Organometallics 1989,8, 2759-2766 166-168 OC; 'H NMR (CDClJ 6 1.97 (t, 12 H, SnCH,), 2.37 (q, 6 H, CHJ. Anal. Calcd for CJ-I18Cl&h3: C, 15.5;H, 2.59. Found C, 15.32;H, 2.72. Complex of 4 with [Ph+N=PPh3]+Cl- (6). Into a solution (0.115g, 0.2 mol) of 4 (0.127g, 0.2 mol) and [Ph*N=PPh,]+Clin 3 mL of methylene chloride was added 3 mL of hexane. Slow evaporation led to precipitation of an oily product that solidified to a glasslike product: 'H NMR (CDC13)6 0.70 (s, 9 H, ,J('lSSn-C-H) = 59.6 Hz, SnCH,), 1.65 (t, 12 H, 2J(11gSn-C-H)= 62.0Hz, SnCHJ, 2.38 (q,6H, 3J(11%n-C-C-H) = 110.7 Hz,CH,), 7.70 (m, 12 H, o-Ph), 7.53 (m, 18 H, m- and p-Ph); 13C NMR (CHC13) 6 1.68 (1J(11gSn-13C)= 389.3 Hz, SnCH,), 28.36 ('J(11sSn-13C)= 456.6 Hz, 3J(11gSn-C-C-13C) = 49.6 Hz, SnCH,), 22.38 (2J(11BSn-C-'3C)= 27.0 Hz, CH2). Complex of 5 with [Ph3P=N=PPh3]+Cl- (7). To 3 mL of methylene chloride and 2 mL of hexane were added 78.0 mg (0.136 "01) of [Ph+N=Ph3]+Cl- and 95.4mg (0.136mL) of 5. Slow evaporation of the solvent yielded 155 mg (90%) of colorless crystals: mp 224-225 OC; 'H NMR 6 2.16 (t, 12 H, 2J(11gSn-C-H) = 71.3 Hz,SnCH2),2.59 (q, H, 3J(11%n-C-C-H)= 187.7 Hz,CHJ, 7.46 (m,18 H, m- and p-Ph), 7.65 (m, 12 H, o-Ph); 13C NMR (CDC13)6 38.65 (lJ(llgSn-lSC)= 592.6 Hz, 3J(11sSn-C-C-C) =
2759
50.1 Hz SnCH,), 21.91 (2J(11gSn-C-C) = 41.6 Hz, CH,). Anal. Calcd for C45H48NP2Sn3; C, 42.58;H, 3.78. Found C, 42.42;H, 3.71.
Acknowledgment. K.J. thanks the International Research and Exchanges Board (Princeton, NJ) for a grant. We also thank Professor Shelton Bank for valuable suggestions and the reviewers for helpful criticisms. Registry No. 1, 123126-09-0; 2, 123126-05-6; 3,85443-05-6; 4, 123126-06-7; 5, 123126-07-8; 6, 123126-11-4;7, 123126-13-6; [Ph3P=N=PPh3]+Cl-, 21050-13-5;1,3-bis(trimethylstnyl)propane, 35434-81-2;(trimethylstannyl)sodium,16643-09-7;1,3dichloropropane, 142-28-9;dimethyldichlorostannane, 753-73-1; bis((2-methoxycarbonyl)ethyl)dimethylstannane,115152-95-9; bis(3-hydroxypropyl)dimethylstannane,123126-08-9.
Supplementary Material Available: Tables of atomic coordinates and equivalent isotropic displacement parameters, bond distances, bond angles, and H-atom coordinates and isotropic displacement parameters (6 pages); a listing of observed and calculated structure factors (15pages). Ordering information is given on any current masthead page.
Electronic Absorption Spectra of Diorganogermylenes in Matrices: Formation of Diorganogermylene Complexes with Heteroatom-ContainingSubstrates Wataru Ando, Hiroyuki Itoh, and Takeshi Tsumuraya Department of Chemistty, The University of Tsukuba, Tsukuba, Ibaraki 305, Japan Received March 31. 1989
Diorganogermylenes were generated in hydrocarbon matrices at 77 K by the photolysis of 7germanorbornadienes la-e or bis(trimethylsily1)germanes 2a-g. The germylenes show electronicabsorption bands at 420-558 nm. The germylenes react with heteroatom-containing substrates (bo,RzS,R3P,R3N, RCl, and ROH) to form adducts, which show characteristic absorption bands at shorter wavelengths than those of germylenes. Introduction Divalent compounds of elements of group 14 have been the subject of considerable interest in recent y e a r ~ . l - ~ Although diorganogermylenes have been postulated as reactive intermediates in many reactions,H spectroscopic
Scheme I 8
P'
1 a:R=R' =Me
(1) Jones, M., Jr., Moss, R. A., Eds. Reactioe Intermediates; WileyInterscience: New York 1978, Vol. 1; 1981, Vol. 2; 1985, Vol. 3. (2) SatgB, J.; Massol, M.; Riviere, P. J. Organomet. Chem. 1973,56, 1. (3) Neumann, W. P. In The Organometallic and Coordinution Chemistry of Germanium, Tin, and Lead; Gielen, M., Harrison, P. G., Eds.; Freund: Tel Aviv, 1978. (4) Mars, R.; Neumann, W. P.; Hillner, K. Tetrahedron Lett. 1984,25, 625. (5) Ma, E. C.-L.; Kobayashi, K.; Barzilai, M. W.; Gaspar, P. P. J. Organomet. Chem. 1982,224, C13. (6) (a) Schriewer, M.; Neumann, W. P. J. Am. Chem. SOC.1983,105, 897. (b) Khher, J.; Neumann, W. P. J. Am. Chem. SOC.1984,106,3861. (c) Khher, J.: Neumann. W. P. Ormnometallics 1985.4. 400. (d) Michela, E.; Neumann, W. P. Tetrahe-dron Lett. 1986,27, 2455. ( e ) Neumann, W. P.; Michels, E.; Khher, J. Tetrahedron Lett. 1987,28, 3783. (f)Billeb, G.; Neumann, W. P.; Steinhoff, G. Tetrahedron Lett. 1988,29, 5245. (7) Barrau, J.; El Amine, M.; Rima, G.; Satg6, J. J. Organomet. Chem. 1984,277,323.
(8) (a) Ando, W.; Tsumuraya, T.; Sekiguchi, A. Tetrahedron Lett.
1985,26,4523. (b) Ando, W.; Tsumuraya, T. Tetrahedron Lett. 1986,27, 3251. (c) Ando, W.; Tsumuraya, T.; Goto, M. Tetrahedron Lett. 1986, 27,5105. (d) Tsumuraya, T.; Sato, S.; Ando, W. organometallics 1989, 8, 161. (e) Ando, W.; Tsumuraya, T. Organometallics 1989,8,1467. (0 Ando, W.; Tsumuraya, T. J. Chem. SOC.,Chem. Commun. 1989, 770.
0276-7333/89/2308-2759$01.50 f0
b:R=R'=Et C:R=R~="B~
d:R=?h, R'=Me e:R=R'=Ph
2a:R=R'=?h b: R-R ' = Ta 1 (4-me t h y 1 p h e n y l ) c:R=Mes(2,4,6-trimethylphenyl), d:R=R'=Xy(2,6-dimethylphenyl) e:R=R'=Ar(2,6-diethylphenyl)
R'=t8u
f:R=R'=Mes
g:R=R1=Ar'(2,4,6-tr~isopropylphenyl)
data on diorganogermylenes remain rather limited. Dimethylgermylene and some other dialkyl- and diarylgermylenes have been observed by UV s p e c t r ~ s c o p y ~ ~ J ~ ~ ~ (9) (a) Kira, M.; Sakamoto, K.; Sakurai, H. J. Am. Chem. SOC.1983, 105, 7469. (b) Sakurai, H.; Sakamoto, K.; Kira, M. Chem. Lett. 1984, 1379.
1989 American Chemical Society
2760 Organometallics, Vol. 8, No. 12, 1989
Ando et al. Scheme I1 Me Me
= 3 1 7 nm
hv 254 nm
\
3-',P, Ph
i
77 )KAmax=420 nm
l a -
Scheme I11
zc:R=Mes,
300
400
500
600
d:R=R'=Xy
406
e: R-R
e: R=R'=Ar
400
=Ar
700
f:R=R'=Mes
f:R=R'=Mes
406
(n.1
g:R=R'=Ar'
g:R=R'=Ar'
4 16
Figure 1. (A) After photolysis of la with a low-preasure mercury lamp (254 nm) for 15 min in 3-MP at 77 K. (B) After annealing the matrix and recooling to 77 K. In (A) and (B), the starting material was subtracted.
and some germylenes substituted with bulky groups have been characterized by NMR14J6and EXAFS spectroscopy.16 But, there is no systematic study of the effect of the substituent on the spectroscopic properties of germylenes. Another interesting problem in germylene chemistry is whether diorganogermylenes form stable complexes with heteroatom-containing substrates." In 1982 Satg6 et al. reported the preparation of stable diarylgermylene complexes from dehydrochlorination of diarylchlorogermanes by triethylamine.18 However, recently, Masamune et al. claimed that bis(2,6-diethylphenyl)germylenegenerated from a bis(trimethylsily1)germane or a cyclotrigermane did not form a stable complex with triethylamine at room temperat~re.'~ We report here the matrix isolation and electronic absorptions of various diorganogermylenes in hydrocarbon matrices at 77 K including the formation of diorgano(IO) For the p r e l i m i i reports of matrix isolation of germylenes,see: (a) Ando, W.; Tsumuraya, T.; Sekiguchi, A. Chem. Lett. 1987,317. (b) Ando, W.; Itoh, H.; Tsumuraya, T.; Yoshida, H. Organometallics 1987, 7 , 1880. (11) Konieczny, S.; Jacobs, S. J.; Braddock Wilking, J. K.; Gaspar, P. P. J. Organomet. Chem. 1988, 341, C17. (12) Mochida, K.; W h , M.; Nakadaira, Y.; Sakaguchi,Y.; Hayashi, H. Organometallics 1988, 7, 1869. (13) Tomoda, S.; Shimoda, M.; Takeuchi, Y.; Kajii, Y.; Obi, K.; Tanaka, I.; Honda, K. J. Chem. SOC.,Chem. Commun. 1988,910. (14) Lange, L.; Meyer, B.; du Mont, W.-W. J.Orgummet. Chem. 1987, 329. C17. (15)Davidson, P. J.; Harris, D. H.; Lappert, M. F. J. Chem. Soc., Dalton Trans. 1976, 2268. (16) Mochida, K.; Fujii, A.; Tsuchiya, N.; Tohji, K.; Udagwa, Y. Organometallics 1987, 6, 1811. (17)Dihalogermylenes form stable complexes with heteroatom-containing substrates, and some of them are characterized by X-ray crystal analysis. (a) du Mont, W.-W.; Neudert, B.; Rudolph, C.; Schumann, H. Angew. Chem., Int. Ed. Engl. 1976,15,308. (b) King,R. B. Imrg. Chem. 1963,2,199. (c) Inoguchi, Y.; Okui, S.; Mochida, K.; Itai, A. Bull. Chem. SOC.Jpn. 1985, 58, 974. (d) Jutzi, P.; Hoffman, J.; Brauner, D. J.; Kruger, C. Angew. Chem., Int. Ed. Engl. 1973, 12, 1002. (e) Kulishov, V. I.; Bokii, N. G.; Nefedov, 0. M.; Kolesnikov,S. P.; Perl'mutter, B. L. Zh. Strukt. Khim. 1970, 11, 61. (18) Riviere, P.; Castel, A.; Satg6, J. J. Organomet. Chem. 1982,232, 123. (19) Collins, S.; Murekami, S.; Snow, J. T.; Masamme, S. Tetrahedron Lett. 1985,26, 1281. In this communication the authors also reported that reactioni of diarylchlorogermanes with triethylamine did not form germylene-triethylamine adducts. ~
R ' = h
d :R=R ' =Xy
germylene complexes with heteroatom-containing substrates, which are characterized by electronic absorption spectra.1° Results and Discussion Electronic Absorption Spectra of Diorganogermylenes in 3-Methylpentane (3-MP) at 77 K. Germylenes were generated by UV photolysis at 254 nm of 7-germanorbornadienes la-e or bis(trimethylsily1)germanes 2a-g (Scheme I).2o Although generation of germylenes by the thermolysis of 7-germanorbornadienes is well-known,6*8a-ephotochemical decomposition has no precedent. We found that 7-germanorbornadienes also were effective photochemical precursors of germylenes.21 Irradiation of a cyclohexane solution of 2,3-benzo-7,7dimethyl-1,4,5,6-tetraphenyl-7-germanorbornadiene (la) (0.3 "01) and 2,3-dimethyl-l,3-butadiene(3.0 mmol) with a low-pressure mercury lamp at room temperature produced 1,1,3,4-tetramethyl-1-germacyclopent-3-ene (3) in 90% yield along with 1,2,3,4-tetraphenylnaphthalene.The formation of 3 can be rationalized by the reaction of dimethylgermylene with 2,3-dimethyl-l13-butadiene. Irradiation of la in 3-MP at 77 K for 15 min led to bright yellow coloration of the glass, and two absorptions were produced at 317 and 420 nm (Figure 1). These absorption bands were indefinitely stable at 77 K in the 3-MP matrix. When the 3-MP glass was melted, the 420-nm maximum rapidly diminished. The 317-nm band remained unchanged even after the solution was warmed to room temperature and recooled to 77 K. These results indicate that two products, one stable and one thermally unstable, are formed in the photolysis of la at 77 K. Since it is known that dimethylgermylene is a yellow species with A, at 430 nmlgbthe yellow species from la may be ascribed to dimethylgermylene (Scheme 11). The 317-nm band is due to l12,3,4-tetraphenylnaphthalene. Convincing evidence for identification of the yellow species as dimethylgermylene is provided by the results of the following trapping experiment. About 1 mg of la (20) For simplicity, we use the following short-hand notations in this paper: Tol, 4-methylphenyl; Mes, 2,4,6-trimethylphenyl; Xy, 2,6-dimethylphenyl; Ar, 2,6-diethylphenyl; Af, 2,4,6-triisopropylphenyl. (21) Very recently, photochemical generation of dimethylgermylene from 7-germanorbomadiene la was reported. Kkher, J.; Lehnig, M.; Neumann, W. P. organometallics 1988, 7, 1201.
Organometallics, Vol. 8, NO.12, 1989 2761
Diorganogermylenes
Table I. Electronic Abrorptions of Germylenes in 3-MPat 77 K color of the matrix precursors germylenes hx/nm yellow la 420 Me,Ge: lb yellow 440 Et,Ge: IC yellow nB~2Ge: 440 yellow Id 440 MePhGe: le, 2a yellow-orange PhzGe: 466 2b yellow-orange To1,Ge: 47 1 2c red Mes(*Bu)Ge: 508 2d purple Xy,Ge: 543 2e purple Ar2Ge: 544 2f purple Mes,Ge: 550 purple-blue Ar',Ge: 558 2g ~~
~
~
~
"Abbreviations: Tol, 4-methylphenyl; Xy, 2,6-dimethylphenyl; Ar, 2,6-diethylphenyl; Mes, 2,4,64rimethylphenyl; Ar', 2,4,6-triisopropylphenyl.
400
500
600
700
(nm)
Figure 2. (A) After photolysis of 2f with a low-pressure mercury lamp (254 nm) for 30 min in 3-MP at 77 K. (B) After annealing the matrix and recooling to 77 K. In (A) and (B), the starting material was subtracted.
and 0.5 mL of 2,3-dimethyl-l,3-butadiene were dissolved in 3.5 mL of 3-MP, cooled to 77 K, and the resulting matrix was irradiated at 254 nm, producing the same two bands at 317 and 420 nm. When the matrix was melted, the 420-nm band immediately disappeared. Again, the 317 nm band was unaffected by increasing temperature. Analysis of the photolysate by GC-MS showed that 3 had been formed. Diethyl-, dibutyl-, methylphenyl-, and diphenylgermylenes were generated by the same method in 3-MP matrices at 77 K. Since photolysis of a bis(trimethylsily1)germane was known previously as a photochemical route to a germylene,lBaryl group substituted germylenes were generated by this method. We could easily introduce bulky groups on the germanium atom of bis(trimethylsilyl)germanes, and, therefore, germylenes substituted with bulky groups were generated from these compounds. Irradiation of dimesitylbis(trimethylsily1)germane (2f) in 3-MP at 77 K with a low-pressure mercury lamp led to the formation of a band at 550 nm attributed to dimesitylgermylene. The color of the matrix became an intense purple. This absorption band did not decrease at 77 K on prolonged standing. However, this band disappeared on at 406 careful annealing to give a yellow species with ,A, nm at 77 K due to tetramesityldigermene (Figure 2). This absorption band is identical with that obtained from the photolysis of hexamesitylcyclotrigermane which gives tetramesityldigermene.22 Other germylenes substituted with bulky groups such as bis(2,6-dimethylphenyl)-,bis(2,6-diethylphenyl)-, tert-butylmesityl-, and bis( 2,4,6-triisopropylpheny1)germylenes dimerized to the corresponding digermenes when the matrices containing these germylenes were annealed as shown in Scheme III.23 (22) Tsumuraya, T.; Sato, S.; Ando, W. Organometallics 1988,7,2015. (23) The bands due to digermenes were identical with those obtained from the photolysis of the corresponding cyclotrigermanes. (RR'Ge)B
RR'GdeRR'
(a) R = R' = B,&dimethylphenyl: Maeamune,S.; Hanzawa, Y.; Williams, D. J. J. Am. Chem. SOC. 1982,104,6136. (b) R = R' = 2,&diethylphenyl: Snow, J. T.; Murakami, S.; Masamune, S.; Williams, D. J. Tetrahedron Lett. 1984,25,4191. (c) R = Mes, R' = 'Bu: Tsumuraya, T.; Ando, W., unpublished results.
Electronic absorptions of germylenes obtained by the photolysis of 7-germanorbornadienes or bis(trimethy1sily1)germanes at 77 K in 3-MP glasses are listed in Table I.24 The germylenes are stable in 3-MP matrices at 77 K and show electronic absorptions at 420-558 nm. As in the case of silylenes, these absorptions are probably due to n-p
transition^.^^^^^
lAl
'Bi
The most interesting point is what is the effect of substituent on the n-p transition. The introduction of aryl groups on germanium resulted in red shifts compared to alkylgermylenes. This is probably due to the stabilization of the excited state. When alkyl groups are substituted on aryl groups of germylenes, slight red shifts are observed. It is interesting to note that dramatical red shifts are observed for bulky substituents which increase the steric congestion around the germanium enforcing a (a, angle between two substituents of germylene) to widen. The following three series demonstrate this point: MePhGe (440 nm) C MestBuGe (508 nm); Ph2Ge (466 nm) < XyzGe (543 nm), Ar2Ge (544 nm); Me%Ge (550 nm) C M2Ge (558 nm). These results indicate that the angle around the divalent germanium atom affects strongly the first electronic transition. Theoretical investigation for H2Ge showed that the equilibrium value of a is much larger in the excited 'B1state than in the 'A, state (123.2' and 92.6', respectively, CI calculations).n As CY increases, the energy of the 'Al state rises and that of the excited 'B1 state drops. Thus, as a increases, a red shift is observed. These results are consistent with those obtained for ~ i l y l e n e s . ~ ~ . ~ Matrix Effect. Dimerization of Germylenes at 77 K in Soft MatricesJ8 As previously mentioned, germylenes are stable at 77 K in 3-MP matrices and do not dimerize to digermenes. On the other hand, dimerization of germylenes took place in isopentane (IP)/&MP matrices (24) The molar extinction coefficients cannot be given for the methodological reasons. (25) Michalczyk, M. J.; Fink, M. J.; De Young, D. J.; Carlson, C. W.; Welsh, K. M.; West, R.; Michl, J. Reu. Silicon, Germanium, Tin Lead Compd. 1986, 9, 1, 75. (26) Apeloig, Y.; Karni, M. J. Chem. SOC.,Chem. Common. 1986,1048. (27) Barthelat, 3.-C.; Roch, B. S.; Trinquier, G.; Satg6, J. J. Am. Chem. SOC.1980, 102, 4080. (28) Dimerizationof silylenes at 77 K in soft matrices, see: Sekiguchi, A.; Hagiwara, K.; Ando, W. Chem. Lett. 1987, 209.
2762 Organometallics, Vol. 8, No. 12, 1989
Ando et al.
Table 11. Dimerization of Dimesitylgermylene in S - M P / I P Matrices ratio half-life of viscosity at (3-MP/IP) Mes2Ge:, min 77 K b 9.4 x 10" 110 b 5.9 x 108 111 very slow 1.8 X IO* 416 320 5.2 X 10' 317 50 1.8 x 107 218
A-406 nm
'The viscosity data were taken from ref 29. bDimerization of the germylene did not take place. Scheme I V R2Ge(SLMe3)Z
hv(254nnm) S-MP/IP.77K
R2Ge:
300
at 77 K without annealing. Thus, a mixture of IP and 3-MP containing dimesitylbis(trimethylsily1)germane (20 was placed in a quartz cell and cooled to 77 K. Irradiation of the resulting matrix for 15 min led to the generation of the two absorption bands due to dimesitylgermylene (550 nm) and tetramesityldigermene 4f (406 nm). When the matrix was allowed to stand in the dark at 77 K, the absorption band a t 550 nm due to dimesitylgermylene gradually diminished as a function of time with concurrent formation of an absorption band at 406 nm due to tetramesityldigermene. The band at 406 nm grows at almost same rate as the band at 550 nm decreases. These results indicate that the germylene can dimerize in soft matrices even at 77 K without annealing. The relation between the half-life of dimesitylgermylene and the viscosity of the matrix is given in Table 11, which shows that the dimerization of germylene is strongly dependent on the viscosity of the matrix.29 Similarly, other diorganogermylenes dimerize in soft matrices. Since 3-MP is a hard matrix (viscosity: 9.4 X 10" P at 77 K), dimesitylgermylene cannot dimerize in a 3-MP matrix. The above results indicate that intermolecular reactions proceed in soft matrices even at 77 K. Therefore, this method can be adapted to the generation of thermally unstable molecules by the reactions of germylenes. We next attempted to observe diorganogermylene complexes with various heteroatom-containing substrates by this soft matrix technique. Spectroscopic Characterization of Diorganogermylene Complexes with Heteroatom-Containing Substrates.30 When bis(trimethylsily1)germane 2f was photolyzed with a low-pressure mercury lamp for 40 min at 77 K in a 3-MPIIP (3/7) matrix containing triethylamine, a new band at 414 nm appeared together with a (29) Lambardi,J. R.; Raymonda, J. W.; Albrecht, A. C. J. Chem. Phys. 1964,40, 1148. (30) Formation of Lewis base adducts to diorganosilylenes, see: (a)
Ando, W.; Sekiguchi, A.; Hagiwara, K.; Sakakibara, A.; Yoshida, H. Organometallics 1988, 7, 558. (b) Gillette, G. R.; Noren, G. H.; West, R. Organometallics 1987,6, 2617. (c) Gillette, G. R.; Noren, G. H,.; West, R. Organometallics 1989, 8, 487. (d) Levin, G.; Das, P. K.; Lee, C. L. Organometallics 1988,7,1231. (e) Levin, G.; Das,P. K.; Bilgrien, C.; Lee, C. L. Organometallics 1989,8, 1206.
400
500
600
700 (nm)
Figure 3. (A) After photolysis of 2f with a low-pressure mercury lamp (254 nm) for 40 min in the presence of triethylamine in 3-MP/IP a t 77 K. (B)The above sample was allowed to stand in the dark a t 77 K for 30 min. (C) After annealing the matrix and recooling to 77 K. In (A)-(C), the starting material was subtracted. Table 111. UV Absorption Maxima (nm)of Diornanwermvlene Comdexes' MezGe: PhzGe: MeeGe: Ar2Ge: Ar'zGe: 3-MPb 420 466 550 544 558 Bu~P 306 314 334 334 349 356 363
Gc)N MezS
326 332
348 352
357 359
357 366
325
360 (373)'
369
376
341
374
495
508
544
392
403
538
532
553
Cs Me
U
a ,A in 3-MP/IP(3/7) at 77 K. , A 2-MeTHF at 77 K.
in 3-MP at 77 K. A,
in
band at 550 nm due to dimesitylgermylene. After being allowed to stand in the dark at 77 K for 30 min, the band due to dimesitylgermylene disappeared and the 414-nm band grew as shown in Figure 3. The absorption band at 414 nm did not decrease at 77 K on prolonged standing. However, when the matrix was annealed, the 414-nm band disappeared immediatelyand a new band was formed with ,A, at 406 nm, which was assigned to tetramesityldigermene. On the basis of these results, it is quite reaat 414 sonable to assume that the intermediate with ,A, nm most probably is the dimesitylgermylene-triethylamine complex (5f)(Scheme IV). Similar results were obtained for 2g, and a band due to the germylene-amine complex 5g was observed at 445 nm. When dimethyl sulfide was used for donor, formation of a germylene-ulfide complex was observed. Irradiation of 2g in a 3-MP/IP (317) matrix containing dimethyl sulfide at 77 K for 60 min led to the formation of a band
Organometallics, Vol. 8, No. 12, 1989 2763
Diorganogermy lenes Scheme V
X m a x = 6 9 0 nm
RZGe:
t
'Bu2C=C=S
A=333 nn
V ( 2 5 4 nm)
~
t
3-MP/IP
-
'BuZC=C=S-GeRZ
R-Ph, ~ , , , ~ ~ = 5 6nm 5
Mes2 R=Hes. h m a , = 5 8 0 nm
Chart I R" X
Y
I
-.
GeGlp
8
U
7
at 357 nm, which was assigned to the diarylgermylenedimethyl sulfide complex. The band due to the germylene was not observed. When the matrix was carefully annealed, the band of the complex diminished gradually and a new band of digermene 4g appeared. The germylenesulfide complex seems to be stable compared to the germylene-amine complex. New stable complexes of dimethyl- and diarylgermylenes with heteroatom-containing substrates were observed in matrices at 77 K and are analogous to the reaction between silylenes and donors (Table III).30 Bands due to germylene complexes were observed ranging widely from 306 to 553 nm. The bands of germylene complexes were shifted to shorter wavelengths compared to those of the corresponding free germylenes. These results are markedly in contrast to those obtained for germylene-thiocarbonyl complexes ("germathiocarbonyl ylide"). In the case of germylene-thiocarbonyl complexes,8diewhich were generated by the photolysis of thiagermiranes or the reactions of germylenes with thiocarbonyl compounds, red shifts compared to germylene were observed (Scheme V). To consider the structures of germylene complexes, the results of crystal structure analyses of dihalogermylene complexes are informative. Crystal structures of diiodoand dichlorogermylenecomplexes such as 6,7, and 8 have been determined to date (Chart I).17 All of these results indicate that the monomeric dihalogermylene unit is coordinated with a lone pair of electrons of the donor. Diorganogermylene complexes seem to have the same structure: a lone pair of electrons of the donor coordinates to vacant p orbital of the germylene ?Al state). The position of the absorption maxima of germylene complexes provides an indication of the strength of the interaction between germylenes and a lone pair of electrons of the donors. Interaction between germylenes and phosphines, amines, sulfides, and ethers seems to be relatively strong, but those of germylene-chloride complexes may be weak. In order to determine the stability of germylene complexes, 2g was irradiated in a matrix (3-MP/IP = 3/7) containing Bu3P or dimethyl sulfide at a higher temperature. In an experiment using Bu3P, only one band at 334 nm appeared at -120 "C after prolonged standing with no bands corresponding to tetrakis(2,4,6-triisopropyl-
400
300
500
700
600
(nm)
Figure 4. (A) After photolysis of 2f with a low-pressure mercury lamp (254 nm) for 30 min in the presence of ethanol in 3-MP/IP at 77 K. (B) The above sample was allowed to stand at 77 K for 30 min. (C) After annealing the matrix and recooling to 77 K. In (A)-(C), the starting material was subtracted. Scheme VI Mes2Ge(SiMe3)2
+
EtOH
h" (254 nm) 3-HP/IP, 7 7 K
M~~~G~...oE~ I
H
2f
Amax-333 nm
lH
annealing
Hes2CG OEt
pheny1)digermene (4g). However, two bands, one corresponding to the germylene complex and one corresponding to the digermene, appeared at -100 "C. Thus, the diarylgermylenephosphine complex is stable below -120 "C but slowly decomposes at -100 "C in solution. The half-life of the bis(2,4,6-triisopropylphenyl)germylene-tributylphosphine complex was 48 s at -79 "C. The diarylgermylene-dimethyl sulfide complex is stable only below -140 "C. Other germylene complexes decomposed when the matrices were melted. The thermal instability of germylene complexes is consistent with Masamune's report. l9 Reaction of Germylenes with Alcohols in Matrices at 77 K. Photolysis of bis(trimethylsily1)germane 2f with a low-pressure mercury lamp at 77 K in a 3-MP/IP (3/7) matrix containing ethanol gave a new band at 333 nm and a band at 550 nm due to dimesitylgermylene. When the matrix was allowed to stand at 77 K, the band of dimesitylgermylene decreased and the 333-nm band grew (Figure 4). On annealing the matrix the band at 333 nm diminished and no new bands were observed. Analysis of the photolysate showed that an insertion product of the germylene into the 0-H bond was obtained.31 On the basis of above results, it is quite reasonable to assume that the intermediate with a band at 333 nm most probably is the dimesitylgermylene-ethanol complex, which is decomposed (31) Dimesitylgermylene generated thermally from cyclotrigermane (see ref Sf) reacts with ethanol to yield an insertion product, ethoxydimesitylgermane.
2764
Organometallics, Vol. 8, No. 12, 1989
Table IV. Absorption Maxima (nm) of Germylene-Alcohol Comdexes in 3-MP/IP (3/7) Matrices germylenes EtOH 'PrOH "UOH tBuOH Ph2Ge: 320 325 332 324 Mes,Ge: 333 3390 35Y 362" 332 34l0 3430 367O Ar2Ge:
Ando et al. Scheme VI1
'
X m a x = ~ 3 0nm
2f -
annealing
OBands due to digermenes were observed when the matrices were annealed.
to the insertion product on annealing (Scheme VI). Electronic absorptions of germylene-alcohol complexes obtained by the reactions of germylenes with alcohols are listed in Table IV. These results are in contrast to those obtained by flash laser photolysis, which indicates that germylenes are not quenched by alcohols."J2 The reason that the results obtained by matrix experiments are quite different from those obtained by flash laser photolyses is not clear at present, but, on the basis of our earlier results for germylene-ether complexes and those obtained by West et al. for silylene-alcohol the species with absorption maxima at 320-367 nm may be assigned to germylene-alcohol complexes. Reactions of Dimesitylgermylene with Allyl Chloride and Allyl Sulfide in Matrices at 77 K. Recently, Lehnig et al. reported the thermal reaction of dimethylgermylene with allyl chloride, which gave an insertion product into the C-C1 bond.21 They proposed that the n-system of the allyl chloride was involved in the first reaction step by formation of a n-complex. Since germylenes can interact with lone pair of electrons of chlorides as indicated previously, we consider that the initial step of that reaction is the formation of the germylene-chloride complex. Therefore, we tried to observe intermediates in this type of reaction by the matrix-isolation technique. Although we could not see a new band due to intermediates when 2f was photolyzed in a matrix (3-MP/IP = 3/7) containing allyl chloride, analysis of the photolysate by GC-MS showed the formation of the insertion product. Photolysis of 2f in a harder matrix (3-MP/IP = 4/6) containing allyl chloride at 77 K produced a broad band at 530 nm. The band corresponding to the digermene was not detected upon annealing, and the insertion product was identified by GC-MS. Since dimesitylgermylenechloride complexes show absorption bands at 495-538 nm, the 530-nm band is probably due to germylene-allyl chloride complex (Scheme VII).32 Irradiation of 2f at 77 K in a matrix (3-MP/IP = 4/6) containing allyl ethyl sulfide led to the formation of a new band at 380 nm. Annealing of the matrix discharged the band with formation of the C-S insertion product of dimesitylgermylene. The species with, , A at 380 nm may be assigned to the germylene-allyl sulfide complex, which rearranges to the insertion product. The above results indicate that the interaction between germylenes and heteroatoms may be involved in the first step of the reactions of germylenes with allylic compound^.^^*^^ Experimental Section General Procedures. All manipulations were carried out under dry argon. lH NMR spectra were recorded on a JEOL PMX 60 SI spectrometer. I3C NMR spectra were recorded on a JEOL FX-9OQ spectrometer. Mass spectra were obtained on Hitachi RMU-6M and JEOL JMS D-300 mass spectrometers. (32)In the control experiment with an alkene we could not observe the alkene-germylene complex. (33)Ishikawa, M.; Katayama, S.; Kumada, M. J. Organomet. Chem. 1983,248, 251. (34)Ando, W.Acc. Chem. Res. 1977, 10, 179.
I
Nes
p./Gk-Cl Mes
-ws.. Et
h u ( 2 5 4 nm)
-2f
+
F S E t
'CeNes2
X m a x = 3 8 0 nm annealing
I
Mes
e G e - S E t YLS
UV-vis spectra were measured on a JASCO Ubest 50 spectrometer. GC analysis was carried out on a Ohkura gas chromatograph with a 8 mm X 2 m glass column of 10% SF-96 on Celite 545. All melting points were uncorrected. Materials. l,l-Dichloro-2,3,4,5-tetraphenylgermole was prepared according to literature procedure^.^^ 2,3-Benzo-7,7-dimethyl-l,4,5,6-tetraphenyl-7-germanorbornadiene (la) was prepared according to literature procedures.h Bis(trimethylsily1)germanes 2a and 2f were synthesized as reported previously.& Hexamesitylcyclotrigermanewas prepared by reductive coupling of Mes&Xl2 with Mg and MgBrz in THF as reported previously.98 3-Methylpentane and isopentane used for matrix studies were stirred with concentrated H2S04 for several hours (to remove olefinic impurities), dried over MgSO,, and distilled under nitrogen from lithium aluminum hydride prior to use. 2-Methyltetrahydrofuran used for matrix studies was distilled from lithium aluminum hydride under nitrogen prior to use. Ether, THF, and benzene used in syntheses were all distilled from lithium aluminum hydride before use. Dichloromethane was dried over calcium chloride and then distilled. Dimethyl sulfide and tetrahydrothiophene were dried over KOH and distilled from sodium. Chlorocyclohexane and chlorobenzene were dried over calcium chloride and then distilled from calcium hydride. Quinuclidine was recrystallized from ether. Tributylphosphine was distilled under reduced pressure before use. Preparation of l,l-Diethyl-2,3,4,5-tstraphenylgermoleand l,l-Dibutyl-2,3,4,5-tetraphenylgermole.A solution of 1,l-dichloro-2,3,4,5-tetraphenylgermole (2.5 g, 5 mmol) and T H F (20 mL) was added to a ethereal solution of EtMgBr (20 mmol) at room temperature. The mixture was hydrolyzed with dilute hydrochloric acid and extracted with ether. After evaporation hexane was added to afford pale yellow crystals of 1,l-diethyl2,3,4,5-tetraphenylgermolein 45% yield: mp 145-146 "C; 'H NMR (CCl,) 6 0.6-1.0 (m, 10 H), 6.3-6.9 (m, 20 H); MS m/e (relative intensity) 488 (100, M+), 459 (36, M+ - Et), 430 (17, M+ - 2Et), 151 (34, EtGeC,). Anal. Calcd for C32H30Ge:C, 78.89; H, 6.21. Found C, 78.95; H, 6.09. Similarly, l,l-dibutyl-2,3,4,5-tetraphenylgermole was synthesized by the reaction of l,l-dichlorc-2,3,4,5tetraphenylgermole with BuMgBr in 92% yield: pale yellow crystals; mp 67-68 OC; 'H NMR (CCl,) 6 0.7-1.5 (m, 18 H), 7.1-7.5 (m, 20 H); MS m/e (relative intensity) 544 (96, M+), 487 (23, M+ - Bu), 430 (M+ 2Bu). Anal. Calcd for C,H3*Ge: C, 79.59; H, 7.05. Found C, 79.54; H, 7.06. Preparation of l-Methy1-1,2,3,4,5-pentaphenylgermole.A THF solution of PhMgBr (10 mmol) was added to a THF (50 mL) solution of l,l-dichlorc-2,3,4,5-tetraphenylgermole (5.0 g, 10 m o l ) at -78 "C. To the mixture was added a ethereal solution of MeMgI (12 mmol). The resulting mixture was hydrolyzed with dilute hydrochloric acid and extracted with ether. After evaporation the residue was subjected to column chromatography (silica gel, hexane) to yield pale yellow crystals of l-methyl-1,2,3,4,5pentaphenylgermole in 13% yield: mp 154-155 "C; 'H NMR (35)Curtis, M.D.J. Am. Chem. SOC.1969, 91, 6011. Tsumuraya, T. J . Chem. SOC.,Chem. Commun. 1987, (36)Ando, W.; 1514.
Diorganogermy lenes (CDC13) 6 0.95 (e, 3 H), 6.4-7.5 (m, 25 H); MS m / e (relative intensity) 522 (100, M+), 507 (33, M+ - Me), 445 (6, M+ - Ph), 430 (17, M+ - Me - Ph). Anal. Calcd for C35HzsGe: C, 80.66; H, 5.42. Found: C, 80.73; H, 5.42. Preparation of 7-Germanorbornadienes lb-d. 7Germanorbornadienes lb-d were prepared by the method of Neumann.& To a mixture of Mg (73 mg, 3 mmol) and 1,l-diethyl-2,3,4,5-tetraphenylgermole(972 mg, 2 mmol) was added 10 mL of dry THF by syringe. After 2-bromofluorobenzene (525 mg, 3 mmol) was added slowly at 0 "C, the mixture was stirred at 20 "C until nearly all of Mg was dissolved. Then, T H F was evaporated, and the residue was dissolved in CHzClzand filtered from the remaining Mg. After evaporation of the solvent, ethanol was added to afford crude lb. Purification by column chromatography (silica gel, benzene/hexane = 1/3) gave pure lb in 41% yield. For l b colorless crystals; mp 116-117 "C; 'H NMR (CDC13)6 0.7-1.8 (m, 10 H), 6.8-7.0 (m, 24 H); MS m / e (relative intensity) 432 (100, Ci&I4Ph4), 355 (8, C1,-,H4Ph3). Anal. Calcd for CBHUGe: C, 81.03; H, 6.08. Found: C, 81.00; H, 6.08. By analogous method, 7-germanorbornadienes ICand Id were prepared from the corresponding germole. For IC: colorless crystals; mp 121-123 "C; 'H NMR (CDC13) 6 0.4-1.7 (m, 18 H), 6.5-7.5 (m, 24 H); MS m / e (relative intensity) 432 (100, Ci,-,H4Ph4), 355 (54, C1&14Ph3). Anal. Calcd for C42H42Ge:C, 81.45; H, 6.84. Found C, 81.42; H, 6.90. For Id: colorless crystals; mp 158 "C; 'H NMR (CDC13) 6 0.31 (s, 3 H), 6.5-7.8 (m, 29 H); MS m / e (relative intensity) 432 (100, C1&I4Ph4),355 (13, C1&14Ph3). Anal. Calcd for C4,H3,Ge: C, 82.45; H, 5.40. Found: C, 82.50; H, 5.55. Preparation of 2,3-Benzo-1,4,5,6,7,7-hexaphenyl-7germanorborna-2,5-diene(le). le was prepared by the reaction of 1,1,2,3,4,5-hexaphenylgermoleand benzyne generated from of the germole 1-aminobenzotriazole and P ~ ( O A C ) ~A ~mixture ' (4.0 g, 6.8 mmol), 1-aminobenzotriazole (1.27 mmol), and CH2C1, (60 mL) was cooled by dry ice-MeOH, and a CHzClzsolution (30 mL) of P ~ ( O A C(9.5 ) ~ mmol) was added to the mixture. The mixture was stirred for about 1 h and filtered. The filtrate was washed with aqueous K&O3 and water. The organic layer was dried by MgS04 and concentrated in vacuo, yielding 1.8 g (41%) of le as a white solid. For le: 'H NMR (CCl,) 6 6.6-8.0 (m, 34 H); MS m / e (relative intensity) 432 (100, CI0H4Ph4).Elemental analyses could not be achieved since compound le was relatively thermally unstable. Thermolysis of l e in the presence of 2,3dimethyl-1,3-butadiene a t 70 "C gave 3,4-dimethyl-l,l-diphenyl-1-germacyclopent-3-ene(45%) and 1,2,3,4-tetraphenylnaphthalene. Preparation of Mes(tBu)GeC12.A THF solution of MesMgBr (11mmol, prepared from MesBr and Mg) was added to a benzene solution of tBuGeC13 (2.36 g, 10 mmol) a t room temperature. The mixture was refluxed for 12 h and allowed to cool. The resulting mixture was hydrolyzed with dilute hydrochloric acid and extracted with ether. Mes(tBu)GeC1, was isolated by Kugelrohr distillation (100 "C, 0.02 Torr) as a white solid: isolated yield 31%; mp 110-113 "C; 'H NMR (CC14)6 1.31 (s, 9 H), 2.30 (s, 3 H), 2.60 (s, 6 H), 6.82 (s, 2 H); MS m / e (relative intensity) 320 (8, M+), 263 (6, M+ - tBu), 57 (100, tBu). Anal. Calcd for C13H2&12Ge: C, 48.83; H, 6.30. Found: C, 48.34; H, 6.39. Preparation of Dichlorobis(2,4,6-triisopropylphenyl)germane. A T H F solution of (2,4,6-triisopropylphenyl)magnesium bromide (21 mmol, prepared from 2,4,6-triisopropylphenyl bromide and Mg) was added to a benzene (10 mL) solution of GeC14 (1.14 mL, 10 mmol) a t room temperature, and the mixture was refluxed for 10 h. The resulting mixture was hydrolyzed with dilute hydrochloric acid and extracted with ether. After evaporation ethanol was added to afford 2.3 g of white powder. Although this white powder is a mixture of Ar',GeClz, Ar',GeClBr, and Ar',GeBr,, we can use conveniently this mixture for the preparation of bis(trimethylsily1)germane 2g. Pure dichlorogermane can be obtained by treating with lithium aluminum hydride followed by chlorination by CClq For AfzGeClz: colorless crystals; mp 130-131 "C; 'H NMR (CDCl,) 6 1.00 (d, J = 7 Hz, 24 H), 1.23 (d, J = 7 Hz, 12 H), 2.75 (sept, J = 7 Hz, 2 H), 3.50 (sept, J = 7 Hz, 4 H), 6.88 (s, 4 H); MS, m / e (relative intensity) 550 (0.1, M'), 347 (14, M+ - Af),312 (5, M+ - Ar' - Cl), 203 (100, (37) Campbell, C.D.;Rees, C. W. J. Chem. SOC.1962, 742.
Organometallics, Vol. 8, No. 12, 1989 2765 Ar'). Anal. Calcd for CmH6C12Ge: C, 65.49; H, 8.43. Found: C, 65.20; H, 8.62. Preparation of Bis(trimethylsily1)germanes 2b-e,g. A T H F (5 mL) solution of dibromoethane (752 mg, 4 mmol) was added to Mg (243 mg, 10 mmol) with stirring. After the flask was cooled, chlorotrimethylsilane (1.09 g, 10 mmol) was added to the reaction mixture and the mixture was heated to reflux. A T H F (10 mL) solution of dichlorobis(triisopropylpheny1)germane (1.1 g, 2 mmol) was added to the heated mixture. The resulting mixture was allowed to cool and hydrolyzed with dilute hydrochloric acid. Concentration in vacuo yielded bis(trimethy1sily1)germane 2g in 64% yield. For 2g: colorless crystals; mp 199-200 "C; 'H NMR (CDC13) 6 0.10 (d, J = 7 Hz, 6 H), 0.40 (9, 18 H), 1.1-1.5 (m, 30 H), 2.6-3.7 (m, 6 H), 6.75 (8, 1 H), 6.80 (s, 1 €I), 6.95 (s, 1 H), 6.97 (5, 1 H); MS m / e (relative intensity) 611 (4, M+ - Me), 553 (70, M+ - Me3Si), 480 (3, Ar',Ge), 350 (62, Ar'(Me3Si)Ge), 277 (41, Ar'Ge), 261 (100). Anal. Calcd for C3,H,,SiZGe: C, 69.10; H, 10.31. Found: C, 68.87; H, 10.56. Other bis(trimethylsily1)germanes 2b-e were prepared similarly. For 2 b colorless crystals; mp 54-55 "C; 'H NMR (CDCl,) 6 0.21 (5, 18 H), 2.30 (9, 6 H), 7.17 (AB, JAB = 8 Hz, Av- = 11 Hz, 8 H); MS m / e (relative intensity) 402 (0.8, M+), 387 (1, M+ - Me), 256 (9, TolzGe), 241 (37, Tol,Ge-Me), 146 (100, Me3Si-SiMe3). Anal. Calcd for C&-I,,Si,Ge: C, 59.87; H, 8.04. Found: C, 59.84; H, 8.11. For 2c: colorless oil; 'H NMR (CDC13)6 0.23 (s, 18 H), 1.07 (s, 9 H), 2.15 (s, 3 H), 2.40 (s, 6 H), 6.73 (s, 2 H); MS m(e (relative intensity) 339 (100, M+ - tBu), 266 (42, M+ - tBu - Me3&), 193 (29, MesGe). For 2d: colorless crystals; mp 187-190 "C; 'H NMR (CDCl,) 6 0.23 (9, 18 H), 2.26 (5, 1 2 H), 7.0-7.2 (m, 6 H); MS m / e (relative intensity) 430 (2, M+), 415 (8, M+ - Me), 357 (10, M+ - Me3%), 284 (6, Xy,Ge), 179 (13, XyGe), 164 (100, XyGe-Me). Anal. Calcd for Cz2H&,Ge: C, 61.55; H, 8.45. Found: C, 61.13; H, 8.53. For 2e: colorless crystals; mp 145 "C; 'H NMR (CDC13)6 0.17 (9,18 H), 1.00 (t, J = 7 Hz, 12 H), 2.63 (4, J = 7 Hz, 8 H), 6.8-7.3 (m, 6 H); MS m / e (relative intensity) 471 (4, M+ - Me), 413 (23, M+ - Me3Si), 340 (6, ArzGe),207 (63, ArGe), 192 (100, ArGe-Me). Anal. Calcd for CZsH4Si2Ge: C, 64.34; H, 9.14. Found: C, 64.66; H, 9.27. Photolysis of Germylene Precursors at 77 K in Hydrocarbon Matrices. In a typical experiment about 1 mg of the germylene precursor was added to a quartz UV cell. Then, 4 mL of matrix solvent was added. After the sample was degassed by three freeze-pump-thaw cycles, the cell was placed into a quartz windowed Dewar filled with liquid nitrogen. The resulting matrix was irradiated for 5-30 min with a low-pressure mercury lamp. After the electronic absorption spectrum was taken, the matrix was warmed to room temperature and recooled to 77 K. Then the electronic absorption spectrum of the matrix was remeasured. Photolysis of la with 2,3-Dimethyl-l,3-butadiene at Room Temperature. A cyclohexane (4.5 mL) solution of la (160 mg, 0.3 mmol) and 2,3-dimethyl-l,3-butadiene (246 mg, 3.0 mmol) was irradiated with a low-pressure mercury lamp for 5 h a t room temperature. The solvent and compound 3
