Eight-co-ordination in lanthanide pyrazolylborate chemistry: crystal structures of [LaTp^M^e^,^M^e~2(MeCN)-(O~3SCF~3)]�eCN, [NdTp^M^e^,^M^e~2^-(MeCN)~2][O~3SCF~3] and [LaTp^M^e^,^M^e~2^-(NO~3)]�eCN [Tp^M^e^,^M^e = tris(3,5-dimethylpyrazolyl)hydroborate]