Isomeric clusters [HOs3(CO)10(C18H11N6)] obtained from the reaction of [Os3(CO)10(CH3CN)2] with new tris-pyridyl-1,2,4-triazines

The new tris-pyridyl-as-triazines 3-(3-pyridyl)-5,6-bis(2-pyridyl)-1,2,4-triazine (3TPT) and 3-(4-pyridyl)-5,6-bis(2-pyridyl)-1,2,4-triazine (4TPT) have been synthesized from the corresponding pyridyl-amidrazone and 2,2′-pyridyl in good yields. The reaction of 3TPT with [Os3(CO)10(CH3CN)2] at room temperature gives the new compounds [HOs3(CO)9(C18H11N6)] (1 and 2) by orthometallation of the 3-pyridyl ring at the 2- and 6-positions. The reaction of 4TPT with [Os3(CO)10(CH3CN)2] gives only one derivative, the isomer [HOs3(CO)9(C18H11N6)] (3) by orthometallation of the 4-pyridyl ring. In all cases, C–H activation of the 3-pyridyl or 4-pyridyl is favored, so the 2-pyridyl substituents remain uncoordinated.