The reaction of Na[H2B(mt)2] (mt = 2-mercapto, 3-methylimidazol-1-yl, methimazolyl) with [Ru(X)Cl(CO)(PPh3)n] (n = 3 X = H; n = 2 BO2C6H4, SiCl3, SiMe3) affords the complexes [Ru(X)(CO)(PPh3){κ2-H,S,S'-H2B(mt)2}]. Evidence is presented to also support the transient formation of [Ru(X)(CO)(PPh3){κ2-H,S,S'-H2B(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)(PPh3){κ2-H,S,S'-H2B(mt)2}] is similarly obtained from [OsHCl(CO)(PPh3)3] or [OsH(NCMe)2(CO)(PPh3)2]BF4. The reaction of [RuH(CO)(PPh3){κ2-H,S,S'-H2B(mt)2}] with chloroform or diphenyldiselenide provides [Ru(X)(CO)(PPh3){κ2-H,S,S'-H2B(mt)2}] (X = Cl, SePh), the latter reaction also providing traces of [Ru(SeH)(CO)(PPh3){κ2-H,S,S'-H2B(mt)2}]. Spectroscopic and structural data for the series [Ru(X)(CO)(PPh3){κ2-H,S,S'-H2B(mt)2}] are discussed in terms of perturbations on the B-H-Ru interaction by the trans-ligand X.