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The Behavior of Acid Halides Toward Lewis Acids and Lewis Bases.

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The Behavior of Acid Halides Toward Lewis Acids and Lewis Bases
By Ekkehard Lindnerr*J
Reactions of some typical acid halides of carbonic and trithiocarbonic acids and oforthophosphoric and sulfuric acids with Lewis acids and Lewis bases are compared. Acylium,
perfluoroacylium, thioacylium, and even sulfonylium ions are obtainable with Lewis
acids. It is possible by conductivity measurements and by electronic and above all IR
spectroscopic investigations to determine whether the 1:1 adducts of acid halides and
Lewis compounds are acylium or sulfonylium salts or donor-acceptor complexes. In the
reaction with Lewis bases, the halogen atom in the acid halide is replaced by the electron
donor, generally with formation of nonpolar molecular compounds or complexes.
1. Introduction
This article presents a comparative report on the
reactions of some typical acid halides that are formally
derived from carbonic and trithiocarbonic acids and
from orthophosphoric and sulfuric acids (RCOX,
RCSX, OPX3, RzPOX, and RS02X; R = organic or
inorganic residue; X = halogen or acid residue) with
Lewis acids and Lewis bases.
Particularly significant results were obtained from
studies on the dependence of the C-0, C-S, P-0, or
S - 0 bond o n the acceptor or donor strength of the
Lewis acid or base and on the electronegativity of the
organic or inorganic residue bonded to the carbon,
phosphorus, or sulfur. The ability of Lewis acids such
as BF3, PF5, AsFs, or SbF5, whose central atoms have
no free electron pairs, to accept the halogen atom of
an acid halide depends on their acceptor strength. The
coordination number of the Lewis acid rises to its
maximum value, the Lewis acid being converted into
an anion, while the acid halide forms an “electrondeficient” cationic system such as
The originally nonbonding electrons on the oxygen or
on the sulfur make a considerable contribution to the
resulting positive charge on the elements carbon,
phosphorus, or sulfur, leading to additional x components in the C-0, C-S, P-0, and S - 0 bonds.
The residue R also has an important influence on
these bonds because of its inductive effect.
If, on the other hand, Lewis bases are allowed to act
on acid halides, the halogen may also be split off as an
anion. In this case, however, it is replaced by the
electron donor, generally with formation of non-polar
compounds. In contrast with the reactions with Lewis
acids, the x components of the G O , C-S, P - 0 , and
S - 0 bonds are now decreased; the bond strength
again depends on the donor strength of the Lewis base
and on the electronegativity of the residue R.
[*] Priv.-Doz. Dr. E. Lindner
Instltut fur Anorgankche Chemie der Universitiii
8520 Erlangen, Fahrstrasse 17 (Germany)
The phenomena just described can be followed particularly readily by methods based on vibration spectroscopy. I n the IR spectra of the cationic systems formed
from Lewis acids and acid halides, the frequencies of
the element-oxygen or
element-sulfur stretching
vibrations increase considerably, pointing to correspondingly high force constants. In the reaction
products of Lewis bases with acid halides, these
stretching frequencies often show an extremely
pronounced decrease; the force constants have therefore become extremely small.
2. Acyl Halides and Perfluorinated Acyl Halides
2.1. Reactions with Lewis Acids
Though acylium salts have been known for a long
time[rl, it was Seelr21 that first recognized them as
“carboxonium” compounds and detected them. They
are obtained e.g. by reaction of CH3COF and BF3 or
CH3COCI and SbClS below 0 “C.
Their salt-like character has been confirmed by conductivity measurements in liquid SO2
Above the boiling point of CH3COF (20.8 “C), the salt
is largely dissociated into the two starting components.
Stable acylium salts were first reported by Olah et
al. 133, who described them as “oxocarbonium” derivatives because of the positive charge on the carbonyl
carbon atom. Two methods have become particularly
widely used for the preparation of acylium saltsr2. 31;
these are the reaction of acyl fluorides with Lewis acids
such as BF3 or EIF5 (El -= P, As, Sb) and the reaction
of acyl chlorides or bromides with the anhydrous silver
complexes Ag[BF4] or Ag [EIFs] (“silver salt method”)
[l] F. Fairbyorher, J. chem. S O C . (London) 1937, 503; R.J.Gillespie, ibid. 1950, 2997; H . Burton and P.F.G.PraiN, ibid.1950, 2034.
121 F.Seel, Z . anorg. allg.Chem.250, 331 (1943); 252, 24 (1944).
131 G. A . Olah, S. J . Kuhn W. S.To/gyesi, and E. B. Baker, J.
Amer. chem. SOC.8 4 , 2733 (1962).
Angew. Chem. internat. Edit. 1 Vol. 9 (1970)
1 No. 2
in strongly polar solvents such as nitromethane or
liquid SO2:
+ [RCO] [EIFnl
+ Ag[EIFn]
+ [RCO] [EIFnl+ AgX
El = B, n = 4; El = P, As, Sb, n = 6; X = CI, Br
The second method is often more favorable for
preparative reasons. Olah et al. [31 isolated the thermally surprisingly stable, but extremely hygroscopic,
acetylium, propionylium, and benzoylium cations as
the salts [RCO][ElF,]. The arsenic and antimony
compounds, which are among the most stable of
these, are almost completely in the form of the
acylium salts ( I ) even at room temperature, whereas
the PF6- derivative contains considerable quantities
of a polarized donor-acceptor complex (2) under the
same conditions.
The question whether a 1:l adduct of the type
RCOF.EIFn-l is in the form of the acylium salt ( I )
or of a donor-acceptor complex (2) can be answered
by conductivity measurements or by IR spectroscopic
investigations [3,41. Whereas the CO stretching absorption of ( I ) appears above 2290 cm-1, i.e. in the CO
triple bond region, the corresponding band for the
compounds (2) lies below 1620 cm-1; in other words,
it has been shifted toward longer wavelengths relative
to that of the free acid fluoride.
By X-ray studies on [CH3CO][SbF6], Boertsl was
able to show the existence, in the solid state, of isolated
linear [CH3CO]+ cations (symmetry C3"), in which
the C-H, C-C, and C - 0 distances are considerably
shorter (d C-C = 1.378 A, d C - 0 = 1.116 A) than in
aldehydes and ketones, owing to the positive charge
on the carbonyl C atom. MO calculations gave the
following charge distributions: -0.11 for the methyl
carbon atom, 1.18 for the carbonyl carbon atom, -0.35
for the oxygen, and 0.09 for each hydrogen atomt51.
Acylium salts can also be detected chemically [31. They
react with benzene by a Friedel-Crafts mechanism to
form the ketones. Only the salt form (1) has an
acylating action, whereas (2) has not.
Electronegative ligands, such as perfluoroalkyl groups,
have a considerable influence on the C - 0 bond. 1:l
complexes of perfluoroacyl fluoride with phosphorus,
arsenic, or antimony pentafluoride can be prepared by
the "silver salt method" 131 if liquid SO2 is used as the
+ Ag[EIF6]
CF3, CzF5; El
P, AS, Sb
[4] B. P . Susz and J.-J. Wuhrmann, Helv. chim. Acta 40, 722
(1957); D.Cook, Canad. J . Chem. 37, 48 (1959); 40,480(1962).
[5] F. P . Boer, J. Amer. chem. SOC.88, 1572 (1966).
[6] E. Lindner and H . Kranz, Z . Naturforsch. 206, 1305 (1965).
Angew. Chem. internat. Edit.
Vol. 9 (1970)
/ NO. 2
The advantage of acid bromides is obvious, since
AgBr has a lower solubility product than AgCl. It has
been found possible to prepare trifluoroacetylium
hexafluoroantimonate(v) below - 25 OCl6J. The conductivity diagram L7J (from measurements in liquid
SO2) shows a marked change of direction at the
boiling point of CF3COF (-57°C). Below this temperature the specific conductivity increases very
rapidly; CF3COF.SbFs is therefore best formulated
as a 1:l electrolyte [CF3CO][SbF6] at these temperatures (equivalent conductivity at -60 "C: I\,
Low-temperature I R studies revealed a band of
medium intensity at 2371 cm-1, which practically
disappears at room temperature, and which is characteristic of a C E O stretching vibration. From the
occurrence of two other absorptions at 1780 and
1631 cm-1 (i.e. shifted to longer wavelengths in relation
to CF3COF) in the I R spectrum of CF3COF.SbF5,
which can be assigned to a keto (>C=O) stretching
vibration, it is concluded that a considerable amount
of the compound exists as a polarized donor-acceptor
complex above -57 "C r6,71. Whereas CF3COF.AsF5
decomposes into CF3COF and AsF5 above -57"C,
and CF3COF.PF5 cannot be isolated at all, the thermally more stable CF3COF.SbFs reacts with benzene
at 6 "C to form CF3COC6H5, which could be detected
in small quantities when precipitated as the 2,4-dinitrophenyl hydrazone.
The homologous 1:1 adduct C2FSCOFSbFS exhibits
no conductivity (in nitromethane) at room temperature
and, as its I R spectrum shows, it is only partly in the
form of the 1:l electrolyte even below -30°C. The
action of C6H6 on C2FSCOF-SbFs does not yield the
ketone 171.
2.2. Reactions with Lewis Bases
The behavior of aliphatic and aromatic acyl halides
toward organometallic Lewis bases, particularly
carbonylmetalates, was studied in detail several years
ago 18-11].
e.g. R
CH3, ClHx, C6H5. etc.; M
Co; ii = 4, etc.
Mn, Re; n
This reaction yields extremely reactive acylcarbonylmetal compounds, some of which are of industrial
interest [lo]. Derivatives are also known in which
CO groups are replaced by other ligands, as in
C H ~ C O C O ( C O ) ~ P Rand
~ [ ~X
~ ]- C ~ H ~ F ~ ( C O ) ~ C O C H ~
1133, with the result that the stability is generally greatly
[7] E . Lindner and H. Kronz, Chem. Ber. 99, 3800 (1966).
[8] R . D . Closson, J . Kozikowski, and T . H . Coffeld, J. org.
Chemistry 22, 598 (1957).
[9] W.Hieber, G . Broun, and W .Beck, Chem.Ber.93, 901 (1960).
[lo] R . F. Heck and D . S . Breslow, Chem. and Ind. 1960, 467.
[ I l l W. Beck, W.Hieber,and H.Teng/er,Chem.Ber.94,862(1961).
[12] R . F. Heck and D . S . Breslow, J. Amer. chem. SOC.82, 4438
(1960); R . F. Heck, ibid. 85, 651, 657 (1963).
[13] J . P. Bibler and A . Wojcicki, Inorg. Chem. 5 , 889 (1966).
increasedr141. It is interesting to note that only the
truns complexes are obtained in the case of RCOCo(C0)3PR3; the acyl residue and the phosphine
ligand are arranged axially around the Co atom, and
the three CO groups equatorially (pseudo-C3,) [151.
On the other hand both cis and tram forms of the
pseudo-octahedral Mn complexes of the type
RCOMn(C0)4PR3 [16-181 have been isolated [17-191.
A characteristic of all acylmetal compounds is that
owing to the strong donor properties of the metal, the
keto (>C=O) stretching bands, in the sense of the
polar limiting form (b) are strongly shifted toward
longer wavelengths, pointing to a weakened C=O
bond 1111. Carbonylacylmetal compounds eliminate CO
when heated in the absence of air [8,9,111. This reaction
has been followed for acetylpentacarbonylmanganese
with the aid of the isotopes 14C(201 and 13C 1211:
The CO removed was originally terminal, i.e. it did
not come from the acetyl group. Conversely, no
activity of the acetyl group can be detected in a reaction of
e0 on CH3Mn(C0)5 under pressure[221:
+ 60
+ CH3COMn(C0)460
Similar experiments with organocobalt derivatives led
to the same results [Is]. When partly halogenated acyl
chlorides, such as CHzXCOCl (X = F, CI), are used,
rotational isomers of the type CH2XCOMn(C0)5 are
observed in the reaction with [Mn(C0)5]-, as is
shown by NMR and IR datac23J.
Perfluorinated acyl halides 124-271 or anhydrides of
carboxylic acids [11,28,291 react with organometallic
Lewis bases to give the carbonylperfluoroacylmetal
The stability of the metal complexes is considerably
increased by the introduction of perfluoroalkyl groups,
which relieve the metals of their negative charge. This
is particularly noticeable in the case of cobalt; whereas
CH3COCo(C0)4 [10,141 decomposes rapidly above
-30 OC, CF3COCo(C0)4 [281 is stable up to 55 "C.
Carbonylperfluoroacylmetal complexes can also be
decarbonylated [26-291; the products are the carbonylperfluoroalkylmetal complexes, which are thermally
stable and resistant to atmospheric oxygen. The higher
homologs C2F5COCo(C0)4 and C ~ F ~ C O C O ( C O ) ~
characteristically eliminate CO at much lower temperatures ( > 3 0 and >O "C respectively) 1291. The
carbonyl group between the metal and the perfluoroalkyl residue is thus evidently increasingly eliminated
as the number of F atoms increases.
As expected, the electron-attracting perfluoroalkyl
residues shift the keto (>C=O) stretching bands to
higher frequencies in relation to those of the unfluorinated acylmetal compounds (cf. Table 1).
The behavior of acyl halides toward organophosphorus
and organoarsenic compounds has also been studied.
Zssleib and Priebe 1301 were the first to obtain CH3COP(C6H5)2 [from CH3COCl and LiP(C&5)2], which can
be readily oxidized with oxygen to CH3COPO(C6H5)2.
Since Lewis basicity decreases in the order amines
(though these occupy a special place because of the
absence of energetically favorable d orbitals in nitrogen), phosphines, arsines, and stibines, it is particularly
interesting to compare the properties of perfluoroacyldiphenylphosphines and perfluoroacyldiphenylarsines 1311.
[14] R . F. Heck, J. Amer. chem. SOC.85,2220 (1963).
[15] Z . Nagy-Magos, G. Bor, and L. Markd, J. organometallic
Chem. 14, 205 (1968).
[I61 R . J . Mawby, F. Basolo, and R . G. Pearson, J. Amer. chem.
SOC.86, 3994 (1964).
[I71 R . J . Mawby, F. Basolo, and R . G. Pearson, J. Amer. chem.
SOC.86, 5043 (1964).
[I81 W . D . Bannister, M . Green, and R . N . Haszeldine, Chem.
Commun. 1965, 54.
[191 C. S . Kraihanzel and P . K . Maples, J. Amer. chem. SOC.87,
5261 (1965).
[20] F. Calderazzo and F. A . Cotton, Inorg. Chem. 1 , 30 (1962).
[21] K . Noack and F. Calderazzo, J. organometallic Chem. 10,
101 (1967).
[221 H . Werner, Angew.Chem. 80, 1017 (1968); Angew. Chem.
internat. Edit. 7,930 (1968).
[23] F. Calderazzo, K . Noack, and U .Schaerer, J.organometailic
Chem. 6 , 265 (1966).
1241 H.D.Kaesz, R . B. King, and F.G. A.Stone, Z. Naturforsch.
ISb, 763 (1960).
[25] W. R . McClellan, J. Amer. chem. SOC.83, 1598 (1961).
1261 R . B. King, J. Amer. chem. SOC.85, 1922 (1963).
[27] R . B. King and M . B . Bisnette, J. organometallic Chem. 2, 15
+ NaX
R = CF3. C2F5, CjF7 rtc.; X = CI, OCOR; M = transition metal
+ MEl(c6H~)z--+
CF3, C2F5; X
Na, K; El
+ MX
P, As
The colorless to orange-red liquids are extremely
sensitive to air and moisture.
Contrary to expectations, oxidation of CF3COP(C6H5)2
with molecular oxygen leads, not to CF3COPO(C6H5)2,
but by a complicated path that depends on the solvent
(toluene or hexane) to 1-diphenylphosphoryl-2,2,2-trifluoroethyl diphenylphosphinate [31al and C02. The
[28] W. Hieber, W. Beck, and E. Lindner, Z . Naturforsch. 166,
229 (1961).
I291 W . Hieber and E . Lindner, Chem. Ber. 95,2042 (1962).
[30] K . Issleib and E. Priebe, Chem. Ber. 92, 3183 (1959).
[31] E. Lindner and H . Kranz, Z . Naturforsch. 226, 675 (1967);
Chem. Ber. 101, 3438 (1968).
[3lal E. Lindner, H.-D. Ebert, and P. Junkes, Chem. Ber., in press.
Angew. Chem. internat. Edit.
Vol. 9 (1970) No. 2
structure was demonstrated by alkaline decomposition
to diphenylphosphinic acid and trifluoroethanol, and
by mass spectroscopic (molecular mass line: SOO),
N M R (two 31P signals), and I R studies. The proton
on the asymmetric C atom gives the splitting scheme
of first order coupling in the high-resolution 1H-NMR
spectrum, i.e. a doublet of quartets of doublets
(coupling constants: 2 J ~ p= 12.5 Hz; 3JHp* = 4.7 Hz;
~ J H=F7.8 Hz). The I R spectrum is characterized in
particular by V(C-Haliphat.) (2924 cm-1) and vas
(P-O-Caliphat,) (1092 cm-1) apart from the intense
P - 0 and CF3 stretching vibrations. The peculiar
oxidation behavior of C F ~ C O P ( C ~ H is
S )due
~ to the
electron-attracting CF3 group and the lone pair of
electrons on the phosphorus.
Whereas CH3COP(C6H& and the perfluoroacyldiphenylarsines decompose when heated in the absence
of air, perfluoroacyldiphenylphosphines, like the acylcarbonylmetal and carbonylperfluoroacylmetal compounds, quantitatively eliminate CO to form perfluoroalkyldiphenylphosphines. The removal of CO
is evidently facilitated when the keto group is directly
flanked by a strong electron donor and an electronegative alkyl residue. C F ~ P ( C ~ H S
) ~ also be
prepared from (C&&PP(C~HS)~and CF3I [321.
An insight into the molecular structure and the
difference in the chemical behavior of perfluoroacylphosphines and perfluoroacylarsines is provided above
all by the I R spectra. The phosphines are characterized
by the very low frequency (1702 cm-1) of the keto
(>C==O) stretching vibrations, whereas the corresponding band for the homologous arsines, in agreement with their weaker donor properties, is situated
a t a wave number about 55 cm-1 higherr311. This is
probably due to stronger participation of the limiting
form (6) in the phosphorus compounds than in the
arsenic compounds.
The other I R data support this view, the CF3 and
P-Cacyl stretching vibrations being particularly
Moreover, the behavior of CF3COSn(CH3)3, which
was recently isolated in the reaction of LiSn(CH3)3
with CF3COC1, is quite comparable with that of
CF~COAS(C~H&.Owing to tin’s lack of donor
properties, the colorless liquid does not eliminate CO
when heated, and is even stable to dry oxygen. In
agreement with this, the keto (>C=O) stretching
vibration occurs at a very short wavelength [32a3.
[32] M . A. A . Beg and H. C . Clark, Canad. J. Chem. 40, 283
(1962); 40, 393 (1962).
[32a] E.Lindner and U.Kunze, J. organometallic Chem. 21, P 19
Angew. Chem. internat. Edit.
Vol. 9 (1970)1 No. 2
Table 1 shows a comparison of the C - 0 stretching
frequencies and force constants of (trifluoro)acetyl
fluoride and some derivatives.
Table I . C - - 0 stretching vibrations and estimated force
constants of (trifluoro)acetyl Ruorlde and some derivatives.
(cm- 1
3. Thioacyl Halides
A particularly interesting aspect in systematic studies
is the behavior of thioacyl halides toward Lewis acids
and Lewis bases. The only thioacyl halide that has
been verified in every respect so far is thiobenzoyl
chloride. Staudinger and Siegwart [35J obtained this
compound as early as 1920 from dithiobenzoic acid
and thionyl chloride. The preparation of CF3CSCl[361
was also described for the first time in a patent a few
years ago.
3.1. Reactions with Lewis Acids
As was seen in Section 2.1, the “silver salt method” is
particularly suitable for the preparation of acylium
salts. Stoichiometric quantities of C6H~CSCI and
Ag[SbF6] react in liquid SO2 at -40°C to give an
extremely hygroscopic, light brown complex, which is
found even at room temperature to be the surprisingly
stable thiobenzoylium hexafluoroantimonate(v) 1371:
The ionic structure is shown by conductivity measurements (equivalent conductivity a t -50°C: A, ==
80.9 Lk-1 cm2mole-l), by IR studies [v(C-S) = 1332
cm-1; v(SbF6-) = 673 cm-1 (Tlu)], and by reaction
with benzene:
1331 L . J . Bellarny and R . L. Williams, J. chem. S O C . (London)
1957, 4294.
[34] E . J . Bourne, S . H . Henry, C . E. M . Tatlow, and J . C. Tatlow,
J. chem. S O C . (London) 1952,4014.
[35] H . Staudingerand J . Siegwart, Helv.chim.Acta 3,824 (1920).
[ 3 6 ] W. J . Middleton, US-Pat. 3113936 (1963), DuPont; Chem.
Abstr. 60, 4012 (1964).
[37] E. Lindner and H.-G. Karmann, Angew. Chem. 80,561 (1968);
Angew. Chem. internat. Edit. 7, 548 (1968).
Thiobenzophenone is formed in a yield of about 40 %.
This was the first reaction to yield a thioacylium ion,
and it was shown that thioacyl halides also react by the
Friedel-Crafts mechanism. Mayer and Scheithauer [38J
had previously obtained thiobenzophenone from thiobenzoyl chloride, benzene, and anhydrous AI2Cl6, and
these authors also explained the reaction by a FriedelCrafts mechanism.
According to the I R spectrum, the [C6H5CS]+ cation
can be essentially described by the limiting formulas
( l a ) -(I c).
understandable if one considers that sulfur is more
readily polarizable than oxygen because of its greater
atomic radius, and the nucleophilic strength is further
increased by the negative charge carried by the sulfur
in the polar limiting form. Intramolecular elimination
of CO seems to be ruled out for steric reasons, so that
only polymeric products are to be expected. One does
in fact obtain a compound consisting of --.-Mn(C0)4C(R)-S-Mn(CO)4-C(R)-S-...
units. The compound
may be regarded either as a thioketone complex (3a)
or as a carbene complex (3b) [401; no distinction can
be made on the basis of the I R spectrum.
3.2. Reactions with Lewis Bases
The reactions of thioacyl halides with organometallic
Lewis bases are much more complicated than those of
acyl halides, and are by no means uniform. Thus
C~HSCSCIand Na[Mn(CO)s] react quantitatively at
-78 “C in T H F to give c & c S M n ( C o ) ~ 1391; however,
this product eliminates one CO per Mn atom above
-70 “C. Incontrastwiththereactionsofthe[Mn(CO)s]anion with acyl halides 1111, carboxylic acid anhydrides [28,291, or even sulfonyl halides, in which the
reaction product still contains an intact Mn(CO)s
residue, no such product can be obtained in this case.
The product isolated is instead a non-polar, chromatographically uniform brown compound that is inert to
atmospheric oxygen, and which has the formula
[C6H5CSMn(C0)4], (n is 3 or 4, depending on whether
the reaction mixture is warmed rapidly or slowly to
room temperature). It must be assumed from the
solubility behavior of the “tetrameric” Mn compound
that it is polymeric in the solid state, and breaks down
into smaller fragments only on dissolution. It is
interesting to note that the molecular weight of the
“tetramer” falls to that of the “trimer” within a few
The coordination vacancy created on the manganese
by the loss of CO is filled by the sulfur, as is shown
in particular by IR data. The long wavelength of the
v(>C=O) band for the acylpentacarbonylmanganese
compounds (cf. Section 2.2) points to appreciable
participation of the polar limiting form (2). Formal
It is interesting to note that there is no absorption
between 700 and 1500 cm-1 that can be assigned t o a
C-S stretching vibration. However, a new band of
medium to low intensity, which suggests a C-S
vibration, appears at 630 cm-1 (cf. Table 2). In agreement with the proposed structures (3a) and (3b), the
spectrum also shows four C - 0 absorptions having
very high wave numbers (cis position of the CO
groups), i.e. 2100,2020,2011, and 1955 cm-1 for n = 3
and 2090, 2032, 2008, and 1956 cm-1 for rr = 4. Only
X-ray structural analysis can show whether structuie
(3a) or (36) is present, since the Mn-C distance
should be greater than 2 A in a carbene complex f411.
The reaction of C6H5CSCl with the Lewis base
[Re(C0)5]- is fundamentally different from the reaction with [Mn(CO)s]-. All the results with [Re(C0)5]point to the formation of a dithiolate complex 1421.
Table 2. C-S stretching vibrations and estimated
force constants of C6H,CSCI and some derivatives.
replacement of the oxygen in the acyl residues by
sulfur should lead to a decrease in the C-S bond order.
Finally, the nucleophilic strength of the sulfur is
[38] R . Mayer and St. Scizeitlzauer, J.prakt.Chem. 21, 214 (1963).
[39] E. Lindner, Part of Habilitationsschrift, Universitat Erlangen-Niirnberg 1967; E. Lindner, H . Weber, and H.-G. Karmnnn,
J . organometallic Chem. 17, 303 (1969).
[40] Cf. e . g . E . 0. Fischer and A . Maasbol, Angew. Chem. 76,645
(1964); Angew. Chem. internat. Edit. 3, 580 (1964).
[41] 0. S . Mills and A . D . Redhouse, Angew. Chem. 77, 1142
(1965); Angew. Chem. internat. Edit. 4, 1082 (1965).
1421 E. Lindner and H . Weber, unpublished.
Angew. Chem. internat. Edit.
Vol. 9 (1970) 1 No. 2
4. Phosphoryl Halides and Diorganophosphinyl
4.1. Reactions with Lewis Acids
On reaction of phosphoryl halides (OPX3; X = C1,
Br) with Ag[SbF6][391 in a polar solvent such as
acetonitrile, though AgX separates out of the solution,
no salt [OPX2]+ [SbF6]- is formed. Ag[SbF6] evidently
acts as a fluorinating agent in this case; OPF3 (v(P-0)
= 1415 cm-1) is formed quantitatively, irrespective of
the stoichiometric ratio of the starting compounds
+ 3 Ag[SbF6]
20 o
3 AgX
+ 3 SbFS
The instability of phosphorylium ions is so severe that
even organosubstituted derivatives [R2PO]+ cannot be
stabilized. On reaction of bis(dimethy1amino)phosphinyl chlorides or diphenylphosphinyl chloride on
Ag[SbF6] in liquid SO2 or acetonitrile in accordance
R2P(F)O. . .SbFs could be detectedC42aJ.
4.2. Reactions with Lewis Bases
Hieber and Duchatsch[431 have shown that the phosphoryl halides OPC13 and OPBr3 halogenate organometallic Lewis bases.Reaction with[Co(C0)3P(C6H~)3]leads primarily to the halogen derivatives, which are
mediate. This was found from concentration-dependent
molecular weight determinations,conductivitymeasurements, IR studies, and its hydrolysis properties to be
an ionic dihalogenophosphoryltriphenylphosphonium
halide containing a P-P bond 1451:
The observed chalcogen transfer occurs only in the
presence of small quantities of moisture:
The salts may be regarded as substitution compounds
of phosphoryl halides. Some time ago, Cutrnann [461
described a crystalline adduct having the composition
OPC13.2CsH5N, which dissociates in OPC13 into the
ions [C5H5NP(C12)0]+ and C1-. Baaz and Gutnzann 147,481 later showed that tertiary aliphatic amines,
as Lewis bases, also have a substituting action in
OPC13 solution:
+ OPC13 + FeC13 -2
As(C6H5)3, which is very readily soluble in OPCl3,
also reacts with the solvent [451. However, the colorless
[ ( C ~ H ~ ) ~ A S P ( C ~slowly
~ oPc13 above room
temperature, owing to the weaker donor properties of
The number of IR absorptions in the spectra of the
compounds [(C~HS)~PP(X~)O]X
points to low symmetry [point group c,, with P(C6H5)3 as a point mass].
This leads to a pseudotetrahedral arrangement of the
four ligands [2 X-, P(C&)3, and 01 about the central
phosphorus atom (Fig. 1).
Fig. 1. Structural model of the cations [ ( C ~ H S ) ~ P P ( X Z ) ~ ] + .
thermally unstable and immediately change into the
dicarbonyl compounds XCo(C0)2[P(C6H5)3]2.
Toward neutral Lewis bases, such as triphenylphosphine or triphenylarsine, phosphoryl halides and thiophosphoryl halides act as excellent chalcogen transfer
agents 1441.
+ E I ( C ~ H S )+
El’ = 0, S; X
CI, Br; El
+ EI’EI(C6H5)3
As can be seen from Table 3, the P-0 and P-C1
stretching vibrations in the phosphonium salts occur
at higher frequencies than in the parent compounds
Table 3. P-0 and P-Cl stretching vibrations of phosphoryl halides
and their substitution uroducts [(C~HS)~PP(XZ)OIX.
1290 (A,)
P, As
1261 (A,)
This reaction can be applied to any monodentate or
polydentate organophosphine or organoarsine.
1320 (A’)
For phosphoryl halides (X = C1, Br) in particular, the
transfer of chalcogen to phosphines takes place via an
extremely hygroscopic, thermally stable, isolable inter-
[45] E. Lindner and H . Schfess, Chem. Ber. 99, 3331 (1966).
[42a] E . Lindner and K . - M . Matejcek, 2. anorg. allg. Chem., in
[43] W.Hieber and H . Duchatsch, Chem. Ber.98, 2530 (1965).
[44] E . Lindner, unpublished.
[46] V . Gutmann, Mh. Chem. 85, 1077 (1954).
[47] M . Baaz and V , Gutmann, Mh. Chem. 90,216 (1959); 90,144
1481 M . Bnaz, V. Gutmann, and L. Hiibner, Mh. Chem. 92, 107
Angew. Chem. internat. Edit.
1 VoI. 9
No. 2
1305 (A‘)
OPX3 corresponding to greater double-bond components in the P - 0 and P-CI bonds, owing to the
positive charge on the phosphorus of the PR3 group.
Dihalogenophosphoryltriphenylphosphonium halides
can be converted specifically into 1:1 triphenylphosphine oxide-metal halide complexes containing a
metal-oxygen-phosphorus bridge by reaction with
metal halides. This reaction, which is of preparative
interest, proceeds particularly well when the metal
halides are soluble in an inert solvent (ether).
Many new 1:l complexes have been obtained in this
way [MCln = TIC14 (complex: yellow), ZrC14 (pale
yellow), VCl3 (pink), FeC13 (light yellow), and CoC12
(deep blue)]. The AlC13- [501 and NbCls adducts [511
prepared by these reactions are already known.
The triorganophosphine oxide-metal halide complexes described many years ago by Pickard and
Kenyon [521 have recently been subjected by numerous
authors [51,53-561 t o IR- C571 and UV spectroscopic
studies 1581.
While Tyree et al. [591, Cotton et al. [601, and Merijanian
and Zingaro [611 also extended these studies to triorganoarsine oxides, Tyree et al. 158,621, Guns et al. [63J,
Kohl, Lewis, and Whyman[641, and Hart and Newbery [651 also reported on triphenylphosphine oxidemetal oxide halide complexes. The compounds can be
prepared in general by direct action of triphenylphosphine oxide on the metal halide, and contain more
O P ( C ~ H Sthan
) ~ they should for a ratio of 1:l. On the
other hand, the formation of the few hitherto known
1:l triarylphosphine oxide-metal halide adducts [50,51
661 was fortuitous.
The intense v,(P-0-M)
bands [491 lie between 1160
and 950 cm-1 depending on the acceptor strength of
the metal, and are shifted (considerably in some cases)
toward longer wavelengths in relation to that of
OP(C6H5)3 (1191 cm-1). Since each metal atom is
bonded to only one phosphine oxide residue, the
( p j d ) , back-bonding component of the 0 - P bond is
greatly decreased. This can be illustrated by two
titanium compounds; 2 (C6H5)3P0.TiC14[53]:v(P-0) =
1130 cm-1; (C6H5)3POTiC14f491: v(P-0) = 1060 cm-1.
The v,(P-O-M) stretching vibrations are more difficult to assign; this has been achieved with certainty for
(C6H&POAIC13 [49,671 and (C6H5)3POCOC12 f491 (cf.
Table 4). The simplified calculation of the force
constants for the P-0 and A1-0 bonds on the basis of
the three-particle model gives fpo = 7.5 mdyn/A and
falo = 1.7 mdyn/A; the two P-0 and A1-0 oscillators are therefore strongly coupled with each other.
By application of the Siebert approximation
orders of 1.7 and 0.3 are estimated for the P - 0 and
A1-0 bonds respectively. The relatively small force
constant of the weak Al-0 bond, which is characteristic of this addition complex, can be confirmed by experimental observations 1491. With the stronger acceptors TiCl4, ZrC4, and particularly NbC15,
vas(P-0-M) stretching vibrations absorb at unusually
low frequencies, corresponding to a stronger metaloxygen bond. Finally, with MoCl5 or WCl6, the
oxygen is actually displaced from the phosphorus to
the metal [49,62,69,701.
Table 4. Some P-0-M
stretching vibrations of 1:ltriphenylphosphine oxide-metal halide compiexes.
(491 E. Lindner, R . Lehner, and H. Scheer, Chem. Ber. 100, 1331
[50] M . J. Frazer, W . Gerrard, and R . Twaits, J. inorg. nuclear
Chem. 25, 637 (1963).
1511 D. Brown, J . F. Easey, and J . G. H . du Preez, J. chem. S O C .
(London) A 1966,258.
1521 R . H . Pickard and J . Kenyon, J. chem. SOC. (London) 1906,
1531 J . C. Sheldon and S . Y.Tyree, J. Amer. chem. SOC.80, 4775
[54] D . M . L . Goodgame and F. A . Cotton, J. chem. SOC.(London)
1961, 3735.
5. Sulfonyl Halides and Perfluorinated Sulfonyl
1551 K . Issleib and H . Reinhold, Z . anorg. allg. Chem. 314, 113
[56] H . Glees and F. Huber, 2. anorg. allg. Chem. 352,200 (1967).
5.1. Reactions with Lewis Acids
[57] F. A . Cotton, R. D . Barnes, and E. Bannister, J. chem. SOC.
(London) 1960, 2199.
1581 S.M.Horner and S.Y.Tyree j r . , Inorg. Chem. 2, 568 (1963).
1591 D . J . PhiZlips and S. Y.Tyreejr., J. Amer. chem. Soc. 83,1806
1601 D . M . L . Goodgame, M . Goodgame, and F. A . Cotton, Inorg.
Chem. I , 239 (1962); G . A . Rodley, D . M . L . Goodgame, and
F. A . Cotton, J. chem. SOC.(London) 1965, 1499.
By reaction of p-CH3C6H4S02Br with Ag[CI04], KZages et al. 1711 were able to show that p-toluenesulfonylium ions probably exist in liquid SO2 below -60 "C.
If instead of Ag[C104] one uses Ag[SbF6], which has
repeatedly given successful results in the past, only
1611 A . Meroanian and R . A.Zingaro, Inorg. Chem. 5,187 (1966).
[62] S . M.Horner and S.Y.Tyreejr., Inorg. Chem. I , 122 (1962).
[63] P. Cans and B. C.Smith, J. chem. SOC.(London) 1964, 4172.
[64] F. J . Kohl, J . Lewis, and R. Whyman, J. chem. SOC. (London)
A 1966, 630.
1651 F. A . Hurt and J . E . Newbery, J. inorg. nuclear Chem. 28,
1334 (1966).
1661 M . E . Peach and T . C. Wuddington, J. chem. SOC.(London)
1962, 3450.
1671 E. W . Wartenberg and J . Goubeau, 2. anorg. allg. Chem. 329,
269 (1964).
[68] H . Siebert, 2. anorg. allg. Chem. 273, 170 (1953).
1691 C. G . Barraclough, J. Lewis, and R . S. Nyholm, J. chem. S O C .
(London) 1959, 3552.
1701 F.A.Cotton and R . M . Wing, Inorg. Chem. 4 , 867 (1965).
1711 F. Klages and K . Hoheisel, Chem. Ber. 96, 2057 (1963);
F. Kluges and F. E. Mafecki, Liebigs Ann. Chem. 691, 15 (1966).
Angew. Chem. internat. Edit.
Vot. 9 (1970) / No. 2
halogen exchange is observed at room temperature 1721.
CF3S02Cl and FS02CI d o not react with Ag[SbF6] 1731.
Organosulfonylium ions cannot be stabilized even by
strong Lewis acids unless the sulfur can transfer its
positive charge to the organic residue, with participation of quinonoid limiting forms in the case of aromatic
systems [721.
Thus the p-dimethylaminobenzenesulfonylium ions
(4), which (for El = Sb) are stable up to room tem-
and BF3. Table 5 shows a comparison of the properties
of some p-dimethylaminobenzenesulfonyl and p-dirnethylaminobenzenesulfonylium compounds.
5.2. Reactions with Lewis Bases
Organometallic sulfonyl or “S-sulfinato” complexes
have been known only since 1964c741. They can be
prepared by two basic methods:
a) by the action of sulfonyl halides or sulfonic acid
anhydrides on organometallic Lewis bases, and
b) by insertion of SO2 between the metal and the
organic residue (“SO2 insertion”).
perature, but are very hygroscopic, can be prepared
in accordance with
from p-(CH3)2NC6H4S02Cl [containing the (CH3)zN
residue, which acts as a strong electron donor] and the
complexes Ag[ElF6] in liquid SO;?.
The participation of the quinonoid limiting form (4b)
deepens the color of the complexes. This effect is
particularly noticeable in p-dimethylaminobenzenesulfonylium hexafluoroantimonate(v), which is readily
soluble in liquid S02, and whose deep orange color
[p-(CH3)2NC6H$302CI is lemon yellow] is a definite
indication of the quinonoid form (46). Further evidence is provided by the electronic spectra. Whereas
p-(CH3)2NC6&S02CI has an intense maximum in the
visible region a t 24 509 cm-1, the band characteristic
of thecation shows a bathochromicshift to 21 413 cm-1.
The ionic structure of the antimony complex is also
shown by conductivity measurements in nitromethane
(cf. Table 5).
Owing to the conjugation effect [limiting form (4bJ1,
the symmetric and asymmetric SO2 vibrations of
[p-(CH3),NC6~so2][sbF6] absorb at higher frequencies than the corresponding vibrations in p(CH3)2NC6&S02F (cf. Table 7). The stronger 0 - S
double bond character [(p+d),] and the intense
absorption band at 662 cm-1 [v(SbF6-) (TI,)] also
point to the ionic structure. The stability of the
[p-(CH3)2NC6fiS02]+ cation decreases with decreasing acceptor strength of the Lewis acids AsF5, PF5,
Table 5. Properties of compounds of the type
~ X[ P - ( C H ~ ) ~ N C ~ H ~ S O Z ] X .
olive green
light green
up to 30 O C
up to -20 “C
up to -25 “C
not isolable
cmz mole-’)
Neither process is generally applicable, but each
complements the other.
Method a): The action of p-CH3C6fiS02Cl on the
Lewis base [Mn(C0)5]- leads not only to the expected
pentacarbonyl - p - toluenesulfonylmanganese
ClMn(CO)s, but also to a series of by-products, some
of which are polymeric[751, and which prevent the
preparation of pure p-CH3C6&S02Mn(C0)5.
formation of CIMn(C0)s is based on the strongly
electron-attracting effect of the p-toluenesulfonyl
residue on the C1 atom; the halogen atom acquires a
positive charge because of the inductive effect, with
the result that the S-Cl bond assumes double bond
character [761. The instability of the [p-CH3C6H4S02]+
cation confirms these views.
If, however, p-CH3C6H4S02Cl is replaced by the anhydride (p-CH3C6H4S02)20, heterolysis occurs in the
presence of the carbonylmetalates of manganese,
iron, and cobalt, which act as Lewis bases.
The extremely unstable [RS02]+ cation immediately
reacts further with the anions mentioned [761, as
+ [Lewis base]-
[Lewis basel-
RS02Lewis base
[Mn(CO)s]-, [~-C5HsFe(C0)21-,and
Like the reaction of perfluorinated carboxylic acid
anhydrides with carbonylmetalates, this reaction
proceeds almost quantitatively [28,29J. The diamagnetic compounds [RSOzLewis base] are thermally very
stable. The method is not applicable to other systems
(e.g. [Re(C0)5]- or [xx-C5H5Mo(C0)3]-).
Unlike p-toluenesulfonic acid anhydride, (CF3S02)20
is totally unsuitable for the introduction of a CF3S02
[74] J . P . Bibler and A . Wojcicki, J.
Amer. chem. SOC.86, 5051
[72] E. Lindner and H. Weber, Chem.
[73] E. Lindner, unpublished.
Ber. 101, 2832 (1968).
Angew. Chem. internat. Edit. / Vol. 9 (1970)
1 No. 2
[75] W. Beck, private communication.
[76] E. Lindner and H . Weber, Z . Naturforsch. 226, 1243 (1967).
group; it oxidizes the carbonylmetalates to the neutral
carbonylmetal compounds in every case 1771. The
CF3S02 derivatives were first isolated in yields of
about 20 % on condensation of equimolar quantities
of CF3S02Cl with [M(CO),](M- Mn, Re),
[x-C5H5Fe(C0)2]-, and [cO(co)3P(c6H~)~]in T H F
solution a t -60 to -80 "C 177,781:
+ [Lewis base]-
+ CF3SOzLewis base
+ CI-
The perfluorinated compounds are thermally much
less stable than the p-toluenesulfonyl derivatives
(Table 6).
Table 6. Melting points and decomposition points of p-toluenesulfonyl and trifluorornethanesulfonyl complexes.
The principal products of the action of sulfonyl halides,
and particularly of CF3S02C1, on carbonylmetalates
are the carbonylchlorometal compounds, the yield of
which largely depends on the electronegativity of the
residue attached to the sulfonyl sulfur atom. It is
significant that FSO2Cl in which the CF3 group has
been replaced by the still more electronegative
fluorine, reacts quantitatively with Na[Mn(CO)s] to
give ClMn(C0)s 1781
FS02C1+ Na[Mn(CO)sJ + CIMn(C0)S
+ NaF+
and is therefore suitable for use as a mild halogenating
agent. It would seem reasonable to prevent this undesirable reaction by the use of the sulfonyl fluorides
instead of the chlorides, but this procedure has not
acquired much importance, owing to the low yields 1791.
The reaction of alkali metal organosulfinates with
halogenated carbonylmetal compounds or halogenocarbonylmetalates has been used for the preparation
of the Cr and W complexes Na[M(C0)5S02C6H5]
(M = Cr, W)[801.
Finally, mention should also be made of the behavior
of CF3S02CI toward carbonylmetal complexes with
aromatic ligands ([nx-C5H5Fe(C0)2]2[791 and [nCsH5NiC012 [sll); the CF3SOz-iron and CF3S02nickel compounds listed in Table 6 are formed in
yields of about 10%.
[77] E . Lindner, H . Weber, and G . Vitzthum, J. organometallic
Chem. 13,431 (1968).
1781 E. Lindner and H. Weber, Angew. Chem. 78, 752 (1966);
Angew. Chem. internat. Edit. 5, 727 (1966).
[79] J . P . Bibler and A . Wajcicki, J. Amer. chem. SOC.88, 4862
[80]F. A . Hartman and A . Wojcicki, Inorg. Chem. 7,1504 (1968).
[81] E.Lindner and G.Vitrthum, Z. anorg. allg. Chern., in press.
Method b): "SO2 insertion" is particularly suitable for
the preparation of carbonylalkanesulfonylmetal,carbonylbenzenesulfonylmetal, carbonyl-cr-toluenesulfonylmetal, and carbonyl-p-toluenesulfonylmetalderivatives, which are formed in high yields and mostly
without by-products 174,7930,821, e.g.
RM(CO),+ SO2
Many sulfinato complexes derived from manganese [821,
rhenium 1801, and iron 1791 have been obtained in this
way: the compounds RS02M(C0)5 (M = Mn, Re) and
~ - C ~ H S F ~ ( C O ) ~ S(R
O ~=
R CH3, C2H5, C6H5,
CH2C6H5, p-CH3C6H4). Depending on the strength
of the metal-carbon bond, liquid SO2 is allowed to act
on the organometallic compound (for example
~ [ ~ ~below
the boiling
point of SO2 or under pressure a t higher temperatures
(about 40 "C) (e.g. C6H5Mn(C0)5 [8ol). It is interesting to note that the SO2 insertion cannot be applied to
perfluorinated carbonylorganometallic compounds 1801.
CF3Mn(CO)s does not take up SO2 even under extreme
conditions; the metal-carbon bond is too strong,
owing to the n-components.
The thermal behavior of the sulfonyl complexes
described is quite different from that of the acyl compounds. N o elimination of SO2 was observed in any
case 1801. The decomposition reactions are uncontrolled, and generally proceed with initial loss of CO.
The positions of the symmetric and asymmetric SO2
stretching vibrations are strongly dependent on the
nature of the residue X bound to the organosulfonyl
group 1761. As can be seen from Table 7, their frequencies are highest for p-CH3C&S02F,
and, for the
same organosulfonyl residue, they decrease with
increasing donor strength of X; for the organometallic
residues X = Mn(C0)5, ~-C=jH5Fe(C0)2, and
Co(CO)3P(C6H5)3 in particular they fall by up to
200 cm-1. This is also found in the trifluoromethanesulfonyl derivatives. The large decrease in the frequencies of the SO2 bands is characteristic of organometallic sulfonyl compounds, and indicates the presence of
strong bonds between the metal and the sulfur:
The electron-attracting CF3 group causes a considerable increase in the frequencies of the SO2 stretching
vibrations. The low frequency vs(SO~) and vas(S02)
vibrations naturally mean that the C - 0 absorptions
must occur at very short wavelengths, as was in fact
found in every case. The spectra of the manganese and
rhenium complexes are characterized by the presence
of five absorptions in the terminal CO group region.
The C4" symmetry is so strongly perturbed because of
the angular RS02 ligands that the B1 vibration, which
is forbidden in the IR, is in fact observed, and the
band of the E vibration is also split.
[82] F. A . Hartman and A . Wojcicki, J. Amer. chem. SOC.88, 844
Angew. Chem. internat. Edit. / Vol. 9 (1970) No. 2
Table 7. Symmetric and asymmetric SO2 stretching frequencies of some
typical sulfonyl halides, sulfonylium compounds, and (perRuoro)organosulfonylmetal complexes.
'Lewis -Base
( 1061
1 1218
f 1128
\ 1132
6. Summary and Outlook
It was shown in Sections 2 to 5 that acylium, perfluoroacylium, thioacylium, and even sulfonylium ions
are obtainable though only under extreme conditions
in some cases. All the described reactions of acyl, perfluoroacyl, thioacyl, or sulfonyl halides and carboxylic
acid or sulfonic acid anhydrides with organometallic,
organophosphorus, or organoarsenic Lewis bases thus
have fundamentally the same course. When a nucleophile dissolved in a polar medium approaches the acid
halide or anhydride, the reaction proceeds uniformly
via a transition state ( 5 ) or (5a) toward the limiting
arrangement, the ions (6) or f6a) (heterolysis).
R' - S - Lewis -Base
0 ; X = CI, Br, OCOR; R
S; X = CI; R = CsH5;
p-CH3C6H4, P - ( C H ~ ) ~ N C ~XH=
~ ;CI, p-OS02C6H4CH3
(perfluoro)organo group;
The surprising stability of the thiobenzoylium ion and
the entirely novel polymeric tetracarbonylthiobenzoylmanganese compounds are of preparative interest.
Thioacyl halides appear to be more reactive than other
acid halides, as is shown by their behavior toward
organometallic Lewis bases.
The intermediate cations (6) and (6a) can now react
with the nucleophile, i.e. the Lewis base, to give the
derivatives (7) and (7a) respectively. The ratedeterming step is the heterolysis.
I ani very grateful to my co-workers Dr. H . Kranz, Dr.
H. Weber, Dr. G . Vitzthum, Dipl.-Chem. H.-G. Karmann, Dip1.-Chem. U. Kunze, Dip1.-Chem. H.-D.
Ebert, and Dip1.-Chem. K.-M. Matejcek, who have
played a vital part in these investigations, and to H .
Schless, R . Lehner, and H. Scheer, who also made
valuable contributions. Sincere thanks are due to Professor Dr.-Ing. H. Behrens for his interest in this work
and for his generous support. I also thank the Verband
der Chemischen Industrie, Fonds der Chemischen Industrie, and the Deutsche Forschungsgemeinschaft for
their financial support.
[83] M . Spoliti, S. M . Chackalackal, and F. E . Stafford, J. Amer.
chem. SOC. 89, 1092 (1967).
Received: January 29. 1969
[A 741 IEI
German version: Angew. Chem. 82, 143 (1970)
Translated by Express Translation Service, London
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