TRIVALENT LANTHANIDE CHALCOGENOLATES - LN(SEPH)(3), LN(2)(EPH)(6), LN(4)(SPH)(12), AND [LN(EPH)3](N), (E=S, SE) - HOW METAL, CHALCOGEN, ANDSOLVENT INFLUENCE STRUCTURE

A series of trivalent lanthanide (Ln) benzenechalcogenolate (EPh, E = S,Se) complexes have been prepared and structurally characterized in a n attempt to evaluate how metal size: chalcogen, and solvent influence structure and physical properties. The compounds [(py)(3)Ln(SPh)(3)]( 2) (Ln=Ho (1) and Tm (2)), [(py)(2)Sm(SPh)(3)](4) (3), [(THF)Sm(SPh)(3 )](4n) (4), (THF)(3)Ln(SePh)(3)(Ln=Tm (5), Ho (6): Er (7)), [(py)(3)Sm (SePh)(3)](2) (8), and [(THF)(4)Ln(3)-(SePh)(9)](n) (Ln=Pr (9), Nd (10 ), and Sm (11)) were isolated and characterized by IR, NMR, and UV-vis ible spectroscopy. Compounds 2-4, 7, S, and 10 have also been characte rized by low-temperature single-crystal X-ray diffraction. Three trend s in structure are clear. First, the tendency to form oligomeric struc tures is found to increase with the size of the lanthanide ion. Second , thiolates bridge metal ions to form polynuclear structures more effe ctively than selenolates. Finally, pyridine displaces bridging chalcog enolates to form less extended structures more effectively than THF. C ompounds 5-7 are molecular fac-octahedral complexes, compounds 1, 2, a nd 8 are bimetallic molecules with a pair of chalcogen atoms spanning the pentagonal bipyramidal metal centers, compound 3 is a tetrametalli c structure with an alternating (3-2-3) number of mu(2)-thiolates span ning the linear assembly of four seven-coordinate Sm(III) ions, and co mpounds 4, 9, 10, and 11 are polymers with sets of three doubly bridgi ng benzenechalcogenolates connecting adjacent metal-ions, Resonance:Ra man spectroscopy indicates that the intense electronic absorption asso ciated with Sm(III) chalcogenolate is a chalcogen-to-metal charge-tran sfer excitation. Compounds 1 and 2 decompose thermally to give Ln(2)S( 3).