ORGANOAMIDO-LANTHANOIDS AND ARYLOXO-LANTHANOIDS .10. RIS(ETA-2-3,5-DI-T-BUTYLPYRAZOLATO)LANTHANOID(III) COMPLEXES AND THE X-RAY CRYSTAL-STRUCTURE OF ER(ETA-2-BUT2PZ)3(THF)2

The complexes Ln(But2pz)3(thf)2 (Ln = Y, La, Pr, Nd, Sm, Gd, Dy, Er, Y b, Lu; But2pz- = 3,5-di-t-butylpyrazolate; thf = tetrahydrofuran), and [Ln(But2pz)3(OPPh3)2].(dme). (Ln = La, n = 2/3; Ln = Er, n = 1; dme = 1,2-dimethoxyethane) have been prepared by reaction of the anthanoid metal with bis(pentafluorophenyl)mercury and the corresponding pyrazol e in either thf, or 2 in dme in the presence of triphenylphosphine oxi de. The X-ray crystal structure of Er(eta2-But2pz)3(thf)2 [monoclinic, space group P2(1) (No. 4), a 9.738(4), b 19.602(4), c 11.636(4) angst rom, beta 99.42(3)degrees, R 0.0374 for 3667 observed reflections] sho ws the complex to be an eight-coordinate monomer with three chelating But2PZ ligands. The arrangement of centres (Cen) of the N-N bonds of t he But2pz ligands [<Er-N> 2.336 angstrom; Cen-Er-Cen 140.1(4)degrees, 110.3(4)degrees and 109.6(4)degrees] and the thf oxygen atoms [<Er-O> 2.351 angstrom; O-Er-O 140.1(4)degrees] is intermediate between trigon al bipyramidal and square pyramidal. The other Ln(But2pz)3(thf)2 compl exes and Ln(But2pz)3(OPPh3)2 are considered to have similar structures .