Title

The novel hydrogen dense dinuclear cobalt hydride

Document Type

Presentation

Presentation Date

Fall 9-10-2013

Conference Name

246th ACS Meeting

Conference Location

Indianapolis, IN

Abstract

We have been interested in preparing new soluble hydrogen rich complexes of the transition metals since our original synthesis of [FeH6][MgBr(THF)2]4. These compounds are sought because they are intermediates in novel routes to metallic materials and also new hydrogenation catalysts.

The search for the soluble homoleptic hydride of cobalt entailed a reaction of cobalt(II) bromide and six equivalents of phenylmagnesium bromide in THF solution under an atmosphere of hydrogen for 24 hours at temperatures between -70 and 23 °C. A striking difference in the cobalt vs. iron reaction has been the amount of biphenyl produced as a by-product (50% vs. 9% based on metal); nevertheless, an isolable yellow complex hydride precipitated. Analysis by 1H NMR and IR of this molecule and its D-labeled analogue has clearly demonstrated the presence of the Co-H bond. The solid state monomeric species Mg2CoH5 has precedence. Unexpectedly, XAFS and XANES analysis reveals a novel dinuclear cobalt hydride complex with three primary absorbers [n = 1, Co-Co, r = 2.4529(2); n = 4, Co-H, r= 1.544(7); n = 2, Co-H, r = 1.822(7)]. DFT studies combined with multiple elemental analyses have been undertaken to probe the electronic structure and to arrive at the correct formulation.

Keywords

cobalt hydride, synthesis, hydrogen, EXAFS, XANES

Disciplines

Chemistry

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