Dihydrobis(methimazolyl)borato complexes of ruthenium and osmium

The reaction of Na[H 2 B(mt) 2 ] (mt = 2-mercapto, 3-methylimidazol-1-yl, methimazolyl) with [Ru(X)Cl(CO)(PPh 3 ) n ] (n = 3 X = H; n = 2 BO 2 C 6 H 4 , SiCl 3 , SiMe 3 ) affords the complexes [Ru(X)(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }]. Evidence is presented to also support the transient formation of [Ru(X)(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }] (X = CH[double bond, length as m-dash]CHPh, Ph) via a similar strategy, although these are unstable. The osmium complex [OsH(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }] is similarly obtained from [OsHCl(CO)(PPh 3 ) 3 ] or [OsH(NCMe) 2 (CO)(PPh 3 ) 2 ]BF 4 . The reaction of [RuH(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }] with chloroform or diphenyldiselenide provides [Ru(X)(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }] (X = Cl, SePh), the latter reaction also providing traces of [Ru(SeH)(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }]. Spectroscopic and structural data for the series [Ru(X)(CO)(PPh 3 ){κ 2 -H,S,S'-H 2 B(mt) 2 }] are discussed in terms of perturbations on the B-H-Ru interaction by the trans-ligand X.