Reactions of sodium tetrahydroborate and cyanotrihydroborate with ruthenium(II) and (III) systems in the presence of tertiary phosphines

The first tetrahydroborato–phosphine complexes of Ru(II) are reported and a number of new cyanotrihydroborato and hydrido complexes of Ru(II) are also recorded. Among the more interesting complexes prepared are RuH(BH 4 )(PPh 3 ) 3 , RuH(BH 4 )(CO)(PPh 3 ) 3 , RuH(BH 4 )(CO) 2 [P(C 6 H 11 ) 3 ] 2 , and RuH(BH 3 CN)(CO) 2 (DBP) 2 (DBP is the ligand 5-phenyl-5H-dibenzophosphole). It is shown that unlike Rh(III), Ru(III) is not stabilized by phosphine complex formation towards reduction by tetrahydroborate ion although Ru(II) is not reduced further by this reagent. A stepwise mechanism is proposed for the reduction of phosphine–dichloro Ru(II) systems to hydrido–tetrahydroborato and dihydro complexes. Nuclear magnetic resonance studies show that certain of the products are mixtures of geometrical isomers and, in several cases, detailed nmr assignments are made.