title: Complexes of the tripodal phosphine ligands PhSi(XPPh2)3 (X = CH2, O): synthesis, structure and catalytic activity in the hydroboration of CO2.
abstract: The coordination chemistry of Fe(2+), Co(2+) and Cu(+) ions was explored with the triphosphine and triphosphinite ligands PhSi{CH2PPh2}3 (1) and PhSi{OPPh2}3 (2), so as to evaluate the impact of the electronic properties of the tripodal phosphorus ligands on the structure and reactivity of the corresponding complexes. The synthesis and characterization of the complexes [Fe(κ(3)-PhSi{CH2PPh2}3)(MeCN)3][OTf]2 (3) (OTf = O3SCF3), [Fe(κ(3)-PhSi{OPPh2}3)(MeCN)3][OTf]2 (3'), [Co(κ(2)-PhSi{CH2PPh2}3)Cl2] (4), [Co(κ(3)-PhSi{OPPh2}3)Cl2] (4'), [Cu(κ(3)-PhSi{CH2PPh2}3)Br] (5) and [Cu(κ(3)-PhSi{OPPh2}3)I] (5') were carried out. The crystal structures of 3, 3', 4, 4', and of the solvates 5·3THF and 5'·THF are reported. Complexes 3-5' were shown to promote the catalytic hydroboration of CO2 with (9-BBN)2 (9-BBN = 9-borabicyclo[3.3.1]nonane). While the iron and cobalt complexes of the triphosphine 1 are more active than the analogous complexes with 2, the opposite trend is observed with the copper catalysts. Overall, the copper catalysts 5 and 5' are both more reactive and more selective than the Fe and Co catalysts, enabling the formation of the acetal H2C(OBBN)2 with a high molar ratio of H2C(OBBN)2 : CH3OBBN up to 92 : 8.
authors.affiliation: NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette, France. jean-claude.berthet@cea.fr thibault.cantat@cea.fr.
authors.forename: Alicia
authors.initials: A
authors.lastname: Aloisi
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Berthet
authors.forename: Caroline
authors.initials: C
authors.lastname: Genre
authors.forename: Pierre
authors.initials: P
authors.lastname: Thuéry
authors.forename: Thibault
authors.initials: T
authors.lastname: Cantat