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Coordination Chemistry.

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C O N F E R E N C E REPORT§
Coordination Chemistry
The 8th International Conference on Coordination Chemistry
was organized by the Verein Osterreichischer Chemiker
( A . Maschka) and was held in Vienna (Austria) from September 7th to 1 lth, 1964 under the chairmanship of V . Gritmonn. There were 850 participants from 34 countries, and the
155 lectures and discussions were dedicated to three major
problems: the nature of the chemical bond in coordination
compounds, novel coordination compounds, and new results
and methods in coordination chemistry in solution [I].
P l e n a r y L e c t u r e s [2]:
New Approaches to the Theory of Complex Ions and
Their Physical Foundations
H . Hrrrrrnanrt, Frankfurt/Main (Germany)
A “united atom model” for complex compounds has been
developed which affords information beyond the limitations
of the ligand field theory (crystal field theory) with reasonable
calculatory effort, provided the mathematical operations are
carried out precisely, and which is still applicable even when
MO-LCAO calculations fail owing to non-orthogonality of
the functions belonging to the various centers involved. I n this
model, use is made of hydrogen-like single-center functions
which correspond in their symmetry and in the nature and
number of their nodal surfaces to MO-LCAO multicenter
functions. I n the Hamiltonian operator, a term c/r2 is
included for correction; the only parameters used are a
variation parameter (Zeffective) a n d a free parameter (c in
the term c/r2). This model gives very close agreement with
experimental data for Ti(Il1) and V(II1) complexes.
[W2Clo]3- since the W--W distance (2.40 A) here is much
shorter than in tungsten metal (2.74 A). M-M quadruple
bonds even occur in [Cr(CH3C00)212 and in the
diagmagnetic ion [RezC18]2-, where the Re-Re distance
(2.27 A) is extremely short and overlap of d,z (= s),dx, and
d,, (= x), and d,, (= 6 ) orbitals occurs.
The number of compounds with a-M-M bonds between two
different metals is still relatively small. The combinations
observed are V-Au, W-Mo, W-Au, Mo-Fe, Mn-Re,
Mn-Fe, Mn-Co, Mn-Cu, Mn-Au, Fe-Co, Fe-Ni, Fe-Cu,
Fe-Ag, Fe-Au, Fe-Hg, Co-Cu, Co-Ag, Co-Au, Rh-Hg,
Ir-Hg, Pd-Pt, and Pt-Cu. Atoms with a d*osl configuration
form particularly strong bonds. Thus, the bond energy for
Au-Au is 51.5 kcal/mole, for Cu-Au 54.5, for Ag-Au 47.6,
for Cr-Au 50.4, and for Sn-Au 57.5 kcal/mole. a-Metalmetal bonds can be strongly influenced by back-donation
from the metals to ligands and from ligands to the metals, by
7r-M-M bonds, by repulsion effects from non-bonding
orbitals, and by steric requirements. Metal-metal bonds are
best recognized by combination of Raman and infrared
spectroscopy (M-M frequencies lie below 200 cm-I), X-ray
structural analysis, and magnetic measurements. There is
considerable variance in the lengths of the bonds observed to
date for individual elements depending o n the strengths of
the bonds in question.
Tetrahedral and Octahedral Cationic Chelates of
Main Group Elements
E. L. Muetrerties, Wilmington, Del. (U.S.A.)
Salts such as [ L ~ B H ZXo
] ~ with ligands L = RzS, R3N, R3P,
and R3As can be prepared according to Equations (a) and (b)
LBH3
Metal-Metal Interactions in Coordination Compounds
L. Lewis, Manchester (England)
Compounds with metal-metal bonds between the same
elements have so far been found foi all transition elements
with the exceptions of zinc and metals of the scandium group.
Here the elements occur in any oxidation state from + 5 to -1
and with electronic configurations (of the electrons not
bonded to ligands or anions) dl-dl to d9-d9 and s1-s’;
d6--d6 is never observed. They also occur in the most diversiCS
fied structural arrangements, e . g . Mo in [Mo(OC6H&C12]2
+4
(dl-dl),
MOO^]^ (dz-d’),
+1
+2
+3
[M02Clg]3- (d3-d3), [MOCI~],
[L2BH2J0
+ [L2BHzlmXo
2 L + [L‘2BH2J0
+ H2
(a)
+
(b)
+ 2 L‘
as well as by the reaction of LBH3 with B2H6, which leads
~.
with evolution of hydrogen to [L2BH2I0 [ B I ~ H I I L ]Compounds of the type [L2BH2laOHO are strong bases, [L2BH#
ClO are strong electrolytes. The cation [ ( R ~ N ) Z B H ~ is
]@
remarkably stable. It is not attacked by concentrated sulfuric,
hydrochloric, or nitric acid, alkalies, Au30,30 ”/, H202 up to
100°C, 12, or Friedel-Crafts reagents. When heated at 100°C
with q u a regici, the complex is converted without decomposition into [(R3N)2BHCI]@. Its salts decompose according
to Equation (c) below 180°C in the presence of small,
compact anions (X = CI, Br, or N3).
-1
(d4-d4), [ M O ( ~ - C ~ H ~ ) ( C O(d5-d5),
) ~ I ~ and [Mo2(CO)&(d7-d7). The tendency for M-M bonds to be formed is
greater in the second and third periods of transition elements
as well as in higher groups of transition elements and at
lower states of oxidation of the elements. Frequently there
are ligand bridges in addition to the M-M bonds. Occasionally structural units are observed where 3, 4, 5, or 6 metal
atoms are intercombined and remain together even in solution. Thus, for example, there are always 3 atoms of rhenium
at the corners of the equilateral triangle in the entities
[ReCI3],, [(R3P)3Re3C191, [Re3C111]3-, and [ R e 3 C I d - . A
M = M triple bond is postulated in the diamagnetic ion
[I] Abbreviations used in this report are: El = atom of an
element, L = ligand, M = metal, R = organic ligand, THF =
tetrahydrofuran, s* = sip hybrid orbitals.
[Z] Complete and partially extended versions of the plenary
lectures will be published in the Journal of Pure and Applied
Chemistry.
248
+ LHoXo
[(R~N)~BHz]‘X’
+ R3NBXHz
-C
NR3
(c)
Amine exchange occurs above 15O”C, e . g . according to
Equation (d).
[(R3N)2BH2l3
+ R2NC2H4NR2
+
[ ( R ~ N C ~ H ~ N R ~ ) B+
H2
Z ]NR3
@
(d)
For theoretical reasons, this can be preceded only by a dissociation equilibrium [Equation (e)].
[(R3N)zBH2l0
+
+
[H2BNR3]@ NR3
(e)
Substitution of the hydrogen atoms can be achieved only by
means of radical reactions. Thus, [(R3N)lBH2]9 reacts with
fluorine in aqueous solution to give [(R3N)2BF2IG, with
F S 0 2 0 0 S 0 2 F to give [(R3N)2B(OS02F)2]@,and with ICI to
give [(R3N)2BC12]@.The stability of the other complexes
decreases in the series R3N > R3P > R3As > R2S.
Angew. Chem. internat. Edit. 1 Vo1. 4(1965)
1 No. 3
a-Perfluoroalkylmetal complexes are generally very stable
and have confirmed the theoretical predictions by Orgel that
additional CO valence frequencies should appear in the
infrared spectra of carbonyl complexes with distorted symmetry owing to splitting of the E bands and appearance of
an additional B1 band.
The anions (C7H502)’ ( I ) and (CgHllN2)O (2) derived from
tropolone and its methylaminomethylimino derivative, respectively, give rise to pseudotetrahedral (D2d) cations
(C7H502)2B@and (CgHllN2)2B@.The salt (C7H502)~BeBre
is a strong 1 : 1 electrolyte, (C9HllN2)2B@OHe is a strong
base. Salts of the pseudo-octahedral ions (CgHllN2)3EI@with
El = Si, Ge, or Sn are also strong electrolytes. On the other
hand, (C7H502)3SnCI and (C7H502)3SnCeH5 - which can be
sublimed - are non-electrolytes with seven-coordinated t i n .
Experiments with ISOH have revealed that hydrolysis of
(C7H502)3EIQ proceeds primarily by substitution on the
ligands and not by attack of the central atom. Other ions
produced included (C7H502)3P2^ (from PC15 and 3 C7H602),
(C,H502)2As(OH)? and the eightfold coordinated compounds (C7H502)4Nb@Clo and (C7H502)4Ta@CIO. Hydrolysis of (C7H.j02)4Nb0 yields (C7H502)3NbO, but
(C7H502)4Taa is not markedly hydrolysed even at 140 “C.
The Role of Organometallic Compounds in the
Development of Coordination Chemistry
F. G. A . Stone, Bristol (England)
Starting from r-C5H5V(C0)4, Fe(C0)5, HMn(C0)5, and
NaMn(CO)5, complex compounds containing metal-carbon
bonds were prepared whose investigation led to the discovery of novel classes of compounds and which have brought
decisive advances in the development of coordination
chemistry and organometallic chemistry. Thus, C5HsV(C0)4
reacts with cycloheptatriene to give a T;-aromatic complex
( C ~ H ~ ) V ( C ~ in
H Swhich
)
V has the oxidation state zero. The
weakly paramagnetic compound [n-CgHsV(SCH3)212, which
is also prepared via C5HsV(C0)4, is a binuclear complex
with four S(CH3) bridges and strong V-V bonds. Paramagnetism occurs within the thermic range. Iron pentacarbonyl is substituted even at room temperature according
to Equation (f) to giveo-perfluoroalkyliron complexes (n = 1,
2, or 3 ) .
Intermediates in the Electrode Reactions of
Coordination Compounds
A . A . VICek, Prague (Czechoslovakia)
Redox processes at inert polarized electrodes differ from
those occurring with redox reagents in homogenous solution.
They sometimes take a different course, and in the case of
complex ions, often proceed via a number of chemical transformations not occasioned by redox processes, e.g. alterations
of the type or number of ligands attached to the complex.
D1
72
D2
+e-
+ D; +
+ .. ..D,
. . . DZ
Only the particle with the greatest redox activity (Dn) reacts
at the electrode. If the rates of the subsequent chemical
transformations D, + DE are slow, it is possible to detect
otherwise unrecognizable intermediates by polarography at a
dropping mercury electrode and even occasionally to prepare
the species by electrolysis. Thus, [Mn(dipy)3]2? is reduced at
-1.5 volt in 1 M alcoholic LiCl to stable [Mn(dipy)3]Q,which
had hitherto never been isolated in the form of salts; beyond
- 1.6 volt reduction of the dipyridyI ligands begins. On homogeneous reduction in aqueous systems, [Ni(CN)4]23 leads to
[Ni2(CN)#”, and in liquid ammonia to [Ni(CN)4]4”. It can
be concluded from electrode processes that it is always the
complex of nickel with the oxidation state zero that is formed
first and that this is rapidly oxidized by water to give
[Ni2(cN)6]4e. The primary product of electrode reduction
of [Cr(CN)5NO]30 is [Cr(CN)5N0]4@,which can be isolated
as such by electrolysis in 0.1 M NaOH; however, below
p H 9.5 the species is decomposed by addition of two protons
or because further reduction occurs. Rapid oxidation of
[Co(dipy)3]3 in the presence of catalytic amounts of
[Cr(CN)~N0133in homogeneous solution proceeds via the
steps shown in Equations (h) and (i).
+ [Cr(CN)sN0]30
[Cofdipy)3]@
--f
+
[Co(dipy)3]2@ [Cr(CN)sNO]4”
+
[ C ~ ( C N ) S N O ] ~H0
~
+ [Cr(CN)5N0]33
+H
(h)
(0
x-C5H5Co(CO) (CnF2,tl)I or r-C5HsNi(CO) (C,F2n+1), for
F r o m t h e R e s e a r c h Reports[31:
example, can be prepared analogously. Fe(C0)5 reacts with
dibutyldivinyltin to give [(C4Hg)2SnFe(C0)4]2. Mn(C0)4NO
is a compound that is isosteric with Fe(C0)s and has a
The major accent of preparative and synthetic coordination
trigonal bipyramidal structure; it is a deep red diamagnetic
chemistry still lies on the field of carbonyl, x-aromatic, and
liquid which decomposes o n exposure to air and whose
n-olefin complexes, although increasing attention is being
vapors are similar to those of bromine. It is formed from
paid to the corresponding a-compounds. New aspects worthy
HMn(C0)5 and p-CH3-C6H4S02-NCH3-NO
in ether
of inclusion in textbooks have appeared in the preparation
at 25°C i n the dark. Tetrafluoroethylene adds onto
of a-metal-metal compounds and also in the detection of
HMn(C0)sin pentane at20 OC and 2 atm to give H(CF2)zMnmultiple bonds in 0 x 0 complexes of transition metals (e.g. in
\Q
0
(CO)5. Analogous reactions were achieved with the carboiiyl
;VO or ‘CrOz), whose structures ( e . g . ,V =O analogous
hydrides of W, Re, and Fe and with RMn(C0)S (R = CH3 or
0 0’
C6Hs) o n the one hand and with CIFC=CFp, C12C=CF2, and
to C E O ) explains their stability even towards protons.
F ~ C - C G C - C F ~ on the other. NaMn(C0)s reacts with
X-ray structural analysis and magnetic measurements (tox-C~H5Fe(C0)21or Re(C0)5CI to give x - C ~ H ~ ( C O ) ~ F ~ - M ~gether
with ESR and N M R spectroscopy) are still the most
( c o ) 5 or (CO)5Re-Mn(C0)5, i . e . carbonyl complexes with a
important aids for elucidating the details of the structures
covalent hetero-metal-metal bond. With perfluoroalkylof coordination compounds: novel possibilities are offered
carbonyl chlorides it reacts to give compounds of the type
by application of the Mossbauer effect [E. Fluck, Heidelberg
CnF2,,1COMn(C0)5, which o n heating decompose into CO
(Germany): I . Danon, Rio de Janeiro (Brazil)]. I n the followand CnF2n+1Mn(C0)5. An analogous reaction takes place
ing, a short review will be given of the most important results
according to Equation (g).
of preparative and synthetic coordination chemistry reported.
2 C3F7COCI
+ Na~Fe(C0)d +
2 NaCl + 2 CO + (C3F7)2Fe(C0)4
Angew. Chem. internnt. Edit. / Vol. 4(1965)
/ No. 3
____.
(g)
131 Cf. V. Gutrnann: Proceedings of the 8th International Conference on Coordination Chemistry. Springer, Vienna-New York
1964.
249
Metal-Metal Compounds
sion i n Nujol within 5 h at 25 “ C [A. Wojcicki, Columbus,
Ohio (U.S.A.)]. N ~ M O ( C O ) ~ ( C ~
reacts
H ~ ) with CH3SCHzCI
In T H F at 25OC t o form C H ~ S C H ~ M O ( C O ) ~ ( C
which
~H~)
Metal-metal bonds occur i n pure metals (Cu), metallic alloys
o n irradiation with ultraviolet light is transformed into
(Cu/Zn), and salt-like alloys (Cs“Au”), as well as in comCH~SCH~MO(CO),(C~H
both
~ ) ;compounds are yellow and
melt at 66-67 OC, and both are supposed to involve r-bonds
pounds of transition metals with low states of oxidation
over the CH2=%-CH3 moieties. (CH3S)Fe(C0?2(C5H5), m.p.
[MO6C112]; Ta6Cl14), in s*-donor compounds
(“MOCl2”
67-69 “C, is a monomer without sulfur bridges [R. B. King,
([Pt(SnCl3)412a) and d-donor compounds (Ni-diacetylPittsburgh, Pa. (U.S.A.)]. J. A . Ibers, Upton, N.Y. (U.S.A.)
dioxime), and finally in distinctly covatent o-bonding species
and
) ~ ] ) , succeeded in elucidating the details of the structures of the
such as s*/s* (Hg2C12), s*/d ( [ ( C ~ H ~ ) ~ P A U M ~ ( C O
crystalline carrier of molecular oxygen (02)IrCI(CO)d/d ([Mn2(CO)& Classes of compounds prepared for the
first time were LM-M’(CO),, pale yellow to clear brown
[(P(C6H5)3]2,which can be prepared from its components and
solids with melting points between 80 and 2OOOC (L =
IS comparable with the Oz/oxyhemoglobin complex, and of
the analogous complex (SOz)IrCi(CO)[P(C6H5)3]2.
(C6Hs)3P+, H ~ C - C [ C H Z A S ( C H ~ ) Z H3C-AsICoH4-0I~~,
As(CH3)2123 ; M = Cu, Ag, or Au; M’ = V, W, Mn, Fe, or
Co; and n = 4,5, or 6) [R. S. Nyhulni, London (England)],
and L3XzM-HgX’ and LzX,M’-HgX’ (L = (C6H5)2A~CH3
x- and 5-Complexes with Aromatics and Olefins
or (C6H5)3P; M = Rh or 0 s ; M’ = I r ; X = CI, Br, or CO;
and X‘ = F, CI, Br, I, CN, or SCN) [K. Vrieze, London
(England)].
The reaction of triphenylcyclopropenyl bromidewithNi(C0)4
Crystallographic analysis of (C6H5)3P + Au-Mn(C0)s inin methanol leads to red crystals of the bromine-bridged bidicated a linear P-Au-Mn
arrangement with an Au-Mn
nuclear complex { [~-(C6H5)3C3]Ni(CO)Br}2[S. F. A . Kettle,
distance of 2.47 A (rAu = 1.2 and r M n = 1.27 A), whereas
Sheffield (England)]. x-Tetraphenylcyclobutadienepalladium
the bonding radius of the Mn in Mn2(CO)lo is 1.46 A
dibrornide is obtained via diphenylacetylene and is suband in (C6H5)2Sn[Mn(CO)5]~is 1,3l A; here the two
stituted by triphenylphosphine to form octaphenylcubane
[ H . A4. Powell, OxSn-Mn distances are both 2.70
according to Equation (k).
ford (England)]. In the violet crystals of composition
K],&‘t(C204)2.2.5 H 2 0 (Pt-Pt = 2.76 A) and K ~ P ~ ( C N ) ~ C I O , ~
(Pt-Pt = 2.83 A), the Pt-Pt distances are unusually short
[K. Krogmann, Stuttgart (Germany)]. Investigations of the
structures of the cations [M6X12]20, where M = N b or Ta
and X = C1 or Br, revealed a n octahedral arrangement of the
Ligand exchange occurs with [ ( C ~ H ~ ) ~ P I ~toN ~form
B~Z
equivalent metal atoms - formally 2 M33 and 4 M20 is
[(C6H5)3P]~PdBr2
and
[(C,jH5)4C4]NiBrz,
and
it
reacts
with
expected - with strong M-M bonds [ M . B. Robin, Murray
Fe(C0)s
to
form
[(C6H5)4C4]Fe(CO), and
with
Hill, N.J. (U.S.A.)]. Molybdenum(lI) chloride reacts with
(CgHs)Fe(CO)zBr by transfer of the cyclopentadienyl group
pyridine or (C6kf5)3P to give the non - electrolytes
to yield ~ [ ( C ~ H ~ ) ~ C ~ ] P ~ ( C S H[P.
S )M.
} ~M
F a~ifBf i ~
s, ~ ~
( M o ~ C I ~ ) C Iand
~ L ~the electrolytes [(Mo6Cls)C13L3]CI and
Hamilton, Ont. (Canada)].
[ ( M O ~ C I ~ ) C ~ ~ L ~ ( R[C.
O J.
H )Wilkins,
~ ~ C ~ Christchurch
~
(New
The complex C13Hl,Ni(C5H5) formed from NaC5H5 and
Zealand)].
[(CH3)4C4]NiC12was recognized by X-ray structural analysis
to be x-cyclopentadienyl-1,2,3,4-tetramethyl-~-cyclopenta1’,3’-dienocyclobutenyInickel(Il), a representative of a
Carbonyl Compounds
completely new type of compound [ L . Dahl, Madison, Wisc.
(U.S.A.)]. The reaction of ZrCI3 with cyclopentadiene at
200°C leads to (x-C5H5)ZrC13. ZrCl4 reacts with NaC5H5 to
Vanadium hexacarbonyl reacts with benzene with liberation
form yellow (z-CgH5)4Zr. The [(z-CsH5)2ZrCl]z formed
of 2 moles of CO to form [V(C0)4C&j] [v(co)6], which can
from “(C5H5)2ZrC12”and aniline reforms the “(C5H5)2ZrC12”
be converted into the compounds [V(CO)C&6]PF6 and
with HCI without liberation of hydrogen, hence there must
[V(C0)4C&j] [B(C6H5)4] [E. Calderazzo, Geneva (Switzerbe a hidden proton somewhere in this compound [ A . F. Reid,
land)]. Trimeric [Mn(C0)4]3 and polynuclear derivatives
Melbourne (AustraIia)]. F. Jellinek, Groningen (Holland)
[M(CO)4], where M = Mn, Tc, or Re were formed during
succeeded in preparing purple colored (C5H&Ti(C3H5), m.p.
attempts to prepare M(C0)sH [ H . Kuesz, Los Angeles, Calif.
1 18 “C,and a similar complex ( C ~ H S ) ~ T ~ ( C H ~ C
M.
~ Cais,
HS).
(U.S.A.)]. New hydrides and carbonyl hydrides of iridium
Haifa (Israel) reported on some metal complexes ofthe pentalwere obtained by L. Mulatesta, Milan (Italy): H31rL2 (m.p.
ene system,e.g. [(CsH6)Mn(C0)3]aXC. Crystalline olefin com145’C), H3IrL~py(m.p. 134”C), HIr(CO)L2, and H3Ir(CO)L2
plexes of silver of general formula [Ag(RR’C=CR’R)]flBFi3
with the isomers cis,cis-, and trans-H, and cis-L, where L =
have z-bond character [ H . W. Quinn, Sarna (Canada)]. The
(Cf,H&P.
Carbonyl acetylene complexes of tungsten such
chlorine-bridged complex [ C I ~ P ~ ~ ( T ~ - C ~obtained
H ~ C I )from
~]
as (RC=CR’)3W(CO) with R and R = CH3, C2H5, and
PdClz(C6H5CN)2and butadiene reacts rapidly with alcohols to
C6H5 [D.Ture, Akron, Ohio (U.S.A.)], of iron such as
O R complex
)~].
[CI~P~Z(C~H~CI)~]
(RC =CR)Fe(C0)4
(yellow),
(RC E C R ) ~ F ~ Z ( C O ) ~ ,yield [ C I ~ P ~ ~ ( T - C ~ H ~The
can be prepared analogously with allene. NazPdCId and allene
(RC=CR)xFe2(C0)6, ( R C G C R ) ~ C O F ~ ~ ( C(RC=CR’)O)~,
form the Tc-complex [Cl2Pd2(C6H&1)21 [s.Robinson, Leeds
Fe2(C0)7 (dark-green), and (RC =CR’)Fe3(C0)9 [C. Hoog(England)]. Dahl found that [(x-C3H~)PdCll2crystallizes in
zand, Brussels (Belgium)], and of cobalt such as [(CH3)3the space group C2h-2/m. The reactions with hydrogen and
C-C %CHI, (HC=CH)Co2(C0)4, and (HC =CH)Co2(C0)9
with sodium acetate of the [(diolefin) (ROH)PdCi] complexes
[O. S. Mi& Manchester (England)] were prepared and
which have a x-ally1 structure were described by E. J . Smuttheir occasionally unusual constitutions elucidated. M. Tsutny, Emeryville, Calif. (U.S.A.). Unstable complexes of allene
sui, New York, N.Y. (U.S.A.) treated estrone with Cr(C0)6
and transition metals are highly active and selective catalysts
and acetylergosterol as well as vitamin A acetate with
for converting butadiene into cyclodecatriene, 4-methyl-l,3,6Fe3(CO)12 and succeeded in isolating the derivatives estroneheptatriene, or 1,2-polybutadiene, and for polymerizing
Cr(C0)3, acetylergosteroI-Fe(CO)3, and vitamin A acetateethylene in solution [ G . WiNCc, MiilheimjRuhr (Germany)l.
Fe(CO)3. The reaction of Co2(CO)p with Ss led depending
S . F. Mason, Exeter (England) reported on some 5-z-corn) ~[Co2(C0)5Sln
SZ,
on the Co: S ratio to C O ~ ( C O ) ~ S , C O ~ ( C Oor
plexes of cobalt and iron, c.g. tricarbonyloctafluoro-1,3[L. Marko, Veszprem (Hungary)]. (CO)sMn-SCN can be
cyclohexadienyliron, and E. Kurras, Jena (Germany) deprepared from (C0)SMnNa with ClSCN and rearranges
scribed o-z-allylchromium complexes and the dark violet
within 5 min at 25°C in acetonitrile to its bond isomer
compound Li.$[V(o-C6H5)6].
(CO)sMn-NCS, but is reformed from the latter in suspen-
-
250
Angew. Chem. internat. Edit.
/
Vul. 4{1965) / Nu. 3
Complex and Addition Compounds of Main
Group Elements
The methylammonium N-methylboranocarbamate formed
according to Equation (I) from methylamine and borane
carbonyl is converted by 2 moles of KOH in refluxing alcohol
2 CH3NHp
+ H3BCO
+
[CH3NH3] [CH3NH-CO-BH3]
(I)
via elimination of 2 moles of methylamine and 1 mole of
water into fine crystals of dipotassium boranocarbonate
8
KB[@O-CO-BH,]Ko which decomposes only on heating
above 400 "C, which is converted into the hydrogen carbonate
0
K@[HO-CO-BH3] by titration with acids, and which forms
coordination compounds with transition metals [ R . W. Parry,
Ann Arbor, Mich. (U.S.A.)]. The preparation of a yellow
crystalline sublimable borazole addition compound
[-(CH3)BN(CH3)-]3TiCl4 which dissolves readily in benzene
was achieved by H . Norh, Munich (Germany). Aminoborane
forms soluble 1: 1 complexes with iodine in inert solvents
[J. J. Lugowski, Austin, Tex. (U.S.A.)]. Acetonitrile and
tetramethyldiborane [R2BH]2 combine to form two isomers
of the type [ H ~ C - C H = N - B ( C H ~ ) Z ]of
~ m.p. 76 and ca.
-5 "C. Analogously, compounds of general formula
[RR'C=NAlR'2]2 are formed from R C N and AIR'3 at
150-250 "C [ K . Wade, Durham (England).
B. J. A y le ft, London (England) reported on silyl iodide
addition products, e.g . H&I(py)z and HjSiI(dipy), and
their reactions. Novel complexes of aluminum and gallium
with coordination number 4 were isolated by H . Schmidbnur,
Marburg/Lahn (Germany) in compounds of the types
[-(R3Si)O-AIR'2-12, Na[R'*AI(OSiRj)2], and K[Ga(OSiR3)41;
he also succeeded in preparing complexes of lithium with the
coordination number 2 in the form of the compounds
M[Li(OSiR3)2], where M = Na (m.p. 233-235'C) and K
(m. p. 258-262 "C). H . Burger, Graz (Austria) investigated
transition metal bistrimethylsilylamides M [N(SiR3)2In,where
M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, or Hg, which
are mostly intensely colored liquids or crystals and are
distillable or sublimate. From their infrared spectra and
behavior toward Lewis bases it can be seen when and whether
the lone pair of electrons on the nitrogen form x-bonds with
the silicon or with the metal atom. Tetra- and pentafluoroorganylsilicates such as [(C2H5)4N] [CH3SiF4], K2[CH3SiF5Ir
and (NH4)4[F5Si-CHCl-SiF5]
were prepared for the first
time by R . Mul/er, Dresden-Radebeul (Germany) and are
suitable as intermediates for separating methylchlorosilanes
produced by direct synthesis, as carburating agents, or for
the production of organomercury compounds. M. Onyszchuk, Montreal (Canada) managed to add two oxa rings
[-O(CHz)n-]ring with n = 2, 3 , 4, or 5 each onto SiF4 and
GeF4, and simultaneously obtained SiF4[O(CH3)2]2,
GeFd(CH3OH)2, GeF4[0C(CH3)2]2, and GeF40(CH2)40.
The GeF4 adducts are considerably more stable than the
SiF4 adducts. Some specially substituted phosphines and
phosphites were examined in their capacity as complexforming ligands, and compounds such as (CO)3Ni t
PRz-B(NR'2)z or the cyclic derivative [ + Ni(C0)2 c
PR~-B(NR~)-B(NR~)-RzP+Iring (Noth), octahedral complexes of Re(O), Re(Il), Re(III), and Re(V), e . g .
I(R2PCH2CH2PR&ReX2]GXs [E. S . Stern, Runcorn (England)] or Ni[tP(OCH2)3C-CH3]4 [J. G. Verknde, Ames, Iowa
(U.S.A.)] were obtained. K . Issleib, Halle/Saale (Germany)
synthesized such unusual compounds as P[FeP(C6H5)2]3,
P[Ti(PR2)213,or the cyclic complex [-Fe-PR-PR-PR-PR-]ring.
X-ray structural analysis of K4[Asp02Fs] indicated the
space group P21/n-C52h and the presence of a four-membered As0 ring [ W . Huase, Jena (Germany)]. XeF6
can be made to form complexes with Lewis acids; the
colorless solids F6XeBF3, m. p. 90 "C, F6XeAsF5, and
F&e(SbF& were isolated. They are extremely hygroscopic
and react with moisture to form highly explosive Xe03.
Structures such as F&e+ BF3, F5Xe@AsFp, and
F4Xe(FzSbF4)2 came up for consideration [ H . Selig, Argonne
111. (U.S.A.)].
Miscellaneous
W. Beck, Munich (Germany) prepared some new fulminato
complexes M(CNO), (with M-C bonds), e.g. HPt(CN0)
(PR3)2, Ni(CN0)2(PR3)2, Hg(CN0)2(PR&, the extremely
stable category of compounds (C6H5)3EI(CNO), where El =C,
Si, Ce, Sn, or Pb,and the explosive complexes(CH3)2TI(CNO)
and (C3H7)3Pb(CNO). G. W. A . Fuwles, Southampton
(England) reported o n addition compounds of the type
X4TiL2, X3TiL2, and C13VL2 in which X = C1 or Br, L = SRp,
and R = CH3, C2H5, or (CH&CH-. J. C. Curter, Pittsburgh,
Pa. (U.S.A.) obtained a labile complex (C5H&Ti(BloH13)2
from (C5H&TiC12 and NaBloH13. Dipole measurements on
the compounds [C13ReNC6H5(PR&] and [C13ReO(PR3)3]
0
6
8
Q
suggested strong x-Re ~ 0 and
1 x-Re E N bonds, comparable
Q
O
. 0 8
with C z O or ; C E N - C ~ H S[ J . Chuft, Welwyn (England)].
Fe(dipy)3 has formally iron of zero valence and is obtained
as deep green to blackcrystalsfrom thereaction of[Fe(dipy)3]lz
and LiZ(dipy) inTHF or ofFeC13 with dipyridyl and Liz(dipy);
it dissolves in benzene to give a violet solution and is very
sensitive to air and moisture [S. Herrug, Greifswald (Germany)].
[VB 874/178 IE]
German version: Angew. Chem. 77, 263 (1965)
Symposium on Macromolecular Compounds
The 3rd Symposium on Macromolecular Compounds took
place at Zurich (Switzerland) o n October 16th and 17th, 1964,
the main subject of this year's discussion being additives to
synthetic polymers.
From the lectures:
L. D d o g (Mainz, Germany) reported on the primary step in
autoxidation. As ageing of synthetic polymers is mainly due
to autoxidation, the initiation of this process is of interest.
The primary step consists of a direct reaction of molecular
oxygen with the organic compound. It precedes any autocatalytic oxidation which is initiated by peroxides present in
the substrate. The primary reaction could be observed by
Aiigew. Cliem. intertiat. Edit.
1 Vul. 4(1965) 1 Nu. 3
analysing very small conversions in the autoxidation of nbutyl methacrylate and of tetralin. Some deviations from the
usual kinetic relations were found. The mechanism could be
derived from the kinetics of the autoxidation of styrene,
indene, deuterated indene, and 1 ,I-dimethylindene. The primary step of the autoxidation was found to be a dehydrogenation of the organic compound by molecular oxygen, yiedling free radicals.
H . Harrel (Troisdorf, Germany) dealt with inhibitors of the
styrene polymerization. More than 100 inhibitors (quinones
and their derivatives, nitroso compounds, phenols, amines,
and hydrazines) were tested in concentrations of 10-2 mole- %.
At 90 O C , the time of induction, i. e. the time elapsing before
polymerization 'starts, was measured in relation to the
inhibitor concentration. The results allowed some conclusions
25 1
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