Syntheses and crystal structures of heteroleptic stannylenes and germylenes

Article abstract of DOI:10.1021/om980836z

Two novel, monomeric heteroleptic derivatives of divalent Sn [Sn(2-{(Me₃Si)₂C}-C₅H₄N)R] [R = Sn(SiMe₃)₃ (1) or Si(SiMe₃)₃ (2)] and divalent Ge [Ge(2-{(Me₃Si)₂C}-C₅H₄N)R] [R = Cl (3) or CH(PPh₂)₂ (4)] have been prepared and characterized, and their molecular structures were determined by single-crystal X-ray diffraction. The stannylenes 1 and 2 were prepared from the corresponding heteroleptic chloro-analogue, [Sn(2-{(Me₃Si)₂C}-C₅H₄N)Cl]; 1 is the first structurally characterized compound to contain a bond between divalent Sn and tetravalent Sn and 2 is only the second structurally characterized example of a silyl-substituted heteroleptic stannylene. The Ge analogue of [Sn(2-{(Me₃Si)₂C}-C₅H₄N)Cl] (3) has been prepared and its utility as a precursor to further examples of heteroleptic germylenes demonstrated by the preparation and characterization of [Ge(2-{(Me₃Si)₂C}-C₅H₄N)CH(PPh ₂)₂] (4).

Full text of DOI:10.1021/om980836z

Organometallics 1999, 18, 389-398
389
Syn th eses a n d Cr ysta l Str u ctu r es of Heter olep tic
Sta n n ylen es a n d Ger m ylen es
Sisco Benet, Christine J . Cardin, David J . Cardin,* Steven P. Constantine,
Peter Heath, Haroon Rashid, Susana Teixeira, J ames H. Thorpe, and
Alan K. Todd
Department of Chemistry, University of Reading, Whiteknights, P.O. Box 224,
Reading RG6 6AD, U.K.
Received October 6, 1998
Two novel, monomeric heteroleptic derivatives of divalent Sn [Sn(2-{(Me3Si)2C}-C5H4N)R]
[R ) Sn(SiMe3)3 (1) or Si(SiMe3)3 (2)] and divalent Ge [Ge(2-{(Me3Si)2C}-C5H4N)R] [R ) Cl
(3) or CH(PPh2)2 (4)] have been prepared and characterized, and their molecular structures
were determined by single-crystal X-ray diffraction. The stannylenes 1 and 2 were prepared
from the corresponding heteroleptic chloro-analogue, [Sn(2-{(Me3Si)2C}-C5H4N)Cl]; 1 is the
first structurally characterized compound to contain a bond between divalent Sn and
tetravalent Sn and 2 is only the second structurally characterized example of a silyl-
substituted heteroleptic stannylene. The Ge analogue of [Sn(2-{(Me3Si)2C}-C5H4N)Cl] (3)
has been prepared and its utility as a precursor to further examples of heteroleptic
germylenes demonstrated by the preparation and characterization of [Ge(2-{(Me3Si)2C}-
C5H4N)CH(PPh2)2] (4).
In tr od u ction
halide or amide), (ii) the robust nature of SnR2 (in
comparison, for example, with the Pb analogues which
have weaker Pb-ligand bonds, a tendency to dispro-
portionate,21 and are often light and/or thermally sensi-
tive), and (iii) the I ) 1/2, ca. 9% abundant, 119Sn nucleus.
We have recently made several reports on the prepa-
ration and characterization of organometallic deriva-
tives of divalent Sn.2,22 For example, the additional
intramolecular N-atom coordination provided by 2-
{(Me3Si)2C}-C5H4N permitted the preparation of a range
of novel heteroleptic compounds by providing stabiliza-
tion with respect to ligand redistribution and/or oligo-
merization. [Sn(2-{(Me3Si)2C}-C5H4N){CH(PPh2)2}]2 (5)
was of interest inter alia as the homoleptic Sn(II) and
Pb(II) analogues [E{CH(PPh2)2}2] (E ) Sn, Pb) have
been shown to possess two different bonding modes (η1,
C-bound and η2, P-bound) within the same molecule.
The organometallic chemistry of the heavier divalent
group 14 element carbene analogues, ER2, is now an
active area of research, with structural data available
for an increasingly wide range of compounds (E ) Sn >
Ge . Pb > Si; R ) alkyl, aryl, amide, silyl).1,2 This is
due in part to the rich variety of reactivity and coordi-
nation chemistry encountered,3 but also to the now wide
availability of techniques such as 29Si{1H}, 119Sn{1H},
and 207Pb{1H} NMR spectroscopies for the direct, in situ
study of non-hydrogen/carbon nuclei. There is a great
deal of interest in thermally or photolytically generated
Si and Ge carbene analogues,4,5 however, it is the Sn
analogues which have afforded by far the greatest
number of stable, structurally characterized (and mon-
omeric) examples.6-20 This is a reflection on (i) the broad
range of divalent precursors available, e.g. SnX2 (X )
[Sn(2-{(Me3Si)2C}-C5H4N)(C6H2-2,4,6-Pri )]2 (6), pre-
3
pared by the reaction of [Sn(2-{(Me3Si)2C}-C5H4N)Cl]23
* To whom correspondence should be addressed. E-mail:
D.J .Cardin@Reading.ac.uk.
(1) Simons, R. S.; Lihung, P.; Olmstead, M. M.; Power, P. P.
Organometallics 1997, 16, 1920.
(2) Cardin, C. J .; Cardin, D. J .; Constantine, S. P.; Convery, M. A.;
Drew, M. G. B.; Fenske, D.; Rashid, H. J . Chem. Soc., Dalton Trans.
1998, 2749.
(3) Lappert, M. F.; Rowe, R. S. Coord. Chem. Rev. 1990, 100, 267.
(4) Schriewer, M.; Neumann, W. P. J . Am. Chem. Soc. 1983, 105,
897.
with Li(Et2O)‚C6H2-2,4,6-Pri , is stable in solution at
3
(12) Westerhausen, M.; Gruel, J .; Hausen, H. D.; Schwarz, W. Z.
Anorg. Allg. Chem. 1996, 622, 1295.
(13) Dias, H. V. R.; J in, W. C. J . Am. Chem. Soc. 1996, 118, 9123.
(14) Dias, H. V. R.; J in, W. C. Inorg. Chem. 1996, 35, 6546.
(15) Braunschweig, H.; Drost, C.; Hitchcock, P. B.; Lappert, M. F.;
Pierssens, L. J . M. Angew. Chem., Int. Ed. Eng. 1997, 36, 261.
(16) Agustin, D.; Rima, G.; Barrau, J . Main Group Metal Chem.
1997, 20, 791.
(17) Allan, R. E.; Beswick, M. A.; Coggan, G. R.; Raithby, P. R.;
Wheatley, A. E. H.; Wright, D. S. Inorg. Chem. 1997, 36, 5202.
(18) Armstrong, D. R.; Duer, M. J .; Davidson, M. G.; Moncrieff, D.;
Russell, C. A.; Stourton, C.; Steiner, A.; Stalke, D.; Wright, D. S.
Organometallics 1997, 16, 3340.
(19) Hitchcock, P. B.; Hu, J .; Lappert, M. F.; Layh, M.; Severn, J .
Chem. Commun. 1997, 1189.
(20) Hitchcock, P. B.; Lappert, M. F.; Layh, M. Inorg. Chim. Acta
1998, 269, 181.
(21) Harrison, P. G.; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds. Pergamon Press: Oxford, England, 1982; p 670.
(22) Cardin, C. J .; Cardin, D. J .; Constantine, S. P.; Todd, A. K.;
Teat, S. J .; Coles, S. Organometallics 1998, 17, 2144.
(5) Raabe, G. W.; Michl, J . Chem. Rev. 1985, 85, 419.
(6) Braunschweig, H.; Chorley, R. W.; Hitchcock, P. B.; Lappert, M.
F. J . Chem. Soc., Chem. Commun. 1992, 1311.
(7) Braunschweig, H.; Hitchcock, P. B.; Lappert, M. F.; Pierssens,
L. J . M. Angew. Chem., Int. Ed. Eng. 1994, 33, 1156.
(8) Edwards, A. J .; Paver, M. A.; Raithby, P. R.; Russell, C. A.;
Steiner, A.; Stalke, D.; Wright, D. S. Inorg. Chem. 1994, 33, 2370.
(9) Edwards, A. J .; Paver, M. A.; Raithby, P. R.; Rennie, M. A.;
Russell, C. A.; Wright, D. S. J . Chem. Soc., Dalton Trans. 1995, 1587.
(10) Braunschweig, H.; Gehrhus, B.; Hitchcock, P. B.; Lappert, M.
F. Z. Anorg. Allg. Chem. 1995, 621, 1922.
(11) Ceaolivares, R.; Novosad, J .; Woollins, J . D.; Slawin, A. M. Z.;
Garciamontalvo, V.; Espinosaperez, G.; Garcia, P. G. Y. Chem. Com-
mun. 1996, 519.
10.1021/om980836z CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/08/1999

390 Organometallics, Vol. 18, No. 3, 1999
Benet et al.
Ta ble 1. Com p a r ison of Seleted NMR Ch em ica l Sh ift Da ta for P er tin en t CH(P P h 2)2- a n d
2-{(Me3Si)2C}-C5H4N-Con ta in in g Com p ou n d s (298 K, 5.872 T)
CH(PPh2)2, δ 2-{(Me3Si)2HC}-C5H4N, δ
1H 13C
compound
CH2(PPh2)2
Li(Et2O)‚CH(PPh2)2
4
1H
13C
31P
solvent
2
1
2.78, t, J (31P-1H) 4 Hz
28.85, t, J (31P-13C) 48 Hz
-21.0
-2.9
-
-
-
C6D6
C6D6
C6D6
C4D8O
C6D6
C6D6
2.16, bs
18.14, bs
-
-
-
-
2
1
3.81b, d, J (31P-1H) 6 Hz
22.80, t, J (31P-13C) 105 Hz
1.1, -11.0
-0.1, -11.1
-0.4, -10.7
-
38.10
39.69
28.70d
33.30
1
-
24.61, t, J (31P-13C) 104 Hz
2
1
5a
3.44b, d, J (31P-1H) - Hzc
26.79, t, J (31P-13C) 114 Hz
2-{(Me3Si)2HC}-C5H4N
-
-
1.70
Reference 2. Internally referenced to minor CH2(PPh)2 impurity. c Barely resolvable doublet. C4D8O, 245 K, 9.395 T.
a
b
d
ambient temperature: the homoleptic bis-aryl analogue
ported.23,29 However, also reported were unsuccessful
attempts at the preparation of both [Ge(2-{(Me3Si)2C}-
C5H4N)2] and [Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3).23 In our
laboratory, we have succeded in preparing both of these
materials in high yield, although the preparation and
molecular structure of the former, dialkyl Ge(II) deriva-
tive has since been reported by others.30
Sn(C6H2-2,4,6-Pri ) trimerizes in solution above -30 °C
3 2
to yield the structurally characterized cyclic trimer
[Sn(C6H2-2,4,6-Pri ) ] 7,2,24 crystals of which have been
3 2
shown to undergo a solid-state phase transition from
orthorhombic, space group Pna21 at 220 K to monoclinic,
space group P21/c for the same crystals at 298 K.
Building on the work presented in our earlier com-
munication,22 we now report in full the preparation,
characterization and crystal structure of [Sn(2-
{(Me3Si)2C}-C5H4N){Sn(SiMe3)3}] (1) and its novel, iso-
structural Si analogue, [Sn(2-{(Me3Si)2C}-C5H4N)-
{Si(SiMe3)3}] (2). 1 is the first structurally characterized
compound to contain a bond between divalent Sn and
tetravalent Sn.25 Its 119Sn{1H} NMR spectrum permits
the first measurement of 1J coupling between Sn atoms
of different valence. Compound 2 is only the second
structurally characterized heteroleptic stannylene con-
taining a silyl substituent and is of particular interest
since the central divalent Sn is bound to an element
more electropositive than carbon: the other example,
[Sn{C6H3-2,6-(NMe2)2}(Si{(-NCH2But)2-1,2-C6H4}{C6H3-
2,6-(NMe2)2})], obtained in good yield by the treatment
of [Si{(-NCH2But)2-1,2-C6H4}]26 with [Sn{C6H3-2,6-
(NMe2)2}2]27 was very recently reported.28 Continuing
our program of study into the versatility of group 14
element carbene analogues in the preparation of het-
erometallic (group 14/group 8) clusters, we have now
begun to explore the utility of Ge(II) species. Thus, we
now report the preparation, characterization, and mo-
lecular structure of the heteroleptic germylene [Ge(2-
{(Me3Si)2C}-C5H4N)Cl] (3) and demonstrate its utility
as a precursor to further heteroleptic compounds of
Ge(II) by presenting its dialkyl derivative, [Ge(2-
{(Me3Si)2C}-C5H4N){CH(PPh2)2}] (4). The preparation
and molecular structure of [Sn(2-{(Me3Si)2C}-C5H4N)R]
(R ) Cl) was first reported in a preliminary communica-
tion a decade ago and along with the R ) N(SiMe3)2 or
2-{(Me3Si)2C}-C5H4N derivatives, was among the first
heteroleptic mononuclear Sn(II) compounds to be re-
Exp er im en ta l Section
Equ ip m en t. All experiments were carried out under an
atmosphere of argon. All chemical manipulations were per-
formed, either using standard Schlenk line techniques employ-
ing a dual manifold vacuum/argon line fitted exclusively with
Young’s type greaseless taps, or in a Miller-Howe glovebox
under an atmosphere of dinitrogen operating at <1 ppm O2
and <5 ppm H2O. Solvents were predried by distillation over
the appropriate drying agent under an atmosphere of dinitro-
gen for 72 h prior to use, freeze-thaw degassed, and stored
in ampules under dinitrogen or argon, either in the presence
of a potassium mirror (C6D6, toluene, Et2O and hexane) or a
sodium mirror (thf).
Mu ltin u clea r NMR Sp ectr oscop y. 1H, 13C{1H}, 29Si{1H},
31P{1H}, and 119Sn{1H} NMR spectra were recorded using a
Bruker DPX instrument (operating at a field strength of 5.872
T) with observational frequencies of 250.00, 62.86, 49.662,
101.202, and 93.181 MHz, respectively. 1H, 13C{1H}, and
29Si{1H} spectra were referenced externally to SiMe4, 31P{1H}
spectra were referenced externally to 85% H3PO4 solution, and
119Sn{1H} spectra were referenced externally to SnMe4. Low
resolution CI mass spectra were recorded on a Fisons “Au-
tospec” double focusing mass spectrometer.
X-r a y Cr ysta llogr a p h y. A crystal of 1 was mounted at the
end of a glass fiber under Perfluorpolyether RS 3000 and
quickly placed in a cryostream at 160 K. The intensities were
collected using synchrotron radiation (λ ) 0.6879) and a
Siemens SMART CCD area detector system at the SRS, station
9.8, Daresbury. The structure was solved by direct methods
using SHELXL 97. Data were corrected for adsorption using
SADABS. Hydrogen atoms were included in the calculated
positions for final refinement cycles. All non-hydrogen atoms
were refined anisotropically. The structures of 2-4 were
determined from image plate X-ray diffraction data from a Mar
180 cm plate using ambient temperature data, capillary-
mounted crystals and Mo KR sealed tube radiation with a
graphite monochromator (λ ) 0.710 73 Å). 95 images having
a 2° rotation per image were collected using a data collection
time of 5 min per frame and a crystal-to-plate distance of 75
mm. The XDS program31 was used for data processing and
merged together with MARSCALE, the MarResearch version
of XSCALE.31 Final cell constants were determined using the
GLOREF routine within XDS, using refined diffraction spots
(23) J olly, B. S.; Lappert, M. F.; Engelhardt, L. M.; White, A. H.;
Raston, C. L. J . Chem. Soc., Dalton Trans. 1993, 2653.
(24) Brady, F. J .; Cardin, C. J .; Cardin, D. J .; Convery, M. A.;
Devereux, M. M.; Lawless, G. A. J . Organomet. Chem. 1991, 241, 199.
(25) “The reaction of o-(diphenylphosphine)phenylbromomagnesium
with tin(II) chloride leads to the formation of a tin(II)-tin(IV) contain-
ing compound...”; although no structural data are provided, 31P{1H}
and 119Sn{1H} NMR spectroscopic data, in addition to 119Sn Mo¨ssbauer
spectroscopic data, support the proposed formulism. J urkschat, K.;
Abicht, H.-P.; Tzschach, A.; Mahieu, B. J . Organomet. Chem. 1986,
309, C47-C50.
(26) Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Heinicke, J .;
Boese, R.; Blaser, D. J . Organomet. Chem. 1996, 521, 211.
(27) Drost, C.; Hitchcock, P. B.; Lappert, M. F.; Pierssens, L. J . M.
Chem. Commun. 1997, 1141.
(28) Drost, C.; Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F. Chem.
Commun. 1997, 1845.
(29) Engelhardt, L. M.; J olly, B. S.; Lappert, M. F.; Raston, C. L.;
White, A. H. J . Chem. Soc., Chem. Commun. 1988, 336.
(30) Ossig, G.; Meller, A.; Bro¨nneke, C.; Mu¨ller, O.; Scha¨fer, M.;
Herbst-Irmer, R. Organometallics 1997, 16, 2116.
(31) Kabsch, W. J . Appl. Crystallogr. 1993, 26, 795.

Heteroleptic Stannylenes and Germylenes
Organometallics, Vol. 18, No. 3, 1999 391
Ta ble 2. Su m m a r y of Cr ysta l Da ta a n d In ten sity Collection P a r a m eter s for 1 a n d 2
1
2
empirical formula
M
C
21H49NSi5Sn2
C21H49NSi6Sn
602.84
693.44
temperature/K
habit
cryst syst
space group
unit cell dimens
a/Å
160(2)
293(2)
red needles
orthorhombic
Pbca
red needles
monoclinic
P21/n
17.064(3)
17.759(5)
21.585(3)
90
90
90
6541(2)
8
1.408
1.720
2816
11.795(5)
9.344(4)
31.394(8)
90
91.84
90
3458(3)
4
1.158
0.956
1264
b/Å
c/Å
R/deg
â/deg
γ/deg
volume/Å3
Z
Dc/Mg m-3
µ/mm-1
F(000)
data collection
θ range/deg
index ranges, hkl
no. of reflcns collcd
no. of indep reflcns
structure refinement
no. of params refined
final R, R′ indices (observed data)
Goodness-of-fit on F2
1.83 to 27.13
-17 to 16, -23 to 5, -26 to 26
22087
2.54 to 23.19
0 to 11, 0 to 10, -34 to 34
10547
6241 [R(int) ) 0.0523]
3767 [R(int) ) 0.0345]
full-matrix least-squares on all F2
full-matrix least-squares on all F2
263
263
0.0308, 0.0866
0.648
0.0448, 0.1158
1.093
Ta ble 3. Atom Coor d in a tes (×104) a n d Equ iva len t
Ta ble 4. Atom Coor d in a tes (× 104) a n d Equ iva len t
Isotr op ic Disp la cem en t P a r a m eter s (Å2 × 103) for 1
Isotr op ic Disp la cem en t P a r a m eter s (Å2 × 103) for 2
x
y
z
U(eq)
x
y
z
U(eq)
Sn(1)
Sn(2)
Si(1)
Si(2)
Si(3)
Si(4)
Si(5)
N(1)
C(1)
C(2)
C(3)
C(4)
1241(1)
1893(1)
932(1)
2257(1)
1166(1)
1616(1)
3356(1)
316(2)
-309(2)
-622(2)
-285(2)
344(2)
452(1)
1663(1)
-74(1)
1164(1)
1223(1)
3087(1)
1531(1)
1257(1)
1674(2)
2182(2)
2259(2)
1817(2)
1311(1)
776(1)
3745(1)
4457(1)
2281(1)
2450(1)
5438(1)
4344(1)
4690(1)
3358(1)
3510(1)
3108(1)
2530(1)
2369(1)
2791(1)
2712(1)
2212(2)
1492(2)
2684(2)
2790(2)
1590(1)
2698(1)
5443(2)
4751(2)
4069(2)
4326(4)
5014(2)
3653(2)
6151(2)
5262(2)
5632(2)
26(1)
23(1)
30(1)
29(1)
31(1)
30(1)
30(1)
27(1)
34(1)
39(1)
36(1)
31(1)
24(1)
23(1)
53(1)
52(1)
43(1)
45(1)
45(1)
34(1)
53(1)
51(1)
40(1)
127(3)
73(2)
89(2)
57(1)
47(1)
52(1)
Sn
9384(1)
11527(2)
7644(2)
7515(2)
9652(2)
5937(2)
7656(2)
12224(8)
10765(4)
10456(6)
7165(10)
11022(5)
5686(8)
11972(8)
5943(8)
10473(8)
11233(7)
8922(8)
12802(7)
11770(7)
6184(11)
8398(8)
10823(8)
12132(8)
6395(8)
9141(8)
4649(7)
8564(13)
8075(19)
4486(1)
5416(2)
2644(2)
3404(2)
3432(2)
3418(2)
98(2)
1108(1)
1790(1)
929(1)
47(1)
53(1)
43(1)
63(1)
59(1)
61(1)
67(1)
86(3)
48(1)
42(2)
110(4)
43(2)
107(3)
90(3)
91(3)
84(3)
71(2)
105(3)
82(2)
67(2)
159(6)
105(3)
90(3)
82(3)
100(3)
92(3)
108(3)
182(7)
244(12)
Si(1)
Si(4)
Si(3)
Si(2)
Si(5)
Si(6)
C(3)
N
204(1)
2213(1)
1237(1)
895(1)
1378(3)
1061(1)
1723(2)
169(3)
1488(2)
1756(3)
948(3)
1347(3)
2737(2)
797(2)
-43(2)
2129(3)
1650(2)
748(5)
2242(3)
2033(3)
1266(2)
-142(2)
2190(3)
872(3)
636(8)
2707(5)
3875(6)
536(9)
2684(6)
2467(11)
704(9)
C(0)
C(6)
C(1)
C(9)
C(4)
C(7)
C(8)
C(5)
C(10)
C(11)
C(2)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(5)
C(6)
C(7)
C(8)
643(2)
1299(2)
1715(2)
562(3)
-799(2)
164(2)
5402(8)
3647(9)
1736(8)
3154(12)
4864(9)
1632(7)
-562(10)
4676(11)
7023(8)
5999(9)
2424(11)
1533(9)
3060(12)
-542(11)
-838(10)
C(9)
80(2)
-515(2)
594(2)
1170(2)
2162(2)
2002(2)
528(2)
1970(2)
3621(2)
3406(2)
3358(2)
1805(2)
1215(2)
239(2)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
3064(2)
2381(2)
2363(2)
3596(3)
3661(2)
3966(2)
2537(3)
1026(3)
1041(4)
1329(3)
101(2)
452(5)
1394(4)
1459(3)
(Figure 1, Figure 2, Figure 3, and Figure 4) were drawn using
collected over 190° of rotation. The structure was solved using
the direct methods routine in SHELXS and refined using the
SHELX96 version of SHELXL. Hydrogen atoms were placed
in calculated positions and the final cycles of refinement were
full-covariance least squares. Data collection and structure
refinement parameters are shown in Table 2 (1 and 2) and
Table 7 (3 and 4). The lower precision of 4 is due to crystal
decay during data collection, corrected for by the scaling in
the CORRECT step of XDS. Atomic coordinates for 1-4 are
shown in Tables 3, 4, 8, and 9, respectively. Important
intramolecular distances and angles for 1-4 are shown in
Tables 5, 6, 10, and 11, respectively. The structure plots
the ORTEP-3 for Windows program.32
Ma ter ia ls. LiBun (2.5 mol dm-3 in hexane), 2-MeC5H4N,
CH2(PPh2)2, SiMe3Cl, SiCl4, GeCl4, SnHBun3, SnCl2 (97%),
SnCl4, and Li wire were purchased from Aldrich Chemical Co.
and used as received. The Li reagents, [Li(tmeda)‚(2-
{(Me3Si)2C}-C5H4N)],33 [Li(thf)3‚Sn(SiMe3)3],34 [Li(thf)3‚Si-
(32) ORTEP-3 for Windows (32-bit version, 1.04â, build date 05-01-
98) supplied by Dr L. J . Farrugia, University of Glasgow (louis@
chem.gla.ac.uk).
(33) Papasergio, R. I.; Skelton, B. W.; Twiss, P.; White, A. H.; Raston,
C. L. J . Chem. Soc., Dalton Trans. 1990, 1161.

392 Organometallics, Vol. 18, No. 3, 1999
Benet et al.
Ta ble 5. Selected Dista n ces (Å) a n d An gles (d eg)
for 1 [Estim a ted Sta n d a r d Devia tion s (Esd s) in
P a r en th eses]
Distances
Sn(1)-N(1)
Sn(1)-C(6)
Sn(1)-Sn(2)
2.288(2)
2.304(2)
2.8689(5)
Sn(2)-Si(3)
Sn(2)-Si(4)
Sn(2)-Si(5)
2.5770(8)
2.5833(10)
2.5585(10)
Angles
N(1)-Sn(1)-C(6)
N(1)-Sn(1)-Sn(2)
61.36(9) Si(3)-Sn(2)-Si(4)
106.63(3)
106.25(3)
106.71(3)
89.68(6) Si(3)-Sn(2)-Si(5)
C(6)-Sn(1)-Sn(2) 108.29(6) Si(4)-Sn(2)-Si(5)
Sn(1)-Sn(2)-Si(3)
Sn(1)-Sn(2)-Si(5) 114.54(2) C(6)-C(5)-N(1)
91.50(2) Sn(1)-Sn(2)-Si(4) 127.76(2)
111.8(2)
Ta ble 6. Selected Dista n ces (Å) a n d An gles (d eg)
for 2 [Estim a ted Sta n d a r d Devia tion s (Esd s) in
P a r en th eses]
Distances
F igu r e 2. Molecular structure of [Sn(2-{(Me3Si)2C}-
C5H4N){Si(SiMe3)3}] (2) (thermal ellipsoids drawn at the
50% probability level).
Sn-N
2.335(5)
2.345(6)
2.7236(18)
Si(4)-Si(3)
Si(4)-Si(5)
Si(4)-Si(6)
2.386(2)
2.374(3)
2.381(2)
Sn-C
Sn-Si(4)
Angles
N-Sn-C
61.36(18)
93.43(13)
113.49(15)
91.88(7)
Sn-Si(4)-Si(3)
Sn-Si(4)-Si(5)
Sn-Si(4)-Si(6)
Si(5)-Si(4)-Sn
C-C(1)-N
91.88(7)
111.53(8)
129.43(10)
111.53(8)
112.5(5)
N-Sn-Si(4)
C-Sn-Si(4)
Si(3)-Si(4)-Sn
Si(6)-Si(4)-Sn
129.43(10)
F igu r e 3. Molecular structure of [Ge(2-{(Me3Si)2C}-
C5H4N)Cl] (3) showing the two independent molecules
(thermal ellipsoids drawn at the 50% probability level).
F igu r e 1. Molecular structure of [Sn(2-{(Me3Si)2C}-
C5H4N){Sn(SiMe3)3}] (1) (thermal ellipsoids drawn at the
50% probability level).
(SiMe3)3],35,36 and Li(Et2O)‚CH(PPh2)2,37 were prepared accord-
ing to literature methods as was the Sn(II) precursor [Sn(2-
{(Me3Si)2C}-C5H4N)Cl].23 [Ge(2-{(Me3Si)2C}-C5H4N)2] can be
prepared according to published methods also.30
Syn th esis of [GeCl2‚d iox]. To a Schlenk tube containing
GeCl4 (16.00 mL, 30.00 g, 139.93 mmol), Et2O (90 mL), hexane
(90 mL), 1,4-dioxane (30 mL), and a stir-bar was added a
solution of SnHBun3 (38.00 mL, 40.73 g, 139.93 mmol) in Et2O
(50 mL) over a 20 min period; a white precipitate formed. The
mixture was stirred overnight and then refluxed for 48 h. The
solution was filtered, and remaining white microcrystalline
material washed with hexane (2 × 60 mL) and then dried in
vacuo. Yield 18.38 g (79.36 mmol, 57%).
F igu r e 4. Molecular structure of [Ge(2-{(Me3Si)2C}-
C5H4N){CH(PPh2)2}] (4) (thermal ellipsoids drawn at the
50% probability level).
Syn th eses of [E(2-{(Me3Si)2C}-C5H4N)R] (1-4). [Sn (2-
{(Me3Si)2C}-C5H4N){Sn (SiMe3)3}] (1). To a Schlenk tube
containing [Sn(2-{(Me3Si)2C}-C5H4N)Cl] (3.99 g, 10.21 mmol),
a stir-bar, and Et2O (40 mL) was added with stirring a solution
of [Li(thf)3‚Sn(SiMe3)3]34 (5.73 g, 10.21 mmol) over a 5 min
period, resulting in an immediate change from yellow/orange
to red. The mixture was stirred for a further 16 h, the Et2O
removed in vacuo, and the product extracted from the LiCl
byproduct with hexane (3 × 40 mL). The hexane was removed
in vacuo to afford 6.23 g of 1 as a pyrophoric dark red powder
(8.99 mmol, 88% yield). Crystals of 1 suitable for an X-ray
diffraction study were grown from a saturated hexane solution.
(34) Cardin, C. J .; Cardin, D. J .; Coles, S.; Constantine, S. P.; Rowe,
J . R.; Teat, S. J . J . Organomet. Chem. 1998, in press.
(35) Gutekunst, G.; Brook, A. G. J . Organomet. Chem. 1982, 225,
1.
(36) Heine, A.; Herbst-Irmer, R.; Sheldrick, G. M.; Stalke, D. Inorg.
Chem. 1993, 32, 2694.
(37) Issleib, V. K.; Abicht, H. P. J . Prakt. Chem. 1970, B132, 456.

Heteroleptic Stannylenes and Germylenes
Organometallics, Vol. 18, No. 3, 1999 393
Ta ble 7. Su m m a r y of Cr ysta l Da ta a n d In ten sity Collection P a r a m eter s for 3 a n d 4
3
4
empirical formula
M
C
24H44Ge2N2Cl2Si4
C37H43GeNP2Si2
692.43
689.05
temperature/K
habit
cryst syst
space group
unit cell dimens
a/Å
293(2)
293(2)
yellow needles
triclinic
yellow needles
monoclinic
P21/n
P1h
15.364(5)
14.451(5)
17.309(6)
90
112.73(6)
90
3544.6
4
1.291
10.766(5)
14.338(6)
15.841(6)
68.83(6)
86.34(6)
68.44(6)
2114
b/Å
c/Å
R/deg
â/deg
γ/deg
volume/Å3
Z
2
Dc/Mg m-3
1.088
0.879
724
µ/mm-1
1.997
1424
F(000)
data collection
θ range/deg
index ranges, hkl
no. of reflcns collcd
no. of indep reflcns
structure refinement
no. of params refined
final R, R′ indices (observed data)
Goodness-of-fit on F2
2.55 to 25.91
0 to 18, 0 to 17, -19 to 18
9747
3.00 to 23.25
0 to 11, -14 to 15, -17 to 17
8450
5662 [R(int) ) 0.0574]
5484 [R(int) ) 0.0677]
full-matrix least-squares on all F2
full-matrix least-squares on all F2
308
388
0.0595, 0.1820
1.175
0.0916, 0.3132
1.067
Ta ble 8. Atom Coor d in a tes (×104) a n d Equ iva len t
MHz), δ 897 [1J (119Sn-119Sn) ) 6746 Hz, 1J (117Sn-119Sn) )
6448 Hz], -502 [1J (119Sn-119Sn) ) 6765 Hz, 1J (117Sn-119Sn)
) 6467 Hz]. Elem. Anal. for C21H49Si5NSn2, found (calcd): C,
36.63 (36.37); H, 6.92 (7.12); N, 2.13 (2.02).38
Isotr op ic Disp la cem en t P a r a m eter s (Å2 × 103) for 3
x
y
z
U(eq)
Ge(1)
Ge(2)
Si(3)
Si(4)
Cl(1)
Si(1)
Si(2)
Cl(2)
N(2)
C(13)
C(14)
N(1)
C(1)
C(5)
C(21)
C(2)
C(6)
C(15)
C(24)
C(4)
4953(1)
5206(1)
4592(1)
3295(1)
3595(1)
6958(1)
5446(1)
6448(1)
4358(3)
4172(3)
3845(4)
5616(3)
5923(4)
6222(5)
3635(5)
6100(4)
5673(4)
3141(4)
2089(4)
6701(4)
6658(4)
4212(5)
3132(5)
2987(5)
6694(5)
3749(6)
3519(5)
5600(5)
4977(6)
8083(4)
4604(6)
4820(7)
7145(6)
6398(6)
3968(1)
6557(1)
8650(1)
7630(1)
3692(1)
2985(2)
1892(2)
6829(2)
6038(4)
7527(4)
6823(4)
4535(4)
3033(4)
5339(5)
9554(5)
3758(5)
5301(5)
6859(5)
7974(6)
4536(6)
3747(5)
5291(5)
6459(7)
6097(7)
2146(6)
8450(7)
5293(6)
9128(5)
8458(7)
2667(7)
1425(6)
2009(8)
4155(7)
1003(7)
2308(1)
2990(1)
3602(1)
1899(1)
1158(1)
3146(1)
1602(1)
4238(1)
3575(3)
3027(3)
3476(3)
1572(3)
2106(4)
702(4)
3296(5)
1565(3)
1163(4)
3798(4)
1816(4)
667(4)
1098(4)
3972(4)
1374(5)
4206(5)
3859(4)
1316(4)
4288(4)
3377(6)
4758(5)
3023(4)
2061(6)
446(5)
58(1)
56(1)
57(1)
54(1)
73(1)
62(1)
68(1)
85(1)
51(1)
47(1)
48(1)
56(1)
51(1)
66(2)
79(2)
51(1)
62(2)
63(2)
72(2)
71(2)
64(2)
66(2)
93(3)
81(2)
83(2)
89(3)
77(2)
83(2)
103(3)
87(2)
91(3)
113(3)
98(3)
115(3)
[Sn (2-{(Me3Si)2C}-C5H4N){Si(SiMe3)3}] (2). To a Schlenk
tube containing [Sn(2-{(Me3Si)2C}-C5H4N)Cl] (4.70 g, 12.03
mmol), a stir-bar, and Et2O (80 mL), cooled to -78 °C using a
dry ice/acetone slush bath, was added a stirred slurry of
[Li(thf)3‚Si(SiMe3)3] (5.79 g, 12.30 mmol) over a 30 min period.
The red mixture was allowed to warm slowly to ambient
temperature (ca. 8 h) and stirred for a further 16 h. The Et2O
was removed in vacuo, the product extracted with hexane (1
× 80 mL). Concentration of the hexane solution in vacuo
followed by cooling with liquid N2 and filtration afforded 4.17
g of 2 as a red pyrophoric powder (6.92 mmol, 56% yield). Red
needles of 2 were grown from a concentrated Et2O solution.
Da ta for 2: 1H NMR (C6D6, 298 K, 250.00 MHz), δ 7.85 (d,
1 H), 6.86 (t, 1 H), 6.32 (d, 1 H), 6.23 (t, 1 H), 0.44 (s, 27 H),
0.29 (s, 9 H), 0.24 (s, 9 H); 13C{1H} NMR (C6D6, 298 K, 62.86
MHz),
δ 173.40, 147.82, 137.17, 127.01, 118.54, 38.95
[C{Si(CH3)3}2], 4.99 [Si{Si(CH3)3}3], 3.50 [C{Si(CH3)3}2], 1.63
[C{Si(CH3)3}2]; 119Sn{1H} NMR (C6D6, 298 K, 93.18 MHz), δ
C(3)
876. MS (CI, 70 eV) m/z 603 M+., 588 M•+ - Me, 356 M•+
-
C(18)
C(23)
C(16)
C(9)
C(22)
C(17)
C(20)
C(19)
C(7)
Si(SiMe3)3. Elem. Anal. for C21H49Si6NSn, found (calcd): C,
41.11 (41.84); H, 8.14 (8.19); N, 2.84 (2.32).38
[Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3). To a Schlenk tube con-
taining [GeCl2‚diox] (4.10 g, 17.70 mmol), a stir-bar and Et2O
(50 mL), cooled to -78 °C using a dry ice/acetone slush bath,
was added a stirred slurry of [Ge(2-{(Me3Si)2C}-C5H4N)2] (9.55
g, 17.51 mmol) also in Et2O (70 mL) over a 45 min period. After
complete addition of the [Ge(2-{(Me3Si)2C}-C5H4N)2], the thick
pale yellow slurry was allowed to warm slowly to ambient
temperature (ca. 8 h) and stir overnight. The Et2O was
removed in vacuo, and the product was extracted with warm
hexane (3 × 60 mL). As the solution was filtered, large yellow
crystals of 3 were seen to form and these were isolated (4.22
g, 12.25 mmol) by removing the hexane solution into the second
Schlenk tube via cannula. The hexane was removed in vacuo
C(11)
C(12)
C(8)
3642(5)
1772(7)
C(10)
Da ta for 1: 1H NMR (C6D6, 298 K, 250.00 MHz), δ 7.75 (dd,
1 H), 6.88 (td, 1 H), 6.25 (m, 2 H), 0.49 [s, 27 H, J (119,117Sn-
3
1H) ) 32 Hz], 0.28 (s, 9 H), 0.23 (s, 9 H); 13C{1H} NMR (C6D6,
298 K, 62.86 MHz), δ 173.30, 148.23, 136.81, 127.10, 118.70,
35.60, 5.99 [2J (119,117Sn-13C) ) 38 Hz] 3.23 [1J (29Si-13C) ) 48
Hz], 1.26 [1J (29Si-13C) ) 46 Hz]; 29Si{1H} NMR (C6D6, 298 K,
49.662 MHz), δ 0.2 [2J (119,117Sn-29Si) ) 21 Hz], -3.5 [2J -
(38) Similarly poor elemental analysis values for N were found for
[Sn(2-{(Me3Si)2C}-C5H4N)R] {R ) (2-{(Me3Si)2C}-C5H4N) or Cl}: 5.2
(4.7) or 4.1 (4.7) and 3.4 (3.6) or 4.0 (3.6), respectively. J olly, B. S.;
Lappert, M. F.; Engelhardt, L. M.; White, A. H.; Raston, C. L. J . Chem.
Soc., Dalton Trans. 1993, 2653.
(
119,117Sn-29Si) ) 13 Hz], -4.7 [1J (119Sn-29Si) ) 208 Hz,
1J (117Sn-29Si) ) 199 Hz]; 119Sn{1H} NMR (C6D6, 298 K, 93.18

394 Organometallics, Vol. 18, No. 3, 1999
Benet et al.
Ta ble 9. Atom Coor d in a tes (×104) a n d Equ iva len t
Ta ble 11. Selected Dista n ces (Å) a n d An gles (d eg)
for 4 [Estim a ted Sta n d a r d Devia tion s (Esd s) in
P a r en th eses]
Isotr op ic Disp la cem en t P a r a m eter s (Å2 × 103) for 4
x
y
z
U(eq)
Distances
Ge(1)
P(1)
P(2)
7191(1)
5249(2)
8082(2)
7048(9)
8272(3)
9344(3)
8761(9)
9068(7)
9661(10)
7465(10)
7489(11)
5218(9)
10105(12)
4371(9)
6486(10)
10987(12)
11013(10)
9679(11)
6402(11)
8190(13)
8149(12)
11645(11)
4201(12)
3821(11)
5978(15)
6090(12)
10716(15)
6216(13)
4946(14)
7844(16)
5978(14)
7905(14)
4214(11)
4094(14)
7831(18)
3131(12)
7700(20)
6902(16)
6677(18)
3519(15)
6747(16)
9592(18)
3004(14)
7938(1)
6529(2)
5565(2)
6417(7)
9192(2)
6647(2)
7786(7)
7548(6)
7653(7)
6309(8)
4444(8)
5396(7)
5308(8)
7688(8)
7330(8)
7366(9)
7568(9)
7440(8)
4464(9)
3500(8)
5822(10)
7429(9)
7619(9)
8689(9)
4044(10)
4889(10)
6685(12)
7872(10)
3718(10)
6406(14)
3598(11)
6664(10)
5011(9)
4174(10)
10196(10)
9600(9)
2659(11)
7413(12)
2696(12)
8520(12)
9498(11)
9420(13)
9524(12)
6333(1)
6791(2)
6177(2)
6784(6)
7211(2)
8333(2)
7197(6)
5813(5)
6459(6)
4970(7)
6465(7)
7817(6)
8176(8)
7151(7)
4611(7)
4978(8)
6390(7)
5066(7)
6014(9)
7184(8)
4358(8)
5656(8)
8044(9)
6470(9)
9344(9)
8559(8)
8992(10)
3683(8)
9335(10)
3418(10)
6282(10)
9070(8)
7809(9)
8565(11)
6030(9)
6663(11)
7467(11)
3097(9)
7041(12)
8237(12)
7844(11)
7732(15)
7540(13)
55(1)
55(1)
57(1)
52(2)
66(1)
61(1)
54(2)
55(2)
58(2)
61(2)
65(2)
59(2)
79(3)
59(2)
63(2)
75(3)
70(3)
67(3)
77(3)
82(3)
78(3)
77(3)
81(3)
76(3)
95(4)
82(3)
102(4)
81(3)
92(4)
101(4)
93(4)
87(3)
83(3)
101(4)
104(5)
89(4)
113(5)
98(4)
104(5)
102(4)
110(5)
136(7)
104(4)
P(1)-C(1)
P(1)-C(2)
P(1)-C(8)
Ge(1)-N(1)
Ge(1)-C(1)
1.883(9)
1.846(9)
1.854(10)
2.089(7)
2.097(8)
P(2)-C(1)
1.836(9)
1.841(9)
1.845(11)
2.142(9)
P(2)-C(14)
P(2)-C(20)
Ge(1)-C(26)
C(1)
Si(1)
Si(2)
C(26)
N(1)
C(27)
C(20)
C(14)
C(2)
Angles
98.7(3)
N(1)-Ge(1)-C(1)
N(1)-Ge(1)-C(26)
C(1)-Ge(1)-C(26)
C(2)-P(1)-C(8)
C(2)-P(1)-C(1)
C(8)-P(1)-C(1)
C(26)-C(27)-N(1)
P(2)-C(1)-P(1)
P(2)-C(1)-Ge(1)
P(1)-C(1)-Ge(1)
C(14)-P(2)-C(20)
C(1)-P(2)-C(14)
C(1)-P(2)-C(20)
113.3(4)
112.7(4)
111.4(4)
101.5(4)
104.9(4)
105.6(4)
66.6(3)
105.8(3)
101.1(4)
104.4(4)
103.8(4)
111.4(8)
C(32)
C(8)
C(21)
C(30)
C(28)
C(31)
C(15)
C(19)
C(25)
C(29)
C(13)
C(9)
a 30 min period. Stirring overnight resulted in an orange
solution and the formation of a substantial yellow precipitate.
The Et2O was removed in vacuo and the resulting intensely
yellow solid washed with freezing-cold hexane (2 × 60 mL). 4
was separated from the LiCl byproduct with hot toluene (50
mL) and isolated as an intensely yellow solid by removal of
the toluene in vacuo. Yield 1.72 g (2.48 mmol, 75%). Redisso-
lution in hot toluene afforded upon cooling, 4 as large intensely
yellow, X-ray quality needles which could be handled in air
for a number of minutes without any visible signs of decom-
position.
C(4)
C(3)
C(34)
C(22)
C(5)
C(24)
C(16)
C(33)
C(7)
1
Da ta for 4: H NMR (C6D6, 298 K), δ 8.15-6.06 [P(C6H5)
and C5H4N, 24 H; 6.51, d, C5H4N; 6.06, t, C5H4N], 3.81 [d, 1H,
CH(PPh2)2], 0.43 and 0.02 [s, 9H, C{Si(CH3)3}2]; 13C{1H} NMR
(C6D6, 298 K), δ 171.89 (C5H4N), 146.45 (C5H4N), 141.50-
125.64 [P(C6H5) and C5H4N], 124.71 (C5H4N), 118.44 (C5H4N),
38.10 [C{Si(CH3)3}2], 22.80 [CH(PPh2)2, t, 1J (31P-13C) ) 105
Hz], 4.07 and 1.57 [C{Si(CH3)3}2]; 13C{1H} NMR (C4D8O, 298
K), δ 173.70 (C5H4N), 148.33 (C5H4N), 141.74-129.67 [P(C6H5)
and C5H4N], 127.16 (C5H4N), 120.81 (C5H4N), 39.69
[C{Si(CH3)3}2], 24.61 [CH(PPh2)2, t, 1J (31P-13C) ) 104 Hz], 5.52
and 3.03 [C{Si(CH3)3}2]; 29Si{1H} NMR (C6D6, 298 K), δ -0.3;
31P{1H} NMR (C6D6, 298 K), δ 1.1 (s, 1 P), -11.0 (s, 1 P). MS
(CI, NH3) m/z 694 M+., 457 M•+ - (2-{(Me3Si)2C}-C5H4N), 384
CH2(PPh2)2, 310 M•+ - {2-CH(PPh2)2, 238 2-{(Me3Si)2CH}-
C5H4N. Elem. Anal. for C37H42Si2NP2Ge, found (calcd): C,
63.90 (64.27); H, 6.21 (6.12); N, 2.18 (2.02).38
C(6)
C(37)
C(10)
C(18)
C(23)
C(17)
C(12)
C(35)
C(36)
C(11)
Ta ble 10. Selected Dista n ces (Å) a n d An gles (d eg)
for 3 [Estim a ted Sta n d a r d Devia tion s (Esd s) in
P a r en th eses]
Resu lts a n d Discu ssion
Distances
Ge(1)-N(1)
Ge(1)-C(1)
Ge(1)-Cl(1)
2.082(4)
2.138(5)
2.2948(19)
Ge(2)-N(2)
Ge(2)-C(13)
Ge(2)-Cl(2)
2.075(4)
2.138(5)
2.2962(19)
The precursor to 1 and 2, [Sn(2-{(Me3Si)2C}-C5H4N)Cl],
was prepared in high yield (ca. 70%) according to the
literature method. Reaction of 2 equiv of [Li(tmeda)‚(2-
{(Me3Si)2C}-C5H4N)]33 with SnCl2 in Et2O at ambient
temperature yields [Sn(2-{(Me3Si)2C}-C5H4N)2], which
undergoes ligand redistribution with 1 equiv of SnCl2
to to afford 2 equiv of the desired material.23
Angles
N(1)-Ge(1)-C(1)
N(1)-Ge(1)-Cl(1)
67.1(2)
N(2)-Ge(2)-C(13)
66.9(2)
93.06(14)
91.89(14) N(2)-Ge(2)-Cl(2)
C(1)-Ge(1)-Cl(1) 101.86(17) C(13)-Ge(2)-Cl(2) 102.52(15)
C(1)-C(2)-N(1)
110.0(4)
C(13)-C(14)-N(2) 110.0(4)
Syn t h eses of [E (2-{(Me3Si)2C}-C5H 4N)R ] (1-4).
to afford 3 as an O2- and H2O-sensitive, yellow powder (7.35
g, 21.34 mmol) which was then washed with freezing-cold
hexane (1 × 40 mL). Combined yield of crystalline/washed 1,
9.63 g (27.95 mmol, 80%).
[Sn (2-{(Me3Si)2C}-C5H4N)(C6H2-2,4,6-P r i )] (1). Com-
3
pound 1 was prepared by the treatment of a stirred
solution of [Sn(2-{(Me3Si)2C}-C5H4N)Cl] in Et2O at -78
°C with a solution of 1 equiv of [Li(thf)3.{Sn(SiMe3)3}],
also in Et2O (Scheme 1) and was obtained as a dark red
pyrophoric powder in 88% yield. Recrystallization from
a very concentrated hexane solution produced small
dark red needles of suitable quality for crystallographic
analysis.
[Sn (2-{(Me3Si)2C}-C5H4N){Si(SiMe3)3}] (2). Com-
pound 2 was prepared in a manner analogous to that
for 1 but using [Li(thf)3‚{Si(SiMe3)3}] (Scheme 1) and
was obtained as a red pyrophoric powder in 56% yield.
1
Da ta for 3: H NMR (C6D6, 298 K), δ 7.45 (bs, 1 H), 7.03
(dt, 1 H), 6.54 (bs, 1 H), 6.40 (bt, 1 H), 0.32 (s, 18 H); 13C{1H}
NMR (C6D6, 298 K), δ 174.54 (b, C5H4N), 143.95 (b, C5H4N),
139.66 (C5H4N), 126.10 (C5H4N), 119.65 (C5H4N), 39.24 [b,
C{Si(CH3)3}2], 1.61 [b, C{Si(CH3)3}2]; 29Si{1H} NMR (C6D6, 298
K), δ 0. Elem. Anal. for C12H22Si2NGeCl, found (calcd): C,
39.97(41.83); H, 6.30 (6.44), N, 4.50 (4.06).38
[Ge(2-{(Me3Si)2C}-C5H4N){CH(P P h 2)2}] (4). To a Schlenk
tube containing [Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3) (1.30 g, 3.77
mmol), a stir-bar, and Et2O (50 mL) was added a stirred slurry
of Li(Et2O)‚CH(PPh2)2 (1.53 g, 3.30 mmol), also in Et2O, over

Heteroleptic Stannylenes and Germylenes
Organometallics, Vol. 18, No. 3, 1999 395
aromatic 1H environments of 2-{(Me3Si)2C}-C5H4N are
observed at δ 7.85, 6.98, 6.68, and 6.36. The observation
of two chemically distinct SiMe3 1H environments for
this ligand, at δ 0.33 and 0.04, indicates the persistence
of the formally coordinate N-Sn bond in solution (at
ambient temperature) thereby preventing rotation of the
bidentate ligand about the C-Sn bond which would
render the two SiMe3 groups equivalent. Additionally,
it is presumably the longer (Me3Si)3Sn-Sn bond (al-
lowing free rotation) compared with the corresponding
(Me3Si)2N-Sn bond in [Sn(2-{(Me3Si)2C}-C5H4N)-
{N(SiMe3)2}] that results in the equivalence of the
Sn(SiMe3)3 ligand 1H (and 13C) environments in 1 at
Sch em e 1. P r ep a r a tion of
[Sn (2-{(Me3Si)2C}-C5H4N)R] [R ) Sn (SiMe3)3 (1) or
Si(SiMe3)3 (2)]
1
ambient temperature. In agreement with the H NMR
spectrum, two distinct 13C resonances are observed for
the SiMe3 groups of the 2-{(Me3Si)2C}-C5H4N ligand, at
δ 2.49 and 2.30. The 29Si{1H} NMR spectrum exhibits
three resonances. The resonance at δ -4.7 is assigned,
on the basis of its 1J (119Sn-29Si) and 1J (117Sn-29Si)
satellites (208 and 199 Hz respectively) and its greater
intensity, to the SiMe3 groups of the Sn(SiMe3)3 ligand.
Cooling of an Et2O solution of 2 to -30 °C afforded dark
red needles suitable for crystallographic analysis.
[Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3). Compound 3 was
prepared in high yield (80%) from the reaction of [Ge(2-
{(Me3Si)2C}-C5H4N)2] with 1 equiv of [GeCl2‚diox] (ca.
1% excess) in Et2O at ambient temperature (Scheme 2).
This route is identical to the preferred preparation of
the Sn analogue,23 however, during extraction of 3 from
residual [GeCl2‚diox] using hot hexane, small amounts
of a white precipitate were observed: 1H, 13C{1H}, and
29Si{1H} NMR spectra of the crude 3 extract (i.e., before
washing with hexane at just above its freezing point)
revealed the presence of 2-{(Me3Si)2HC}-C5H4N. Thus,
3 appears to be less thermally robust in solution than
its Sn analogue.
[Ge(2-{(Me3Si)2C}-C5H4N){CH(P P h 2)2}] (4). Com-
pound 4 was prepared by the treatment of a stirred
solution of [Ge(2-{(Me3Si)2C}-C5H4N)Cl] (ca. 14% excess)
in Et2O at ambient temperature with a stirred slurry
of Li(Et2O)‚CH(PPh2)2, also in Et2O and was obtained
as an intensely yellow powder in 75% yield (Scheme 2).
[As was found for 5, a small amount of “free” CH2(PPh2)2
was shown to be present by 1H and 31P{1H} NMR
spectroscopies]. Redissolution of this solid in hot toluene
afforded upon cooling 4 as intensely yellow needles
which did not show any visible signs of decomposition
upon exposure to air for a period of minutes.
2
The two resonances at δ 0.2 and -3.5, with J (119,117Sn-
29Si) satellites of 21 and 13 Hz respectively, are assigned
to the chemically distinct SiMe3 groups of the 2-
{(Me3Si)2C}-C5H4N ligand. The 119Sn{1H} NMR spec-
trum of 2 comprises two sharp singlet resonances, at δ
897 and -502. The high-frequency resonance is to
higher frequency compared with the corresponding
resonances for other derivatives of divalent Sn for which
119Sn NMR chemical shift data have been reported, e.g.
[Sn(2-{(Me3Si)2C}-C5H4N){CH(PPh2)2}] at δ 397 and
[Sn(2-{(Me3Si)2C}-C5H4N)(C6H2-2,4,6-Pri )] at δ 474.2
3
Similarly, the other resonance is to much higher fre-
quency than that for the Li precursor 1 (C6D6, δ -878).34
1
Both resonances exhibit well-resolved J (119Sn-119Sn)
and 1J (117Sn-119Sn) satellites, unsymmetrically posi-
tioned about the 119Sn resonance being observed. This
is a result of isotope shifts (the satellite nuclei are bound
to the Sn isotopes 117Sn and 119Sn and the central
resonance corresponds to those bound to nonmagnetic
nuclei) and is obvious in this instance owing to the large
couplings involved. Thus, the resonance at δ 896.53 has
119Sn satellites with a 1J coupling of 6746 Hz and
chemical shift of δ 897.44, and 117Sn satellites with a
1J coupling of 6448 Hz and chemical shift of δ 896.64.
The corresponding values for the resonance at δ -501.84
are 6765 Hz and δ -501.68, 6467 Hz and δ -500.71,
respectively.
Mu ltin u clea r NMR Sp ectr oscop ic Da ta for [E(2-
{(Me3Si)2C}-C5H 4N)R ] (1-4). [Sn (2-{(Me3Si)2C}-
1
C5H4N){Sn (SiMe3)3}] (1). The H NMR spectrum of 1
in C6D6 at ambient temperature exhibits resonances
with characteristic chemical shifts and integral values
for both ligands. The resonances corresponding to the
Sch em e 2. P r ep a r a tion of [Ge(2-{(Me3Si)2C}-C5H4N)R] [R ) Cl (3) or CH(P P h 2)2 (4)]

396 Organometallics, Vol. 18, No. 3, 1999
Benet et al.
[Sn (2-{(Me3Si)2C}-C5H4N){Si(SiMe3)3}] (2). The 1H
and 13C{1H} NMR spectra of 2 in C6D6 at ambient
temperature are essentially the same as those for 1 and
thus the notion that the formally coordinate N-Sn bond
persists in solution at ambient temperature for 2 also
is confirmed: similarly, resonances confirming only
single 1H and 13C environments for the Si(SiMe3)3 ligand
were observed. The resonance corresponding to the C
atom of the 2-{(Me3Si)2C} moiety appears at δ 38.95, to
higher frequency compared with that for 1 (δ 35.60), but
to lower frequency compared with that for the parent
chloro-species (δ 43.34). The 29Si{1H} NMR spectrum
exhibits only three resonances: these are assigned on
the basis of their integral values and by analogy with
the assignments made for 1. The resonance at δ -5.8,
at δ 1.61. The 29Si{1H} NMR spectrum exhibits a single
broad resonance at δ 0.
[Ge(2-{(Me3Si)2C}-C5H4N){CH(P P h 2)2}] (4). The
1H NMR spectrum of 4 in C6D6 at ambient temperature
exhibits reasonably sharp resonances with chemical
shifts and integral values characteristic of the two
ligands. Table 1 contains a comparison of selected NMR
chemical shift data for pertinent CH(PPh2)2- and
2-{(Me3Si)2C}-C5H4N-containing compounds. The dou-
blet at δ 3.81 [2J (31P-1H) ) 6 Hz] is similar to that
observed for its Sn analogue 52 (though is very much
sharper) with both resonances to much higher frequency
compared with CH2(PPh2)2 and Li(Et2O)‚CH(PPh2)2 (δ
2.78 and 2.16, respectively): a doublet (presumably two
unresolved, overlapping doublets) rather than a triplet
is observed as a result of the two distinct 31P environ-
ments (vide infra). Contrasting that for 3, but as found
for [Sn(2-{(Me3Si)2C}-C5H4N){CH(PPh2)2}],2 1, and 2,
two distinct resonances corresponding to the SiMe3 1H
environments are observed, indicating that the N-Ge
bond persists in solution at ambient temperature. The
13C{1H} NMR spectrum of 4 in C6D6 at ambient tem-
perature, in contrast to that for 5, exhibits only sharp
resonances. The sharpness and number of distinct
resonances in the 13C{1H} NMR spectrum suggest that
the coalescence point corresponding to unrestricted
rotation about the E-CH(PPh2)2 bond which is being
closely approached at ambient temperature for 5 (E )
Sn), is energetically much further away for 4 (E ) Ge).
This is in agreement with the shorter E-CH(PPh2)2
bond for E ) Ge vs Sn (vide infra). In agreement with
the 1H NMR spectrum and further supporting the
persistence of the formally coordinate N-Ge bond of 4
in solution at ambient temperature, resonances corre-
sponding to two distinct SiMe3 13C environments are
observed (δ 4.07 and 1.57). The resonance corresponding
to the C atom of the 2-{(Me3Si)2C} moiety appears at δ
38.10. The resonance corresponding to the central C
atom of the CH(PPh2)2 ligand appears at δ 22.80 as an
1
2
with J (29Si-29Si) and J (119,117Sn-29Si) satellites of 43
and 36 Hz respectively, corresponds to the SiMe3 groups
of the Si(SiMe3)3 ligand with a chemical shift extremely
similar to that of its Li salt, [Li(thf)3‚Si(SiMe3)3] (δ
-5.2).36 The resonances at δ -0.3 and -3.3, the former
2
with J (119,117Sn-29Si) satellites of 33 Hz, are assigned
to the chemically distinct SiMe3 groups of the 2-
2
{(Me3Si)2C}-C5H4N ligand. That the J (119,117Sn-29Si)
coupling on the resonance at δ -3.3 is not fully resolved
at 5.872 T and that the corresponding values in 1 (21
and 13 Hz) are also different from each other is at
present not understood, but is presumably a reflection
on the position of the two Si atoms with respect to the
lone pair at the central divalent Sn. Furthermore, the
resonance corresponding to the central 29Si atom of the
Si(SiMe3)3 ligand was not observed: the 119Sn chemical
shift of the Sn(SiMe3)3 ligand in 1 is to considerably
higher frequency in comparison with that of its Li salt,
[Li(thf)3‚Sn(SiMe3)3] (δ -502 vs -878).34 Thus, it is
possible that the 29Si resonance of the central Si atom
for 2 occurs to higher frequency compared with that of
1
its Li salt [δ -189.4; a 1:1:1:1 quartet with J (7Li-29Si)
39 Hz]36 also, but that it is masked by the broad peak
in the 29Si{1H} spectrum that appears at ca. δ 100-
130 and which corresponds to the glass insert of the
NMR probe. The 119Sn{1H} NMR spectrum in C6D6 at
ambient temperature exhibits a single resonance at δ
876 which does not exhibit any resolvable nJ (29Si-119Sn)
satellites (n ) 1 or 2) and is only ca. 20 ppm different
from that for 1.
1
apparent triplet with J (31P-13C) 105 Hz: on the basis
of the observed doublet in the 1H NMR spectrum
[E-CH(PPh2)2, δ 3.81, 2J (31P-1H) ) 6 Hz] and by
analogy with the discussion presented for 5,2 it is likely
that this triplet is in fact an overlapping pair of doublets.
This chemical shift is slightly to lower frequency with
respect to that for “free” bis(diphenylphosphino)methane
[C6D6, δ 28.86, 1J (31P-13C) ) 48 Hz] and 5 [C6D6, δ
26.79, 1J (31P-13C) ) 114 Hz] but to significantly higher
frequency than the corresponding resonances for Li-
(Et2O)‚CH(PPh2)2 (C6D6, δ 18.14). This suggests there-
fore that in solution, the CH(PPh2)2 ligand of 4 is bound
to the central Ge atom η1, via the central C atom. The
31P{1H} NMR spectrum of 4 in C6D6 at ambient tem-
perature, like that for 3, exhibited two resonances with
equal integral values and similar intensities (δ 1.1 and
-11.0). The 29Si{1H} NMR spectrum of 4 was also
recorded in C6D6 at ambient temprature and exhibits a
single and slightly broad resonance at δ 0. (The ambient
temperature 29Si{1H} NMR spectrum of 5 exhibited a
single resonance, while at 245 K in C4D8O, exhibited
two just resolvable resonances, centered at δ 2).2
[Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3). The 1H NMR
spectrum of 3 in C6D6 at ambient temperature exhibits
resonances with characteristic chemical shifts and
integral values, very similar to those observed for its
Sn analogue23 though considerably broader. This sug-
gests that the formally cordinate N-Ge bond, though
not persistent in solution, is much stronger than the
corresponding bond in [Sn(2-{(Me3Si)2C}-C5H4N)Cl] for
1
which the H and 13C{1H} NMR spectra exhibit sharp
resonances. In the 13C{1H} NMR spectrum, resonances
for the aromatic 13C environments of the 2-{(Me3Si)2C}-
C5H4N ligand are observed at δ 174.54, 143.95, 139.66,
126.10, and 119.65. The resonance for the quaternary
13C environment of the 2-{(Me3Si)2C} moiety is observed
at δ 39.24, several ppm to lower frequency compared
with that for [Sn{2-[(Me3Si)2C]-C5H4N}Cl] (δ 43.34). In
Cr ysta l Str u ctu r es of [E(2-{(Me3Si)2C}-C5H4N)R]
(1-4). The molecular structures of 1-4 are presented
in Figures 1-4, respectively. Table 2 contains a sum-
1
agreement with the H NMR spectrum, only one (albeit
broad) 13C resonances is observed for the SiMe3 groups,

Heteroleptic Stannylenes and Germylenes
Organometallics, Vol. 18, No. 3, 1999 397
mary of cell constants and data collection parameters
for 1 and 2, respectively. Table 3 and Table 4 contain
atom coordinates (× 104) and temperature factors (Å2
× 103) for 1 and 2 respectively. Important intramolecu-
lar distances and angles for compounds 1 and 2 are
listed in Tables 5 and 6, respectively. Table 7 contains
a summary of cell constants and data collection param-
eters for 3 and 4 respectively. Tables 8 and 9 contain
atom coordinates (×104) and temperature factors (Å2 ×
103) for 3 and 4 respectively. Important intramolecular
distances and angles for compounds 3 and 4 are listed
in Tables 10 and 11, respectively.
divalent group 14 element is three-coordinate, bound
η1 to the R (Cl) ligand and η2 to the 2-{(Me3Si)2C}-
C5H4N ligand. However, there are two crystallographi-
cally independent molecules in the unit cell, the geom-
etries of which differ only very slightly; 3 is isostructural
with [Sn(2-{(Me3Si)2C}-C5H4N)Cl]. The 2-{(Me3Si)2C}-
C5H4N ligand is bound to the Ge atom through the
central C atom of the 2-{(Me3Si)2C} substituent and the
N atom of the C5H4N ring [Ge(1,2)-C(1,13), 2.138(5),
2.138(5); Ge(1,2)-N(1,2), 2.082(4), 2.075(4) Å; Table 10]:
the Ge(1,2)-Cl(1,2) bond lengths are 2.2948(19) and
2.2962(19) Å. These Ge-C and Ge-Cl distances are are
very much longer than those in dimeric [(Ge{C6H3-2,6-
(C6H2-2,4,6-Me3)2}Cl)2] which has a Ge-Ge bond of
2.443(2) Å and terminal Cl atoms [Ge-C, 2.000(6); Ge-
Cl, 2.120(2) Å]: the Sn analogue is dimeric also, but
possesses two bridging Cl atoms and no metal-metal
interaction.1 The C(1,13)-Ge(1,2)-Cl(1,2) and N(1,2)-
Ge(1,2)-Cl(1,2) angles of 101.86(17), 102.52(15),
91.89(14), and 93.06(14) are very close to the corre-
sponding angles in [Sn(2-{(Me3Si)2C}-C5H4N)Cl], while
the much larger N(1,2)-Ge(1,2)-C(1,13) angles [67.1(2)
and 66.9(2) vs 61.4(6) and 61.7(6)°] are a consequence
of the shorter Ge-ligand C, N bond lengths in 3. These
angles are also slightly larger than that observed for
the four-coordinate homoleptic analogue, [Ge(2-
{(Me3Si)2C}-C5H4N)2] [64.8(3)°] but are very similar to
those for the five-coordinate derivatives, [Ge(2-
{(Me3Si)2C}-C5H4N)2Se] [67.16(13) and 67.40(13)°] and
[Ge(2-{(Me3Si)2C}-C5H4N)2Te] [67.12(8)°].30
[Ge(2-{(Me3Si)2C}-C5H4N){CH(P P h 2)2}] (4). An ex-
amination of the molecular structure presented in
Figure 4 reveals compound 4 to be monomeric in the
solid state also. The central Ge atom is η2-bound to the
2-{(Me3Si)2C}-C5H4N ligand through the C atom of the
2-{(Me3Si)2C} substituent and the N atom of the C5H4N
ring [Ge(1)-C(26), 2.142(9), Ge(1)-N(1), 2.089(7) Å] and
η1 bound to the CH(PPh2)2 ligand through its central C
atom, C(1) [Ge(1)-C(1) 2.097(8) Å]. The molecular
structures of [E{CH(PPh2)2}2] (E ) Sn, Pb)41 and [Sn(2-
{(Me3Si)2C}-C5H4N){CH(PPh2)2}] (5) have been re-
ported,2 but 4 is the first structurally characterized
germylene employing the CH(PPh2)2 ligand. The Ge-
ligand C, N bond lengths (Ge(1)-C(26), 2.142(9) and
Ge(1)-N(1), 2.089(7) Å) are not significantly different
from those in 3; the Ge(1)-C(26) distance and the Ge-
CH(PPh2)2 [Ge(1)-C(1), 2.097(8) Å] distance are also not
significantly different.
[Sn (2-{(Me3Si)2C}-C5H4N){Sn (SiMe3)3}] (1). The
molecular structure of 1 illustrated in Figure 1 shows
it to be monomeric with a distorted trigonal pyramidal
geometry about the central, three coordinate divalent
Sn atom, Sn(1), typical of heteroleptic 2-{(Me3Si)2C}-
C5H4N derivatives of Sn(II).2,23 The Sn(1) atom is
bonded to the 2-{(Me3Si)2C}-C5H4N ligand via the C
atom of the 2-{(Me3Si)2C} substituent [C(6)] and by a
formally coordinate bond with the N atom of the C5H4N
ring. The Sn(1)-C(6) bond length of 2.304(2) Å is
marginally shorter than that found in the related,
covalent [Sn(2-{(Me3Si)2C}-C5H4N)R] [R ) Cl, 2.32(2)
Å (both molecules); R ) 2-{(Me3Si)2C}-C5H4N, 2.334(6),
2.346(6) and 2.377(7) Å; R ) N(SiMe3)2, 2.356(8) Å],23
a
result of the longer Sn(1)-R bond when R ) Sn(SiMe3)3,
reducing the steric congestion about the Sn(1) center.
The Sn(1) and Sn(2) atoms are bound by a single bond,
2.8689(5) Å in length; this is the first structurally
authenticated measurement of a bond between divalent
Sn and tetravalent Sn. The C5H4N ring of the 2-
{(Me3Si)2C}-C5H4N ligand shows values typical for an
aromatic system.
[Sn (2-{(Me3Si)2C}-C5H4N){Si(SiMe3)3}] (2). The
molecular structure of compound 2 is presented in
Figure 2. It can be seen that it is monomeric in the solid
state and that the central divalent Sn atom is three-
coordinate, bound η1 to the Si(SiMe3)3 ligand and η2 to
the 2-{(Me3Si)2C}-C5H4N ligand; thus 2 is isostructural
with 1. The 2-{(Me3Si)2C}-C5H4N ligand is bound to the
central Sn atom through the central C atom of the
2-{(Me3Si)2C} substituent and the N atom of the C5H4N
ring [Sn-C, 2.345(6); Sn-N, 2.335(5) Å; Table 6]. The
Sn-Si bond length of 2.7236(18) Å is significantly longer
than the corresponding distances in [(Sn{Si(SiMe3)3}2)2]
[2.6667(11) and 2.6781(11) Å],39 [Sn{Si(SiMe3)3}2(µ-
Cl)Li(thf)3] [2.681(2) Å]40 and [Sn{C6H3-2,6-(NMe2)2}(Si{(-
NCH2But)2-1,2-C6H4}{C6H3-2,6-(NMe2)2})] [2.636(2) Å].28
The geometry about the central Si atom of the Si(SiMe3)3
ligand is distorted tetrahedral [Sn-Si(4)-Si(3), 91.88(7);
Sn-Si(4)-Si(5), 111.53(8); Sn-Si(4)-Si(6), 129.43(10)°],
as is found for the two corresponding Si environments
in the bis{Si(SiMe3)3} derivative: the angles about one
Si atom are similar to those in 2 [99.78(5), 106.19(5),
and 131.88(6)°] while the angles about the second Si
atom are much less distorted from ideal [112.06(5),
112.35(5), and 115.51(5)°].
Con clu sion s
We have prepared and structurally characterized two
novel, monomeric heteroleptic derivatives of divalent Sn,
the stannylenes 1 and 2. We envisage that these will
play an important role in the development of compounds
containing bonds between low-valent group 14 elements.
Additionally, we have prepared and structurally char-
acterized two monomeric heteroleptic derivatives of
divalent Ge, germylenes 3 and 4, demonstrating the
utility of [Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3) as a precursor
to further novel divalent Ge compounds by the prepara-
tion of the CH(PPh2)-containing [Ge(2-{(Me3Si)2C}-
C5H4N){CH(PPh2)2}] (4). As illustrated for their Sn
[Ge(2-{(Me3Si)2C}-C5H4N)Cl] (3). The molecular
structure of compound 3 is presented in Figure 3. Like
1 and 2, 3 is monomeric in the solid state and the central
(39) Klinkhammer, K. W.; Schwartz, W. Angew. Chem., Int. Ed. Eng.
1995, 34, 1334.
(40) Arif, A. M.; Cowley, A. H.; Elkins, T. M. J . Organomet. Chem.
1987, 325, C11.
(41) Balch, A. L.; Oram, D. E. Organometallics 1986, 5, 2159.

398 Organometallics, Vol. 18, No. 3, 1999
Benet et al.
1
analogues,2,23 the H NMR spectra of 3 and 4 reveal the
supplying the SHELX 96 and 97 programs, Dr. L. J .
Farrugia (University of Glasgow) for supplying the
ORTEP-3 for Windows program, Mr. Chris Patmore for
image manipulation and the ERASMUS exchange pro-
gram (S.B), and the BBSRC (A.K.T), and the EPSRC
(S.P.C., J .H.T., and H.R.) for financial support.
persistence of the formally coordinate N-E bond in
solution at ambient temperature for 4 only. With
regards to the chemistry of compounds containing bonds
between main group elements and tranistion metals, we
predict that the heteroleptic nature of 1-4 will give rise
to interesting reactivity in their coupling with transition
metal clusters.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
data, positional and thermal parameters, bond distances and
angles, least-squares planes, 29Si{1H} and 119Sn{1H} NMR
spectra for 1 (25 pages). Ordering information is given on any
current masthead page.
Ack n ow led gm en t. The authors wish to thank Pro-
fessor W. Clegg for allocation of SRS beamtime and use
of facilities at the CLRC, Daresbury Laboratory (1),
Professor G. M. Sheldrick (University of Go¨ttingen) for
OM980836Z