Abstract
A study is presented of the thermodynamics of the halogen-bonding interaction of C F I with a series of structurally similar group 10 metal fluoride complexes trans-[Ni(F)(2-C NF )(PCy ) ] (2), trans-[Pd(F)(4-C NF )(PCy ) ] (3), trans-[Pt(F){2-C NF H(CF )}(PR ) ] (4a, R = Cy; 4bR = iPr) and trans-[Ni(F){2-C NF H(CF )}(PCy ) ] (5a) in toluene solution. F NMR titration experiments are used to determine binding constants, enthalpies and entropies of these interactions (2.4 ≤ K ≤ 5.2; -25 ≤ ΔH ≤ -16 kJ mol ; -73 ≤ ΔS ≤ -49 J K mol ). The data for -ΔH for the halogen bonding follow a trend Ni <Pd <Pt. The fluoropyridyl ligand is shown to have a negligible influence on the thermodynamic data, but the influence of the phosphine ligand is significant. We also show that the value of the spin-spin coupling constant J increases substantially with adduct formation. X-ray crystallographic data for Ni complexes 5a and 5c are compared to previously published data for a platinum analogue. We show by experiment and computation that the difference between Pt-X and Ni-X (X = F, C, P) bond lengths is greatest for X = F, consistent with F(2pπ)-Pt(5dπ) repulsive interactions. DFT calculations on the metal fluoride complexes show the very negative electrostatic potential around the fluoride. Calculations of the enthalpy of adduct formation show energies of -18.8 and -22.8 kJ mol for Ni and Pt complexes of types 5 and 4, respectively, in excellent agreement with experiment.
| Original language | English |
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| Pages (from-to) | 14338-14348 |
| Number of pages | 11 |
| Journal | Journal of the American Chemical Society |
| Volume | 133 |
| Issue number | 36 |
| DOIs | |
| Publication status | Published - 14 Sept 2011 |