Versatile Coordination Behavior of the Asymmetric Bis(3‐mesityl‐pyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) Hydroborate Ligand towards Late 3 d M2+ Ions.

Bearing in mind the potential which tris(pyrazolyl) hydroborate ligands have demonstrated in various different fields of coordination chemistry, the behavior of a more rarely employed representative, namely bis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) hydroborate (TpMes,H*), towards a series of divalent metal ions has been investigated. Thus, the synthesis of two new heteroleptic metal chlorido [TpMes,H*MCl] complexes, 2, (Mn2+, 2‐a, and Cu2+, 2‐e) are described, which correspond to the typical precursor compounds that would be needed for subsequent research. Structural and spectroscopic properties of the two new and four published members of this series (M=Fe2+, 2‐b, Co2+, 2‐c, Ni2+, 2‐d, Zn2+, 2‐f) are discussed in detail for the solid and solution states. Furthermore, synthetic routes to five homoleptic [(TpMes,H*)2M] complexes, 3, bearing Mn2+, 3‐a, Fe2+, 3‐b, Co2+, 3‐c, Ni2+, 3‐d, and Cu2+, 3‐e, ions as well as an alternative preparation method for [(κ2‐TpMes,H*)2Zn], 3‐f, are described. Their structures and spectroscopic parameters are compared to those of their heteroleptic counterparts. Additionally, the complex [(TpH,Mes*)2Cu], 4, is reported, representing the second example of a complex with the (3‐mesitylpyrazol‐1‐yl)bis(5‐mesitylpyrazol‐1‐yl) hydroborate ligand (TpH,Mes*). [ABSTRACT FROM AUTHOR]