Synthesis and Structure of [TpBut2]In, a Highly Twisted [Tris(3,5-di-tert-butylpyrazolyl)hydroborato]indium(I) Complex: Comparison with the Re-Evaluated Ordered Structure of [TpBut]In

Abstract

The indium(I) complex [Tp^But₂]In ([Tp^But₂] = tris(3,5-di-tert-butylpyrazolyl)hydroborato), synthesized by the reaction of [Tp^But₂]Na with InCl, exhibits a structure in which the [Tp^But₂] ligand adopts a highly twisted configuration due to steric interactions of the tert-butyl substituents in the 5-positions of the pyrazolyl groups. In contrast, the absence of 5-tert-butyl substituents allows the pyrazolyl groups in [Tp^But]In to be coplanar with their respective In−N−N−B planes. The structure of [Tp^But]In has been previously reported but was noted to exhibit an unusual type of disorder in which a nitrogen atom of one molecule was coincident with the boron atom of its disordered configuration [Dias, H. V. R.; Huai, L.; Jin, W.; Bott, S. G. Inorg. Chem. 1995, 34, 1973−1974]. In view of the unusual nature of the disorder, which involved both a 2-fold rotation and a canting of the molecule, the disordered structure of [Tp^But]In was re-evaluated. Significantly, an ordered structure of [Tp^But]In was obtained. The disorder present in the previously reported structure is a consequence of adopting a space group with unnecessarily high symmetry. Thus, [Tp^But]In provides an example where the structure is much better described as ordered in a noncentrosymmetric space group, rather than disordered in the centrosymmetric alternative. [Tp^But₂]In is monoclinic, of space group P2₁/c (No. 14), with a = 18.781(9) Å, b = 10.380(2) Å, c = 20.849(6) Å, β = 112.76(3)°, and Z = 4. [Tp^But]In is orthorhombic, of space group Cmc2₁ (No. 36), with a = 16.193(3) Å, b = 15.214(3) Å, c = 9.963(3) Å, and Z = 4.