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Published August 29, 2012 | Published + Supplemental Material
Journal Article Open

Dihydrogen Binding to Isostructural S = 1/2 and S = 0 Cobalt Complexes

Abstract

Two isostructural, nonclassical Co(H_2) complexes are prepared from their Co(N_2) precursors using tris(phosphino)silyl and tris(phosphino)borane ancillary ligands. Comproportionation of CoBr_2 and Co metal in the presence of TPB (tris-(o-diisopropylphophinophenyl)borane) gives (TPB)CoBr (4). One-electron reduction of 4 triggers N_2 binding to give (TPB)Co(N_2) (2-N_2) which is isostructural to previously reported [SiP_3]Co(N_2) (1-N_2) ([SiP_3] = tris-(o-diisopropylphosphinophenyl)silyl). Both 1-N_2 and 2-N_2 react with 1 atm H_2 to generate thermally stable H_2 complexes 1-H_2 and 2-H_2, respectively. Both complexes are characterized by a suite of spectroscopic techniques in solution and by X-ray crystallography. The H_2 and N_2 ligands in 2-H_2 and 2-N_2 are labile under ambient conditions and the binding equilibria are observable by temperature-dependent UV/vis. A van't Hoff analysis allows for the ligand binding energetics to be determined (H_2: ΔHº = −12.5(3) kcal mol^(–1) and ΔSº = −26(3) cal K^(–1) mol^(–1); N_2: ΔHº = −13.9(7) kcal mol^(–1) and ΔSº = −32(5) cal K^(–1) mol^(–1)).

Additional Information

© 2012 American Chemical Society. Received: May 30, 2012. Publication Date (Web): August 14, 2012. We thank the Gordon and Betty Moore Foundation and the NSF Center for Chemical Innovation on Solar Fuels (CCI Solar, CHE-0802907 and CHE-0947829) for funding. We thank Prof. George Rossman (solid-state Raman studies), Maraia Ener (solution-state Raman studies), and Lawrence Henling (X-ray crystallography) for experimental assistance.

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Published - ja305248f.pdf

Supplemental Material - ja305248f_si_001.pdf

Supplemental Material - ja305248f_si_002.cif

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Created:
August 19, 2023
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