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Title: Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds

Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H{sub 2} gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe){sub 2}, dmpe = 1,2-bis(dimethylphosphinoethane) was capable of reducing a variety of BX{sub 3} compounds having hydride affinity (HA) greater than or equal to HA of BEt{sub 3}. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, (HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +}), to form B-H bonds. The hydride donor abilities ({Delta}G{sub H{sup -}}{sup o}) of HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +} were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX{sub 3} compounds. The collective data guided our selection of BX{sub 3} compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe){sub 2} was observed to transfer H{sup -} to BX{sub 3} compounds with X = H, OC{sub 6}F{sub 5} and SPh. The reaction with B(SPh){sub 3} is accompanied by formation of (BH{sub 3}){sub 2}-dmpe and (BH{sub 2}SPh){sub 2}-dmpe products that follow from reductionmore » of multiple BSPh bonds and loss of a dmpe ligand from Co. Reactions between HCo(dmpe){sub 2} and B(SPh){sub 3} in the presence of triethylamine result in formation of Et{sub 3}N-BH{sub 2}SPh and Et{sub 3}N-BH{sub 3} with no loss of dmpe ligand. Reactions of the cationic complex [HNi(dmpe){sub 2}]{sup +} with B(SPh){sub 3} under analogous conditions give Et{sub 3}N-BH{sub 2}SPh as the final product along with the nickel-thiolate complex [Ni(dmpe){sub 2}(SPh)]{sup +}. The synthesis and characterization of HCo(dedpe){sub 2} (dedpe = diethyldiphenyl(phosphino)ethane) from H{sub 2} and a base is also discussed; including the formation of an uncommon trans dihydride species, trans-[(H{sub 2})Co(dedpe){sub 2}][BF{sub 4}].« less
Authors:
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Publication Date:
OSTI Identifier:
1033061
Report Number(s):
PNNL-SA-79240
Journal ID: ISSN 0020-1669; INOCAJ; EB4202000; TRN: US201202%%563
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 50; Journal Issue: 23
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ACETONITRILE; AFFINITY; AMMONIA; CLEAVAGE; COBALT; HYDRIDES; HYDROGEN STORAGE; NICKEL HYDRIDES; REGENERATION; SYNTHESIS; TRANSFER REACTIONS; TRANSITION ELEMENTS hydride transfer; transition metal; cobalt; nickel; GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; AMMONIA-BORANE; DONOR ABILITIES; HYDROGEN; REGENERATION; PROTON; NI; FEH(DMPE)2(BH4); ACETONITRILE