Structure and reactivity of palladium and platinum arylazooximates.

The structure and selected reactions of the title compounds are reviewed. Some highlights are as follows (L = conjugate base of phenylazoacetaldoxime). While PtL exist in cis and trans forms, PdL occurs only in the trans form. In the crystalline state cis-PtL consists of weakly held dimers (Pt. Pt 3.151 A) but trans-PtL consists of stacks of discrete molecules in the solid state. Trans- PdL displays a surprisingly large tetrahedral distorsion. The different metal-ligand bonds undergo selective cleavage by different reagents. Thus HCl and tertiary phosphines respectively cleave the M-N (oxime) and M-N (azo) bonds. Phosphine cleavage leads to interesting situations such as cone angle-dependent equilibria and fluxional behaviour. A rich redox chemistry consisting of successive reductions of the azo groups and of the metal are revealed electrochemically. Cis-PtL unlike trans- PtL undergoes a facile one-electron oxidation at low potentials. Another very curious reaction of cis-PtL is the process in which an aromatic ring is thermally hydroxylated at the expense of an oximato oxygen atom. The meaning and significance of the observations are discussed. [ABSTRACT FROM AUTHOR]