Sequential Formation of [Ru (IPr) 2 (CO) H (OH2)]+ and [Ru (IPr)(η6

1976

Organometallics 2009, 28, 1976–1979

Sequential Formation of [Ru(IPr)2(CO)H(OH2)]+ and [Ru(IPr)(η6-C6H6)(CO)H]+ upon Protonation of Ru(IPr)2(CO)H(OH) (IPr ) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) Olly Saker,† Mary F. Mahon,† John E. Warren,‡ and Michael K. Whittlesey*,† Department of Chemistry, UniVersity of Bath, ClaVerton Down, Bath BA2 7AY, U.K., and SRS Station 9.8 SMX, CCLRC Daresbury Laboratory, Warrington WA4 4AD, U.K. ReceiVed December 2, 2008 Summary: Protonation of the N-heterocyclic carbene (NHC) complex Ru(IPr)2(CO)H(OH) (IPr ) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with HBF4 · OEt2 in thf affords the cationic aqua hydride complex [Ru(IPr)2(CO)H(OH2)](BF4), whereas if the solVent is changed to benzene, loss of imidazolium salt and H2O occurs to leaVe the 12e fragment [Ru(IPr)(CO)H]+, which is isolated as the cationic arene species [Ru(IPr)(η6-C6H6)(CO)H](BF4). N-Heterocyclic carbene (NHC) ligands have been shown to undergo degradation by a wide variety of reactions including intramolecular bond activation,1 migratory insertion,2 abnormal coordination,3 and ring-opening and expansion.4,5 By far the most common pathway, however, is the reductive elimination (RE) of an imidazolium salt, which has been seen for both early and late transition metal centers.6-8 While the loss of imidazolium can occur under very mild conditions, especially when hydride or alkyl groups are present as ancillary ligands (e.g., RE occurs at room temperature in [Pd(IMe4)(PR3)2(CH3)]+),7 the addition of a Brønsted acid can be used to induce the elimination reaction.8 However, some M-NHC complexes have shown a marked resilience to the addition of acid, even allowing highly acidic media to be employed for catalysis.9 Given these widely varying levels of reactivity, further studies in this area are clearly warranted. * Corresponding author. E-mail: [email protected]. † University of Bath. ‡ CCLRC Daresbury Laboratory. (1) (a) Scott, N. M.; Dorta, R.; Stevens, E. D.; Correa, A.; Cavallo, L.; Nolan, S. P. J. Am. Chem. Soc. 2005, 127, 3516–3526. (b) Burling, S.; Mahon, M. F.; Powell, R. E.; Whittlesey, M. K.; Williams, J. M. J. J. Am. Chem. Soc. 2006, 128, 13702–13703. (2) Danopoulos, A. A.; Tsoureas, N.; Green, J. C.; Hursthouse, M. B. Chem. Commun. 2003, 756–757. (3) Gru¨ndemann, S.; Kovacevic, A.; Albrecht, M.; Faller, J. W.; Crabtree, R. H. J. Am. Chem. Soc. 2002, 124, 10473–10481. (4) Galan, B. R.; Gembicky, M.; Dominiak, P. M.; Keister, J. B.; Diver, S. T. J. Am. Chem. Soc. 2005, 127, 15702–15703. (5) For two general reviews of NHC reactivity see: (a) Crudden, C. M.; Allen, D. P. Coord. Chem. ReV. 2004, 248, 2247–2273. (b) Hahn, F. E.; Jahnke, M. C. Angew. Chem., Int. Ed. 2008, 47, 3122–3172. (6) (a) McGuinness, D. S.; Green, M. J.; Cavell, K. J.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1998, 565, 165–178. (b) McGuinness, D. S.; Cavell, K. J. Organometallics 2000, 19, 4918–4920. (c) Marshall, W. J.; Grushin, V. V. Organometallics 2003, 22, 1591–1593. (d) van Rensburg, H.; Tooze, R. P.; Foster, D. F.; Slawin, A. M. Z. Inorg. Chem. 2004, 43, 2468–2470. (e) Graham, D. C.; Cavell, K. J.; Yates, B. F. Dalton Trans. 2005, 1093–1100. (f) Graham, D. C.; Cavell, K. J.; Yates, B. F. Dalton Trans. 2006, 1768–1775. (7) McGuinness, D. S.; Saendig, N.; Yates, B. F.; Cavell, K. J. J. Am. Chem. Soc. 2001, 123, 4029–4040. (8) Martin, H.; James, N. H.; Aitken, J.; Gaunt, J. A.; Adams, H.; Haynes, A. Organometallics 2003, 22, 4451–4458. (9) (a) Gru¨ndemann, S.; Albrecht, M.; Kovacevic, A.; Faller, J. W.; Crabtree, R. H. J. Chem. Soc., Dalton Trans. 2002, 2163–2167. (b) Muelhofer, M.; Strassner, T.; Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1745–1747.

Figure 1. X-ray crystal structure of Ru(IPr)2(CO)H(OH) (1). Thermal ellipsoids are set at 30% probability. Hydrogen atoms (except for RuH) have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru(1)-C(1) 1.838(2), Ru(1)-C(2) 2.0763(19), Ru(1)-C(29) 2.079(2), Ru(1)-O(2) 1.9958(18), C(2)-Ru(1)-C(29) 177.34(8), C(1)-Ru(1)-O(2) 176.94(10).

In this note, we report that the two-step protonation of the biscarbene hydroxy hydride complex Ru(IPr)2(CO)H(OH) (1, IPr ) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) in benzene results in the elimination of [IPrH]+, along with H2O, to generate the 12e fragment [Ru(IPr)(CO)H]+, which is trapped by the solvent to afford the structurally characterized cationic benzene complex [Ru(IPr)(η6-C6H6)(CO)H](BF4) (3).

Results and Discussion The 16e hydroxy hydride complex Ru(IPr)2(CO)H(OH) (1) was prepared and isolated in excellent yield (82%) as a moderately airsensitive yellow solid in a similar manner to the previously reported IMes analogue10 (IMes ) 1,3-bis(2,4,6-trimethylphenyl)imidazol2-ylidene) by metathesis of Ru(IPr)2(CO)HCl with KOH at elevated temperature. The structure of 1 (Figure 1) is in accord with related five-coordinate RuL2(CO)HX (L ) NHC, PR3; X ) F, Cl, SH, (10) Chatwin, S. L.; Mahon, M. F.; Prior, T. J.; Whittlesey, M. K. Inorg. Chim. Acta, in press. (11) (a) Chatwin, S. L.; Davidson, M. G.; Doherty, C.; Donald, S. M.; Jazzar, R. F. R.; Macgregor, S. A.; McIntyre, G. J.; Mahon, M. F.; Whittlesey, M. K. Organometallics 2006, 25, 99–110. (b) Chantler, V. L.; Chatwin, S. L.; Jazzar, R. F. R.; Mahon, M. F.; Saker, O.; Whittlesey, M. K. Dalton Trans. 2008, 2603–2614.

10.1021/om801150v CCC: $40.75  2009 American Chemical Society Publication on Web 02/18/2009

Notes

Organometallics, Vol. 28, No. 6, 2009 1977

Figure 2. X-ray crystal structure of the cation in [Ru(IPr)2(CO)H(OH2)](BF4) (2). Thermal ellipsoids are set at 30% probability. Hydrogen atoms (except for Ru-OH2) have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru(1)-C(1) 1.799(2), Ru(1)-C(2) 2.0958(18), Ru(1)-C(29) 2.1071(19), Ru(1)-O(2) 2.1805(15), C(2)-Ru(1)-C(29) 175.04(7), C(1)-Ru(1)-O(2) 177.07(10). Scheme 1

CtCR) complexes,10,11 in displaying a square-based pyramidal geometry with the hydride in an apical position trans to the vacant coordination site. The Ru-O distance of 1.9958(18) Å is slightly shorter than reported for other Ru-OH complexes.12,13 The slow addition of 1.2 equiv of HBF4 · OEt2 to a thf solution of 1 at room temperature resulted in protonation of the OH group and formation of the cationic aqua hydride complex [Ru(IPr)2(CO)H(OH2)](BF4) (2) in quantitative yield by NMR spectroscopy (Scheme 1). The Ru-H signal of 2 appeared at ca. δ -25, while the protons of the coordinated water ligand were observed as a broad, singlet resonance at δ 4.1. The change from neutral 1 to cationic 2 is reflected in the IR spectrum of the latter, which showed a single carbonyl stretch at 1923 cm-1, ca. 60 cm-1 higher in frequency than the corresponding value for 1. Isolation of the complex (73% yield) led to a determination of the X-ray crystal structure as shown in Figure 2. Both hydrogen atoms of the coordinated water ligand were located with one of them hydrogen bonded to the BF4- anion [O(2) · · · F(1), 2.66 Å; O(2)-H · · · F(1), 171°]. The coordination geometry of water is (12) Jazzar, R. F. R.; Bhatia, P. H.; Mahon, M. F.; Whittlesey, M. K. Organometallics 2003, 22, 670–683. (13) (a) Burn, M. J.; Fickes, M. G.; Hartwig, J. F.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 5875–5876. (b) Akita, M.; Takahashi, Y.; Hikichi, S.; Moro-oka, Y. Inorg. Chem. 2001, 40, 169–172. (c) Feng, Y.; Lail, M.; Barakat, K. A.; Cundari, T. R.; Gunnoe, T. B.; Petersen, J. L. J. Am. Chem. Soc. 2005, 127, 14174–14175.

worthy of comment. The angle of displacement of the metal from the plane defined by the H-O-H atoms (ε) has been used as a means of determining whether lone pair donation to a metal arises from an sp2 hybrid on O (ε ) 0° and trigonal planar O), an sp3 orbital on O (ε ) 54.7° and pyramidal O), or a p-orbital of an sp2-hybridized O atom (ε ) 90° and angular O).14 In the case of 2, ε ) 27°, intermediate between planar and pyramidal M-OH2 arrangements. The Ru-Owater distance of 2.1805(15) Å is comparable to that reported for other cationic ruthenium aqua complexes.15 As shown in Scheme 1, when the protonation of 1 was carried out in benzene rather than thf, a mixture of 2 and a second hydridecontaining species, 3, was formed. Addition of a further equiv of acid resulted in complete conversion to 3 (68% isolated yield), which was shown by multinuclear NMR spectroscopy and X-ray crystallography to be the cationic mono-NHC arene complex [Ru(IPr)(η6-C6H6)(CO)H](BF4).16 The formation of 3 results from the elimination of the imidazolium salt [IPrH]+ and H2O from 2 and trapping of the resultant low-coordinate fragment [Ru(IPr)(CO)H]+ by the reaction solvent.17 While numerous Ru(NHC)(arene) complexes exist in the literature,18 these are commonly formed by addition of NHC to an arene precursor, typically [Ru(pcymene)Cl2]2, rather than by arene trapping of an unsaturated species. The presence of a coordinated benzene ligand was established through the appearance of singet resonances at δ 5.76 and 98.5 in the 1H and 13C{1H} NMR spectra, respectively. The proton spectrum showed a single hydride resonance at δ -10.1 (this shifts to δ -9.6 when the spectrum of 3 is recorded in CD2Cl2). One imidazolylidene backbone resonance plus two doublets and two septets were observed for the iPr groups, indicating restricted rotation about the N-Caryl bonds in the carbene ligand. The IR spectrum showed a single νCO peak at 1986 cm-1. The molecular structure of 3 (Figure 3) displayed the expected three-legged piano stool geometry. A comparison of the metrics to Ru(NHC)(p-cymene) species18 revealed an unremarkable Ru-CNHC bond length (2.035(9) Å), but a relatively long Ru(1)-arenecentroid distance (1.818 Å), suggestive of a labile Ruarene coordination mode.19 This was confirmed by facile arene exchange that was found upon dissolution of 3 in C6D6. Immediate removal of the deuterated solvent and redissolution of the residue in CD2Cl2 led to a 1H NMR spectrum that consisted of a ca. 1:1 mixture of 3 and [Ru(IPr)(η6-C6D6)(CO)H](BF4) (3-C6D6). Pre(14) (a) Luo, X.-L.; Schulte, G. K.; Crabtree, R. H. Inorg. Chem. 1990, 29, 682–686. (b) Boyer, P. M.; Roy, C. P.; Bielski, J. M.; Merola, J. S. Inorg. Chim. Acta 1996, 245, 7–15. (c) Zhu, G.; Parkin, G. Inorg. Chem. 2005, 44, 9637–9639. (15) (a) Boniface, S. M.; Clark, G. R.; Collins, T. J.; Roper, W. R. J. Organomet. Chem. 1981, 206, 109–117. (b) Harding, P. A.; Robinson, S. D.; Henrick, K. J. Chem. Soc., Dalton Trans. 1988, 415–420. (c) Takahashi, Y.; Akita, M.; Hikichi, S.; Moro-oka, Y. Inorg. Chem. 1998, 37, 3186– 3194. (d) Dinelli, L. R.; Batista, A. A.; Wohnrath, K.; de Araujo, M. P.; Queiroz, S. L.; Bonfadini, M. R.; Oliva, G.; Nascimento, O. R.; Cyr, P. W.; MacFarlane, K. S.; James, B. R. Inorg. Chem. 1999, 38, 5341–5345. (16) The compound could also be formed by direct addition of 2 equiv of HBF4 · OEt2 to a benzene solution of 1. (17) Similar trapping of Ru(PPh3)2H was reported many years ago upon protonation of Ru(PPh3)4H2: Cole-Hamilton, D. J.; Young, R. J.; Wilkinson, G. J. Chem. Soc., Dalton Trans. 1976, 1995–2001. (18) (a) Jafarpour, L.; Huang, J.; Stevens, E. D.; Nolan, S. P. Organo¨ zdemir, I.; metallics 1999, 18, 3760–3763. (b) C¸etinkaya, B.; Demir, S.; O Toupet, L.; Se´meril, D.; Bruneau, C.; Dixneuf, P. H. Chem.-Eur. J. 2003, 9, 2323–2330. (c) Poyatos, M.; Mas-Marza, E.; Sanau´, M.; Peris, E. Inorg. Chem. 2004, 43, 1793–1798. (d) Poyatos, M.; Maisse-Franc¸ois, A.; Bellemin-Laponnaz, S.; Peris, E.; Gade, L. H. J. Organomet. Chem. 2006, 691, 2713–2720. (e) Prades, A.; Viciano, M.; Sanau´, M.; Peris, E. Organometallics 2008, 27, 4254–4259. (19) Arene loss from Ru(NHC)(arene) complexes has been invoked in catalytic applications: Se´meril, D.; Bruneau, C.; Dixneuf, P. H. HelV. Chim. Acta 2001, 84, 3335–3341.

1978 Organometallics, Vol. 28, No. 6, 2009

Notes

All manipulations were carried out using standard Schlenk, highvacuum, and glovebox techniques using dried and degassed solvents. Deuterated solvents were vacuum transferred from CaH2 (CD2Cl2) or potassium (THF-d8). HBF4 · OEt2 was used as received. IPr was

prepared according to the literature.21 NMR spectra were recorded on Bruker Avance 400 and 500 MHz NMR spectrometers at 298 K and referenced as follows: 1H, δ 3.58 (THF-d8), δ 5.32 (CD2Cl2); 13C, δ 67.2 (THF-d8), δ 53.7 (CD2Cl2). Elemental analyses were performed by Elemental Microanalysis Ltd., Okehampton, Devon, UK. Ru(IPr)2(CO)H(OH) (1). Ru(IPr)2(CO)HCl11b (500 mg, 0.53 mmol) and KOH (85%, 446 mg, 8.0 mmol) were suspended in dried ethanol (5 mL) in an ampule fitted with a J. Youngs PTFE valve, and the mixture was heated at 85 °C for 16 h. After cooling to ambient temperature, the volatiles were removed, the crude product extracted with benzene (3 × 5 mL), and the filtrate pumped to dryness. Hexane (10 mL) was added, the suspension vigorously stirred, and the solvent removed in Vacuo. This procedure was repeated three times to aid the removal of any residual water. The final residue was taken up in benzene (5 mL) and passed through Celite using benzene as the eluent. Concentration of the solvent gave 1 as a yellow solid. Yield: 372 mg (82%). X-ray quality crystals were grown from toluene/hexane (1:3) at 5 °C. 1H NMR (THF-d8, 500 MHz): δ 7.26 (t, JHH ) 7.50 Hz, 4H, p-CH), 7.06-7.01 (m, 8H, m-CH), 6.92 (s, 4H, NCH), 2.85 (sept, JHH ) 7.00 Hz, 4H, CHMe2), 2.80 (sept, JHH ) 7.00 Hz, 4H, CHMe2), 0.98 (d, JHH ) 6.50 Hz, 12H, CHMe2), 0.96 (d, JHH ) 6.50 Hz, 12H, CHMe2), 0.91 (d, JHH ) 6.50 Hz, 12H, CHMe2), 0.88 (d, JHH ) 6.50 Hz, 12H, CHMe2), -23.03 (s, 1H, RuH). 13C{1H} NMR: δ 206.0 (s, CO), 198.1 (s, Ru-C), 146.9 (s, o-C), 138.5 (s, i-C), 129.2 (s, p-CH), 124.1 (s, NCH), 124.0 (s, m-CH), 123.9 (s, m-CH), 29.1 (s, CHMe2), 29.0 (s, CHMe2), 26.0 (s, CHMe2), 25.9 (s, CHMe2), 23.4 (s, CHMe2), 23.0 (s, CHMe2). IR (Nujol, cm-1): 1864 (νCO). Anal. Calcd for C55H74N4O2Ru: C, 71.47; H, 8.07; N, 6.06. Found: C, 71.21; H, 8.19; N, 6.04. [Ru(IPr)2(CO)H(OH2)](BF4) (2). Ru(IPr)2(CO)H(OH) (100 mg, 0.11 mmol) was dissolved in thf (2 mL) in an ampule fitted with a J. Youngs valve. HBF4 · OEt2 (18 µL, 0.13 mmol) was added slowly via syringe to the solution, which was then stirred for 10 min at room temperature. The mixture was reduced to dryness and the residue washed with hexane (3 × 3 mL) to give 2 as a pale yellow solid. Yield: 79 mg (73%). 1H NMR (THF-d8, 500 MHz): δ 7.41 (t, JHH ) 7.50 Hz, 4H, p-CH), 7.22 (s, 4H, NCH), 7.19 (d, JHH ) 7.50 Hz, 4H, m-CH), 7.16 (d, JHH ) 7.50 Hz, 4H, m-CH), 4.10 (br, s, 2H, H2O), 2.67 (sept, JHH ) 6.50 Hz, 4H, CHMe2), 2.55 (sept, JHH ) 6.50 Hz, 4H, CHMe2), 1.01-0.98 (m, 36H, CHMe2), 0.86 (d, JHH ) 6.50 Hz, 12H, CHMe2), -24.93 (s, 1H, RuH). 13C{1H} NMR: δ 204.3 (s, CO), 190.4 (s, Ru-C), 146.8 (s, o-C), 137.0 (s, i-C), 130.5 (s, p-CH), 126.2 (s, NCH), 124.9 (s, m-CH), 124.8 (s, m-CH), 29.1 (s, CHMe2), 26.1 (s, CHMe2), 25.9 (s, CHMe2), 23.2 (s, CHMe2), 23.0 (s, CHMe2). IR (Nujol, cm-1): 1923 (νCO). Anal. Calcd for C55H75N4O2RuBF4: C, 65.27; H, 7.47; N, 5.54. Found: C, 65.27; H, 7.35; N, 5.35. [Ru(IPr)(η6-C6H6)(CO)H](BF4) (3). An ampule fitted with a J. Youngs PTFE tap and a stirrer bar was charged with a solution of Ru(IPr)2(CO)H(OH) (220 mg, 0.22 mmol) in benzene (3 mL). HBF4 · OEt2 (65 µL, 0.48 mmol) was slowly added and the mixture stirred at room temperature for 1 h. The volatiles were removed and the residue was dried under vacuum for 30 min before fresh benzene (3 mL) was added. Further HBF4 · OEt2 (33 µL, 0.24 mmol) was syringed into the solution, which was stirred for an additional 10 min, during which time it became dark brown in color with a dark precipitate present. The volatiles were again removed and the residue extracted with benzene (6 × 5 mL) and filtered by cannula. The solution was taken to dryness and washed with Et2O (3 × 5 mL) and hexane (3 × 5 mL) to give a pale brown solid. Yield: 99 mg (68%). Small X-ray quality crystals were grown from a saturated CH2Cl2 solution layered with hexane. 1H NMR (CD2Cl2, 500 MHz): δ 7.67 (t, JHH ) 7.50 Hz, 2H, p-CH), 7.46 (d, JHH ) 7.50 Hz, 2H, m-CH), 7.45 (d, JHH ) 7.50 Hz, 2H, m-CH), 7.31 (s, 2H, NCH), 5.76 (s, 6H, C6H6), 2.48 (sept, JHH ) 6.50 Hz, 2H, CHMe2), 2.35 (sept, JHH ) 6.50 Hz, 2H, CHMe2), 1.39-1.36 (m, 12H, CHMe2), 1.20 (d, JHH ) 6.50 Hz, 6H, CHMe2),

(20) Yi, C. S.; Lee, D. W.; He, Z.; Rheingold, A. L.; Lam, K.-C.; Concolino, T. E. Organometallics 2000, 19, 2909–2915.

(21) Jafarpour, L.; Stevens, E. D.; Nolan, S. P. J. Organomet. Chem. 2000, 606, 49–54.

Figure 3. X-ray crystal structure of one of the cations and one of the anions in the asymmetric unit of [Ru(IPr)(η6-C6H6)(CO)H](BF4) (3). Thermal ellipsoids are illustrated at 30% probability. Solvent and hydrogen atoms (except for Ru-H and NHC backbone hydrogens) have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru(1)-C(10) 1.832(11), Ru(1)-C(12) 2.035(9), Ru(1)-Ccentroid 1.818, C(10)-Ru(1)-C(12) 85.0(4), C(10)-Ru(1)-Ccentroid 133.3, C(12)-Ru(1)-Ccentroid 133.6.

liminary studies of the reaction of 1 with HBF4 · OEt2 in toluene rather than benzene revealed formation of the analogous toluene complex [Ru(IPr)(η6-C6H5CH3)(CO)H](BF4) (4), which was characterized through the appearance of five multiplet resonances between δ 6.0 and 5.4 and a singlet at δ 2.08 in the 1H NMR spectrum (in CD2Cl2), which integrated in a ratio of 1:1:1:1:1:3. The hydride resonance of 4 appeared in a similar position to that for 3 (δ -9.9). The toluene ligand also proved to be substitutionally labile. Thus, a 1:1 mixture of (3-C6D6):4 was detected within a minute of dissolving 4 in C6D6 at room temperature, with conversion to the former complete after 15 min. In conclusion, we have found that the protonation of the NHC hydroxy hydride complex Ru(IPr)2(CO)H(OH) by HBF4 · OEt2 leads to the clean formation of solvent-dependent products, with the cationic aqua hydride complex [Ru(IPr)2(CO)H(OH2)](BF4) (2) generated in thf and [Ru(IPr)(η6-C6H6)(CO)H](BF4) (3) formed in benzene. The formation of 3 provides an interesting comparison to the findings of Yi and co-workers, who showed that addition of HBF4 · OEt2 to the phosphine hydride chloride complex Ru(PCy3)2(CO)HCl in C6H6 afforded an effective alkene hydrogen catalyst as a result of [HPCy3]+ loss and formation of some form of cationic adduct of the resulting 14e fragment Ru(PCy3)(CO)HCl.20 Given our results, we postulate that this species could in fact be the arene complex [Ru(PCy3)(η6-C6H6)(CO)H](Cl/BF4), although slow degradation to the tetrameric compound [Ru(PCy3)(CO)]4(µ-Cl)6(µ4-Cl) prevented proper characterization.

Experimental Section

Notes

Organometallics, Vol. 28, No. 6, 2009 1979 Table 1. Crystal Data and Structure Refinement for Compounds 1-3 empirical formula fw T/K wavelength cryst syst space group a/Å b/Å c/Å R/deg β/deg γ/deg U/Å3 Z Dc/gcm-3 µ/mm-1 F(000) cryst size/mm θ min., max. for data collection index ranges

reflns collected indep reflns, Rint reflns obsd (>2σ) absorp corr max., min. transmn data/restraints/params goodness-of-fit on F2 final R1, wR2 [I > 2σ(I)] final R1, wR2 (all data) largest diff peak, hole/e Å-3 abs struct param

1

2

3

C61H88N4O2Ru 1010.42 150(2) 0.71073 orthorhombic P212121 12.9870(1) 20.6070(2) 21.2510(2) 90 90 90 5687.26(9) 4 1.180 0.319 2168 0.20 × 0.15 × 0.15 3.53, 27.51 -16 e h e 16; -26 e k e 26; -27 e l e 27 109 458 13 030, 0.0635 10 974 0.995 none 13 030/2/637 1.057 0.0339, 0.0736 0.0477, 0.0793 0.739, -0.625, 0.00(1)

C55H75BF4N4O2Ru 1012.07 150(2) 0.71073 orthorhombic Pbca 20.7380(1) 21.0220(1) 24.9520(2) 90 90 90 10877.93(11) 8 1.236 0.344 4272 0.40 × 0.25 × 0.15 3.87, 27.48 -26 e h e 26; -27 e k e 27; -32 e l e 32 176 301 12 440, 0.0950 9490 0.997 multiscan 12 440/8/652 1.041 0.0335, 0.0846 0.0531, 0.0945 0.631, -0.633,

C34.25H43.50BCl0.5F4N2Ru 704.82 120(2) 0.69430 triclinic P1j 9.704(4) 18.093(8) 19.237(8) 91.981(5) 96.119(5) 93.590(5) 3349(2) 4 1.398 0.560 1458 0.04 × 0.02 × 0.02 3.98, 24.41 -11 e h e 11; -21 e k e 21; -22 e l e 22 24 891 11 455, 0.1058 6357 0.967 multiscan 11 455/37/831 1.051 0.0816, 0.1845 0.1551, 0.2112 1.536, -1.097,

1.10 (d, JHH ) 6.50 Hz, 6H, CHMe2), -9.64 (s, 1H, RuH). 13C{1H} NMR: δ 196.1 (s, CO), 172.7 (s, Ru-C), 146.1 (s, o-C), 146.0 (s, o-C), 136.5 (s, i-C), 131.8 (s, p-CH), 126.4 (s, NCH), 125.1 (s, m-CH), 125.0 (s, m-CH), 98.5 (s, C6H6), 29.5 (s, CHMe2), 29.1 (s, CHMe2), 26.4 (s, CHMe2), 25.7 (s, CHMe2), 22.7 (s, CHMe2), 22.2 (s, CHMe2). IR (Nujol, cm-1): 1986 (νCO). ESI-TOF MS: [M - C6H6]+ m/z ) 519.1966 (theoretical m/z ) 519.1951). Dissolution of 3 (ca. 12 mg) in C6D6 (0.6 mL) in a J. Youngs resealable NMR tube followed by immediate removal of the solvent and redissolution of the residue in CD2Cl2 allowed spectroscopic characterization of 3-C6D6. NMR data for isotopically shifted resonances: 1H NMR (CD2Cl2, 500 MHz): δ -9.65 (s, 1H, RuH). 13C{1H} NMR: δ 98.1 (1:1:1 triplet, JCD ) 27 Hz, C6D6). [Ru(IPr)(η6-C6H5CH3)(CO)H](BF4) (4). An NMR tube fitted with a J. Youngs PTFE tap was charged with a solution of Ru(IPr)2(CO)H(OH) (15 mg, 0.015 mmol) in toluene (0.5 mL). HBF4 · OEt2 (4.4 µL, 0.033 mmol) was added and the mixture shaken at room temperature for 15 min. The volatiles were removed and the residue was dried under vacuum for 30 min before a further 0.5 mL of toluene and 2.3 µL (0.017 mM) of HBF4 · OEt2 were added. The solution was shaken for 15 min and then reduced to dryness to give 4 as a brown solid, which was spectroscopically characterized. Selected 1 H NMR (CD2Cl2, 500 MHz): δ 5.97 (t, JHH ) 6.50 Hz, 1H, p-CH), 5.63 (d, JHH ) 6.50 Hz, 1H, o-CH), 5.58 (d, JHH ) 6.50 Hz, 1H, o-CH), 5.56 (t, JHH ) 6.50 Hz, 1H, m-CH), 5.49 (t, JHH ) 6.50 Hz, 1H, m-CH), 2.08 (s, 3H, C6H5CH3), -9.87 (s, 1H, RuH). X-ray Crystallography. Single crystals of compounds 1 and 2 were analyzed using a Nonius Kappa CCD diffractometer, while 3 was measured at Station 9.8 of the CLRC at Daresbury. Data collection and refinement details are summarized in Table 1. The structures were solved using SHELXS-9722 and refined using full-matrix least-squares in SHELXL-97.22 In 1, it was noted that the hydride is split over two sites, but both fractions were readily located and refined at 1.6 Å from the ruthenium center. The OH proton however could not be reliably

located and was therefore omitted from the refinement. The asymmetric unit in this structure was also seen to contain one molecule of hexane. The hydrogen atoms attached to the ligated water in 2 were located and refined at a distance of 0.9 Å from O2. As mentioned previously, one of these was involved in hydrogen bonding to the anion. It was not possible to reliably locate the hydride ligand in this structure, which may reflect the possibility of disorder. This thesis is also supported by 65:35 disorder in the C12 and C13 positions. The asymmetric unit in 3 consists of two cations, two anions, and one molecule of dichloromethane. One of the tetrafluoroborate anions exhibits 1:1 disorder of three fluorines, which was successfully modeled subject to inclusion of some distance and ADP restraints. The hydrides were located and refined as for 1. In parallel with the hydrogen bonding observed in 2, there is evidence for the presence of C-H · · · F interactions between the cations and anions in 3. Crystallographic data for compounds 1-3 have been deposited with the Cambridge Crystallographic Data Centre as supplementary publications CCDC 711770-711772. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: (+44) 1223 336033, e-mail: [email protected]].

Acknowledgment. Johnson Matthey plc is acknowledged for the kind loan of hydrated ruthenium trichloride, and EPSRC is thanked for financial support for O.S. Supporting Information Available: CIF file giving X-ray crystallographic data for 1-3. This material is available free of charge via the Internet at http://pubs.acs.org. OM801150V (22) (a) Sheldrick, G. M. Acta Crystallogr. 1990, 467-473, A46. (b) Sheldrick, G. M. SHELXL-97, computer program for crystal structure refinement; University of Go¨ttingen, 1997.