1ST PROTOTYPE OF NEUTRAL DIACYL COMPLEXES OF PLATINUM(II) AND RELATED ACYL(ALKYL) COMPLEXES OF PLATINUM(II)

The acyl(carbonyl) complex cis-[Pt(COPh)- (COXPPh3)2]+ (2a) reacts with PhLi to yield the neutral dlbenzoyl complex cis-Pt(COPh)2(PPh3)2 (3a) in 34% Isolated yield. The crystallographic data of 3a indicate that it is disposed In a distorted square-planar geometry with two benzoyl carbonyls in the s-trans configuration. The analogous reaction of the cationic 2a with MeLI, however, gives three products: cis -Pt(COPh)(COMeXPPh3)2 (3b), cis-Pt(COPhXMeXPPh3)2 (4), and Pt(COPhXMeXCOXPPh3) (5a) in a relative ratio of 1:2.5:3 in 55% total yield. In a similar reaction carried out in the presence of extra PPh3, only 3b and 4 were obtained, in a 1:3.5 ratio In 90% total yield. The structures of the complexes 4 and 5a were determined by X-ray crystallography, and both are square planar. In 5a, the PPh3 was found trans to the benzoyl ligand. The replacement of a PPh3 in 4 by CO gives 5a and its reglo isomer 5b, whose PPh3 is instead trans to the methyl group. The complex 5b is kinetically favored but thermodynamically unstable. These substitution reactions are reversible with the equilibria in favor of 4. © 1990, American Chemical Society. All rights reserved.