SUBSTRATE ACTIVATION BY THE WILKINSON ANALOGOUS COMPLEX CLRH(P-SIMILAR-TO-O) (P-O)-CONTAINING ETA(2)-P-O-CHELATED AND ETA(1) P-BONDED (METHOXYETHYL)DICYCLOHEXYLPHOSPHINE AS A HEMILABILE LIGAND

In the presence of a variety of small molecules the pseudo 14-electron rhodium complex ClRh(P similar to O)(arc P O) (1, arc P O = eta(2)(O, P)-chelated Cy(2)PCH(2)CH(2)OCH(3) ligand; P similar to O = eta(1)(P)- coordinated) is shown to undergo a facile cleavage of its intramolecul ar ether moiety. The reaction of 1 with ethene, diphenylacetylene and carbon disulfide results in the irreversible coordination of the corre sponding molecule to the metal yielding the complexes ClRh(C2H4)(P sim ilar to O), (2), ClRh(PhC=CPh)(P similar to O)(2) (3), ClRhCS2(P simil ar to O)(2) (4), and ClRhCS(P similar to O)(2) (5). All compounds are obtained in excellent yields under very mild conditions, The structure s of 4 and 5 were determined by single-crystal X-ray diffraction. The oxidative addition of HCL to the starting material 1 leads to the mono chelated octahedrally coordinated complex Cl2Rh(H)(P similar to O)(arc P O) (6). Complex 6 exhibits fluxional behavior on the P-31 NMR time scale. Line-shape analysis of variable temperature P-31{H-1} NMR spect ra of 6 affords the Eyring parameters Delta H double dagger = 42.3 kJ mol(-1) and Delta S double dagger = -63.7 J mol(-1) K-1, indicating an intramolecular exchange mechanism. The Rh-H bond in 6 is able to inse rt ethene to give the ethylrhodium(III) complex Cl2RhC2H5(P similar to O), (7). Subsequently, there follows a fast sigma/pi rearrangement to the complex Cl2Rh(eta(2)-C2H4)(H)P similar to O), (8) which undergoes a slow pi/sigma transformation to the monochelated product Cl2Rh(C2H5 )(P similar to O)(arc P O) (9).