POLY(PYRAZOLYL)BORATE COMPLEXES OF TERBIUM, SAMARIUM, AND ERBIUM - X-RAY CRYSTAL-STRUCTURE OF ([ETA-3-HB(PZ)3]2SM(MU-O2CPH))2 (PZ = PYRAZOLYL RING)

The reaction of MC13(M = Tb, Sm, Er) with 3 equiv of K[H2B(pz)2] yields [H(µ-H)B(pz)2]3M. These complexes have properties similar to those of the yttrium analogue, which has been shown to have a trigonal-prismatic structure possessing weak agostic B-H…Y three-center interactions. The reaction of the metal halides with 2 equiv of K[HB(pz)3] yields [HB(pz)3]2MCl, shown to be monomeric in solution for M = Sm. A similar reaction, which in addition contains 1 equiv of Na(O2CCH3), yields {[HB(pz)3]2M(O2CCH3)}2. NMR spectra for all three types of these paramagnetic complexes are resolved for M = Sm and are temperature dependent, showing these molecules are fluxional in solution. The complex {[HB(pz)3]2Sm(O2CPh)j2was also prepared and the solid-state structure determined by X-ray diffraction: monoclinic, space group P21, a = 13.264 (3) υ, b = 35.821 (8) υ, c = 15.544 (4) υ, β = 115.06 (2)°, V = 6690 υ3, and Z = 4. The structure is an acetate-bridged dimer in which the geometry about the samarium atoms fails to fit any regular polyhedron. Molecular weight studies show that this complex and {[HB-(pz)3]2Sm(O2CCH3))2are dimers in benzene solution. © 1990, American Chemical Society. All rights reserved.