NCN Pincer‐Type Complexes of Group X Metals Bearing 1,3‐Di(5‐butylpyrazol‐3‐yl)benzene Ligands

Pincer‐type 1,3‐di(5‐butylpyrazol‐3‐yl)benzene ligands are synthesized by double Claisen condensation, followed by ring closure with hydrazine hydrate. Complexes of these ligands with Group X metals are obtained by C–H bond activation with platinum dichloride or by oxidative addition to Pd(0) and Ni(0) precursors using a brominated ligand. These reactions yield complexes [Pt(L)Cl] and [M(L)Br] (M = Pd or Ni) in an analytically pure form. All three complexes are investigated by X‐ray structure analysis, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. Structure analyses reveal a square planar coordination environment around the metal atoms with short M‐C distances (Pt‐C of 1.973(6), Pd‐C of 1.936(9), and Ni‐C of 1.867(8) Å). The luminescence of the platinum complex is investigated in both the solid state and solution. The [LPdCl] and [LNiCl] complexes do not exhibit luminescence properties. Visible excitations of [LNiCl] from 330 to 420 nm and of [LPdCl] of 310—334 nm are measured. The results of density functional theory (DFT) and time‐dependent density functional theory (TDDFT) calculations are consistent with the experimental data.