Synthesis and Reactivity of Ru(II)/Chloro/Hydrido/Carbonyls with Cis Bulky Phosphines: An Unsaturated Ru(II) Monohydride

[RuCl 2 (CO) 2 (d t bpe)], d t bpe = t Bu 2 PCH 2 CH 2 P t Bu 2 is synthesized as a mixture of two isomers and is converted to [RuHCl(CO) 2 (d t bpe)], then [Ru(H) 2 (CO) 2 (d t bpe)]. The chloride trans to hydride in [RuHCl(CO) 2 (d t bpe)] can be replaced by BF 4 - or PF 6 -, and reaction with NaB(3,5-(CF 3 ) 2 C 6 H 3 ) 4 gives authentic, five-coordinate [RuH(CO) 2 (d t bpe)] +, characterized structurally by X-ray diffraction, which reveals the lack of agostic interactions. [Ru(H) 2 (CO) 2 (d t bpe)] reacts under mild conditions with CO to give [Ru(CO) 3 (d t bpe)], with ethylene to give C 2 H 6 and [Ru(C 2 H 4 )(CO) 2 (d t bpe)], and with D 2 to give some [Ru(H)(D)(CO) 2 (d t bpe)]. These results are interpreted in terms of relatively facile dissociation of one end of d t bpe from the metal.