title: Original palladium pincer complexes deriving from 1,3-bis(thiophosphinoyl)indene proligands: C(sp3)-H versus C(sp2)-H bond activation.
abstract: A series of original 2-indenylidene palladium pincer complexes {PdL[Ind(Ph(2)P==S)(2)]} (L = HNCy(2), PPh(3), Cl(-)) have been prepared by double C-H activation of a 1,3-bis(thiophosphinoyl)indene proligand. Crystallographic analyses and DFT calculations indicate that the bonding situation of the {Pd[Ind(Ph(2)P==S)(2)]} fragment is essentially governed by the conjugated and rigid nature of the dianionic pincer ligand, the nature of the coligand having little influence. The formation of the 2-indenylidene complexes involves either a 2-indenyl pincer or a four-membered cyclometalated complex as an intermediate, suggesting that C(sp(2))-H or C(sp(3))-H bond activation takes place. However, deuterium labelling experiences show that in all cases, C(sp(3))-H bond activation occurs followed eventually by a Pd/H exchange. Nevertheless, evidence for direct C(sp(2))-H bond activation under mild conditions is obtained when a methyl group is introduced at the indene proligand to prevent C(sp(3))-H bond activation. The ensuing dissymmetrical 2-indenyl palladium pincer complex has been fully characterized.
authors.affiliation: University of Toulouse, UPS, LHFA, 118 route de Narbonne, F-31062 Toulouse, France.
authors.forename: Noel
authors.initials: N
authors.lastname: Nebra
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lisena
authors.forename: Nathalie
authors.initials: N
authors.lastname: Saffon
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron
authors.forename: Blanca
authors.initials: B
authors.lastname: Martin-Vaca
authors.forename: Didier
authors.initials: D
authors.lastname: Bourissou