Construction of Metal Butterflies on a Metallacarborane Scaffold. 1. Synthesis and Structures of Bimetallic Precursors

Treatment of [N(PPh3)2][NEt4][1,1,1-(CO)3-2-Ph-closo-1,2-MCB9H9] (M = Mn (1a), Re (1b)) with sources of the cations {M‘(CO)2}+ (M‘ = Ir, Rh) affords the bimetallic species [N(PPh3)2][1,3,6-{M(CO)3}-3,6-(μ-H)2-1,1-(CO)2-2-Ph-closo-1,2-M‘CB9H7] (M = Re, M‘ = Ir (2a), Rh (2b); M = Mn, M‘ = Ir (2c), Rh (2d)). In these, the {M(CO)3} fragment, formerly a cluster vertex, has assumed an exo-polyhedral role, while the {M‘(CO)2} units now occupy a site within the cluster. Compounds 2 convert to [N(PPh3)2][1,3-{M(CO)4}-3-(μ-H)-1,1-(CO)2-2-Ph-closo-1,2-M‘CB9H8] (M = Re, M‘ = Ir (3a), Rh (3b); M = Mn, M‘ = Ir (3c), Rh (3d)) by deliberate CO addition or by CO scavenging. Reaction of 2b with PEt3 gives [N(PPh3)2][1,3-{Re(CO)3(PEt3)}-3-(μ-H)-1,1-(CO)2-2-Ph-closo-1,2-RhCB9H8] (4), which has a mirror-symmetric structure, whereas 2a with NH2C6H4Me-1,4 affords [N(PPh3)2][1,3-{Re(CO)3(NH2C6H4Me-1,4)}-3-(μ-H)-1,1-(CO)2-2-Ph-closo-1,2-IrCB9H8] (5), which is asymmetric. The structures of 2b, 3b, and 5 have been confirmed by X-ray diffraction studies.