Divalent Lanthanide Phosphides. Synthesis and X-ray Crystal Structure Determination of Yb [PPh 2 ] 2 (N-MeIm) 4 : The Missing Link

Abstract

YbI₂(thf)₂ reacts with two equiv of KPPh₂ in tetrahydrofuran to give Yb[PPh₂]₂ (thf)₄, 1.1 can also be obtained from the reaction of YbI₃(thf)₃ with KPPh₂ in tetrahydrofuran in a 1:3 ratio with half an equiv of Ph₂P-PPh₂ as a byproduct as well as from Yb[N(SiMe₃)₂]₂ (thf)₂ and two equiv of Ph₂PH in tetrahydrofuran. 1 can be converted to Yb [PPh₂]₂(N-MeIm)₄, 2, in tetrahydrofuran using four equiv of the strong donor ligand N-methylimidazole (N-MeIm). 2 crystallizes in space group P2₁/n. Crystal data for 2 at 217 K: a = 9.881 (l) Å, b = 17.717 (2) Å, c = 11.153 (2) Å, β = 95.61 (1)°; V = 1943.1 (5) ų; Z = 2; D_calcd = 1.490 g cm⁻³; R_F = 2.01%. The structure of 2 shows the hexacoordinate ytterbium atom, which lies on an inversion center, in a slightly distorted octahedral environment with two phosphido ligands in trans positions. A significant feature of the molecular structure of 2 is the only slightly pyramidal configuration of the metal-coordinated phosphorus atoms (sum of angles: 343.9°).