Organometallics 1989, 8, 2606-2608
2606
Photochemistry of a Matrix-Isolated Geminal Diazide. Dimethylgermylene Jacques Barrau,*slasb Dennis L. Bean," Kevin M. Welsh,'c Robert West,*Sic and Josef Michl**'a Center for Structure and Reactivity, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712- 1167, and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 Received December 8, 1988
UV irradiation of matrix-isolated dimethyldiazidogermane [Me2Ge(N&] permits identification of dimethylgermylene (Me2Ge) by its IR and UV-vi'sible spectra. IR of the annealed matrix shows peaks attributable to the known dimer MezGe=GeMez. Chemical trapping experiments in room-temperature solutions are compatible with the possibility that here, too, free MezGeis generated by the irradiation of MezGe(W2.
Introduction
Scheme I. Chemical Trapping Experiments
Divalent compounds of elements of group 14 have been the subject of considerable experimental and theoretical s c r ~ t i n y . ~Quite . ~ a few reports on the direct observation of organosilylenes have appeared since the initial observation of dimethylsilylene," but spectroscopic data on simple organogermylenes remain rather limited. A few dialkylgermylenes and diarylgermylenes have been characterized by UV," NMR,l0J1and EXAFS12spectroscopy, but, to our knowledge, there is no precedent for IR observation. We report herein the IR and UV spectroscopic characterization of matrix-isolated dimethylgermylene, MezGe (11, which has been frequently postulated as intermediate in thermal and photochemical p r o c e ~ s e s . ~ ~ J ~
h (254 or 248 nm)
Me2e(N3)2
c
2
1
5 (25%)
I
Results and Discussion The geminal diazide Me2Ge(N& (2) was chosen as a photochemical precursor to 1. This selection was inspired by the known photochemical conversion of certain geminal diazides in the carbon and silicon series, which yield (1)(a) The University of Texas at Austin. (b) On sabbatical leave from Laboratoire de Chimie des OrganominBram, Universit.5 Paul Sabatier, Toulouse, France. (c) University of Wisconsin. (2)Jones, M., Jr., Mow, R. A., Eds. Reactive Intermediates; WileyInterscience: New York, 1978;Vol. 1, 1981;Vol. 2,1985;Vol. 3. (3)Satg6, J. Pure Appl. Chem. 1984,56,137.Neumann, W. P. In The Organometallic and Coordination Chemistry of Germanium, Tin and Lead; Gielen, M., Harrison, P. G., Eds.; Freund Tel Aviv, 1978. Marx, R.; Neumann, W. P.; Hillner, K. Tetrahedron Lett. 1984,25,625. (4)Drahnak, T. J.; Michl, J.; West, R. J.Am. Chem. SOC.1979,101, 5427. (5)Sakurai, H.; Sakamoto, K.; Kira, M. Chem. Lett. 1984,1379. (6)Ando, W.; Tsumuraya, T.; Sekiguchi, A. Chem. Lett. 1987,317. Ando, W.; Itoh, H.; Tsumuraya, T.; Yoshida, H. Organometallics 1988, 7, 1880. (7)Egorov, M. G.; Dvomikov, A. S.; Kolesnikov, S. P.; Kuz'min, V. A.; Nefedov, D. M. Izv. Akad. Nauk USSR, Ser. Khim. 1987,1114. (8)Konieczny, S.;Jacobs, S. J.; Braddock Wilking, J. K.; Gaspar, P. P. J. Organomet. Chem. 1988,341,C17. (9)Tomoda, S.;Shimoda, M.; Takeuchi, Y.; Kajii, Y.; Obi, K.; Tanaka, I.; Honda, K. J. Chem. SOC.,Chem. Commun. 1988,910. (10)Goldberg, D.E.; Harris,D. H.;Lappert, M. F.; Thomas, K. M. J. Chem. SOC.,Chem. Commun. 1976,261.Davidson, P. J.; Harris, D. H.; Lappert, M. F. J. Chem. SOC.,Dalton Trans. 1976,2268. Hitchcock, J. B.; Lappert, M. F.; Miles, S. J.; Thorne, A. J. J. Chem. Soc., Chem. Commun. 1984,224,480. (11)Lange, L.; Meyer, B.; du Mont, W. W. J. Organomet. Chem. 1987, 329,C17. (12)Mochida, K.; Fujii, A,; Tsuchiya, N.; Tohji, K.; Udagawa, Y. Organometallics 1987,6, 1811. (13)For leading references see: Ma, E. C.-L.; Kobayashi, K.; Barzilai, M. W.; Gaspar, P. P. J. Organomet. Chem. 1982,224,C13. Kira, M.; Sakamoto,K.; Sakurai, H. J. Am. Chem. Soc. 1983,105,7469.Schriewer, M.; Neumann, W. P. J. Am. Chem. SOC.1983,105,897. Michels, E.; Neumann, W. P. Tetrahedron Lett. 1986,27,2455. Neumann, W.P.; Michels, E.;K&her, J. Tetrahedron Lett. 1987,28,3783. (14)Barrau, J.; El Amine, M.; Rima, G.; Sat& J. J. Organomet. Chem. 1984,277,323.
0276-733318912308-2606$01.50/0
[Me2Ge:]
LiAIH,
Me2GeH-GeHMe2 + MePGeHP
Table I. Dimethslgermslene (1) Vibrations no. 1 2 3 4
freq, cm-* 2987 2974 2957 2897 1234 1217 1205 1195 882 817 541 527
5 6 7 8 9 10 11 12
intensity (relative) W 9 9
W
m W
m W
m m W
vs
assignt C-H stretch C-H stretch C-H stretch C-H stretch CH, deformation CHI deformation CH, deformation CH, deformation in-plane CH, rock in-plane CHI rock Ge-C stretch Ge-C stretch
carbenes15and silylene~,'~J'respectively. Chemical Trapping Experiments. Preliminary experiments demonstrated that 1 might indeed be formed from 2. Thus 2 was irradiated a t 254 or 248 nm in hydrocarbon solution a t room temperature or glass a t 77 K in the presence of excess germylene-trapping agents. Significant yields of the trapping adducts expected from 1 were isolated (Scheme I), suggesting but not proving the intermediacy of 1. With l,&butadiene in benzene solution, we isolated a small yield of the formal 1:l 1,4-cycloadduct 3 and a fair yield of the mixed cis and trans germacyclopentanes 4 ~~
~
~
~~~
~
~~
~
(15)Barash, L.; Wasserman, E.; Yager, W. A. J. Am. Chem. Soc. 1967, 89, 3931. (16)VanEik, H.; Raabe,G.; Michalczyk, M. J.; West, R.; Michl, J. J. Am. Chem. SOC.1985,107,4097. (17)Welsh, K. M.; Michl, J.; West, R. J. Am. Chem. SOC.1988,110, 6689.
0 1989 American Chemical Society
Photochemistry of a Matrix-Isolated Geminal Diazide
Ii /I !
AO.'I
I 3100
moo
2900
2800
Organometallics, Vol. 8, NO. 11, 1989 2607
'
) 1,
'cn
1)
Figure 1. The IR spectrum of 1. The sinusoidal background in the high-frequency region is due to interference fringes.
expected from a 1,2-addition followed by insertion of a second molecule of butadiene into the germacyclopropane intermediateals Trapping with a (MezGeO), mixture (n = 3, >75%; n = 4,5,
