Chemistry of Metal Hydrides. 27. Kinetic and ESR Studies of Acetylene Insertion Reactions with Platinum(II) Dihydrides and the Crystal Structure Determination of trans-PtH(P-t-Bu2-n-Bu)2(CH3OOCC=CHCOOCH3)

Article abstract of DOI:10.1021/ja00282a021

Platinum(II) dihydrides react with both internal and terminal activated alkynes to give alkenyl products that are trans with respect to Pt and H about the C=C bond.The stereochemistry of both the alkenyl groups and the metal center can be deduced unambiguously through analysis of 1H, 31P, and 13C NMR spectral parameters.These assignments have been confirmed by a crystallographic investigation of trans-PtH(P-t-Bu2-n-Bu)2(CH3OOCC=CHCOOCH3) which crystallizes in the monoclinic system, space group <*> with a = 9.218(2) Angstroem, b = 14.437 (2) Angstroem, c = 27.892 (3) Angstroem, β = 105.27 (1) grad.U = 3580.8 Angstroem³, and Z = 4.The structure was refined to R = 0.039 and R_w = 0.043 and is in full accord with that deduced from NMR spectral parameters.The Pt atom has distorted square planar geometry with Pt-P 2.293 (4) Angstroem, 2.311 (4) Angstroem, and Pt-C 2.086 (12) Angstroem and P-Pt-P 163.5(1) grad, C-Pt-P 95.5 (4) grad, and 100.34 (4) grad.Kinetic studies of these reactions provide evidence that formation of these monoalkenyl products occurs via an electron-transfer process.The ability of the Pt(II) dihydrides, in contrast to the monohydrides, to participate in charge-transfer mechanisms is discussed and is further illustrated by the reaction with 2,3-dichloro-5,6-dicyanoquinone.ESR studies of the reaction mixtures of Pt(II) dihydrides with acetylenes show the unexpected presence of persistent platinum-containing radicals.Evidence is presented to indicate that these are novel bis(phosphine)hydridoplatinum(II) (?-acetylene) species in which the unpaired electron is delocalized over an unsaturated three-membered metallacyclic ring.