Synthesis, structure and spectroscopic properties of novel half-sandwich nickel(II) complexes with less hindered hydrotris(pyrazolyl)borate ligand

Abstract

This paper presents the syntheses, crystal structures and spectroscopic properties of a series of half-sandwich nickel(II) complexes with hydrotris(3,5-dimethylpyrazolyl)borate and azide or thiocyanate, [Tp*Ni(pz)* 2(N 3)] ( 1), [Tp*Ni(pz*)(SCN)(H 2O)] ( 2) and [Tp*Ni(SCN)(CH 3OH) 2] ( 3) (Tp*: hydrotris(3,5-dimethylpyrazolyl)borate; pz*: 3,5-dimethylpyrazole). Compound 1 crystallizes in the triclinic system, P 1 ̄ space group (No. 2), a=10.2957(11) Å, b=11.5080(12) Å, c=13.6748(15) Å, α=81.993(2)°, β=72.999(2)°, γ=74.533(2)°, Z=2, R 1=0.0454, wR 2=0.1272. The nickel(II) ion in 1 is coordinated to six nitrogen atoms of Tp* and azide ion to form a distorted N 6 octahedron. The structure of 2 is roughly determined by X-ray crystal diffraction and shown two structurally independent [Tp*Ni(pz)(SCN)(H 2O)] units. The nickel(II) ion in 2 is six-coordinated to five nitrogen atoms of Tp*, pz*, thiocyanate and one oxygen atom of water molecule to form a N 5O octahedral environment. Compound 3 crystallizes in the monoclinic system, P2 1/ c space group, a=13.416(4) Å, b=11.964(3) Å, c=14.636(4) Å, β=96.195(5)°, Z=4, R 1=0.0379, wR 2=0.1079 . The coordination environment of nickel(II) ion in 3 is better to be described as the N 4O 2 octahedron made up of three nitrogen atoms of Tp*, one nitrogen atom of thiocyanate and two oxygen atoms of coordinated methanol molecules. The half-sandwich compound [Tp*Ni(η 2-O 2N)(CH 3OH)] 4 ( 4), which has been previously reported in a short communication, has the nickel(II) center with N 3O 3 coordination environment. The influences of N 3 −, SCN − and NO 2 − in all these half-sandwich nickel(II) complexes were discussed in this paper.