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The mechanism for the hydrolysis of the methyl phosphate anion was studied using high-level ab initio and density functional theory methods. Starting from the molecular species CH3OPO3H-, CH3OPO3H-·(H2O), and CH3OPO3H-·(H2O)2, gas phase reaction coordinates of the proposed mechanisms were followed. Solvation free energies were evaluated using the polarizable continuum model (PCM) at the stationary point geometries. The dissociative mechanism, which involves the formation of a metaphosphate ion (PO3 -), is found to be more favorable than the associative mechanism, which involves a pentacoordinated intermediate, both in the gas phase and in aqueous solution. In the dissociative mechanism, the first step is rate determining. The computed free energy of activation in solution is within 1.7 kcal/mol of the experimentally determined activation free energy for hydrolysis. The first step and the second step in the dissociative mechanism are each shown to proceed via a six-centered water-assisted transition state.

The ligand precursor [LH2]2+·2Br- (1) for the bis(NHC) ligand with N-picolyl moieties is synthesized in 83% yield. Complexation of 1 with palladium and nickel acetates produced [PdL]2+·2Br- (2) and [NiL]2+·2Br- (3), respectively, in quantitative yields. Metathesis reactions of 2 and 3 with AgPF6 give the corresponding bromide-free complexes [PdL]2+·2PF6 - (4) and [NiL]2+·2PF6 - (5). Complexes 2−4 were characterized by X-ray structural determinations, which reveal a highly twisted helical coordination of L around the metal ions. In solution, however, the tetradentate chelate ring undergoes a rapid fluxional process of ring twisting. A theoretical study confirms that the tetradentate coordination of L in 2 and 3 is energetically more favorable than the bidentate chelation mode with dangling picolyl groups. A preliminary application of [NiL]2+·2Br- in Suzuki coupling of aryl halides with phenylboronic acid shows effective activity.

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Photodissociative experiments were performed on Cu+−C5H5N and Ag+−C5H5N complexes in the gas phase. The dissociative ligand-to-metal charge-transfer fragments, pyridine+, were observed for both complexes. Photodissociation spectra were recorded as a function of laser wavelength. Two continuous, structureless bands were investigated in each complex. Because of the low-energy 2D state of the Cu atom, the Cu+−pyridine dissociative process is more complicated. Several possible mechanisms for this process have been discussed. The binding energies were determined experimentally to be 65.5 and 45.2 kcal/mol for Cu+−pyridine and Ag+−pyridine, respectively. M+−C5H5N (M = Cu or Ag) complexes also were studied theoretically using the HF, MP2, and B3LYP methods. All complexes under study show C 2 v symmetry. The binding energies predicted from the theoretical calculations were less than the experimental values, which were derived from the onset of the charge-transfer appearance combined with the IP (ionization potential). The complexes containing Cu+ and Ag+ are characterized predominantly by electrostatic interactions.