Metathesis between [{(Me3Si)(2)CH) (C6H4-2-OMe)P]K and SmI2(THF)(2) in THF yields [{([Me3Si](2)CH)(C6H4-2-OMe)P)(2)Sm(DME)(THF)] (1), after recrystallization. A Similar reaction between [{(Me3Si)(2)CH}(C6H3-2-OMe3-Me-3-Me)P]K and SmI2(THF)(2) yields [{([Me3Si](2)CH)(C6H3-2-OMe-3-Me)P}(2)Sm(DME)]. EtO2 (2), while reaction between [{(Me3Si)(2)CH}(C6H4-2-CH2NMe2)P]K and either SmI2(THF)(2) or YbI2 yields the five-coordinate complex [{([Me3Si](2)CH)(C6H4-2-CH2NMe2)P}(2)Sm(THF)] (3) or the solvent-free complex [{([Me3Si](2)CH)(C6H4-2-CH2NMe2)P}(2)Yb] (4), respectively. X-ray crystallography shows that complex 2 adopts a distorted cis octahedral geometry, while complex 1 adopts a distorted pentagonal bipyramidal geometry (1, triclinic, P (1) over bar, a = 11.0625(9) Angstrom, b = 15.924(6) Angstrom, c = 17.2104(14) Angstrom, alpha = 72.327(2)degrees, beta = 83.934(2)degrees, gamma = 79.556(2)degrees, Z = 2; 2, monoclinic, p2(1), a = 13.176(4) Angstrom, b = 13.080(4) Angstrom, c = 14.546(4) Angstrom, beta = 95.363(6)degrees, Z = 2). Complex 3 crystallizes as monomers with a square pyramidal geometry at Sm and exhibits short contacts between Sm and the ipso-carbon atoms of the ligands (3, monoclinic, C2/c, a = 14.9880(17) Angstrom, b = 13.0528(15) Angstrom, c = 24.330(3) Angstrom, beta = 104.507(2)degrees, Z = 4). Whereas preliminary X-ray crystallographic data for 4 indicate a monomeric structure in the solid state, variable-temperature H-1, C-13{H-1}, P-31{H-1}, and Yb-171 NMR spectroscopies suggest that 4 undergoes an unusual dynamic process in solution, which is ascribed to a monomer-dimer equilibrium in which exchange of the bridging and terminal phosphide groups may be frozen out at low temperature.