86322-43-2Relevant articles and documents
Triphosphine-Ligated Copper Hydrides for CO2 Hydrogenation: Structure, Reactivity, and Thermodynamic Studies
Zall, Christopher M.,Linehan, John C.,Appel, Aaron M.
, p. 9968 - 9977 (2016)
The copper(I) triphosphine complex LCu(MeCN)PF6 (L = 1,1,1-tris(diphenylphosphinomethyl)ethane), which we recently demonstrated is an active catalyst precursor for hydrogenation of CO2 to formate, reacts with H2 in the presence of a base to form a cationic dicopper hydride, [(LCu)2H]PF6. [(LCu)2H]+ is also an active precursor for catalytic CO2 hydrogenation, with equivalent activity to that of LCu(MeCN)+, and therefore may be a relevant catalytic intermediate. The thermodynamic hydricity of [(LCu)2H]+ was determined to be 41.0 kcal/mol by measuring the equilibrium constant for this reaction using three different bases. [(LCu)2H]+ and the previously reported dimer (LCuH)2 can be synthesized by the reaction of LCu(MeCN)+ with 0.5 and 1 equiv of KB(OiPr)3H, respectively. The solid-state structure of [(LCu)2H]+ shows threefold symmetry about a linear Cu-H-Cu axis and significant steric strain imposed by bringing two LCu+ units together around the small hydride ligand. [(LCu)2H]+ reacts stoichiometrically with CO2 to generate the formate complex LCuO2CH and the solvento complex LCu(MeCN)+. The rate of the stoichiometric reaction between [(LCu)2H]+ and CO2 is dramatically increased in the presence of bases that coordinate strongly to the copper center, e.g. DBU and TMG. In the absence of CO2, the addition of a large excess of DBU to [(LCu)2H]+ results in an equilibrium that forms LCu(DBU)+ and also presumably the mononuclear hydride LCuH, which is not directly observed. Due to the significantly enhanced CO2 reactivity of [(LCu)2H]+ under these catalytically relevant conditions, LCuH is proposed to be the catalytically active metal hydride.
Reactivity of copper(I) tetrahydroborates toward CO2 and COS. Structure of (triphos)Cu(η1-O2CH)
Bianchini, Claudio,Ghilardi, Carlo A.,Meli, Andrea,Midollini, Stefano,Orlandini, Annabella
, p. 924 - 931 (2008/10/08)
The novel tetrahydroborate complexes (PCy3)2Cu(BH4), (np3)Cu(BH4) [np3 = tris(2-(diphenylphosphino)ethyl)amine] and (etp3)Cu(BH4) [etp3 = 1,1,1-tris((diphenylphosphino)ethyl)ethane] have been synthesized and characterized. The reactivity of these compounds and of other copper(I) tetrahydroborates, (PPh3)2Cu(BH4), (triphos)Cu(BH4) [triphos = 1,1,1-tris((diphenylphosphino)methyl)ethane], and (PMePh2)3Cu(BH4), toward CO2 and COS have been investigated. The latter triatomic molecules are reduced under very mild conditions to give metalloformate or metallothioformate derivatives. The bonding mode of the BH4- ligand, i.e. unidentate or bidentate, has been found to influence the rate of the reactions. The reactivity of the formate complex (triphos)Cu(O2CH) has been investigated in some detail. The latter compound has been studied by X-ray analysis. Crystal data: orthorhombic, space group Pn21a, a = 20.901 (8) ?, b = 17.136 (6) ?, c = 10.162 (4) ?, Z = 4, R, Rw = 0.055, 0.054 for 2267 reflections having I ≥ 3σ(I). The bonding mode of the formate group was shown to be through one oxygen atom.
