A route to a germanium - Carbon triple bond: First chemical evidence for a germyne

Article abstract of DOI:10.1002/1521-3773(20010302)40:5<952::AID-ANIE952>3.0.CO;2-S

Photolysis of a diazogermylene generates a germylene-carbene species, a resonance form of a germyne (see scheme). Support for the intermediacy of the triply bonded form in the trapping reaction with an alcohol is provided by the fact that the diazo precur

Full text of DOI:10.1002/1521-3773(20010302)40:5<952::AID-ANIE952>3.0.CO;2-S

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[1] a) C. Walling, Acc. Chem. Res. 1975, 8, 125; b) P. A. Mc Faul, D. D. M.
Wayner, K. U. Ingold, Acc. Chem. Res. 1998, 31, 159.
higher concentration. Other minor products have been detected but
their structures remain unknown.
[2] a) S. H. Bossman, E. Oliveros, S. Göb, S. Siegwart, E. P. Dahlen, L.
Payawan, M. Straub, M. Wörner, A. M. Braun, J. Phys. Chem. A 1998,
102, 5542; b) D. T. Sawyer, A. Sobkowiak, T. Matsushita, Acc. Chem.
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[3] a) R. M. Buchanan, S. Chen, J. F. Richardson, M. Bressan, L. Forti, A.
Morvillo, R. H. Fish, Inorg. Chem. 1994, 33, 3208; b) J. Kim, R. G.
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[13] S. J. Lange, H. Miyake, L. Que, Jr., J. Am. Chem. Soc. 1999, 121, 6330.
[14] The reaction mixture contains both mononuclear FeII and FeIII L and
L1 complexes.
[15] 1H NMR (300 MHz, CD3CN, 258C): d ˆ 2.66 (m, 4H; NCH2CH2N),
3.52 (s, 2H; CH2Bz), 3.62 (s, 3H; OCH3), 3.67 (s, 2H; CH2py), 3.69 (s,
6H; OCH3), 3.72 (s, 2H; CH2py), 6.63 (s, 2H; o-HPh); 7.13 (td, 2H; m-
H
py); 7.23 (d, 1H; p-Hpy), 7.43 (d, 1H; p-Hpy), 7.61 (t, 2H; m-Hpy), 8.41
Â
Duboc-Toia, S. Menage, C. Lambeaux, M. Fontecave, Tetrahedron
(dd, 2H, o-Hpy). ESI/MS (CH2Cl2; positive-ion mode): m/z: 423
‡
Lett. 1997, 38, 3727, and references therein; d) M. Kodera, H.
Shimakoshi, K. Kano, Chem. Commun. 1996, 1737; e) D. T. Sawyer,
C. Kang, A. Liobet, C. Redman, J. Am. Chem. Soc. 1993, 115, 5817;
f) D. H. R. Barton, S. D. Beviere, W. Chavasiri, E. Cshuai, D. Doller,
W.-G. Liu, J. Am. Chem. Soc. 1992, 114, 2147.
(100%) for [L1 ‡ H ].
[16] Accordingly, the pendant product of the N-dealkylation of the ligand,
3,4,5-trimethoxybenzaldehyde, has been quantitatively detected.
[17] Experimental conditions: complex/alkane/H2O2 1/1100/10 in acetoni-
trile inside a glove box (dioxygen content less than 1 ppm) using
syringe pump conditions; delivering time ˆ 30 min [complex] ˆ
0.7 mm.
Â
Á
[4] a) A. C. Rosenzweig, C. A. Frederick, S. J. Lippard, P. Nordlund,
Nature 1993, 366, 537; b) J. B. Wallar, J. D. Lipscomb, Chem. Rev. 1996,
96, 2625.
[5] a) L. Que, Jr., R. Y. N. Ho, Chem. Rev. 1996, 96, 2607; b) T. J.
Kappock, J. P. Caradonna, Chem. Rev. 1996, 96, 2659.
[6] S. Menage, J. B. Galey, J. Dumats, G. Hussler, M. Seite, I. Gautier-
Luneau, G. Chottard, M. Fontecave, J. Am. Chem. Soc. 1998, 120,
13370.
[7] G. V. Buxton, C. L. Greenstock, W. P. Helman, A. B. Ross, J. Phys.
Chem. Ref. Data 1988, 17, 513.
[18] The isotope ratio in cyclohexanol has been analyzed by GC/MS on a
reaction mixture directly after reaction. Cyclohexanol was not labeled
in the presence of 18O water under standard conditions.
[19] No 1,2-cyclohexanediol was detected.
[20] A. M. Khenkin, A. E. Shilov, New. J. Chem. 1989, 13, 659.
[21] Notably, [(bpmen)FeIICl2]/H2O2 showed the same stereoselectivity,
selectivity, and catalytic properties as complex 1 (bpmen ˆ N,N'-
dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine). Thus, the
concomitant formation of [Fe(LO)Cl2] is not responsible for the poor
catalytic properties.
Â
Â
[8] Selected physical data for 1: Elemental analysis for 1 ´ 0.25H2O
(C34H42.5Cl2FeN4O6.25)(Mr ˆ 733.4): calcd: C 55.62, H 5.79, N 7.63, Cl
9.68, Fe 7.63; found: C 55.45, H 5.87, N 7.64, Cl 9.75, Fe 7.68; ESI/
[22] a) W. Nam, J. S. Valentine, J. Am. Chem. Soc. 1993, 115, 1772; b) K. A.
Lee, W. Nam, J. Am. Chem. Soc. 1999, 121, 1916.
‡
MS(CH3CN): m/z: 693 (100%) [FeLCl] ; UV/Vis (CH3CN): lmax (e,
1 cm 1): 415 nm (1050). Crystal data of 1 ´ CH3CN: C36H45Cl2Fe-
m
[23] K. Chen, L. Que, Jr., Chem. Commun. 1999, 1375.
[24] J. Bernadou, B. Meunier, Chem. Commun. 1998, 2167.
[25] No hydrogen peroxide dismutation was observed for either complex
in the absence of substrate, apart from the involvement of dioxygen as
an oxygen-atom donor (autooxidation mechanism).
Å
N5O6, Mr ˆ 770.52, triclinic, space group P1, a ˆ 13.1459(2), b ˆ
15.5146 (2), c ˆ 18.5430 (2) Š, a ˆ 92.19(1), b ˆ 98.22(1), g ˆ
99.93(1)8, Vˆ 3679.34(8) Š3, Z ˆ 4, 1calcd ˆ 1.391 gcm
,
m ˆ
3
0.607 mm 1, l ˆ 0.71073 Š, direct methods, R[I > 2s(I)] ˆ 0.0305 for
12229 independent reflections of the 17177 collected, R(all data) ˆ
0.046. Selected physical data for 2: Elemental analysis for 2(ClO4)2 ´
3H2O (C34H48Cl2FeN4O17)(Mr ˆ 911.3): calcd: C 44.80, H 5.26, N 6.15,
Cl 7.78, Fe 6.15; found: C 44.80, H 5.44, N 6.16, Cl 8.22, Fe 5.75; ESI/
Â
[26] a) C. Duboc-Toia, S. Menage, R. Y. N. Ho, L. Que, Jr., C. Lambeaux,
M. Fontecave, Inorg. Chem. 1999, 38, 1261; b) Y. Mekmouche, C.
Â
Duboc-Toia, S. Menage, C. Lambeaux, M. Fontecave, J. Mol. Catal. A
2000, 156, 85; c) C. Kim, K. Chen, J. Kim, L. Que, Jr., J. Am. Chem.
Soc. 1997, 119, 5964.
‡
MS (CH3CN): m/z: 757 (100%) [FeLClO4] ; UV/Vis (CH3CN): lmax
(e, m 1 cm 1): 377 nm (1700). Suitable crystals for an X-ray analysis
were obtained after a metathesis of ClO4 for PF6 anions. Crystal data
of 2(PF6)2 ´ 2.5 CH3CN´ 0.25 CH3OH´ 0.5 H2O: C43.25H57.5F12P2FeN8.5
-
Å
O
6.75, Mr ˆ 1144.22, triclinic, space group P1, a ˆ 13.3988(9), b ˆ
14.5835(9), c ˆ 27.8533 (17) Š, a ˆ 98.096(1), b ˆ 94.746(1), g ˆ
A Route to a Germanium ± Carbon Triple
Bond: First Chemical Evidence for a
Germyne**
94.264(1)8, Vˆ 5349.4(6) Š3, Z ˆ 4, 1calcd ˆ 1.421 gcm
,
m ˆ
3
0.437 mm 1, R[I > 2s(I)] ˆ 0.0748 for 24469 independent reflections
of the 34761 collected, R(all data) ˆ 0.1708. Crystallographic data
(excluding structure factors) for the structures reported in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-146454 (1) and
CCDC-146455 (2(PF6)2). Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk).
Â
Á
Christine Bibal, Stephane Mazieres, Heinz Gornitzka,
and Claude Couret*
Since the isolation of the first disilene, a compound
containing a silicon ± silicon double bond, in 1981,[1] many
stable compounds with a double bond involving the Group 14
elements Si, Ge, and Sn have been synthesized.[2] In contrast,
compounds containing a triple bond to a Group 14 element
other than C remained unknown. Power[3] described recently
a lead analogue of an alkyne (ArPbPbAr) but more consistent
with a diplumbylene form. However, some compounds with
triple bonds to Si were identified by spectroscopy or by
[9] See for example: a) C. J. Carrano, M. W. Carrano, K. Sharma, G.
Backes, J. S. Sanders-Loehr, Inorg. Chem. 1990, 29, 1865; b) A. B. P.
Lever, Inorganic Electronic Spectroscopy, Elsevier, New York, 1984,
p. 311.
[10] The resulting solution was concentrated and diluted in water in the
presence of excess dithionite and bathophenanthroline. The organic
material was extracted from the solution by using dichloromethane
and choloroform.
[11] Comparisons between 1H and 13C NMR spectra of L and LOH
allowed us to unambiguously attribute the inserted oxygen position. In
fact, the signal at d ˆ 6.63 corresponding to the o-H for L is replaced
by two signals at d ˆ 6.63 and 6.42 in a 2:1 ratio for LOH. A similar
trend is observed in the 13C NMR spectrum (for the o-C of the phenyl
ring signals appear at d ˆ 108.5 and 105.5 for LOH, but only at d ˆ
105.0 for L). ESI-MS for LOH (CH2Cl2; positive-ion mode): m/z: 619
Á
[*] Prof. Dr. C. Couret, C. Bibal, Dr. S. Mazieres, Dr. H. Gornitzka
 Â
Â
Laboratoire Heterochimie Fondamentale et Appliquee
Â
Universite Paul Sabatier
118, route de Narbonne, 31062 Toulouse cedex 04 (France)
Fax : (‡33)5-61-55-82-04
‡
E-mail: couret@ramses.ups-tlse.fr
(100%) for [LOH ‡ H ].
[12] The HPLC titration has been carried out on authentic pure samples of
L, L1, and LOH obtained by extraction of the reaction mixture at
[**] We thank Prof. Dr. Josef Michl (University of Colorado at Boulder,
USA) for helpful discussions.
952
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Angew. Chem. Int. Ed. 2001, 40, No. 5

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various other methods.[4] Germaisocyanides Ge NR have
only been detected by photoelectron spectroscopy,[5] whereas
in coordination chemistry, stable transition metal germylyne
complexes have been reported and structurally characterized
since 1996.[6] No triple bond to tin has yet been described.
Besides the difficulty in isolating such a triply bonded
compound and the possibility that more stable isomers exist,
the major obstacle remains to find a suitable synthetic
method. We considered a potential route to germynes
:
ꢀ
ꢀ
RGe CR' from a germylene ± carbene structure (Scheme 1).
Scheme 1. Resonance forms: germylene ± carbene and germyne.
Figure 1. Molecular structure of 2 in the solid state. Selected distances [Š]
and angles [8]: Ge1-C5 2.006(5), Ge1-C1 2.02(1), Si1-C1 1.85(8), Ge1-N3
2.35(9), Ge1-N4 3.05(3), C1-N1 1.298(2), N1-N2 1.146(2); C5-Ge1-C1
96.84(7), C5-Ge1-N3 80.46(6), C1-Ge1-N3 98.94(6), N1-C1-Si1 115.55(12),
Ge1-C1-Si1 128.0(8), Ge1-C1-N1 116.33(11), N2-N1-C1 178.02(10).
Coupling reactions between germylenes (or stannylenes) and
carbenes that provide convenient access to Ge C and Sn C
double bonds[7, 8] prompted us to extend such a methodology
to the formation of a germanium ± carbon triple bond from a
s-bonded germylene ± carbene compound. Generation of a
carbene moiety adjacent to a Group 14 element bearing both
a lone pair and a vacant p orbital[9] appears to be an attractive
method for the synthesis of a triply bonded metal ± carbon
species. Diazogermylenes RGeC(N2)R' may be convenient
precursors for the formation of such a unit by photolysis or
thermolysis. We describe here the synthesis and the structure
of diazogermylenes ArGeC(N2)SiMe3 and an initial study of
their photochemical behavior.
to the plane of the aryl ligand. The Ge1 C1 (2.02(1) Š) and
C1 Si1 (1.85(8) Š) bond lengths are close to the normal
values for s bonds of 1.99 and 1.94 Š, respectively.[12a] The
Ge1-C1-Si1 angle of 128.0(8)8 is consistent with sp2 hybrid-
ization of carbon atom C1 and a repulsive steric interaction
between germanium and the SiMe3 group.
When a solution of 2 in toluene was irradiated at 508C
and l ˆ 300 nm in the absence of a trapping agent, we
observed evolution of nitrogen and formation of polymeric
materials. Elemental analyses of these polymers are compat-
ible with a formula such as (ArGeCSiMe3)n. When the same
irradiation was carried out in the presence of an alcohol as a
trapping agent, 3 was obtained in nearly quantitative yield for
R2 ˆ tBu and in 40% yield for R2 ˆ Me [Eq. (2)]. The
The 2,6-bis[(dialkylamino)methyl]phenyl groups (R12NCH2)2-
C6H3 (Ar) are suitable ligands because of their steric bulk and,
in particular, their stabilizing effect due to intramolecular
coordination of the nitrogen lone pair to empty orbitals on the
metal atom. The use of this kind of ligand has allowed the
preparation of sensitive derivatives of main group elements,
such as gallium and indium halides (R1 ˆ Me, Et)[10a±c] as well
as a chlorostannylene (R1 ˆ Me).[10d]
The diazogermylenes were obtained in good yields by one-
pot synthesis [Eq. (1)]. Compounds 1 and 2 are readily soluble
È
È
formation of 3 from the germylene ± carbene species ArGe C-
SiMe3 (I) formed by photolysis of 2 can be explained by three
possible mechanisms (Scheme 2): I can react as a carbene (1),
as a germylene (2), or as a germyne (3). All processes involve
2
ˆ
the transient formation of germene ArGe(OR ) CHSiMe3,
in hydrocarbon and ether solvents and have been fully
characterized. Whereas 1 is a yellow, viscous oil, 2 is
crystalline, and single crystals suitable for an X-ray structure
determination were grown from pentane at 208C. The
structure analysis[11] showed 2 to be monomeric in the solid
state (Figure 1).
but routes 1 and 2 require rearrangement reactions.
Mechanism 1 can be excluded since I does not behave as a
carbene; for example, it does not react with dienes such as 2,3-
dimethylbutadiene, which is well known to react with
The Ar ligand is bound to germanium in a bidentate fashion
with a s bond to the ipso-carbon atom C5 and intramolecular
coordination of the N atom of a CH2NiPr2 side chain. The
Ge1 N3 distance of 2.35(9) Š is, as expected, longer than the
a normal Ge N s bond (1.92 Š[12a]) but much shorter than the
sum of the van der Waals radii (3.74 Š[12b]). The Ge N4
distance (3.05(3) Š) indicates a weak interaction between the
N atom of the other side chain and the metal atom. The
coordination sphere of germanium is completed by the
Ge1 C1 bond, which is oriented almost orthogonal (96.88)
Scheme 2. Possible mechanisms of the trapping reaction (2).
Angew. Chem. Int. Ed. 2001, 40, No. 5
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carbenes.[13] Moreover, kinetic studies have shown that the
reactivity of alcohols towards carbenes is proportional to their
acidity and that the relative reactivity of tertiary alcohols such
as tBuOH is low.[14] As diazogermylene 2 does not react with
tBuOH at room temperature or with MeOH at low temper-
ature, it does not behave as a germylene, and this rules out
mechanism 2. The lack of typical carbene and germylene
reactivity of I suggests that it is reasonable to postulate
mechanism 3, in which the germyne is trapped by two
equivalents of alcohol.
In conclusion, diazogermylenes, in which a carbenoid
species is adjacent to a Group 14 atom bearing both a lone
pair and vacant orbitals, are promising precursors to germa-
nium ± carbon triple bonds. Our results, which constitute the
first chemical evidence for a germyne, contrast with ab initio
quantum mechanical calculations of Stogner and Grev on the
[1] R. West, M. J. Fink, J. Michl, Science 1981, 214, 1343 ± 1344.
Â
[2] a) P. P. Power, Chem. Rev. 1999, 99, 3463 ± 3503; b) J. Escudie, C.
Couret, H. Ranaivonjatovo, Coord. Chem. Rev. 1998, 178 ± 180, 565 ±
592.
[3] L. Pu, B. Twamley, P. P. Power, J. Am. Chem. Soc. 2000, 122, 3524 ±
3525.
[4] M. Karni, Y. Apeloig, D. Schröder, W. Zummack, R. Rabezzana, H.
Schwarz, Angew. Chem. 1999, 111, 344 ± 347; Angew. Chem. Int. Ed.
1999, 38, 331 ± 335, and references therein.
Á
Á
[5] S. Foucat, T. Pigot, G. Pfister-Guillouzo, H. Lavayssiere, S. Mazieres,
Organometallics 1999, 18, 5322 ± 5329.
[6] a) R. S. Simons, P. P. Power, J. Am. Chem. Soc. 1996, 118, 11966 ±
11967; b) L. Pu, B. Twamley, S. T. Haubrich, M. M. Olmstead, B. V.
Mork, R. S. Simons, P. P. Power, J. Am. Chem. Soc. 2000, 122, 650 ±
656.
[7] a) H. Meyer, G. Baum, W. Massa, A. Berndt, Angew. Chem. 1987, 99,
790; Angew. Chem. Int. Ed. Engl. 1987, 26, 798 ± 799; b) A. Berndt, H.
Meyer, G. Baum, W. Massa, S. Berger, Pure Appl. Chem. 1987, 59,
1011 ± 1014; c) M. Weidenbruch, H. Kilian, M. Stürmann, S. Pohl, W.
Saak, H. Marsmann, D. Steiner, A. Berndt, J. Organomet. Chem. 1997,
530, 255 ± 257.
[8] a) N. Kuhn, T. Kratz, D. Blaeser, R. Boese, Chem. Ber. 1995, 128, 245 ±
250; b) A. Schäfer, M. Weidenbruch, W. Saak, S. Pohl, J. Chem. Soc.
Chem. Commun. 1995, 1157 ± 1158.
[9] Phosphorus ± carbon triple bonds were obtained from a phosphini-
dene ± carbene compound: a) D. J. Berger, P. P. Gaspar, P. Le Floch, F.
Mathey, R. S. Grev, Organometallics 1996, 15, 4904 ± 4915; b) D.
Bourissou, P. Le Floch, F. Mathey, G. Bertrand, Org. Organomet.
Synth. 1999, 351 ± 357.
ꢀ
parent molecule HGe CH, which indicated that the germa-
vinylidene isomer Ge ˆ CH2 is 7 kcalmol 1 more stable than
:
1
trans-bent germyne, and 43 kcalmol more stable than the
linear germyne.[15] However, our results are in accordance
with the work of Apeloig and Karni in the field of silicon
chemistry, who predicted that bulky substituents are expected
to destabilize the vinylidene structure relative to the triple
bond.[16]
[10] a) A. Cowley, R. Jones, M. Mardones, J. Ruiz, J. Atwood, S. Bott,
Angew. Chem. 1990, 102, 1169; Angew. Chem. Int. Ed. Engl. 1990, 29,
1150 ± 1151; b) H. Schumann, W. Wassermann, A. Dietrich, J. Organo-
met. Chem. 1989, 365, 11 ± 18; c) H. Schumann, U. Hartmann, W.
Wassermann, Chem. Ber. 1991, 124, 1567 ± 1569; d) J. T. B. H. Jastr-
zebski, P. A. Van der Schaaf, J. B. Boerma, G. van Koten, M. C.
Zoutberg, D. Heijdenrijk, Organometallics 1989, 8, 1373 ± 1375.
[11] Crystal data for 2: C24H44GeN4Si, Mr ˆ 489.31, monoclinic, space
Experimental Section
All experiments were performed under a dry and oxygen-free argon
atmosphere. Solvents were dried by appropriate methods. Melting points
were determined in capillaries sealed under argon and are not corrected.
1: n-Butyllithium (4.2 mL, 1.6m in hexane) was added dropwise to ArBr
(2.0 g, 6.1 mmol) in THF (15 mL) at 788C, and the mixture was stirred for
20 min. A solution of GeCl2 ´ dioxane (1.4 g, 6.1 mmol) in THF (15 mL) was
then added at the same temperature, and the reaction mixture was stirred
for 30 min at room temperature. A solution of lithiotrimethylsilyldiazo-
methane (6.1 mmol) prepared from a solution of trimethylsilyldiazo-
methane (3.05 mL, 2m in hexane) and nBuLi (4.2 mL, 1.6m in hexane) in
THF (15 mL) was added dropwise to the above mixture at 788C, and the
solution was stirred at room temperature for 30 min. Solvents were
removed in vacuum, and the residue was dissolved in pentane. The mixture
was filtered, the solvents evaporated, and 1 was obtained as viscous oil
(1.98 g, 75% yield). 1H NMR (400.1 MHz, C7D8, TMS): d ˆ 0.55 (s, 9H,
Me3Si), 1.11 (t, 3J(H,H) ˆ 6.7 Hz, 12H, CH2CH3), 2.83 (q, 3J(H,H) ˆ
6.7 Hz, 8H, CH2CH3), 3.63, 3.75 (AB system, 2J(H,H) ˆ 14.2 Hz, 4H,
CH2), 7.10 ± 7.30 (m, 3H); 13C NMR (100.6 MHz, C7D8, TMS): d ˆ 0.40
(1J(13C,29Si) ˆ 26.6 Hz, CH3Si), 9.84 (CH2CH3), 24.49 (CN2), 45.31
(CH2CH3), 59.77 (CH2), 124.54 (m-C), 127.69 (p-C), 145.21 (o-C), 156.85
(ipso-C); 14N NMR (28.9 MHz, C7D8, MeNO2): d ˆ 110 (14Na), 14Nb signal
too weak to be observed; 29Si NMR (39.8 MHz, C7D8, TMS): d ˆ 0.98
group P21/c, a ˆ 10.3936(3), b ˆ 10.8900(3), c ˆ 24.2005(8) Š, b ˆ
3
99.247(1)8, Vˆ 2703.6(1) Š3, Z ˆ 4, 1calcd ˆ 1.202 Mgm
,
F(000) ˆ
1
1048, l ˆ 0.71073 Š, Tˆ 193(2) K, m(MoKa) ˆ 1.194 mm
, crystal
dimensions 0.1 Â 0.6 Â 0.8 mm, 2.53 ꢁ q ꢁ 30.498; 22744 reflections
(8204 independent, Rint ˆ 0.0469) were collected at low temperature
on an oil-coated shock-cooled crystal on a Bruker-AXS CCD 1000
diffractometer. A semi-empirical absorption correction was employed
(Tmin ˆ 0.546246, Tmax ˆ 1.000000).[17] The structure was solved by
direct methods (SHELXS-97)[18], and 340 parameters were refined by
the least-squares method on F 2.[19] Maximum residual electron
density: 1.068 eŠ 3, R1 (for F > 2s(F))ˆ0.0375 and wR2ˆ0.0990
(all data) with R1ˆSjFo j jF j SjF j and wR2ˆ(Sw(Fo2 Fc2†2/
/
c
o
Sw(Fo2†2)0.5. Crystallographic data (excluding structure factors) for the
structure reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publica-
tion no. CCDC-149434. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk).
.
.
‡
‡
(Me3Si); EI-MS (70 eV): m/z (%): 434 (21) [M ], 377 (2) [M
Et N2],
[12] a) We consider bond lengths close to the sum of the covalent radii for
the two elements involved to be normal; b) R. Chauvin, J. Phys. Chem.
1992, 96, 9194 ± 9197.
321 (100) [ArGe], 291 (42) [ArGe 2Me], 220 (52) [ArGe NEt2 Et],
177 (35) [ArGe 2NEt2]; IR (C6D6): nÄ ˆ 1994 cm 1 (CN2).
[13] For a review on carbene chemistry, see W. Kirmse in Carbene
Chemistry (Ed.: A. T. Blomquist), Academic Press, New York, 1971,
pp. 267 ± 362.
[14] D. Bethell, R. D. Howard, J. Chem. Soc. B 1969, 745 ± 748.
[15] S. M. Stogner, R. S. Grev, J. Chem. Phys. 1998, 108, 5458 ± 5464.
[16] Y. Apeloig, M. Karni, Organometallics 1997, 16, 310 ± 312.
[17] SADABS, Program for Absorption Correction, Bruker-AXS.
[18] G. M. Sheldrick, Acta Crystallogr. Sect. A 1990, 46, 467 ± 473.
[19] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Göttingen, 1997.
2: The same procedure as for 1 was used for 2, which was recrystallized
from pentane at 208C (40% yield). M.p. 788C (decomp); 1H NMR
(400.1 MHz, C7D8, TMS): d ˆ 0.37 (s, 9H, Me3Si), 1.02 (d, 3J(H,H) ˆ 7.0 Hz,
12H, CH(CH3)2), 1.06 (d, 3J(H,H) ˆ 7.0 Hz, 12H, CH(CH3)2), 3.27 (sept,
3J(H,H) ˆ 7.0 Hz, 4 H, CH(CH3)2), 3.72 (s, 4H, CH2), 7.08 ± 7.17 (m, 3H,
ArH); 13C NMR (100.6 MHz, C7D8, TMS): d ˆ 0.04 (CH3Si), 20.63
(CH(CH3)2), 21.45 (CH(CH3)2), 30.15 (CN2), 51.20 (CH(CH3)2), 54.36
(CH2), 124.19 (m-C), 127.67 (p-C), 147.10 (o-C), 158.39 (ipso-C); 29Si NMR
(39.8 MHz, C7D8, TMS): d ˆ 0.06 (Me3Si); EI-MS (70 eV): m/z (%): 490
.
.
.
‡
‡
‡
(12) [M ], 447 (4) [M
iPr], 419 (5) [M
iPr N2], 377 (100) [ArGe];
IR (C6D6): nÄ ˆ 2001cm 1 (CN2).
Received: September 11, 2000 [Z15784]
954
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4005-0954 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 5