Lanthanide and uranium complexes with an SPS-based pincer ligand

Reactions of Ln( BH4)(3)(THF) n and [Li(Et2O)][ SPSMe], the lithium salt of an anionic SPS pincer ligand composed of a central hypervalent lambda 4- phosphinine ring bearing two ortho- positioned diphenylphosphine sulfide sidearms, led to the monosubstituted compounds [Ln( BH4)(2)( SPSMe)(THF)(2)] [Ln) Ce (1), Nd ( 2)], while the homoleptic complexes [ Ln( SPSMe)(3)] [Ln) Ce (3), Nd (4)] were obtained by treatment of LnX(3) (X) I, BH4) with [K(Et2O)][ SPSMe]. The [UX2( SPSMe)(2)] complexes [X) Cl ( 5), BH4 ( 6)] were isolated from reactions of UX4 and the lithium or potassium salt of the [ SPSMe]- anion. The X- ray crystal structures of 1.1.5THF, 2.1.5THF, 3.2THF center dot 2Et(2)O, and 5, 4py reveal that the flexible tridentate [ SPSMe](-) anion is bound to the metal as a tertiary phosphine with electronic delocalization within the unsaturated parts of the ligand.