Diacetylplatinum(II) Complexes with κ2‑Coordinated Tris(pyridyl)methanol and Tris(pyridyl)methyl Ether Ligands: Structural Insight into the Ligand Dynamics in Solution

Reactions of the bis­(benzylamine)­platinum­(II) complex [Pt­(COMe)2(NH2Bn)2] (2; Bn = benzyl) with (2-py)3COR (2-py = 2-pyridyl), (2-py)2PhCOR, and (2-py)2(m-Tol)­COR (m-Tol = 3-methylphenyl) afforded the neutral diacetylplatinum­(II) complexes [Pt­(COMe)2{(2-py)3COR}] (R = H (3a), Me (3b), Et (3c), Bn (3d)), [Pt­(COMe)2{(2-py)2PhCOR}] (R = H (4a), Me (4b)), and [Pt­(COMe)2{(2-py)2(m-Tol)­COR}] (R = H (5a) Me (5b)), respectively, having, due to a κ2 coordination of the ligands, a 2-pyridyl (3), a phenyl (4), or a m-tolyl (5) ring as the pendant group. The identities of all complexes were unambiguously proved by high-resolution mass spectrometric investigations and by NMR (1H, 13C, 195Pt) and IR spectroscopy as well as by single-crystal X-ray diffraction analyses (3a–d). In methanol solution, complexes 3b–d and 5b show a dynamic behavior. The thermodynamic parameters of these dynamics have been determined by variable-temperature 1H NMR measurements (Eyring plots). Furthermore, extensive DFT calculations will be presented, which indicate that the dynamics are caused by the interplay of hindered and respectively unhindered rotations of the substituent R and/or the pendant group.