Borole Derivatives. 24. Synthesis of Cationic (Arene)(phenylborole)rhodium Complexes. Structures of the Trinuclear Complex (η⁵-C₄H₄BPh)Rh(μ₃-I)₃-Rh(μ,η⁵:η⁶-C₄H₄BPh)Rh(η⁵-C₄H₄BMe)·CH₂Cl₂ and of the Polymeric catena-(μ,η⁵:η⁶-1-Phenylborole)rhodium Tetrafluoroborate

The heterocubane [Rh(μ₃-I)(C₄H₄BPh)]₄ (1) reacts with Ag⁺ salts in acetonitrile to give the labile salt [Rh(NCMe)₃(C₄H₄BPh)]BF₄ (2). This salt 2 reacts with hexamethylbenzene (hmb) to give the arene complex [Rh(C₄H₄BPh)(hmb)]BF₄ (3), and with mesitylene [Rh(1,3,5-C₆H₃Me₃)(C₄H₄BPh)]BF₄ (4) is obtained. Complex 2 loses acetonitrile under vacuum to produce the polymeric salt catena-[{Rh(μ,η⁵:η⁶-C₄H₄BPh)}BF₄]_x (5). Insight into the essential structural features of this polymer provided its radial distribution function obtained from a wide-angle X-ray scattering experiment. When treated with acetonitrile, complex 5 regenerates 2 and with pyridine affords [Rh(py)₃((C₄H₄BPh)]BF₄ (6). Crystallization from a solution of [Rh(μ₃-I)(C₄H₄BPh)]₄ (1) and the corresponding methylborole complex [Rh(μ₃-I)(C₄H₄BMe)]₄ (1/1) in CH₂Cl₂ produces the trinuclear complex (η⁵-C₄H₄BPh)Rh(μ₃-I)₃Rh(μ,η⁵:η⁶-C₄H₄BPh)Rh(η⁵-C₄H₄BMe)·CH₂Cl₂ (7) with a bridging μ,η⁵:η⁶-C₄H₄BPh ligand; complex 7 was characterized by an X-ray structure determination. The resulting molecular structure was used to create a structure model for the monomeric building block of polymer 5.