Preparation and Characterization of Simple Dihalomethylidene Platinum Dihalide Complexes in Reactions of Laser-Ablated Pt Atoms with Tetrahalomethanes

Platinum atoms react with tetrachlorofluoromethanes upon laser-ablation and with ultraviolet irradiation to form dihalomethylidene platinum dihalide complexes, CX2=PtX2. These new molecules are identified from carbon-13 and chlorine isotopic shifts, displacements in functional group frequencies as chlorine is replaced with fluorine, and comparison to frequencies calculated by density functional theory. The Pt-C bond lengths calculated here, 1.810 to 1.816 angstrom, are shorter than analogous bond lengths measured earlier for Pt(II) carbene complexes (1.943-1.950 angstrom). The computed effective Pt-C bond orders range from 1.41 to 1.70 as chlorine is replaced by fluorine since the more electronegative halogen appears to concentrate the Pt 5d orbitals and make them bond better with carbon. These platinum methylidene complexes thus have a substantial amount of double bond character from d(pi)-p(pi) bonding.