No abstract

Syntheses of osmium analogues of acceptor pincer ( CF 3 PCP)Ru-(II) systems are reported. Treatment of [Et 4 N] 2 OsCl 6 with CF 3 PCPH at 130 °C in ethanol in the presence of Et 3 N gave the coordinatively saturated anionic carbonyl complex HNEt 3 + [( CF 3 PCP)Os(CO)Cl 2 ] − , which subsequently may be converted to cis-( CF 3 PCP)Os(CO) 2 Cl or cis-( CF 3 PCP)Os(CO) 2 H by reaction with Me 3 SiOTf or (Et 3 Si) 2 (μ-H) + B(C 6 F 5 ) 4 −, respectively. ( CF 3 PCP)Os(cod)H was obtained in modest yields by thermolysis of Os(cod)(η 3 -2-methylallyl) 2 with CF 3 PCPH in neat cod under 3 atm of H 2 at 130 °C. The alkane dehydrogenation activity of ( CF 3 PCP)Os(cod)H was examined: under identical conditions to previously studied ( CF 3 PCP)Ru(cod)H (1:1 cyclooctane/tert-butylethylene, 200 °C), the initial turnover rate for cyclooctene production was 1520 h −1 , 75% the rate observed for the ruthenium analogue, but with significantly enhanced catalyst lifetime. Acceptorless cyclodecane dehydrogenation under reflux conditions gave 125 turnovers of cyclodecenes in one hour. Spectroscopic evidence on the nature of the catalyst resting state and catalyst thermal and air stability is presented.

A series of new acceptor pincer Ru(II) complexes are reported. The carbonyl complex ((CF(3))PCP)Ru(CO)Cl(2)(-)Et(3)NH(+) is obtained from the reaction of (CF(3))PCPH with [(cod)Ru(μ-Cl)(2)](n). Chloride displacement with (CF(3))PCPH, CO, PPh(3), or C(2)H(4) gave complexes of the type ((CF(3))PCP)Ru(CO)(L)Cl, or in the case of (CF(3))PCPH, the bridged dimeric complex [((CF(3))PCP)Ru(CO)Cl](2)(μ-(CF(3))PCPH). Chloride abstraction from ((CF(3))PCP)Ru(CO)(L)Cl, L = CO or PPh(3) by (Et(3)Si)(2)(μ-H)(+)B(C(6)F(5))(4)(-) followed by Et(3)N addition produced ((CF(3))PCP)Ru(CO)(L)(H) products. Reaction of cis-((CF(3))PCP)Ru(CO)(2)Cl with (Et(3)Si)(2)(μ-H)(+)B(C(6)F(5))(4)(-) in the presence of excess CO afforded ((CF(3))PCP)Ru(CO)(3)(+). The reaction of (CF(3))PCPH with (PPh(3))(3)Ru(H)(O(2)CR) (R = Me or Ph) produced the corresponding carboxylate complexes ((CF(3))PCP)Ru(PPh(3))(O(2)CR).