BOROLE DERIVATIVES .23. REVERSIBLE CARBONYLATION AND LEWIS BASE DEGRADATION OF THE HETEROCUBANE [RH(MU(3)-I)(C4H4BPH)](4) AND OF THE BIS(BOROLE) COMPLEX RHI(C4H4BPH)(2) AND SYNTHESIS AND STRUCTURE OF THE DINUCLEAR COMPLEX CP-ASTERISK-RH(MU-I)(3)RH(C4H4BPH)

The heterocubane [Rh(mu(3)-I)(C4H4BPh)](4) (2a) readily adds Lewis bas es to form the mononuclear products RhI(py)(2)(C4H4BPh) (4), and RhI(b py)(C4H4BPh) (7), the labile solution species, RhI(NCMe)(2)(C4H4BPh) ( 8) and RhI(CO)(2)(C4H4BPh) (9), RhI(PPh3)(2)(C4H4BPh) (11), the 1,1'-b is(diphenylphosphino)ferrocene complex RhI(dppf)(C4H4BPh) (13), and th e norbornadiene complex RhI(nbd)(C4H4BPh) (14) as well as the dinuclea r products [Rh(mu-I)(py)(C4H4BPh)](2) (5), [Rh(mu-I)(CO)(C4H4BPh)](2) (10), and the bis(diphenylphosphino)methane complex [Rh-2(mu-I)(2)(mu- dppm)(C4H4BPh)(2)] (12). The complexes 5 and 10 exist as mixtures of c is and trans isomers; the isomeric carbonyls 10 interconvert slowly at ambient temperature, while the isomeric pyridine complexes 5 show fas t interchange on the NMR time scale at 20 degrees C and low-temperatur e limiting spectra at -80 degrees C, The heterocubane also adds (RhI2C p)(2) (which acts as a Lewis base and as a Lewis acid) to produce the novel unsymmetrical dinuclear complex CpRh(mu-I)(3)Rh(C4H4BPh) (15). Complex 15 was shown by crystal structure analysis to possess a centr al trigonal-bipyramidal Rh2I3 core, capped with the Cp and the borole ligands, respectively, The bis(ligand) complex RhI(C4H4BPh)2 (3a) rea cts with excess pyridine at 20 degrees C to give RhI(py)(2)(C4H4BPh) ( 4) and the borole-pyridine adduct C4H4BPh . py (6), With CO it reacts at elevated temperature (in toluene, 80 degrees C, 7 h) to give the di carbonyl 9 with loss of one borole ligand.