The structures of [Ru(bpy),] (PF6)2 (bpy = 2,2'-bipyridine) and [ R~( b p m )~] (PF6)2.CH3CN (bpm = 2,2'-bipyrimidine) have been determined by single-crystal X-ray diffraction. [R~(bpy)~l(PF,), crystallized in the hexagonal space group P3cl with cell dimensions a = 10.760 (1) A, b = 10.760 (1) A, c = 16.391 (3) A, u = B = 90°, y = 120°, Z = 2, and dal4 = 1.74 g ~m -~, Of the 1411 unique reflections (Mo Ka, l o I 26' I 57O), 1081 reflections with I > a(l) were used in full-matrix least-squares refinement. Final residuals were RF = 0.044. [ R U (~~~)~] ( P F~)~-C H~C N crystallized in the triclinic space group Pi with cell dimensions a = 10.552 (2) A, b = 11.635 (1) A, c = 14.231 (2) A, a = 74.47 (1)O, fl = 81.41 (1)O, y = 75.08 (1)O, 2 = 2, and d,,, = 1.852 g ~m -~. Of the 4269 unique reflections (Mo Ka, 3.Y I 20 I 45O), 3941 reflections with 1 4 > 4.0u(F) were used in full-matrix least-squares refinement. Final residuals were RF = 0.028, Ru-N bond distances in [ R~( b p y )~]~+ were 2.056 (2) 8, and average 2.067 (4) A in [ R~( b p r n )~]~+ . Other bond distances and angles lead to the conclusion that the structures of the [ R~( b p y )~]~+ and [ R~( b p m )~]~+ cations are basically the same.

This study focuses on a series of PtII(L-L')(dppm)n+ complexes, where dppm is bis(diphenylphosphino)methane and L-L' are C-C' (n = 0), C-N (n = 1), and N-N' (n = 2) aromatic ligands. Structural characteristics are as follows: for [Pt(phen)(dppm)](PF6)2, a N-N' derivative, monoclinic, C2/c, a = 33.583(6) A, b = 11.399(2) A, c = 22.158(4) A, Z = 8; for [Pt(phq)(dppm)](PF6), a C-N derivative, triclinic, P1, a = 11.415(3) A, b = 13.450(3) A, c = 14.210(4) A, Z = 2; for [Pt(phpy)(dppm)](PF6), a C-N derivative, triclinic, P1, a = 10.030(3) A, b = 13.010(2) A, c = 15.066(4) A, Z = 2; and for [Pt(bph)(dppm)], a C-C' derivative, P2(1)/c, a = 17.116(7) A, b = 21.422(6) A, c = 26.528(6) A, Z = 12, where phen is 1,10-phenanthroline, phq is 2-phenylquinoline, phpy is 2-phenylpyridine, and bph is 2,2'-biphenyl. Structural features indicate that the Pt-C bond distance is shorter than the Pt-N bond distance in symmetrical complexes and that the Pt-P bond distance trans to N is shorter than the Pt-P bond trans to C. This is consistent with the 31P NMR spectra where the chemical shift of the P trans to C is approximately 10 ppm less than found for P trans to N. The energy maxima of the metal-to-ligand charge-transfer band for the complexes containing various L-L' ligands occur in the near-UV region of the spectrum and fall into the energy series bpy > bph > phen > 2-phpy > 2-ptpy > 2-phq > 7,8-bzq, where bpy is 2,2'-bipyridine, 2-phpy is 2-phenylpyridine, 2-ptpy is 2-p-tolylpyridine, and 7,8-bzq is 7,8-benzoquinoline. The emission energy maxima, ascribed to variance in metal-perturbed triplet ligand centered emission, commence near 500 nm and follow the series phen > bpy > 7,8-bzq > 2-phpy > 2-ptpy > bph > 2-phq. In general, emission is observed at 77 K and in solution at low temperatures, but the temperature dependence of the emission lifetimes indicates thermal activation to another state occurs with an energy of approximately 1800 cm-1 for the complexes, with the exception of [Pt(bph)(dppm)], which has an activation energy of approximately 2300 cm-1.

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