Reactions of the B ‐Phenylborole Complex [CpRh(η 5 ‐C 4 H 4 BPh)] with Metalloelectrophiles [(ring)M] 2+

Thirty‐valence‐electron dicationic triple‐decker complexes with a bridging borole ligand [CpRh(μ‐η 5 :η 5 ‐C 4 H 4 BPh)M(ring)] 2+ [M(ring) = CoCp* ( 3 ), IrCp* ( 6 ), Ru(η‐C 6 H 3 Me 3 ‐1,3,5) ( 8a ), Ru(η‐C 6 Me 6 ) ( 8b )] were obtained by stacking reactions of [CpRh(η 5 ‐C 4 H 4 BPh)] ( 2 ) with the corresponding half‐sandwich fragments [M(ring)] 2+ . Minor formation of arene‐type complexes [CpRh(μ‐η 5 :η 6 ‐C 4 H 4 BPh)M(ring)] 2+ was observed for M(ring) = IrCp* and Ru(arene). On the contrary, the arene‐type complex [CpRh(μ‐η 5 :η 6 ‐C 4 H 4 BPh)RhCp*] 2+ ( 5 ) was isolated as the sole product from the reaction of 2 with the fragment [RhCp*] 2+ ; an intermediate formation of the triple‐decker complex [CpRh(μ‐η 5 :η 5 ‐C 4 H 4 BPh)RhCp*] 2+ ( 4 ) in this reaction was detected by 1 H NMR spectroscopy. Heating 6 in nitromethane gives the symmetrical triple‐decker complex [Cp*Ir(μ‐η 5 :η 5 ‐C 4 H 4 BPh)IrCp*] 2+ ( 10 ). The cations were isolated as salts with the BF 4 – anion. The structures of 2 , 5 (BF 4 ) 2 , 6 (BF 4 ) 2 and 8a (BF 4 ) 2 were determined by X‐ray diffraction. The electrochemical properties of the complexes were also investigated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)