Exploration of Solid-State Solution-State Structure in Contact Ion Pair Systems: Synthesis, Characterization, and Solution-State Dynamics of Zinc Diphenyl Phosphate, [Zn{OP(OPh)}], Donor-Base-Supported Complexes.

A family of zinc phosphate complexes supported by nitrogen donor-base ligands have been synthesized, and their molecular structures were identified in both the solid (X-ray crystallography) and solution state (DOSY NMR spectroscopy). [Zn{OP(OPh)}] (), formed from the reaction of Zn[N(SiMe)] with HO(O)P(OPh) coordinates to donor-base ligands, , pyridine (Py), 4-methylpyridine (4-MePy), 2,2-bipyridine (bipy), tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), and 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me-TAC), to produce polymeric 1D structures, [(Py)Zn{OP(OPh)}] () and [(4-MePy)Zn{OP(OPh)}] (), the bimetalic systems, [(Bipy)Zn{OP(OPh)}] (), [(TMEDA)Zn{OP(OPh)}] (), and [(Me-TAC)Zn{OP(OPh)}] (), as well as a mono-nuclear zinc bis-diphenylphosphate complex, [(PMDETA)Zn{OP(OPh)}] (). H NMR DOSY has been used to calculate averaged molecular weights of the species. Studies are consistent with the disassembly of polymeric into the bimetallic species [(Me-Py)·Zn{OP(OPh)}], where the Me-Py ligand is in rapid exchange with free Me-Py in solution. Further H DOSY NMR studies of and reveal that dissolution of the complex results in a monomer dimer equilibrium, , [(Bipy)Zn{OP(OPh)}] ⇆ 2[(Bipy)Zn{OP(OPh)}] and [(TMEDA)Zn{OP(OPh)}] ⇆ 2[(TMEDA)Zn{OP(OPh)}], respectively, in which the equilibria lie toward formation of the monomer. As part of our studies, variable temperature H DOSY experiments (223 to 313 K) were performed upon in -tol, which allowed us to approximate the enthalpy [Δ = -43.2 kJ mol (±3.79)], entropy [Δ = 109 J mol K (±13.9)], and approximate Gibbs free energy [Δ = 75.6 kJ mol (±5.62) at 293 K)] of monomer-dimer equilibria. While complex is shown to maintain its monomeric solid-state structure, H DOSY experiments of at 298 K reveal two separate normalized diffusion coefficients consistent with the presence of the bimetallic species [(TAC)Zn{OP(OPh)}], ( = 1 or 0) and free TAC ligand.