The Synthesis and Structural Characterization of the Sterically Demanding Tris (3,5-di-t-butylpyrazolyl) hydroborato Ligand, [Tp^Bu₂t]: A Highly Twisted, Propeller-Like, Ligand System

Article type: Research Article

Authors: Dowling, Conor M. | Leslie, Douglas | Chisholm, Malcolm H. | Parkin, Gerard

Affiliations: Department of Chemistry, Columbia University, New York, 10027 | Department of Chemistry, lndiana University, Bloomington, lndiana 47405

Note: [] Corresponding author

Abstract: The synthesis of the new sterically demanding tris (3,5-di-t-butylpyrazolyl) hydroborato ligand, [TpBu2t], 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 [TpBu2t], Cs [TPBu2t], TI [TpBu2t], [TpBu2t] ZnI, and [TpBu2t] CdI, demonstrates that the [TpBu2t] ligand adopts a highly twisted propeller-like configuration, a consequence of intra-ligand repulsive interactions between the 5-t-butyl substituents. K[TpBu2t] (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) Å3, Z = 4. Cs [TpBu2t] (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) Å3, Z = 4. T1 [TpBu2t] 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) Å3, Z = 4. [TpBu2t] 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) Å3, Z = 2. [TpBu2t]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) Å3, Z = 4.

DOI: 10.1080/13583149512331338245

Journal: Main Group Chemistry, vol. 1, no. 1, pp. 29-52, 1995