Polyazolyl Chelate Chemistry. 13. An Osmaboratrane1

The reaction of [Os(C6H5)Cl(CO)(PPh3)2] with Na[HB(mt)3] (mt = methimazolyl) results in benzene elimination and the formation of the first osmaboratrane [B(mt)3Os(CO)(PPh3)](OsB), the crystal structure of which reveals a somewhat long transannular dative bond between osmium(0) and boron(III).