Heterobimetallic dioxygen activation:: Synthesis and reactivity of mixed Cu-Pd and Cu-Pt bis(μ-oxo) complexes

Heterobimetallic CuPd and CuPt bis(mu-oxo) complexes have been prepared by the reaction of (PPh3)(2)MO2 (M = Pd, Pt) with LCu(I) precursors (L = beta-diketiminate and di- and triamine ligands) and characterized by low-temperature UV-vis, resonance Raman, and H-1 and P-31{H-1} NMR spectroscopy in conjunction with DFT calculations. The complexes decompose upon warming to yield OPPh3, and in one case this was shown to occur by an intramolecular process through crossover experiments using double-labeling (oxo and phosphine). The reactivity of one of the complexes, (LCu)-Cu-Me2(mu-O)(2)Pt(PPh3)(2) (L-Me2 = beta-diketiminate), with a variety of reagents including CO2, 2,4-di-tert-butylphenol, 2,4-di-tert-butylphenolate, [NH4][PF6], and dihydroanthracene, was compared to that of homometallic Pt-2 and Cu-2 counterparts. Unlike typical [Cu-2(mu-O)(2)](2+) cores which have electrophilic oxo groups, the oxo groups in the [Cu(mu-O)(2)Pt](+) core behave as bases and nucleophiles, similar to previously described Pt-2 compounds. In addition, however, the [Cu(mu-O)(2)Pt](+) core is capable of oxidatively coupling 2,4-di-tert-butylphenol and 2,4-di-tert-butylphenolate. Theoretical evaluation of the electron affinities, basicities, and H-atom transfer kinetics and thermodynamics of the Cu-2 and CuM (M = Pd, Pt) cores showed that the latter are more basic and form stronger O-H bonds.