Photoreversible multiple additions of hydrogen to a highly unsaturated platinum-rhenium cluster complex

Richard D. Adams, Burjor Captain, Chad Beddie, Michael B. Hall

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

The compound Pt3Re2(CO)6(PBU t3)3, 1, was obtained from the reaction of Re2(CO)10 with Pt(PBut3)2 in octane solvent at reflux. Compound 1 consists of a trigonal bipyramidal cluster of five metal atoms with three platinum atoms in the trigonal plane and the two rhenium atoms in the apical positions. The metal cluster is formally unsaturated by 10 electrons. Compound 1 sequentially adds 3 equiv of hydrogen at room temperature/1 atm to form the series of compounds Pt3Re 2(CO)6(PBut3)3(μ-H) 2, 2, Pt3Re2(CO)6(PBu t3)3(μ-H)4, 3, and Pt 3Re2(CO)6(PBut3) 3(μ-H)6, 4. A small but significant kinetic isotope effect was observed, kH/kD = 1.3. The rate of addition of hydrogen is unaffected by the presence of a 20-fold excess of free PBu t3 in solutions of 1. Compounds 2-4 each consist of a trigonal bipyramidal cluster of three platinum and two rhenium atoms similar to that of 1. The hydrido ligands in 2-4 bridge the platinum-rhenium bonds and are arranged to give structures having overall C2v, symmetry for 2 and 3 and approximate D3h symmetry for 4. Some of the hydrido ligands were expelled from 4 in the form of hydrogen upon exposure of solutions to UV-vis irradiation to yield compound 3 and then 2 in reasonable yields, but the elimination of all hydrido ligands to yield 1 was achieved only under the most forcing UV irradiation and then only with a major loss of the complex due to decomposition. The electronic structures of 1-4 were investigated by DFT calculations. Additional DFT calculations have suggested some mechanisms for the activation of hydrogen at multicenter metal sites without ligand eliminations prior to the hydrogen additions.

Original languageEnglish (US)
Pages (from-to)986-1000
Number of pages15
JournalJournal of the American Chemical Society
Volume129
Issue number4
DOIs
StatePublished - Jan 31 2007
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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