Organometallics 1995, 14, 4004-4009
4004
Reductive Dehalogenation of 4,8=Dihalooctakis ( 1,1,2=trimethylpropyl) tetracyclo[3.3.0.02~7.03~6]octasilanes with Sodium: Formation of Octasilacubane Masafumi Unno, Hiroaki Shioyama, Masami Ida, and Hideyuki Matsumoto* Department of Applied Chemistry, Faculty of Engineering, Gunma University, Kiryu, Gunma 376, Japan Received January 23, 1995@
The reductive dehalogenation of 4,8-dichloro-, 4,8-dibromo-, and 4,8-diiodooctakis(l,1,2trimethylpropyl)tetracyclo[3.3.O.Oz~7.O3~6loctasilanes (2-4)with sodium resulted in unprecedented skeletal rearrangement to generate octakis(l,l,2-trimethylpropyl)octasilacubane(l), along with a reduced product, 4,8-~y~~dakis(l,1,2-trimethylpropyl~tracyclo[3.3.O.Oz~7.O3~6loctasilane (6). The structure of 5 was determined by X-ray crystallography.
Introduction
Scheme 1
There is considerable interest in the syntheses and properties of [nlprismanes (where n = 3-5) of group 14 elements, Si, Ge, and Sn.1-3 During our work on the R' d 'R chemistry of octasilacubanes and related compounds, we found that the chlorination of octakis(l,l,2-trimethyl2-4 propy1)octasilacubane( l I 3 with PC15 resulted in skeletal R = CMe2CHMe2 rearrangement with concomitant formation of stereoX = CI, Br, I isomeric 4,8-dichlorooctakis(1,1,2-trimethylpropyl)ttra~y~lo[3.3.0.0~~~.0~~~loctasilane~ (2).*Also we found that the halogenation of octasilacubane 1 with Br2 or with I2 produced stereoisomeric 4,8-dibromo- or 4,8-diiodooctakis(l,l,2-trimethylpropyl)tetracyclo[3.3.O.O2~7.O3~6loctasilanes (3or 4),as described in the present manuscript. We have thus commenced an investigation of the behavior of these dihalooctasilanes toward active Results and Discussion metals in hoping that they can serve as starting materials for a range of new silicon p~lyhedranes.~ In Dechlorination of Dichlorooctasilane 2. When this paper we report our finding that the reductive a solution of stereoisomeric 26 in toluene was heated dehalogenation of 2-4 with sodium metal led to unusual with a large excess sodium7 at 110 "C for 4 h under an skeletal rearrangement, forming octasilacubane 1,along atmosphere of argon, 82% of 2 was dechlorinated and with a reduced product, 4,8-dihydrooctakis(l,1,2-trioctasilacubane 1 was formed in 70% yield (based on the consumption of 2) as red-orange crystals, along with methylpropyl)tetracyclo[3.3.0.02~7.03~610ctasilane (5) reduced product 5 (18%).The identity of 1 was estab(Scheme 1). lished by a comparison of its physical properties (HPLC retention time, mp, and NMR, IR, and W spectra, etc.) @Abstractpublished in Advance ACS Abstracts, July 1, 1995. with those of an authentic samplea3The solid structure (1)(a) Matsumoto, H.; Higuchi, K.; Hoshino, Y.; Koike, H.; Naoi, Y.; Nagai, Y. J. Chem. SOC.,Chem. Commun. 1988,1083.(b) Sekiguchi, of 5 was determined by X-ray crystallography. The A.; Kabuto, C.; Sakurai, H. Angew. Chem., Int. Ed. Engl. 1989,28,55. ORTEP drawing is shown in Figure 1. Crystallographic (c) Nagase, S.Angew. Chem., Int. Ed. Engl. 1989,28,329.(d) Sita, L. R.; Kinoshita, I . Organometallics 1990, 9, 2865. (e) Sita, L. R.; data, positional parameters, and selected bond lengths Kinoshita, I. J . Am. Chem. SOC.1991, 113, 1856. (0 Sekiguchi, A,; and angles are given in Tables 1-3. Compound 5 Yatabe, T.; Kamatani, H.; Kabuto, H.; Sakurai, H. J.Am. Chem. SOC. crystallizes in the P211a space group with four molecules 1992,114,6260. (g) Wiberg, N.; Finger, C. M. M.; Polborn, K. Angew. Chem., Int. Ed. Engl. 1993,32, 1054. per unit cell. As indicated by the X-ray results, the SiH (2)For reviews: (a) Tsumuraya,T.; Batcheller, S. A,; Masamune, hydrogen atoms occupy endo,endo and the bulky 1,1,2S. Angew. Chem., Int. Ed. Engl. 1991, 30, 902. (b) Nagase, S. trimethylpropyl groups exo,exo positions (the positions Polyhedron 1991,10,1299.(c) Sekiguchi, A; Sakurai, H. Adu. Organomet. Chem. 1995,37,1. relative to the bridged Si-Si bonds).
(3)Matsumoto, H.; Higuchi, IC;Kyushin, S.;Goto, M. Angew. Chem., Int. Ed. Engl. 1992,31,1354. (4)Unno, M.; Higuchi, K.; Ida, M.; Shioyama, H.; Kyushin, S.; Matsumoto, H.; Goto, M. Organometallics 1994,13,4633. ( 5 ) To our knowledge, no example has been reported for this type of skeletal rearrangement in the carbon system. For other types of skeletal rearrangements in carbon polyhedral compounds, see: (a) Griffin, G. W.; Marchand, A. P. Chem. Rev. 1989, 89, 997. (b) Marchand, A. P. Chem. Rev. 1989,89,1011.
(6)A mixture of three isomers (endo,exo-2/exo,exo-2/endo,endo-2 = 56/27/17) was used. The ratio of isomers for recovered dichlorides was 53/25/21, and the reactivities of three isomers toward dechlorination were thus thought to be basically similar. (7)The reaction gave the highest yield of octasilacubane 1 when 1 2 equiv of sodium was used. An attempted dechlorination using 5 equiv of sodium resulted in the formation of trace amounts of 1.
0276-733319512314-4004$09.00/0 0 1995 American Chemical Society
Organometallics, Vol. 14, No. 8, 1995 4005
Formation of Octasilacubane
Table 2. Fractional Atomic Coordinates and Equivalent Isotropic Thermal Parameters for 5 atom
c39
Figure 1. ORTEPII drawing of 5. Thermal ellipsoids are drawn at the 30% probability level. Table 1. Summary of Crystal Data, Data Collection, and Refinement Crystal Data formula molecular weight cryst description cryst size, mm cryst system space group a,A b, A C,
A
deg
v, A3
Z
Data Collection diffractometer radiation (A,A) p , cm-l variation of stds, % 28 range, deg range of h range of k range of 1 scan type scan width, deg no. of reflcns measd no. of indepdt reflcns no. of obsd reflcns (IFnIz 3a(Fn)) Refinement
R RW weighting scheme
S e A-3 (Ae)min, e A-3 no. of params
C48Hio6Si8 908.05 colorless prisms 0.2 x 0.2 x 0.1 monoclinic P21lu 22.866(5) 11.726(4) 23.243(4) 114.99(1) 5648(2) 4 Rigaku AFC7S Mo Ka (0.710 69) 2.19 0 3-55 0 to 30 0 to 15 -30 to 30 03-20 0.73 0.30 tan 8 13 953 13 620 2797
+
0.064 0.044 w = l/&F,) 1.54 0.00 0.38 -0.34 513
In dihydrooctasilane 5, the Si-Si bond lengths vary from 2.342(5) to 2.461(5) A and the Si-Si-Si bond angles in the three fused cyclotetrasilane range from 79.9(1) to 94.2(2)". These values are similar to those found in the corresponding isomer of dichlorooctasilane 2, exo,ex0-2 (2.390(3)-2.452(3)A and 81.2(1)-93.9(1)").4 The dihedral angles of the three cyclotetrasilane rings in 5, however, are somewhat greater than the corre-
Si(1) Si(2) Si(3) Si(4) Si(5) Si(6) Si(7) Si(8) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30) C(31) C(32) C(33) C(34) C(35) C(36) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46) C(47) C(48) H(Si4) H(Si8)
Y
X
0.3982(2) 0.4208(2) 0.3537(2) 0.2982(2) 0.4775(2) 0.4550(2) 0.5195(2) 0.5773(2) 0.4013(6) 0.3659(6) 0.2939(6) 0.4716(6) 0.3741(6) 0.3758(5) 0.4091(5) 0.4217(6) 0.4257(7) 0.4590(6) 0.3414(5) 0.3750(7) 0.3026(6) 0.2348(7) 0.1920(7) 0.2887(6) 0.3413(6) 0.2380(7) 0.2327(6) 0.1665(6) 0.1108(6) 0.2369(7) 0.2453(7) 0.1528(7) 0.4904(6) 0.4264(6) 0.4321(7) 0.5216(6) 0.5384(6) 0.3929(6) 0.4838(6) 0.4537(6) 0.3820(6) 0.4706(6) 0.5574(6) 0.4854(7) 0.5599(6) 0.6054(6) 0.6298(6) 0.5942(6) 0.5041(6) 0.6634(5) 0.6411(6) 0.6590(6) 0.6890(6) 0.6174(6) 0.7012(5) 0.7045(7) 0.258(5) 0.616(4)
+
Beq?A2
z
0.5052(3) 0.3074(3) 0.2615(3) 0.4319(3) 0.5014(3) 0.3045(3) 0.2612(3) 0.4303(3) 0.643(1) 0.633(1) 0.617(1) 0.6662(10) 0.741(1) 0.737(1) 0.2794(10) 0.159(1) 0.139(1) 0.356(1) 0.318(1) 0.073(1) 0.126(1) 0.132(1) 0.031(2) 0.127(1) 0.017(1) 0.128(1) 0.505(1) 0.479(1) 0.499(1) 0.452(1) 0.633(1) 0.547(1) 0.6318(10) 0.681(1) 0.794(1) 0.727(1) 0.598(1) 0.599(1) 0.250(1) 0.319(1) 0.308(1) 0.123(1) 0.266(1) 0.294(1) 0.116(1) 0.071(1) -0.052(1) 0.128(1) 0.028(1) 0.145(1) 0.489(1) 0.613(1) 0.629(1) 0.475(1) 0.413(1) 0.665(1) 0.406(9) 0.409(7)
0.7741(1) 0.8127(1) 0.7019(2) 0.6981(2) 0.7326(2) 0.6960(2) 0.8049(2) 0.8139(2) 0.8233(5) 0.8680(6) 0.8314(7) 0.8639(5) 0.7764(5) 0.9108(5) 0.8904(5) 0.9140(6) 0.9819(6) 0.9402(5) 0.8811(5) 0.8718(6) 0.6615(5) 0.6631(7) 0.6279(8) 0.5924(6) 0.6885(6) 0.7264(8) 0.6238(6) 0.6210(6) 0.5586(7) 0.5664(6) 0.6233(7) 0.6694(7) 0.6862(5) 0.6349(6) 0.6067(7) 0.7342(6) 0.6585(6) 0.5812(6) 0.6322(5) 0.5699(5) 0.5348(5) 0.6215(6) 0.6615(5) 0.5250(6) 0.8403(6) 0.8147(6) 0.8389(7) 0.9142(6) 0.8231(6) 0.8271(6) 0.8942(6) 0.8899(6) 0.8424(7) 0.9458(6) 0.9146(6) 0.9532(7) 0.726(5) 0.782(4)
+
2.53(9) 2.36(9) 2.68(9) 3.22(10) 2.84(9) 2.86(9) 2.65(9) 3.12(10) 3.1(3) 3.6(3) 5.6(4) 4.0(4) 4.4(4) 4.5(4) 3.1(3) 3.8(4) 6.9(5) 4.3(4) 4.1(4) 5.5(4) 3.4(3) 5.8(5) 12.7(8) 5.7(5) 6.1(4) 7.6(6) 3.9(4) 5.8(4) 8.6(5) 7.6(5) 6.6(5) 8.3(6) 3.1(3) 4.0(4) 7.0(5) 4.5(4) 4.5(4) 6.0(4) 3.6(3) 4.0(4) 5.1(4) 5.1(4) 4.6(4) 7.8(5) 3.8(4) 4.1(4) 7.1(5) 5.0(4) 5.1(4) 5.0(4) 3.9(4) 4.2(4) 6.4(5) 5.1(4) 4.7(4) 7.9(5) 7.0(7) 3.0(10)
+
a Be, = ~/3n~(U11(aa*)2 U ~ z ( b b * ) ~ U ~ ~ ( C C * )2' U i m ~ * b b * cos y +2U13uu*cc* cos p 2U23bb*cc* cos a).
+
sponding angles in 2 (31.7-41.5"), 44.7" between the Si(l)-Si(3)-Si(2) and Si(l)-Si(3)-Si(4) planes, 45.1" between the Si(2)-Si(4)-Si(l) and Si(2)-Si(4)-Si(3) planes, 33.0" between the Si(2)-Si(6)-Si(3) and Si(2)Si(6)-Si(7) planes, 37.0" between the Si(3)-Si(7)-Si(2) and Si(3)-Si(7)-Si(6) planes, 41.6" between the Si(5)Si(7)-Si(6) and Si(5)-Si(7)-Si(8) planes, and 43.0" between the Si(S)-Si(S)-Si(ti) and Si(6)-Si(8)-Si(7) planes. The formation of octasilacubane 1 is quite remarkable in light of previous work reported by Masamune and co-workers, who found that treatment of 4,8-dichlo-
4006 Organometallics, Vol. 14, No. 8, 1995
Unno et al.
Table 3. Selected Bond Lengths (A)and Angles (deg) for 5 Si(l)-Si(2) Si(l)-Si(5) Si(2)-Si(3) Si(2)-C(7) Si(3)-Si(6) Si(4)-C(19) Si(5)-Si(8) Si(6)-Si(7) Si(7)-Si(8) Si(8)-C(43) Si(8)-H(Si8)
Bond Lengths 2.461(5) Si(l)-Si(4) 2.388(4) Si(l)-C(l) 2.437(5) Si(2)-Si(7) Si(3)-Si(4) 1.96(1) 2.431(5) Si(3)-C(13) 1.94(1) Si(5)-Si(6) 2.414(5) Si(5)-C(25) 2.385(5) Si(6)-C(31) 2.342(5) Si(7)-C(37) 1.95(1) Si(4)-H(Si4) 1.39(8)
2.382(5) 1.96(1) 2.403(5) 2.348(5) 1.96(1) 2.440(5) 1.96(1) 1.97(1) 1.94(1) 1.37(9)
Scheme 2 R
m
.. R'
1
k R = CMe2CHMe2
Bond Angles Si(2)-Si(l)-Si(4) si(2)-si(l)-C(l) Si(4)-Si(l)-C(l) Si(l)-Si(2)-Si(3) Si(l)-Si(2)-C(7) Si(3)-Si(2)-C(7) Si(2)-Si(3)-Si(4) si(2)-si(3)-C(13) Si(4)-Si(3)-C(13) Si(l)-Si(4)-Si(3) si(3)-si(4)-C(19) Si(l)-Si(5)-Si(8) Si(6)-Si(5)-Si(8) Si(8)-Si(5)-C(25) Si(3)-Si(6)-Si(7) Si(5)-Si(6)-Si(7) Si(7)-Si(6)-C(31) Si(2)-Si(7)-Si(8) Si(6)-Si(7)-Si(8) Si(8)-Si(7)-C(37) Si(5)-Si(8)-C(43)
85.3(2) 127.7(4) 121.1(4) 83.2(2) 113.8(4) 131.8(4) 86.6(2) 131.9(4) 117.8(4) 86.8(2) 127.7(5) 108.6(2) 86.4(2) 112.8(4) 94.2(2) 83.5(2) 118.4(4) 108.4(2) 89.3(2) 123.6(4) 134.9(4)
Si(2)-Si(l)-Si(5) Si(4)-Si(l)-Si(5) Si(5)-Si(l)-C(l) Si(l)-Si(2)-Si(7) Si(3)-Si(2)-Si(7) Si(7)-Si(2)-C(7) Si(2)-Si(3)-Si(6) Si(4)-Si(3)-Si(6) Si(6)-Si(3)-C(13) Si(l)-Si(4)-C(l9) Si(l)-Si(5)-Si(6) Si(l)-Si(5)-C(25) Si(6)-Si(5)-C(25) Si(3)-Si(6)-Si(5) Si(3)-Si(6)-C(31) Si(5)-Si(6)-C(31) Si(2)-Si(7)-Si(6) Si(2)-Si(7)-C(37) Si(6)-Si(7)-C(37) Si(5)-Si(8)-Si(7) Si(7)-Si(8)-C(43)
93.0(2) 110.4(2) 113.9(4) 104.1(2) 93.6(2) 122.0(4) 79.9(1) 109.5(2) 122.0(4) 129.6(5) 94.2(2) 121.5(4) 127.2(4) 104.0(2) 127.3(4) 118.9(4) 81.5(2) 117.2(4) 127.3(4) 84.9(2) 123.4(4)
roocta-tert-butyltetracyclo[3.3.O.O2~7.O3~6loctasilane with lithium naphthalenide in toluene had provided only a reduced product, 4,8-dihydroocta-tert-butyltetracyclo[3.3.0.02~7.03~610~tasilane, after protolytic workup.* However, the choice of reaction conditions is crucial in our case: (1) When other active metals such as lithium powder were substituted for sodium, only starting materials were recovered and no octasilacubane was obtained. (2)When the reaction time was extended over several hours to attain the complete conversion of dichlorooctasilane 2, the yield of 1 decreased and ring opening of 1 occurred during the reaction. Synthesis and Dehalogenation of Dibromooctasilane 3 and Diiodooctasilane 4. We next examined the reductive dehalogention of 3 and 4 with sodium. In the present work, these dihalooctasilanes were obtained by the reactions of octasilacubane 1 with Bra and with I2 (Scheme 2). We found that in each case, the halogenation proceeded in a fashion similar to that observed for the chlorination using PC15,4resulting in the exclusive formation of the rearranged products, 3 or 4.9 Thus, treatment of 1 with a slight excess of Br2 in benzene at 5 "C to room temperature afforded a 75% yield of 3. HPLC analysis indicates that 3 exists as a mixture of the three possible stereoisomers, 3a-c. (8) Kabe, Y.; Kuroda, M.; Honda, Y.; Yamashita, 0.;Kawase, T.; Masamune, S.Angew. Chem., Int. Ed. Engl. 1988,27,1725. However, no crystal structure of the 4,8-dihydrooctasilane was given. (9) An X-ray cryallographic determination was undertaken for isomer 3b,and the preliminary results indicate the exo,exo structure. Crystal data for the compound: C48H104Br2Si monoclinic, C2/c; a = 27.907(2) 8, b = 11.783(2)A, c = 22.302(1) /3 = 127.431(2)",V = 5823.6(10)A3, 2 = 4, R = 0.068, R, = 0.046 (for the ORTEP drawing of the compound, see the supporting information). We have, however, been unable to obtain crystals of compounds 3a,c and 4a-c suitable for X-ray crystallography.
1:
endo,ex0
[XI = Br, (3) 12
(4)
32% 26%
R' k exo,exo
31% 39%
endo,endo 9%
13%
These isomers could easily be separated by reversephase recycle-type HPLC (Scheme 2); yields were 32% (3a), 31% (3b),and 9% (3c). The diiodination of 1 was similarly accomplished as was the dibromination, resulting in the isolation of the three isomers in 26% (4a), 39% (4b),and 13% (4c) yields. The structures of 3a-c as endo,exo-, exo,exo-, and endo,endo-4,8-dibromooctakis( 1,1,24rimethylpropyl)tetracyclo[3.3.0.02J.03~6]octasilanes were confirmed by IR, mass, and NMR (lH, 29Si{1H},and 13C{lH})spectroscopy (Experimental Section); the corresponding conformers of dichlorooctasilane Z4 can serve as precedents in determining the stereochemistry of isomers 3a-c. Compound 3a exhibits eight signals in the 29Si{lH} NMR spectrum and 48 signals in the 13C NMR spectrum, indicating that all eight silicon atoms and 1,1,24rimethylpropyl groups are nonequivalent. The observed NMR patterns closely resemble those of the endo,exo isomer of 2,4 allowing the assignment of 3a to the endo,exo structure. Both 3b and 3c exhibit four signals in the 29Si{1H}NMR spectra and 24 signals in the 13C NMR specta, indicating the presence of C2 symmetry in these molecules. These NMR results are consistent with the exo,exo and endo,endo structures, and the discrimination of the two structures was made from 29Si NMR spectra of 3b and 3c. In 3b the resonance of the 29Si(SiBr) nuclei is observed a t 46.59 ppm, and in 3c the corresponding resonance is at 54.60 ppm. We previously showed that the 29Siresonance of the Si(SiC1) atoms in the exo,exo isomer of 2 fell at higher field (51.49 ppm) than that of the exo,exo isomer (59.33 ppmL4 Since the 29Si(SiBr) resonance in 3b is shifted upfield relative to the corresponding resonance in 3c, 3b is assigned as the exo,exo i ~ o m e r ,and ~ therefore 3c is the endo,endo isomer. On a similar NMR basis, we assigned 4a-c to the endo,exo, exo,exo, and endo,endo isomers. Then, we examined the dehalogenation of bromide 3 and iodide 4 with sodium and observed the formation of 1 and 5. Thus the treatment of 3 with a large excess of sodium at 120 "C for 4 h resulted in the formation of 1 and 5 in 68 and 29% yields, respectively. When 4 was treated with a large excess of sodium at 120" C for 4 h, 1 and 5 formed in 45 and 22% yields, respectively. In both cases, the starting materials were completely consumed.
Organometallics, Vol. 14, No. 8, 1995 4007
Formation of Octasilacubane
Scheme 3
2-4
H.1
- NaX
7
Possible Reaction Pathway for Dehalogenation. The pathway leading to octasilacubane 1 is not clearly understood, but in Scheme 3 a possible reaction pathway is proposed to account for the formation of 1. The initial process produces an anion species 6, in a fashion similar to the reductive coupling of chloropolysilanes with alkali metals.1° Then a rapid skeletal rearrangement follows wherein the central Si-Si bond is cleaved and the new Si-Si bonds are formed. Such a skeletal rearrangement is very unusual and has, t o our knowledge, no precedentall Although, this rearrangement may be associated with a high activation energy, the ring closure leading t o 1 can be accomplished by employing the forced reaction conditions, as shown in the present work. In addition, releasing steric congestion in 2 due to the bulky 1,1,2-trimethylpropyl groups may provide a part of the driving force for the skeletal rearrangement. The generation of dihydrooctasilane 5 is also explained in the same scheme. The reason for the fact that only endo,endo isomer of 5 was obtained could also be demonstrated with the intermediate 7. The steric repulsion of large 1,1,2-trimethylpropyl groups made endo conformation preferable. Summary The reaction of 4,8-dihalooctakis(l,1,2-trimethylpropyl2 tetracyclo[3.3.0.02~7.03~610ctasilane with sodium resulted the unprecedented rearrangement to give octasilacubane in good yields along with a reduced product, 4,8dihydrooctakid 1,1,2-trimethylpropyl)tetracyclo[3.3.0.02~7.03~610~tasilane. The reductive dechlorination of 2 with sodium might offer an attractive route to 1, otherwise available only in low yields from the reductive with coupling of ~1,1,2-trimethylpropyl)trichlorosilane sodium.13
Experimental Section NMR spectra were recorded on a JEOL Model a-500 (lH, 500.0 MHz; 13C, 125.7 MHz; 29Si,99.3 MHz). Mass spectrom-
__
(10)Ruehl, K. E.: Davis, M. E.; Matyjaszewski, K. Organometallics 1992, 11, 788. (11)In 1989, Weidenbruch et al. reportedI2 the synthesis of 4,8-
dibromoocta-tert-but~ltetrac~clo~3.3.O.O~~~.O~~~loctasilane. They described in their manuscript &at the formation of an octagermacibane from it is not possible, since, in addition to the reductive elimination of the two bromine atoms, the cleavage and re-formation of a Ge-Ge bond is required. (12) Weidenbruch, M.; Grimm, F.-T.; Pohl, S; Saak, W. Angew. Chem., Int. Ed. Engl. 1989, 28, 198. (13) We are now investigating the possibilitiy of one-pot synthesis of the dichlorides 2 from 1,1,2-trimethylpropyltrichlorosilane.
6
1
5
etry was performed by a JEOL JMS-D300. Infrared spectra were measured with a JASCO A-102 spectrometer. Analytical HPLC was done by JASCO 875W/880PU and W-970/88OPU instruments with a Chemco 4.6 mm x 250 mm 5-ODs-H column. Preparative (recycle-type) HPLC was carried out using JAI LC-908 and LC-09 instruments with Chemco 20 mm x 250 mm 7-ODs-H columns. All reactions were carried out under an atmosphere of argon or nitrogen. All solvents were dried, distilled, and degassed, and all glassware was dried at 80 "C for several hours prior to use. Synthesis of Dibromooctasilane 3. To a solution of octasilacubane 1 (24 mg, 0.025 mmol) in 6 mL of benzene was added 0.4 mL of 0.1 M benzene solution of Br2 (0.04 mmol) around 5 "C, and the mixture was stirred at room temperature. After 2 h, an aliquot was taken from the mixture; HPLC showed the bromination to be complete. The reaction mixture was passed through a short silica gel column, and the solvent was removed by evaporation. A pale-yellow solid was obtained as a isomeric mixture of 3. Each isomer of 3 was isolated by recycle-type preparative HPLC (ODS, MeOWTHF = 614 elution). Isomers 3a-c were identified as endo,exo, exo,exo, and endo,endo conformers, respectively. The yields of 3a-3c were 8.6 mg (32%),8.4 mg (31%),and 2.3 mg (9%),respectively. 3a: colorless prisms, mp (sealed) 187 "C dec; 'H NMR (CDC13)6 2.52 (sept, 2H, J = 6.7 Hz), 2.40 (sept, l H , J = 6.7 Hz), 2.33 (sept, 2H, J = 6.7 Hz), 2.29 (sept, 3H, J = 6.7 Hz), 1.62 (s, 3H), 1.49 (s, 3H), 1.47 (s, 3H), 1.46 (s, 3H), 1.44 (s, 3H), 1.41 (s, 3H), 1.40 (9, 3H), 1.39 (s, 3H), 1.35 (s, 3H), 1.33 (5, 3H), 1.324 (s, 3H), 1.317 (s, 6H), 1.29 (s, 3H), 1.27 (s, 3H), 1.22 (s, 3H), 1.12 (d, 3H, J = 5.8 Hz), 1.11(d, 3H, J = 6.8 Hz), 1.10 (d, 3H, J = 6.7 Hz), 1.06 (d, 3H, J = 6.8 Hz), 1.03 (d, 3H, J = 6.7 Hz), 0.99 (d, 3H, J = 6.4 Hz), 0.98 (d, 3H, J = 6.4 Hz), 0.94 (d, 3H, J = 7.3 Hz), 0.92 (d, 3H, J = 7.3 Hz), 0.90 (overlap, d, 6H, J = 6.7 Hz), 0.89 (overlap, d, 6H, J = 6.4 Hz), 0.85 (overlap, d, 9H, J = 6.7 Hz); 13C{lH} NMR (CDC13) b 38.07, 37.38, 37.03, 36.39, 36.33, 36.19, 36.00, 35.66, 35.45, 35.36, 35.36, 35.01, 34.96, 34.43, 34.43, 34.19, 33.45, 30.43, 30.07, 29.68, 28.26, 27.93, 27.93, 27.22, 26.63, 26.55, 26.47, 25.43, 25.29, 23.96, 23.74, 23.45, 22.50, 22.24, 22.15, 21.91, 21.91, 21.12, 20.47, 20.40, 20.01, 19.79, 19.63, 18.77, 18.22, 18.03, 17.22, 16.08; 29Si{1H}NMR (CDC13): 6 51.39, 46.80, 19.94, 13.44, -0.76, -3.57, -18.59, -22.67; IR (KBr) 2960, 2860, 1460, 1370, 1120, 1080 cm-l; MS (30 eV) m l z 980 (1,M+ CsHio), 895 (51, 811 (5), 727 (61, 643 (111,559 (131, 475 (12), 391 (3),69 (100);HRMS calcd for C48H104Si~Br2 m / z 1062.4664, found: m l z 1062.4640. 3b: colorless prisms, mp (sealed) 191 "C dec; 'H NMR (CDC13) 6 2.41 (sept, 2H, J = 6.7 Hz), 2.37 (sept, 4H, J = 6.7 Hz), 2.33 (sept, 2H, J = 6.7 Hz), 1.47 (s, 6H), 1.43 (overlap, s, 12H), 1.39 (overlap, s, 12H), 1.36 (s, 6H), 1.30 (s, 6H), 1.21 (s, 6H),1.09(d,6H,J=6.7Hz),l.OO(d,6H,J=6.7Hz),0.98(d, 6H, J = 6.7 Hz), 0.97 (overlap, d, 12H, J = 6.8 Hz), 0.93 (d, 6H, J = 6.8 Hz), 0.87 (d, 6H, J = 7.1 Hz), 0.85 (d, 6H, J = 6.7 Hz); 13C{1H}NMR (CDCl3)6 37.28,36.61, 36.54,35.62, 34.57, 34.57, 34.28, 33.67, 28.58, 27.80, 27.41, 26.79, 26.63, 26.49,
4008
Unno et al.
Organometallics, Vol. 14, No. 8,1995
4c: pale yellow prisms, mp (sealed) 170 "C dec; 'H NMR (CDC13)6 2.57 (sept, 2H, J = 6.7 Hz), 2.48 (sept, 2H, J = 7.0 Hz), 2.38 (sept, 2H, J = 6.7 Hz), 2.33 (sept, 2H, J = 7.0 Hz), 1.57 (s, 6H), 1.55 (s, 6H), 1.52 (9, 6H), 1.41 (s, 6H), 1.39 (s, 6H) 1 3 8 (s, 6H), 1.33 (s, 6H), 1.28 (s, 6H), 1.18 (d, 6H, J = 6.7 Hz), 1.15 (d, 6H, J = 7.0 Hz), 1.05 (d, 6H, J = 6.8 Hz), 1.00 (d, 6H, J = 6.8 Hz), 0.91 (d, 6H, J = 6.7 Hz), 0.893 (d, 6H, J = 6.4 Hz), 0.891 (d, 6H, J = 8.0 Hz), 0.84 (d, 6H, J = 6.7 Hz); l3C{lH) NMR (CDCl3) 6 47.37, 47.11, 45.73, 45.20, 45.04, 44.48, 43.54, 42.51, 40.24, 39.46, 38.32, 35.93, 35.83, 35.33, 33.72, 33.31, 33.05, 32.10, 31.32, 30.72, 28.71, 28.48, 1.31(s,6H),1.28(s,6H),1.13(d,6H,~=6.7Hz),l.ll(d,6H, 27,62,26.16; 29Si{lH} NMR (CDCl3)6 35.00, 10.13,0.48,-2.36; J = 7.0 Hz), 1.04 (d, 6H, J = 6.7 Hz), 1.00 (d, 6H, J = 7.0 Hz), IR (KBr) 2960,2860,1460,1370,1120,1080cm-l; MS (30 eV) 0.89(d,6H,J=6.7Hz),0.88(d,6H,J=6.7Hz),0.87(d,6H, m l z 1074 (1, M+ - C6H13), 989 (21, 905 (31, 821 (41, 737 (71, J = 6.4 Hz), 0.85 (d, 6H, J = 6.7 Hz); 13C{1H}NMR (CDC13) 6 653 (9), 569 (lo), 484 (2),69(100);HRMS calcd for C48H104Si812 37.22, 37.00, 36.10, 36.04, 35.44, 34.78, 34.54, 34.37, 30.28, m l z 1158.4382, found m l z 1158.4320. 29.91, 28.54, 26.20, 26.11, 25.92, 24.29, 23.39, 23.06, 22.16, Reductive Dehalogenation of Dichlorooctasilane 2 21.81, 21.04, 19.15, 19.15, 17.66, 16.62; 29Si{1H}NMR (CDC13) with Sodium. A suspension of sodium sand (8 mg, 0.35 6 54.60, 12.50, -1.52, -12.86; IR(KF3r) 2960,2860,1460, 1370, mmol) in toluene (1mL) was added to a solution of 2 (30 mg, 1120, 1080 cm-'; MS (30 eV) m l z 980 (1,M+ - C6HlO), 895 0.030 mmol, a mixture of the three isomers (endo,exo-21exo,(21, 811 (31, 727 (21, 643 (51, 559 (71,475 (61, 391 (6), 69 (100); exo-Wendo,end0-2= 56127117)) in toluene (1 mL). The resultHRMS calcd for C42Hg1Si8Br2 (M+ - CMe2CHMe2) m l z ing mixture was stirred at 120 "C for 1.5 h. The color of the 977.3642, found m l z 977.3610. mixture changed from pale yellow to pink. The reaction Synthesis of Diiodooctasilane 4. By a reaction analomixture was passed through a short silica gel column, and the gous to that described for dibromooctasilane 3, but using 22 solvent was removed by evaporation. The residue was recrysmg (0.024 mmol) of octasilacubane 1 and 0.6 mL of a solution tallized from hexane to give 16 mg of red crystals, whose of 0.05 M iodine in benzene, a pale yellow solid was obtained physical properties (HPLC retention time, mp, and NMR, IR, after a 2.5 h reaction (at room temperature) and subsequent and W spectra, etc.) were identical with those of an authentic workup. Each isomer of 4 was isolated by recycle-type sample of octasilacubane L3 The yield was 70% based on the preparative HPLC (ODS, MeOWTHF = 614 elution). Isomers dichlorooctasilane 2 consumed. Recycle-type preparative HPLC 4a-c were identified as endo,exo, exo,exo, and endo,endo (ODS, MeOWTHF = 614 elution) of the supernatant liquid conformers, respectively. The yields of 4a-c were 7.1 mg from the above recrystallization allowed isolation of reduced (267~1,10.6 mg (39%),and 3.6 mg (13%),respectively. product 5 (4 mg, 18%)and unreacted 3 (endo,exo-2, 3 mg; 4a: pale yellow prisms, mp (sealed) 200 "C dec; 'H NMR exo,exo-2, 1 mg; endo,endo-2, 1 mg; total 18%). (CDC13)6 2.67 (sept, l H , J = 7.0 Hz), 2.54 (sept, l H , J = 6.7 5: colorless prisms, mp (sealed) 226-228 "C dec; 'H NMR Hz), 2.49 (sept, l H , J = 6.7 Hz), 2.40 (sept, l H , J = 6.7 Hz), (CsD6)6 4.82 (s, 2H), 2.48 (sept, J = 6.7 Hz, 2H), 2.45 (sept, J 2.36-2.30 (m, 4H, J = 6.7 Hz), 1.64 (s,3H), 1.60 (s,3H), 1.58 = 6.7 Hz, 2H), 2.30 (sept, J = 6.7 Hz, 4H), 1.63 (s, 6H), 1.63 (s, 3H), 1.53 (s, 3H), 1.52 (s, 3H), 1.51 (s,3H), 1.46 (s, 3H), (s, 6H), 1.49 (s, 6H), 1.43 (s, 6H), 1.43 (s, 6H), 1.42 (s, 6H), 1.41 (s, 3H), 1.40 (s, 3H), 1.372 (s, 3H), 1.366 (s, 3H), 1.351 (s, 1.39 (s, 6H), 1.37 (s, 6H), 1.38 (d, J = 6.7 Hz, 6H), 1.28 (d, J 3H), 1.351 (s, 3H), 1.32 (s, 3H), 1.27 (s,3H), 1.25 (s,3H), 1.18 = 6.7 Hz, 6H), 1.15 (d, J = 6.7 Hz, 6H), 1.12 (d, J = 6.7 Hz, (d, 3 H , J = 6.7 Hz), 1.17 (d, 3 H , J = 6.7 Hz), 1.14(d, 3 H , J = 6H), 1.09 ( d , J = 6.7 Hz, 6H), 1.06 ( d , J = 6.7 Hz, 6H), 1.02 (d, 6.7 Hz), 1.12 (d, 3H, J = 7.0 Hz), 1.06 (d, 3H, J = 6.7 Hz), J = 6.7 Hz, 6H), 0.99 (d, J = 6.7 Hz, 6H); l3C(lH} NMR (CsD6) 1.02 (d, 3H, J = 7.1 Hz), 1.00 (d, 3H, J = 6.7 Hz), 0.93-0.90 6 36.77, 36.56, 35.89, 35.81, 35.28, 34.36, 33.15, 30.77, 29.78, (m, 15H, J = 6.7 Hz), 0.89 (d, 3H, J = 7.0 Hz), 0.85 (d, 3H, J 28.49, 7.29, 26.55, 26.23, 25.38, 24.46, 24.08, 22.33, 21.43, = 6.4 Hz), 0.84 (d, 3H, J = 6.5 Hz), 0.82 (d, 3H, J = 6.4 Hz); 21.43, 9.33, 19.20, 18.76, 18.51, 18.15; 29Si{1H}NMR (C&) 13C{lH}NMR (CDC13)6 38.48,38.27,37.37,36.92,36.69,36.23, 6 22.83, -7.20, -21.43, -32.16; IR ( m r ) 2950, 2850, 2080, 35.99, 35.79, 35.55, 35.55, 34.82, 34.50, 34.05, 32.88, 32.29, 1460, 1370, 1260, 1080, 800 cm-l; MS (30 eV) m l z 821 (14, 30.98, 30.88, 30.56, 30.19, 29.17, 28.77, 28.05, 27.98, 27.59, M+ - C6H13), 737 (ll),653 (22), 569 (141, 485 (151, 401 (181, 317 (51), 233 (231, 69 (100); HRMS calcd for C48H106Si8 m l z 27.52, 26.83, 26.10, 25.20, 24.58, 24.11, 24.06, 23.98, 23.56, 23.38, 23.06, 22.78, 22.78, 21.35, 20.93, 20.71, 20.11, 19.80, 906.6449, found m l z 906.6416.14 19.03, 18.72, 18.27, 18.27, 16.89, 16.06; 29Si{'H}NMR (CDC13) Reductive Dehalogenation of Dibromooctasilane 3 6 31.00, 26.45, 18.57, 9.63, 1.44, 1.23, -5.48, -17.49; IR with Sodium. The same procedure as above with 22 mg (KBr): 2960, 2860, 1460, 1370, 1120, 1080 cm-l; MS (30 eV) (0.021 mmol) of 3, 14 mg (0.61 mmol) of sodium sand, and 1.5 m l z 1074 (1,M+ - C6H13), 989 (11,905 (11, 821 (21, 737 (41, mL of toluene gave 13 mg (68% yield) of 1 and 5.6 mg (29% 653 (5), 569 (5), 69 (base); HRMS calcd for C48H104Si812 m l z yield) of 5 after a 4 h reaction and subsequent workup 1158.4382, found m l z 1158.4447. including recycle-type preparative HPLC (ODS, MeOHPTHF = 614 elution). 4b: colorless prisms, mp (sealed) 207 "C dec; 'H NMR Reductive Dehalogenation of Diiodoctasilane 4 with (CDC13)6 2.51 (sept, 2H, J = 6.7 Hz), 2.43 (sept, 2H, J = 6.7 Sodium. The same procedure as above with 45 mg (0.039 Hz), 2.41 (sept, 2H, J = 7.1 Hz), 2.33 (sept, 2H, J = 6.7 Hz), mmol) of 4, 15 mg (0.65 mmol) of sodium sand, and 1.5 mL of 1.57 (s, 6H), 1.49 (s, 6H), 1.46 (s, 6H), 1.43 (overlap, s, 12H), toluene gave 16 mg (45% yield) of 1 and 8 mg (22% yield) of 5 1.40 (s, 6H), 1.37 (s, 6H), 1.24 (s, 6H), 1.14 (d, 6H, J = 6.7 after a 4 h reaction and subsequent workup including recycleHz),1.02(d,6H,J=6.7Hz),1.01~d,6H,J=7.3Hz~,0.98~d, 6H,J=6.7Hz),0.95(d,6H,J=6.7Hz),0.93(d,6H,J=6.8 type preparative HPLC (ODS, M e O m H F = 614 elution). Hz), 0.88 (d, 6H, J = 6.7 Hz), 0.84 (d, 6H, J = 6.8 Hz); X-ray CrystallographicAnalysis of Reduced Product 5. Colorless crystals of endo,endo-4,8-dihydrooctakis(l,l,2{lH} NMR (CDC13) 6 37.47, 37.33, 37.29, 25.49, 34.87, 34.80, trimethylpropyl)tetracyclo[3.3.O.Oz~7.03~6loctasilane were ob34.63, 32.30, 29.27, 28.34, 27.80, 27.63, 27.56, 27.24, 25.80, tained from benzene by slow evaporation. A crystal specimen 24.21, 22.10, 21.57, 21.50, 21.14, 20.70, 19.72, 19.27, 18.33; of dimensions 0.2 x 0.2 x 0.1 mm was sealed in a glass 29Si{1H}NMR (CDC13)6 24.81, 16.32, -1.65, -18.85; IR (KBr) capillary and used for data collection on a Rigaku AJX7S 2960,2860,1460,1370,1120,1080 cm-I; MS (30 eV) m l z 1074 (1,M+ - CsH13), 989 (41,905 (41,821 (41, 737 (81,653 (lo), 569 (91, 485 (21, 69 (100); HRMS calcd for C48H104Si812 m l z (14)SAPIQ1: Fan Hai-Fu. Structure Analysis Programs with Intelligent Control, Rigaku Corp., Tokyo, Japan, 1991. 1158.4382, found m l z 1158.4428.
26.20, 22.28, 22.02, 21.16, 20.75, 20.61, 20.55, 20.15, 19.07, 18.05; 29Si{'H} NMR (CDC13) 6 46.59, 18.62, -4.29, -25.56; IR (KBr) 2960,2860,1460,1370,1120,1080cm-'; MS (30 eV) m l z 980 (1,M+ - C6H10), 895 (31,811(31,727 (5), 643 (71,559 (7), 475 (a), 391 (2), 69 (100); HRMS calcd for C42HglSieBrz (M+ - CMeZCHMez) m l z 977.3642, found m l z 977.3655. 3c: pale yellow prisms, mp (sealed) 190 "C dec; 'H NMR (CDC13) 6 2.61 (sept, 2H, J = 7.0 Hz), 2.47 (sept, 2H, J = 7.0 Hz), 2.30 (sept, 2H, J = 7.0 Hz), 2.29 (sept, 2H, J = 7.0 Hz), 1.51 (s, 6H), 1.48 (s, 6H), 1.43 (s, 6H), 1.32 (overlap, s, 18H),
?
~~
Formation of Octasilacubane diffractometer using graphite-monochromated Mo Ka radiation. Cell parameters were refined by the least-squares method using 20 reflections (22.52 < 28 < 27.59"). The space group P21Ia was uniquely determined from systematic absences (h01,h 2n; 0120, k ;t 272). Intensity data were collected in the range of 3 < 28 < 55" by the 0-28 scan technique at a temperature of 20 f 1"C. Of the 13 953 reflections which were collected, I3 620 were unique (Rint= 0.101). The intensities of three representative reflection were measured after every 150 reflections. No decay correction was applied. The linear absorption coefficient, ,u, for Mo Ka radiation is 2.2 cm-l. Azimuthal scans of several reflections indicated no need for an absorption correction. The data were collected for Lorentz and polarization effects. The structure was solved by SAP191'4 and expanded using Fourier techniques. l5 The non-hydrogen atoms were refined anisotropically. Two of hydrogen atoms (Si-H) were refined isotropically, and the rest were included in fixed positions. The final cycle of full-matrix least squares refinement was based on 2797 observed reflections (iF,I 2 3a(F0))and 513 variable parameters and converged (largest
*
(15)DIRDIF92: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-Granda, S.; Gould, R. 0.; Smits, J. M. M.; Smykalla, C . The DIRDIF program system, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands, 1992.
Organometallics, Vol. 14,No. 8, 1995 4009 parameter was 0.01 times its esd) with unweighted and weighted factors of R = 6.4% and R, = 4.4%. All calculations were carried out on a SiliconGraphics INDY computer. Details of crystal data, data collection and refinement are listed in Table 1.
Acknowledgment. This work was supported by a Grant-in-aid for Scientific Research (No. 05740405) and that on Priority Area of Reactive Organometallics (No. 05236102) from the Ministry of Education, Science, and Culture of Japan. We wish to thank Shin-Etsu Chemical Co. Ltd., Toshiba Silicon Co. Ltd., and Toagosei Co. Ltd. for financial support. Supporting Information Available: Tables of anisotropic thermal parameters, atomic coordinates and isotropic thermal parameters involving H atoms, and bond lengths and angles for 5 and figures showing views of molecular packing and packing diagrams for 5 and an ORTEP drawing for 3b (28 pages). Ordering information is given on any current masthead page. OM950056F
