Complex Catalysis, XLIX 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 = Ethylene, Styrene, HNR 2 ; X = BF 4 , PF 6 , CF 3 SO 3 )

The cationic rhodium(1) complexes [Rh(PNP)(C 2 H 4 )]X; X = BF 4 ( 1a ), PF 6 ( 1b ), CF 3 SO 3 ( 1c ) were prepared by addition of the tridentate ligand 2,6‐bis(diphenylphosphanylmethyl)pyridine (PNP) to a solution of [Rh(C 2 H 4 ) 2 (solv) 2 ]X (solv = acetone or THF) under ethylene. The complexes were characterized by IR and 1 H‐, 13 C‐, and 31 P‐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)]BF 4 ( 4 ) was obtained by substitution of the ethylene from 1a with an excess of styrene. The π coordination of C 2 H 4 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)(HNR 2 )]X; HNR 2 = piperidine ( 5 ), HNMe 2 ( 6 ), HNEt 2 ( 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 .