Sammendrag
Design of a selective homogeneous methane functionalizing catalyst based on [(ArN=CRCR=NAr)Pt(Me)(L)]+ requires knowledge of its stability in various reaction media, particularly water. Reaction of (diimine)PtMe2 1 (diimine = ArN=CRCR=NAr, Ar = 2,6-Me2C6H3, R = Me) with HOTf (OTf = OSO2CF3) gives the methane activating compound (diimine)Pt(Me)OTf 3. When varying amounts of H2O are added during the synthesis of 3, competing degradation pathways lead to two different characterizable products. With only trace amounts of water, two dimeric species, [(diimine)Pt(µ-Cl)(µ-OH)Pt(diimine)](OTf)2 6 and [(diimine)Pt(µ-OH)2Pt(diimine)](OTf)2 7, are isolated, in addition to an uncharacterized dark brown precipitate. When an excess of H2O is added, the aquo species [(diimine)Pt(Me)(H2O)][OTf] 5 is first observed, which then reacts further to give a dark brown precipitate and 7. The structures of 1, 6, and 7 are presented. Both 6 and 7 exhibit unusual conformations for their respective classes. Compound 6 has a rarely observed planar conformation, while 7 has an unusual bifurcated H-bonding motif between the bridging OH-groups and a triflate anion and a highly bent conformation.