(Cyclopentadienyl)metalladicarbollides 3-(η-C5R 5)-3,1,2-MC2B9H11 (M = Co, Rh, Ir): Synthesis, electrochemistry, and bonding

Metallacarboranes 3-(η-C5R5)-3,1,2-MC 2B9H11 (1a: M = Co, R = H; 1b: M = Co, R = Me; 2a: M = Rh, R = H; 2b: M = Rh, R = Me; 3a: M = Ir, R = H; 3b: M = Ir, R = Me) were obtained by reactions of Tl[Tl(η-7,8-C2B9H 11)] with [(η-C5R5)MX2] 2 (X = Cl, I) or [CpM(MeCN)3]2+. The structures of 2a and 3a were determined by X-ray diffraction. The electrochemical investigation of complexes 2a,b and 3a,b shows that they undergo the partially reversible M(III)/M(II) electron addition followed by the irreversible M(II)/M(I) reduction. Such a path is quite reminiscent of that occurring for the isolobal and isoelectronic monocations [(η-C5R 5)MCp]+ (M = Rh, Ir; R = H, Me). An electrochemical comparison is made also with respect to the cobalt derivatives 1a,b. DFT calculations of the redox potentials and the respective geometrical changes were performed. Metal-ligand bonding in 1a, 2a and 3a was analyzed by energy decomposition analysis. © 2012 Elsevier B.V. All rights reserved.