On the Coordination of Olefins and Secondary Amines at the Cationic [2,6-Bis(diphenyIphosphanylmethyl)pyridine]rhodium(I) Fragment [Rh(PNP)]+ - Synthesis and Characterization of [Rh(PNP)(L)]X (L = Ethylene, Styrene, HNR2; X = BF4, PF6, CF3so3)

Article abstract of DOI:10.1002/cber.19971300720

The cationic rhodium(I) complexes [Rh(PNP)(C₂H₄)]X; X = BF₄ (1a), PF₆ (1b), CF₃SO₃ (1e) were prepared by addition of the tridentate ligand 2,6-bis(diphenylphosphanylmethyl)pyridine (PNP) to a solution of [Rh(C₂H₄)₂(solv)₂]X (solv = acetone or THF) under ethylene. The complexes were characterized by IR and ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The coordination of two ethylene molecules at the [Rh(PNP)]⁺ fragment could be detected by dynamic proton resonance of a solution of la under free ethylene. The styrene complex [Rh(PNP)(styrene)]BF₄ (4) was obtained by substitution of the ethylene from la with an excess of styrene. The π coordination of C₂H₄ and styrene in la and 4 respectively was confirmed by X-ray crystal structure analysis. The olefin complexes react with an excess of the secondary amine to give the corresponding amine complexes [Rh(PNP)(HNR₂)]X; HNR₂ = piperidine (5), HNMe₂ (6), HNEt₂ (7). Conversly, the amine could be released from the amine complexes with an excess of ethylene at low temperature by the formation of the ethylene complex 1. VCH Verlagsgesellschaft mbH,.