Ruthenium(II) Complexes Containing Bis(2-(diphenylphosphino)phenyl) Ether and Their Catalytic Activity in Hydrogenation Reactions Ramalingam Venkateswaran, † Joel T. Mague, ‡ and Maravanji S. Balakrishna* ,† Phosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400 076, India, and Department of Chemistry, Tulane UniVersity, New Orleans, Lousiana 70118 Received September 20, 2006 The half-sandwich complexes [(η 5 -C 5 H 5 )RuCl(DPEphos)] (1) and [{(η 6 -p-cymene)RuCl 2 } 2 (µ-DPEphos)] (2) were synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride trihydrate and cyclopentadiene and with [(η 6 -p-cymene)RuCl 2 ] 2 , respectively. Treatment of DPEphos with cis-[RuCl 2 - (dmso) 4 ] afforded fac-[RuCl 2 (κ 3 -P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine, 2,2′-bipyridine, 4,4′-bipyridine, and PPh 3 to yield trans,cis-[RuCl 2 (DPEphos)(C 5 H 5 N) 2 ](4), cis,cis-[RuCl 2 (DPEphos)- (2,2′-bipyridine)] (5), trans,cis-[RuCl 2 (DPEphos)(µ-4,4′-bipyridine)] n (6), and mer,trans-[RuCl 2 (κ 3 -P,P,O-DPEphos)- (PPh 3 )] (7), respectively. Refluxing [(η 6 -p-cymene)RuCl 2 ] 2 with DPEphos in moist acetonitrile leads to the elimination of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl 2 (DPEphos)(H 2 O)(CH 3 CN)] (8). The structures of the complexes 1-5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of these complexes for the hydrogenation of styrene is studied. Introduction The chemistry of Ru II complexes incorporating phosphorus donor ligands has received considerable attention in recent years since the discovery of Noyori’s BINAP-RuX 2 catalysts, which developed a practical way to prepare an intermediate for the synthesis of prostaglandin and carbapenam antibiot- ics, 1 and Grubb’s L 2 X 2 RudCHR catalysts, leading to im- pressive development in the field of olefin metathesis. 2 Ru II complexes containing nitrogen donor ligands have acquired considerable significance in supramolecular chemistry, 3 photoredox processes for solar energy conversions, biosen- sors, and catalysis. 4 Phosphorus-, nitrogen-, and sulfur- containing ligands such as PPh 3 , dppm, dppe, pyridines, and dmso associated with Ru are well documented, 5 whereas the ruthenium chemistry of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) has not been studied. The large bite angle DPEphos with a relatively rigid diphenyl ether backbone and containing both oxygen and phosphorus donor sites 6 offers different coordination modes through the possibility of behaving as a hemilabile ligand, thereby providing the promise of rich coordination and organometallic chemistry with various metal centers. van Leeuwen and co-workers 7 and others 8 have extensively studied the coordination chem- istry and catalytic utility of DPEphos. 9 As part of our research interest, 10 herein we report the syntheses of ruthenium * To whom correspondence should be addressed. E-mail: krishna@ chem.iitb.ac.in. Fax: +91-22-5172-3480. † Indian Institute of Technology. ‡ Tulane University. (1) (a) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40, 40-73. (b) Noyori, R. Angew. Chem., Int. Ed. 2002, 41, 2008-2022. (c) Mikami, K.; Korenaga, T.; Ohkuma, T.; Noyori, R. Angew. Chem., Int. Ed. 2000, 39, 3707-3710. (2) (a) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413-4450. (b) Trnka, T. M.; Day, M. W.; Grubbs, R. H. Organometallics 2001, 20, 3845-3847. (3) Cronin, L. Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem. 2005, 101, 348-374. (4) (a) Ward, M. D. Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem. 2005, 101, 649-672. (b) Chelucci, G.; Thummel, R. P. Chem. ReV. 2002, 102, 3129-3170. (5) (a) Fache, F.; Schulz, E.; Tommasino, M. L.; Lemaire, M. Chem. ReV. 2000, 100, 2159-2231. (b) Tang, W.; Zhang, X. Chem. ReV. 2003, 103, 3029-3069. (c) Drozdzak, R.; Allaert, B.; Ledoux, N.; Dragutan, I.; Dragutan, V.; Verpoort, F. Coord. Chem. ReV. 2005, 249, 3055- 3074. (6) Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Acc. Chem. Res. 2001, 34, 895-904. (7) (a) Kranenburg, M.; van der Burgt, Y. E. M.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J. Organometallics 1995, 14, 3081-3089. (b) van Haaren, R. J.; Zuidema, E.; Fraanje, J.; Goubitz, K.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; van Strijdonck, G. P. F. C. R. Chim. 2002, 5, 431-440. (c) Zuideveld, M. A.; Swennenhuis, B. H. G.; Boele, M. D. K.; Guari, Y.; van Strijdonck, G. P. F.; Reek, J. N. H.; Kamer, P. C. J.; Goubitz, K.; Fraanje, J.; Lutz, M.; Spek, A. L.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans. 2002, 2308-2317. Inorg. Chem. 2007, 46, 809-817 10.1021/ic061782l CCC: $37.00 © 2007 American Chemical Society Inorganic Chemistry, Vol. 46, No. 3, 2007 809 Published on Web 01/06/2007