Formation of Metal Clusters or Nitrogen-Bridged Adducts by Reaction of a Bis(amino)stannylene with Halides of Two-Valent Transition Metals

Article abstract of DOI:10.1021/ic960007a

When the cyclic bis(amino)stannylene Me₂Si(NtBu)₂Sn is allowed to react with metal halides MX₂ (M = Cr, Fe, Co, Zn; X = Cl, Br [Zn]) adducts of the general formula [Me₂Si(NtBu)₂Sn-MX₂]_n are obtained. The compounds are generally dimeric (n = 2) except the ZnBr₂ adduct, which is monomeric in benzene. The crystal structures of [Me₂Si(NtBu)₂Sn-CoCl₂]₂ (triclinic, space group P?1; a = 8.620(9) ?, b = 9.160(9) ?, c = 12.280(9) ?, α = 101.2(1)°, β = 97.6(1)°, γ = 105.9(1)°, Z = 1) and of [Me₂Si(NtBu)₂Sn-ZnCl₂]₂ (monoclinic, space group P2₁/c; a = 8.156(9) ?, b = 16.835(12) ?, c = 13.206(9) ?, β= 94.27(6)°, Z = 2) were determined by X-ray diffraction techniques. The two compounds form similar polycyclic, centrosymmetrical assemblies of metal atoms bridged by chlorine or nitrogen atoms. While in the case of the cobalt compound Co is pentacoordinated by three chlorine and two nitrogen atoms, in the zinc derivative Zn is almost tetrahedrally coordinated by three chlorine atoms and one nitrogen atom. The iron derivative [Me₂Si(NtBu)₂Sn·FeCl₂]₂ seems to be isostructural with the cobalt compound as can be deduced from the crystal data (triclinic, a = 8.622(7) ?, b = 9.158(8) ?, c = 12.353(8) ?, α = 101.8(1)°, β= 96.9(1)°, γ = 105.9(1)°, Z = 1). If NiBr₂, PdCl₂, or PtCl₂ is combined with the stannylene, the reaction product is totally different: 4 equiv of the stannylene are coordinating per metal halide, forming the molecular compound [Me₂Si(NtBu)₂Sn]₄MX₂, which crystallizes with half a mole of benzene per molecular formula. The crystal structures of [Me₂Si(NtBu)₂Sn]₄·NiBr ₂·l/2C₆H₆ (tetragonal, space group I4₁/a, a = b = 43.86(4) ?, c = 14.32(2) ?, Z = 16) and [Me₂Si(NtBu)₂Sn₄4·PdCl ₂·1/2C₆H₆ (tetragonal, space group I4₁/a, a = b = 43.99(4) ?, c = 14.318(14) ?, Z = 16) reveal the two compounds to be isostructural. The molecules have an inner Sr₄M pentametallic core (mean distances: Sn-Ni 2.463 ?, Sn-Pd 2.544 ?) with the transition metal in the center of a slightly distorted square formed by the four tin atoms, the distortion from planarity resulting in a weak paramagnetism of 0.2 μ_B for the nickel compound. The halogen atoms form bridges between two of the tin atoms and have no bonding interaction with the transition metal. The nickel compound has also been prepared by direct interaction of Br₂ or NR₄Br₃ with [Me₂Si(NtBu)₂Sn]₄Ni as a minor product, the main products being Me₂Si(NtBu)₂Sn(NtBu)₂SiMe₂, Me₂Si(NtBu)₂SnBr₂, NiBr₂ and SnBr₂ . Other metal clusters have been obtained by the reaction of Me₂Si(NtBu)₂Sn with tetrakis(triphenyphosphine)palladium or by the reaction of Me₂Si(NtBu)₂Ge with RhCl(PPh₃)₃. In the first case Ph₃PPd[Sn(NtBu)₂SiMe₂]₃PdPPh ₃ (rhombohedral, space group R3c, a = b = 21.397(12) ?, c = 57.01(5) ?, α = β= 90°, γ = 120°, Z = 12) is formed and is characterized by X-ray techniques to be composed of a central PdSn₃Pd trigonal bipyramid with the tin atoms occupying the equatorial positions (Pd - Sn = 2.702(5) ?). In the second reaction all the triphenylphosphine ligands are replaced from rhodium and Rh[Ge(NtBu)₂SiMe₂]₂Cl is formed (monoclinic, space group P2₁/n, a = 12.164(2) ?, b = 23.625(5) ?, c = 24,128(5) ?, β = 102.74(3)°, Z = 4). The central core of this molecule is made up of a rhodium atom which is almost square planarly coordinated by the germanium atoms, two of which are bridged by chlorine (mean Ge -Rh = 2.355 ?).

Full text of DOI:10.1021/ic960007a

3848
Inorg. Chem. 1996, 35, 3848-3855
Formation of Metal Clusters or Nitrogen-Bridged Adducts by Reaction of a
Bis(amino)stannylene with Halides of Two-Valent Transition Metals
Michael Veith,* Alice Mu1ller, Lothar Stahl, Martin No1tzel, Maria Jarczyk, and Volker Huch
Institute for Inorganic Chemistry, University of the Saarland, D-66041 Saarbru¨cken, Germany
ReceiVed January 5, 1996X
When the cyclic bis(amino)stannylene Me2Si(NtBu)2Sn is allowed to react with metal halides MX2 (M ) Cr, Fe,
Co, Zn; X ) Cl, Br [Zn]) adducts of the general formula [Me2Si(NtBu)2Sn‚MX2]n are obtained. The compounds
are generally dimeric (n ) 2) except the ZnBr2 adduct, which is monomeric in benzene. The crystal structures
of [Me2Si(NtBu)2Sn‚CoCl2]2 (triclinic, space group Ph1; a ) 8.620(9) Å, b ) 9.160(9) Å, c ) 12.280(9) Å, R )
101.2(1)°, â ) 97.6(1)°, γ ) 105.9(1)°, Z ) 1) and of [Me2Si(NtBu)2Sn‚ZnCl2]2 (monoclinic, space group P21/c;
a ) 8.156(9) Å, b ) 16.835(12) Å, c ) 13.206(9) Å, â ) 94.27(6)°, Z ) 2) were determined by X-ray diffraction
techniques. The two compounds form similar polycyclic, centrosymmetrical assemblies of metal atoms bridged
by chlorine or nitrogen atoms. While in the case of the cobalt compound Co is pentacoordinated by three chlorine
and two nitrogen atoms, in the zinc derivative Zn is almost tetrahedrally coordinated by three chlorine atoms and
one nitrogen atom. The iron derivative [Me2Si(NtBu)2Sn‚FeCl2]2 seems to be isostructural with the cobalt
compound as can be deduced from the crystal data (triclinic, a ) 8.622(7) Å, b ) 9.158(8) Å, c ) 12.353(8) Å,
R ) 101.8(1)°, â ) 96.9(1)°, γ ) 105.9(1)°, Z ) 1). If NiBr2, PdCl2, or PtCl2 is combined with the stannylene,
the reaction product is totally different: 4 equiv of the stannylene are coordinating per metal halide, forming the
molecular compound [Me2Si(NtBu)2Sn]4MX2, which crystallizes with half a mole of benzene per molecular formula.
The crystal structures of [Me2Si(NtBu)2Sn]4‚NiBr2‚1/2C6H6 (tetragonal, space group I41/a, a ) b ) 43.86(4) Å,
c ) 14.32(2) Å, Z ) 16) and [Me2Si(NtBu)2Sn]4‚PdCl2‚1/2C6H6 (tetragonal, space group I41/a, a ) b ) 43.99(4)
Å, c ) 14.318(14) Å, Z ) 16) reveal the two compounds to be isostructural. The molecules have an inner Sn4M
pentametallic core (mean distances: Sn-Ni 2.463 Å, Sn-Pd 2.544 Å) with the transition metal in the center of
a slightly distorted square formed by the four tin atoms, the distortion from planarity resulting in a weak
paramagnetism of 0.2 µB for the nickel compound. The halogen atoms form bridges between two of the tin
atoms and have no bonding interaction with the transition metal. The nickel compound has also been prepared
by direct interaction of Br2 or NR4Br3 with [Me2Si(NtBu)2Sn]4Ni as a minor product, the main products being
Me2Si(NtBu)2Sn(NtBu)2SiMe2, Me2Si(NtBu)2SnBr2, NiBr2 and SnBr2. Other metal clusters have been obtained
by the reaction of Me2Si(NtBu)2Sn with tetrakis(triphenyphosphine)palladium or by the reaction of Me2Si(NtBu)2Ge
with RhCl(PPh3)3. In the first case Ph3PPd[Sn(NtBu)2SiMe2]3PdPPh3 (rhombohedral, space group R3c, a ) b )
21.397(12) Å, c ) 57.01(5) Å, R ) â ) 90°, γ ) 120°, Z ) 12) is formed and is characterized by X-ray techniques
to be composed of a central PdSn3Pd trigonal bipyramid with the tin atoms occupying the equatorial positions
(Pd-Sn ) 2.702(5) Å). In the second reaction all the triphenylphosphine ligands are replaced from rhodium and
Rh[Ge(NtBu)2SiMe2]4Cl is formed (monoclinic, space group P21/n, a ) 12.164(2) Å, b ) 23.625(5) Å, c )
24.128(5) Å, â ) 102.74(3)°, Z ) 4). The central core of this molecule is made up of a rhodium atom which is
almost square planarly coordinated by the germanium atoms, two of which are bridged by chlorine (mean Ge-
Rh ) 2.355 Å).
Introduction
From these findings it seemed worthwhile to have a closer
look at the ligating properties of the bis(amino)stannylene 1 Vs
simple transition metal halides of the type MX2. These metal
halides could act either as simple acceptors Via their metal atoms
or as a combined acid-base system. Using the simple Pearson’s
hard and soft acid rule,4 we should get N f M interactions
with small cations and Sn f M interactions with bigger and
heavier transition metals. In order to test these predictions, we
chose the following series: CrCl2, FeCl2, CoCl2, NiCl2, ZnCl2,
NiBr2, ZnBr2 as well as PdCl2 and PtCl2 in the nickel group.
During these investigations we also had a look at the reaction
of Ni[Sn(NtBu)2SiMe2]4 with Br2, as will become evident from
the results obtained at this stage. To conclude our survey we
have also included the reaction of 1 with Pd[PPh3]4 and of Me2-
Si(NtBu)2Ge with [Rh(PPh3]3]Cl as the clusters formed in these
reactions could have differences from or similarities with the
cluster compounds obtained from the simple reactions of 1 with
MX2.
The bis(amino)stannylene Me2Si(NtBu)2Sn (1) can behave
as an efficient donor to transition metals, which was demon-
strated by the synthesis and characterization of the complexes
Rh[Sn(NtBu)2SiMe2]5Cl1 or Ni[Sn(NtBu)2SiMe2]4.2 In both
compounds, the central transition metal is coordinated by five
or four tin atoms, the tin(II) atom acting as an electron donor
Via its lone pair. On the other hand, we have noticed that the
whole atom arrangement N2Sn in 1 may act as a tridentate ligand
toward metal halides, Me2Si(NtBu)2Sn‚(SnCl)+SnCl3- being a
good example.3 In this case the two nitrogen atoms of the ring
compound 1 act as donors toward the tin atom of the SnCl+
unit while the tin atom of 1 is coordinated to the chlorine of
SnCl+ (displaying electron acceptor properties).
X Abstract published in AdVance ACS Abstracts, May 15, 1996.
(1) Veith, M.; Stahl, L.; Huch, V. Inorg. Chem. 1989, 28, 3278.
(2) Veith, M.; Stahl, L.; Huch, V. J. Chem. Soc., Chem. Commun. 1990,
359.
(3) Veith, M.; Huch, V.; Lisowsky, R.; Hobein, P. Z. Anorg. Allg. Chem.
1989, 569, 43.
(4) Pearson, R. G. Coord. Chem. ReV. 1990, 100, 403.
S0020-1669(96)00007-9 CCC: $12.00 © 1996 American Chemical Society

Formation of Metal Clusters
Inorganic Chemistry, Vol. 35, No. 13, 1996 3849
Table 1. Crystallographic Data for 4, 5, 7, 8, 10, 11
4
5
7
8
10
11
formula
C20H48Cl4Co2N4Si2Sn2 C20H48Cl4N4Si2Sn2Zn2 C40H96Br2N8NiSi4Sn4‚ C40H96Cl2N8PdSi4Sn4‚ C40H96ClGe4N8RhSi4‚ C66H102N6P2Pd2Si3Sn3
0.5C6H6
1533.95
0.5C6H6
1492.83
C7H8
1322.46
12.164(2)
23.625(5))
24.128(5)
90
102.74(3)
90
6763(2)
4
fw.
a, Å
b, Å
c, Å
R ,deg
â , deg
γ , deg
V, Å3
Z
897.86
8.620(9)
9.160(9)
12.280(9)
101.2(1)
97.6(1)
105.9(1)
897(2)
910.75
8.156(9)
16.835(12)
13.206(9)
90
94.27(6)
90
1808(3)
2
1694.62
21.397(12)
21.397(12)
57.01(5)
90
90
120
22605(26)
12
43.86(4)
43.86(4)
14.32(2)
90
90
90
43.99(4)
43.99(4)
14.318(14)
90
90
90
27553(50)
16
27707(45)
16
1
space group P1h
P21/c
1.673
3.05
I41/a
1.441
2.96
I41/a
1.394
1.85
P21/c
1.299
2.140
R3c
1.494
1.579
d
calc, g/cm-3 1.663
µ(Mo KR)b, 2.67
mm-1
no. of reflcns 1673
no. of params 155
3164
155
5857
344
9209
456
8844
538
3985
494
Iobs > nσ
largest diff.
peak and
hole, e Å-3
R1
2
2
2
2
2
2
0.904; -1.265
0.657; -0.438
0.757; -0.574
0.877; -0.493
0.689; -0.323
0.740; -0.935
0.037
0.099
0.043
0.105
0.090
0.157
0.045
0.127
0.033
0.083
0.038
0.093
a
wR2
2
2
2
a wR2 ) (∑w(Fo - Fc2)2/∑w(Fo )2)1/2; w ) 1/[σ2(Fo ) + (aP)2 + bP + d + e sin θ]; P ) (Fo + 2Fc2)/3. b λ ) 0.71073 Å.
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg)
for 4 and 5
Experimental Section
All manipulations were done on a modified Schlenk-type vacuum
Compound 4
line, under an atmosphere of prepurified nitrogen gas. The NMR (1H,
Sn-N(1)
Sn-Cl(1)
Co-N(2)
Co-Cl(1)
Co-Cl(2)
mean:
2.165(6)
2.606(4)
2.156(6)
2.365(3)
2.379(3)
Co-Cl(2)#1
Sn-N(2)
Co-N(1)
Si-N(1)
2.337(5)
2.195(5)
2.342(5)
1.752(6)
1.765(5)
13C, 31P, 119Sn, 195Pt) spectra were recorded on Bruker AC 200 and
AM 400 instruments, using benzene-d6 as the lock solvent. Proton
and carbon NMR spectra are referenced relative to TMS, and the 119Sn
and 195Pt spectra, to tetramethyltin and potassium hexachloroplatinate,
respectively. The phosphorus signals are given relative to P(OMe)3 at
0.00 ppm. Mass spectra were measured with a Finnigan MAT 90
instrument, operating in either the EI (70 eV) or CI (methane) mode.
Elemental analyses (C, H, N) were performed by Beller, Go¨ttingen,
Germany. Melting points (uncorrected) were determined by sealing
single crystals of the compounds under an inert atmosphere inside
melting point capillaries. The data sets for the single-crystal X-ray
studies were collected on a fully automated Siemens/Stoe AED2 four-
circle diffractometer. All calculations were performed on a Digital
Corporation VAX system, with the help of SHELXS 86, SHELXL 93
and SHELXTL-PLUS programms. The specific data of the crystals
and the refinements are collected in Table 1, some results of the
structure determinations are assembled in Table 2-5.
Si-N(2)
C-N
1.487(9)
C-C
1.53(1)
N(1)-Sn-N(2)
N(1)-Sn-Cl(1)
N(2)-Sn-Cl(1)
N(2)-Co-Cl(2)#1
N(2)-Co-N(1)
Cl(2)#1-Co-N(1)
N(2)-Co-Cl(1)
67.3(2)
Sn-N(1)-Co
C(1)-N(2)-Si
C(1)-N(2)-Co
Si-N(2)-Co
C(1)-N(2)-Sn
Si-N(2)-Sn
Co-N(2)-Sn
81.7(2)
128.2(4)
127.6(4)
87.9(2)
122.4(4)
92.8(2)
85.4(2)
94.2(2)
131.0(4)
82.5(2)
160.6(2)
89.3(2)
87.6(2)
149.8(2)
64.8(2)
97.3(2)
95.1(2)
Cl(2)#1-Co-Cl(1) 110.24(14) Si-N(1)-Sn
C(2)-N(1)-Si
C(2)-N(1)-Sn
N(1)-Co-Cl(1)
N(2)-Co-Cl(2)
Cl(2)#1-Co-Cl(2)
N(1)-Si-N(2)
130.0(4)
122.5(4)
91.3(2)
C(2)-N(1)-Co
Si-N(1)-Co
N(1)-Co-Cl(2)
103.9(2)
85.40(13) Co-Cl(1)-Sn
86.8(3) Co#1-Cl(2)-Co
Cl(1)-Co-Cl(2) 105.75(13)
The graphical representations of the molecular structures were drawn
by using either the SCHAKAL program or the XP routine of the
SHELXTL-PLUS package. The Ge(II) and Sn(II) compounds Me2-
Si(NtBu)2Ge and Me2Si(NtBu)2Sn were prepared according to literature
methods.5,6
72.68(10)
94.60(13)
Compound 5
1.729(7)
Si-N(2)
Si-N(1)
N(1)-C(1)
N(2)-C(2)
Sn-N(2)
Sn-N(1)
Sn-Cl(2)
Zn-N(1)
Zn-Cl(2)
Zn-Cl(1)
Zn-Cl(1)#1
2.791(3)
2.014(6)
2.309(3)
2.309(3)
2.367(3)
1.799(6)
1.514(9)
1.483(11)
2.033(7)
2.252(6)
General procedure for the reaction of transition metal halides with
the cyclic bis(amino)stannylene 1. To a suspension of 2.0 mmol of
anhydrous MX2 (CrCl2, FeCl2, CoCl2, NiCl2, NiBr2, ZnCl2, ZnBr2, PdCl2,
PtCl2), in 15 mL of toluene (benzene), was added a solution of 2.0 mL
(8.0 mmol) of Me2Si(NtBu)2Sn in 10 mL of toluene (benzene). In
each case the reaction mixture changed its color with exception of NiCl2
which gave no reaction, the components being recovered unchanged
even after refluxing for 10 days (NMR evidence). Most of the metal
halides dissolved within 30 min, and only NiBr2 and PtCl2 were heated
for 48 h at 40 °C and 30 min at 60 °C, respectively. Upon removal of
the solvent and excess of 1 in vacuo a colored solid remained. This
was taken up in a minimum amount of hexane and cooled to -20 °C.
The products crystallized from these solutions and could be easily
seperated.
N(2)-Sn-N(1)
N(2)-Sn-Cl(2)
N(1)-Sn-Cl(2)
N(1)-Zn-Cl(2)
N(1)-Zn-Cl(1)
Cl(2)-Zn-Cl(1)
N(1)-Zn-Cl(1)#1
Cl(2)-Zn-Cl(1)#1
Cl(1)-Zn-Cl(1)#1
N(2)-Si-N(1)
74.0(2)
94.7(2)
80.4(2)
Zn-Cl(2)-Sn
C(1)-N(1)-Si
C(1)-N(1)-Zn
Si-N(1)-Zn
C(1)-N(1)-Sn
Si-N(1)-Sn
Zn-N(1)-Sn
C(2)-N(2)-Si
C(2)-N(2)-Sn
Si-N(2)-Sn
78.19(8)
123.9(5)
112.4(4)
111.3(3)
115.1(4)
90.9(3)
98.5(2)
123.5(2)
116.72(10)
126.4(2)
102.44(11)
88.90(10)
94.2(3)
98.6(2)
131.6(6)
126.8(6)
100.8(3)
Cr2[Sn(NtBu)2SiMe2]2Cl4 (2): pale green, rod-shaped crystals; yield
0.63 g (72%); mp 140 °C dec; molecular weight (cryoscopic in
benzene) 843 g/mol; paramagnetic compound, 2.48 µB (Evans method).
Zn-Cl(1)-Zn#1
91.10(10)
UV-spectrum: λ (max) ) 709 nm (ꢀ ) 321). Anal. Calcd for C20H48-
Cl4Cr2N4Si2Sn2, 883.98 g/mol: C, 27.18; H, 5.47; N, 6.34; Sn, 26.85.
Found: C, 27.16, H, 5.51; N, 6.33; Sn, 24.57.
Fe2[Sn(NtBu)2SiMe2]2Cl4 (3): brown-yellow, rod-shaped crystals;
yield 0.70 g (79%); mp 125 °C dec; molecular weight (cryoscopic)
(5) Veith, M. Angew. Chem. 1975, 87, 287.; Angew. Chem., Int. Ed. Engl.
1975, 14, 263.
(6) Veith, M.; Grosser, M. Z. Naturforsch. 1982, 37B, 1375.

3850 Inorganic Chemistry, Vol. 35, No. 13, 1996
Veith et al.
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg)
of 7 and 8
Table 4. Selected Bond Lengths (Å) and Bond Angles (deg) of 10
Rh-Ge(2)
2.3366(9)
2.3368(7)
2.3711(7)
2.3756(8)
1.834(4)
1.839(4)
1.835(4)
1.835(4)
1.850(4)
1.854(4)
2.5944(14)
1.850(4)
1.851(4)
2.604(2)
1.727(4)
1.737(4)
Si(1)-C(11)
Si(2)-N(22)
Si(2)-N(21)
Si(2)-C(22)
Si(2)-C(21)
Si(3)-N(32)
Si(3)-N(31)
Si(3)-C(31)
Si(3)-C(32)
Si(4)-N(42)
Si(4)-N(41)
Si(4)-C(41)
Si(4)-C(42)
1.855(6)
1.727(4)
1.736(4)
1.851(6)
1.866(7)
1.723(4)
1.730(4)
1.868(6)
1.872(6)
1.720(5)
1.726(4)
1.868(6)
1.876(6)
Rh-Ge(1)
Compound 7
Rh-Ge(4)
Rh-Ge(3)
Sn(1)-N(1)
Sn(4)-Br(2)
Sn(3)-Ni
Si(1)-N(1)
Si(1)-N(2)
Si(2)-N(3)
Si(2)-N(4)
Sn(1)-N(2)
Sn(1)-Ni
1.99(2)
2.789(4)
2.467(4)
1.72(2)
1.75(2)
1.70(2)
1.75(2)
2.03(2)
2.460(4)
2.776(4)
2.459(4)
2.02(2)
Sn(3)-N(6)
Sn(4)-N(7)
Sn(3)-Br(2)
Si(3)-N(5)
Si(3)-N(6)
Sn(2)-Ni
Sn(2)-N(4)
Sn(2)-N(3)
Sn(2)-Br(1)
Sn(3)-N(5)
2.03(2)
2.02(2)
2.813(4)
1.70(2)
1.74(2)
2.466(4)
2.03(2)
2.03(3)
2.847(4)
2.00(2)
Ge(1)-N(12)
Ge(1)-N(11)
Ge(2)-N(21)
Ge(2)-N(22)
Ge(3)-N(32)
Ge(3)-N(31)
Ge(3)-Cl
Ge(4)-N(42)
Ge(4)-N(41)
Ge(4)-Cl
Si(1)-N(12)
Si(1)-N(11)
Sn(1)-Br(1)
Sn(4)-Ni
Sn(4)-N(8)
N(1)-Sn(1)-N(2)
N(1)-Sn(1)-Ni
N(2)-Sn(1)-Ni
N(1)-Sn(1)-Br(1)
76.5(9)
129.6(7)
143.2(7)
98.5(7)
N(6)-Sn(3)-Br(2)
Ni-Sn(3)-Br(2)
N(7)-Sn(4)-N(8)
N(7)-Sn(4)-Ni
N(8)-Sn(4)-Ni
99.2(6)
97.16(14)
74.0(9)
145.6(7)
130.9(6)
99.0(6)
Ge(2)-Rh-Ge(4)
Ge(1)-Rh-Ge(4)
Ge(2)-Rh-Ge(3)
Ge(1)-Rh-Ge(3)
Ge(4)-Rh-Ge(3)
92.10(3) Ge(3)-Cl-Ge(4)
77.34(4)
163.36(2) N(12)-Si(1)-N(11) 88.2(2)
161.34(2) N(12)-Si(1)-C(12) 114.8(3)
93.93(3) N(11)-Si(1)-C(12) 115.1(3)
86.37(3) N(12)-Si(1)-C(11) 113.9(3)
N(2)-Sn(1)-Br(1) 101.3(7)
Ni-Sn(1)-Br(1)
N(4)-Sn(2)-N(3)
N(4)-Sn(2)-Ni
N(3)-Sn(2)-Ni
N(4)-Sn(2)-Br(1)
N(3)-Sn(2)-Br(1)
Ni-Sn(2)-Br(1)
N(5)-Sn(3)-N(6)
N(5)-Sn(3)-Ni
N(6)-Sn(3)-Ni
N(5)-Sn(3)-Br(2)
99.51(14) N(7)-Sn(4)-Br(2)
76.8(9)
127.5(7)
149.2(7)
96.9(6)
N(8)-Sn(4)-Br(2) 101.2(6)
N(12)-Ge(1)-N(11) 82.1(2)
N(11)-Si(1)-C(11) 114.6(3)
Ni-Sn(4)-Br(2)
Sn(4)-Ni-Sn(1)
Sn(4)-Ni-Sn(2)
Sn(1)-Ni-Sn(2)
97.98(14)
162.9(2)
93.9(2)
87.7(2)
88.8(2)
N(12)-Ge(1)-Rh
N(11)-Ge(1)-Rh
130.57(13) C(12)-Si(1)-C(11) 109.1(3)
147.37(13) N(22)-Si(2)-N(21) 88.2(2)
N(21)-Ge(2)-N(22) 82.1(2)
N(22)-Si(2)-C(22) 115.2(3)
97.7(7)
N(21)-Ge(2)-Rh
N(22)-Ge(2)-Rh
147.86(13) N(21)-Si(2)-C(22) 114.5(3))
129.86(13) N(21)-Si(2)-C(21) 114.5(3)
97.48(14) Sn(4)-Ni-Sn(3)
75.6(8)
142.0(6)
134.4(6)
99.8(6)
Sn(1)-Ni-Sn(3)
Sn(2)-Ni-Sn(3)
Sn(1)-Br(1)-Sn(2)
Sn(4)-Br(2)-Sn(3)
94.3(2)
N(32)-Ge(3)-N(31) 81.4(2)
C(22)-Si(2)-C(21) 109.2(4)
163.7(2)
74.72(12)
75.98(12)
N(32)-Ge(3)-Rh
N(31)-Ge(3)-Rh
N(32)-Ge(3)-Cl
N(31)-Ge(3)-Cl
Rh-Ge(3)-Cl
137.24(13) N(32)-Si(3)-N(31) 88.7(2)
132.95(12) N(32)-Si(3)-C(31) 116.0(3)
102.34(14) N(31)-Si(3)-C(31) 115.2(3)
96.47(12) N(32)-Si(3)-C(32) 114.4(3)
98.23(4) N(31)-Si(3)-C(32) 115.2(3)
Compound 8
Pd-Sn(1)
2.542(2)
2.542(2)
2.544(2)
2.547(2)
2.043(8)
2.045(8)
2.617(3)
2.027(8)
2.028(8)
2.661(3)
2.023(9)
2.033(9)
2.699(3)
Sn(4)-Cl(1)
Sn(4)-N(7)
Sn(4)-N(8)
Si(1)-N(1)
Si(1)-N(2)
Si(2)-N(3)
Si(2)-N(4)
Si(3)-N(5)
Si(3)-N(6)
Si(4)-N(7)
Si(4)-N(8)
2.652(3)
2.018(8)
2.025(8)
1.733(9)
1.753(10)
1.733(9)
1.740(9)
1.727(11)
1.731(10)
1.732(9)
1.734(9)
Pd-Sn(3)
N(42)-Ge(4)-N(41) 81.4(2)
C(31)-Si(3)-C(32) 106.9(3)
Pd-Sn(4)
Pd-Sn(2)
N(42)-Ge(4)-Rh
N(41)-Ge(4)-Rh
N(42)-Ge(4)-Cl
N(41)-Ge(4)-Cl
Rh-Ge(4)-Cl
134.02(14) N(42)-Si(4)-N(41) 88.9(2)
136.09(13) N(42)-Si(4)-C(41) 115.4(3)
96.39(13) N(41)-Si(4)-C(41) 113.6(3)
102.86(13) N(42)-Si(4)-C(42) 115.4(3)
98.07(4) N(41)-Si(4)-C(42) 116.0(3)
Sn(1)-N(1)
Sn(1)-N(2)
Sn(1)-Cl(2)
Sn(2)-N(4)
Sn(2)-N(3)
Sn(2)-Cl(1)
Sn(3)-N(5)
Sn(3)-N(6)
Sn(3)-Cl(2)
Zn2[Sn(NtBu)2SiMe2]2Cl4 (5): pale yellow, prismatic crystals; yield
0.76 g (83%); mp 130 °C dec; molecular weight (cryoscopic) 892 g/mol.
1H-NMR (benzene): 0.20 (s, 1.0, Si-CH3), 0.62 (s, 1.0, Si-CH3), 1.20
(s, 6.0, C-CH3) ppm. MM (spectrum): peak of highest intensity and
mass: 873 (C20H48N435Cl3118Sn264Zn68Zn, M - Cl). Anal. Calcd for
C20H48Cl4N4Si2Sn2Zn2, 910.75 g/mol: C, 26.38; H, 5.31; N, 6.15; Sn,
26.06. Found: C, 26.39, H, 5.31; N, 6.20; Sn, 26.30.
Zn[Sn(NtBu)2SiMe2]Br2 (6): pale yellow, rod-shaped crystals; yield
0.88 g (81%); mp 125 °C dec; molecular weight (cryoscopic) 558 g/mol.
1H-NMR (benzene): -0.04 (s, 1.0, Si-CH3), 0.52 (s, 1.0, Si-CH3),
1.09 (s, 6.0, C-CH3) ppm. Anal. Calcd for C10H24Br2N2SiSnZn,
544.28 g/mol: C, 22.06; H, 4.44; N, 5.15; Sn, 21.81. Found: C, 22.16,
H, 4.50; N, 5.12; Sn, 20.70.
Ni[Sn(NtBu)2SiMe2]4Br2 (7): dark red, rod-shaped crystals; yield
2.34 g (78%); mp 150 °C dec; molecular weight (cryoscopic) 1420
g/mol. 1H-NMR (benzene): 0.42 (s, 1.0, Si-CH3), 1.45 (s, 3.0,
C-CH3) ppm. 13C-NMR (benzene): 7.23 (s, 1.0, Si-CH3); 36.72
(3JSn-C ) 26.7 Hz, 15%, C-CH3); 53.34 (s, 1.0, C-CH3) ppm. 29Si-
NMR: 8.77 ppm. Small paramagnetism: 0.2 µB. UV-spectrum: λ
(max) ) 380 nm (sh, ꢀ ) 4147), 333 nm (ꢀ ) 8955). Anal. Calcd for
C43H99Br2N8NiSi4Sn4 (7‚0.5 C6H6), 1533.95 g/mol: C, 33.67; H, 6.51;
N, 7.30; Sn, 30.96; Ni, 3.83. Found: C, 32.53; H, 7.13; N, 7.12; Sn,
29.98; Ni, 3.18.
Pd[Sn(NtBu)2SiMe2]4Cl2 (8): dark red, rod-shaped crystals; yield
2.09 g (72%); mp 290 °C dec; molecular weight (cryoscopic) 1452
g/mol, 1H-NMR (benzene): 0.44 (s, 1.0, Si-CH3), 1.41 (s, 3.0, C-CH3)
ppm. 13C-NMR (benzene): 6.99 (s, 1.0, Si-CH3), 7.83 (s, 1.0, Si-CH3),
36.64 (s, 6.0, C-CH3), 53.03 (s, 2.0, C-CH3) ppm. 119Sn-NMR
(benzene): 55.85 (s) ppm. Anal. Calcd for C43H99Cl2N8PdSi4Sn4 (8‚0.5
C6H6), 1492.83 g/mol: C, 34.60; H, 6.68; N, 7.51. Found: C, 33.68;
H, 6.57; N, 7.26.
N(3)-Sn(2)-Cl(1)
Pd-Sn(2)-Cl(1)
N(5)-Sn(3)-N(6)
N(5)-Sn(3)-Pd
N(6)-Sn(3)-Pd
N(5)-Sn(3)-Cl(2)
N(6)-Sn(3)-Cl(2)
Pd-Sn(3)-Cl(2)
N(7)-Sn(4)-N(8)
N(7)-Sn(4)-Pd
N(8)-Sn(4)-Pd
N(7)-Sn(4)-Cl(1)
N(8)-Sn(4)-Cl(1)
Pd-Sn(4)-Cl(1)
Sn(4)-Cl(1)-Sn(2)
Sn(1)-Cl(2)-Sn(3)
102.6(3)
95.63(9)
76.5(4)
149.4(3)
126.5(3)
100.9(3)
98.4(3)
95.48(9)
76.3(3)
145.2(2)
129.0(2)
101.6(2)
102.1(2)
95.91(9)
Sn(1)-Pd-Sn(3)
Sn(1)-Pd-Sn(4)
Sn(3)-Pd-Sn(4)
Sn(1)-Pd-Sn(2)
Sn(3)-Pd-Sn(2)
Sn(4)-Pd-Sn(2)
N(1)-Sn(1)-N(2)
N(1)-Sn(1)-Pd
N(2)-Sn(1)-Pd
85.52(8)
164.45(4)
96.31(8)
95.76(7)
165.30(4)
86.38(7)
77.0(4)
128.0(3)
143.5(3)
N(1)-Sn(1)-Cl(2) 100.8(3)
N(2)-Sn(1)-Cl(2) 103.4(3)
Pd-Sn(1)-Cl(2)
N(4)-Sn(4)-N(3)
N(4)-Sn(2)-Pd
97.54(9)
76.5(3)
132.6(2)
141.9(2)
81.96(10) N(3)-Sn(2)-Pd
80.97(10) N(4)-Sn(2)-Cl(1) 100.9(3)
874 g/mol; paramagnetic compound, 5.46 µB. Crystal data (single-
crystal X-ray diffraction): triclinic, a ) 8.622(7), b ) 9.158(8), c )
12.353(8) Å; R ) 101.8(1), â ) 96.9(1), γ ) 105.9(1)°. Anal. Calcd
for C20H48Cl4Fe2N4Si2Sn2, 891.68 g/mol: C, 26.94; H, 5.43; N, 6.28;
Sn, 26.62. Found: C, 27.03; H, 5.50; N, 6.33; Sn, 25.81.
Co2[Sn(NtBu)2SiMe2]2Cl4 (4): dark blue, rod-shaped crystals; yield
0.83 g (92%); mp 80 °C dec; molecular weight (cryoscopic) 861 g/mol.
MM (spectrum): peak of highest intensity and mass: 881(C19H45-
35Cl337ClCoN4Si2118Sn2, M - 15). Paramagnetic compound: 5.0 µB.
UV-spectrum: λ(max) ) 707 nm (ꢀ ) 289). Anal. Calcd for C20H48-
Cl4Co2N4Si2Sn2, 897.86 g/mol: C, 26.75; H, 5.39; N, 6.24; Co, 13.13.
Found: C, 27.89; H, 5.57; N, 6.19; Co, 12.96.
Pt[Sn(NtBu)2SiMe2]4Cl2 (9): orange-yellow crystals; yield 2.31 g
(75%); mp 320 °C dec; molecular weight (cryoscopic) 1577 g/mol.

Formation of Metal Clusters
Inorganic Chemistry, Vol. 35, No. 13, 1996 3851
Table 5. Selected Bond Lengths (Å) and Bond Angles (deg) of 11
was reduced to half of its volume by condensation in Vacuo. Crystal-
lization at -20 °C yielded 1.11 g (95%) of dark red prisms.
Pd(3)-Pd(4)
Pd(1)-Pd(2)
Pd(1)-P(1)
Pd(1)-Sn(1)
Pd(2)-P(2)
Pd(2)-Sn(1)
Sn(1)-N(2)
Sn(1)-N(1)
Pd(3)-P(3)
Pd(3)-Sn(2)
Pd(4)-P(4)
Pd(4)-Sn(2)
Sn(2)-N(3)
2.583
2.597
Sn(2)-N(4)
P(1)-C(21)
P(2)-C(27)
P(3)-C(33)
P(4)-C(39)
Si(1)-N(1)
Si(1)-N(2)
Si(1)-C(12)
Si(1)-C(11)
Si(2)-N(3)
Si(2)-N(4)
Si(2)-C(20)
Si(2)-C(19)
2.082(9)
Rh[Ge(NtBu)2SiMe2]4Cl‚C7H8: mp 285 °C dec; molecular weight
(cryoscopic) 1280 g/mol. MM (spectrum): highest mass 1230,
calculated for C40H96ClGe4N8RhSi4 (M - C7H8+). 1H-NMR (ben-
zene): 0.43 (s, 1.0, Si-CH3), 1.50 (s, 3.0, C-CH3)ppm. 13C-NMR:
5.92 (s, 2.0, Si-CH3), 35.65 (s, 6.0, C-CH3), 53.06 (s, 2.0, C-CH3)
ppm. 15N-NMR: -248.97 ppm, 29Si-NMR: 11.75 ppm. Anal. Calcd
for C47H104ClGe4N8RhSi4, 1322.47 g/mol: C, 42.68; H, 7.92; N, 8.47;
Cl, 2.7. Found: C, 40.60; H, 7.91; N, 7.55; Cl, 3.2.
Synthesis of Pd2[Sn(NtBu)2SiMe2]3(PPh3)2. In a 100 mL two
necked flask equipped with a stirring bar, 0.441 mmol of Pd(PPh3)4
was dissolved in 20 mL of toluene to give a yellow-brown solution.
Addition of 6 mL 0.44 M Sn(NtBu)2SiMe2 in toluene solution resulted
in a rapid darkening of the reaction mixture. The solution was then
stirred for 16 h at 50-60 °C. Upon removal of the solvent and excess
stannylene, beautifully developed dark red crystals were formed on
the walls of the flask. These crystals were redissolved in a minimum
amount of toluene and the ensuing solution was cooled to 0 °C. After
3 days a large crop (0.623 g, 82%) of cherry red block-shaped crystals
could be obtained.
1.830(11)
1.841(12)
1.823(10)
1.824(11)
1.720(10)
1.728(10)
1.861(14)
1.870(12)
1.694(10)
1.738(10)
1.871(14)
1.874(14)
2.290(5)
2.697(2)
2.298(5)
2.700(2)
2.050(9)
2.081(9)
2.288(5)
2.725(2)
2.292(5)
2.688(2)
2.074(9)
P(1)-Pd(1)-Sn(1)
118.71(4) C(21)#1-P(1)-C(21) 102.8(4)
115.5(3)
118.83(4) C(27)-P(2)-C(27)#1 101.8(5)
Sn(1)#1-Pd(2)-Sn(1) 98.70(5) C(27)-P(2)-Pd(2) 116.4(4)
74.5(4) C(33)#1-P(3)-C(33) 103.1(4)
146.1(3) C(33)-P(3)-Pd(3) 115.3(3)
Sn(1)-Pd(1)-Sn(1)#1 98.85(5) C(21)-P(1)-Pd(1)
P(2)-Pd(2)-Sn(1)
N(2)-Sn(1)-N(1)
N(2)-Sn(1)-Pd(1)
N(1)-Sn(1)-Pd(1)
N(2)-Sn(1)-Pd(2)
N(1)-Sn(1)-Pd(2)
Pd(1)-Sn(1)-Pd(2)
P(3)-Pd(3)-Sn(2)
Sn(2)-Pd(3)-Sn(2)#1 98.22(5) N(1)-Si(1)-C(11)
P(4)-Pd(4)-Sn(2) 117.74(4) N(2)-Si(1)-C(11)
Sn(2)#1-Pd(4)-Sn(2) 100.08(5) C(12)-Si(1)-C(11)
N(3)-Sn(2)-N(4)
N(3)-Sn(2)-Pd(4)
N(4)-Sn(2)-Pd(4)
N(3)-Sn(2)-Pd(3)
N(4)-Sn(2)-Pd(3)
Pd(4)-Sn(2)-Pd(3)
121.0(3) C(39)-P(4)-C(39)#1 103.2(4)
126.0(3) C(39)-P(4)-Pd(4)
148.5(3) N(1)-Si(1)-N(2)
57.54(6) N(1)-Si(1)-C(12)
119.20(4) N(2)-Si(1)-C(12)
115.2(4)
93.0(4)
Pd2[Sn(NtBu)2SiMe2]3(PPh3)2: mp 275 °C. 1H-NMR (benzene):
0.57 (s, 18, Si-CH3), 1.125 (s, 54, C-CH3), 6.90-7.50 (m, 30,
115.8(6)
113.6(6)
112.8(6)
114.9(6)
106.8(6)
93.8(4)
31
117/
aromatic, partially observed) ppm. P-NMR (THF): -109.9 ppm (J
31
Sn-
119
) 70 Hz, 32%). Anal. Calcd for C66H102N6P2Pd2Si3Sn3,
P
1694.76 g/mol: C, 46.78; H, 6.07; N, 4.96. Found: C, 46.98; H, 5.82;
N, 4.85.
74.1(4) N(3)-Si(2)-N(4)
150.9(3) N(3)-Si(2)-C(20)
126.5(3) N(4)-Si(2)-C(20)
121.8(3) N(3)-Si(2)-C(19)
142.4(3) N(4)-Si(2)-C(19)
56.94(6)
113.7(6)
112.9(6)
113.2(6)
116.3(6)
Results and Discussion
Syntheses. The reactions between transition metal dihalides
and the cyclic bis(amino)stannylene 1 can be separated into two
distinct classes. Chromium dichloride, iron dichloride, cobalt
dichloride, zinc dichloride and zinc dibromide react with 1 equiv
of stannylene, whereas nickel dibromide, palladium dichloride,
and platinum dichloride react with 4 equiv of 1 (eq 1 and 2).
1H-NMR (benzene): 0.403 (s, 1.0, Si-CH3), 0.480 (s, 1.0, Si-CH3),
1.415 (s, 6.0, C-CH3) ppm. 13C-NMR (benzene): 6.80 (s, 1.0, Si-
CH3), 7.78 (s, 1.0, Si-CH3), 36.65 (s, 6.0, C-CH3), 52.78 (s, 2.0,
C-CH3) ppm. 119Sn-NMR (benzene): 7.17ppm (JPt-Sn ) 14017 Hz,
195
117
33%).
J
Pt-NMR (benzene): -3456.2 ppm (J
) 13401 Hz,
Sn-Pt
119
Sn-Pt ) 14037 Hz). Anal. Calcd for C40H96Cl2N8PtSi4Sn4, 1542.43
g/mol: C, 31.15; H, 6.27; N, 7.56. Found: C, 31.55; H, 6.27; N, 6.89.
Reaction of Ni[Sn(NtBu)2SiMe2]4 with Br2 and PhMe3NBr3. A
0.67 g (0.5 mmol) sample of Ni[Sn(NtBu)2SiMe2]4 was dissolved
(1)
2
in 10 mL of hexane to which an equimolar solution of Br2 or
phenyltrimethylammonium tribromide7 in 20 mL of hexane was dropped
at -78 °C. The reaction mixture turned dark red. After separation of
some solid material, which contained NiBr2 and SnBr2 as found by
X-ray powder diffraction, partial removal of hexane in Vacuo yielded
a concentrated solution from which crystals were obtained at -30 °C.
Within these crystals two different species could easily be recognized:
one species was dark red and rod-shaped, and the other one was pale
yellow. The dark red crystals were identified to be Ni[Sn(NtBu)2SiMe2]4-
Br2 from 1H-NMR in benzene and from the X-ray pattern of the single
crystal; yield 20 mg (2.8%). The pale yellow crystals were identified
as Me2Si(NtBu)2SnBr2 (0.27 g, 28%). From the remaining solution
the solvent was completely removed and replaced by 1.5 mL of toluene.
After crystallization at -30 °C, 0.30 g (29%) of Me2Si(NtBu)2Sn-
(NtBu)2SiMe2 was obtained and identified by physical and spectroscopic
means.5
(2)
Me2Si(NtBu)2SnBr2: pale yellow crystals; mp 160 °C dec. 1H-NMR
(benzene): 0.46 (s, 1.0, Si-CH3), 1.43 (s, 3.0, C-CH3); 13C-NMR:
7.847 (s, 6H, Si-CH3), 37.083 (s, 18H, C-CH3), δ ) 54.184 (s, 2H,
C-CH3) ppm. Anal. Calcd for C10H24Br2N2SiSn, 478.92 g/mol: C,
25.08; H, 5.05; N, 5.85. Found: C, 25.37; H, 4.98; N, 5.91.
No reaction could be observed between nickel dichloride and
the stannylene 1. In all other cases the suspension of the metal
dihalide in the aromatic solvent cleared up when 1 was added
and the solution changed its color. Compounds 2-9 could be
isolated by crystallization in high yields. By cryoscopic
molecular weight determination in benzene it could be shown
that the molecules 2-5 were dimeric whereas 6-9 were found
to be monomeric in benzene. Compounds 2-4 are paramag-
netic and no NMR spectra could be obtained for these
Synthesis of Rh[Ge(NtBu)2SiMe2]4Cl. To a solution of 0.82 g (0.89
mmol) of Rh(PPh3)3Cl8 in 50 mL of toluene was added 0.88 mL (3.54
mmol) of Me2Si(NtBu)2Ge dropwise, and the solution was stirred for
2 h at room temperature and 6 h at 80 °C. After filtration the solution
(7) Marquet, A.; Jacques, J. Tetrahedron Lett. 1959, 9, 24.
(8) Young, J. F.; Osborne, J. A.; Jardine, F. H.; Wilkinson, G. J. J. Chem.
Soc., Chem. Commun. 1965, 131.

3852 Inorganic Chemistry, Vol. 35, No. 13, 1996
Veith et al.
molecules; we used Evans’ NMR-method9 to determine the
susceptibility in solution from which the following µeff (magnetic
moments) could be calculated (the values are related to the
monomeric unit): 2, 2.5 µB; 3, 5.5 µB; 4, 5.0 µB. The values
for 3 and 4 compare well with those for the high spin d6 and d7
configuration in trigonal bipyramidal or octahedral environments
(Fe2+; 5.06-5.26;10,11 Co2+, 4.5-4.812-14 ), while the value for
2 seems to indicate a low spin complex (for the facile transition
of high spin Cr[d4] to low spin see ref 15. ). Unfortunately we
could get no single crystals of compound 2 suitable for X-ray
diffraction analysis. As expected the compounds 5 and 6 show
no paramagnetism (Zn d10), and the 1H NMR spectra have two
different resonance lines for the dimethylsilyl groups. This may
be taken as a hint that the Me2Si(NtBu)2Sn unit is asymmetri-
cally coordinated to the ZnCl2 or ZnBr2 parts of the molecule.
In each case the tert-butyl groups show up as a common
resonance. This is in contrast to the crystal structure of 5 which
displays two chemically different tert-butyl groups (see next
section). We may conclude that either the molecules show
fluxional behavior in solution or the structures in solutions are
different from the solid state.
From the compounds 7-9 very simple NMR spectra can be
obtained, consistent with a high symmetry of these compounds
in solution (the Me2Si(NtBu)2Sn part has a 2-fold symmetry
and all four ligands are equivalent on the NMR time scale).
As we had no problems in obtaining the NMR spectra, the
paramagnetism for these d8 systems is expected to be zero or
very small. We were able to find a very small µeff value for 7
(0.2 µB) by the Evans method. This value, which is different
from zero, is in accord with the crystal structure determination
of 7 and 8: in each case the transition metal is not in a perfect
square planar arrangement, but deviates by a small amount (see
next section). The high coupling constants JSn-Pt ≈ 14 000 Hz
in the Sn and Pt spectra indicate direct Sn-Pt bonding.
In order to test if the compound 7 may also be produced by
direct interaction of the nickel(0) complex Ni[Sn(NtBu)2SiMe2]4
with the corresponding halogen or with PhMe3NBr3, we have
performed the reactions in eq 3 in hexane solutions. The main
be obtained by crystallization from the solution. Carrying out
the reactions in eq 3 at low temperatures does not considerably
influence the ratio of the products. It is nevertheless remarkable
that to a small extent the starting cluster compound can be
oxidized to 7 without decompostion.
In order to establish that Me2Si(NtBu)2Ge may also coordinate
efficiently to transition metals in the place of Me2Si(NtBu)2Sn,
we have reacted, in analogy to previous experiments,1 Wilkin-
son’s catalyst Rh(PPh3)3Cl with a bis(amino)germylene (eq 4).
Rh(PPh3)3Cl + 4Me2Si(NtBu)2Ge f
[Me Si(NtBu) Ge] RhCl
+ 3PPh3 (4)
2
2
4
10
The reaction proceeds smoothly and the triphenylphosphine
ligands at rhodium are completely displaced. To our surprise,
not five carbene analogues are coordinated to rhodium as in
the case of the stannylene,1 but only four. In solution the
structure of 10 seems to be highly symmetrical as may be
concluded from the NMR spectra as no differences are found
between the bis(amino)germylene ligands which have no
interaction with chlorine and those which coordinate rhodium
and chlorine at the same time (compare with the crystal structure
of 10 in the next section). As a complete chloride dissociation
in benzene seems to be highly improbable, we may attribute
this higher symmetry of 10 in solution to fast chlorine exchanges
between the molecules or to fluxional processes within 10.
Another attempt to displace the phosphine ligands at a
transition metal (this time in the oxidation state 0) by carbene
like stannylenes was performed with Pd(PPh3)4 (eq 5). In the
Pd(PPh3)4 + 3/2Sn(NtBu)2SiMe2 f
1/2 Ph3PPd[Sn(NtBu)2SiMe2]3PdPPh3
+ 3PPh3 (5)
11
product 11, which is obtained in high yield, a triphenylphosphine
ligand is still present. Three of the phosphine ligands are thus
replaced by stannylenes, but as will become evident from the
X-ray structure determination (see below) all tin atoms are
involved in bridging the two palladium atoms. The NMR
spectra are consistent with the solid structure of compound 11
and have a precedence with the platinum compound Ph3PPt(Sn
acac)3PtPPh3, described by Stobart et. al. in 1982.17
[Me2Si(NtBu)2Sn]4Ni + X2
8
-NiBr2, -SnBr2
xMe2Si(NtBu)2Sn(NtBu)2SiMe2 +
y[Me2Si(NtBu)2Sn]4NiBr2
+ zMe2Si(NtBu)2SnBr2 (3)
7
Structures of the Compounds. X-ray structure determina-
tions on single crystals of 4, 5, 7, 8, 10, and 11 have been
performed (see Experimental Section). In Figures 1 and 2 the
molecular structures of 4 and 5 are depicted, while some
important molecular dimensions of these molecules are as-
sembled in Table 2. Molecule 3 seems to be isostructural to 4
as may be deduced from the cell parameters and the crystal
lattice symmetry. The common feature of these two molecules
is a centrosymmetric four-membered dimetal dihalogen cycle.
The bond distances and angles within these roughly square
planar rings are similar, the distortion in 4 being rhomboidal
and in 5 rectangular. This four membered central unit is
connected through Co to a polycyclic CoN2ClSiSn unit in 4
whereas in 5 Zn is a spiro center to another four membered
ZnClNSn ring which shares an edge with an SnN2Si cycle. The
SiN2SnCoCl assembly in 4 resembles a highly symmetric
twistane and is isostructural to the SiN2Sn2Cl cage found in
X2 ) Br2, PhNMe3Br3
products of these reactions are the well-known spiro tetrakis-
(amino)stannane Me2Si(NtBu)2Sn(NtBu)2SiMe25 and the bis(ami-
no)tin dibromide Me2Si(NtBu)2SnBr2, along with NiBr2 and
SnBr2, which precipitate from the solution and which are
identified as components of the solid residue by X-ray powder
diffraction. The nickel-tin cluster is thus completely degraded
to its oxidation products. The spiro compound is known to be
formed from Me2Si(NtBu)2SnX2 and free Sn(NtBu)2SiMe2.16
Besides these main products 7 is formed in low yield and could
(9) Evans, D. F. J. Chem. Soc. 1959, 2003.
(10) Ciampolini, M.; Nardi, N. Inorg. Chem. 1967, 6, 445.
(11) Fallon, G. D.; Nichols, P. J.; West, B. O. J. Chem. Soc., Dalton Trans.
1986, 2271.
(12) Kaden, T.; Hohnquist, B.; Vallee, B. L. Inorg. Chem. 1974, 13, 2585.
(13) Fox, D. B.; Hall, J. R.; Plowman, R. A. Austr. J. Chem. 1965, 18,
691.
(14) Che, C. M.; Mak S.-T.; Mak, T. C. W. Inorg. Chem. 1986, 25, 4705.
(15) Reed, C. A.; Kouba, J. K.; Grimes C. J.; Cheung, S. K. Inorg. Chem.
1978, 17, 2666.
-
Me2Si(NtBu)2Sn2Cl+SnCl3 (see ref 3). Comparing Figure 1
and Table 2 it is evident that the point symmetry of the molecule
outside the lattice should be 2/m (C2h) and the symmetry
(16) Veith, M.; Recktenwald, O.; Humpfer, E. Z. Naturforsch. 1978, B 33,
14.
(17) Bushnell, G. W.; Eadie, D. T.; Pidcock, A.; Sam, A. R.; Holmes-
Smith, R. D.; Stobart, S. R. J. Am. Chem. Soc. 1982, 104, 5837.

Formation of Metal Clusters
Inorganic Chemistry, Vol. 35, No. 13, 1996 3853
Figure 1. SCHAKAL drawing of [Me2Si(NtBu)2Sn]2Co2Cl4 (4). The
nonnumbered atoms are carbon atoms; the hydrogen atoms are not
drawn.
Figure 3. Drawing of [Me2Si(NtBu)2Sn]4NiBr2 (7). The balls without
numbering represent carbon and nitrogen atoms.
Figure 2. SCHAKAL drawing of [Me2Si(NtBu)2Sn]2Zn2Cl4 (5). The
nonnumbered atoms are carbon atoms; the hydrogen atoms are omitted.
reduction in the solid should be due to the packing requirements.
In the zinc compound 5 the metal atom is approximately
tetrahedrally coordinated by three chlorine and one nitrogen
atom. In contrast to 4 the bis(amino)stannylene unit in 5 acts
only as a double Lewis acid-base system Via the tin and one
nitrogen atom toward the Zn-Cl(2) part whereas it acts as a
tridentate ligand toward Co-Cl(1) in 4. The consequence of
the different ligating properties of Me2Si(NtBu)2Sn in 4 and 5
can be seen from the sum of the angles around the nitrogen
atoms (for example N(2) in 5 summing up to 359.2°) or from
the distances N-Sn and N-Co or N-Zn (compare Table 2).
The N-Zn distances are typical for four coordinate zinc18
whereas the Co-N bond lengths are longer than expected.18
The remarkable difference in Co-N(1) and Co-N(2) bond
lengths is a reflection of the different pyramidalities at N(1)
and N(2) (sum of bond angles without Co at N(1) 246.7°, at
N(2) 243.4°).The coordination sphere of cobalt in 4 may best
be described by a distorted square pyramid, N(1), N(2), Cl(2),
and Cl(2′) forming the basal plane. The cobalt and zinc
distances to chlorine (mean values: 4, 2.360 Å; 5, 2.328 Å)
are within the standard values.18,19
The crystal structures of 7 and 8 are isotypic, the structures
of the molecules being displayed in Figures 3 and 4 and the
most important distances and angles in table 3. The quality of
the crystals from 8 has been superior to 7; this difference is
mostly due to librations of the tert-butyl groups which are more
important in the nickel case. In the molecules 7 and 8, the
transition metal elements are situated almost in the center of a
rectangle made up of four tin atoms the smaller edge of this
Sn4 rectangle being almost symmetrically bridged by a halogen
atom. None of the nitrogen atoms are interacting with the
Figure 4. ORTEP drawing of [Me2Si(NtBu)2Sn]4PdCl2 (8). The
elipsoids without numbering represent carbon and nitrogen atoms.
transition metals, and the SnN2Si rings are almost perpendicu-
larly oriented to the MSn4X2 plane. In each of the crystal
structures a benzene molecule is situated on an inversion center
of the lattice completing the crystal structure as a space filler.
The molecules have no crystallographic point symmetry. This
has a consequence for the crystal packing in this space group,
the molecules lining up to form a helical arrangement.
The central Sn4M metal cluster is not planar. Its deviation
is seen in the Sn(1)-M-Sn(4) and Sn(3)-M-Sn(2) angles with
the following values: 7, 162.9, 163.7°; 8, 164.5, 165.3°. The
deviation from the ideal value of 180° is more important in the
case of nickel compared to the palladium derivative and correlate
to a smaller Ni-Sn bond [mean: 2.463(3) Å] and a longer Pd-
Sn bond [mean: 2.544(2) Å]. The four tin-metal bonds are
equal within standard errors in both cases and are larger
compared to other tin-nickel2 or similar compared to other tin-
palladium bonds20 of homoleptic complexes with three-
coordinate tin. In comparison to Ni[Sn(NtBu)2SiMe2]4 (Ni-
Sn, 2.394(2) Å; Sn-N, 2.055(9) Å)2 the oxidation product 7
has longer Sn-Ni bond lengths as the coordination number at
tin is raised; contrarily the Sn-N bonds in 7 seem to be
comparativly short (mean in 7: 2.02 Å). The small deviation
from planarity in the clusters seem to explain in part the low
paramagnetism found in solutions of 7 in which we can assume
the atoms within the molecules to librate more freely.
The bromine and chlorine atoms in 7 and 8 are far away from
the transition metals and are equidistant to the tin atoms to which
(18) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(19) Olmstead, M. M.; Power, P. P.; Sigel, G. Inorg. Chem. 1986, 25, 1027.
(20) Hitchcock, P. B.; Lappert, M. F.; Misra, M. C. J. Chem. Soc., Chem.
Commun. 1985, 863.

3854 Inorganic Chemistry, Vol. 35, No. 13, 1996
Veith et al.
Figure 6. Drawing of the two enantiomeric molecules of Ph3PPd[Sn-
(NtBu)2SiMe2]3PdPPh3 in the crystal structure of 11. Only heavy atoms
have been numbered in part. A 3-fold crystallographic axis runs through
P(3)-Pd(3)-Pd(4)-P(4) and P(1)-Pd(1)-Pd(2)-P(2), respectively.
(2) Å] are considerably longer than those which have no chlorine
atom coordinated to germanium [mean: 1.836(2) Å].
From a structural point of view the structures of 7, 8
(presumably also 9, see Experimental Section), and 10 compare
well, as the inner metal cores MM′4 (M ) transition metal, M′
) Ge or Sn), which approaches a cross-bar, are apparently
similar. The deviations from planarity are also analogous to
one another and may be attributed to the steric bulkiness of the
Me2Si(NtBu)2El ligands. In all compounds no interaction of
the nitrogen atoms of the rings is observed with the transition
metal elements. It is interesting to note that the analogous
compound with Rh(I) and Sn(NtBu)2SiMe2 ligands to 10 has a
different composition {[Me2Si(NtBu)2Sn]5RhCl} and struc-
ture: rhodium is in the center of a trigonal bipyramid of tin
atoms.1 We ascribe this to the less space demanding property
of Me2Si(NtBu)2Sn, the Sn-N bond [mean 2.06 Å] being
approximately 0.2 Å longer than in Ge(NtBu)2SiMe2 and the
Rh-Sn distance [mean 2.55 Å]1 exceeding the Rh-Ge distances
by approximately 0.20 Å. All geometries found at Ni, Pd, and
Rh are consistent with a d8-configuration of the metallic atom.
A view of the two independent molecules present in the
crystal of Ph3PPd[Sn(NtBu)2SiMe2]3PdPPh3, 11, is shown in
Figure 6 while some of the distances and angles within these
molecules are depicted in Table 5. The two molecules are
similar with respect to the inner Pd2Sn3 trigonal bipyramidal
core coordinated at the Pd apices by Ph3P ligands. They are
different in the orientation of the four-membered SnN2Si cycles
with respect to Sn3 plane: while these rings form a right-handed
“paddle wheel” in the molecule with Pd(1) and Pd(2), they form
a left-handed “paddle wheel” in the other molecule as may be
easily deduced from inspection of Figure 6 (the dihedral angles
between the two planes can be calculated to 20.7°). Also the
phenyl groups on the phosphorus atoms follow in part these
geometries: thus the phenyl groups on P(2) and P(3) are turned
in form of a right handed “paddle wheel” while they are left
handed at the P(1) and P(4) atoms. The two molecules have
crystallographic C3 symmetry and can be considered as enan-
tiomeric forms.
Figure 5. SCHAKAL drawing of [Me2Si(NtBu)2Sn]4RhCl (10). The
balls without numbering are carbon and nitrogen atoms.
they are coordinated [deviation from symmetrical bridge in 7,
0.048 Å; in 8, 0.0455 Å (mean values)]. The Sn-X-Sn angles
are remarkably small (7, 75.35°; 8, 81.47°) whereas the mean
Sn-Cl (2.657(20) Å) distances are comparable to values found
-
in Sn2Cl5 anions (2.695 Å, Sn-Cl-Sn 105.5°).21
There is another feature of the structures of 7 and 8 which
should be pointed out: the deviation from planarity of the metal
cluster also has consequences on the Sn(NtBu)2-SiMe2 ligands.
Looking at Figure 4 it becomes clear that tert-butyl groups of
trans bis(amino)stannylenes are touching one another.
On the basis of the crystal structures the cluster compounds
7-9 can be described in two ways: either M2+ ions are
-
coordinated by two Me2Si(NtBu)2Sn-X-Sn(NtBu)2SiMe2
anions or the [Me2Si(NtBu)2Sn]4M2+ cation has two further X-
anions as counterparts. Any of these descriptions are of course
to be considered as borderline cases and the charge separation
into anions and cations is merely formal. The structural change
from [Me2Si(NtBu)2Sn]4Ni to Br2[Me2Si(NtBu)2Sn]4Ni (7) is
at the transition metal and is accompanied by a change of the
coordination site: where it changes from tetrahedral to almost
square planar.
In Figure 5 the molecular structure of [Me2Si(NtBu)2Ge]4RhCl
is drawn while the most important bond lengths and angles in
10 are assembled in Table 4. The molecule crystallizes with a
toluene molecule serving as a space filler in the lattice.
Rhodium is almost in the center of a slightly distorted planar
germanium square one edge of this square being bridged by a
chlorine atom. Two of the bis(amino)germylene cycles are
almost perpendicular to that plane [rings with Ge(3) and Ge-
(4)] while the other two are severely tilted. The deviation from
planarity may again be expressed by the angles Ge(1)-Rh-
Ge(4) [163.36(2)°] and Ge(2)-Rh-Ge(3) [161.34(2)°]. These
values compare well with the deviations found for the corre-
sponding Sn-M-Sn angles in 7 and 8 (see above). The four
germanium-rhodium bonds can be divided into two smaller
ones with three coordinate germanium atoms [mean: 2.337(1)
Å] and two larger ones with the tetracoordinate germanium
atoms Ge(3) and Ge(4) [mean: 2.373(2) Å]. The two chlorine
germanium bonds are equal within standard errors [mean:
2.599(3) Å] and the Ge-Cl-Ge angle [77.34(4)°] is acute like
the corresponding Sn-X-Sn angles in 7 or 8. As expected,
the Ge-N bonds adjacent to the chlorine bridge [mean: 1.851
In the metallic five-membered central cluster the six Sn-Pd
bonds are almost equal in the molecule with Pd(1) and Pd(2)
[Pd-Sn 2.697, 2.700 Å] while they are quite different in the
molecule with Pd(3) and Pd(4) [Pd-Sn 2.725, 2.688 Å]. So
far we have no straight forward explanation for this effect. The
Sn-Pd-Sn angles in the two molecules (98.78°, 99.15°)
approach 100° while the Pd-Sn-Pd angles are extremely acute
(57.54°, 56.94°). This may be taken as a hint that the two
palladium atoms form a Pd-Pd bonding interaction and the
distances between these atoms are short [Pd(1)-Pd(2) 2.597
Å, Pd(3)-Pd(4) 2.583 Å]. Our findings resemble those obtained
for Ph3PPt[Sn(acac)2]3PtPPh3 [Pt-Pt 2.593(1) Å, Pt-Sn-Pt
57.87(3)°] and we also would like to adopt the bonding
(21) Veith, M.; Go¨dicke, B.; Huch, V. Z. Anorg. Allg. Chem. 1989, 579,
99.

Formation of Metal Clusters
Inorganic Chemistry, Vol. 35, No. 13, 1996 3855
description proposed in this paper for the Pt2Sn3 cluster.17 Thus
the Pd should retain its closed-shell d10 character with three
hybrid orbitals on each Pd and with a single orbital at tin to
give three bonding, three nonbonding, and three antibonding
levels. The bonding model thus is based on a delocalization of
electron density between the five metal centers.
Compared to 8 the Pd-Sn bonds in 11 are elongated by
almost 0.159 Å. This is in line with the qualitative bonding
description given so far: the tin atom can supply the cluster
with only two electrons per atom and as two Pd centers have
to be satisfied the bonding in 11 should be less efficient as
compared to 8. The electron withdrawal from tin in 11 is also
observed in the Sn-N bonds in both compounds 8 (mean Sn-N
2.030(5) Å) and 11 (mean Sn-N 2.072(5) Å).
formation (although low in yield) is nevertheless remarkable
as the oxidation of [Me2Si(NtBu)2Sn]4Ni proceeds at the outer
sphere of the cluster without direct Br2-Ni interaction. At the
same time the nickel atom is transferred from a tetrahedral
coordination to almost square planar. Within the metal clusters
having five metallic elements and Me2Si(NtBu)2Sn as compo-
nents, [Me2Si(NtBu)2Ge]4ClRh fits in nicely among [Me2Si-
(NtBu)2Sn]4Ni and [Me2Si(NtBu)2Sn]4MX2 (M ) Ni, Pd, Pt).
The five membered metal cluster in Ph3PPd[Sn(NtBu)2SiMe2]3-
PdPh3 (11) is structurally very different from 7-10; this can
be attributed to the fact that the metal cluster is electron deficient
compared to the other compounds.
Acknowledgment. We would like to thank the Fonds der
Chemischen Industrie and the Deutsche Forschungsgemeinschaft
(DFG) for financial support.
Conclusions
It has been shown that transition metal chlorides (bromide
for Ni) behave differently toward Me2Si(NtBu)2Sn, forming
either Lewis acid-base adducts or metal clusters. Br2[Me2Si-
(NtBu)2Sn]4Ni can also be generated in low yield by treating
[Me2Si(NtBu)2Sn]4Ni with Br2 or R4NBr3, the main reaction
leading to oxidative degradation of the starting compound. This
Supporting Information Available: Tables of X-ray experimental
details, bond lengths and angles, positional parameters, and anisotropic
thermal parameters for 4, 5, 7, 8, 10, and 11 (41 pages). Ordering
information is given on any current masthead page.
IC960007A