Construction of metal butterflies on a metallacarborane scaffold. 1. Synthesis and structures of bimetallic precursors

Treatment of [N(PPh 3 ) 2 ][NEt 4 ][1,1,1-(CO) 3 -2-Ph-closo-1,2-MCB 9 H 9 ] (M = Mn (la), Re (1b)) with sources of the cations {M'(CO) 2 } + (M' = Ir, Rh) affords the bimetallic species [N(PPh 3 ) 2 ][1,3,6-(M-(CO)3}-3,6-(μ-H)2-1,1-(CO)2-2-Ph-closo-1,2-M'CB 9 H 7 ] (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 exopolyhedral role, while the {M'(CO) 2 } units now occupy a site within the cluster. Compounds 2 convert to [N(PPh3)2][l,3-{M(CO)4}-3-(μ-H)-l,l-(CO)2-2-Ph-closo-1,2-M'CB 9 H 8 ] (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 PEt 3 gives [N(PPh 3 ) 2 ][1,3-{Re(CO)3(PEt3)}-3-(μ-H)-1,1-(CO)2-2-Ph-closo-1,2-RhCB 9 H 8 ] (4), which has a mirror-symmetric structure, whereas 2a with NH 2 C 6 H 4 Me-1,4 affords [N(PPh3)2][l,3-{Re(CO)3-(NH2C6H4Me-1,4)}-3-(μ-H)-1,1-(CO)2-2-Ph-closo-1,2-IrCB 9 H 8 ] (5), which is asymmetric. The structures of 2b, 3b, and 5 have been confirmed by X-ray diffraction studies.