Macropolyhedral boron-containing cluster chemistry. Isolation and structure of the twenty-one-vertex globular cluster compound [(η5-C5Me5)3Ir3B18H15(OH)]

Reaction of syn-B18H20 with [(η5-C5Me5)IrCl2]2 and base results in multiple metal-centre addition, allied with oxidative cluster closure by multiple dihydrogen loss, giving the twenty-one-vertex globular cluster compound [(η5-C5Me5)3Ir3B18H15(OH)] based on twelve-vertex closo {IrB11} and isonido {Ir2B10} clusters fused with a common five-atom {IrB4} unit that contains a central tetrahedral {IrB3} core.