Alkali‐Metal Pyrazolate Complexes with Unusual Pyrazolate Coordination Modes and Pseudocubane Motifs

The dimeric complex [Li(Ph 2 pz)(OEt 2 )] 2 ( 1 ) and tetrameric cluster [Na(Ph 2 pz)(thf)] 4 ( 2 ) were prepared by treatment of alkali‐metal reagents ( n BuLi and Na{N(SiMe 3 ) 2 }, respectively) with 3,5‐diphenylpyrazole (Ph 2 pzH) in Et 2 O ( 1 ) or THF ( 2 ). The polymer [Na( t Bu 2 pz)] n ( 3 ) was obtained from reaction at elevated temperature in a sealed tube between Na metal and 3,5‐di‐ tert ‐butylpyrazole ( t Bu 2 pzH). The complex [Na 4 ( t Bu 2 pz) 2 (thf) 3 (obds)] 2 ( 4 ; obds=(OSiMe 2 ) 2 O) was obtained as a minor product from prolonged treatment of t Bu 2 pzH with elemental sodium in a silicone‐greased flask. All four alkali‐metal pyrazolato complexes were characterized by IR and 1 H NMR spectroscopy and X‐ray crystallography.The Li dimer 1 displays μ‐η 2 :η 1 lithium–pyrazolato binding, in which both lithium atoms are four‐coordinate. Room‐ and variable‐temperature NMR studies ( 1 H, 13 C, and 7 Li) of 1 suggest similar behavior in solution, with peaks coalescing at low temperatures. Complexes 2 and 4 display distorted cubane structures. In 2 , all the sodium atoms are five‐coordinate, whereas 4 contains two sodium/pyrazolate/thf clusters (4:2:3 ratio) bridged by two obds 2− units, as well as two four‐coordinate and two five‐coordinate sodium atoms. Compound 3 is composed of two independent chains with the unusual coordination modes μ 3 ‐η 5 :η 2 :η 2 , μ 3 ‐η 5 :η 2 :η 1 , and μ 3 ‐η 4 :η 2 :η 1 , with five‐, six‐, and seven‐coordinate sodium atoms. Two oxo‐centered M 8 cage complexes [( t Bu 2 pz) 6 Li 8 O] ( 5 ) and [( t Bu 2 pz) 6 Na 8 O] ( 6 ) were obtained as by‐products from attempted preparation of [Li( t Bu 2 pz)] and [Na( t Bu 2 pz)], respectively, and their structures were determined.