Abstract
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{O2P(OPh)2}2]∞ (1), formed from the reaction of Zn[N(SiMe3)2]2 with HO(O)P(OPh)2 coordinates to donor-base ligands, i.e., pyridine (Py), 4-methylpyridine (4-MePy), 2,2-bipyridine (bipy), tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), and 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3-TAC), to produce polymeric 1D structures, [(Py)2Zn{O2P(OPh)2}2]∞ (2) and [(4-MePy)2Zn{O2P(OPh)2}2]∞ (3), the bimetalic systems, [(Bipy)Zn{O2P(OPh)2}2]2 (4), [(TMEDA)Zn{O2P(OPh)2}2]2 (5), and [(Me3-TAC)Zn{O2P(OPh)2}2]2 (7), as well as a mono-nuclear zinc bis-diphenylphosphate complex, [(PMDETA)Zn{O2P(OPh)2}2] (6). 1H NMR DOSY has been used to calculate averaged molecular weights of the species. Studies are consistent with the disassembly of polymeric 3 into the bimetallic species [(Me-Py)2·Zn2{O2P(OPh)2}4], where the Me-Py ligand is in rapid exchange with free Me-Py in solution. Further 1H DOSY NMR studies of 4 and 5 reveal that dissolution of the complex results in a monomer dimer equilibrium, i.e., [(Bipy)Zn{O2P(OPh)2}2]2 ⇆ 2[(Bipy)Zn{O2P(OPh)2}2] and [(TMEDA)Zn{O2P(OPh)2}2]2 ⇆ 2[(TMEDA)Zn{O2P(OPh)2}2], respectively, in which the equilibria lie toward formation of the monomer. As part of our studies, variable temperature 1H DOSY experiments (223 to 313 K) were performed upon 5 in d8-tol, which allowed us to approximate the enthalpy [ΔH = −43.2 kJ mol-1 (±3.79)], entropy [ΔS = 109 J mol-1 K-1 (±13.9)], and approximate Gibbs free energy [ΔG = 75.6 kJ mol-1 (±5.62) at 293 K)] of monomer-dimer equilibria. While complex 6 is shown to maintain its monomeric solid-state structure, 1H DOSY experiments of 7 at 298 K reveal two separate normalized diffusion coefficients consistent with the presence of the bimetallic species [(TAC)2-xZn2{O2P(OPh)2}4], (x = 1 or 0) and free TAC ligand.
Original language | English |
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Pages (from-to) | 4770-4785 |
Number of pages | 16 |
Journal | Inorganic Chemistry |
Volume | 62 |
Issue number | 12 |
Early online date | 14 Mar 2023 |
DOIs | |
Publication status | Published - 27 Mar 2023 |
Bibliographical note
Funding Information:A.J.S. and J.D.P. thank Infineum UK for the provision of a Ph.D. studentship and PDRA funding, respectively. A.L.J. wishes to thank the Department of Chemistry, University of Bath.
Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.
Funding
A.J.S. and J.D.P. thank Infineum UK for the provision of a Ph.D. studentship and PDRA funding, respectively. A.L.J. wishes to thank the Department of Chemistry, University of Bath.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry