The Synthesis and Structural Characterization of the Sterically Demanding Tris (3,5-di-t-butylpyrazolyl) hydroborato Ligand,[Tp Bu 2 t ]: A Highly Twisted,Propeller-Like,Ligand System

Abstract

The synthesis of the new sterically demanding tris (3,5-di-t-butylpyrazolyl) hydroborato ligand, [Tp^Bu₂t], in which both the 3- and 5-positions of the pyrazolyl group are occupied by bulky t-butyl substituents is described. The structural characterization of several derivatives, namely K [Tp^Bu₂t], Cs [TP^Bu₂t], TI [Tp^Bu₂t], [Tp^Bu₂t] ZnI, and [Tp^Bu₂t] CdI, demonstrates that the [Tp^Bu₂t] ligand adopts a highly twisted propeller-like configuration, a consequence of intra-ligand repulsive interactions between the 5-t-butyl substituents. K[Tp^Bu₂t] (C₆H₆)₂ is monoclinic, P2₁/c (No. 14), a = 20.188 (3) Å, b = 12.794 (3) Å, c = 18.666 (5) Å, β = 98.43 (2)°, V = 4769 (2) ų, Z = 4. Cs [Tp^Bu₂t] (C₆ H₆) is monoclinic, P2₁/c (No. 14), a = 13.513 (3) Å, b = 17.430 (4) Å, c = 18.437(3) Å, β = 99:38 (2)°, V = 4283 (2) ų, Z = 4. T1 [Tp^Bu₂t] is monoclinic, P2₁/c (No. 14), a = 18.644 (4) Å, b = 10.366 (3) Å, c = 20.883 (4) Å, β = 112.73 (2)°, V = 3733 (2) ų, Z = 4. [Tp^Bu₂t] ZnI is triclinic, P1 (No. 2), a = 11.095 (2) Å, b = 13.236 (4) Å, c = 13.302 (5) Å, α = 95.15 (3)°, β = 93.82 (3)°, γ = 101.55 (3)°, V= 1899 (1) ų, Z = 2. [Tp^Bu₂t]CdI (C₆H₆)_0.5 is monoclinic, P2₁/c (No. 14), a = 9.908 (2) Å, b = 18.962 (4) Å, c = 22.012 (4) Å, β = 100.84 (2)°, V = 4057 (2) ų, Z = 4.