NOVEL HEMILABILE (PHOSPHINOALKYL)ARENE LIGANDS - MECHANISTIC INVESTIGATION OF ALL UNUSUAL INTRAMOLECULAR, ARENE-ARENE EXCHANGE-REACTION

The novel, hemilabile (phosphinoalkyl)arene ligands ArX(CH2)(2)PPh(2) (1a, Ar = C6H5, X = O; 1b, Ar = C6H5, X = CH2; 1c, Ar = FC6H4, X = CH2 ) were synthesized and complexed to Rh(I) to form the bis(phosphine), eta(6)-arene piano stool complexes ArX(CH2)(2)PPh(2))Rh(eta(1)-ArX(CH2 )(2)PPh(2))]BF4 (2a-c). Complexes 2a-c were fully characterized in sol ution, and complex 2a was characterized by single-crystal X-ray diffra ction methods. Two of these complexes, 2a,c, undergo an unusual, degen erate eta(6)-arene, free arene exchange reaction which was studied by 2-D NMR EXSY experiments. A mechanism for the exchange reaction of 2a which involves the formation of a square planar, cis-phosphine, cis-et her Rh(I) complex, [Rh(eta(2)-PhO(CH2)(2)PPh(2))(2)]BF4 (13), is propo sed.