Bulky pyrazole as ligands in rhodium(I) complexes. Crystal structure of chlorodicarbonyl (3-p-methoxyphenylpyrazole)rhodium(I)

Abstract A new family of complexes containing bulky pyrazoles substituted in the 3 or the 3 and 5 positions, [RhCl(L 2 )(Hpz R′,R″ )] (L 2  NBD, 2CO; R′  Bu t , Ph, p -CH 3 OC 6 H 4 (An), R″  H; R′  Bu t , Ph, R″  CH 3 ; R′  R″  H, CH 3 ), has been obtained. A dynamic behaviour has been observed only in complexes with the less demanding pyrazole ligands, relating with a metallotropic equilibrium when R′  R″  H, Me, or a diolefin reorientation when R′  Bu t , Ph, An, R″  H. The X-ray crystal structure of [RhCl(CO) 2 (Hpz An )] has been solved, showing a molecular stacking with a RhRh separation of 3.398(3) A along the one-dimensional chain.