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

The dimeric complex [Li(Ph₂pz)(OEt₂)]₂ ( 1 ) and tetrameric cluster [Na(Ph₂pz)(thf)]₄ ( 2 ) were prepared by treatment of alkali‐metal reagents (nBuLi and Na{N(SiMe₃)₂}, respectively) with 3,5‐diphenylpyrazole (Ph₂pzH) in Et₂O ( 1 ) or THF ( 2 ). The polymer [Na(tBu₂pz)]_n ( 3 ) was obtained from reaction at elevated temperature in a sealed tube between Na metal and 3,5‐di‐tert‐butylpyrazole (tBu₂pzH). The complex [Na₄(tBu₂pz)₂(thf)₃(obds)]₂ ( 4 ; obds=(OSiMe₂)₂O) was obtained as a minor product from prolonged treatment of tBu₂pzH with elemental sodium in a silicone‐greased flask. All four alkali‐metal pyrazolato complexes were characterized by IR and ¹H NMR spectroscopy and X‐ray crystallography.The Li dimer 1 displays μ‐η²:η¹ lithium–pyrazolato binding, in which both lithium atoms are four‐coordinate. Room‐ and variable‐temperature NMR studies (¹H, ¹³C, and ⁷Li) 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 μ₃‐η⁵:η²:η², μ₃‐η⁵:η²:η¹, and μ₃‐η⁴:η²:η¹, with five‐, six‐, and seven‐coordinate sodium atoms. Two oxo‐centered M₈ cage complexes [(tBu₂pz)₆Li₈O] ( 5 ) and [(tBu₂pz)₆Na₈O] ( 6 ) were obtained as by‐products from attempted preparation of [Li(tBu₂pz)] and [Na(tBu₂pz)], respectively, and their structures were determined.