Spectroscopy and X-ray crystal structure of luminescent Pt2(dppm)2(CN)4 [dppm = bis(diphenylphosphino)methane]

Abstract

The reaction of Pt(CN)2·xH2O with dppm [bis(diphenylphosphino)methane] in refluxing dimethylformamide (DMF) yielded Pt2(dppm)2(CN)4. The X-ray structure of this binuclear platinum(II) complex has been determined: Pt2(dppm)2(CN)4·2DMF, space group P21/n, Z = 2, a = 11.561 (1) Å, b = 17.475 (1) Å, c = 13.981 (5) Å, β = 95.34 (2)°. The Pt2(dppm)2(CN)4 molecule adopts the trans,trans geometry and consists of two platinum atoms bridged by two dppm groups, with two trans cyanide ions bonded to each platinum atom. The measured Pt⋯Pt distance is 3.301 (1) Å, indicative of a weak Pt⋯Pt bonding interaction. The UV-vis absorption spectrum of methanolic solutions of Pt2(dppm)2(CN)4 exhibits an intense band at 324 nm (εmax 10 500) and a weak band at ca. 390 nm, assigned to the 1A1g → 1B1u and 1A1g → 3B1u transitions, respectively. Excitation of Pt2-(dppm)2(CN)4 at 324 nm in degassed methanol leads to an intense emission at 425 nm with a shoulder at ca. 530 nm. The room-temperature triplet lifetime has been found to be 0.23 μs in degassed methanol. © 1989 American Chemical Society.