Absolute single-ion thermodynamic quantities of hydration at 298.15 K are derivable from the conventional enthalpies and entropies if the values of and are known. Here we suggest S¡(H aq `) * hyd H¡(H`) S¡(H aq `) \ J K~1 mol~1 based on the thermodynamics of the dissociation of water. This assignment, in turn, [5.5 corresponds to kJ mol~1 according to a self-consistent analysis of Krestov. Using these * hyd H¡(H`) \ [1078 values, as a main result, the anions are more strongly hydrated than usually thought, in line with recent calculations. Only the group 1, 2, and 15 nobel gas ions are dealt with. For each series, the conventional enthalpies and entropies are linearly related to one another. From these linear free energy relationships (LFERs) a relationship between and is derived. Further, a connection is detected between S¡(H aq `) * hyd H¡(H`) the Born radii calculated from the free energies of hydration, and the distances d, corresponding to the r B, upper limits of the experimental Ðrst peak position of the ionÈoxygen radial distribution curves, upon implication, in the case of a cation, the covalent radius of oxygen, and in the case of an anion, the water r cov radius r water ,Finally, from the di †erences between the enthalpies and free energies of hydration the temperature derivatives of the Born radii are determined.

A complete catalytic cycle for the cyclotrimerization of acetylene with the CpRuCl fragment has been proposed and discussed based on DFT/B3LYP calculations, which revealed a couple of uncommon intermediates. The first is a metallacyclopentatriene complex RuCp(Cl)(C(4)H(4)) (B), generated through oxidative coupling of two alkyne ligands. It adds another alkyne in eta(2) fashion to give an alkyne complex (C). No less than three successive intermediates could be located for the subsequent arene formation. The first, an unusual five- and four-membered bicyclic ring system (D), rearranges to a very unsymmetrical metallaheptatetraene complex (E), which in turn provides CpRuCl(eta(2)-C(6)H(6)) (F) via a reductive elimination step. The asymmetry of E, including Cp ring slippage, removes the symmetry-forbidden character from this final step. Completion of the cycle is achieved by an exothermic displacement (21.4 kcal mol(-)(1)) of the arene by two acetylene molecules regenerating A. In addition to acetylene, the reaction of B with ethylene and carbon disulfide, the latter taken as a model for a molecule lacking hydrogen atoms, has also been investigated, and several parallels noted. In the case of the coordinated alkene, facile C-C coupling to the alpha carbon of the metallacycle is feasible due to an agostic assistance, which tends to counterbalance the reduced degree of unsaturation. Carbon disulfide, on the other hand, does not coordinate to ruthenium, but a C=S bond adds instead directly to the Ru=C bond. The final products of the reactions of B with acetylene, ethylene, and carbon disulfide are, respectively, benzene, cyclohexadiene, and thiopyrane-2-thione, the activation energies being lower for acetylene.

The solvent-induced UV−vis spectral shifts in 4-nitroanisole and pyridinium N-phenoxide betaine-30 dyes utilized in the famous π* and E T(30) polarity scales, respectively, are analyzed by molecular theories in terms of long-range solute−solvent interactions due to induction, dispersion, and dipole−dipole forces. The solvent-induced shift is represented as a sum of the differential solute−solvent internal energy and the differential energy of binding the solvent molecules in the solute vicinity. The aim of the study is 3−fold:  (i) to clarify and quantify the relative effects of the three types of interactions, (ii) to elicit the magnitude of the effect of specific forces, and (iii) to evaluate the contribution of the differential solvent binding to the spectral shift. For (i), the dye properties directing the weighting are the size and the differences in both polarizability and dipole moment between ground and excited states. Accordingly, the distinctions π* vs E T(30) derive from the different sizes (4.5 vs 6.4 Å), dramatically different polarizability enhancement upon excitation (6 vs 61 Å3), and opposite changes in the dipole moment (+8.2 vs −8.6 D) of the two dyes. As a key result, the importance of dispersion forces to the spectral shift even in highly polar liquids is emphasized. While the contributions of dispersions and inductions are comparable in the π* scale, inductions are clearly overshadowed by dispersions in the E T(30) values. Both effects reinforce each other in π*, producing the well-known red shift. For the E T(30) scale, the effects due to dispersion and dipolar solvation have opposite signs making the red shift for nonpolar solvents switch to the blue for polar solvents. For (ii), there is overall reasonable agreement between theory and experiment for both dyes, as far as the nonpolar and select solvents are concerned, but there are also discrepant solvent classes. Thus, the predicted E T(30) values for protic solvents are uniformly too low, revealing a decrease in H-bonding interactions of the excited state with lowered dipole moment. Further, the calculated π* values of aromatic and chlorinated solvents are throughout too high, and this is explained by an increase in charge-transfer interactions of the more delocalized excited state. For (iii), the differential solvent binding energies have been extracted from experimental thermochromic data. For strongly polar fluids, the solute−solvent component of the shift overshadows that from the solvent binding energy variation. In nonpolar and weakly polar liquids the two parts are comparable for 4-nitroanisole, but the latter is still small for betaine-30. Experimental and calculated values in the present work parameters for betaine-30 are applied to calculating solvent reorganization energies λs of intramolecular electron transfer. λs is separated into polar activation by the solvent permanent dipoles and nonpolar activation due to induction and dispersion forces. Experimental reorganization energies due to the classical solvent and solute modes ...

The synthesis and catalytic reactivity of a variety of new ruthenium complexes of the tris(pyrazolyl)borate ligand (HB(pz) 3 ) are reported in this paper. From the parent complex Ru(HB(pz) 3 )(COD)X (X ) Cl, Br) the cationic derivatives [Ru(HB(pz) 3 )(COD)L] + (L ) H 2 O, CH 3 CN, pyridine, dmso) have been obtained by treatment with 1 equiv of AgCF 3 SO 3 in CH 2 -Cl 2 solutions of L. Displacement of COD from these latter complexes has been accomplished in boiling dmf solutions of ligands L 2 ) Ph 2 PCH 2 PPh 2 (dppm), Ph 2 PCH 2 CH 2 NMe 2 (pn), and Me 2 NCH 2 CH 2 NMe 2 (tmeda) as well as L ) pyridine and 3-methylpyridine to give Ru(HB-(pz) 3 )(L 2 )Cl and Ru(HB(pz) 3 )(L) 2 Cl, respectively, each in high yield. From some of these complexes, in turn, the chloride ion has been abstracted with either AgCF 3 SO 3 , TlCF 3 SO 3 , or NaBPh 4 in CH 3 CN as the solvent. In this way we obtained [Ru(HB(pz) 3 )(dppm)(CH 3 -CN)]CF 3 SO 3 , [Ru(HB(pz) 3 )(pn)(CH 3 CN)]BPh 4 , and [Ru(HB(pz) 3 )(tmeda)(CH 3 CN)]BPh 4 . Selected X-ray structures are included. Some of the complexes synthesized are efficient catalysts for the formation of selectively C-O-coupled products from the reaction of phenylacetylene with either benzoic acid or allyl alcohols.