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 ( 1a ), 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 exo -polyhedral role, while the {M‘(CO) 2 } units now occupy a site within the cluster. Compounds 2 convert to [N(PPh 3 ) 2 ][1,3-{M(CO) 4 }-3-( μ -H)-1,1-(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 (PEt 3 )}-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(PPh 3 ) 2 ][1,3-{Re(CO) 3 (NH 2 C 6 H 4 Me-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.