Eight-co-ordination in lanthanide pyrazolylborate chemistry: crystalstructures of[LaTpMe,Me2(MeCN)(O3SCF3)]·MeCN,[NdTpMe,Me2(MeCN)2][O3SCF3] and[LaTpMe,Me2(NO3)]·MeCN[TpMe,Me = tris(3,5-dimethylpyrazolyl)hydroborate]

The reaction of [LnTp Me,Me 2 ][O 3 SCF 3 ] [Ln = La, Ce, Pr or Nd; Tp Me,Me = tris(3,5-dimethylpyrazolyl) hydroborate] in toluene with acetonitrile gave complexes of stoichiometry LnTp Me,Me 2 (MeCN) 2 (O 3 SCF 3 ) (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 isomers of each other: [LaTp Me,Me 2 (MeCN)(O 3 SCF 3 )] ·MeCN consists of neutral molecules while [NdTp Me,Me 2 (MeCN) 2 ][O 3 SCF 3 ] adopts an ionic structure. The structure of [LaTp Me,Me 2 (NO 3 )] has been determined for comparison. The co-ordination environment of the metal centres in all three complexes was shown by polytopal analysis to be dodecahedral in contrast to that (square antiprismatic) commonly adopted by complexes involving unsubstituted hydrotris(pyrazolyl)borate.