Hydride, Borohydride, and Dinitrogen Pincer Complexes of Ruthenium

Reactions of chlorides RuCl(CO)(PCP) ( 1; PCP = [2,6-(CH 2 PBu t 2 ) 2 C 6 H 3 ] - ) and RuHCl[1,3-(CH 2 PBu t 2 ) 2 C 6 H 4 ] ( 2 ) with [Bu 4 N]BH 4 in ethanol afforded the hydrides RuH(CO)(PCP) ( 3 ) and [RuH(PCP)] 2 (μ-N 2 ) ( 5a ), respectively. Complex 5a exists in equilibrium with the dinitrogen species [RuH(N 2 )(PCP)](μ-N 2 )[RuH(PCP)] ( 5b ) and RuH(N 2 )(PCP) ( 5c ) in solution under N 2 . Reaction of 1 and [Bu 4 N]BH 4 in ether resulted in formation of the two isomeric borohydride complexes Ru(η 2 -BH 4 )(CO)(PCP) ( 4a ) and RuH(CO)[1-BH 3 -2,6-(CH 2 PBu t 2 ) 2 C 6 H 3 ] ( 4b ). Single-crystal X-ray structures of 3, 4b, and 5a,b are reported.