Photochemical generation of dihydrogen complexes of chromium and tungsten

Steven L Matthews; D Michael Heinekey

doi:10.1021/ja057912r

Photochemical generation of dihydrogen complexes of chromium and tungsten

J Am Chem Soc. 2006 Mar 1;128(8):2615-20. doi: 10.1021/ja057912r.

Authors

Steven L Matthews¹, D Michael Heinekey

Affiliation

¹ Department of Chemistry, University of Washington, 98195-1700, USA.

PMID: 16492046
DOI: 10.1021/ja057912r

Abstract

Photolysis of solutions of M(CO)(6) (M = Cr, W) at low temperature in the presence of hydrogen gas affords Cr(CO)(5)(H(2)) (1) and W(CO)(5)(H(2)) (2). Complexes 1 and 2 are characterized as dihydrogen complexes based on short T(1) values for the hydride resonances and the observation of a large HD coupling in the HD derivatives. Irradiation of a phosphine-substituted derivative (PMe(3))Cr(CO)(5) in the presence of hydrogen gas gave similar results. Thus cis-(PMe(3))Cr(CO)(4)(H(2)) (3) and trans-(PMe(3))Cr(CO)(4)(H(2)) (4) were prepared and characterized by (1)H and (31)P NMR spectroscopy. When the photolysis reactions were carried out in methylene chloride, solvent binding competitive with hydrogen binding was observed. This was not observed in less coordinating solvents such as alkanes. Subsequent displacement of solvent by H(2) leads to the dihydrogen complexes. Complexes 1 and 2 are moderately acidic, with deprotonation effected by mild bases.