Heterometallic Trinuclear Polyhydrido Complexes Containing

Organometallics 2009, 28, 871–881

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Heterometallic Trinuclear Polyhydrido Complexes Containing Ruthenium and a Group 9 Metal, [Cp*3Ru2M(µ3-H)(µ-H)3] (M ) Ir or Rh; Cp* ) η5-C5Me5): Synthesis, Structure, and Site Selectivity in Reactions with Phosphines Takanori Shima,§ Yumi Sugimura, and Hiroharu Suzuki* Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan ReceiVed October 30, 2008

A heterometallic trinuclear polyhydrido complex, [Cp*3Ru2Ir(µ3-H)(µ-H)3] (Cp* ) η5-C5Me5) (1), was synthesized by dehydrogenative coupling between a dinuclear ruthenium tetrahydrido complex, [Cp*Ru(µH)4RuCp*], and an equimolar amount of a mononuclear iridium tetrahydrido complex, Cp*IrH4. The Ru-Rh analogue, [Cp*3Ru2Rh(µ3-H)(µ-H)3] (2), was synthesized by reacting a 2:1 mixture of the dichlorido dimers (Cp*RuCl2)2 and (Cp*RhCl2)2 with NaBH4. The molecular structure of [Cp*2(C5Me4Et)Ru2Ir(µ3-H)(µ-H)3] (1′′) was determined through single-crystal X-ray diffraction. The mutual exchange of the hydrido ligands in 1 among the coordination sites was analyzed using variable-temperature (VT)-1H NMR spectroscopy. Complex 1 undergoes an H/D exchange between the hydrido ligands and C6D6 via C-H bond cleavage/formation. The reactivity of 1 toward tertiary and secondary phosphines was studied to elucidate the roles of each metal atom in the substrate activation step. The reactions of 1 with tertiary phosphines afford the phosphine complexes [Cp*3Ru2Ir(PR3)(µ-H)4] (R ) Me, 3a; Et, 3b; Ph, 3c; OMe, 3d), in which the phosphine is bound to the one of the Ru atoms in a terminal mode. Treatment of 1 with PPh2H exclusively produces a µ-phosphido complex, [Cp*3Ru2Ir(µ-PPh2)(µ-H)3] (5), in which the phosphido ligand bridges the Ru-Ir edge through the intermediary µ-phosphido complex [Cp*3Ru2Ir(µPPh2)(µ-H)5] (6), in which the phosphido ligand bridges the Ru-Ru edge. The fluxional behavior of the µ-phosphido ligand in 5 was elucidated by VT-1H NMR and selective pulse irradiation. Thermolysis of 5 generates a µ3-phosphinidene complex, [Cp*3Ru2Ir(µ3-PPh)(µ-H)2] (7), via P-C(ipso) bond cleavage and the reductive elimination of benzene. Introduction The chemistry of heteromultimetallic systems has been intensively studied, in part due to the promise of enhanced stoichiometric or catalytic reactivity from the cooperative activation and synergistic interaction of metal centers with differing electronic properties.1 The authors have recently reported the synthesis of novel heterometallic dinuclear polyhydrido complexes, [Cp*Ru(µ-H)3IrCp*] (Cp* ) η5-C5Me5),2,3 [Cp*Ru(µ-H)3MH3Cp*] (M ) Mo, W),4 [Cp*Ru(µ-H)3ReH2Cp*],5 and [Cp*Ru(µ-H)4OsCp*],6,7 and heterometallic trinuclear polyhydrido complexes, [Cp*3Ru2Re(µ-H)4], [Cp*3Re2Ru(µ-H)5],5 and [Cp*3Ru2M(µ-H)5] (M ) Mo, W),8 as precursors of active species for heteromultimetallic actiVation. Several typical examples of site-selective coordination and activation through reactions with organic substrates such as * To whom correspondence should be addressed. E-mail: hiroharu@ n.cc.titech.ac.jp. Tel: (+81)-3-5734-2148. Fax: (+81)-3-5734-3913. § Current address: Organometallic Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198, Japan. (1) For recent examples, see: ComprehensiVe Organometallic Chemistry III; Crabtree, R. H.; Mingos, D. M. P., Eds.; Elsevier: Oxford, 2007; Vol. 6, and references therein. (2) Shima, T.; Suzuki, H. Organometallics 2000, 19, 2420. (3) Shima, T.; Suzuki, H. Organometallics 2005, 24, 1703. (4) Shima, T.; Ito, J.; Suzuki, H. Organometallics 2001, 20, 10. (5) Ito, J.; Shima, T.; Suzuki, H. Organometallics 2004, 23, 2447. (6) Shima, T.; Suzuki, H. Organometallics 2005, 24, 3939. (7) Shima, T.; Ichikawa, T.; Suzuki, H. Organometallics 2007, 26, 6329. (8) Ito, J.; Shima, T.; Suzuki, H. Organometallics 2006, 25, 1333.

phosphines have been demonstrated. For example, the phosphido complex [Cp*Ru(µ-PPh2)(µ-H)(µ-η1:η2-C6H5)IrCp*] was exclusively formed through site-selective coordination of the triphenylphosphine to the Ru center and subsequent P-C bond cleavage at the Ir center in the reaction of [Cp*Ru(µ-H)3IrCp*] with PPh3.3 Thus, the metal centers of heterometallic dinuclear complexes may play the complementary roles of coordination and activation sites. This site-selective activation of substrates in heterometallic dinuclear systems may also be possible in trinuclear systems. This article reports the synthesis, structural determination, and H/D exchange reaction of a heterometallic trinuclear tetrahydrido complex, [Cp*3Ru2M(µ3-H)(µ-H)3] (M ) Ir (1), Rh (2)), containing two Ru atoms and a group 9 metal atom, and describes the site-selective reactions of 1 with tertiary and secondary phosphines.

Results and Discussion Synthesis of the Heterometallic Trinuclear Polyhydrido Complex [Cp*3Ru2M(µ3-H)(µ-H)3] (M ) Ir (1), Rh (2)). Previously, we reported that the diruthenium tetrahydrido complex [Cp*Ru(µ-H)4RuCp*] was a suitable precursor for the synthesis of a heterometallic polyhydrido complex containing ruthenium and rhenium.5 The heterometallic trinuclear polyhydrido complex [Cp*3Ru2Re(µ-H)4] was obtained by reacting [Cp*Ru(µ-H)4RuCp*] with a mononuclear rhenium hexahydrido complex, Cp*ReH6. Coupling two metal fragments through

10.1021/om8010432 CCC: $40.75  2009 American Chemical Society Publication on Web 01/06/2009

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intermolecular dehydrogenation is a useful and practical method for the synthesis of heterometallic polyhydrido complexes. This method was applied to the synthesis of new heterometallic trinuclear complexes having a metal-metal bond between ruthenium and iridium. The reaction of [Cp*Ru(µ-H)4RuCp*] with an equimolar amount of Cp*IrH49 in toluene at 100 °C for 4 h resulted in the formation of a heterometallic trinuclear tetrahydrido complex, [Cp*3Ru2Ir(µ3-H)(µ-H)3] (1) (76% yield), and a heterometallic dinuclear trihydrido complex, [Cp*Ru(µ-H)3IrCp*] (6% yield) (eq 1). Complex 1 could also be synthesized in low yield (ca. 15%) by reacting 1.0 equiv of the super hydride LiBEt3H with the chloride complex [Cp*3Ru2Ir(µ-Cl)(µ-H)3] obtained by reacting [Cp*Ru(µ-H)3IrCp*] with a Cuban-type ruthenium complex, [Cp*Ru(µ-Cl)]4.10 When a mixture of 1 and 1.7 equiv of Cp*IrH4 was heated in toluene at 100 °C for 71 h, [Cp*Ru(µH)3IrCp*] was formed in 58% yield, demonstrating that the sideproduct [Cp*Ru(µ-H)3IrCp*] is formed by way of 1.

1.88 (30H). The former was ascribed to the Cp* group coordinated to the Ir atom. To establish the assignment of the Cp* signal for 1 more conclusively, the 1H NMR spectrum of 1 in C6D6 was compared with those of the Ru-Rh analogue 2. The 1H NMR spectrum of 2 in C6D6 showed a peak at δ 1.79 (15H) that could be attributed to the Cp* group bound to the Rh atom and another at δ 2.02 (30H) that could be attributed to the Cp* group bound to the Ru atom. While the Cp* peak for 1 was a sharp singlet, the shape and chemical shift of the peaks for the hydrido ligands were temperature-dependent due to fluxional site exchange of the hydrido ligands (Figure 1). In the 1H NMR spectrum of 1 recorded at 60 °C, the four hydrido ligands were observed to be equivalent at δ -14.82. With a decrease in the temperature, a significant broadening of this peak was observed. The peak then decoalesced and split into two peaks with an intensity ratio of 1:3; at -80 °C, two singlet peaks were observed at δ -5.53 (1H) and -17.97 (3H). While the peak at δ -5.53 remained

The Ru-Ir heterometallic analogues, [(η5-C5Me4Et)2Cp*Ru2Ir(µ3-H)(µ-H)3] (1′) and [Cp*2(η5-C5Me4Et)Ru2Ir(µ3-H)(µ-H)3] (1′′), were synthesized in a similar manner using [(η5C5Me4Et)Ru(µ-H)4Ru(η5-C5Me4Et)] and [(η5-C5Me4Et)IrH4] as the starting material, respectively. Although there are no suitable rhodium polyhydrido species such as “Cp*RhH4” with which to synthesize a Ru-Rh heterometallic cluster, the Ru-Rh tetrahydrido complex [Cp*3Ru2Rh(µ3H)(µ-H)3] (2) can be successfully synthesized in 28% isolated yield by reacting a mixture of the dichloride dimers (Cp*RuCl2)211 (2 equiv) and (Cp*RhCl2)212 (1 equiv) with the hydride reagent NaBH4 (eq 2). The Ru-M heterometallic dinuclear complexes [Cp*Ru(µ-H)3MH3Cp*] (M ) Mo, W) have also been previously synthesized from the chloride complexes Cp*MCl4 (M ) Mo, W) and [Cp*Ru(µ-Cl)]4.4

almost unchanged with decreasing temperature, a significant broadening of the peak at δ -17.97 was observed. However, the broad peak did not split in two even at -120 °C. The assignment of the Ru-µ-H-Ru ligand (HC) was clarified by determining the low-temperature 1H NMR spectrum of 2. The fluxionality of the hydride ligands in 2 was quite similar to that in 1. At room temperature, one peak for the hydrido ligands was observed at δ -12.43 (d, JHRh ) 28.0 Hz, 4H), demonstrating their equivalency. At -90 °C, two singlet peaks were observed at δ -6.88 (1H) and -14.38 (3H). The peak at δ -6.88 remained a singlet with decreasing temperature and showed that coupling with the 103Rh nucleus did not occur. This clearly indicates that the peak at δ -6.88 is associated with the hydrido ligand located on the Ru-Ru edge. From this result, the sharp singlet peaks observed at δ -5.53 (1H) and -17.97 (3H) at -80 °C for 1 can be assigned to HC and the average peak for the two Ru-µ-H-Ir ligands (HA) and the Ru2-µ3H-Ir ligand (HB), respectively. The dynamic behavior of 1, specifically, the site exchange of the hydrides among the Ru-Ru and Ru-Ir edges (eq 3), was studied by VT-1H NMR and line shape analysis for temperatures ranging from +25 to -50 °C (Figure 1, right).

Complex 1 was unambiguously identified using NMR spectroscopy as well as X-ray diffraction (vide infra). The 1H NMR spectrum of 1 recorded at room temperature in C6D6 exhibited one peak attributable to the Cp* group at δ 2.01 (45H) and one broad peak for the bridging hydrides at δ -14.46 (4H). Although only one peak attributable to the Cp* group was observed in C6D6, the 1H NMR spectrum of 1 in THF-d8 exhibited two singlet peaks attributed to the Cp* group at δ 2.18 (15H) and (9) Gilbert, T. M.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc. 1985, 107, 3508. (10) Fagan, P. J.; Michael, D. W.; Calabrese, J. C. J. Am. Chem. Soc. 1989, 111, 1698. (11) (a) Oshima, N.; Suzuki, H.; Moro-oka, Y. Chem. Lett. 1984, 1161. (b) Tilley, T. D.; Grubbs, R. H.; Bercaw, J. E. Organometallics 1984, 3, 274. (12) Kang, J. W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969, 91, 5970.

On the basis of these results, the enthalpy, entropy, and free energy of activation were estimated to be ∆Hq ) 9.9(2) kcal/ mol, ∆Sq ) -0.3(8) cal/mol · K, and ∆Gq298K ) 10.0 kcal/mol, respectively. The small absolute value of ∆Sq indicates that the hydride site exchange is an intramolecular process. The value of ∆Gq298K is comparable to those for the site exchange of hydrido ligands among the Ru-Ru and the Ru-M edges in the heterometallic polyhydrido analogues [Cp*3Ru2M(µ-H)5] (∆Gq298K ) 12.2 kcal/mol for M ) Mo and 11.2 kcal/mol for M ) W).8 It was not possible to estimate the activation

Heterometallic Trinuclear Polyhydrido Complexes

Figure 1. Experimental (left, THF-d8) and simulated (right) variable-temperature (VT)-1H NMR spectra of 1 showing the hydrido region.

parameters for the site exchange process between the µ2-HA and µ3-HB bridging hydrides due to insufficient separation between the peaks for the three hydride ligands at δ -17.97, even at -120 °C. Such rapid site exchange of the hydrides between µ2-H and µ3-H has also been observed in the ruthenium hydride complex [Cp*3Ru3(µ3-H)2(µ-H)3].13 To obtain information on the bonding mode of the hydride ligands in 1, the longitudinal relaxation time (T1) was measured in THF-d8 at 400 MHz. The T1 values of 2.01 s at 298 K and 560 ms (δ -5.53) and 789 ms (δ -17.97) at 203 K for the hydrido peaks for 1 are comparable with those for the hydrido peaks for [Cp*Ru(µ-H)3IrCp*] (3.34 s at 193 K) and [Cp*3Ru3(µ3H)2(µ-H)3] (2.55 s at 193 K). From the T1 values, it is clear that there are no bonding interactions among the hydrido ligands in 1. H/D Exchange Reaction between C6D6 and the Hydrido Ligands in 1. The hydrido ligands in 1 exchange with those in C6D6 (Figure 2). A solution of 1 in C6D6 was heated in a sealed NMR sample tube to 100 °C, and the H/D exchange reaction was monitored by 1H NMR with cyclohexane as the internal standard. Upon heating for 7 h, four peaks assignable to the isotopomers [Cp*3Ru2Ir(µ-H)4] (1-d0), [Cp*3Ru2Ir(µ-H)3(µ-D)] (1-d1), [Cp*3Ru2Ir(µ-H)2(µ-D)2] (1-d2), and [Cp*3Ru2Ir(µ-H)(µD)3] (1-d3) were observed at δ -14.46, -14.66, -14.87, and -15.11, respectively. After additional heating for 12 h, 81% of the hydrido ligands were replaced with deuterides, and after 66 h, 99% were converted. The H/D exchange of the hydrido ligands most certainly proceeded via the coordination of C6D6 in an η2 fashion, involving the oxidative addition of C6D6 and subsequent reductive elimination of C6D5H. The rate of H/D exchange with C6D6 is reasonably comparable to that of [Cp*3Ru3(µ3-H)2(µ-H)3] (73% of the hydride ligands were exchanged with deuterides after 40 h at 80 °C) and much faster than that of [Cp*3Ru2Re(µ-H)4] (30% of the hydrido ligands were exchanged with deuterides after 210 h at 80 °C). (13) Suzuki, H.; Kakigano, T.; Tada, K.; Igarashi, M.; Matsubara, K.; Inagaki, A.; Oshima, M.; Takao, T. Bull. Chem. Soc. Jpn. 2005, 78, 67.

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Molecular Structure of 1′′. Complex 1 has three C5Me5 ligands on the metal centers. In such cases, the molecular structure is often disordered, despite the unsymmetrical metal core. To avoid the disordered arrangement of the three metal centers, structural determination for the trimetallic complex 1 was performed using [Cp*2(C5Me4Et)Ru2Ir(µ3-H)(µ-H)3] (1′′), which has C5Me5 ligands on the Ru atoms and a C5Me4Et ligand on the Ir atom. Single crystals of 1′′ were obtained from cold pentane. The ORTEP drawing is shown in Figure 3 with the relevant bond lengths and angles. The Ru1-Ir1 and Ru2-Ir1 distances of 2.693(2) and 2.697(1) Å are comparable to the sum of the covalent radii (2.69 Å) and also the reported Ru-Ir distance for [(η4-C8H12)Ir(µH)2RuH(PPh3)3] (2.623 Å),14 but are longer than that for the related dinuclear complex [Cp*Ru(µ-H)3IrCp*] (2.4858(4) Å). The Ru1-Ru2 distance of 2.738(2) Å is comparable to that of the isoelectronic 44-electron complex [Cp*3Ru3(µ3-H)2(µ-H)3] (Ru-Ruav ) 2.7497(7) Å),13 but is considerably shorter than those of the other 42-electron heterometallic complexes, [(C5Me4Et)2Cp*Ru2Mo(µ-H)5] (Ru-Ru ) 3.148(2) Å), [(C5Me4Et)2Cp*Ru2W(µ-H)5] (Ru-Ru ) 3.196(2) Å),8 and [(C5Me4Et)2Cp*Ru2Re(µ-H)4] (Ru-Ru ) 3.233(1) Å).5 This is probably due to the presence of the µ3-bridging hydrido ligands. Indeed, the Ru3 and IrRu2 clusters have µ3-hydrogen ligands at their cores, while the MoRu2, WRu2, and ReRu2 analogues have no µ3-hydrogen ligands. Fortunately, all the metal-bound hydrogen atoms of 1′′ were located in the Fourier maps. Three of the four hydrido ligands bridge the edges of the Ru2Ir triangle, and the other caps the trigonal face. The Cp* centroids are all tilted by approximately 7.6° to one side of the Ru2Ir plane (Figure 3, side view). This distortion is probably responsible for the steric repulsion among the three doubly bridging hydrogens and the Cp* ligands. Theopold and Casey et al. also observed this type of distortion in the structure of the tetrahydrido cobalt complex [Cp*3Co3(µ-H)3(µ3-H)].15 The average distances between the metals and the C5Me5 ring carbons (or C5Me5 centroids) in 1′′ are 2.201 Å (1.833 Å), 2.166 Å (1.795 Å), and 2.158 Å (1.792 Å) for Ir1, Ru1, and Ru2, respectively. The electron density at the metal center is responsible for the distance between the metal and the C5Me5 ring carbons, as a result of back-donation. When a metal center adopts a high oxidation state, back-donation from the metal center to the C5Me5 group should be reduced. As a result, the distances between the metal center and the C5Me5 ring carbons are lengthened. The average distance between the metal centers and the C5Me5 ring carbons (or C5Me5 centroids) in 1′′ is slightly less than that in [Cp*3Ru3(µ3-H)2(µ-H)3] (Ru-C5Me5 centroids: 1.809 Å13) or [Cp*RuIII(µ-H)2]2 (Ru-C5Me5 ring carbons: 2.183 Å16), but comparable to the Ir-Cp* length in [Cp*IrII(µ-H)]2 (Ir-C5Me5 ring carbons: 2.204 Å).17 Reaction with Tertiary Phosphines. On the heterometallic cluster 1, site-selective incorporation and site-selective interaction with the substrate are possible due to the electronically anisotropic reaction field. Previously, the authors reported that the reaction of the trirutheniumpentahydrido complex [Cp*3Ru3(µ3-H)2(µ-H)3] with phosphines afforded a 1:1 adduct, [Cp*3Ru3(µ(14) Poulton, J. T.; Folting, K.; Caulton, K. G. Organometallics 1992, 11, 1364. (15) Kersten, J. L.; Rheingold, A. L.; Theopold, K. H.; Casey, C. P.; Widenhoefer, R. A.; Hop, C. E. C. A. Angew. Chem., Int. Ed. Engl. 1992, 31, 1341. (16) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima, M.; Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 1129. (17) Hou, Z.; Fujita, A.; Koizumi, T.; Yamazaki, H.; Wakatsuki, Y. Organometallics 1999, 18, 1979.


Shima et al.

Figure 2. H/D exchange reaction of 1 (60 °C, C6D6).

Figure 3. ORTEP drawing of [Cp*2(C5Me4Et)Ru2Ir(µ3-H)(µ-H)3] (1′′), with thermal ellipsoids at the 30% probability level. Top view (left) and side view (right). Selected bond lengths (Å) and angles (deg): Ir1-Ru1, 2.693(2); Ir1-Ru2, 2.697(1); Ru1-Ru2, 2.738(2); Ru1-Ir1-Ru2, 61.05(4); Ir1-Ru1-Ru2, 59.55(4); Ir1-Ru2-Ru1, 59.40(4).

H)5(PR3)], by way of an associative pathway.13 Thus, the reaction chemistry of 1 was investigated through its reactions with phosphines to elucidate the roles played by the individual metal atoms. Treatment of 1 with tertiary phosphines PR3 in toluene at ambient temperature resulted in the exclusive formation of 46electron phosphine complexes [Cp*3Ru2Ir(PR3)(µ-H)4] (R ) Me, 3a; Et, 3b; Ph, 3c; OMe, 3d), in which the phosphine was directly bound to the one of the two Ru metals in a terminal mode (eq 4). The reaction mode did not change, irrespective of the phosphine ligand employed. The complexes 3a-d were characterized using 1H, 13C, and 31P NMR and IR spectroscopic analysis, as well as analytical data. Table 1 lists selected 1H, 13 C, and 31P NMR data for 3a-d. The similarity between the δΗ values and intensities for the C5Me5 and the hydrido ligands strongly suggests structural similarity among these complexes. The integral intensity of 4H for the hydrido ligands clearly confirms the addition of the phosphine ligands to the 44-electron complex 1 to afford 46-electron complexes without ligand loss,

which are all electron-deficient with respect to the noble gas rule requiring 48 electrons for trinuclear complexes.

As is apparent from the X-ray diffraction results (vide infra), the phosphine ligand is coordinated to one of the Ru centers. The 1H peaks for the C5Me5 groups coordinated to the Ru atom directly bound to the phosphine ligand appeared around δ 2 ppm as doublets. Complexes 3a-d have no mirror plane, unlike 1. The unsymmetrical structures of 3a-d were corroborated



Table 1. 1H, 13C, and 31P NMR Data (rt) 1

13

H NMR

31

C NMR

P NMR

δ (C5Me5, 15H)

δ (µ-H)

δ (C5Me5)

δ (C5Me5)

δ (P)

3a

2.06 (s) 2.02 (d, JPH ) 1.8 Hz) 1.85 (s)

-10.92 (d, JPH ) 17.7 Hz, 1H) -18.96 (brs, w1/2 ) 307.7 Hz, 3H)

87.7 (s) 87.3 (d) 75.2 (s)

13.5 13.2 11.7

10.9

3b

2.04 (s) 1.97 (d, JPH ) 1.5 Hz) 1.82 (s)

-11.60 (d, JPH ) 24.6 Hz, 1H) -18.37 (brs, w1/2 ) 200.0 Hz, 1H) -19.13 (brs, w1/2 ) 200.0 Hz, 1H) -21.96 (brs, w1/2 ) 160.0 Hz, 1H)

88.0 (s) 86.4 (d) 74.9 (s)

13.4 13.1 11.7

43.8

3c

1.90 (s, 15H) 1.74 (s, 30H)

-10.96 (d, JPH ) 23.7 Hz, 1H) -19.26 (brs, w1/2 ) 281.3 Hz, 3H)

88.4 (s) 88.2 (d) 75.5 (s)

13.1 12.6 11.4

64.9

3d

2.06 (d, JPH ) 2.7 Hz) 2.05 (s) 1.82 (s)

-11.60 (d, JPH ) 25.8 Hz, 1H) -19.23 (brs, w1/2 ) 96.0 Hz, 3H)

90.1 (d) 88.3 (s) 76.0 (s)

13.2 12.6 11.5

175.8

by the presence of three resonance peaks for the C5Me5 groups in the 13C NMR spectra. The JPH value (1.5-2.7 Hz) of the C5Me5 peak is comparable to that for [Cp*3Ru3(PMe3)(µ-H)5] (JPH ) 1.8 Hz), and the doublet C5Me5 peak is assigned to the C5Me5 groups on the Ru atom bound to the phosphine ligand. The peak for one hydride ligand was observed around δ -11 (doublet), while the peaks for the rest of the hydrido ligands (3H) appeared between δ -19 and -20. The latter split into three distinct peaks at low temperature. Figure 4 shows the VT1 H NMR spectrum of 3c. At -50 °C, hydride peaks appeared at δ -10.99 (d, JPH ) 23.2 Hz, 1H), -17.69 (s, 1H), -18.48 (d, JPH ) 20.0 Hz, 1H), and -21.40 (s, 1H). The doublet peak at δ -10.99 is assigned to the hydride bridging the two Ru atoms. The chemical shift is similar to that of [Cp*3Ru3(PMe3)(µ-

Figure 4. VT-1H NMR spectra of 3c (400 MHz, toluene-d8, *impurity).

H)5] (δ -10.90 (d, JPH ) 32.5 Hz)). The doublet peak at δ -18.48 corresponds to the hydride bridging the Ir and Ru atoms, and the Ru atom directly interacts with the phosphine ligand. The rest of the hydrido ligands bridge the Ir atom and the Ru atoms that have no bonding interaction with the phosphine ligand. With an increase in temperature, the three hydrido ligands that bridge the Ir and Ru atoms are mutually exchanged among the coordination sites, and their peaks coalesce around room temperature. The 31P NMR spectra of 3a-d exhibit resonances characteristic of terminal coordination to the Ru atom.11b The Rh analogue 2 reacted with tertiary phosphines in benzene at ambient temperature to form 1:1 adducts [Cp*3Ru2Rh(PR3)(µ-H)4] (R ) Et, 4a; Ph, 4b) similar to 3. The 1H NMR spectrum of 4b recorded at ambient temperature exhibited three Cp* peaks and two peaks attributable to the hydrido ligands. This strongly indicated that the PPh3 ligand is coordinated to one of the Ru atoms. The singlet at δ -16.17 recorded at 23 °C split into three peaks at δ -14.67, -16.16, and -17.20 at -60 °C due to deceleration of the coordination site exchange of the hydrides (see Supporting Information; SFigure 2). The hydrides in 4b were identified on the basis of 1H and 1H{31P} NMR experiments at -60 °C (SFigure 3). Comparison of the spectra revealed that the doublet at δ -10.69 (JH-P ) 24.4 Hz, 1H) corresponded to the hydrides bridging the two Ru atoms and that the doublets at δ -14.67 (JH-Rh ) 26.4 Hz, 1H) and -17.20 (JH-Rh ) 23.6 Hz, 1H) corresponded to the hydrides bridging the Rh and Ru atoms. The doublets of doublet peaks at δ -16.16 (JH-P ) 24.2 Hz, JH-Rh ) 26.4 Hz, 1H) were unambiguously assigned to the hydrides bridging the Rh and Ru atoms bonded to the PPh3 ligand. The chemical shifts and coupling pattern for 4 were similar to those of the iridium analogue 3. Therefore, it was concluded that the reaction pattern of 2 with tertiary phosphines was nearly the same as that of 3. Slow crystallization from a THF/methanol solution of 3b at 0 °C afforded black-purple plates suitable for X-ray analysis. The ORTEP drawing illustrated in Figure 5 establishes the structural identity of 3b. The Ru2Ir core is disordered, having either of two orientations (59:41). Figure 5 clearly demonstrates the structure of 3b in which a triethylphosphine molecule is coordinated to one of the two Ru atoms. The structure of 3b is disordered and has a pseudosymmetry plane with C1, P1, Ru2, and the center of the Ru1-Ir1 bond. Two hydrogen atoms bridge Ru1 and Ir1, and the remaining two hydrogen atoms bridge the Ru1-Ru2 and Ir1-Ru2 bonds. The Cp* ligands coordinated to Ir1 and Ru1 are almost perpendicular to the Ir1-Ru1-Ru2 plane. The


Figure 5. ORTEP drawing of 3b (Ru1,Ir1:Ir1a,Ru1a ) 41:59), with thermal ellipsoids at the 30% probability level. Selected bond lengths (Å) and angles (deg): Ru1-Ru2, 2.9844(9); Ir1-Ru2, 2.9816(9); Ir1-Ru1, 2.6667(8); Ru2-P1, 2.268(2); Ir1-Ru2-Ru1, 53.10(2); Ru2-Ir1-Ru1, 63.40(2); Ru2-Ru1-Ir1, 63.50(2); P1-Ru2-Ir1, 98.58(7); P1-Ru2-Ru1, 97.73(7); Cp-Ru2-P1, 129.7. Cp is the centroid of the C5Me5 ring.

Cp(centroid)-Ru2-P1 angle of 129.7° is typical of the Ru tertiary phosphine complexes and is comparable to the Cp-Ru-P angle in dinuclear ruthenium phosphine complexes [Cp*Ru(PR3)(µ-H)2RuCp*] (Cp-Ru-Pav 130°).18 The Ru2-P1 bond distance (2.268(2) Å) is also in the range of those of the terminally coordinated phosphine or phosphite complexes. The Ru1-Ir1 bond (2.6667(8) Å) is significantly shorter than the Ru1-Ru2 (2.9844(9) Å) and Ir1-Ru2 (2.9817(9) Å) bonds, probably due to the presence of the two bridging hydrido ligands across the Ru1-Ir1 bond. This trend in the metal-metal bond distances is also observed in the triruthenium complex [Cp*3Ru3(P(OPh)3)(µ-H)5] (3.0262(6), 2.9969(6), 2.6504(7) Å).13 Reactions with Secondary Phosphines. The above results illustrate that a single Ru center acts as the coordination site in reactions of 1 with tertiary phosphines. It is of considerable interest to determine which metal centers activate P-H bonds in reactions with secondary phosphines, which include a more reactive P-H bond. Thus, the reactivity of 1 toward diphenylphosphine, Ph2PH, was investigated. Treatment of 1 with diphenylphosphine at room temperature for 4 h exclusively afforded a µ-phosphido complex, [Cp*3Ru2Ir(µPPh2)(µ-H)3] (5), in which the phosphido ligand bridges the Ru and Ir atoms (Scheme 1). When the reaction was monitored using 1H NMR spectroscopy at room temperature, an intermediary phosphido complex, [Cp*3Ru2Ir(µ-PPh2)(µ-H)5] (6), in which the phosphido ligand bridged the two Ru atoms, was observed in the early stage of the reaction. Although isolation of 6 was not possible due to its instability, the structure and coordination mode of the phosphorus ligand were exactly determined on the basis of 1H, 13C, and 31P NMR data. Upon leaving 6 to stand in an NMR sample tube at room temperature for 1 day, peaks related to 6 gradually disappeared, and peaks for 5 appeared.19 Accordingly, the formation of 5 most likely proceeds via the intermediate 6, that is, by the coordination of Ph2PH to one of the Ru atoms, followed by P-H bond cleavage at the neighbor(18) Ohki, Y.; Suzuki, H. Angew. Chem., Int. Ed. 2002, 41, 2994. (19) The time-conversion curves are given in the Supporting Information.

Shima et al.

ing Ru atom. Subsequent liberation of dihydrogen from 6 induces conversion into 5, in which the phosphido ligand bridges the Ir and Ru atoms. In the 1H NMR spectrum of 5, the peaks for the C5Me5 groups and the hydrido ligands appeared at δ 2.14 (15H), 2.01 (15H), 1.42 (15H), -11.76 (dd, JPH ) 20.8 Hz, JHH ) 3.2 Hz, 1H, µ-H), -14.88 (dd, JPH ) 17.2 Hz, JHH ) 3.2 Hz, 1H, µ-H), and -18.05 (m, 1H, µ-H), respectively. The doublet of doublets at δ -11.76 were assigned to the hydride bridging the two Ru atoms. The doublet of doublets at δ -14.88 correspond to the hydride bridging the Ir atom and the Ru atom bonded with the phosphido ligand. The hydrido ligand appearing at δ -18.05 bridges the Ir atom and the Ru atom that has no bonding interaction with the phosphido ligand. The significant upfield shift of the peak for the C5Me5 group observed at δ 1.42 is probably due to shielding by the endo-aromatic ring of the bridging phosphido ligand. The orientation of the endo-phenyl ring of the phosphido ligand is clearly observable in the side view in Figure 6 (vide infra). The resonance peak for the phosphido ligand was observed at δ 36.4 in the 31P NMR spectrum. The chemical shift of the phosphido ligand is comparable to that observed for the Ru-Ir heterobimetallic phosphido complex [Cp*Ru(µ-H)(µ-PPh2)(µ-η1:η2-C6H5)IrCp*] (δ 39.6).3 However, the peaks of the C5Me5 groups and the hydrido ligands appeared at δ 1.97 (30H), 1.69 (15H), and -16.13 (5H), respectively, in the 1H NMR spectrum of the intermediary complex 6. This indicates that complex 6 belongs in a Cs group and that the hydrido ligands mutually exchange their coordination sites. The upfield shift of the peak for the C5Me5 group on the Ir atom appeared at δ 1.69, implying a shielding effect by the endo-phenyl group of the phosphido ligand that bridges the two Ru atoms. The 31P NMR spectrum of 6 revealed a resonance peak for the bridging phosphido ligand at δ 149.1, and this value is comparable to that observed for a diruthenium phosphido complex, [Cp*Ru(µ-H)(µ-PPh2)(µ-η2: η2-C6H6)RuCp*] (δ 168.0).20 The structure of 5 was unequivocally established through X-ray diffraction (Figure 6). Although the structure is disordered, having either of two orientations (66:34), the phosphorus atom is observed to bridge the Ru and Ir atoms. The side view in Figure 6 clearly shows the orientation of the endo-phenyl ring, from which the shielding effect on the Cp* methyl group of Ru2 originates. The distance between the centroid of the endophenyl group and the Cp* methyl group is about 3.6 Å. The Ru1-Ir1 bond (2.9090(6) Å) is slightly longer than that observed in the Ru-Ir heterobimetallic phosphido complex [Cp*Ru(µ-H)(µ-PPh2)(µ-η1:η2-C6H5)IrCp*] (2.823(2) Å).3 The other metal-metal bond distances (2.8051(8) and 2.8103(6) Å) roughly correspond to that of a metal-metal single bond. The EAN rule applied to 5 requires a formal Ru-Ru or Ru-Ir bond order of 4/3. Dynamic Behavior of 5 in Solution. While the µ-phosphido ligand is fixed between one Ru and one Ir atom in the solid state, the µ-phosphido ligand pivots on the Ir atom in solution (Scheme 2). The fluxional behavior of the µ-phosphido ligand was initially investigated using VT-1H NMR spectroscopy. A solution of 5 in toluene-d8 was warmed from 30 to 120 °C (Figure 7). With the rise in temperature, peaks for the Cp* groups appeared at δ 2.1 and 1.4, while the hydride peaks at δ -15 and -18 both broadened. However, at the same time, new peaks assignable to 7 appeared due to the thermal instability of 5 (Vide infra). Therefore, estimation of kinetic parameters by (20) Omori, H.; Suzuki, H.; Take, Y.; Moro-oka, Y. Organometallics 1989, 8, 2270.



Scheme 1. Reaction of 1 with Diphenylphosphine

line-shape analysis was not carried out. However, this broadening of peaks strongly indicated that the phosphido ligand, which would be σ-bonded to the Ir atom and n-bonded to the Ru atom, pivots on the Ir atom. A magnetization transfer experiment using the selective inversion recovery method is suitable for analyzing the exchange process.21 A selective π pulse was applied to the resonance peak of the Cp* group at δ 1.4 at temperatures ranging from 55 to 70 °C, followed by subsequent π/2 pulses after various delay times τ (from 0 to 3.0 s).22 The kinetic parameters, enthalpy ∆Hq and entropy ∆Sq, estimated from the magnetization transfer experiment are 18(1) kcal/mol and -5(3) eu, respectively. The small absolute value of the ∆Sq indicates the intramolecular process of the pivot of the µ-phosphido ligand on the Ir atom. Thermolysis of 5. The introduction of a heteroatom into a cluster core gives rise to an electronic and steric perturbation, which would influence the reactivity. The reaction of the structurally closely related homometallic cluster [Cp*3Ru3(µ3H)2(µ-H)3] with diphenylphosphine results in the selective formation of the corresponding triply bridged phosphinidene complex [Cp*3Ru3(µ3-PPh)(µ-H)3].23 In this reaction, the phosphinidene complex is formed by way of a phosphido intermediate as a result of a P-Ph bond scission in the phosphido ligand. The P-C(aromatic) bond cleavage in the µ2-diphenylphosphido ligand has been documented in several reports so far.24 As observed in the solid-state structure of 5 shown in Figure 6, the endo-phenyl group in the bridging phosphido ligand faces the Ru2 favorable to the P-C(ipso) bond cleavage. The advantageous orientation of the phenyl group is also demonstrated in solution by the upfield shift of the 1H NMR peak of the Cp* group attached to the Ru atom. Therefore, the thermolysis of the µ2-phosphido complex 5 was investigated. When a solution of 5 in toluene was heated at 100 °C for 4 h, a µ3-phosphinidene complex, [Cp*3Ru2Ir(µ3-PPh)(µ-H)2] (7), was formed in 95% yield together with benzene (eq 5). In the 1H NMR spectrum of 7 in a deuterated aromatic solvent such as C6D6, a decrease in the integral intensity of the hydrido peaks was observed. This decline in intensity was due to a facile H/D exchange reaction between the hydrido ligands and C6D6 that took place at room temperature to afford the deuterated complex 7-dn (n ) 1, 2).25 Therefore, a deuterated aliphatic solvent such as cyclohexane-d12 was used to obtain the NMR spectrum. In the 1H NMR spectrum of 7 in C6D12, peaks for the hydrides and Cp* groups were observed at δ -8.00, 1.93, (21) (a) Kalikhman, I.; Girshberg, O.; Lameyer, L.; Stalke, D.; Kost, D. Organometallics 2000, 19, 1927. (b) Blanca, M. B.-D.; Maison, E.; Kost, D. Angew. Chem., Int. Ed. Engl. 1997, 36, 2216. (c) Mann, B. E. J. Magn. Reson. 1976, 21, 17. (d) Dahlquist, F. W.; Longmuir, K. J.; Vernet, R. B. D. J. Magn. Reson. 1975, 17, 406. (22) Details are given in the Supporting Information. (23) Okamura, R.; Matsubara, K.; Suzuki, H. Manuscript in preparation. (24) (a) Harding, M. M.; Nicholls, B. S.; Smith, A. K. J. Chem. Soc., Dalton. Trans. 1983, 1479. (b) Cherkas, A. A.; Corrigan, J. F.; Doherty, S.; MacLaughlin, S. A.; Gastel, F. v.; Taylor, N. J.; Carty, A. J. Inorg. Chem. 1993, 32, 1662. (25) When a solution of 7 in toluene-d8 was kept at room temperature for 10 min, ca. 43% of the hydride ligands were converted into the deuteride. See Supporting Information.

and 1.89, respectively, in an intensity ratio of 2:15:30. The phenyl protons of the phosphinidene ligand appeared in the ordinary aromatic region. A characteristic resonance for the µ3phosphinidene ligand was observed at δ 369.5 in the 31P NMR spectrum, and the value was comparable to those for reported µ3-PPh complexes.26 Complex 7 was formed as a result of P-C(aromatic) bond cleavage at one of the Ru centers and the subsequent elimination of benzene. The liberated benzene was detected using NMR spectroscopy. The resulting heterometallic phosphinidene complex 7 is expected to be highly reactive toward C-H bond activation because of the high electron density at the Ir center and large open space on the reverse side of the µ3-phosphinidene group with respect to the Ru2Ir plane. Preliminary experiments have shown that H/D exchange between the hydrido ligands in 7 and octane-d18 proceeds smoothly at 120 °C. Further investigation of the reaction chemistry of the heterometallic system is now in progress.

In summary, a novel heterometallic trinuclear complex 1 was synthesized in good yield via the reaction of [Cp*Ru(µH)4RuCp*] with Cp*IrH4. X-ray diffraction demonstrated that 1 had a µ3-hydrido ligand and three doubly bridging hydrido ligands at the core. The Ru-Rh analogue 2 was also synthesized by reacting (Cp*RuCl2)2 with (Cp*RhCl2)2 in the presence of NaBH4. Comparison of the 1H NMR spectra revealed the presence of structural analogy between 1 and 2. Complex 1 readily undergoes intermolecular H/D exchange with C6D6 to yield the isotopomers [Cp*3Ru2Ir(µ-H)4-n(µ-D)n] (n ) 1, 2, 3, and 4). Reactions of 1 with tertiary phosphines proceed associatively and site-selectively to afford the phosphine complexes 3a-d, in which the phosphine group is coordinated to one of the two Ru atoms as a terminal ligand. Regioselective incorporation of the substrate is likely characteristic of the heterometallic clusters. Treatment of 1 with diphenylphosphine directly affords the µ2-phosphido complex 5 by way of the isomeric µ2-phosphido complex 6, in which the phosphido ligand bridges two Ru atoms. A dynamic process of the bridging phosphido ligand in 5 was studied using VT-1H NMR spectroscopy and a magnetization transfer experiment employing a selective inversion recovery technique. The temperature-dependent NMR spectrum strongly suggests that the phosphido ligand bridging the Ir and Ru atoms is pivoted on the Ir atom. Kinetic parameters estimated through the magnetization transfer (26) (a) Huttner, G.; Schneider, J.; Mohr, G.; Seyerl, J. V. J. Organomet. Chem. 1980, 191, 161. (b) Mays, J. M.; Raithby, P. R.; Taylor, P. L.; Henrick, K. J. Organomet. Chem. 1982, 224, C45. (c) Kwek, K.; Taylor, N. J.; Carty, A. J. J. Am. Chem. Soc. 1984, 106, 4636. (d) Field, J. S.; Haines, R. J.; Mulla, F. J. Organomet. Chem. 1990, 389, 227.


Shima et al.

Figure 6. ORTEP drawing of 5 (Ir1,Ru1:Ru1a,Ir1a ) 66:34), with thermal ellipsoids at the 30% probability level. Top view (left) and side view (right). Selected bond lengths (Å) and angles (deg): Ir1-Ru2, 2.8051(8); Ru1-Ru2, 2.8103(6); Ir1-Ru1, 2.9089(6); Ir1-P1, 2.246(1); Ru1-P1, 2.250(1); Ru2-Ru1-Ir1, 58.89(1); Ru2-Ir1-Ru1, 58.71(2); Ir1-Ru2-Ru1, 62.40(2); Ir1-P1-Ru1, 80.63(4).

experiment corroborate that the dynamic process proceeds intramolecularly. Thermolysis of 5 generates the µ3-phosphinidene complex 7 together with benzene via P-C(ipso) bond cleavage. The advantageous orientation of the phenyl group on the µ-phosphido ligand for P-C(ipso) bond cleavage was confirmed by X-ray diffraction and 1H NMR spectroscopy.

Experimental Section General Procedures. All manipulations were carried out under an argon atmosphere with use of standard Schlenk techniques. Toluene and THF were distilled from sodium benzophenone ketyl prior to use. Pentane was dried over P2O5 and distilled prior to use. Methanol was dried over Mg(OMe)2 and distilled prior to use. [Cp*Ru(µ-H)4RuCp*],16 Cp*IrH4,9 (Cp*RuCl2)2,11 and (Cp*RhCl2)212 (Cp* ) η5-C5Me5) were prepared according to previously published methods. Other reagents were used as received. IR spectra were recorded using a Nicolet Avatar 360 FT-IR and a Jasco FT/IR-5000 spectrometer. 1H and 13C NMR spectra were recorded using JEOL-GSX-500, Varian Gemini300, and INOVA-400 Fourier transform spectrometers with tetramethylsilane as an internal standard. 31P NMR spectra were recorded using JEOL-GSX-500 and INOVA-400 Fourier transform spectrometers with 85% H3PO4 as the external standard. Elemental analyses were recorded on a Perkin-Elmer 2400II. X-ray Data Collection and Reduction. Crystals of 1′′, 3b, and 5 suitable for X-ray analysis were obtained from pentane (for 1′′ at -30 °C) or a solution of THF/MeOH (for 3b at 0 °C, for 5 at -30 °C). The crystals were mounted on glass fibers, and the data were collected on a Rigaku AFC-7R four-circle diffractometer employing graphite-monochromated Mo KR radiation (λ ) 0.71069 Å) in the range 5° < 2θ < 55°. The data were processed using the TEXSAN crystal structure analysis package27 on an IRIS Indigo computer. Atomic scattering factors were obtained from the standard sources. In reduction of the data, Lorentz/polarization corrections and empirical absorption corrections based on azimuthal scans were applied for each structure. (27) TEXSAN, Crystal Structure Analysis Package; Molecular Structure Corp.: The Woodlands, TX, 1985. and 1992.

Scheme 2. Fluxional Behavior of the Phosphido Complex 5

Structural Elucidation and Refinement. The structures were solved by the Patterson method (DIRDIF94,28 PATTY29) and expanded using Fourier techniques. The positions of non-hydrogen atoms were refined by full-matrix least-squares methods on F2 using the SHELXL-97 program.30 The trinuclear structures of 3b and 5 were disordered, having either of two orientations (41% and 59% occupancy for 3b and 66% and 34% occupancy for 5). The hydrogen atoms, except those bonded to metals, were placed at the calculated positions, which were then refined using a riding model. The metal-bound hydrogen atoms of 1′′, 3b, and 5 (H1A and H2A) were located on difference Fourier maps, and their positions were refined with restraint. Crystal data and analysis results are listed in Table 2. H/D Exchange with C6D6. Roto Tite NMR sample tubes were charged with 0.5 mL of C6D6 and complex 1 (15 mg, 0.019 mmol). The H/D exchange reaction was monitored at 100 °C via 1H NMR spectroscopy. The results are presented in the Supporting Information. Selective Pulse Irradiation on 5. The selective pulse technique is easily applied to slow chemical exchange in small diamagnetic molecular systems using the Varian INOVA 400 Pandora’s Box (pbox) software. This software creates radio frequency (rf) pattern files for experiments involving a shaped rf pulse sequence, which consists of a long selective π pulse, followed by a short observation pulse after various delay times, to examine the effect of the selective pulse on line intensities. Selective pulse irradiation of 5 was performed in flame-sealed NMR tubes in toluene-d8 from 55 to 70 °C using Cp* (δ 1.4) (28) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; deGelder, R.; Israel, R.; Smits, J. M. M. DIRDIF94; University of Nijmegen: The Netherlands, 1994. (29) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; GarciaGranda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. PATTY; University of Nijmegen: The Netherlands, 1992. (30) Scheldrick, G. M., SHELXL-97, Program for Crystal Structure Solution; University of Goettingen: Germany, 1997.



Figure 7. VT-1H NMR spectra of 5 (400 MHz, toluene-d8). Peaks marked with an asterisk are Cp* peaks of complex 7. Table 2. Crystallographic Data for 1′′, 3b, and 5 formula fw cryst syst space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z Dcalcd, g/cm3 temp, K µ, mm-1 (Mo KR) 2θmax reflns collected indep data indep data (I > 2σ(I)) R1 wR2 parameters GOF

1′′

3b

5 · THF

C31H51Ru2Ir 818.06 triclinic P1j (No. 2) 11.143(7) 15.510(5) 11.115(5) 93.39(4) 118.53(4) 69.23(4) 1564(1) 2 1.737 223 5.214 55.0 7494 7137 5980

C36H64IrPRu2 922.18 monoclinic P2(1)/n (No. 14) 11.085(2) 18.882(4) 18.078(4)

C42H58PRu2Ir · C4H8O 1060.30 monoclinic P2(1)/c (No. 14) 11.841(2) 15.500(3) 23.891(5)

94.49(3)

93.37(3)

3772(1) 4 1.624 296 4.373 55.0 9097 8660 6497

4377(2) 4 1.609 253 3.783 55.0 10 262 10 021 8909

0.0316 0.0782 338 1.049

0.0669 0.1785 396 1.016

0.0350 0.0883 484 1.095

according to previously published procedures.21 The data in SFigure 5 were obtained by applying the selective π pulse to the Cp* (δ 1.4) peak. [Cp*3Ru2Ir(µ3-H)(µ-H)3] (1). The dinuclear tetrahydridobridged ruthenium complex [Cp*Ru(µ-H)4RuCp*] (263.6 mg, 0.553 mmol) and mononuclear tetrahydrido-iridium complex Cp*IrH4 (174.7 mg, 0.527 mmol) were stirred in 8 mL of toluene at 100 °C for 4 h. The solution turned from red to dark brown. Subsequently, the solvent was evaporated under reduced pressure. The resulting dark brown solid was extracted with a 2:1 mixture of pentane and toluene and purified by column chromatography on Al2O3 with the same mixture of pentane and toluene. Removal of the solvent then afforded the heterobimetallic complex [Cp*Ru(µ-H)3IrCp*] (18.3 mg, 0.0323 mmol, 6%) as the first fraction. Purification with a 5:1

mixture of toluene and THF afforded the heterotrimetallic complex [Cp*3Ru2Ir(µ3-H)(µ-H)3] (1) (322.5 mg, 0.401 mmol, 76%) as a black solid. The preparation of the tetramethylethylcyclopentadienyl complex [(η5-C5Me4Et)2Cp*Ru2Ir(µ3-H)(µ-H)3] (1′) and [Cp*2(η5C5Me4Et)Ru2Ir(µ3-H)(µ-H)3] (1′′) was carried out in exactly the same manner as for the parent complex 1. 1: 1H NMR (300 MHz, C6D6, rt): 2.01 (s, 45H, C5Me5), -14.46 (brs, w1/2 ) 45.3 Hz, 4H, µ-H). 13C NMR (75 MHz, C6D6, rt): 90.6 (s, C5Me5Ir), 80.8 (s, C5Me5Ru), 13.5 (q, JCH ) 125.4 Hz, C5Me5Ru), 11.7 (q, JCH ) 127.4 Hz, C5Me5Ir). 1H NMR (300 MHz, THF-d8, rt): 2.18 (s, 15H, C5Me5Ir), 1.88 (s, 30H, C5Me5Ru), -14.82 (brs, 4H, µ-H). 13C NMR (125 MHz, THF-d8, rt): 92.0 (s, C5Me5Ir), 81.6 (s, C5Me5Ru), 14.4 (q, JCH ) 124.8 Hz, C5Me5Ru), 12.9 (q, JCH ) 126.7 Hz, C5Me5Ir). Anal. Calcd for C30H49Ru2Ir: C, 44.81; H, 6.10. Found: C, 44.79; H, 6.01. IR (KBr): 2894, 1560, 1452, 1375, 1075, 1027, 553 cm-1. 1′: 1H NMR (300 MHz, C6D6, rt): 2.49 (q, JHH ) 7.6 Hz, 4H, CH3CH2-), 2.04 (s, 12H, C5Me4EtRu), 2.00 (s, 15H, C5Me5Ir), 1.99 (s, 12H, C5Me4EtRu), 1.12 (t, JHH ) 7.6 Hz, 6H, CH3CH2-), -14.43 (brs, w1/2 ) 55.0 Hz, 4H, µ-H). 13C NMR (75 MHz, C6D6, rt): 90.4 (s, C5Me5Ir), 86.4 (s, C5Me4EtRu), 81.0 (s, C5Me4EtRu), 80.0 (s, C5Me4EtRu), 21.8 (t, JCH ) 126.2 Hz, CH3CH2-), 15.8 (q, JCH ) 125.4 Hz, CH3CH2-), 13.4 (q, JCH ) 125.0 Hz, C5Me4EtRu), 13.2 (q, JCH ) 125.4 Hz, C5Me4EtRu), 11.7 (q, JCH ) 125.4 Hz, C5Me5Ir). 1′′: 1H NMR (400 MHz, C6D6, rt): 2.37 (q, JHH ) 7.5 Hz, 2H, CH3CH2-), 2.10 (s, 6H, C5Me4EtIr), 2.01 (s, 30H, C5Me5Ru), 1.98 (s, 6H, C5Me4EtIr), 0.98 (t, JHH ) 7.5 Hz, 3H, CH3CH2-), -14.41 (brs, w1/2 ) 65.7 Hz, 4H, µ-H). 13C NMR (100 MHz, C6D6, rt): 95.3 (s, ipso-C5Me4EtIr), 90.6 (s, C5Me4EtIr), 90.0 (s, C5Me4EtIr), 80.4 (s, C5Me5Ru), 20.0 (t, JCH ) 127.8 Hz, CH3CH2-), 15.9 (q, JCH ) 125.1 Hz, CH3CH2-), 13.4 (q, JCH ) 125.1 Hz, C5Me5Ru), 11.7 (q, JCH ) 126.4 Hz, C5Me4EtIr), 11.5 (q, JCH ) 126.4 Hz, C5Me4EtIr). [Cp*3Ru2Rh(µ3-H)(µ-H)3] (2). THF (40 mL), (Cp*RuCl2)2 (81.7 mg, 0.133 mmol), and (Cp*RhCl2)2 (44.6 mg, 0.0722 mmol) were charged into a reaction flask. After the solution was cooled at -78 °C, an excess amount of NaBH4 (25 mg) was added. The solution was vigorously stirred at room temperature for 10 h. The reaction solution was again cooled to -78 °C. MeOH (5 mL) was added dropwise to the cooled solution. After warming to room temperature, the solution was stirred for 8 h. Removal of the solvent gave a purple residue. The products were extracted with toluene and purified by column chromatography on Al2O3 with a 10:1 mixture of toluene and THF. Removal of the solvent afforded the complex 2 (28.9 mg, 0.0404 mmol, 28%). The preparations of the tetramethylethylcyclopentadienyl complex [(η5-C5Me4Et)2Cp*Ru2Rh(µ3H)(µ-H)3] (2′) and [Cp*2(η5-C5Me4Et)Ru2Rh(µ3-H)(µ-H)3] (2′′) were carried out in exactly the same manner as for the parent complex 2. 2: 1H NMR (400 MHz, C6D6, rt): 2.02 (s, 30H, C5Me5Ru), 1.79 (s, 15H, C5Me5Rh), -11.98 (d, JHRh ) 28.0 Hz, 4H, µ-H). 13C NMR (100 MHz, C6D6, rt): 95.9 (d, JCRh ) 5.3 Hz, C5Me5Rh), 82.3 (s, C5Me5Ru), 13.4 (q, JCH ) 125.1 Hz, C5Me5Ru), 11.8 (q, JCH ) 125.9 Hz, C5Me5Rh). Anal. Calcd for C30H49Ru2Rh: C, 50.41; H, 6.91. Found: C, 47.29; H, 6.40. IR (ATR): 2911, 1655, 1619, 1451, 1375, 1282, 1217, 1116, 1071, 1022, 1005, 881, 704 cm-1. 2′: 1H NMR (400 MHz, C6D6, rt): 2.50 (q, JHH ) 7.4 Hz, 4H, CH3CH2-), 2.06 (s, 12H, C5Me4EtRu), 2.00 (s, 12H, C5Me4EtRu), 1.79 (s, 15H, C5Me5Rh), 1.12 (t, JHH ) 7.4 Hz, 6H, CH3CH2-), -11.97 (d, JHRh ) 26.8 Hz, 4H, µ-H). 13C NMR (100 MHz, C6D6, rt): 96.0 (d, JCRh ) 5.5 Hz, C5Me5Rh), 88.1 (s, C5Me4EtRu), 84.6 (s, C5Me4EtRu), 82.7 (s, C5Me4EtRu), 21.8 (t, JCH ) 126.5 Hz, CH3CH2-), 15.8 (q, JCH ) 126.4 Hz, CH3CH2-), 13.4 (q, JCH ) 125.1 Hz, C5Me4EtRu), 13.3 (q, JCH ) 125.1 Hz, C5Me4EtRu), 11.8 (q, JCH ) 126.5 Hz, C5Me5Rh). 2′′: 1H NMR (400 MHz, C6D6, rt): 2.32 (q, JHH ) 7.6 Hz, 2H, CH3CH2-), 2.01 (s, 30H, C5Me5Ru), 1.79 (s, 6H, C5Me4EtRh), 1.76 (s, 6H, C5Me4EtRh), 0.95 (t, JHH ) 7.6 Hz, 3H, CH3CH2-), -11.94 (d, JHRh ) 27.6 Hz, 4H, µ-H). 13C NMR (100 MHz, C6D6, rt): 101.1 (d, JCRh ) 5.3 Hz, C5Me4EtRh),

880 Organometallics, Vol. 28, No. 3, 2009 96.1 (d, JCRh ) 5.4 Hz, C5Me4EtRh), 95.7 (d, JCRh ) 5.4 Hz, C5Me4EtRh), 82.3 (s, C5Me5Ru), 19.9 (t, JCH ) 127.0 Hz, CH3CH2-), 15.0 (q, JCH ) 125.5 Hz, CH3CH2-), 13.5 (q, JCH ) 125.1 Hz, C5Me5Ru), 11.8 (q, JCH ) 126.2 Hz, C5Me4EtRh), 11.6 (q, JCH ) 126.2 Hz, C5Me4EtRh). [Cp*3Ru2Ir(PMe3)(µ-H)4] (3a). A 50 mL Schlenk tube was charged with 26.2 mg (0.0326 mmol) of 1 and 3 mL of toluene. Then 60 µL (1.58 mmol/mL in toluene, 0.0948 mmol) of PMe3 was added, and the reaction mixture was stirred at room temperature for 2 h. The color of the solution turned from black to purple. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol afforded 26.1 mg (0.0297 mmol, 91%) of 3a as a brown solid. 1H NMR (300 MHz, C6D6, rt): 2.06 (s, 15H, C5Me5), 2.02 (d, JPH ) 1.8 Hz, 15H, C5Me5), 1.85 (s, 15H, C5Me5), 1.11 (d, JPH ) 7.8 Hz, 9H, PMe3), -10.92 (d, JPH ) 17.7 Hz, 1H, µ-H), -18.96 (brs, w1/2 ) 307.7 Hz, 3H, µ-H). 13C NMR (125 MHz, C6D6, rt): 87.7 (s, C5Me5), 87.3 (d, JPC ) 2.9 Hz, C5Me5), 75.2 (s, C5Me5), 25.5 (dq, JPC ) 24.9 Hz, JCH ) 124.6 Hz, PMe3), 13.5 (q, JCH ) 125.0 Hz, C5Me5), 13.2 (q, JCH ) 125.0 Hz, C5Me5), 11.7 (q, JCH ) 125.0 Hz, C5Me5). 31P NMR (202.4 MHz, C6D6, H3PO4 85%, rt): δ 10.9. Anal. Calcd for C33H58PRu2Ir: C, 45.02; H, 6.59. Found: C, 44.82; H, 6.82. IR (KBr): 2976, 2896, 1634, 1373, 1025, 946, 536 cm-1. [Cp*3Ru2Ir(PEt3)(µ-H)4] (3b). A 50 mL Schlenk tube was charged with 30.2 mg (0.0376 mmol) of 1 and 3 mL of toluene. PEt3 (6.0 µL, 0.0406 mmol) was added, and the reaction mixture was stirred at room temperature for 2 h. The color of the solution turned from black to purple. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol afforded 33.2 mg (0.0360 mmol, 96%) of 3b as a black-purple solid. 1 H NMR (300 MHz, C6D6, rt): 2.04 (s, 15H, C5Me5), 1.97 (d, JPH ) 1.5 Hz, 15H, C5Me5), 1.82 (s, 15H, C5Me5), 1.24 (dq, JPH ) 5.7 Hz, JHH ) 7.7 Hz, 6H, PEt3), 1.04 (dt, JPH ) 13.9 Hz, JHH ) 6.8 Hz, 9H, PEt3), -11.60 (d, JPH ) 24.6 Hz, 1H, µ-H), -18.37 (brs, w1/2 ) 200.0 Hz, 1H, µ-H), -19.13 (brs, w1/2 ) 200.0 Hz, 1H, µ-H), -21.96 (brs, w1/2 ) 160.0 Hz, 1H, µ-H). 13C NMR (125 MHz, C6D6, rt): 88.0 (s, C5Me5), 86.4 (d, JPC ) 2.9 Hz, C5Me5), 74.9 (s, C5Me5), 23.4 (dt, JPC ) 21.3 Hz, JCH ) 124.4 Hz, PEt3), 13.4 (q, JCH ) 125.0 Hz, C5Me5), 13.1 (q, JCH ) 125.0 Hz, C5Me5), 11.7 (q, JCH ) 126.3 Hz, C5Me5), 9.2 (q, JCH ) 125.4 Hz, PEt3). 31P NMR (202.4 MHz, C6D6, H3PO4 85%, rt): δ 43.8. Anal. Calcd for C36H64PRu2Ir: C, 46.89; H, 6.95. Found: C, 46.69; H, 6.81. IR (KBr): 2962, 2896, 1458, 1375, 1027, 764, 708, 623, 530, 447 cm-1. [Cp*3Ru2Ir(PPh3)(µ-H)4] (3c). A 50 mL Schlenk tube was charged with 33.4 mg (0.0416 mmol) of 1 and 3 mL of toluene. PPh3 (15.3 mg, 0.0585 mmol) was added, and the reaction mixture was stirred at room temperature for 30 min. The color of the solution turned from black to purple. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol afforded 39.7 mg (0.0373 mmol, 90%) of 3c as a black-purple solid. 1 H NMR (300 MHz, C6D6, rt): 6.84-8.18 (m, 15H, Ph), 1.90 (s, 15H, C5Me5), 1.74 (s, 30H, C5Me5), -10.96 (d, JPH ) 23.7 Hz, 1H, µ-H), -19.26 (brs, w1/2 ) 281.3 Hz, 3H, µ-H). 13C NMR (75 MHz, C6D6, rt): 136.5 (s, Ph), 135.3 (d, JCH ) 155.3 Hz, Ph), 134.2 (dd, JCH ) 161.3 Hz, JPC ) 19.4 Hz, Ph), 128.8 (dd, JPC ) 7.3 Hz, obscured C6D6, Ph), 88.4 (s, C5Me5), 88.2 (d, JPC ) 2.4 Hz, C5Me5), 75.5 (s, C5Me5), 13.1 (q, JCH ) 125.0 Hz, C5Me5), 12.6 (q, JCH ) 125.0 Hz, C5Me5), 11.4 (q, JCH ) 125.8 Hz, C5Me5). 31P NMR (202.4 MHz, C6D6, H3PO4 85%, rt): δ 64.9. Anal. Calcd for C48H64PRu2Ir: C, 54.05; H, 6.01. Found: C, 54.26; H, 6.18. IR (KBr): 3056, 2978, 2890, 1649, 1628, 1477, 1435, 1373, 1091, 1027, 746, 698, 518 cm-1. [Cp*3Ru2Ir(P(OMe)3)(µ-H)4] (3d). A 50 mL Schlenk tube was charged with 32.1 mg (0.0399 mmol) of 1 and 3 mL of toluene. P(OMe)3 (8.0 µL, 0.0678 mmol) was added, and the reaction mixture was stirred at room temperature for 1 h. The color of the solution turned from black to purple. Subsequently, the solvent was

Shima et al. removed under reduced pressure. Washing the residual solid with methanol afforded 33.1 mg (0.0357 mmol, 90%) of 3d as a blackpurple solid. 1H NMR (300 MHz, C6D6, rt): 3.43 (d, JPH ) 11.1 Hz, 9H, P(OMe)3), 2.06 (d, JPH ) 2.7 Hz, 15H, C5Me5), 2.05 (s, 15H, C5Me5), 1.82 (s, 15H, C5Me5), -11.00 (d, JPH ) 25.8 Hz, 1H, µ-H), -19.23 (brs, w1/2 ) 96.0 Hz, 3H, µ-H). 13C NMR (125 MHz, C6D6, rt): 90.1 (d, JPC ) 3.6 Hz, C5Me5), 88.3 (s, C5Me5), 76.0 (s, C5Me5), 51.6 (q, JCH ) 142.4 Hz, P(OMe)3), 13.2 (q, JCH ) 125.0 Hz, C5Me5), 12.6 (q, JCH ) 125.4 Hz, C5Me5), 11.5 (q, JCH ) 126.3 Hz, C5Me5). 31P NMR (202.4 MHz, C6D6, H3PO4 85%, rt): δ 175.8. Anal. Calcd for C33H58O3PRu2Ir: C, 42.69; H, 6.25. Found: C, 42.75; H, 6.50. IR (KBr): 2978, 2892, 1615, 1456, 1378, 1081, 1023, 750, 719 cm-1. [Cp*3Ru2Rh(PEt3)(µ-H)4] (4a). An NMR sample tube was charged with 2 (11.8 mg, 0.0165 mmol) and C6D6 (0.4 mL). PEt3 (7.8 µL, 0.0825 mmol) was added to the tube at room temperature. Inspection of the sample immediately and quantitatively demonstrated the presence of complex 4a. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol at -78 °C afforded 11.3 mg (0.0135 mmol, 81%) of 4a as a black-purple solid. 1H NMR (400 MHz, C6D6, rt): 1.96 (s, 15H, C5Me5), 1.93 (d, JPH ) 1.6 Hz, 15H, C5Me5), 1.81 (s, 15H, C5Me5), 1.16-1.24 (m, 6H, PEt3), 0.94-1.06 (m, 9H, PEt3), -11.29 (d, JPH ) 25.2 Hz, 1H, µ-H), -16.18 (brs, w1/2 ) 794.4 Hz, 3H, µ-H). 13C NMR (100 MHz, C6D6, rt): 93.8 (d, JCRh ) 5.2 Hz, C5Me5), 87.6 (s, C5Me5), 75.8 (s, C5Me5), 23.8 (dt, JPC ) 22.7 Hz, JCH ) 128.3 Hz, PEt3), 13.2 (q, JCH ) 124.9 Hz, C5Me5), 13.1 (q, JCH ) 125.0 Hz, C5Me5), 12.2 (q, JCH ) 125.4 Hz, C5Me5), 9.2 (q, JCH ) 124.6 Hz, PEt3). 31P NMR (162 MHz, C6D6, H3PO4 85%, rt): δ 46.0. [Cp*3Ru2Rh(PPh3)(µ-H)4] (4b). An NMR sample tube was charged with 2 (19.3 mg, 0.0270 mmol) and C6D6 (0.4 mL). PPh3 (11.3 mg, 0.0430 mmol) was added to the tube at room temperature. Inspection of the sample immediately and quantitatively demonstrated the presence of complex 4b. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol afforded 18.4 mg (0.0188 mmol, 70%) of 4b as a blackpurple solid. 1H NMR (400 MHz, C6D6, rt): 6.86-8.20 (m, 15H, Ph), 1.80 (s, 15H, C5Me5), 1.69 (s, 15H, C5Me5), 1.68 (d, JPH ) 1.6 Hz, 15H, C5Me5), -10.68 (d, JPH ) 24.8 Hz, 1H, µ-H), -16.17 (brs, w1/2 ) 160.0 Hz, 3H, µ-H). 13C NMR (100 MHz, C6D6, rt): 123.5-136.0 (m, Ph), 94.2 (d, JCRh ) 5.5 Hz, C5Me5), 89.0 (d, JPC ) 2.3 Hz, C5Me5), 76.4 (s, C5Me5), 12.9 (q, JCH ) 125.1 Hz, C5Me5), 12.6 (q, JCH ) 125.1 Hz, C5Me5), 11.8 (q, JCH ) 125.7 Hz, C5Me5). 31P NMR (162 MHz, C6D6, H3PO4 85%, rt): δ 67.7. [Cp*3Ru2Ir(µ-PPh2)(µ-H)3] (5). A 50 mL Schlenk tube was charged with 190.1 mg (0.237 mmol) of 1 and 5 mL of toluene. PPh2H (50 µL, 0.287 mmol) was added, and the reaction mixture was stirred at room temperature for 4 h. The solution turned from black to red-brown. Removal of the solvent afforded a black residue. Crystallization from a mixture of THF and MeOH afforded 203.1 mg (0.206 mmol, 87%) of 5 as a black crystal. 1H NMR (400 MHz, C6D6, rt): 6.9-7.6 (m, 10H, Ph), 2.14 (s, 15H, C5Me5), 2.01 (s, 15H, C5Me5), 1.42 (s, 15H, C5Me5), -11.76 (dd, JPH ) 20.8 Hz, JHH ) 3.2 Hz, 1H, µ-H), -14.88 (dd, JPH ) 17.2 Hz, JHH ) 3.2 Hz, 1H, µ-H), -18.05 (m, 1H, µ-H). 13C NMR (100 MHz, C6D6, rt): 126.1-133.6 (m, Ph), 92.3 (d, JPC ) 1.5 Hz, C5Me5), 88.5 (s, C5Me5), 75.4 (s, C5Me5), 13.4 (q, JCH ) 125.1 Hz, C5Me5), 12.2 (q, JCH ) 125.4 Hz, C5Me5), 11.2 (q, JCH ) 126.1 Hz, C5Me5). 31P NMR (162 MHz, C6D6, H3PO4 85%, rt): δ 36.4. Anal. Calcd for C42H58PRu2Ir: C, 50.90; H, 5.90. Found: C, 50.91; H, 6.10. IR (KBr): 2900, 1570, 1435, 1375, 1023, 696, 476 cm-1. [Cp*3Ru2Ir(µ-PPh2)(µ-H)5] (6). An NMR sample tube was charged with 1 (25.3 mg, 0.0315 mmol) and C6D6 (0.45 mL). PPh2H (6 µL, 0.0345 mmol) was added to the tube at -78 °C. Inspection of the sample immediately and quantitatively demonstrated the presence of complex 6. 1H NMR (400 MHz, C6D6, rt): 8.40 (m,

Heterometallic Trinuclear Polyhydrido Complexes 2H, Ph), 7.0-7.5 (m, 6H, Ph), 6.78 (m, 2H, Ph), 1.97 (s, 30H, C5Me5), 1.69 (s, 15H, C5Me5), -16.13 (brs, w1/2 ) 55.6 Hz, 5H, µ-H). 13C NMR (100 MHz, C6D6, rt): 126.4-136.4 (m, Ph), 93.9 (s, C5Me5), 89.3 (s, C5Me5), 12.7 (q, JCH ) 125.4 Hz, C5Me5), 11.2 (q, JCH ) 126.1 Hz, C5Me5). 31P NMR (162 MHz, C6D6, H3PO4 85%, rt): δ 149.1. [Cp*3Ru2Ir(µ3-PPh)(µ-H)2] (7). A 50 mL Schlenk tube was charged with 203.1 mg (0.206 mmol) of 5 and 6 mL of toluene. The reaction mixture was stirred at 100 °C for 4 h. Subsequently, the solvent was removed under reduced pressure. Washing the residual solid with methanol afforded 177.1 mg (0.195 mmol, 95%) of 7 as a black solid. 1H NMR (400 MHz, C6D12, rt): 7.64 (m, 2H, Ph), 7.20 (m, 2H, Ph), 7.13 (m, 1H, Ph), 1.93 (s, 15H, C5Me5Ir), 1.89 (s, 30H, C5Me5Ru), -8.00 (d, JPH ) 9.2 Hz, 2H, µ-H). 13C NMR (100 MHz, C6D6, rt): 131.9 (dd, JCH ) 157.7 Hz, JPC ) 12.1 Hz, Ph), 127.4 (dd, JCH ) 151.2 Hz, JPC ) 9.1 Hz, Ph), 89.3 (s, C5Me5Ir), 85.9 (s, C5Me5Ru), 13.6 (q, JCH ) 125.1 Hz, C5Me5Ru), 11.8 (q, JCH ) 126.1 Hz, C5Me5Ir). 31P NMR (162 MHz, toluened8, H3PO4 85%, rt): δ 369.5. Anal. Calcd for C36H52PRu2Ir: C, 47.36; H, 5.75. Found: C, 47.28; H, 5.78. IR (KBr): 2953, 2924, 2853, 1452, 1375, 1026 cm-1.


Acknowledgment. The present work was supported by a Grant-in-Aid for Science Research on Priority Research (No. 18064007, Synergy of Elements) from Ministry of Education, Culture, Sports, Science, and Technology, Japan, and by a Grant-in-Aid for Science Research (S) (No. 18105002) from the Japan Society of the Promotion of Science. The authors are also grateful to Kanto Chemical Co., Inc., for a generous supply of pentamethylcyclopentadiene. Supporting Information Available: Text providing details of the simulation for the VT-1H NMR studies of 1, tables and plots of the H/D exchange reaction for 1, time conversion curves from 6 to 5, the VT-1H NMR studies of 4b, selective pulse irradiation of 5, H/D exchange reaction for 7, and X-ray crystallographic data for 1′′, 3b, and 5 in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org.

OM8010432

Heterometallic Trinuclear Polyhydrido Complexes Containing

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