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Dialkylboryl-Substituted Triphenylphosphonium Ylides.

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151 l a was prepared using the method described by J. W. Davis, US-Pat.
3718688 (1973); l b was prepared analogously. The structures were determined by 'H- and "C-NMR spectroscopy as well as by elemental analysis. Although racemic serine can, in principle, also be used L-serine was
used on grounds of cost.
[6] R. Andruszkiewicz, A. Czerwinski, Synthesis 1982, 986.
[7] Experimental procedure using the example of 3b : l b (560 mg, 2.0 mmol)
[5] and an equimolar amount of N,N'-carbonyldiimidazole were dissolved
in 10 mL anhydrous diethyl ether and 2 mL anhydrous tetrahydrofuran
under N2. After addition of 1 mL triethylamine, the mixture was stired for
2-3 min at room temperature, 50 mL cold n-pentane added, and the resulting mixture cooled for 30 min at - 15°C and filtered at this temperature. 3b crystallizes at -90°C; yield: 325 mg (62%); m.p. (in sealed ampule)=60-61 "C (decomp.).
[8] E. Rothstein, J. Chem. Soc. 1949, 1968.
[9] Attempts to prepare the N-salicylidenedehydroalaninemethyl ester indicated that this is considerably more reactive than 3a.
ture can be deduced from the relationship between its
spectra"] and those of other H2R~3(C0)9(p3-X)
complexes[']. 4 is the product of oxidative addition of the NH
moiety of the benzylamino ligand in 3 to the free ruthenium atom, resulting in CO elimination. The assumption
that 3 is an intermediate on the route from 2 to 4 is corroborated in that under the chosen reaction conditions pure
3[61
is converted into 4.
CHzPh
H,
N
,CHzPh
3
Stepwise Hydrogenation of Benzonitrile
on a Ru,-Cluster**
By Wolfgang Bernhardt and Heinrich Vahrenkamp*
Nitriles can be reduced to amines by H2 under pressure
using metal catalysts, e.g. Raney nickel. Single steps of this
reaction have been studied in an exemplary way for Fe3clusters"'. Here, we report other part-steps which occur on
Ru3-clusters.
With the aim of obtaining the p3-qz-benzonitrile complex 1, we passed Hz into a mixture of R U ~ ( C O )and
,~
PhCN in ligroin for 30 min at 130°C using the conditions
described by KeZZer et al.['I for the corresponding Fe3-complex"]. However, instead of 1 we isolated the orange-yellow p2-q'-complex 2 in 41% yield after chromatography on
silica
1
2
The CN-containing ligand in 2 is derived from benzylideneamine, the initial product of hydrogenation of benzonitrile. For this reaction to occur under the very mild hydrogenation conditions, coordination of the substrate to
the cluster is a prerequisite. Whether complex 2 is formed
from a precursor related to 1 is not yet clear. The constitution of 2 is determined by crystal structure analysis[41.The
C=N bond length in 2 (127 pm) is in the double bond region; the C=N bond in benzonitrile is 13 pm shorter[51.All
the atoms of the benzylidenamino ligand and the two
bridged ruthenium atoms are coplanar, and this plane
forms an angle of 109" with the Ru3 plane.
Further hydrogenation of 2 should afford the recently
described 3[61.
However, renewed reaction of 2 with H2 as
described above gave 49% of the orange-yellow p3-q1-complex 4 after 90 min. The composition of 4 results from elemental analyses and the EI mass spectrum, and its struc[*] Prof. Dr. H. Vahrenkamp, Dipl.-Chem. W. Bernhardt
Institut fur Anorganische und Analytische Chemie der Universitat
Albertstrasse 21, D-7800 Freiburg (FRG)
[**I
This work was supported by the Fonds der Chemischen Industrie and
by the Rechenzentrum der Universitat Freiburg.
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 5
4
The bonding and activation of the substrate by several
metal atoms in these complexes is an example for the cluster-surface analogy. In contrast to the Fe3/nitrile system['I,
in which the key steps occur on y3-bonded, CN-containing
ligands, the present case demonstrates that complete hydrogenation of the CN bond at atmospheric pressure is
possible with coordination involving only the nitrogen and
two metal atoms. We are presently attempting to obtain the
precursor complex of 2 containing unaltered benzonitrile
and to find a method of cleaving the benzylamine from
4.
Received: January 24, 1984 [Z 685 IE]
German version: Angew. Chem. 96 (1984) 362
[I] M. A. Andrews, H. D. Kaesz, J. Am. Chem. Soc. I01 (1979) 7238,7255.
121 E. Keller, D. Wolters, Chem. Ber. 117(1984) 1572.
[3] 'H-NMR data (CDC13, int. TMS) for 2 : 6=9.05 (NCH), 7.58 (Ph, m),
-13.30 (Ru2H); 4 : 6=7.33 (Ph, m), 5.04 (CHI), -17.13 (Ru2H).-IR
data (C6HIZ,cm-') for 2 : 2097 w, 2061 vs, 2051 s, 2020 s, 1997 sh, 2003
m, 1985 w, 1965 vw, 1952 vw; 4: 21 1 1 m, 2078 s, 2052 vs, 2042 sh, 2028 w,
2010 s, 1992 s, 1980 m.
[4] Monoclinic, P2,, a =960.5(2), b=929.4(2),
c = 1306.0(3) pm,
~=111.23(2)", Z=2 , 2463 reflections, R=0.031. Further details on the
crystal structure investigation can be obtained from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2, by quoting the depository number CSD 50674, the names of the
authors and the journal citation.
[5] G. Fauvet, M. Massaux, R. Chevalier, Acfa Crystallogr. 8 3 4 (1978)
1376.
[6] P. M. Lausarot, G. A. Vaglio, M. Valle, A. Tiripicchio, M. Tiripicchio-Camellini, J. Chem. SOC.Chem. Commun. 1983, 1391.
[7] E. Sappa, 0. Gambino, G. Cetini, J. Organomel. Chem. 35 (1972) 375; E.
Sappa, L. Milone, ibid. 61 (1973) 3x3.
Dialkylboryl-Substituted Triphenylphosphonium
Ylides
By Hans-Jurgen Bestmann* and Thomas Arenz
The hydrogen atom in triphenylphosphonium ylides of
via transylidation by reactions
type 1 can be
with halogen compounds in the molar ratio 2 : l['I. So far
these reactions have only been carried out with halides of
elements of the 4th-7th main groups of the Periodic System[2~31.
It can be expected that ylides in which an element of the
1st to 3rd main groups is bonded to carbon are more stable
[*I Prof. Dr. H. J. Bestmann, Dipl.-Chem. T. Arenz
Institut fur Organische Chemie der Universitat Erlangen-Nurnberg
Henkestrasse 42, D-8520 Erlangen (FRG)
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
0570-0833/84/0505-0381 $02.50/0
381
than 1. We therefore examined reactions of the readily accessible dialkylchloroboranes 214]with phosphoranes 1IS1.
diate. 3 decomposes in an equilibrium reaction into 2 and
1. Compound 1 reacts with further HCl to give the phosphonium salt 6 and is thus removed from the equilibrium.
The chloroborane 2 formed in the reaction was detected
by reaction with methanol and subsequent conversion of
the dialkyl borinate into the ketoners1.
Received: January 24, 1984;
supplemented: February 29, 1984 [Z 687 IE]
German version: Angew. Chem. 96 (1984) 363
1
0
R'-i.-BTi;
4
0
+-+ R'-C=BR;
I
I
HCI
PPh,
+
8
[R'-CH,-PPh,]
C1'
PPh,
0
8
5B
5A
6
In boiling benzene the reaction proceeds as expected
with transylidation and formation of the a-dialkylborylsubstituted triphenylphosphonium ylides 5L61
(Table 1) and
the phosphonium salts 6, which precipitate from the solution. We assume that the adduct 3 is initially formedL7]
and
is subsequently converted into 4. The products 5 and 6
are obtained by reaction of 1 with 3 as well as 4.
Table 1. Dialkylboryl-substituted triphenylphosphonium ylides 5 by reaction
of 1 with 2 in the molar ratio 2: 1. NMR: &values, v,,,=line width in the
"B-NMR spectrum.
R'
CH3
b C2HS
c CH,
d C6Hs
e C6HS
f CsHs
a
RZ
Yield
[%]
'IP
[a1
c-CsH9fi] 65
c-CsH9[b] 85
n-CSHII 88
n-C5HI,
76
c-CsH9[bl 71
C-C~HII[C] 70
NMR
"B
MS
vIlz Int. [%] [g]
[Hz] M + - 1
+26.2 +56[d] 436
f27.0 +%[el 402
f24.2 +54[d] 344
+19.2 +52[e] 384
+20.6 +58[e] 360
+20.7 +51[d] [fl
22
24
23
22.5
24
21.5
M+ M++1
100
100
100
100
100
100
29
30
25
35
37
39.5
[a] In C6D6, H3P04 as external standard. [b] Cyclopentyl. [c] Cyclohexyl. [d]
In C6D6 at RT; Et20-BF3 as external standard. [el In [Ds]toluene, 80"C,
Et20-BF3 as external standard. [Q Extremely flat bands. [g] Intensity in molecular ion region.
The new ylides, which can be described in terms of the
mesomeric formulations 5 A + +5B, are crystalline compounds which decompose without melting sharply over a
wide temperature interval on heating. The 'H-NMR data
of 5 are consistent with expectation. In the l3C-NMR
spectrum the absorption of the C atoms directly bonded to
boron is characterized by strong line-broadening. The I 'BNMR spectrum shows a broad signal in the region 6 = 50
(diethyl ether/trifluoroborane as external standard),
whereas trialkylboranes absorb at 6= 80. The 31P-NMR
signal appears at 6 = +20 to +27 (H3P04 as external
standard) and is thus shifted downfield into the resonance
region of stabilized phosphonium ylides compared to that
of the ylide 1. We ascribe the upfield shift of the "B-NMR
signals compared to those of trialkylboranes and the
downfield shift of the 3'P-NMR signals compared to those
of the phosphorane 1 to participation of the mesomeric
form 5B with partial B=C double bonding.
When anhydrous hydrogen chloride is passed into a solution of 5 in ether or tetrahydrofuran the title compounds
decompose to the starting compounds 1 and 2. 3 is
formed on addition of HCl, but it cannot be established
whether the phosphonium chloride 4 occurs as interme382
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
[I] H. J. Bestmann, Chem. Ber. 95 (1962) 58.
[2] a) H. J. Bestmann, Angew. Chem. 77 (1965) 609,651; Angew. Chem. Znt.
Ed. Engf. 4 (1965) 583,645; b) H. J. Bestmann, R. Zimmermann in Houben-Weyl: Methoden der Organischen Chemie, 4 edit. Vol. E l , Thieme,
Stuttgart 1982, p. 636ff.
131 H. Schmidbaur, Acc. Chem. Res. 8 (1975) 62.
141 R. Koster in Houben-Weyl: Methoden der Organischen Chemie, 4th edit.
Vol. XIII/Sa, Thieme, Stuttgart 1982, p. 378ff.
[5] For a different reaction of trialkylphosphonium ylides with halides of elements of the 1st-3rd main and sub-groups of the Periodic System cf.
131.
[6] A boron-substituted phosphonium ylide has been reported on but not isolated: D. S. Matteson, D. Majumda, Organometallics 2 (1983) 230.
[7] For adducts of 1 and borane see H. J. Bestmann, K. Siihs, T. Roder, Angew. Chem. 93 (1981) 1098; Angew. Chem. Znt. Ed. Engl. 20 (1981)
1038.
[8] B. A. Carlson, H. C. Brown, J . Am. Chem. SOC.95 (1973) 6876.
A Binuclear Molybdenum Complex with
Two p-Hydrazido(3- ) N-Ligands
By Rainer Mattes* and Heinz Scholand
Alkyl dithiocarbazates NH,NHC(S)SR are versatile ligands: thus, complexes with N-, S-, or N,S-coordinated
neutral ligands are known, as are also chelate complexes
of the singly (at N") or doubly (at N" and NO) deprotonated ligands"]. Alkyl dithiocarbazates can also be used as
starting substances for the synthesis of diazenido complexesL2].In mononuclear compounds of this type the N2R'
group functions either as formal 3-electron donor with linear M-N-N arrangement or as 1-electron donor with
angular M-N-N arrangement. For binuclear complexes
with diazenido bridge-ligands, structure types A - C are
conceivable; examples for all three cases are already
knownr3].
A
B
C
On attempting to convert the diazenido-hydrazido(1 -)molybdenum complex l r 2 I into the corresponding
hydrazido(2 -) complex by protonation, we have now obtained the neutral, diamagnetic binuclear complex zL4].
The molybdenum complex 2 represents a novel example
for the versatile ligand properties of alkyldithiocarbazates.
As shown by an X-ray structure analysis['] (cf. Fig. 1) the
two molybdenum atoms in 2 are linked together via two
N2R' groups (R'= C(S)SEt) analogously to the general
type A ; concomitantly, however, the two N,C(S)SEt
groups function as N,S chelate ligands via the terminal sulfur atom. The bonding is best described in terms of the me[*] Prof. Dr. R. Mattes, DipLChem. H. Scholand
Anorganisch-chemisches Institut der UniversitSLt
Corrensstrasse 36, D-4400 Munster (FRG)
0570-0833/84/0505-0382 $02.50/0
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 5
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