The UV-visible absorption, emission, and excitation spectra and the emission lifetimes of M(PPh3)3 and M2(dppm)3 (M = Pd, Pt; dppm = bis(diphenylphosphino)methane) in 2-methyltetrahydrofuran solution at room temperature and 77 K have been investigated.Electronic absorption and emission bands attributable to -*-d transitions are observed in the 400-900-nm region in the d10-d10 binuclear complexes; the M2 emissive state is 123A2"(da*)(pa).Resonance Raman spectra associated with excitation in the M2(dppm)3•*-d * singlet absorption band have been measured: peaks attributable to M-M stretching vibrations are at 120.0 (k = 0.45; M = Pd) and 102.5 cm-1 (k = 0.60 mdyn A-1; = Pt), thereby confirming the presence of weak M-M bonding interactions.When an empirical distance/force constant equation is used, the Pd-Pd distance in Pd2(dppm)3 is estimated to be 3.043 A.The spectroscopic properties and photochemical reactivities of d8-d8 complexes have been extensively investigated.1'3Related d10-d10 species4 have not attracted as much attention, but the luminescence behavior of Pd2(dppm)3 (dppm bis(diphenyl- phosphino)methane) and Pd2(dpam)3 (dpam = bis(diphenylarsino)methane) has been reported.5The d,0-d10 systems exhibit long-lived luminescences and are very reactive in solution with small molecules.46,5The aim of this work is to elucidate the electronic structures of the lowest singlet and triplet excited states of d10-d10 Pd2 and Pt2 species. Experimental SectionMaterials.K2PtCl4, K2PdCl4 (Aldrich), PPh3, and dppm (Strem) were used without further purification.M(PPh3)3 and M2(dppm)3 complexes were synthesized according to standard procedures46,6,7 and were purified by triple recrystallization in benzene/ethanol or benzene/pro- panol.Purity was checked by elemental analysis and 31P and NMR spectroscopy (500 MHz; 1000 scans).All complexes are air-sensitive; they were stored in an oxygen-free dry box when not in use.The M-(PPh3)3 complexes also are light-sensitive in the solid state; they were (1) (a) Marshall,
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Harvey et al. (1988) studied this question.