A Photochemical Route to Heterometallic Complexes. Synthesis and

A Photochemical Route to Heterometallic Complexes. Synthesis ... Organometallics 2008 27 (8), 1758-1764 ... Inorganic Chemistry 1997 36 (27), 6440-644...
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5598

A Photochemical Route to Heterometallic Complexes. Synthesis and Structural Characterization of Di- and Trinuclear Complexes Having a Molybdenocene or Tungstenocene Unit Takayuki Nakajima,' Takaya Mise,$ Isao Shimizu,? and Yasuo Wakatsuki*s$ The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan, and Department of Applied Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Ookubo, Shinjuku-ku, Tokyo 169, Japan Received July 6, 1995@ Irradiation of a mixture of tungstenocene or molybdenocene dihydride and a metal-metalbonded dimeric complex has been found to be a convenient route to homo- and heterometallic complexes. The photoreactions of (q5-C5H5)2M1H2with [(q5-C5H5)Mz(CO)312(M1, M2 = W, Mo) in DME afford in good yields the bimetallic complexes (q5-C5H5)(CO)M1CU,aq5-C5H4)M2(C0)2(q5-C5H5)with a M1-M2 bond. (la,M1 = W,M2 = Mo; lb,M1 = Mo, M2 = W;IC, M1 = M2 = W;Id,M' = M2 = Mo). By use of [(q5-C5R5)Ni(C0)12as the dimer part, the (2a,M = W,R = H; 2b,M = W, heterobimetallic hydrides (q5-C5H5)2MCU-H)CU-CO)Ni(C5R5) R = Me; 2c,M = Mo, R = H, 2d,M = Mo, R = Me) were obtained, where the two metallocene cyclopentadienyl rings remain intact and the metal-metal bond is bridged by CO and hydride. Similar photolysis of a mixture of (q5-C5H5)2MH2 and [(q5-C5H5)Ru(C0)212has afforded two trimetallic complexes: (q5-C5H5)CU,u-q5-C5H4)MCU-C0)2Ru(q5-C5H5)Ru(q5-C5H5)(CO)H (3a,M = W;3b,M = Mo), where the Ru-Ru bond still exists with a new M-Ru bond and one bridging @,a-q5-C5H4)ring between M and the other Ru, and @,o-q5-C5H4)2MHz[(q5-C5H5)Ru(CO)12(4a,M = W,4b,M = Mo), in which both of the cyclopentadienyl rings of the metallocene are metalated with Ru. The crystal and molecular structures of la,2d,3a,and 4a have been determined by single-crystal X-ray diffraction analysis. In recent years heterometallic complexes have attracted considerable interest as the potential sites for cooperative reactions effected by different sorts of neighboring metals. A large number of heteronuclear metal-metal-bonded complexes have been known, and many synthetic approaches for them have been summarized and classified in the reviews by Roberts and Geoffroyl and Stephan.2 Though synthetic methods for heterobimetallic complexes and triangular heterotrimetallic complexes are most extensively studied, that for open-chain framed heterotrimetallic complexes are much fewer with major rational synthetic methodologies being (1)substitution of the halide anions (X-) in ML,X2 by an anionic metal complex or (2) ligand bridge-assisted substitution reacti0ns.l Photoactivation of CpzWH2 (Cp = q5-C5H5)has been reported to generate active tungstenocene [Cp2Wl species which can oxidatively add the C-H bond of solvent molecules (RH) to form CP~W(R)(H).~ If a similar oxidative addition of the metal-metal bond of an appropriatee L,M'-ML, complex can take place across the tungstenocene or molybdenocene, heterotrimetallic ~~

+

Waseda University.

* RIKEN.

Abstract published in Advance ACS Abstracts, November 1, 1995. (1)Roberts, D. A.; Geoffroy, G. L. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, G., Abel, E. W., Eds.; Pergamon: New York, 1982;Vol. 6. (2)Stephan, D. W. Coord. Chem. Rev. 1989,95,41. (3) (a)Green, M. L. H. Pure Appl. Chem., 1978,50,27.(b)Giannotti, C.;Green, M. L. H. J . Chem. Soc., Chem. Commun. 1972,1114. (c) Berry, M.;Elmitt, K.; Green, M. L. H. J . Chem. Soc., Dalton Trans. 1979,1950. @

complexes of the form (LnM)-(Cp2M)-(ML,) (M = W, Mo) may be expected. Alternatively, photolysis of the L,M-ML, molecule might cleave the metal-metal bond to form a metal radical species4which could attack the metallocene dihydride to give a heterometallic complex. In any event, irradiation of a mixture of Cp2MH2 (M = W, Mo) and a L,M-ML, type complex seemed to be a reasonable system to produce new heterometallic compounds. To examine this hypothesis we carried out several photoreactions of molybdenocene and tungstenocene dihydrides with dimeric metal complexes. Although some of the reactions ended up with the formation of bimetallic complexes, the present reaction system has been found to be useful in introducing a molybdenocene or tungstenocene unit into di- and trimetallic compounds. To the best of our knowledge, complexes possessing heteronuclear bonds between the molybdenocene or tungstenocene unit and other transition metals have only one p r e ~ e d e n t . ~ Results and Discussion W-Mo, W-W, and Mo-Mo Complexes. An equimolar amount of Cp2WH2 and [CpMo(CO)slnin 1,2dimethoxyethane (DME) was irradiated with a highpressure mercury lamp at room temperature until most (4)(a) Wrighton, M.S.; Ginley, D. S. J . A m . Chem. SOC.1975,97, 2065. (b) Wrighton, M.S.; Ginley, D. S.J . A m . Chem. SOC.1975,97, 4246. (5)Hoxmeier, R.; Deubzer, B.; Kaesz, H. D. J . A m . Chem. SOC.1971, 93,536.

0276-7333/95/2314-5598$09.00/00 1995 American Chemical Society

A Photochemical Route to Heterometallic Complexes

of the tungstenocene dihydride was consumed (ca. 35 h), which was easily monitored by ‘H NMR spectra. Chromatography on an alumina column of the crude mixture gave dark red crystals which were not the expected trimetallic complex but turned out to be a heterobimetallic complex of the formula Cp(C5Hd)WMo(C0)zCp (la) in 43% yield. The other half of the dimolybdenum unit obviously took up hydrogen since CpMo(C0)3H was detected in a reasonable amount when the reaction mixture was dried up and subjected t o NMR measurement. Complex l a is air-stable in the crystalline form but begins to decompose gradually when kept in solution for a few days under argon. The lH NMR spectrum of l a shows two singlets with an integrated ratio equal to 10 protons, indicating the presence of two different Cp rings. The third cyclopentadienyl unit exhibits four protons which appear as four different multiplets. Subsequent characterization of this complex by a single-crystal X-ray diffraction analysis revealed the solid state structure shown in Figure 1. Crystal and data collection parameters are provided in Table 1,and selected bond distances and angles are tabulated in Table 2. One of the metallocene Cp rings has been metalated by molybdenum, and the two metals are directly bonded. To attain an 18-electron configuration, this metal-metal bond may be regarded as a dative bond from metallocene (W) to Mo. The W-Mo bond length of 3.069(2) is a little, but significantly, shorter than the Mo-Mo bond (3.089(1) in the known analog (ldh6 A similar trend has been observed in the metal-metal bond lengths in [CpM(C0)312: 3.222(1) A for M = W and 3.235(1) A for M = M o . ~ In the converse way, photolysis of a mixture of Cp2MoH2 and [CpW(C0)312for 12 h gave the corresponding heterobimetallic complex Cp(CsH4)Mo-W(CO)zCp (lb) in 42% yield. The reaction could also be applied t o the syntheses of homobimetallic complexes of W and Mo: similar photoreactions of CpzMHz and [CpM(C0)312in DME afforded Cp(C5HdM-M(C0)2Cp (IC,M = W, 43%; Id, M = Mo, 56% yield). In all of these reactions, concomitant formation of the metal hydride CpM(C013H was confirmed by NMR spectra. The overall reaction may then be expressed as shown in eq 1.

A

A)

l a : M’-W, M 2=Mo l b : M’=Mo, M ‘=W 1C ; M’-W, M ‘-W l d : Ml-Mo, M 2=Mo

The homometallic complex Id has been prepared previously by two quite different methods, i.e. from Moz(OzCMe)4 and Na(C5H5)/C0,6and also by the reaction of C5H4N2 with C~(CO)~MO=MO(CO)~C~.~ The very low terminal-carbonyl absorption of Id a t 1765 cm-l (mulls) has been assigned by Green et a1.6to one of the (6) Bashkin, J.;Green, M. L. H.; Poveda, M. L.; Prout, K. J . Chem. SOC., Dalton Trans. 1982,2485. (7)Adams, R. D.; Collins, D. M.; Cotton, F. A. Znorg. Chem. 1974, 13, 1086.

(8)Herrmann, W. A.; Kriechbaum, G.; Bauer, C.; Guggolz, E.; Ziegler, M. L. Angew. Chem., Int. E d . Engl. 1981,815.

Organometallics, Vol. 14, No. 12, 1995 5599

Figure 1. View of Cp(C&)(CO)W-Mo(CO)2Cp (la)showing the atom-labeling scheme. CO groups on M2 and has been attributed to the strong dative bond from the molybdenocene unit (Ml), which causes accumulation of negative charge on M2. In THF solutions, the present complexes exhibit three carbonyl stretching bands (la, 1961, 1882,1799; lb, 1971,1880, 1790; IC,1962,1876,1788; Id, 1970,1887,1803 cm-l). Following the argument of Green et al., the two lowfrequency bands may be assigned symmetric and asymmetric coupling of the two CO vibrations at M2. Comparing the bands of l a with Id, and also l b with IC, we see the donation from tungstenocene unit is slightly stronger than that from molybdenocene. W-Ni and Mo-Ni Complexes. The nickel dimer [(q5-C5Rs)Ni(C0)12(R = H, Me) reacted successfully under the photolysis conditions with the metallocene dihydrides. Workup on an alumina column gave darkred crystals of heterobimetallic complexes of the formula Cp2MH-Ni(C0)(q5-C5R5)(2a, M = W, R = H, 56%; 2b, M = W, R = Me, 23%; 2c, M = Mo, R = H, 35%;2d, M = Mo, R = Me, 25% yield). Proton NMR spectra of these complexes indicated that the two metallocene Cp rings remain intact and magnetically equivalent. A peak with an intensity equivalent t o one hydrogen was observed at 6 -5.83 (2a), -6.47 (2b), -6.43 (2c), and -5.57 (2d) ppm. These complexes have a single carbonyl stretching absorption at the bridging carbonyl region, 1718-1755 cm-l. The crystal of 2d has been characterized by X-ray analysis. The molecular structure with atom-labeling scheme is shown in Figure 2, and selected bond lengths and angles are listed in Table 3. The Mo-Ni distance is 2.657(1)A indicating the presence of the metal-metal bond. For comparison, the Ni-Ni and Mo-Mo distances in [CpNi(CO)129and [C~Mo(C0)312~ are 2.3627(9) and 3.235(1)A,respectively. The hydride in complex 2d could not be located from Fourier maps but must be present at the vacant site bridging the two metals. The Cp ring on Ni (C(21)-C(25)) is not perpendicular to the Mo-Ni vector but tilted, the angle between the Mo-Ni axis and the Cp(Ni) plane being 75”, and opens toward the bridging CO. Still there is enough space available for the hydride bridge opposite t o the bridging CO. The metallocene wedge opens right to the direction of Ni. Reflecting the larger size of the molybdenum atom, the Mo-C(0) distance (2.226(4)A)is much longer than the corresponding Ni-C(0) distance of 1.759(5) A. The C-0 vector is almost perpendicular to the Mo-Ni axis. In accord with this structure, the hydride lH NMR resonances of 2a,b exhibit satellites due to la3W(IJw-HI (9)Byers, L. R.; Dahl, L. F. Inorg. Chem. 1980,19, 680.

5600 Organometallics, Vol. 14,No. 12, 1995

Nakajima et al.

Table 1. Crystallographic Data for Complexes la, 2d, 3a, and 4a fw cryst system space group

a,A b, A

A A deg C,

v, A3

z

crvst size. mm

la (C18H1403MoW) 558.1 monoclinic P21h 12.223(2) 15.229(2) 8.613(3) 92.27(2) 1605 4 0.54 x 0.23 x 0.11

2d (CzlHz&MoNi) 449.1 monoclinic P21In 15.026(2) 14.097(4) 9.085(2) 101.96(1) 1880 4 0.58 x 0.29 x 0.07

3a (C23H2003RuzW) 730.5 monoclinic P21lC 15.126(3) 11.956(2) 12.202(6) 112.78(2) 2039 4 0.29 x 0.14 x 0.07

4.0-55.0 f19,+18,+11 3210 3.58 3.60

4.0-55.0 rt19,+15,+25 3831 3.85 4.27

4a (CzzHzoO2RuzW.O.5C7Hs)

748.5 monoclinic P211c 9.848(3) 10.993(3) 21.658(6) 98.06(3) 2321 4 0.43 x 0.22 x 0.07

dcalc,

radiation u. cm-l

#

I

26' scan range, deg 4.0-136.0 f14,+18,+10 data collcd (h,K,Z) no. of unique rflns (F,, 2 4a(F,)) 2638 7.91 R,% 8.41 Rw, %

4.0-55.0 f12,+14,+28 3878 5.12 5.79

Table 2. Selected Bond Distances (A)and Angles (deg) for l a W-MO W-C(l1) W-C(l2) W-C(l3) W-C(l4) W-C(15) C(ll)-C(12) C(13)-C(14) C(15)-C(ll) Mo-C(2) Mo-C( 11) Mo-C(22) Mo-C(24) C(1)-O( 1) C(2)-0(2) Mo-W-C(l1) C(ll)-MO-W W-Mo-C(2) C(ll)-C(l2)-C(l3) C(13)-C(14)-C(15) C(X)-C(ll)-C(12)

Bond Disitances W-C(l) 3.069(2) W-C(16) 2.222(17) W-C(17) 2.263(21) W-C(18) 2.313(22) W-C(l9) 2.352(21) W-C(20) 2.240(18) C(12)-C(13) 1.481(27) C(14)-C(15) 1.373(31) 1.472(28) Mo-C(3) 1.918(21) Mo-C(21) 2.106(18) Mo-C(23) 2.338(26) 2.371(24) Mo-C(25) 1.150(3) 1.180(26) C(3)-0(3) Bond Angles 43.3(5) W-C(ll)-Mo 46.4(5) Mo- W-C(1) 104.9(6) W-Mo-C(3) 111.4(18) C(12)-C(13)-C(14) 109.1(19) C(l4)-C(l5)-C(ll) 101.2(15) Cp-W-Cp"

2.008(25) 2.331(20) 2.310(22) 2.357(24) 2.317(21) 2.306(20) 1.400(29) 1.433(28) 1.934(25) 2.406(22) 2.347(24) 2.363(27) 1.177(30) 90.3(5) 94.9(6) 75.7(6) 108.2(19) 109.8(17) 148.1(10)

Angle between the two perpendicular lines from W to the Cp rings.

= 73.7 (2a), 76.8 (2b) Hz). If the 18-electron rule is to be applied for each metal center, the structure may be regarded as resonance of two extremes: one with a MoNi o bond and the hydride bonded solely to Ni; the other with a Mo-Ni dative bond and the hydride bound only to Mo. The reaction stoichiometry and the structure of the bimetallic complex may be reasonably assumed as indicated in eq 2. The nickel moiety must have attacked

2a: M-W, R=n 2b: M=W. R-Me 2C: M-Mo. R-H 26: M=Mo. R-Me

the metallocene dihydride before the latter lost dihydrogen on photolysis. We were unable to detect a (r5C5R5)Ni(CO)Hspecies, but it is not unexpected since (r5CSRs)Ni(CO)H must be very unstable and, to our knowledge, no report on its isolation has appeared.

C

Figure 2. View of CpzMoH-Ni(CO)(C5Me5) (2d)showing the atom-labeling scheme. Table 3. Selected Bond Distances (A)and Angles (deg) for 2d Mo-Ni Mo-C(l1) Mo-C( 12) Mo-C(l3) Mo-C(l4) Mo-C(l5) Ni- C(1) Ni-C(22) Ni-C(24) C(ll)-C(12) C(12)-C(13) C(13)-C(14) C(14)-C(15) C(15)-C(ll) C(21)-C(22) C(23)-C(24) C(25)-C(21)

Bond Distances 2.657(1) Mo-C(l) 2.291(7) Mo-C(l6) 2.290(10) Mo-C(17) 2.280(7) Mo-C(18) 2.296(6) Mo-C(l9) 2.299(6) Mo-C(20) 1.759(5) Ni-C(21) 2.132(5) Ni-C(23) 2.193(5) Ni-C(25) 1.360(14) C(16)-C(17) 1.357(14) C(17)-C(18) 1.379(13) C(18)-C(19) 1.361(10) C(19)-C(20) 1.389(11) C(20)-C(16) 1.424(7) C(22)-C(23) 1.423(7) C(24)-C(25) C(l)-O 1.424(7)

Mo-Ni-CU) C(1)-Mo-Ni Mo-C(l)-O Mo-Ni-C(21) Mo-Ni-C(22) Mo-Ni-C(23) Mo-Ni-C(24) Mo-Ni-C(25)

Bond Angles 56.2(2) Ni-C(l)-Mo 41.0(1) Cp-Mo-Cpa 135.4(4) Ni-C(l)-O 163.5(1) Ni-C(21)-C(26) 145.3(1) Ni-C(22)-C(27) 129.5(1) Ni-C(23)-C(38) 130.3(1) Ni-C(24)-C(29) 147.4(1) Ni-C(25)-C(30)

2.226(4) 2.295(6) 2.263(7) 2.301(6) 2.327(6) 2.306(5) 2.056(5) 2.198(5) 2.109(5) 1.428(10) 1.388(11) 1.331(10) 1.357(9) 1.399(11) 1.407(6) 1.427(6) 1.183(6) 82.8(2) 139.0(4) 141.8(4) 124.3(4) 127.0(4) 128.8(4) 128.7(4) 125.8(5)

" Angle between the two perpendicular lines from Mo to the Cp rings. W-Ru and Mo-Ru Complexes. Photolysis of the metallocene dihydride in the presence of the ruthenium dimer [CpRu(CO)& proceeded smoothly and gave the originally expected heterotrimetallic complexes. Thus irradiation and subsequent column chromatography of

A Photochemical Route to Heterometallic Complexes

Organometallics, Vol. 14, No. 12, 1995 5601

Table 4. Selected Bond Distances (A)and Angles (deg) for 3a W-Ru(l) W-C(l) W-C(16) W-C(l7) W-C(18) w-C(19) W-C(20) Ru(l)-C(21) R~(l)-C(22) R~(l)-C(23) R~(l)-C(24) R~(l)-C(25) C(16)-C(17) C(18)-C(19) C(20)-C(16) C(2)-0(2)

Figure 3. View of C~(C~H~)W(CO)~[C~~RU~(CO)HI (3a) W-Ru(l)-Ru(2) showing the atom-labeling scheme. Ru(l)-Ru(2)-C(16)

an equimolar mixture of CpzMHz (M = Mo, W) and [CpRu(C0)212yielded two complexes, both as air-stable dark-brown crystals. A small amount of [RuH(CO)CpI3lo was also obtained as a byproduct. Elemental analysis and spectral data indicated that one of the new complexes had the composition Cp(C5H4)M(CO)dCp2Ru2(CO)Hl (3a, M = W, 20%; 3b, M = Mo, 14% yield) while the other was more symmetric, (C5H4)2M[CpRu(CO)Hl2(4a, M = W, 30%;4b, M = Mo, 12%yield). The lH NMR spectra of complexes 3 exhibit three singlets which indicates that three of the four cyclopentadienyl rings are not metalated, while the fourth Cp ring shows four different multiplets. In addition, a singlet peak assignable to a hydride was observed a t -22.06 (3a) or -21.82 (3b) ppm. Since this peak in the NMR spectra of 3a has no satellite, it must not be bound t o the tungsten but to one of the ruthenium centers. An X-ray analysis of 3a revealed the structure shown in Figure 3, with bond lengths and angles as tabulated in Table 4. The distance between the two ruthenium atoms is 2.983(2) A, indicating the presence of a metal-metal single bond. The CO-bridged Ru-Ru bond in the starting dimer [CpRu(C0)2]2 has a shorter length of 2.735(2)A.11 The W-Ru(1) bond with two bridging COS is also short, 2.784(1)A, which has a character of dative interaction from W to Ru as is obvious from the electron count a t the W center. The third CO is coordinated to Ru(2) as a terminal ligand. Though hydride could not be located from the Fourier map, it must be bonded to Ru(2), as judged by the electron count at the Ru(1) and Ru(2) centers. Inspection of the bond angles a t Ru(2) indicates that the hydride occupies the position between Ru(2)-Ru(l) and Ru(2)-C(3) bonds, the angles Ru(1)Ru(~)-C(16), C(3)-R~(2)-C(16), and Ru(l)-Ru(2)-C(3) being 77.0,88.1, and 105.0",respectively (Table 4). The bond angles at the two Ru centers do not support a structure with a hydride bridge between Ru(1) and Ru(2). The proton NMR spectra of complexes 4 show two singlet signals of Cp protons, eight multiplets due to two different @,~7-7~-CsH4) units, and two nonequivalent hydride peaks. The hydride absorptions in 4a are observed as two doublets at -24.47 and -24.96 ppm (10)Forrow, N. J.;b o x , S. A. R.; Morris, M. J. J.Chem. Soc., Chem. Commun. 1983,234. (11)Mills, 0 . S.; Nice, J. P. J.Organomet. Chem. 1967,9, 339.

W-C(l)-Ru(l) W-C(l)-O(l) W-C(2)-0(2) C(3)-R~(2)-C(16) C(l)-Ru(l)-C(2) C(2)-Ru(l)-Ru(2)

Bond Distances 2.784(1) Ru(l)-Ru(2) 2.177(9) W-C(2) 2.392(10) Ru(l)-C(l) 2.304(10) Ru(l)-C(2) 2.318(10) Ru(2)-C(3) 2.327(12) R~(2)-C(16) 2.377(12) 2.296(12) Ru(2)-C(26) 2.281(12) Ru(2)-C(27) 2.301(11) Ru(2)-C(28) 2.265(13) Ru(2)-C(29) 2.275(16) Ru(2)-C(30) 1.457(15) C(17)-C(18) 1.431(17) C(19)-C(20) 1.474(13) C(1)-0(1) 1.191(11) C(3)-0(3) Bond Angles 84.52(4) Cp-W-Cp" 77.0(3) Ru(2)-C(16)-W 84.0(4) W-C(2)-Ru( 1) 138.1(7) Ru(l)-C(l)-O(l) 136.3(7) R~(l)-C(2)-0(2) 88.1(4) Ru(l)-Ru(2)-C(3) 102.6(4) C(l)-Ru(l)-Ru(2) 93.4(3)

2.983(2) 2.192(10) 1.978(11) 1.950(9) 1.832(12) 2.051(8) 2.237(13) 2.221(11) 2.287(11) 2.320(11) 2.291(12) 1.421(13) 1.442(14) 1.178(13) 1.157(16) 134.2(6) 47.5(4) 84.2(4) 137.6(7) 139.1(7) 105.0(3) 80.5(3)

a Angle between the two perpendicular lines from W to the Cp rings.

Figure 4. View of (CbH4)2W[CpRu(CO)Hl2(4a) showing the atom-labeling scheme.

with satellite peaks (JHH= 4.0, ~ J w =H 59.4 ~ Hz), and those in 4b, as two well-defined doublets at 6 -22.12 and -22.20 (JHH = 3.6) ppm. The observed H-H coupling and the Is3W-lH satellites are indications that the hydrides are interacting with the central metallocene center. The X-ray structure of 4a has been determined and is shown in Figure 4. Each of the metallocene Cp rings has been metalated by ruthenium, and the two ruthenium moieties differ in the orientation of the C and CO ligands. The Ru-Ru distance is 4.697(2) ;therefore, no direct interaction between them exists. Table 5 contains important bond lengths and angles. The W-Ru(1) bond length of 3.048(1) A is a little longer than W-Ru(2) of 3.033(1) A,but the IR carbonyl absorptions in solution appear at the same position (1924 cm-l). These bond lengths are much longer than the W-Ru(1) bond in 3a (2.784(1)A) since the bond character is much different, i.e. the W-Ru in 3a is a pure dative bond with two bridging ligands. Though the positions of hydrides could not be located from the difference-Fourier map, we assume that hydrides bonded to the metallocene center are also interacting with ruthenium atoms since the configuration

B:

Nakajima et al.

5602 Organometallics, Vol. 14, No. 12, 1995

around each ruthenium atom deviates from regular tripod piano stool orientation, as is obvious from the environment of Ru(2) in Figure 4. Two possible bonding descriptions of 4 which are consistent with the 18electron rule at each metal center are one with two dative bonds from M (M = W or Mol to Ru and the hydrides bound only to M (form I) and the other with two single bonds between M and Ru, the hydrides being bonded only to the Ru centers (form 11). The column chromatographic fraction from which 4a crystallized contained other isomers. The lH NMR spectrum of the residue showed, except for the peaks due to 4a, two singlet hydride signals with satellites a t -25.12 (isomer 4a’, ~ J w H=~59.4 Hz) and -24.36 ppm 54.0 ~ Hz) and two singlets due to (isomer 4a”, ~ J w=H Cp-Ru at 4.68 (isomer 4a’) and 4.73 ppm (isomer 4a”). The @,o-$-CsH4) signals were too complicated to be analyzed, but from the peak intensities mentioned above the ratio of isomers was 4d4a’/4af’x 4/2/1. If we denote the Ru configurations in 4a as (R,S),those in the isomers must be (RP) and (S,S) since the hydride signals are observed as singlets. Likewise, isomers of 4b were found in the ratio 4b/4b/4b” FZ 4/2/1 with singlet peaks at -22.63, 4.63 (4b) and -21.68, 4.72 (4b”)ppm. The reaction is illustrated schematically in eq 3. As a reaction path toward the the formation of 3 and 4, a

\

CP

- 2co

38 M-W 3b : M-MO ~

(3)

loss of dihydrogen from the metallocene dihydride in the initial photoreaction is assumed. Attack of the generated metallocene on one of the ruthenium moieties of [Cp(CO)aRulzand subsequent C-H oxidative addition of the metallocene Cp ring to the other ruthenium, expelling one CO ligand from it, will give 3. When the metallocene attacks the metal-metal bond and inserts into it, as has been originally expected, one CO ligand is removed from each ruthenium center leading to oxidative addition of the metallocene H&-H to both of the rutheniums to give 4 (form 11). Tkermal or photochemical conversion of 3 to 4 was not successful. Experimental Section Most manipulations were performed in a dry oxygen-free argon atmosphere. Solvents were purified by standard methods and freshly distilled (from Na-benzophenone or CaH2) under argon before use. Photochemical reactions were per-

Table 5. Selected Bond Distances (deg) for 4a W-Ru( 1) W-C(l1) w-C(12) W-C(13) W-C(14) W-C(15) Ru(1)-C( 1) Ru(l)-C(11) C(ll)-C(12) C(12)-C(13) C(13)-C(14) C(14)-C(15) C(15)-C(ll) C( 1)-0(1) Ru(l)-W-Ru(2) W-RU(l)-C(ll) W-Ru(l)-C(l)

and Angles

Bond Distances 3.047(2) W -Ru( 2) 2.191(13) W-C(16) 2.217(13) W-C(l7) 2.239(12) W-C(18) 2.291(13) W-C(19) 2.281(12) W-C(20) 1.816(12) Ru(2)-C(2) Ru(2)-C(16) 2.032(12) C(16)-C(17) 1.435(16) C(17)-C(18) 1.400(21) C(18)-C(19) 1.465(20) C(19)-C(20) 1.358(19) ’ C(20)-C(16) 1.411(18) 1.177(15) C(2)-0(2) Bond Angles 101.15(4) Cp-W-Cpa 45.9(4) W-Ru(2)-C(16) W-Ru(2)-C(2) 96.0(2)

3.033(1) 2.238(12) 2.271(12) 2.270(12) 2.261(12) 2.256(14) 1.798(12) 1.995(11) 1.453(17) 1.425(17) 1.428(19) 1.466(18) 1.424(17) 1.169(15) 146.3(6) 47.5(4) 95.4(4)

a Angle between the two perpendicular lines from W to the Cp rings.

formed with a Riko 100-W high-pressure mercury lamp in a Pyrex flask of 150 mL volume. The starting materials and complexes cp~MoH2,’~ Cp2WH2,12 [CpMo(C0)312,13[CpW(C0)3]2,l3[CpR~(C0)212,’~ [CpNi(C0)12,15 and [Cp*Ni(C0)1216 were obtained by published procedures. All other reagents were commercially obtained. ‘H- and 13C-NMR spectra were recorded on a JEOL EX-270 spectrometer. The J-value signs were not determined. IR spectra were recorded on a PerkinElmer FT-1650 spectrometer using THF solutions of samples in a CaFz liquid cell. Melting points were measured under argon and were not corrected: all the samples decomposed on melting. Cp(C5&)(CO)W-Mo(CO)&p (la). A mixture of CpzWH2 (123 mg, 0.39 mmol) and [CpMo(CO)& (188 mg, 0.38 mmol) in DME (120 ml) was irradiated until most of CpzWH2 was consumed (35 h) as monitored by lH NMR spectra. The initially red solution became dark red, and a small quantity of dark-red material precipitated. The solvent was evaporated under reduced pressure. The residual dark-red solid was chromatographed on alumina (deactivated with 5 wt % HzO, 2 x 18 cm). Elution with hexane gave a mixture of CpzWH2 and [CpMo(CO)& as a pink band. Further elution with CH2Cl2 gave a dark red fraction which after evaporation to dryness yielded l a as dark-red solid (95.2 mg, 0.17 mmol, 43% yield). The analytically pure sample was obtained by recrystallization from THF-hexane as dark-red plates (mp 235-237 “C). ‘H NMR (CDzC12): 6 5.55 (m, p,a-q5-C5H4,lH), 5.32 (m, p,a-q5C5H4, lH), 5.23 (s,q5-C5H5,5H), 5.14 (bs, p,a-q5-C5H4,lH), 5.02 (s, q5-C5H5,5H), 4.04 (m, p,a-q5-C5H4,1H). IR v(C0): 1961 (s), 1882 (s), 1799 (s) cm-l. Anal. Calcd for C18H1403MoW: C, 38.74; H, 2.53. Found: C, 39.03; H, 2.50. Cp(C&)(CO)Mo-W(CO)&p (lb). A procedure similar to that for la, using CpzMoH2 (88 mg, 0.39 mmol) and [CpW(CO)& (258 mg, 0.39 mmol) and irradiating for 14 h, yielded lb as a dark-red powder (90.8 mg, 0.16 mmol, 42% yield, mp 220-222 “C). Crystallization was not successful. ‘H NMR (DMSO-&): 6 5.59 (m, p,u-q5-C~H4, 2H), 5.45 (s, q5-C5H5,5H), 5.21 (s, q5-C5H5, 5H), 5.04 (m, p,a-q5-C5H4,lH), 3.86 (m, p,uq5-C5H4,1H). IR v(C0): 1971 (s), 1880 (s), 1790 (s) em-’. (12) (a) Green, M. L. H.; McCleverty, J. A,; Wilkinson, G. J . Chem. SOC.1961, 4854. (b) Green, M. L. H.; Knowles, P. J. J . Chem. SOC., Perkin Trans. 1 1973, 989. (13)Birdwhistell, R.; Hackett, P.; Manning, A. R. J . Organomet. Chem. 1978,157,239. (14) Humphries, A. P.; Knox, S. A. R. J. Chem. SOC.,Dalton Trans. 1975, 1710. (15)King, R. B. In Organometallic Syntheses; Academic: New York, 1965; Vol. 1. (16) Mise, T.; Yamazaki, H. J . Organomet. Chem. 1979, 164, 391.

A Photochemical Route to Heterometallic Complexes C~(C~&)(CO)W-W(CO)ZC~ (IC). A solution of Cp2WHz (123 mg, 0.39 mmol) and [CpW(C0)31~ (258 mg, 0.39 mmol) in DME (120 mL) was irradiated for 35 h. Treatment of the mixture in a similar way to that described for l a gave darkred crystals of IC(107.3 mg, 0.17 mmol, 43% yield, mp 212214 "C). 'H NMR (DMSO-&): 6 5.77 (m,p,u-q5-C5H4,lH), 5.53 (m, p,a-q5-C5H4,lH), 5.40 (s, q5-C5H5, 5H), 5.21 (s, q5-C5H5, 5H), 5.11 (m, p,u-q5-C5H4,lH), 3.66 (m, p,u-q5-C5H4,1H). IR v(C0): 1962 (SI, 1876 (SI, 1788 (s) cm-'. Anal. Calcd for C18H1403W2: C, 33.77; H, 2.35. Found: C, 33.47; H, 2.18. Cp(CsH4)(CO)Mo-Mo(CO)zCp (Id). A solution of Cp2MoH2 (88 mg, 0.39 mmol) and [CpMo(CO)& (188 mg, 0.38 mmol) in DME (120 mL) was irradiated for 12 h. Treatment of the mixture in a similar way to that described for l a gave dark-red crystals of the known complex Id (104.8 mg, 0.22 mmol, 56% yield).6.8 CpZWH-Ni(C0)Cp (2a). A solution of CpzWHz (100 mg, 0.32 mmol) and [CpNi(CO)l2(96 mg, 0.32 mmol) in DME (120 mL) was irradiated until most of the CpzWH2 was consumed (37 h) as monitored by IH NMR spectra. The initially red solution became black, and a small quantity of black material precipitated. The solvent was evaporated under reduced pressure. The residual black solid was chromatographed on alumina (deactivated by 10 wt % HzO, 2 x 16 cm). Elution with hexane gave a brown band of [CpNi(CO)lz(38.3 mg, 0.13 mmol, 40%). Further elution with CHzCl2 gave a red band. Evaporation of the solvent from the red eluate t o dryness gave 2a as dark-red solid (82.9 mg, 0.18 mmol, 56% yield). The analytically pure sample was obtained by recrystallization from THF-hexane as dark-red plates (mp 210-212 "C). lH NMR (CD2Clz): 6 5.22 (9, q5-C5H5,5H), 4.72 (s, q5-C5H5, lOH), -5.83 (s, W-H, satellite Jw-H = 73.7 Hz, 1H). IR v(C0): 1732 (s) cm-l. Anal. Calcd for C16H160NiW: C, 41.17; H, 3.45. Found: C, 41.02; H, 3.49. CpZWH--Ni(CO)(C&le5)(2b). A solution of CpzWHz (123 mg, 0.39 mmol) and [(C5Me5)Ni(C0)1~ (172 mg, 0.39 mmol) in DME (120 mL) was irradiated at room temperature for 36 h. The initially red solution became dark red, and a small quantity of black material precipitated. The solvent was evaporated under reduced pressure, and the residual black solid was chromatographed on alumina (deactivated by 10 wt % HzO, 2 x 18 cm). Elution with hexane gave a red band from which [(q5-CsMe5)Ni(C0)12was recovered (73.6 mg, 0.17 mmol, 43%). Further elution with hexane/CHzClz (1/2) gave an orange band. The orange eluate was collected and evaporated to dryness to yield dark-red solid of 2b (48.2 mg, 0.09 mmol, 23% yield). The analytically pure sample was obtained by recrystallization from THF-hexane as dark-red plates (mp 229-230 "C). 'H NMR (C&): 6 4.17 (s, q5-C5H5,lOH), 2.14 (s, C5Me5, 15H), -6.47 (s, W-H, satellite Jw-H = 76.8 Hz, 1H). IR v(C0): 1718 (s) cm-'. Anal. Calcd for CzlH260NiW: C, 46.97; H, 4.87. Found: C, 46.98; H, 4.87. CpmoH-Ni(CO)Cp (2c). A mixture of CpzMoH2 (88 mg, 0.39 mmol) and [CpNi(CO)lz(118 mg, 0.39mmol) in DME (120 mL) was irradiated for 14 h. The solvent was evaporated under reduced pressure, and the residual black solid was treated as described above. Complex 2c crystallized from THF-hexane as dark-red plates (51.6 mg, 0.14 mmol, 35% yield, mp 215-216 "C). 'H NMR (CDzC12): 6 5.16 (s, q5-C5H5, 5H), 4.75 (s,q5-C5H5, lOH), -6.43 (s, Mo-H, 1H). IR v(C0): 1755 (s) cm-'. Anal. Calcd for C16H160MoNi: c, 50.17; H, 3.96. Found: C, 50.49; H, 3.96. CpmoH-Ni(CO)(CsMes) (2d). A solution of CpzMoH2 (88 mg, 0.39 mmol) and [(q5-CsMe5)Ni(C0)12(172 mg, 0.39 mmol) in DME (120 mL) was irradiated for 35 h. The initially red solution became dark red, and a small quantity of black material precipitated. The solvent was evaporated under reduced pressure, and the residual black solid was treated as described above. Recrystallization from THF-hexane gave 2d as dark-red plates (43.9 mg, 0.10 mmol, 25% yield, mp 235237 "C). 'H NMR (CsDs): 6 4.21 (s, q5-C5H5,lOH), 2.11 (s, CgMe5, 15H), -5.57 (s, Mo-H, 1H). IR v(C0): 1741 (s) cm-'.

Organometallics, Vol. 14, No. 12, 1995 5603 Anal. Calcd for CzlH~60MoNi:C, 56.17; H, 5.84. Found: C, 56.28; H, 5.79.

Preparation of C~(C~H~)W(CO)Z[C~ZRUZ(CO)H] (3a) and (C~H~)ZW[C~RU(CO)HIZ (4a). A mixture of CpzWHz (123 mg, 0.39 mmol) and [CpRu(CO)& (172 mg, 0.39 mmol) in DME (120 mL) was irradiated until most of CpzWH2 was consumed (64 h) as monitored by 'H NMR spectra. The initially yellow solution became dark red, and a small quantity of orange material precipitated. The solvent was evaporated under reduced pressure, and the residual dark-red solid was chromatographed on alumina (deactivated with 5 wt % H20, 2 x 15 cm). Three bands separated. The first blue bland which was eluted with hexane gave, after evaporation of the solvent and recrystallization from toluene, blue crystals (19.4 mg, 0.04 mmol) of the known triruthenium cluster [RuH(CO)Cpls, as identified by spectral data and the unit cell dimension from X-ray diffraction.'O The second brown band was eluted with hexane. Crystallization from toluene gave brown plates of 4a (87.5 mg, 0.12 mmol, 30% yield, mp 138-140 "C). Elution of the third orange band with CH2ClflHF (4/1), evaporation of the solvent, and recrystallization from THFhexane gave red crystals of 3a (57.0 mg, 0.08 mmol, 20% yield, mp 193-194 "C). 3a: 'H NMR (CDZC12)6 5.68 (m,p,a-q5-C5H4, lH), 5.32 (m, p,a-q5-C5H4,1H),5.06 (m p,u-q5-C5H4,lH), 5.02 (s, 115-C5H5, 5H), 4.92 (s, q5-C5H5, 5H), 4.81 (s, q5-C5H5, 5H), 4.73 (m, p,a-q5-C5H4,lH), -22.06 (s, Ru-H, 1H); IR v(C0) 2048 (s), 1995 (s), 1921 (s), 1694 (5) cm-'. Anal. Calcd for C23H2003RuzW: C, 37.82; H, 2.76. Found: C, 37.66; H, 2.96. 4a: 'H NMR (CsD6) 6 5.47 (m, p,a-q5-C5H4,lH), 5.11 (m, p,a-q5-C5H4, 2H), 4.98 (m, p,u-q5-C5H4,lH), 4.95 (s, q5-C5H5,5H), 4.51 (s, q5-C5H5,5H), 4.50 (sh, p,a-q5-C5H4,lH), 4.48 (m, p,u-q5-C5H4, lH), 2.95 (m p,u-q5-C5H4, lH), 2.90 (m, p,a-q5-C5H4, lH), -24.47 (d, M-H, JH-H = 4.0, satellite Jw-H = 59.4 Hz, lH), = 4.0, satellite Jw-H = 59.4 Hz, 1H); -24.96 (d, M-H, JH-H IR (THF) v(C0) 1924 (s) cm-'. Anal. Calcd for C22H2002RuzW.VzC7H8: C, 40.92; H, 3.23. Found: C, 41.14; H, 3.23.

Preparation of C~(C~H~)MO(CO)~[C~~RUZ(CO)HI (3b) and (C~H4)&lo[CpRu(CO)Hl~ (4b). A solution of CpzMoHz (96 mg, 0.42 mmol) and [CpRu(CO)zlz(184 mg, 0.42 mmol) in DME (120 mL) was irradiated for 66 h. After the solvent was evaporated under reduced pressure, the residual dark-red solid was treated on column chromatography (A1203 deactivated with 5 wt % H20, 2 x 15 cm). Elution of three bands were performed using the same reaction mixtures as in the case of the W analog described above. Besides the triruthenium cluster [RuH(CO)Cpl3 (37.2 mg, 0.06 mmol), red crystals of 3b (39.4 mg, 0.06 mmol, 14% yield, mp 190-191 "C) and brown crystals of 4b (29.9 mg, 0.05 mmol, 12% yield, mp 143-145 "C) were isolated. 3b: 'H NMR (CDC13)6 5.63 (m, p,u-q5-C5H4, lH), 5.48 (m, p,a-q5-C5H4,l H ) , 5.14 (mp,a-q5-CsH4, lH), 5.09 (s, q5-C55,5H), 4.93 (s, q5-C5H5,5H), 4.90 (m, p,u-q5-C5H4, lH), 4.71 (s, q5-C5H5,5H), -21.82 (s, Ru-H, 1H); IR v(C0) 2048 (s), 1995 (s), 1922 (s), 1717 (s) cm-'. Anal. Calcd for C23H2003MoRu2: C, 43.00; H, 3.14. Found: C, 43.01; H, 3.15. 4b: 'H NMR (C&) 6 5.73 (m, pU,~-q5-C5H4, lH), 5.30 (m, p,u-q5-C5H4, lH), 4.97 (s, q5-C5H5,5H), 4.76 (m, p,u-q5-C5H4, lH), 4.71 (m, p,u-q5-C5H4,lH), 4.48 (s, q5-C5H5,5H), 4.15 (m, p,a-q5-C5H4, 2H), 3.33 (m, p,u-q5-C5H4, lH), 3.29 (m, p,u-q5-CsH4, lH), -22.12 (d, M-H, JH-H = 3.6 Hz, lH), -22.20 (d, M-H, JH-H = 3.6 Hz, 1H); IR v(C0) 1924 (s) cm-I. Anal. Calcd for C ~ ~ H ~ O O ~ M O R U ~C,. '46.36; / ~ C ~ H, H ~3.69. : Found: C, 46.58; H, 3.66. X-ray Crystallographic Analysis of la, 2d, 3a, and 4a. Crystal, data collection, and refinement parameters are summarized in Table 1. Single crystals were grown from THFhexane (la,2d, 3a) or from saturated toluene (4a). Reflection data were collected at room temperature on an Enraf-Nonius CAD-4 diffractometer using graphite-monochromated Mo Ka radiation and the 28-w scan technique. The structures were solved from direct and Fourier methods and refined by blockdiagonal least squares with anisotropic thermal parameters in the last cycles for all non-hydrogen atoms. Hydrogen atoms

5604 Organometallics, Vol. 14,No. 12, 1995 for the cyclopentadienyl rings in l a and 4a were placed in calculated positions, while methyl hydrogens in 2d were located from a difference Fourier map. These hydrogen atoms were included in subsequent refinements with isotropic thermal parameters. The metal-bound hydrogen atoms could not be located. Only three carbon atoms of crystallized solvent (toluene) in 4a could be located in a gap of the crystal lattice, suggesting high disorder of the C7Ha group, and these were included in subsequent refinements with isotropic thermal parameters. In the refinements unit weight was applied. The function minimized in the least-squares refinement was Cw(lFol- IFc1)2.The computational program package used in the analysis was the UNICS 3 program system." Neutral atomic scattering factors were taken from ref 18. Important bond lengths and angles are given in Tables 2-5.

Nakajima et al.

Acknowledgment. We are grateful for financial support of this work by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan. Supporting Information Available: Tables of positional and thermal parameters and bond distances and angles (31 pages). Ordering information is given on any current masthead page.

OM950520G (17)Sakurai, T.; Kobayashi, K. Rikagaku Kenkyusho Hokoku 1979, 55, 69. (18)International Tables for X-Ray Crystallography; Kynoch: Bir-

mingham, England, 1974;Vol. IV.