Complex catalysis .49. On the coordination of olefins and secondary amines at the cationic [2,6-bis(diphenylphosphanylmethyl)pyridine]rhodium(I) fragment [Rh(PNP)](+) - Synthesis and characterization of [Rh(PNP)(L)]X (L equals ethylene, styrene, HNR2; X=BF4, PF6, CF3SO3)

The cationic rhodium (I) complexes [Rh(PNP)(C2H4)]X; X = BF4 (1a), PF6 (1b), CF3SO3 (1c) 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 H-1-, C-13-, and P-31-NMR spectroscopy. The coordination of two ethylene molecules at the [Rh(PNP)](+) fragment could be detected by dynamic proton resonance of a solution of 1a under free ethylene. The styrene complex[Rh(PNP)(styrene)]BF4 (4) was obtained by substitution of the ethylene from 1a with an excess of styrene. The pi coordination of C2H4 and styrene in 1a 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.