A novel bonding mode of tetrazolate ligand to a metal:: synthesis and structural characterization of 5-phenyltetrazolate organolanthanide complexes:: [{(C5H4Me)(C5H5)LnTz}2][{(C5H4Me)2LnTz}2] (Ln=Dy, Gd) and [(C5H4Me)2LnTz)]2 (Ln=Yb, Er)

Reaction of (C5H4Me)(3)Ln and TzH (5-phenyl-1H-tetrazole) in THF affords complexes [(C5H4Me)(2)LnTz](2) [Ln = Yb (1), Er (2)]. 1 crystallized in the space group C2/c, with unit cell dimensions a = 25.596(2), b = 8.342(1), c = 21.573(2) Angstrom, beta = 129.322(9)degrees V = 3563.5(8) Angstrom(3) and Z = 8 for D-c = 1.776 g cm(-3). Least-squares refinement of the model based on 2700 reflections converged to a final R = 0.031. The molecule is centrosymmetric dimer in which each ytterbium atom is coordinated by two methylcyclopentadienyl groups and three nitrogen atoms of the bridging Tz ligands to form a distorted trigonal-bipyramidal geometry. When there is a small amount of (C5H4Me)(2)Ln(C5H5) in (C5H4Me)(3)Ln, the 1:1 complexes [{(C5H4Me)(C5H5)LnTz}(2)] [{(C5H4Me)(2)LnTz}(2)] (Ln = Dy (3), Gd (4)) were obtained in crystalline form. 3 and 4 crystallize as isomorphous crystals of space group P (1) over bar with the following unit cell parameters (3/4): a = 9.374(2)/9.420(4), b = 13.048(2)/13.215(4), c = 16.542(4)/16.677(5) Angstrom, a = 86.95(2)/87.24(2), beta = 74.61(1)/74.50(3), gamma = 77.31(1)/77.08(3)degrees, Y = 1903(1)/1950(1) Angstrom(3), Z = 2, D-c = 1.602/1.545 g cm(-3) R = 0.046/0.051. Crystallographic data for 3 and 4 show that there are two disconnected structural units [(C5H4Me)(C5H5)Ln(mu-eta(1):eta(2)-Tz)](2) and [(C5H4Me)(2)Ln(mu-eta(1):eta(2)-Tz)](2), crystallizing in one asymmetrical unit, each of which is tetrazolate-bridged dimer and has an inversion center. The bridging unit Ln(2)N(6) is planar. All three structures reveal an unusual bonding mode of the tetrazolate ligand, in which the tetrazolate group acts as both a bridging and chelating ligand, with the nitrogen atoms at 1, 2 and 3-position taking part in bonding. (C) 1998 Elsevier Science S.A. All rights reserved.