Pseudotetrahedral scorpionato halide complexes [(TpPh,Me) Ni-X] [TpPh,Me = hydrotris(3-phenyl-5-methyl-1-pyrazolyl) borate] were synthesized by metathesis of Tl(TpPh,Me) and NiX2 (X = Cl, Br, I). Pyrazole adducts [(TpPh,Me)Ni(HpzPh,Me) (X)] (X = Cl, I) were also obtained. [(TpPh,Me)Ni-X] (X = Br, I) are isomorphous with previously reported [(TpPh,Me)Ni-Cl], and a new solvated pseudo-polymorph [(TpPh,Me)Ni- Cl]·2CH2Cl2 was found in this work. Ni-X bond lengths correspond to ionic radii of the halide ions, but some variations in Ni-Cl and Ni-N bond lengths are respectively attributed to bending of the chloride from the ideal threefold HB⋯Ni axis and to the size of the 3-pyrazole substituents. Electronic spectra were rationalized by means of time-dependent (TD) DFT calculations on simplified C3v-symmetric [(Tp)Ni-X] models. Exogenous pyrazole binds to give the pentacoordinate adducts [(TpPh,Me)Ni(HpzPh,Me)(X)] (X = Cl, I). We obtained a crystal structure of the iodide adduct, as well as that of [(TpPh,Me)Ni(HpzPh,Me)(Cl)]·0.5MeCN, isomorphous with a previously reported aquo monosolvate. A hallmark of adduct formation is an intramolecular N-H⋯X hydrogen bond between the added pyrazole and the adjacent halide ligand, thus giving rise to a strong IR absorption band. The stretching frequency correlates to the N(H)⋯X separation for the range of known adducts.
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- Density functional calculations