Luminescent PtII−MI (M = Cu, Ag, Au) Heteronuclear Alkynyl Complexes Prepared by Reaction of [Pt(C⋮CR)4]2- with [M2(dppm)2]2+ (dppm = Bis(diphenylphosphino)methane)

A series of PtM, PtM 2, and Pt 2 M 3 (M = Cu, Ag, Au) heteronuclear alkynyl complexes, synthesized by reaction of the tetraalkynylplatinate(II) complexes [Pt(C⋮CR) 4 ] 2 - with [M 2 ( μ -dppm) 2 ] 2+ (dppm = bis(diphenylphosphino)methane), were characterized by elemental analyses, ESI-MS, 1 H and 31 P NMR spectroscopy, and X-ray crystallography for 5 − 13 . The Pt II and M I centers are linked doubly and singly by dppm in the PtM and PtM 2 complexes, respectively. The Pt 2 Ag 3 complex 13 is composed of two PtAg units associated with another Ag center by acetylide η 2 ( π ) coordination. Strong Pt−M bonding interactions are operative, in view of their rather short distances (2.7−3.0 Å). Compounds 1 − 13 emit strongly in the solid state at 298 and 77 K with lifetimes in the microsecond range, indicating spin-forbidden triplet excited states. They also exhibit moderate photoluminescence in degassed dichloromethane at 298 K. The emission energy in the solid state decreases with an increase in the electron-donating ability of the R substituents, implying that the emissive origin is probably substantial ligand-to-cluster [RC⋮C→PtM] LMMCT transitions, in view of the Pt−M interactions.