Organometallics 1995,14, 3855-3868
3855
Synthesis, Characterization, and Reactivities of Diruthenium Complexes Containing a psilane Ligand and Structural Studies of the psilane Complex [Cp’Ru(C0)]2(1U-92:92-H2SitB~2) Toshiro Takao, Shigeru Yoshida, and Hiroharu Suzuki” Department of Chemical Engineering, Faculty of Engineering, Tokyo Institute of Technology, 0-okayama, Meguro-ku, Tokyo 152, Japan
Masako Tanaka Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-Ku, Yokohama 226, Japan Received November 14, 1994@ The diruthenium complex [Cp’RuOL-H)12CU-r2:112_H2SitBu2)(4; Cp’ = $-CsMes), containing a p-silane ligand, was synthesized by the reaction of Cp’Ru(p-H)4RuCp’(1)with tBu2SiH2. The unusual coordination mode of di-tert-butylsilane was confirmed by means of ‘H, 13C, and 29SiNMR and IR spectroscopy. Treatment of 4 with 1 atm of CO affords a mixture of (5)and the p-silyl complex [Cp’Ru(CO)l2the p-silane complex [Cpau(C0)l2CU-r2:r2-H2SitBu2) +-r2-HSitBu2)(H) (6). The p-silane complex 5 is in equilibrium in solution with hydridop-silyl species 6. The equilibrium constant K, where K = [61/[51, was determined to be 1.3 at 303 K in benzene-&. Variable-temperature lH NMR measurements yielded thermodynamic parameters for conversion of 5 to 6: AH = 1.2 f 0.1 kcaVmol and A S = 4.5 f 0.1 edmol. The reaction of 4 with 5 equiv of PhSiHs yields the mixed-bridge bish-silyl) complex [ C ~ ’ R U ] Z ~ - ~ ~ - H S ~ ~ B ~ ~ ) ( ~(7b). - ~ ~When - H S4~isPtreated ~ H ) ~with - H12 ) (equiv H ) of Et2(7a) SiH2, the mixed-bridge bisk-silyl) complex [Cp’Ru12(CL-r2-HSitBu2)CU-r2-HSiEtH)CU-H)(H) is obtained via Si-C bond fission. The molecular structure of 5 , 7 a , and 7b were determined by single-crystal X-ray diffraction studies.
Introduction In connection with hydrosilylationl or dehydrogenative coupling of primary or secondary silanes,2 the reactions of silanes with transition-metal complexes have become of increased interest. In 1970, Graham and co-workers proposed a new coordination mode of hydrosilane, a two-electron-three-center (2e-3c) M-HSi interaction, in CpMn(CO)z(H)SiPh3on the basis of X-ray diffraction s t ~ d i e s .Since ~ this first example, a number of Si-H a-complexeshave been discovered and characterized by NMR4 and photoelectron spectros~opy.~ A Si-H a-complex of manganese, MeCpMn(C0)dH)Abstract published in Advance ACS Abstracts, July 15, 1995. (1)See, for example: (a)Ojima, I. In The Chemistry ofOrganosilicon Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Chapter 25,p 1479. (b) Speir, J. L. Adu. Organomet. Chem. 1979,17, 47. (2)(a) Aitken, C.; Harrod, J. F.; Samuel, E. J . Organomet. Chem. 1985,279,C11. (b)Aitken, C.; Harrod, J. F.; Samuel, E. J . Am. Chem. Soc. 1986,108,4059. ( c ) Aitken, C.; Harrod, J. F.; Gill, U. S. Can. J . Chem. 1987,65,1804. (d) Aitken, C.; Barry, J.; Gauvin, F.; Harrod, J. F.; Malek, A.; Rousseau, D. Organometallics 1989,8 , 1732. (e) Harrod, J. F.; Ziegler, T.; Tschinke, V. Organometallics 1990,9,897. (0 Tilley, T. D. Acc. Chem. Res. 1993,26,22. (g) Woo, H.; Heyn, R. H.; Tilley, T. D. J . Am. Chem. Soc. 1992, 114, 5698. (h) Woo, H.; Walzer, J. F.; Tilley, T. D. J . Am. Chem. SOC.1992,114,7047. (i)Woo, H.; Tilley, T. D. J . Am. Chem. Soc. 1989,111,3757.(i) Woo, H.; Tilley, T. D. J . Am. Chem. SOC.1989,111, 8043. (k) Forsyth, C. M.; Nolan, S. P.; Marks, T. J. Organometallics 1991,10,2543. (1) Corey, J. Y.; Chang, L. S.; Corey, E. R. Organometallics 1987,6,1595. (m) Chang, L. S.; Corey, J. Y. Organometallics 1989,8, 1885. (n) Corey, J. Y.; Zhu, X.; Bedard, T. C.; Lange, L. D. Organometallics 1991,10,924. (3)Graham, W.A. G. J . Organomet. Chem. 1986,300,81. (4)(a) Schubert, U.;Muller, J.; Alt, H. G. Organometallics 1987,6, 469. (b) Schubert, U.;Scholtz, G.; Muller, J.; Ackermann, K.; Worle, B. J . Organomet. Chem. 1986,306,303.
SiPhzF, was structurally characterized by means of a neutron diffraction study by Schubert et al.49697 In a previous communication, we reported the synthesis of the bis(U-silyl)complexes [C~‘RU(U-);~~-HS~RZ)I~(U-H)(H)(2a,R = Et; 2b,R = Ph; Cp‘ = );15-CsMes),by the reaction of Cp’Ru(p-H)rRuCp’(1)with R ~ s i H 2 . ~
1 Ph Ph
@
Ph Ph 2a; 2b;
R = Et R=Ph
3
In this reaction, the ruthenium tetrahydride complex Cp’Ru(U-H)4RuCp’(11,which readily generates unsatur(5)(a) Lichtenberger, D.L.; Rai-Chaudhuri, A. J . Am. Chem. SOC. 1989,111, 3583. (b) Lichtenberger, D.L.; Rai-Chaudhuri, A. Organometallics 1990,9, 1686. ( c ) Lichtenberger, D.L.; Rai-Chaudhuri, A. Inorg. Chem. 1990, 29, 975. (d) Lichtenberger, D. L.; RaiChaudhuri, A. J . Am. Chem. SOC.1990,112,2492. (6)Schubert, U.;Ackermann, K.; Worle, B. J . Am. Chem. SOC.1982, 104,7378. (7)Schubert, U.Adv. Organomet. Chem. 1990,30,151. (8)Suzuki, H.; Takao, T.; Tanaka, M.; Moro-oka, Y. J . Chem. SOC., Chem. Commun. 1992,476.
0276-7333/95/2314-3855$09.QQIQ 0 1995 American Chemical Society
Takao et al.
3856 Organometallics, Vol. 14,No. 8, 1995
ated sites on the same side of the molecular plane upon heating or treatment with a hydrogen acceptor, acts as a precursor of the active species for bimetadlic actiua-
'Bu 'Bu
ti~n.~
It is generally accepted that the (v2-X-Y)-M species are plausible intermediates in the oxidative addition of X-Y to the metal center. As far as silicon is concerned, there have been only a few examples of the oxidative addition of an Si-H bond via the well-characterized (v2Si-HI-metal complex, while an equilibrium between (v2-H2)Mand M(H2) has been proved in the chemistry of v2-H2complexes on the basis of variable-temperature 'H NMR studies.1° We are interested in studying the interaction of silanes with dinuclear unsaturated species and transformation from (v2-Si-H)-M species into metal hydrido-silyl complex. In the reaction of Cp'Ru(pHhRuCp' (1) with tBu2SiH2, we have successfully isolated a dinuclear complex bridged by a v2:v2-HzSitBu2 ligand. Here we describe in full detail its synthesis, characterization, and structure determination, as well as the oxidative addition of an agostic Si-H bond which forms a hydrido-silyl complex.
"b
Results and Discussion
L -
When tetrahydride complex 1 was treated with tBuzSiH2, the mono&-silane) complex [Cp'Ru(u-H)lz@v2:v2-H2SitBu2)(4) was exclusively obtained, while a bis(p-silyl) complex was formed in the reaction of 1 with dihydrosilanes with less bulky substituents.* The reaction of complex 1 with 1.5 equiv of tBu2SiH2 in toluene at room temperature for 4 h leads to the formation of mono&-silane)complex 4, which is isolated in 89% yield as a purple crystalline solid. Complex 4 is relatively stable to the air and moisture and is extremely soluble in nonpolar solvents, such as pentane or toluene. Complex 4 was fully characterized, and the p-v2:v2geometry of the tBu2SiH2 ligand was confirmed on the basis of the lH, 13C, and 29Si NMR and IR spectral data. 1.5 eq 'BU~SIM, toluene, rt, 4 h
-
*
"2
1 'Bo
t
'Bu
/
4
In the lH NMR spectrum of 4 measured at room temperature, three signals due to the Cp', tBu, and
4
-6
-8
,
-10 -12 -14 -16 -18
,
(PP'n)
Figure 1. Variable-temperature lH NMR spectra of [Cpau01-H)1~01-)7~:)7~-H2Si~Bu~) (4) showing hydride resonances: (A) 60 "C; (B)-50 "C; (C) -60 "C; (D)-120 "C. hydride ligands are observed at 6 1.89,1.11, and -11.12, respectively. Variable-temperature lH NMR spectra shown in Figure 1 clearly establish the fluxionality of the hydride ligands in complex 4. At ambient temperature, the four inequivalent hydrides are in timeaveraged environments and a broad singlet resonance is observed a t 6 -11.12. This resonance broadens and flattens at -60 "C.A sharp, low-temperature limiting spectrum is obtained a t -120 "C. At this temperature, the resonance due to the hydride ligands is split into two singlet peaks a t 6 -6.15 and -16.63. The signal at 6 -6.15 has satellite peaks due to a bonding interaction with silicon (Figure 2; 29Si,abundance 4.70%;J S i - H = 75 Hz). The coupling constant between 29Siand lH often has been employed as a criterion for the magnitude of the Si-H bonding interaction, as has the Si-H distance as determined by neutron or X-ray diffraction studies (Table 1). The J s i - ~value for the v2-Si-Hligand usually lies in the range of 20-140 Hz, intermediate between those of free silane (-200 Hz) and those characteristic of classical silyl hydrides (120 Hz). Therefore, the signals at 6 -6.15 and -16.63 are assigned t o the resonances due to hydride ligands with 2e-3c Ru-H-Si interactions (Ha) and those bridging , We propose between two rutheniums (Hb)respectively.
Ruz Complexes Containing a psilane Ligand
Organometallics, Vol. 14, No. 8, 1995 3857
strong v(C0) absorption^.^ The v(M-H-Si) values for the non-carbonyl complexes Cp2Zr(X)(NtBuSiMe2H)(X = H, I, Br, C1, F) have been reported recently by Berry and co-worker~;'~ the zirconium complexes have ZrH-Si stretching frequencies ranging from 1912 to 1998 cm-', a red shift of ea. 100-200 cm-l compared with v(Si-H) for uncoordinated HNtBuSiMe2H (2107 cm-l). Stone et al. also reported the v(Pt-H-Si) band for the dinuclear bisb-si1yl)platinum complex [Pt(PR'3)(p-~7~HSiR2)Iz (R = Ph, Me; PR3 = PCy3, PPh3, PMetBuz, PiPrzPh), to appear a t ca. 1650 cm-l.15 (wm1 In order to assign the Ru-H-Si stretching frequency, -5.8 -6.0 6.2 -6.4 -16.4 -16.6 -16.8 .17.0 we synthesized an isotopomer of complex 4 by the Figure 2. lH NMR spectrum of [ C ~ ' R U ~ ~ - H ) I Z C U - ~ ; ~ ~ reaction : ~ ~ - H Zof - Cp'Ru@-D)dRuCp'( 1 4 4 ) with tBu~SiD2.The SitBuz)(4) showing hydride resonances measured at -120 IR spectra of 4 and 4 4 4 are shown in Figure 4. A broad "C. The 29Sisatellites are indicated (0). absorption assignable to the stretching vibration of the agostic Ru-H-Si unit was observed at 1790 cm-l an intramolecular site exchange of hydrides among two (spectrum A), which was confirmed by the fact that this Ru-H-Si sites and two Ru-H-Ru sites t o explain the broad absorption disappears in the spectrum of the VT-NMR data. From the line shape analysis of the deuterated complex 444 and a new absorption of 4Ruvariable-temperature lH NMR data, the AG* value of D-Si) appears at 1290 cm-l (spectrum B). The difthis fluxional process was estimated a t ca. 8.5 kcaYmol ferential spectrum (spectrum C) clearly shows the at the coalescence temperature (measured at 500 MHz), isotopic shift. This broad absorption was distinguished which is slightly smaller than those estimated for the from that of a metal-hydride or a noncoordinated Si-H bish-silyl) complexes 2a and 2b.8 bond of a bridging silicon ligand. In the IR spectrum In the proton-coupled 29SiNMR spectrum of 4, the of [ C ~ ' R U ] Z ~ - ~ ~ - H S ~ ~ B U ~ ) C ~ - ~ ? ~ - H(7b), S~P~H)@-H) JS+Hcoupling with the directly bound hydrogen atom obtained in the reaction of 4 with PhSiHs (vide infra), apparently was not observed because it was not sepathe stretching vibration of the terminally bonded hyrable from the multiplet due t o those with tert-butyl dride v(Ru-H) was observed at 2054 cm-' as a sharp groups. When the butyl proton at 6 1.11is irradiated, absorption together with the broad absorptions of 4Ruthe 29Sisignal appears at 6 75.5 as a quintet (Figure 3; H-Si) a t 1813 and 1613 cm-l. v(Si-H) values for the J s i - ~= 34.2 Hz). The coupling constant is about half bridging silylene ligand (M-SiHR-M), however, have of that of the satellite peaks observed in the lH NMR been observed in the range of 1955-2074 cm-1,16,17and spectrum measured at -120 "C. The above-mentioned v(Si-H) for 7b is observed at 2036 cm-l as a relatively site exchange of the hydride ligands is rapid compared strong and sharp absorption. The significant low energy to the NMR time scale at room temperature. The of v(Ru-H-Si) of 4 (1790 cm-l) compared with the apparent coupling constant (JSI-H= 34.2 Hz) must, v(Si-H) value for tBuzSiHz (2116 cm-l)l8 indicates a therefore, be an averaged value of those observed for distinct reduction in the Si-H bond order due to its each hydride site. The 29Siresonance of 4 (6 75.5) shifts coordination t o the ruthenium centers. slightly upfield compared to those of the bish-silyl) An isotopic shift between G(H-Si-H) and G(D-Sicomplexes 2a and 2b (6 111.7 and 95.0, respectively). D) also was observed. The differential spectrum reThe M-H-Si interaction is detectable by means of vealed that a relatively strong absorption of G(H-SiIR spectroscopy, as was found in the case of r2-Hz H) at 1050 cm-l was shifted to 760 cm-l by deuteration. complexeslO or agostic C-H bonds.13 Coordination of a The H-Si-H deformation mode showed a blue shift Si-H a-bond to a transition metal results in a weakenupon coordination; strong bands assignable to G(H-Siing of the Si-H bond, and therefore, the stretching H) of the uncoordinated tBu2SiH~appeared at 928 and frequency of the Si-H bond decreases. Although there 851 cm-l,18 which were 100-200 cm-' lower than the have been several reported examples of transition-metal 6(H-Si-H) value for 4. The H-Si-H angle would be complexes with M-H-Si 2e-3c interactions, most of firmly fixed upon coordination to the ruthenium center them have carbonyl groups as supporting ligands. The M-H-Si stretching of them often is obscured by the (14)Procopio, L.J.;Carroll, P. J.; Berry, D. H. J . Am. Chem. SOC.
2L2L
(9)(a) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Moro-oka, Y. Organometallics 1988,7 , 2243. (b) Suzuki, H.; Omori, H.; Moro-oka, Y. Organometallics 1988, 7, 279. (c) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima, M.; Tanaka, M.; Moro-oka, Y. Organometallics 1994,13,1129. (10)See, for example: (a) Crabtree, R. H. Angew. Chem., Int. Ed. E n d . 1993.32.789. (b) Heinekev. D. M.: Oldham, W. J., Jr. Chem. Re;. 1993,93,913. (cj Jessop, P. G,; Mor& R. H. Coord. Chem. Rev. 1992,121, 155. (d) Crabtree, R. H.; Luo, X.-L.; Michos, D. Chemtracts: Inorg. Chem. 1991,3,245.(e) Crabtree, R.H. Acc. Chem. Res. 1990,23,95. (fl Henderson, R. A. Transition Met. Chem. 1988,13, 474. (g) Kubas, G. Acc. Chem. Res. 1988,21,120. (11)(a) Takao, T.; Suzuki, H.; Tanaka, M. Organometallics 1994, 13,2554. (b) Matthias, D.; Reisgys, M.; Prltzkow, H. Angew. Chem., Int. Ed. Engl. 1992,31,1510. (12)(a) Jetz, W.; Graham, W. A. G. Inorg. Chem. 1971,10,1159. (bj Schubert, U.Chem. Ber. 1988,121,959. (13)Brookhart, M.; Green, M. L. H. J . Organomet. Chem. 1983,250, 395 and references cited therein.
1994,116,177. (15)Auburn, M.; Ciriano, M.; Howard, J . A. K.; Murray, M.; Pugh, N. J.: SDencer. J. L.; Stone, F. G. A.: Woodward. P. J . Chem. SOC., Dalton h n s . 1980,659. (16)McDonald, R.;Cowie, M. Organometallics 1990,9, 2468. (17) (a) Tobita, H.; Kawano, Y.; Shimoi, M.; Ogino, H. Chem. Lett. 1987,2247. (b) Wang, W.; Hommeltoft, S. I.; Eisenberg, R. Organometallics 1988, 7 , 2417. (c) Wang, W.; Eisenberg, R. J . Am. Chem. SOC.1990,112,1833. (d) Herrmann, W. A.; Voss, E. J . Organomet. Chem. 1985,284,47. (e) Malisch, W.; Ries, W. Angew. Chem., Int. Ed. Engl. 1978, 17, 120. (0 Zarate, E. A,; Tessier-Youngs, C. A,; Youngs, W. J. J . A m . Chem. SOC.1988,110,4968. (18)IR spectra of the free silanes tBuzSiHz and tBuzSiDz were measured. A band for the stretching vibration of Si-H bonds appeared at 2116 cm-', while that for Si-D was observed at 1533 cm-'. Absorptions assignable to G(H-SitBuz-H) appeared at 928 and 851 cm-', which shifted to 677 and 569 cm-l, respectively, upon deuteration. Assignments of these absorption bands are corroborated by the literature: Kniseley, N.; Fassel, V. A,; Conrad, E. E. Spectrochim. Acta 1969,651.
3858
Organometallics, Vol. 14, No. 8, 1995
Takao et al.
Table 1. 29SiN M R Data of Hydridosilyl Complexes Having 2e-3c Interactions entry no.
compd
(Hz)
Js,-M-H
[C~ZT~IZO~-H)O~-~~-HS~P~H)~
58 135.4 CpzZr(F)(NtBuSiMezH) 113.2 CpzZr(H)(NtBuSiMezH) 70.8 (rl6-CsMes)Cr(C0)z(qZ-HSiPh2H) 135.7 Cr(CO)s[HSi(Mes)P(Cy)la 69 MeCpMn(CO)(PMe3)(qZ-HSiNpPhH)* 65.4 Cp’Mn(CO)z(q2-HSiPhzHT 63.5 MeCpMn(CO)z(q2-HSiPhzH) 38 MeCpMn(CO)(PMe3)(q2-HSiPhzH) 75 [C~’RU(C~-H)IZ~-~~:~~-HZS~~BUZ) [Cp’Ru12(Cc-q2-HSiPh~)~-SiPhzCH-CH2)~-H)(H) 53.6 32.9 [C~’RU(C!O)]Z(U-H)(,LL-~~-HS~~BUZ) [ C ~ ’ R ~ ~ C O ~ ~ Z ~ ~ - ~ ~ ~ : ~ ~ - H Z S ~ ~22.4 B~
1 2 3 4 5 6 7 8 9 10 11 12 13 14e 15e
‘Js-H
(Hz)
2b 14 14
197
4a llb
208 200.3 205.2 191
4b 4b 4b 4b d
lla d d
Z~
12a 12b
20
MeCpMn(CO)(PMe3XH)(SiCld CpzW(H)Si(SiMe&
ref
148
3.5
Cp = 75-C5H5.* MeCp = q5-CH3C5H4. Cp’ = v5-CsMe5. This work. e Compounds having no direct Si-H interaction.
76 5
76.0
75.5
75.0
74.5
Figure 3. 29SiNMR spectrum of [Cpau01-H)1~01-v~:v~-H~SitBu2) (4) measured at 20 “C upon irradiation at a resonance for the tert-butyl protons (6 1.11).
in ,u-v2:v2geometry. The energy for the deformation vibration would, therefore, increase. As far as the dinuclear p-y2:y2-silane complex is concerned, only two examples, [Re2(C0)&-v2:v2-H2SiR2)I (R = Me, Ph)lgaand [Mnz(C0)6(dppm)1U-~~:r1~-HzSiPh2)1,1gbwere reported prior to our work, while there have been several reported examples of a mononuclear silane complex. These complexes were characterized mainly on the basis of NMR studies. Although a single crystal of 4 suitable for the X-ray diffraction studies was I . . . I . ~ . . , , , , . , , not obtained,20all of the above data strongly indicate 4000 3000 2000 1500 1000 500 the coordination of tBu2SiH2 in a p-v2:v2geometry. A (cm-’) structure determination of the p-v2:v2-H2SitBu2ligand Figure 4. Infrared spectra of (A) [Cp’Ru@-H)1z@-y2:y2was performed by using a crystal of the analogous H2SitBuz)(4) and (B)[ C ~ ’ R U ~ ~ - D ) I Z ~ ~ - ~ ~(: 4~ 4~ )- D ~ S ~ ~ B U p-silane complex [C~’RU(CO)~~CU-)~~:~~-H~S~~BU~) ( 6 )oband (C) a differential spectrum of them. tained by the reaction of 4 with CO. This is the first example of a structurally fully characterized dinuclear Reaction of the p s i l a n e Complex with CO. p-y2:v2-silanecomplex (videinfia). Complex 4 reacts with 1atm of CO a t room temperature (19)(a) Hoyano, J. K.; Elder, M.; Graham, W. A. G. J . Am. Chem. for 12 h t o yield a mixture of the p-silane complex SOC.1969,91, 4568. (b) Elder, M. Inog. Chem. 1970,9, 762. (c) [Cp’Ru(CO)]21U-v2:v2-H2SitBu~) (5; 43% yield based on CarreAo, R.; Ruiz, M. A,; Jeannin, Y.; Philoche-Levisalles,M. J . Chem. lH NMR) and the p-silyl complex [Cp’Ru(C0)]2(,~-y~SOC.,Chem. Commun. 1990, 15.
Y
Ruz Complexes Containing a p s i l a n e Ligand
Organometallics, Vol. 14, No. 8, 1995 3859
HSitBuz)(H)(6; 53%), together with a small amount of [Cp'Ru(CO)zlz (4%) (eq 2L2l
c9
n
'Bu 'Bu \ /
4
'Bu 'Bu r.1
A
and / o r
'BU 'Bu
t l
-C30
5
Figure 5. Molecular structure of [C~'RU(CO)IZ~~-~~:~~-H SitBuz)(51, with thermal ellipsoids at the 30% probability
level. 6
Table 2. Selected Bond Lengths (A)and Angles (dee) for 5
The structure of complex 5 was determined by X-ray Ru(1)-Ru(~) 2.9637(8) crystallography using a single crystal obtained from 2.447(1) Ru( 1)-Si(1) Ru(2)-Si(l) 2.457(1) Ru(l)-H(2) Ru(2)-H(l) 1.44(4) 1.43(4) pentane at -20 "C. The structure of 5, shown in Figure Ru(l)-C(l) Ru(2)-C(2) 1.829(4) 1.816(4) 5, clearly depicts the unique p q 2 : v 2 geometry of the 1.77(3) 1.75(4) Si(l)-H(2) Si(l)-H( 1) tBuzSiH2 ligand. The crystal data for 5 are given in the 1.957(4) 1.961(4) Si(l)-C(3) Si(l)-C(7) Experimental Section (Table 5), and selected bond 1.153(5) 1.162(5) C(1)-0(1) C(2)-0(2) 2.201(4) 2.211(4) Ru( l)-C(11) R~(2)-C(21) lengths and bond angles are listed in Table 2. 2.276(4) 2.274(4) Ru(1)-C(12) Ru(2)-C(22) Two terminal carbonyl groups are mutually trans 2.345(4) 2.350(4) Ru(2)-C(23) Ru( 1)- C(13) with respect to the Ru(l)-Ru(2) vector. Two hydrogen 2.309(4) 2.308(4) R~(2)-C(24) Ru(1)- C(14) atoms, H(1) and H(2), compose 2e-3c bonds between 2.254(4) 2.257(4) Ru(2)-C(25) Ru(1)- C(15) silicon and each ruthenium. The bridging silicon is sepRu(2)-Ru( 1)-Si( 1) 52.97(3) Ru(l)-Ru(2)-Si(l) arated from each ruthenium, Ru(1) and Ru(2), by 2.447Ru(2)- Ru(1)- C(1) 83.6(1) Ru(1)-Ru(2)-C( 2) (1)and 2.457(1) A, respectively. These distances fall Ru(2)-Ru(l)-H(2) Ru( 1) - R u ( ~)-H( 1) 97(1) in the reported range for a Ru-Si single bond (2.288Si(l)-Ru(l)-C(l) 92.U1) Si(1)-Ru( 2)-C(2) (11)-2.507(8) A),11,22 but they are comparatively long. Si(l)-Ru(l)-H(2) 44(1) Si(l)-Ru(2)-H(l) C(l)-Ru(l)-H(2) 95(1) C(~)-RU(~)-H(~) Electron counting that keeps complex 5 diamagnetic Ru(l)-Si( 1)-Ru(2) 74.38(4) C(3)-Si(l)-C(7) requires a single bond between the two rutheniums, and Rdl)-C(l)-O(l) 170.7(4) Ru(2)-C(2)-0(2) the Ru(l)-Ru(2) distance of 2.9637(8) A is comparable with that of Ru-Ru single bonds.22f,23The relatively tween Si and H upon coordination t o ruthenium. acute Ru(l)-Si(l)-Ru(2) angle (74.38(4)")also suggests Although X-ray crystallography is not the best method a bonding interaction between the two r u t h e n i ~ m s . ~ ~to determine the location of the H atom attached to a The Si(l)-H(l) and Si(l)-H(2) distances, 1.77(3)and heavy atom, the observed Si-H bond lengthening is 1.75(3)A, respectively, are reasonably longer than those consistent with the reduced J s ~ - H coupling obtained by reported for organosilicon compounds (1.48 Ai).25This 29SiNMR spectroscopy (vide infra). supports the decrease in the bonding interaction beIn the 'H NMR spectrum of the mixture of 5 and 6, three resonances arising from 5 appear at 6 1.89,1.26, (20)The psilane complex 4 was crystallized from pentane a t -20 "C in the orthorhombic system, space group Ama2, with a = 17.832(5) = 19.780(7)A, c = 8.674(3) A, and 2 = 4. Intensity data were collected at 23 "C on a Rigaku AFC-5R four-circle diffractometer with graphite-monochromated Mo K a radiation (1= 0.710 69 A) in the 6.0" =. 28 < 50.0" range. The intensity of the collected data were weak, and the quality of the data were not sufficiently good because the crystal gradually decomposed during data collection. The Ru atom positions were determined using Patterson methods. The remaining non-hydrogen atoms were located from successive difference Fourier map calculations and refined by using full-matrix least-squares techniques on F. The current R value is 0.067 for 2804 independent reflections with F, > 5dF0).Although the refinement did not sufficiently converge, the X-ray data sufficiently elucidate the atom connectivity of the structure. The resulting structure of 4 is fully consistent with the data obtained from 'H, 13C, and 29Si NMR spectroscopy. Bond lengths and angles of the RuzSi core are as follows: Ru-Si = 2.51(1)A, Ru-Ru = 2.755(5)A; Ru-Si-Ru = 66.6(4)",Ru-Ru-Si = 56.7(2)". (21) (a) Davison, A,; McCleverty, J . A.; Wilkinson, G. J . Chem. SOC. 1963,1133. (b) King, R. B.; Iqbal, M. Z.; King, A. D., Jr. J . Organomet. Chem. 1979,171,53.
A, b
(22)(a) Straus, D. *Tilley, T. D.; Rheingold, A. L.; Geib, S. J. J . Am. Chem. SOC.1987, 109, 5872. (b) Straus, D. A.; Zhang, C.; Quimbita, G. E.; Grumbine, S.D.; Heyn, R. H.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J. J . Am. Chem. SOC.1990,112,2673. (c) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J . Chem. SOC., Chem. Commun. 1992, 1201. (d) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1992, 11, 3918. (e) Campion, B. K.; Heyn, R. H.; Tilley, T. D.; Rheingold, A. L. J.Am. Chem. SOC.1993,115,5527. (D Crozat, M. M.; Watkins, S. F. J . Chem. SOC.,Dalton Trans. 1972, 2512. (g) Einstein, F. W. B.; Jones, T. Inorg. Chem. 1982,21, 987. (h) Klein, H.-P.; Thewalt, U.; Herrmann, G.; Suss-Fink, G.; Moinet, C. J . Organomet. Chem. 1985,286,225. (i) Brookes, A.; Howard, J.; Knox, S.A. R.; Riera, V.; Stone, F. G. A,; Woodward, P. J . Chem. SOC.,Chem. Commun. 1973,727. (j)Edwards, J. D.; Goddard, R.; Knox, S.A. R.; Chem. McKinney, R. J.; Stone, F. G. A,; Woodward, P. J . Chem. SOC., Commun. 1975,828. (k) Howard, J.; Woodward, P. J . Chem. SOC., Dalton Trans. 1975,59. (1) Harris, P. J.; Howard, J. A. K.; Knox, S. A. R.; McKinney, R. J.; Phillips, R. P.; Stone, F. G. A,; Woodward, P. J . Chem. SOC.,Dalton Trans. 1978,403. (m) Djurovich, P. I.; Carroll, P. J.; Berry, D. H. Organometallics 1994,13, 2551.
Takao et al.
3860 Organometallics, Vol. 14, No. 8, 1995
and -13.60, which are assigned to the Cp’, tBu-groups, and hydride ligands, respectively. Satellite peaks due to coupling with 29Siare observed besides the hydride signal. The 29Si NMR spectrum, measured with irradiation of tBu protons, shows a triplet at 6 186.2 (JSi-H = 22.4 Hz). The J s i - ~coupling of 22.4 Hz is much smaller than that for 4 ( J s i - ~= 75 Hz), and this result also suggests the Si-H bond weakening, although a is not simply a reflection of the bond decrease in J s ~ - H order,5a Coordination of CO instead of the hydride ligands would cause a reduction of the Si-H bond order and would result in a distinct weakening of the v2-Si-H bond. While the structure of 5 exhibits noncrystallographic C2 symmetry around the silicon atom, that of complex 6 does not. All of the lH NMR signals for complex 6 are inequivalent as follows: Cp’ (6 1.98 and 1.731, tBu (6 1.42 and 1.411, and hydrides (6 -11.79 and -14.40). Moreover, satellite signals are observed only beside the hydride signal at 6 -11.79. The 29Siresonance arising from 6 appears at 6 168.2 as a doublet of doublets (JSi-H = 31.6 and 7.9 Hz). It is noteworthy that the 29Sisignal for 6 is observed as a doublet of doublets, while that for complex 5 is a triplet. The J s i - ~coupling of 31.6 Hz is common for the hydrides with 2e-3c M-H-Si interactions, but that of 7.9 Hz is too small. Therefore, we can conclude that complex 6 adopts a mono@-silyl)form having a terminal (Ru-H) or bridging (Ru-H-Ru) hydride ligand. Thus far, only two mono@-silyl)complexes have been characterized by means of X-ray diffraction studies. Fryzuk et al. have synthesized a dirhodium complex containing a p-diphenylsilyl ligand by the reaction of [(dippe)Rh@-H)]z(dippe = 1,2-bis(diisopropylphosphino)ethane) with 1 equiv of p h ~ S i H 2 .The ~ ~ dirhodium p-silyl complex [(dippe)Rh12@-a2-HSiPh2~-H) was shown to have a p-silyl ligand and a bridging hydride. Harrod et al. have determined the structure of [Cp2Ti12@-v2HSiPhH)@-H),which was obtained as an intermediate of the dehydrogenative coupling of phenylsilane using titanocene catalyst.2b Ph
Ph
Remarkably, the p-silane complex 5 is in equilibrium in solution with the hydrido-p-silyl complex 6 (Scheme 1). The solution of the isolated single crystal of 5 comes to an equilibrium with 6 in a few hours. Temperature(23) (a) Churchill, M. R.; Hollander, F. J.; Huchinson, J. R. Inorg. Chem. 1977,16, 2655. (b) Nucciarone, D.; Taylor, N. J.; Carty, A. J.; Tiripicchio, A,; Camellini, M. T.; Sappa, E. Organometallics 1988,7, 118. ( c ) Parkins, A. W.; Fischer, E. 0.;Huttner, G.; Regler, D.Angew. Chem., Int. Ed. Engl. 1970,9, 633. (d) Bruce, M. I.; Cairns, M. A,; Cox, A.; Green, M.; Smith, M.; Woodward, P. J. Chem. SOC.D 1970, 735. (e) Howard, J.; Knox, S. A. R.; Stone, F. G. A,; Woodward, P. J. Chem. SOC. D 1970,1477.(f, Howard, J.;Woodward, P. J. Chem. SOC. A 1971,3648. (24) (a) Coleman, J. M.; Dahl, L. F. J.Am. Chem. SOC.1967,89, 542. (b) Stevenson, D. L.; Dahl, L. F. J . Am. Chem. SOC.1967,89, 3721. ( c ) Dahl, L. F.; deGil, E. R.; Feltham, R. D. J . Am. Chem. SOC. 1969,91, 1653. (d) Connelly, N. G.; Dahl, L. F. J. Am. Chem. SOC. 1970,92, 7470. (e) Connelly, N. G.; Dahl, L. F. J. Am. Chem. SOC. 1970,92, 7472.
Scheme 1 ‘Bu ‘Bu t1
Oxidative Addltlon Of
q’-Sl-H Bond L
T
0
0
Reductlve lllmlnatlon between Ru-Si and Ru-H
5 ‘Bu ‘Bu
‘Bu ‘Bu t/
6
dependent behavior is observed for the two resonances (Figure 6), and the equilibrium constant K, where K = [6y[51, was determined on the basis of lH NMR integration of the Cp’ signals. The constant K is 1.3, 1.6, 1.8, and 2.0 at 30, 60, 90, and 110 “C, respectively. The constant K falls to 1.3 again on cooling down t o 30 “C. These results yield the following thermodynamic parameters for the conversion of 5 to 6: AH = 1.2 f 0.1 kcal/mol and A S = 4.5 f 0.1 edmol. While several examples of a tautomeric equilibrium between a nonclassical v2-H2complex and a classical dihydride complex are known,1° only one example has been reported for a Si-H bond, by Luo and K ~ b a s They . ~ ~ reported the first example of a tautomeric equilibrium between an v2-SiH4 complex and a hydrido-silyl species of molybdenum. As far as a dinuclear complex is concerned, the equilibrium between 5 and 6 is the first example of such tautomerism. Reaction of the p-Silane Complex with PhSiHa. As mentioned above, agostic Si-H bonds in the bis@silyl) complex [Cp’Ru@-v2-HSiPh2)12@-H)(H) (2b)oxidatively add to ruthenium to generate the bis@-silylene) complex [Cp’Ru@-SiPh2)@-H)lz(3) upon heating in solution.8 This result strongly suggests that the reaction of Cp’Ru@-H)4RuCp’(1)with R2SiH2, which yields p-v2-silyl complexes 2, proceeds by way of an agostic p-y2:y2-silanespecies. p-Silane complex 4 is, therefore, expected to react with a dihydrosilane to form the bis@-silyl)complex as a result of the oxidative addition of the v2-Si-H bond. To test this possibility, we carried out the reaction of complex 4 with various hydrosilanes R,SiH4-,. The reaction of 4 with a less bulky silane such as PhSiH3 or EtzSiH2 proceeds to form the expected bis@-silyl)complex [Cpau12@-v2-HSitBu2)~-v2-HS~~)@-HI or [Cp’Ru12@-y2-HSitBuz)Cu-y2-HSiEtH)(u-H), respectively, while the reaction of 1 or 4 with an excess of tBu2SiH2 does not show any sign of the formation of the p-silyl complex. p-Silane complex 4 readily reacts with 5 equiv of phenylsilane at room temperature to yield the mixedbridge bis@-silyl)complex [Cp’Ru12(~-)7~-HSi~Buz)(u-r~HSiPhH)@-H)(H)(7b)(eq 3). This result demonstrates (25) (a) Wells, A. F. In Structural Inorganic Chemistry 3rd ed.; Oxford University Press: London, England, 1962; p 696. (b) Baxter, S. G.; Mislow, K.; Blount, J. F. Tetrahedron 1980, 36, 605. (c) Allemand, J.; Gerdil, R. Cryst. Struct. Commun. 1979,8 , 927. (26) Fryzuk, M. D.; Rosenberg, L.; Rettig, S. J. Organometallics 1991, 10, 2537. (27) Luo, X.-L.; Kubas, G. J.; Burns, C. J.; Bryan, J. C.; Unkefer, C. J. J . Am. Chem. SOC.1996,117, 1159.
R u Complexes ~ Containing a psilane Ligand
15
15
6
I
I
I
I
2.0
1.8
1.6
1.4
Organometallics, Vol. 14, No. 8, 1995 3861
I
I
'
I
'
I
1.2 -11.0 -12.0 -13.0 (PPW
'
I
~
I
-14.0 -15.0
and tert-butyl groups are shown on the left side of the figure, and hydride resonances are displayed on the right side. 'Bu 'Bu
I/
/
\I
5 equiv of PhSiH,
'
l
-12.0
'
l
-13.0
'
i
'
-14.0
*
rt, 2 h 4
that bish-silyl) complexes are formed by way of a p-silane intermediate in the reaction of 1 with secondary silanes. Complex 7b can be isolated by crystallization from cold pentane and characterized by means of lH and 13CNMR and IR spectroscopy and elemental analysis. The 'H NMR measurement of 7b a t -90 "C affords the low-temperature limiting spectrum. In the lH NMR spectrum measured a t -90 "C, four resonances for hydride ligands are observed at 6 -11.64, -12.84, -14.00, and -16.46. Among them, satellite peaks due t o coupling with 29Sinuclei appear beside two signals a t 6 -11.64 (JSi-H = 26 Hz) and 6 -14.00 (JSi-H = 49 Hz). They can, therefore, be attributed t o the hydrides
l
-15.0
'
i
-16.0
'
l
-17.0
(ppm)
(ppm)
Figure 6. 'H NMR spectra of the mixture of [Cp'Ru(CO)lzCU-v2:q2-H2SitBu2)(5) and [Cp'Ru(C0)12@-q2-HSitBu2)(H) (6): (A) 30 "C; (B)60 "C; (C) 110 "C. Resonances for Cp'
t
l
-11.0
Figure 7. Variable-temperature
'H NMR spectra of
[C~~U]~CU-~~-HS~~BU~)CU-~~-HS~P~H)CU-H)(H) (7b)showing the hydride resonances: (A) -90 "C; (B)-9 "C; (C) 20 "C; (D)80 "C. with Ru-H-Si 2e-3c interactions. The rest are assigned to terminal and bridging hydrides (Ru-H, and Ru-H-Ru). The lH NMR spectra of the hydride region in Figure 7 demonstrate the fluxionality of 7b. Two hydride signals a t 6 -11.64 and -12.84 coalesce into one signal (6 -12.30) a t -9 "C, and the remaining two signals also coalesce (6 -15.45) a t 0 "C. Although the two newly appearing signals at 6 -12.30 (2H) and 6 -15.45 (2H) never coalesce in spite of further warming to 80 "C, the four hydride ligands exchange coordination sites, with one another. A 'H NMR spin saturation transfer experiment reveals a slow exchange of hydrides between the two sites: irradiation at 6 -15.45 resulted in a 50% decrease in the intensity of the proton signal at 6 -12.30 and vice versa. The signals for the Cp' ligands are observed at 6 1.93 and 1.66 at -90 "C. They broaden upon warming and coalesce at -28 "C. The exact mechanism to account for this complicated temperature dependence of the spectra still has not been elucidated. At room temperature, the resonance of the SiH(terminal) group is observed at 6 6.30 as a sharp signal with satellite peaks (JSi-H = 172 Hz). The intensity of the Si-H resonance did not decrease upon irradiation at the hydride resonances. This result shows that the exchange process between Si-H(termina1) and Ru-H is negligible. Two signals for tert-butyl groups on the bridging silicon are found at 6 1.24 and 1.05. This indicates complex 7b has a butterfly structure, and the signals
3862 Organometallics, Vol.14,No.8, 1995
I (A)
I
t
Takao et al.
H-Si) bands and two different JS1-H values for the satellite peaks were observed in the IR spectrum and the low-temperature lH NMR spectrum, respectively. The unusually long Ru(2)-Si(2) distance may be rationalized in terms of the great contribution of a v2-Si-H complex such as resonance hybrid I.
The Cp' ligands of 7b are bent away from Si(2) with respect to the Ru(l)-Ru(2) vector (Figure 10B). The phenyl group on Si(1)occupies the axial rather than the equatorial position (Figure 10A). This implies that the equatorial positions of bisb-silyl) complexes are steriv(Si.H) cally more congested by the two Cp' ligands than the axial positions. L 8 , ' , 1 , 8 , * ~ , * , ~ ~, 1 1 3500 3000 2500 2000 1500 2100 2050 2000 l! Reaction of the psilane Complex with EtzSiH2. In the reaction of 4 with an excess of EhSiHz, the mixedbridge bisb-silyl) complex [ C ~ ' R U I ~ ~ ~ - ~ ~ - H S ~ ~ B U Z Figure 8. (A) Infrared spectrum of [Cpaul~@-~~-HSi~Buz)@q2-HSiPhH)@-H)(H) (7b).(B) Infrared region for the YHSiEtH)@-H)(H)(7a) was unexpectedly obtained as a (Ru-H) and v(Si-H) bands of 7b. result of an unusual Si-C(ethy1) bond fission (eq 4). The '
I
are assigned to the axial and equatorial tBu groups of 7b, respectively. We have observed that resonances for the substituents on the bridging silicon in the axial position appeared upfield from those for the equatorial position, seemingly because of the shielding effect of the Cp' ring. In the IR spectrum of 7b, two sharp bands were observed at 2054 and 2036 cm-l (Figure 8). A shoulder peak at 2054 cm-' is assigned t o v[Ru-H(termina1)l. For analogous p-silyl complexes 2a and 2b, the ~ [ R u H(termina1)l bands appear at 2066 and 2082 cm-', respectively.8 The other absorption at 2036 cm-l was relatively strong and was assignable to the stretching mode of the Si-H on bridging silicon, and this value falls in the reported range for the dSi-H) values of M-SiHR-M ligands (1955-2074 cm-l).16J7 In addition to these two sharp absorptions, two broad and characteristic absorptions of the $-Si-H bond were observed at 1813 and 1613 cm-1.28 The structure of the mixed-bridgebisb-silyl) complex 7b determined by X-ray diffraction studies is displayed in Figure 9. Table 3 lists some of the relevant bond distances and angles. The RusSiz core forms a folded quadrilateral, as bis(p-diethylsilyl)complex 2a does.8 Different Ru-Si bond lengths represent the existence of 2e-3c interactions around Ru(2); the distance of the agostic bond Ru(2)Si(1) (2.438(1) A) is lon er than that of Ru(1)-Si(1) (2.300(3) A) by ca. 0.14 if, and the distance of Ru(2)Si(2) (2.675(1) A) is ca. 0.30 A longer than that of Ru(2)-Si(2) (2.37.31) A). While the Ru(1)-Si(1) and Ru(lI-Si(2) distances lie in the reported range of RuSi single bonds (2.29-2.51 the Ru(2)-Si(2) distance of 2.675(1) A is much longer. In contrast, the other agostic Ru(2)-Si(l) distance of 2.438(1) A is shorter than that found in 2a (average 2.56 A).8 This result is well consistent with the fact that two distinct ~ ( R u (28) The v(Ru-H-Si)
bands of the bisb-silyl) complexes 2 were observed in the region of 1720-1790 cm-': Takao, T.; Yoshida, S.; Suzuki, H.; Tanaka, M. Manuscript in preparation,
'Bu 'Bu t. /
4
'Bu
!BU
ti Et 7a
(4)
reaction proceeds at 100 "C in a sealed tube to generate 7a in 90% yield, together with a small amount (45%) of bisb-diethylsilyl) complex 2a. A notable feature of this reaction is the occurrence of Si-C(alky1) bond cleavage. While a number of examples of Si-H and SiC(ary1) bond cleavage by transition-metal complexes exist, successful examples of the Si-C(alky1) bond are scarce in the chemistry of mononuclear transition metal c o m p l e x e ~ .Complex ~ ~ ~ ~ ~ 7a can be isolated from the reaction mixture by crystallization and characterized by means of lH and 13C NMR and IR spectroscopy. A single crystal of 7a suitable for an X-ray diffraction study was obtained from pentane. Figure 11 displays the molecular structure of 7a, and Table 4 lists the bond distances and angles. The structure shown in Figure 11 is fully consistent with the spectral data. The complex contains two p-silyl ligands. One of them is a p-HSitBu2 and other is a p-HSiHEt ligand in which the bulky ethyl group occupies a less congested axial position. Although the positions of the hydrogen atoms with agostic interactions among Ru and Si could not be determined by the difference Fourier synthesis, it can be concluded on the basis of the Ru-Si distances that two agostic hydrogens bridge R d l ) and two silicon atoms. The Ru(l)-Si(l) and Ru(lI-Si(2) distances of 2.414(3) and 2.680(3) A, respectively, are significantly longer than the values for Ru(2)-Si(l) (2.322(3)A)and (29)Kakiuchi, F.; Furuta, K.; Murai, S.; Kawasaki, Y. Organometallics 1993,12, 15. (30)Hofmann, P.; Heiss, H.; Neiteler, P.; Muller, G.; Lachmann, J. Angew. Chem., Int. Ed. Engl. 1990,29,880.
RUBComplexes Containing a psilane Ligand
Organometallics, Vol. 14, No. 8,1995 3863
C32 c22
c33
Figure 9. Molecular structure of [Cp’Ru]2(,M-v2-HSitBu2)@-v2-HSiPhH)(,M-H)(H) (7b),with thermal ellipsoids at the 30% probability level. Table 3. Selected Bond Lengths (A)and Angles (deg) for 7ba Ru(l)-Ru(2) Ru(l)-Si( 1) Ru(l)-Si(2) Ru( 1)-H( 1) Ru( 1)-H(2) Si(l)-H(3) Si(l)-H(5) Si(l)-C(l) Ru(l)-C(15) Ru(l)-C(16) Ru(l)-C(17) Ru(l)-C(18) Ru(1)-C( 19) Cp(l)-Ru( l)-Ru(2) Si(l)-Ru(l)-Si(2) H(l)-Ru( 1)-H(2) Si(l)-Ru(2)-H( 3) Ru( 1)-Si(1)-Ru(2) Ru(1)-Si( 1)-H(5) Rutl)-Si(l)-C(l) C(l)-Si(l)-H(5) Ru(2)-H(3)- Si(1)
2.9761(4) 2.300(1) 2.375(1) 1.73(3) 1.43(3) 1.89(3) 1.50(3) 1.902t4) 2.254(4) 2.199(4) 2.216(4) 2.333(4) 2.320(4) 146.9 94.80(4) 116(1) 50.6(10) 77.76(3) 106(1) 126.1(1)
Ru(2)-Si(l) Ru(2)-Si(2) Ru(2)-H(l) Ru(2)-H( 3) Ru(2)-H( 4) Si(2)-H(4) Si(2)-C(7) Si(Z)-C(ll> Ru(2)-C( 25) Ru(2)-C(26) Ru(2)-C(27) Ru(2)-C(28) Ru(2)-C(29)
2.438(1) 2.675(1) 1.76(3) 1.64(3) 1.64(3) 1.77(3) 1.951(4) 1.944(4) 2.2 16(4) 2.178(4) 2.182(4) 2.256(4) 2.280(4)
CP(~)-RU(~)-RU( 1) Si(l)-Ru(2)-Si(2) H(3)-Ru( 2)-H(4) Si(2)-Ru(2)-H(4) Rut 1)-Si(2)-Ru( 2) Rut 1)-Si(21- C(7) Rutl)-Si(2)-C(ll) C(7)-Sit2)-C(ll) Ru(2)-H(4)-Si(2)
134.3 84.50(3) 75(1) 39(1) 71.94(3) 120.0(1) 118.9(3) 109.7(2) 95(1) 103(2) 87(1) a CP(1) and CP(2) are the centroids of the CsMes ligands.
Ru(2)-Si(2) (2.365(3)A) and are consistent with a RuSi bond with a 2e-3c interaction. Plausible reaction paths are shown in Scheme 2. These involve a direct Si-C(Et) activation by way of oxidative addition (path A) or an activation of the C-H bond a t the ,&position of the coordinated diethylsilane (path B). Coordination of diethylsilane and liberation of dihydrogen can be expected to yield the q2:q2-silane species A’ (path A) or A” (path B) by way of q2-silane intermediate A. In the intermediate A’, diethylsilane is coordinated to both ruthenium centers through both
J
CP1
Figure 10. (A) View of the Ru~Si2core of 7b along the Ru-Ru axis. (B)Another view of the Ru2Si2 core, showing the bent form of the Cp’ centroids. Si-H and Si-C(ethy1) o bonds while the silane is coordinated to the rutheniums through Si-H and C-H bonds in A”. Cleavage of the Si-C(ethy1) bond in A’ as
3864 Organometallics, Vol. 14, No. 8,1995
Takao et al.
Table 4. Selected Bond Lengths (A)and Angles (deg) for 7a‘
c9
C28
v C16
LJ
Ru( 1)-Ru( 2) Ru( 1)-Si( 1) Ru( 1)-Si( 2) Ru( 1)-H(2) Si(1)-H( 1) Si(1)-C( 1) Ru( 1)-C( 11) Ru( 1)-C( 12) R~(l)-C(13) Ru( 1)-C( 14) Ru( 1)-C( 15) CP(l)-Ru(l)-Ru(2) Si(l)-Ru(l)-Si(2) Ru(l)-Si(l)-Ru(2) Ru(l)-Si(l)-H(l) Ru( l)-Si(l)-C( 1) C(l)-Si(l)-H( 1)
2.977(1) 2.4 14(4) 2.680(3) 1.79 1.47 1.88(1) 2.28(1) 2.28(1) 2.22(1) 2.15(1) 2.18(1) 140.5 85.2(1) 77.9(1) 104.6 124.5(5) 88.7
Ru(2)-Si(l) Ru(2 1- Si(2) Ru(2)-H(2) Si(2)-C(3) Si(2)-C(7) Ru(2)-C(21) Ru(2)-C(22) Ru( 2)-C( 23) Ru( 2)-C( 24) R~(2)-C(25) C P ( ~ ) - R U ( ~ ) - R U1) ( Si(1)-Ru(2)- Si(2) Ru(l)-Si(2)-Ru(2) Ru(l)--Si(2)-C(3) Ru(l)-Si(2)-C(7) C(3)-si(2)-C(7)
2.322(3) 2.365(3) 1.72 1.94(1) 1.94(1) 2.30(1) 2.23(1) 2.23(1) 2.26(1) 2.3 1(1) 149.8 95.0( 1) 71.02(9) 111.7(4) 120.4(4) 109.6(6)
C30
Figure 11. Molecular structure of [Cp’Ru12(u-q2-HSitBu2)(,u-q2-HSiEtH)(u-H)(H) (7a),with thermal ellipsoids at the 30% probability level. a result of Si-C oxidative addition leads to the formation of B, which should undergo elimination of the ethyl group directly bound to ruthenium to generate 7a together with ethylene. On the other hand, oxidative addition of a terminal C-H bond of the diethylsilane ligand in A” followed by the /3-Si elimination and deinsertion of ethylene from the resulting (P-silylethy1)ruthenium species C also can yield 7a. Although formation of ethylene was expected in both reaction paths, we could not obtain definitive spectroscopic evidence for ethylene formation. However, the occurrence of important elementary steps, i.e. Si-C bond c l e a ~ a g e ,intramolecular ~~?~~ a-C -H bond activation of the ligand,31 and @-Sie l i m i n a t i ~ n are , ~ ~supported on the basis of previous results. Although predominant cleavage of the Si-H bond over the Si-C(alky1) bond by mononuclear late-transition metal complexes has been proved both experimentally29*30 and t h e ~ r e t i c a l l ySi-C(ethy1) ,~~ bond cleavage exclusively takes place in the reaction of dinuclear complex 4 with diethylsilane. This result strongly suggests that one of the two ruthenium centers in 4 acts as a coordination site and that the second metal takes the role of an activation site. This is a typical example of the selective activation of an organic substrate in cooperation with two metal centers, i.e. bimetallic activation. Another reaction path involves intramolecular ethyl migration from a silyl ligand to a terminal silylene ligand which is generated by way of oxidative addition of the second molecule of Et2SiH2 and subsequent a-H elimination (Scheme 3). Although 1,3-alkyl migration in the mononuclear silyl(sily1ene)-metal complexes has been e ~ t a b l i s h e dsuch , ~ ~ a path including alkyl migration would be excluded in the reaction of 4 with Et2SiH2. The space between two rutheniums in the inter~~
(31) See, for example: (a) Foley, P.; Whitesides, G. M. J . Am. Chem. SOC.1979,101,2732. (b) Ibers, J. A.; DiCosimo, R.; Whitesides, G. M. Organometallics 1982,1, 13. (c) Kletzin, H.; Werner, H. Angew. Chem., Int. Ed. Engl. 1983,22,873. (d) Bennett, M. A.; Huang, T.-A.; Latten, J. L. J . Organomet. Chem. 1984,272,189. (e) Bruno, J. W.; Marks, T. J. J . Am. Chem. SOC.1982,104, 7357. (f) Tulip, T. H.; Thorn, D. L. J . Am. Chem. SOC.1981,103, 2448. (32) Wakatsuki, T.; Yamazaki, H.; Nakano, M.; Yamamoto, Y. J . Chem. SOC.,Chem. Commun. 1991, 703. (33) Sakaki, S.; Ieki, M. J . Am. Chem. SOC.1993, 115, 2373.
a
CP(1) and CP(2) a r e t h e centroids of the C5Me5 ligands.
mediate A is occupied by two silicon ligands, ,u-q2:q2tBu2SiHz and q2-Et2SiH2,and is sterically very crowded. The steric congestion would therefore prevent access of the second molecule of Et2SiH2 to one of the ruthenium centers. As mentioned above, an attempt to react p-silane complex 4 with tB~2SiH2resulted in complete recovery of 4, whereas the reaction with the less bulky Et2SiH2 proceeded on drastic heating. These results imply that there is not enough space between two ruthenium centers of 4 for two additional silane molecules to be accommodated. W D Exchange Reaction. While the p-silyl complex [Cp’Ru@-q2-HSiPh2)]2@-H)(H)(2b)undergoes oxidative addition of the agostic Si-H bonds to the ruthenium centers to yield the bis@-diphenylsilylene) complex [Cp’Ru@-SiPh2)@-H)lz(3)upon heating,8 heating a solution of p-silane complex 4 does not result in formation of a dinuclear mono+-silyl) or mono(psily1ene) complex via an oxidative addition of the agostic Si-H bonds. When complex 4 was heated in C6D6 a t 80 “c,H/D exchange reaction between hydrides and C ~ Dproceeded G slowly. After this heating was maintained for 2 weeks, four signals assignable to hydrides for complexes 4 4 , 4-dl, 4-d2, and 4-d~appeared a t 6 -11.11, -11.38, -11.64, and -11.90, respectively (Figure 12). This result shows the occurrence of oxidative addition of the C-D bond of benzene-&. When the reaction of complex l-d4 with tB~2SiH2 was monitored by lH NMR, a new hydride signal was initially found a t d -11.64. Judging from the chemical shift, initial formation of 4 4 was indicated. Prolonged reaction, however, resulted in a redistribution of deuterium. Namely, four signals of 4-do-4-d3 also were observed as the WD exchange reaction with (34) (a) Pannell, K. H.; Cervantes, J.; Hernandez, C.; Cassias, J.; Vincenti, S. Organometallics 1986,5, 1056. (b) Tobita, H.; Ueno, K.; Ogino, H. Bull. Chem. SOC.Jpn. 1988, 61, 2797. ( c ) Pannell, K. H.; Rozell, J. M., Jr.; Hernandez, C. J . Am. Chem. SOC.1989,111, 4482. (d) Pannell, K. H.; Wang, L.J.; Rozell, J. M. Organometallics 1989,8, 550. (e) Ueno, K.; Tobita, H.; Ogino, H. Chem. Lett. 1990, 369. (f) Haynes, A.; George, M. M.; Haward, M. T.; Poliakoff, M.; Turner, J. J.; Boag, N. M.; Green, M. J . Am. Chem. SOC.1991, 113, 2011. (g) Jones, K. L.; Pannell, K . H. J . Am. Chem. SOC.1993,115,11336. (h) Hernandez, C.; Sharma, H. K.; Pannell, K. H. J . Organomet. Chem. 1993, 462, 259. (i) Pannell, K. H.; Brun, M.-C.; Sharma, H.; Jones, K.; Sharma, S. Organometallics 1994, 13, 1075. (j) Grumbine, S. K.; Tilley, T. D. J . Am. Chem. SOC.1994, 116, 6951. (k) Pestana, D. C.; Koloski, T. S.; Berry, D. H. Organometallics 1994, 13, 4173.
Ruz Complexes Containing a p-Silane Ligand
Organometallics, Vol. 14,No. 8,1995 3865 Scheme 2 ‘BU, H-Si
Oxidative Addition of Si-C Bond
I/ \Y
[Ru]-H-[Ru]
7
I\ /I H-Si-CH2Me I\
/
Path A
A
4
/
7a
Oxidative Addition of C-HBond ___)
([Ru] = Cp’Ru)
A”
C
Scheme 3 %ut
Et2SiH2
4-A*
Et2SiH2
H2
,s,i
H-Si-Et
I\
Et H
Et
H
/,
Et
\
‘Bu2
/
‘BU,
SiEt3 H Et
C& proceeded. HfD exchange between 4-d4 and tBu2SiH2 was confirmed, and it was proved t o proceed more rapidly than that of C6Ds (75% conversiod80 “C/ 24 h).
Moreover, X-ray diffraction studies of [Cp’Ru(CO)lz@v2:q2-H2SitBu2)(5) confirmed the p-v2:v2coordination of tBu2SiH2. Steric repulsion suppresses the coordination of the second molecule of tBu2SiH~.This was confirmed by the reaction of 4 with less bulky silanes, such as PhSiH3 or Conclusion EtzSiHz, which yield mixed-bridge bis$-silyl) complexes The p-silane complex [Cp’Ru$-H)12$-v2:v2-H2SitBuz) 7b and 7a,respectively. These results demonstrate that p-silane complex 4 is best regarded as an intermediate (4) was obtained by the reaction of Cp’Ru$-HhRuCp’ in the formation of bis$-silyl) complexes. (1)with di-tert-butylsilane. A unique p-v2:v2coordinaAlthough the corresponding mono$-silylene) complex tion of tBu2SiHz was confirmed on the basis of lH, 13C, and 29SiNMR and IR spectra. Among these spectral [Cp‘Ru$-H)12$-SitBu2) has never been obtained, an data, relatively low coupling constants between Si and oxidative addition of one of the two v2-Si-H bonds of 4 took place in the presence of PhSiHs and EtzSiH2. Also, H observable a t low temperature (Js~-H = 75 Hz) strongly indicated the existence of 2e-3c interactions. the intra- and intermolecular HfD exchange reactions
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Takao et al.
Organometallics, Vol. 14,No. 8,1995
Table 5. Crystallographic Data for 5,7a, and 7b
A 1
d h
n
4-d3
4i - w-11.0
-11.4
-11.8
-12.2
(PPM)
Figure 12. 'H NMR spectra of t h e hydride region i n the WD exchange reaction of 4 with benzene-&: (A) 0 h; (B) 2 days; (C) 4 days; (D)11 days; (E) 13 days.
of 4 distinctly indicate the occurrence of the oxidative addition of the r2-Si-H bond of 4. Experimental Section General Procedures. All experiments were carried out under an argon atmosphere. All compounds were treated with Schlenk techniques. Reagent grade toluene was dried over sodium-benzophenone ketyl and stored under an argon atmosphere. Pentane was dried over phosphorus pentoxide and stored under an argon atmosphere. Benzene-d6 and toluene-& were used as received. Diethylsilane and phenylsilane were used as received, and di-tert-butylsilane and ditert-butylsilane-dz were synthesized by the reduction of di-tertbutyldichlorosilane by LiAlH4 or L A D 4 in diethyl ether, respectively. IR spectra were recorded on a JASCO FTLR5000 spectrophotometer. lH and 13C NMR spectra were recorded on JEOL GX-500, JEOL EX-270, and Varian Gemini3000 Fourier transform spectrometers with tetramethylsilane as a internal standard. Variable-temperature lH NMR spectra were recorded on a JEOL GX-500. 29Si NMR spectra were recorded on a JEOL EX-270 with tetramethylsilane as an external standard under proton-decoupled conditions or were irradiated a t a signal of tert-butyl groups under selectivedecoupling conditions. Field-desorption mass spectra wee recorded on a Hitachi GC-MS M80 high-resolution mass spectrometer. Elemental analyses were performed by the Analytical Facility a t the Research Laboratory of Resources Utilization, Tokyo Institute of Technology. The dinuclear ruthenium tetrahydride complex [(r5-CsMes)Ru01-H)*Ru( r5-C5Medl (1) and [(r5-C5Me5)Ru(~-D)4RU(IIS-C5Me5)1 ( l - d d ) were prepared according to previously published method^.^ X-ray Data Collection and Reduction. X-ray-quality crystals of 5, 7a, and 7b were obtained directly from the preparations described below and mounted on gIass fibers. Diffraction experiments were performed on a Rigaku AFC-SR four-circle diffractometer with graphite-monochromated Mo Ka radiation (1= 0.710 69 A) a t 23 "C. The lattice parameters
(a) Crystal Parameters C~OH~OOZR CU ~O ~ SH~~ ~ R U C Z S~ ~~ZH ~ B R U ~ S ~ Z triclinic orthorhombic monoclinic P1 Pna2l P21Ic 11.020(4) 17.064(4) 10.484(1) 17.389(3) 11.396(3) 18.147(3) 8.774(2) 16.782(3) 18.704(3) 93.23(2) 112.70(2) 97.68(1) 87.47(3) 1548.1(8) 3263(2) 3526.6(8) 2 4 4 Z 1.444 1.378 1.366 Dcalcd, g cm-3 23.0 23.0 23.0 temp, "C 10.15 9.26 ,dMo Ka), cm-l 10.18 cryst dimens, 0.4 x 0.4 x 0.1 0.4 x 0.4 x 0.2 0.3 x 0.3 x 0.2 mm (b) Data Collection Rigaku diffractometer Rigaku Rigaku AFC5R AFC5R AFC5R MoKa(i= MoKa(i= Mo Ka (A = radiation 0.710 69 A) 0.710 69 A) 0.710 69 A) graphite monochromator graphite graphite wl20 scan type w12e w/20 55.0 50.0 50.0 20max,deg 16.0 scan speed, 16.0 16.0 deg min-' 3259 8524 refins collected 5776 3259 8098 independent 5465 data 5649 4741 2570 independent data obsd (c) Refinement 0.045 0.031 R 0.031 0.045 0.026 0.033 R W 0.01 0.03 0.01 p factor 363 variables 324 306 3.53 1.58 GOF 3.67 and orientation matrices were obtained and refined from 15 machine-centered reflections with 24.4" < 20 < 25.4" for 5, 19 machine-centered reflections with 19.5" < 28 < 20.5" for 7a, and 20 machine-centered reflections with 19.4" < 20 < 20.6" for 7b. Intensity data were collected using a wI20 scan technique; 3 standard reflections were recorded every 150 reflections. The data for 5, 7a, and 7b were processed using the TEXSAN crystal solution package operating on a IRIS Indigo computer. Neutral atom scattering factors were obtained from the standard sources.35 In the reduction of the data, Lorentdpolarization corrections and empirical adsorption corrections based on azimuthal scans were applied to the data for each structure. Structure Solution and Refinement. The Ru atom positions were determined using direct methods employing the MITHRIL direct-methods routines. In each case the remaining non-hydrogen atoms were located from successive difference Fourier map calculations. In all cases the non-hydrogen atoms were refined anisotropically by using full-matrix leastsquares techniques on F. In the cases of 5 and 7b, the positions of hydrogen atoms bonded to the Ru and silicon atoms were located by sequential difference Fourier synthesis and were refined isotropically. However, the positions of three of the four hydrogen atoms bound to the Ru atoms were not located from the difference Fourier map calculations in the case of 7a. The positions of the one hydrogen atom bridging between two Ru atoms and of the hydrogen atom terminally bound to silicon were located but not refined. Crystal data and results of the analyses are listed in Table 5. Preparation of [(t16-CsMe~)Ru01-H)12~-~2:~2-H~SitBu2) (4). Toluene (20 mL) and Cp'Ru(p-H)rRuCp' (0.470 g, 0.986 mmol) were charged in a reaction flask. After 1.5equiv of Hz(35)International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1975; Vol. 4.
Ruz Complexes Containing a p s i l a n e Ligand SitBu2 (0.29 mL, 1.61 mmol) was added, the solution was stirred for 4 h at 25 "C with vigorous stirring. The color of the solution changed from red to deep purple with slow generation of hydrogen. The solvent and remaining silanes were then evaporated under reduced pressure. The deep purple residual solid was dissolved in 7 mL of toluene, and the product was purified by the use of column chromatography on neutral alumina (Merck Art.No. 1097) with hexanekoluene. Removal of the solvent in uucuo afforded 0.546 g of purple solid (89% yield). 'H NMR (300 MHz, 23 " c , CsD6): 6 1.89 (s,30H, Cp'), 1.11(s, 18H, tBu), -11.12 (br, 4H, RuHRu and RuHSi). 'H NMR (500 MHz, -120 "C, 1:5 toluene-d$rHF-d& 6 1.90 (s, 30H, Cp'), 0.78 (s, 18H, t B ~ )-6.15 , (s,2H, J s ~ - H = 75 Hz, RuHSi), -16.63 (s, 2H, RuHRu). 13C NMR (75 MHz, 23 "C, C6D6): 6 85.7 (S,C5Me5), 32.3 (9, Jc-H = 124.9 HZ, cMe3), 24.1 (s, CMes), 12.8 (9, Jc-H = 126.5 Hz, CsMe5). 29Si NMR (99 ~ 34.2 Hz). IR MHz, 23 "C, toluene-&): 6 75.5 (quintet, J s 1 -= (KBr, cm-'): 2974, 2952, 2884, 2854, 1790 br (v(Ru-H-Si)), 1468, 1377, 1050 (d(H-Si-H)), 1029, 816, 600. Anal. Calcd for C28H52Ru2Si: C, 54.36; H, 8.47. Found: C, 54.09; H, 8.57.
Preparation of [(q5-C&le5)Ru@-D)Iz (lr-q2:q2-D2SitBu2) (4d4). Toluene (10 mL) and Cp'Ru(p-D)rRuCp' (0.061 g, 0.13 mmol) were charged in a reaction flask. After 2.0 equiv of D2SitBuz (0.05 mL, 0.25 mmol) was added, the solution was stirred for 4 h a t 25 "C with vigorous stirring. The solvent and remaining silanes were then evaporated under reduced pressure. The deep purple residual solid was dissolved in 7 mL of hexane, and the product was purified by the use of column chromatography on neutral alumina (Merck Art. No. 1097) with hexaneltoluene. Removal of the solvent in uucuo afforded 0.047 g of purple solid (60% yield). 'H NMR (300 MHz, 23 " c , C6Ds): 6 1.89 (s,30H, cp'), 1.11(s, 18H, 'Bu). IR (KBr, cm-l): 2960, 2920, 2854, 1468, 1375, 1280 br ( ~ ( R u D-Si)), 1029, 816, 760 (G(D-Si-D)), 601. Reaction of (q5-C&le5)Ru@-D)4Ru(q5-CsMes) ( 1 4 4 ) with Di-tert-butylsilane. Benzene-& (0.3 mL) and Cp'Ru(p-D)rRuCp' (0.012 g, 0.025 mmol) were charged in an NMR tube. Four equivalents of tBu2SiH2 (0.019 mL, 0.097 mmol) was added; the reaction was then monitored by the use of 'H NMR a t room temperature. While the reaction rate was extremely slow when compared t o the reaction carried in a Schlenk tube with vigorous stirring, all of 1-d4 was converted in 12 h. In the lH NMR measured after 15 min, a small hydride resonance was observed only a t 6 -11.64 (conversion ca. 10%); four hydride signals assignable to 4, 4-d1,4-dz, and 4-d3 were observed after 12 h (conversion 100%). 'H NMR (300 MHz, 23 "c, C&): 6 1.89 (5, 30H, cp'), 1.11(S, 18H, 'BU), -11.12 (br, 4), -11.38 (br, 4-d1),-11.64 (br, 4-d2),-11.90 (br, 4-d3). Intensity ratio of the hydride region t o the Cp' signal is ca. 2.OH, and the ratio among 4, 4-dl, 4-dz, 4-d3, and 4-d4 was estimated a t about 2:7:9:3:4. The reaction of 1 with tBu~SiD2 gave a similar result, though the ratio was slightly changed.
Organometallics, Vol. 14,No. 8,1995 3867 (CO), 96.0 (CsMes),31.3 (CMe3), 28.1 (CMed, 10.3 (Cae5); 6, 6 210.4 (CO), 205.7 (CO), 95.63 (CsMed, 95.55 (CsMes),32.0 (CMe3), 31.7 (CMe3), 27.0 (CMed, 26.8 (CMe31, 10.6 ( C a e s ) , 9.8 ( C a e 5 ) . 29siNMR (54 MHz, 23 "c, C6D6): 5 , 6 186.2 (t, J s i - ~= 22.4 Hz); 6 , 6 168.7 (dd, J s i - ~= 31.6,7.9 Hz). IR (KBr, cm-I): 5 and 6,2976,2894,2854,1928,1905,1869,1479,1379, 1027,818. Anal. Calcd for C ~ O H ~ O O Z RC, U53.55; ~ S ~ : H, 7.49. Found: C, 52.69; H, 7.45 (5 and 6).
Preparation of [(q5-C~e~)Ru12~-qz-HSitBu~)@-qz-HSiEtH)@-H)(H)(7a). Benzene-& and [Cp'Ru01-H)I201-q2:q2-H2SitBuz)(4;0.031 g, 0.049 mmol) were charged in an NMR tube. After 20 equiv of diethylsilane (0.13 mL, 1.01 mmol) was added, the NMR tube was sealed. After the solution was heated in a oil bath a t 100 "C for 2 h, the color changed from deep purple to red. The solvent and remaining silanes were then evaporated under reduced pressure in a flask. The orange residual oil was dissolved in 1 mL of pentane, and the product was purified by the use of column chromatography on neutral alumina (Merck Art. No. 1097) with hexane. Removal of the solvent in uucuo afforded 0.030 g of the orange solid of the mixture of 7a together with [Cp'Ru@-y2-HSiEt)12(p-H)(H)(2a)in the ratio of 10:1(82%yield based on 'H NMR). Complex 7a can be isolated from cold pentane as a orange single crystal suitable for an X-ray diffraction study. A minor product was identified as 2a by comparing the 'H NMR chemical shift with that of an authentic sample alternatively synthesized. 'H NMR (500 MHz, 60 "C, toluene-&): 6 5.66 (br, l H , JSI-H= 160 Hz, S Z ) , 1.87 (s, 30H, Cp'), 1.50 (m, 5H, Et), 1.28 (s, 9H, tBu), 1.25 (s, 9H, tBu), -12.83 (br, 2H, RuH), -15.50 (br, 2H, RuH). 'H NMR (-90 "C): 6 5.64 (br, l H , SiH), 1.94 (s, 15H, Cp'), 1.63 (s, 15H, Cp'), 1.6 -1.0 (m, 5H, Et), 1.61.0 (m, 18H, tBu), -12.32 (s, l H , RuH), -13.26 (s, l H , RuH), -14.29 (s,l H , RuH), -16.67 (s, l H , RuH). 13C(1H}NMR (76 MHz, 23 " c , C6Ds): 6 93.3 (CsMe5),32.3 (cMe3), 32.4 (CMe3), 25.9 (CMe3), 24.9 (CMe3), 15.0 (-CH2CH3), 14.0 (-CHZCH~), 12.4 (Cae5). IR (KBr, cm-I): 2964,2906,2850,2062 m (v(RuH), 2022 s (v(Si-H)),1835 br (v(Ru-H-SitBu2)),1659 br ( ~ ( R u H-SiEtH)), 1475, 1379, 1071, 1027, 812, 571. Anal. Calcd for C30H58Ru2Si2: C, 53.22; H, 8.63. Found: C, 53.02; H, 8.22. FD-MASS: mle 678. The field desorption mass spectrum was measured, and the intensities of the obtained isotopic peaks for C30H58R~2Si2 agreed with the calculated values within experimental error.
Preparation of [(q5-C~Me~)Rulz(p-q2-HSitBuz)(p-q2HSiPhH)@-H)(H) (7b). Toluene (10 mL) and [Cp'Ru(u-H)l~(p-q2:q2-HzSitBuz) (4; 0.074 g, 0.12 mmol) were charged in a
reaction flask. After 5 equiv of phenylsilane (0.075 mL, 0.61 mmol) was added, the reaction solution was stirred for 2 h a t room temperature. The color of the solution changed from deep purple to bright orange. The solvent and remaining silanes were then evaporated under reduced pressure. The orange residual oil was dissolved in 5 mL of pentane, and the Preparation of [(q5-C&le5)Ru(C0)12@-qz:q2-HzSitBu~)product was purifed by the use of column chromatography on neutral alumina (Merck Art.No. 1097) with hexane. Removal (5) and [(q5-C~e5)Ru(C0)1~(-q2-HSitBu~)(H) (6). Toluene of the solvent in vacuo afforded 0.059 g of the orange solid of (4;0.081 g, 0.13 (10 mL) and [Cp'Ru(p-H)]2(p-q2:q2-H2SitBuz) the mixture of 7b (68% yield). 'H NMR (500 MHz, 20 "C, mmol) were charged in a reaction flask under 1atm of carbon = 172 toluene-&): 6 8.2-7.1 (m, 5H, Ph), 6.29 (s, l H , Js~-H monoxide. After the solution was stirred for 12 h a t 23 "C, Hz, S a ) , 1.87 (6, 30H, Cp'), 1.24 (s, 9H, t B ~ ) 1.04 , (s, 9H, the color changed from deep purple to light orange. Removal Bu), -12.31 (br, 2H, RuH), -15.35 (br, 2H, RuH). 'H NMR of the solvent under reduced pressure afforded a yellow solid (-90" C): 6 8.2-7.1 (m, 5H, Ph), 6.37 (br, l H , S a ) , 1.93 (s, mixture of 5 and 6 including 4% of [Cp'Ru(CO)(p-C0)12as a 15H, Cp'), 1.66 (s, 15H, Cp'), 1.5-1.0 (m, 18H, tBu), -11.64 byproduct. Complexes 5 and 6 were extracted from the (s, lH, Js~-H = 26 Hz, RuHSi), -12.84 (s, l H , RuH or RuHRu), mixture by filtration with 5 mL of pentane three times. -14.00 (s, l H , Js,-H = 49 Hz,RuHSi), -16.46 (s, l H , RuH or Removal of the solvent in uucuo afforded 0.066 g of the yellow RuHRu). I3Ci1H}NMR (76 MHz, 23 "C, C6D6): 6 144.6 (Ph solid mixture of 5 and 6 in the ratio of 1:1.2 (76%yield). Only ipso), 136.8 (Ph), 127.7 (Ph), 93.5 (CsMes), 32.6 (CMe3), 32.1 5 can be isolated from cold pentane as a yellow single crystal (CMe3),26.0 (CMe3),25.0 (CMe3),12.4 (C5Me5). IR (KBr, cm-l): suitable for X-ray diffraction study, but it came to equilibrium 3062, 3048, 2958, 2900, 2850, 2054 (v(Ru-H)), 2036 (v(Siwithin few hours when it was dissolved in benzene-&. 'H H)), 1813br (v(Ru-H-Si)), 1613 br (v(Ru-H-Si)), 1475, 1427, NMR (300 MHz, 23 "C, CsD6): 5, 6 1.89 (s, 30H, Cp'), 1.26 (s, 1379, 1029,880, 700. Anal. Calcd for C34H58R~2Si2:C, 56.32; 18H, tBu), -13.60 (s, 2H, J s ~ - H = 24 Hz, RuHSi); 6, 6 1.98 (s, H, 8.06. Found: C, 56.04; H, 8.19. 15H, Cp'), 1.73 (s, 15H, Cp'), 1.42 (s, 9H, tBu), 1.41 (s, 9H, W D Exchange Reaction of [Cp'Ru01-H)12@-q2:q2-H2Sitt B ~ )-11.79 , (s, l H , J s l - ~= 36 Hz, RuHSi), -14.40 (s, l H , BuZ)(4) with Benzene-de. Benzene-& (0.3 mL) and t(q5-C5RuHRu). 13C('H} NMR (69 MHz, 23 "C, C6D6): 5, d 211.1
'-
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Organometallics, Vol. 14, No. 8,1995
Me5)Ru(~-H)]2(~-y2:y2-H~SitBu~) (4;0.015 g, 0.024 mmol) were charged in an NMR tube; the tube was then sealed. When the mixture was heated in an oil bath a t 80 "C for days, new peaks of hydride signals assignable t o those for 4 4 , 4 d z , and 4-d3appeared, each consecutively shifted 0.26 ppm upfield from that of 4. Deuterium abstraction gradually proceeded, and those peaks finally disappeared after 2 weeks while the signal for Cp' groups did not show any observable changes during the reaction.
H/D Exchange Reaction of 4-d4 with Di-tert-butylsilane. Di-tert-butylsilane (0.038 mL, 0.21 mmol) and [(y5-C5M ~ ~ ) R u ( ~ - D ) ~ ] ( ~ - ~ ~ :(4-d4; ~ ~ - D0.013 ~ S ~g,~ 0.021 B U Z mmol) ) were dissolved in benzene-& (0.3 mL). After the solution was charged in an NMR tube, the tube was sealed. Whereas the WD exchange reaction did not proceed a t room temperature, the signals for hydrides of 4, 4-dl, 4-dz, and 443 appeared upon heating in a n oil bath a t 80 "C for 24 h. The total intensity of those signals was ea. 3H to 30H of the Cp' signal at that time (conversion 75%), and a decrease in the intensity of the Si-H signal of tBu&iHz was also observed. Prolonged heating resulted in a disappearance of both the Si-H signal
for tBu2SiH2 and that for Ru-H. Deuterium distribution between C6D6 occurred simultaneously.
Acknowledgment. This research was supported by fellowships of the Japan Society for the Promotion of Science for Japanese Junior Scientists and by a Grantin-Aid for Scientific Research on Priority Area (Nos. 05225210 and 05236104)from the Ministry of Eduation, Science, and Culture. We thank Kanto Chemical Co., Inc., for generous gifts of pentamethylcyclopentadiene and several kinds of silanes. Supporting Information Available: Text giving details of the data collection and reduction and the structure solution and refinement and tables of the crystal data and the data collection and refinement parameters, positional parameters, anisotropic thermal parameters, bond lengths and angles, and special contacts (45 pages). Ordering information is given on any current masthead page. OM940859N
