Synthesis, X-ray Crystal Structure Determination, and NMR Spectroscopic Investigation of Two Homoleptic Four-Coordinate Lanthanide Complexes: Trivalent ((t)Bu(2)P)(2)La[(&mgr;-P(t)Bu(2))(2)Li(thf)] and Divalent Yb[(&mgr;-P(t)Bu(2))(2)Li(thf)](2)(,)(1)

La(OSO(2)CF(3))(3) reacts with 4 equiv of LiP(t)Bu(2) in tetrahydrofuran to give dark red ((t)Bu(2)P)(2)La(&mgr;-P(t)Bu(2))(2)Li(thf)] (1). Yb(OSO(2)CF(3))(3) reacts with LiP(t)Bu(2) in tetrahydrofuran in a 1:5 ratio to produce Yb(&mgr;-P(t)Bu(2))(2)Li(thf)](2) (2) and 1/2 an equiv of (t)Bu(2)P-P(t)Bu(2). Both 1 and 2 crystallize in the monoclinic space group P2(1)/c. Crystal data for 1 at 214 K: a = 11.562 (1) ?, b = 15.914 (1) ?, c = 25.373 (3) ?, beta = 92.40 (1) degrees; V = 4664.5 ?(3); Z = 4; D(calcd) = 1.137 g cm(-)(3); R(F)() = 2.61%. Crystal data for 2 at 217 K: a = 21.641 (2) ?, b = 12.189 (1) ?, c = 20.485 (2) ?, beta = 109.01 (1) degrees; V = 5108.9 ?(3); Z = 4; D(calcd) = 1.185 g cm(-)(3); R(F)() = 2.80%. The molecular structures of 1 and 2 show the four-coordinate lanthanide atoms in distorted tetrahedral environments. These complexes are the first representatives of the lanthanide elements surrounded by four only-phosphorus-containing substituents. The main features of the crystal structure of 1 are the shortest La-P distances (2.857(1) and 2.861(1) ?) reported so far and a three-coordinate lithium cation. The molecular structure of 2 represents a divalent bis "ate" complex with two three-coordinate lithium cations. Complex 2 shows photoluminescent properties. VT NMR spectra ((7)Li and (31)P) are reported for 1and 2.