8-CO-ORDINATION IN LANTHANIDE PYRAZOLYLBORATE CHEMISTRY - CRYSTAL-STRUCTURES OF ]CENTER-DOT-MECN,[NDTP(2)(ME,ME)(MECN)(2)][O3SCF3] AND [LATP(2)(ME,ME)(NO3)]CENTER-DOT-MECN[TP(ME,ME) EQUALS TRIS(3,5-DIMETHYLPYRAZOLYL)HYDROBORATE]

The reaction of [LnTp(2)(Me,Me)][O3SCF3][Ln = La, Ce, Pr or Nd; Tp(Me, Me) = tris(3,5-dimethylpyrazolyl)hydroborate] in toluene with acetonit rile gave complexes of stoichiometry LnTp(2)(Me,Me)(MeCN)(2)(O3SCF3) ( Ln = La, Ce, Pr or Nd). The structures of those of La and Nd have been determined by X-ray crystallography and found to be ionization isomer s of each other: [LaTp(2)(Me,Me)(MeCN)(O3SCF3)]. MeCN consists of neut ral molecules while [NdTp(2-)(Me,Me)(MeCN)(2)][O3SCF3] adopts an ionic structure. The structure of [LaTp(2)(Me,Me)(NO3)] has been determined for comparison. The co-ordination environment of the metal centres in all three complexes was shown by polytopal analysis to be dodecahedra l in contrast to that (square antiprismatic) commonly adopted by compl exes involving unsubstituted hydrotris(pyrazolyl)borate.