Reactions of Ln(BH
4)
3(THF)
n and [Li(Et
2O)][SPS
Me], the lithium salt of an anionic SPS pincer ligand composed ofa central hypervalent
4-phosphinine ring bearing two
ortho-positioned diphenylphosphine sulfide sidearms, led tothe monosubstituted compounds [Ln(BH
4)
2(SPS
Me)(THF)
2] [Ln = Ce (
1), Nd (
2)], while the homoleptic complexes[Ln(SPS
Me)
3] [Ln = Ce (
3), Nd (
4)] were obtained by treatment of LnX
3 (X = I, BH
4) with [K(Et
2O)][SPS
Me]. The[UX
2(SPS
Me)
2] complexes [X = Cl (
5), BH
4 (
6)] were isolated from reactions of UX
4 and the lithium or potassiumsalt of the [SPS
Me]
- anion. The X-ray crystal structures of
1·1.5THF,
2·1.5THF,
3·2THF·2Et
2O, and
5·4py revealthat the flexible tridentate [SPS
Me]
- anion is bound to the metal as a tertiary phosphine with electronic delocalizationwithin the unsaturated parts of the ligand.