Concept for Enhancement of the Stability of Calcium-Bound
Pyrazolyl-Substituted Methanides
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Abstract
Metalation
of bis(3-thiophen-2-ylpyrazol-1-yl)phenylmethane [<b>2</b>,
which is accessible from the reaction of bis(3-thien-2-ylpyrazol-1-yl)methanone
(<b>1</b>) with triphosgene] with [(thf)<sub>2</sub>Ca{N(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>] in tetrahydrofuran and subsequent
crystallization from a mixture of toluene and 1,2-dimethoxyethane
yield [(dme)Ca{C(Pz<sup>th</sup>)<sub>2</sub>Ph}{N(SiMe<sub>3</sub>)<sub>2</sub>}] (<b>3</b>). The α,α-bis(3-thiophen-2-ylpyrazol-1-yl)benzyl
ligand exhibits a κ<sup>2</sup><i>N</i>,κ<i>C</i>-coordination mode with a Ca–C σ-bond length
of 262.8(2) pm. The crystalline compound is stable if air and moisture
is strictly excluded; however, in solution; this calcium complex slowly
degrades
