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)2B8H12] (1) and [(Cp*Rh)2B6H10] (2) with [Au­(PPh3)­Cl] that yielded [(Cp*Rh)2(AuPPh3)2B8H10] (3) and isomeric [(Cp*Rh)2(AuPPh3)2B6H8]
(4a,b) respectively. The reactivity of 2 with [Au­(PPh3)­Cl] was rather unusual. In 3 Au exhibits a regular μ2-bonding mode,
while in 4a,b there is a μ3-bonding with a Au–Rh bond. Further, the reactivity of 2 was performed with [Fe2(CO)9] that
permitted the isolation of 12-vertex [(Cp*Rh)2B6H6{Fe­(CO)2}2{Fe­(CO)3}2] (5), 7-vertex [(Cp*Rh)2{Fe­(CO)3}2B3H3] (6),
and the heterometallic compound [(Cp*Rh)2{Fe­(CO)3}2(μ3-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 1H, 11B, and 13C NMR spectroscopy
in solution, and the solid-state structures were established by crystallographic
analysis of 3–7.