Infrared Spectra and Density Functional Calculations for Three Pt−C2H2Reaction Product Isomers: PtCCH2, HPtCCH, and Pt−η2-(C2H2)

Abstract

Laser-ablated Pt atoms react with C2H2 upon co-condensation in excess argon and neon to form the vinylidene PtCCH2, the insertion product HPtCCH, and the strong complex or metallacyclopropene Pt−η2-(C2H2). These species are identified through 13C2H2, C2D2, and C2HD isotopic substitutions and density functional theory isotopic frequency calculations. The global energy minimum PtCCH2 is identified at 3022.4 cm-1 (C−H stretching), 1716.5 cm-1 (C−C stretching), and 707.9 cm-1 (CH2 deformation) in an argon matrix. The C−C stretching modes for Pt−η2-(C2H2) and HPtCCH are observed at 1653.7 and 2016.2 cm-1, respectively. In addition, the insertion product HPtCCH is identified by a Pt−H stretching mode at 2350.8 cm-1 and a C−C stretching mode at 2010.4 cm-1 in the neon matrix. The most stable PtCCH2 vinylidene isomer is the favored primary product. The strong complex Pd−η2-(C2H2) rearranges by 1,2 hydrogen atom migration to form the vinylidene PtCCH2 on 240−290 nm photolysis and on reaction during annealing solid...