Heteroleptic diphenylamido complexes of ytterbium: syntheses and molecular structures of (MeC5H4)2YbNPh2(THF) and (C5Me5)2YbNPh2

Reaction of ytterbocene chloride with NaNPh2 in THF or toluene–THF at 0°C yielded the neutral diphenylamido complexes (MeC5H4)2YbNPh2(THF) (1), (t-BuC5H4)2YbNPh2(THF) (2) and (C5Me5)2YbNPh2 (3) in good yields. The crystal structures of 1 and 3 were identified by X-ray diffraction analysis. Complex 1 has a distorted tetrahedral arrangement around ytterbium by two MeC5H4 groups, one oxygen atom and one nitrogen atom [orthorhombic, space group Pbca (no. 61); a=15.188(1), b=18.145(1), c=17.444(1) Å; V=4807.3(5) Å3, Z=8, Dcalc.=1.579 g cm−3]. The crystal structure of 3 [monoclinic, space group P21/n; a=15.834(2), b=9.992(2), c=18.504(3) Å; β=104.060(10)°, V=2839.9(8) Å3, Z=4, Dcalc.=1.431 g cm−3] shows a triangular array of two C5Me5 groups and one nitrogen atom surrounding ytterbium with additional intramolecular Ybη2-Ph chelate interactions [YbC=2.986(6) and 3.053(6) Å]. The complexes 1 and 2 exhibit good catalytic activity for the polymerization of methyl methacrylate.