Triosmium and triruthenium clusters containing the 4-methylthiazolide ligand: crystal structures of [Os3(µ-H)(CO)10(µ-2,3-η2-CNCMeCHS)], [Os3(µ-H)(CO)9(µ-2,3-η2-CNCMeCHS)(PPh3)] and [Os3(µ-H)(CO)8(µ-2,3-η2-CNCMeCHS)(PPh3)2]