Yttrium and lanthanide diphosphanylamides: syntheses and structures of complexes with one [(Ph2P)2N]- ligand in the coordination sphere

Treatment of the recently reported potassium salt [K(thf)(n)][N(PPh(2))(2)] (n=1.25, 1.5) with anhydrous yttrium or lanthanide trichlorides in THF leads after crystallization from THF/n-pentane (1:2) to the monosubstituted diphosphanylamide complexes [LnCl(2)[(Ph(2)P)(2)N](thf)(3)] (Ln=Y, Sm, Er, Yb). The single-crystal X-ray structures of these complexes show that the metal atoms are surrounded by seven ligands in a distorted pentagonal bipyramidal arrangement, in which the chlorine atoms are located in the apical positions. The diphosphanylamide ligand is always eta(2)-coordinated through the nitrogen atom and one phosphorus atom. Further reaction of [SmCl(2)[(Ph(2)P)(2)N](thf)(3)] with K(2)C(8)H(8) or reaction of [LnI(eta(8)-C(8)H(8))(thf)(3)] with [K(thf)(n)][N(PPh(2))(2)] in THF gives the corresponding cyclooctatetraene complexes [Ln[(Ph(2)P)(2)N](eta(8)-C(8)H(8))(thf)(2)] (Ln=La, Sm). The single crystals of these compounds contain enantiomerically pure complexes. Both compounds adopt a four-legged piano-stool conformation in the solid state. The structures of the A and the C enantiomers were established by single-crystal X-ray diffraction. The more soluble bistrimethylsilyl cyclooctatetraene complex [Y[(Ph(2)P)(2)N](eta(8)-1,4-(Me(3)Si)(2)C(8)H(6))(thf)(2)] was obtained by transmetallation of Li(2)[1,4-(Me(3)Si)(2)C(8)H(6)] with anhydrous yttrium trichloride in THF followed by the addition of one equivalent of [K(thf)(n)][N(PPh(2))(2)]. The (89)Y NMR signal of the complex is split up into a triplet, supporting other observations that the phosphorus atoms are chemically equivalent in solution and, thus, dynamic behavior of the ligand in solution can be anticipated.