Solid-state structure and solution behavior of eight-coordinate Sm(III) poly(pyrazolyl)-borate compounds

[Sm(Tp(Me2))(2)(kappa (2)-S2CNR2)] compounds (R = Et (1), Me (2); Tp(Me2) = HB(3,5-Me(2)pz)(3)) have been isolated from reaction of (R2NC(S)S)(2) with 2 equiv of [Sm(Tp(Me2))(2)]. Reductive cleavage of 2,2'-dipyridyl disulfid e or 2,2'-dipyridyl diselenide by [Sm(Tp(Me2))(2)] afforded good yields of [Sm(Tp(Me2))(2)(kappa (2)-Y)] compounds (Y = 2-SC5H4N (3), 2-SeC5H4N (4)). 4 is the first selenopyridine complex of an f-block element. Sm(Tp(Me2))(2) (2-OC5H4N) (5) has been synthesized by salt metathesis of [Sm(Tp(Me2))(2)Cl ] with the sodium salt of the 2-hydroxypyridine. The solid-state structures of 1, 3, 4, and 5 were determined by single-crystal X-ray diffraction anal ysis and revealed that the compounds are all eight-coordinate with dodecahe dral geometry. The samarium atoms are bound in tridentate fashion to two py razolylborate ligands and in bidentate fashion by the third ligand. The sol ution behavior of the compounds was studied by H-1 NMR techniques. H-1-H-1 exchange spectroscopy experiments give evidence for two distinct dynamic re gimes occurring in solution.