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Photochemical Generation of Dihydrogen Complexes of Chromium and Tungsten

Steven L. Matthews and D. Michael Heinekey*

Contribution from the Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700

J. Am. Chem. Soc., 2006, 128 (8), pp 2615–2620

DOI: 10.1021/ja057912r

Publication Date (Web): January 26, 2006

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, heinekey@chem.washington.edu

Abstract

Photolysis of solutions of M(CO)₆ (M = Cr, W) at low temperature in the presence of hydrogen gas affords Cr(CO)₅(H₂) (1) and W(CO)₅(H₂) (2). Complexes 1 and 2 are characterized as dihydrogen complexes based on short T₁ values for the hydride resonances and the observation of a large HD coupling in the HD derivatives. Irradiation of a phosphine-substituted derivative (PMe₃)Cr(CO)₅ in the presence of hydrogen gas gave similar results. Thus cis-(PMe₃)Cr(CO)₄(H₂) (3) and trans-(PMe₃)Cr(CO)₄(H₂) (4) were prepared and characterized by ¹H and ³¹P 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 H₂ leads to the dihydrogen complexes. Complexes 1 and 2 are moderately acidic, with deprotonation effected by mild bases.

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Published In Issue March 01, 2006
Received November 22, 2005

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Article

Photochemical Generation of Dihydrogen Complexes of Chromium and Tungsten