Synthesis and structure of dinuclear [(2-tert-butyl-4,5,6-trimethylphenyl)2Sn-Co(η 2-ethene)(η5-Me5C5)] and its thermal conversion to trinuclear [{(2-tert-butyl-4,5,6-trimethylphenyl)2Sn}2Co(η 5-Me5C5)] (Co-Sn2)

Article abstract of DOI:10.1016/S0022-328X(99)00172-2

The title compounds 4 and 12 are prepared by reacting bis{(η²-ethene)}(η ⁵-pentamethylcyclopentadienyl)cobalt(I) 3 with Weidenbruch's stannylene bis[bis{6-tert-butyl-2,3,4-trimethylphenyl}tin] (1) employing different thermal reaction conditions. Compounds 4 and 12 are rare examples of transition metal complexes of 1. According to an X-ray crystal structure determination, 4 displays a half-sandwich structure with trigonal planar coordinated Co atom and a subvalent Sn(II) center. The Co-Sn bond length in 4 is 2.3926(4) A and represents one of the shortest reported so far. A comparison of relevant bonding parameters of 4 and several related Co-Sn half-sandwich compounds containing low valent SnR₂ fragments reveals comparable steric and electronic effects of the stannylenes towards the 16 e {(η²-ethene)(Me₅C₅)Co} fragment in these complexes. In contrast to the isostructural ethene/stannylene complex bis{methyl(trimethylsilyl)}stannio(η²-ethene)(η ⁵-cyclopentadienyl)cobalt 6 containing Lappert's bis(stannanediyl) 2, 4 is inert towards H₂O and does not activate water by an oxidative addition reaction to give a mixed hydroxo hydrido complex. At elevated temperatures, 4 reacts via ethene dissociation and ligand redistribution to form the trinuclear cobalt bis stannylene half sandwich complex Bis[bis{6-tert-butyl-2,3,4-trimethylphenyl}]stannio(η ⁵-pentamethylcyclopentadienyl)}cobalt(I) 12 in moderate yields.

Full text of DOI:10.1016/S0022-328X(99)00172-2

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 338–343
Synthesis and structure of dinuclear
[(2-tert-butyl-4,5,6-trimethylphenyl)2Sn-Co(h2-ethene)(h5-Me5C5)]
and its thermal conversion to trinuclear
[{(2-tert-butyl-4,5,6-trimethylphenyl)2Sn}2Co(h5-Me5C5)] (Co–Sn2)
Jo¨rg J. Schneider *, Norbert Czap, Dieter Bla¨ser, Roland Boese
Institut fu¨r Anorganische Chemie der Uni6ersita¨t/GH-Essen, Uni6ersita¨tsstraße 5–7, D-45117 Essen, Germany
Received 22 February 1999
Abstract
The title compounds 4 and 12 are prepared by reacting bis{(h2-ethene)}(h5-pentamethylcyclopentadienyl)cobalt(I) 3 with
Weidenbruch’s stannylene bis[bis{6-tert-butyl-2,3,4-trimethylphenyl}tin] (1) employing different thermal reaction conditions.
Compounds 4 and 12 are rare examples of transition metal complexes of 1. According to an X-ray crystal structure determination,
4 displays a half-sandwich structure with trigonal planar coordinated Co atom and a subvalent Sn(II) center. The Co–Sn bond
,
length in 4 is 2.3926(4) A and represents one of the shortest reported so far. A comparison of relevant bonding parameters of 4
and several related Co–Sn half-sandwich compounds containing low valent SnR2 fragments reveals comparable steric and
electronic effects of the stannylenes towards the 16 e {(h2-ethene)(Me5C5)Co} fragment in these complexes. In contrast to the
isostructural ethene/stannylene complex bis{methyl(trimethylsilyl)}stannio(h2-ethene)(h5-cyclopentadienyl)cobalt 6 containing
Lappert’s bis(stannanediyl) 2, 4 is inert towards H2O and does not activate water by an oxidative addition reaction to give a mixed
hydroxo hydrido complex. At elevated temperatures, 4 reacts via ethene dissociation and ligand redistribution to form the
trinuclear cobalt bis stannylene half sandwich complex Bis[bis{6-tert-butyl-2,3,4-trimethylphenyl}]stannio(h5-pentamethylcy-
clopentadienyl)}cobalt(I) 12 in moderate yields. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Cobalt; Tin; Stannylene; Ethylene; Half-sandwich
M–M% combinations (M=transition metal, M%=
main group metal) interesting to pursue in more
depth. Our interest in this area has focused on het-
erodinuclear organometallic complexes containing a
reactive M–M% bond (M=transition metal; M%=
group 12, 13 or 14 metal), particulary those with an
unbridged M–Sn bond like 6–10 which possess a
metal bonded :SnR2 stannylene fragment (Fig. 1,
[2]).Complexes 6–10 offer ideal prerequisites for the
linkage of novel metal–element bonds by insertion or
addition reactions [2a,d]. Especially interesting fea-
tures with regard to reactivity are the three-fold coor-
dinated sub-valent Sn(II) center and the existence of
an additionally labile bonded ethene ligand in the
cobalt and iron complexes 6–10. Thus, these com-
pounds offer two distinct different sites for chemical
reactivity.
1. Introduction
Unbridged metal–metal bonds exhibit a high reac-
tivity especially when the M–M bonds are polarized.
By choosing an appropriate combination of a transi-
tion metal and a main group metal, the bond polarity
M–M% can be tuned, thus allowing creation of chemi-
cal reactivity of such a bond mainly by bond polar-
ization effects. The concept of bond polarity is not so
readily applicable to M–M bonds (M=transition
metal) [1], thus making the chemistry of heteronuclear
* Corresponding author. Fax: +49-201-183-4195.
E-mail address: joerg.schneider@uni-essen.de (J.J. Schneider)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00172-2

J.J. Schneider et al. / Journal of Organometallic Chemistry 584 (1999) 338–343
339
2. Results and discussion
The coordination of :SnR2 stannylene or stan-
nanediyl fragments to low valent transition metal cen-
ters is already known for a number of transition metal
fragments, mostly containing strong donor–acceptor
substituents like e.g. CO [3]. Examples for the coordina-
tion of :SnR2 fragments to pure hydrocarbyl transition
metal fragments are still rare. With respect to the
nature of M–Sn bonding in such complexes, relevant
bond distances M–Sn are usually found to be signifi-
cantly shorter in pure (hydrocarbyl)transition metal
stannylene complexes than in heteroelement—espe-
cially CO—substituted ones [4]. This fact results from a
distinct M–Sn double bond character for the former
complexes as judged from their binding parameters and
we are interested in finding new examples exhibiting
such short M–Sn bonding.
The reaction of bis[{2-tert-butyl-4,5,6-trimethyl-
phenyl}2tin] (1) with [(h5-Me5C5)Co(h2-C2H4)2] 3, first
at room temperature and then at reflux temperature in
ether leads to dissociation of one ethene ligand and
substitution by an SnR2 fragment generated from 1,
and results in formation of the mixed mono(ethene/
stannylene)cobalt complex 4 (Eq. (1)).
(1)
Herein we report on our studies towards synthesis,
structure and unusual thermal reactivity of a new stan-
nylene cobalt complex containing an unbridged short
Co–Sn bond. In particular, we present the introduction
of the :SnR2 hydrocarbyl stannylene bis{2-tert-butyl-
4,5,6-trimethylphenyl}tin derived from the bis(bis(hy-
drocarbyl)-stannylene (1), as ligand in organocobalt
chemistry and report on the distinct altered chemical
and thermal reactivity of the new cobalt stannylene
complex 4 compared to its isostructural analogues 6
and 7 containing the Sn{(CH(SiMe3)2}2 fragment
derived from Lappert’s bis(stannanediyl) 2.
Ethene substitution in 3 already stops after one
ethene ligand is replaced by a SnR2 unit even when an
excess of stannylene is present. This situation is main-
tained even when 3 is already formed but is still further
Fig. 1.

340
J.J. Schneider et al. / Journal of Organometallic Chemistry 584 (1999) 338–343
Table 1
refluxed with an excess of the bis(stannanediyl) (1) in
ether. Complex 4 is highly soluble in pentane and ether.
From the latter solvent, 4 can be obtained at −20°C as
deep purple to black crystals which are stable at room
temperature.
13
1H- and
C-NMR data for 4 and 12
1H-NMR (C6D6, 27°C, l (ppm)):
4:
4:
7.19, 7.12 (2s, 2H, ꢀCHaryl)
3.27, 3.15, 2.10, 2.08, 2.03 (2s, 6H; s, 6H; s, 6H;
all CH3-aryl)
2.43, 2.20, 2.12, 1.93 (4m, vbr, 4H, C2H4)
1.71 (s, 15H, Me5C5)
7.32, 7.09 (2s, 4H, ꢀCH)
Interestingly 4 cannot be crystallized at −78°C from
diethylether during several months, possibly indicating
a reversible ether solvent coordination to the sub-valent
Sn(II) center in 4. At higher temperatures (\ −30°C),
dissociation of the ether ligand might occur which
lowers the solubility of 4 and in turn allows crystalliza-
tion of 4 within a few days as deep purple to black
crystal chunks. The plausible coordination of the ether
solvent at temperatures \ −30°C can be understood
by a donation of the oxygen lone pair of the ether
solvent into the low lying vacant 5p p-orbitals of the
subvalent three-fold coordinated Sn(II) center (Eq. (2)).
A similar solvent coordination behavior has been found
for Lappert’s bis(stannanediyl) [{Sn{CH(SiMe3)}2}2] (2)
[6] and the Ni complex [(h2-C2H4)2Ni-Sn{CH(Si-
Me3)2}2] (5) derived therefrom [7]. To the best of our
knowledge, such a behaviour is reported here for the
first time for a transition metal complex containing a
pure bis(hydrocarbyl)stannylene :SnR2 like [(2-tert-
butyl-4,5,6-trimethylphenyl)2Sn:].
2.49, 2.25, 2.11. 1.76, 1.67 (2s, 9H, s, 18H, 2s, 9H,
CH3-aryl)
1.58, 1.52 (2s, 36H, C(CH3)3)
1.41 (s, 15H, Me5C5)
13C-NMR (C6D6, 27°C, l (ppm)):
12: 160.5, 158.6, 153.3, 153.2, 142.0, 141.9, 136.1, 135.8, 134.1,
133.9 (sp2Caryl
)
127.6, 127.2 (sp2Caryl–H)
89.6 (Me5C5)
37.2, 36.8 (C(CH3)3)
34.8, 28.2 (C2H4)
32.6, 32.4 (C(CH3)3)
23.5, 22.6, 21.5, 16.0, 15.9 (CH3aryl
10.7 (Me5C5)
)
12: 168.2, 164.0, 154.7, 152.1, 148.4, 144.6, 135.7, 135.6, 133.8,
133.5 (sp2Caryl
)
127.2, 125.6 (sp2Caryl–H)
92.5 (Me5C5)
34.1, 33.6 (C(CH3)3)
33.1, 32.8 (C(CH3)3)
37.5, 36.8, 21.4, 21.3, 16.0, 15.1 (CH3aryl
9.2 (Me5C5)
)
EI–mass spectroscopy of 4 reveals an easy loss of the
ethene ligand giving the [M–C2H4]+ fragment ion as
highest m/e signal in the mass spectrum.
(2)
4. Molecular structure of 4
X-ray quality crystals of 4 were obtained from con-
centrated diethylether solutions at −20°C over several
days. Its molecular structure is depicted in Fig. 2 [9].
The tin atom displays an ideal trigonal structure
reflected by the sum of the bond angles (359.9°). If
Me5C5 is considered to occupy three coordination sites
and the |-bonded :SnR2 and the ethene ligands occupy
two sites, 4 corresponds to a five coordinated com-
pound. The bonding parameters of the {(h2-
ethene)(Me5C5)Co} fragment are virtually in agreement
with the closely related complexes 6 and 7 containing
Lappert’s stannylene [2a].
3. NMR characterization of 4
According to the results of the H- and 13C-NMR
1
analysis of 4, both aryl ligands at tin are chemically
inequivalent. As already observed for the related Co–
Sn complexes 6–8, as well as the isoelectronic Fe–Sn
complexes 9 [2c] and 10, the protons of the ethene
ligand of 4 appear as broad resonances (Table 1).
Compared to the (ethene)Co–Sn complex 11 contain-
ing penta-coordinated tin [8], the proton signals of the
p coordinated ethene of 4 are significantly shifted to
lower field (Dl=1 ppm) indicating the missing p-back-
bonding acceptor ability of the penta-coordinated Sn in
11, which is due to the two additional N donor atoms
present in 11 compared to the situation at the trivalent
Sn in 4, still containing a low lying vacant 5p p-orbital.
The NMR assigments for 4 were substantiated by a
C–H COSY experiment.
,
The Co–Sn distance is 2.3926(4) A for 4, and well
below the sum of the covalency radii of Co and Sn
,
(2.55 A) and in good agreement with the Co–Sn bond
,
,
distance found in 6 (2.396(1) A) [2a] and 7 (2.386(2) A)
[2d] as well as in the related isoelectronic complex
bis{(2 - tert - butyl - 4,5,6 - trimethylphenyl)}stannio(h2 -
ethene)(h6-toluene)iron 9 containing a Fe–Sn bond
,
(2.4362(10) A) [2c]. It is intriguing to compare the

J.J. Schneider et al. / Journal of Organometallic Chemistry 584 (1999) 338–343
341
5. Reactivity studies of 4
Co–Sn atom distances with the Ni–Sn distance of
,
2.387(1) A, which is found only insignificantly shorter
As we have shown recently, the stannylene complexes
6–8 bearing Lappert’s stannnanediyl ligand [:Sn{CH-
(SiMe3)2}2] display a high reactivity towards alkynes or
chalcogenes [2a,10] Reactions of 6–8 with alkynes are
initiated by an initial loss of the p bonded ethene
ligand, further reaction steps in the sequence are alkyne
coordination, followed by catalytic or stoichiometric
transition metal centered C–C and C–Sn coupling
reactions, leading to homo (alkynes); or mixed alkyne/
stannylene cyclotrimerization leading to cobalt(stanna-
cyclopentadienyl) products [10].
Most recently we have found that the cobalt stan-
nylene complex 6, after ethene loss is able to activate
water by an oxidative addition reaction at room tem-
perature giving an unusual hydroxo hydrido complex
[11]. In sharp contrast to these findings 4 is completely
inert towards H2O under identical reaction conditions.
Stirring etheral solutions of 4 with a 50 fold excess of
H2O for several hours, allows to recover 4 nearly
quantitatively. These findings point towards a distinct
alteration of chemical reactivity of 4 versus 6 when
changing the {CH3(SiMe3)2} fragments against the {(2-
tert-butyl-4,5,6-trimethylphenyl)arene} fragments as
ligands at tin.
in the bis(ethene)nicke-(stannylene) complex 5 [7a].
For 5 significant double bond character of the Ni–Sn
bond is discussed according to Nidp–Snpp backbond-
ing contributions based on a modified Duncanson–
Chatt model [7a,b]. Support of this interpretation
comes from shortened Sn–Csp3 bond distances in the
Ni–Sn{CH(SiMe3)}2 fragment in 5 compared to the
relevant
Sn–Csp3
distances
in
the
‘free’
[{Sn(CH(SiMe3)2}2] bis(stannanediyl) 2 [6a,b]. Such a
shortening, however, is not found in the cobalt com-
plexes 6–8. Relevant Sn–Csp3 bond distances in 6–9
are only insignificantly shorther compared to the
‘free’ bis(stannanediyls) 1 and 2 (1: 2.218(5) and
2.189(5) A) [5], 2: 2.22 A [6c]). The same holds true
for the Sn–Cipso(aryl) distances in the isoelectronic Fe–
Sn complex 9 (2.252 A) containing Weidenbruch’s
stannylene [bis{(2-tert-butyl-4,5,6-trimethylphenyl)}-
Sn:] [2c]. Hence a ‘partial oxidation’ caused by signifi-
cant p-donor capability of the subvalent Sn atoms
towards the Co or Fe atoms in 4 as well as in 6–9 is
not reflected in these data and is in contrast to the
Ni–Sn compound 5. Nevertheless, a Mdp–Snpp contri-
bution seems to be reasonable in view of the close
resemblance of the overall very short M–Sn bond
lengths in 4 and 6–9. An in depth discussion of M–
Sn bonding in these transition metal/stannylene half-
sandwich complexes must await future work.
,
,
,
Complex 4 is thermally stable under refluxing condi-
tions in diethylether (see Section 2). However prolonged
heating at elevated temperatures (75°C, toluene) causes
a color change of the initial clear deep purple to a clear
brown solution within a few hours and is accompanied
by evolution of ethene. After workup and crystalliza-
tion at −30°C for several weeks, brown crystals of the
trimetallic bis(stannylene)cobalt complex 12 could be
isolated in moderate yield (Eq. (3)).
Fig. 2. Molecular structure of 4 in the solid state as determined by
,
X-ray crystallography. Selected bond length (A) and angles (°):
Sn–Co 2.3926(4), Sn–C1 2.228(3), Sn–C14 2.228(3), Co–C27
2.001(3), Co–C28 2.024(3); C14–Sn–Co 122.94(7), C1–Sn1–C14
106.44(10), C1–Sn–Co 130.61(6).
(3)

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J.J. Schneider et al. / Journal of Organometallic Chemistry 584 (1999) 338–343
6. Spectroscopic characterization of 12
1, 2 and 3 were synthesized according to the literature
[3a,13]. Microanalysis were performed by the microana-
lytical laboratory of the Chemistry Department of the
University/GH-Essen. All solvents were dried appropri-
ately and were stored under nitrogen. The NMR spec-
tra were recorded on a Bruker AC 300 spectrometer
(300 MHz for 1H, 75 MHz for 13C) and referenced
against the remaining protons of the deuterated solvent
used. NMR samples were prepared by vacuum transfer
of predried, degassed solvents onto the appropriate
amount of solid sample, followed by flame sealing of
the NMR tube. EI-MS spectra were recorded on a
MAT 8200 instrument using standard conditions (EI,
70 eV). A fractional sublimation technique was used in
the EI spectra for compound inlet. IR spectra were
recorded in KBr with a Nicolet 7109 FT- instrument.
Under electron impact mass spectroscopic conditions
(70 eV), only the characteristic SnR2 stannylene ligand
fragment is observed as main fragmentation pattern.
However, under fast atom bombardment conditions
(fab) the characteristic molecular ion [M]+ m/e 1130 as
well as the fragment ion [M–SnR2]+ m/e 663 as base
peak and various distinct other fragment ions are ob-
served for 12 (see Section 8).
1
The H- and 13C-NMR data confirm that the four
aryl ligands are pairwise inequivalent and therefore
show two sets of relevant signals, one for the two
endo-2-tert-butyl-4,5,6-trimethylphenyl ligands and one
for the two exo-2-tert-butyl-4,5,6-trimethylphenyl lig-
ands (Table 1). This assignment is further substantiated
by our recent synthesis of an isolobal bis(stannylene)
iron complex, derived from a reaction of 1 with sol-
vated iron atoms [12].
In contrast to 4 a similar, thermally induced rear-
rangement of the closely related (Cp)(ethene)cobalt–
stannylene derivative 6 containing Lappert’s stannylene
is not observed. Instead, treatment of 6 under electron
impact mass spectroscopic conditions (EI MS) (10−3
torr, 70 ev) results in ethene dissociation and gives a
signal in the EI MS of nominal composition
C38H86Co2Si8Sn2 [2a].
8.2. Synthesis of bis{2-tert-butyl-4,5,6-trimethyl-
phenyl}stannio(p2-ethene)(p5-penta-methylcyclo-
pentadienyl)cobalt(I) 4
A total of 0.27 g (1.1 mmol) 3 and 1.01 g (2.1 mmol)
1 were dissolved in 40 ml diethylether at room tempera-
ture. Stirring for 18 h at room temperature caused a
color change to purple. Stirring was continued under
reflux for three more hours. Removal of all volatiles in
vacuum left a dark residue which was dissolved in 25
ml diethylether and filtered to give a clear deep purple
colored solution from which 0.53 g (0.76 mmol, 71%)
purple crystals of 4 separated within a few days at
−20°C. MS(Ei, 70 eV) 662(1) [M–C2H4]+, 469(1)
[SnAr2]+, 222(10) [M–SnAr2]+. NMR data see Table
1. IR(KBr) 3041(s, ꢀC–H), 2897(s, Me5C5), 2728(s,
The different reactivity of 4 and 6 in the thermal
rearrangement behaviour as well as the reactivity with
water points towards distinct different electronic effects
of the SnR2 fragments as ligands to the [(h2-ethene)(h5-
CpR)Co] fragment.
PhtBuMe ), 1376 (m, Me5C5), 1176 (m, C2H4). Anal.
3
7. Conclusions
Calc. for C38H57CoSn (691.59) C 66.04, H 8.26. Found
C 66.02, H 8.23.
It was shown that the :SnR2 hydrocarbyl stanny-
lene ligand bis{6-tert-butyl-2,3,4-trimethylphenyl}tin
derived in solution from the bis(stannanediyl) 1 is able
to substitute either one or two ethene ligands in bis(h2-
8.3. Synthesis of bis{bis{2-tert-butyl-4,5,6-trimethyl-
phenyl}stannio}(p5-pentamethyl-cyclopentadienyl)-
cobalt(I) 11
ethene)(h5-pentamethylcyclopentadienyl)cobalt
3
to
form the di- and trimetallic cobalt stannylene halfsand-
wich complexes 4 and 12 representing rare examples of
transition metal complexes of this stannylene. The X-
ray structure of 4 reveals a short Co–Sn bond, indicat-
ing a distinct Co to Sn p-backbonding contribution in
addition to the Co–Sn single bond.
A total of 0.27 g (1.1 mol) 3 and 1.101 g (2.1 mmol)
1 were dissolved in 20 ml toluene and stirred for one
hour at 75°C where upon the color changed from red
brown to purple within a few minutes indicating initial
formation of 4. After one additional hour at 75°C, the
purple color of the reaction mixture changed to a deep
brown. Cooling to room temperature and removal of
all volatiles in vacuum leaves a brown residue which
was dissolved in ether, filtered and cooled to −30°C.
This procedure afforded 198 mg (0.18 mmol, 16.3%) 11
as red brown microcrystalline material. MS(fab)
1130(3) [M]+, 955(6) [M–aryl]+, 779(5) [M-2(aryl)]+,
663(100) [M–Sn(aryl)2]+. NMR data see Table 1.
8. Experimental
8.1. General experimental information
All reactions were carried out under an atmosphere
of dry nitrogen gas with standard Schlenk techniques.

J.J. Schneider et al. / Journal of Organometallic Chemistry 584 (1999) 338–343
343
S. Friedrich, L.H. Gade, I.J. Scowen, M. McPartlin, Angew.
Chem. 108 (1996) 1440; Angew. Chem. Int. Ed. Engl. 35 (1996)
1338. (e) S. Friedrich, L.H. Gade, I.S. Scowen, M. McPartlin,
Organometallics 14 (1995) 5344; (f) D. Selent, R. Beckhaus, J.
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Boese, F. Fabrizia de Biani, P. Zanello, C. Kru¨ger, Eur. J. Inorg.
Chem., in press.
Anal. Calc. for C62H91CoSn2 (1132.88) C 65.73, H 8.10.
Found C 65.84, H 8.05.
9. Supplementary material
X-ray crystallographic data for 4: a single crystal
with the approximate size 0.68×0.56×0.23 mm3, for-
mula C38H57CoSn, (MG 691.46) was measured a
Siemens-Smart CCD three circle diffractometer with
Mo–Ka radiation at 183 K. Cell dimensions of the
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Marsmann, Chem. Ber. 128 (1995) 983.
monoclinic system a=9.9156(1), b=30.8055(2), c=
3
,
,
12.1535(1) A, ×=106.875(1)°, V=3552.49(5) A , space
group P21/n with Z=4, Dx=1.293 g cm−3, :=1.19
mm−1, empirical absorption correction min/max trans-
mission 0.55/1.00, Rmerg before/after correction 0.0893/
0.0415, 30891 intensities collected (2[max=56.7°), 7276
unique (Rint(F2)=0.0421), 6649 observed (F2o (2|(F2)),
structure solution (direct methods) and refinement (361
parameters, H atoms as riding groups, 1.2 fold
isotropic U-values, 1.5 fold for methyl groups of the
corresponding C-atoms) with Siemens-SHELXTL (Ver.
5.03), R1=0.0419, wR2 (all data)=0.1082, GOF=
1.089, residual electron density 1.83 e A−3 at a distance
of 1.64 A from Sn1. Crystallographic data (excluding
,
,
structure factors) for the structure(s) reported in this
paper have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication
no. CCD-114510. Copies of the data can be obtained
free of charge on application to: The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [fax: +44-
1223-336-033; e-mail: deposit@chemcrys.cam.ac.uk].
[6] (a) P.J. Davidson, M.F.Lappert, J. Chem. Soc. Chem. Commun.
(1973) 317. (b) J.D. Cotton, P.J. Davidson, D.E. Goldberg, M.F.
Lappert, K.M. Thomas, J. Chem. Soc. Chem. Commun. (1974)
893. (c) P.J. Davidson, D.H. Harris, M.F. Lappert, J. Chem.
Soc. Dalton Trans. (1976) 2268.
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Du¨sseldorf, 1992.
[8] K. Angermund, K. Jonas, C. Kru¨ger, J.L. Latten, Y.-H. Tsay, J.
Organomet. Chem. 353 (1988) 17.
[9] J.J. Schneider, N. Czap, D. Bla¨ser, R. Boese, C. Janiak,
manuscript in preparation.
Acknowledgements
This work was supported by the DFG (Heisenberg
fellowship and grants SCHN 375/3-1 and 3-2 to JJS)
and the Fonds der Chemischen Industrie. The authors
would like to thank Dr D. Sto¨ckigt and Dr K. Seevogel
and coworkers (MPI fu¨r Kohlenforschung, Mu¨lheim)
for recording mass and infrared spectra.
[10] J.J. Schneider, J. Hagen, O. Heinemann, C. Kru¨ger, F. Biani de
Bianchini, P. Zanello, Inorg. Chim. Acta 281 (1998) 53.
[11] J.J. Schneider, N. Czap, J. Hagen, C. Kru¨ger, S.A. Mason, R.
Bau, J. Ensling, P. Gu¨tlich, Chem. Eur. J., submitted for publi-
cation.
[12] N. Czap, Dr. rer. nat. dissertation, University of Essen, 1999.
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