Platinum Metals Rev., 1971, 15, (1), 20
Zerovalent Complexes of Platinum
The discovery some twelve years ago of complexes in which platinum exhibits zero valency—that is, in which the platinum atom is associated only with uncharged ligands—has proved of considerable importance for the synthesis of a wide range of compounds, some of which might be of use in homogeneous catalysis. A typical example of such complexes is tetrakistriphenylphosphine platinum [P(C6H5)3]4Pt. In reactions involving this compound it has been postulated that the coordinatively unsaturated species [P(C6H5)3]2Pt is a reactive intermediate. This means that there will be released in the reaction two triphenylphosphine groups which will still be available to compete for the vacant coordination sites. If the reactive intermediate could readily be prepared this situation would no longer exist, and the possibility would arise for even further advances to be made in the field of platinum organometallic chemistry.
In view of this, a paper by D. M. Blake and C. J. Nyman, of Washington State University, entitled “Photochemical Reactions of Oxalatobis(triphenyphosphine)platinum(II) and Related Complexes” (J. Am. Chem. Soc., 1970, 92, (18), 5359–5364) assumes significance. In an investigation of photochemical reactions of oxalato complexes a route to the co-ordinatively unsaturated compound has been discovered. Photolysis of an ethanol solution of [P(C6H5)3]2C2O4Pt(II) under a nitrogen atmosphere, from which oxygen had been rigorously removed, resulted in the production of this complex in the form of a dimer, [P(C6H5)3]4Pt2. Thus a relatively simple route to this reactive species has become available. Although only this one reaction has been noted here, others are described. It is apparent from this work that photolysis of oxalato complexes offers a route to reactive species for the production of catalytically active compounds in situ.