Isolation of a Low-Coordinate Rhodium Phosphine Complex Formed by C−C Bond Activation of Biphenylene

The isolation of a low-coordinate rhodium complex containing the 2,2′-biphenyl ligand, trans-[Rh(2,2′-biphenyl)(PiPr3)2][BArF4], is described. This complex is prepared by C−C bond activation of biphenylene by the [Rh(PiPr3)2]+ fragment and proceeds via the (isolated) intermediate π complex [Rh(η6-biphenylene)(PiPr3)2][BArF4]. An intramolecular ring slippage mechanism is suggested for this process, and this is supported by DFT calculations.