Alkali-Metal Complexes of a Tetramethylcyclopentadienyl-Functionalized Pyrazolylborate Ligand. Structures of [Li₂(THF)₃B(3-Mepz)₃(C₅Me₄)] and [K₂(THF)₂B(3-Mepz)₃(C₅Me₄)]_∞

The new dianionic ligand [B(3-Mepz)3(C5Me4)]2- was prepared and structurally characterized as its lithium and potassium salts. In the solid state, [Li2(THF)3{B(3-Mepz)3}(C5Me4)] is monomeric, while [K2(THF)2{B(3-Mepz)3}(C5Me4)]∞ consists of infinite puckered chains. The compounds were synthesized by reaction of B(NMe2)2(C5Me4H) with 2 equiv of 3-methylpyrazole and 1 equiv of M(3-Mepz) (M = Li, K) followed by deprotonation with n-BuLi or KH. The crystal structure of the intermediate monoanion, [Li(THF)2{B(3-Mepz)3}(C5Me4H)], is also presented.