Reactivity of Dirhodium Analogues of Octaborane-12 and Decaborane-14 towards Transition-Metal Moieties

Building upon the key results of our earlier work on rhodaboranes, we continue to explore the chemistry of two nido-rhodaborane clusters, [(Cp*Rh)(2)B8H12] (1) and [(Cp*Rh)(2)B6H10] (2) with [Au(PPh3)Cl] that yielded [(Cp*Rh)(2)(AuPPh3)(2)B8H10] (3) and isomeric [(Cp*Rh)(2)(AuPPh3)(2)B6H8] (4a,b) respectively. The reactivity of 2 with [Au(PPh3)Cl] was rather unusual. In 3 Au exhibits a regular mu(2)-bonding mode, while in 4a,b there is a mu(3)-bonding with a Au-Rh bond. Further, the reactivity of 2 was performed with [Fe-2(CO)(9)] that permitted the isolation of 12-vertex [(Cp*Rh)(2)B6H6{Fe(CO)(2)}(2){Fe(CO)(3)}(2)] (5), 7-vertex [(Cp*Rh)(2){Fe(CO)(3)}(2)B3H3] (6), and the heterometallic compound [(Cp*Rh)(2){Fe(CO)(3)}(2)(mu(3)-CO)(2)] (7) in moderate to good yields. The cluster core of 5 consists of a 10-vertex isocloso geometry with two additional {Fe(CO)(3)} vertices capping two trigonal faces. Cluster 6 contains a capped-octahedral geometry, where one of the boron atoms is in the capping position. All of the compounds have been characterized by IR and H-1, B-11, and C-13 NMR spectroscopy in solution, and the solid-state structures were established by crystallographic analysis of 3-7.