Abstract
A series of 3,5‐diisopropylpyrazolates of magnesium, calcium, and strontium in addition to a divalent europium analog continues our investigation on the differences and similarities between the alkaline earth and divalent rare earth metal elements. The alkane elimination reaction between dibutylmagnesium and excess 3,5‐diisopropylpyrazole (__i__Pr~2~pzH) in toluene afforded the dinuclear magnesium pyrazolate [{Mg(__i__Pr~2~pz)~2~(__i__Pr~2~pzH)}~2~] (1). [{Ca(__i__Pr~2~pz)~2~(__i__Pr~2~pzH)~2~}~2~] (2) and [{Eu(__i__Pr~2~pz)~2~(__i__Pr~2~pzH)~2~}~2~] (3) were obtained as the product of redox‐transmetallation/ligand‐exchange reactions between an excess of the corresponding metal, 2 equiv. of __i__Pr~2~pzH, and Hg(C~6~F~5~)~2~ in toluene. This reaction with Sr metal led to the isolation of a unique byproduct, [Hg~3~(__i__Pr~2~pz)~4~(C~6~F~5~)~2~] (4). High‐temperature direct metallation of barium with __i__Pr~2~pzH afforded [{Ba(i__Pr~2~pz)~2~(py)~3~}~2~] (5) upon treatment of the hydrocarbon‐insoluble homoleptic [{Ba(i__Pr~2~pz)~2~}~n~] with pyridine (py). X‐ray crystal structure analyses revealed dinuclear structures for compounds 1–3 and 5 with μ‐η^n^:η^m^ bridging pyrazolato ligands, including the new μ‐η^1^:η^5^ linkage, and further stabilization of 1–3 by intramolecular hydrogen bonding between the terminal pyrazole donor and terminal 1 or bridging pyrazolato ligands in 2 and 3. The trinuclear 4 displays the first example of a complex with an open, triangular Hg~3~ unit. It has μ‐η^1^:η^1^ bridging pyrazolato ligands and terminal pentafluorophenyl groups.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)