Tridentate to Bidentate in a Platinum(II) Chelate: A 90° Anthranilaldehyde Rotation

The labilization of a coordinated formyl group in a platinum(II) chelate by nucleophilic ligands has been examined structurally. The chelating ligand is the deprotonated dimeric Schiff base condensate of o-aminobenzaldehyde. The aldehyde was trapped in its uncoordinated form by adding a 1:1 molar ratio of triphenylphosphine to the complex in acetonitrile. The resulting adduct crystallizes in the space group C2/c with unit cell dimensions a = 32.75 (6) Å,b= 10.04 (2) Å, c = 19.71 (7) Å, and β = 118.5 (2)°. The immediate coordination sphere of the platinum consists of two nitrogens from the chelate, the phosphorus of the triphenylphosphine, and a chloride. The benzaldehyde ring, upon dissociation of the aldehyde oxygen from the platinum, has rotated 90° to a position perpendicular to the deprotonated o-aminobenzylidene group. The aldehyde oxygen is poised almost directly above the imine nitrogen at a distance of 2.87 (1) Å.