DOUBLE OXIDATIVE CARBON CARBON COUPLING OF A DIMERIC ORTHOPALLADATED AMIDO COMPLEX LEADING TO REDOX-ACTIVE TETRAPALLADIA UNITS [PD4](N+) (N = 0-4)

Chemical or electrochemical oxidation of the chiral orthometalated amido dimeric complex [Pd-o-C6H4-C(Me)=N-NPh)L]2 (L = P(OMe)3) leads to double carbon-carbon coupling on the para carbons of the phenyl groups, giving pure diastereomeric tetrapalladia units [Pd4]n+ (n = 0-4) related by fully reversible monoelectronic electron transfers. The species [Pd4]4+ undergoes splitting with Cl-, giving dimeric units [Pd2] where a 4,4'-biphenylene quinone diimine is trapped and stabilized between two palladia atoms; reduction with CoCp2 affords a mixture of both possible diastereomers of [Pd4]0. Near-infrared absorptions have been observed for paramagnetic [Pd4]3+, which can be regarded as a "mixed oxidation state' compound. The structure of [Pd-o-C6H4-C(Me)=N-NPb-p-NO2)L]2 (L]2 (L = P(OMe)3), where coupling is precluded by NO2 groups, was determined crystallographycally [space group P1BAR (triclinic), a = 10.901 (16) angstrom, b = 13.744 (9) angstrom, c = 14.242 (5) angstrom, alpha = 73.41 (4)-degrees, beta = 87.61 (6)-degrees, gamma = 81.00 (8)-degrees, V = 2020 (5) angstrom3, Z = 21.