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A study of square planar palladium(II) and platinum(II) carbonyl derivatives, the molecular structure of cis-Pt(CO)(sub 2)(SO3F)(sub 2), the complete vibrational spectra of cis-Pt(CO)(sub 2)Cl2, and the attempted synthesis of cis-Pt(CO)(sub 2)F2 is presented. The results show the reductive carbonylation of PtF6 in HF produces with [Pt(CO)(Sub 4)][PtF6] the first carbonyl fluoride of platinum, and the reaction of [Pt(CO)(sub 4)][Sb2F11](sub 2) and CsF in HF results in the formation of an anionic cluster complex Cs2[Pt3(CO)(sub 6)](sub n=10).

Research has been conducted on the bis(mu-chloro)tetracarbonyldirhodium(I) and chlorotricarbonyliridium(I). The reactions of these compounds in conjugate Bronsted-Lewis superacid and in CO atmosphere are described.

Nuclear magnetic resonance spectroscopic analysis of methyltitanium trichloride compounds showed that the central carbon atom exhibits a deshielding trend. The analysis of C-CH3, C-Cl, Si-Ch3 and Si-Cl bonds showed the expected trends in polarization and sp(super n) hybridization. The Ti-Ch3 and Ti-Cl bonds are found to be essentially Sd(super 3) hybridized.

Quantum mechanical calculations help determine the geometries and bond energies of Lewis acid-base complexes of BH3, BF3, BCl3, AlCl3 and SO2. The results agree with the experimental gas phase values. Electronic structure analysis using the natural bond orbital partitioning method shows the absence of correlation between charge transfer and bond strength. Examination of electron density distribution by topological analysis shows that strongly bound boron complexes have high covalent contributions to the donor-acceptor bonds, while weakly bound boron complexes exhibit electrostatic interactions between the Lewis acid and base. AlCl3 and SO2 complexes have significant electrostatic interactions between donor-acceptor bonds.

Density functional methods were used to compute the symmetry force fields for neutral and ionic transition metal carbonyl complexes. The variations in the CO-CO coupling, C-O stretching and M-C-O bending force constants clearly indicated that pi back-donation disappears when the total charge increases and the electrostatic effects become dominant in the highly charged cations. Results also showed that the empirical Cotton-Kraihanzel method can effectively calculate trends in the C-O stretching force constants but not the CO-CO interaction constants.

An extensive theoretical and experimental study of the Jahn-Teller distortion in V (CO)6 is discussed. The spectra showed a pronounced temperature dependence, especially for the Jahn-Teller active models, E(sub g) and T(sub 2g).

Continuum solvation models have proven to yield very valuable information about solvation effects, if cavities close to the van der Waals surface of the solutes are used for the calculation of the screening charges. Unfortunately, such cavity size implies that a small but significant portion of the solute electron density reaches out of the cavity. This outlying charge causes serious problems in the context of the dielectric continuum treatment of the solvent. The present paper presents a critical consideration of the origin, the magnitude, and the different strategies for treatment of this problem. Finally, a novel ansatz using an additional, outer cavity is presented which provides rather accurate correction of the corresponding error. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The geometries of the title compounds have been optimized at the levels of restricted Hartree–Fock (RHF) theory, second-order Mo\ller–Plesset perturbation theory, and gradient-corrected density functional theory (DFT) using all-electron and effective core potential wave functions in conjunction with polarized double- and triple-zeta basis sets. The harmonic force fields have been determined from RHF and DFT calculations. The DFT results are generally in very good agreement with the available experimental data. The computed frequencies are accurate enough to be of predictive value, especially when correcting for small systematic errors. Several new assignments of bands in the observed vibrational spectra are proposed. Infrared intensities, dipole moments, and charge distributions are also discussed. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The harmonic force fields of the title compounds have been calculated at the level of Hartree–Fock (HF) theory, Mo\ller–Plesset second-order perturbation theory (MP2), and gradient-corrected density functional theory (DFT) using all-electron and effective core potential wave functions in conjunction with polarized double- and triple-zeta basis sets. The DFT results are in very good agreement with the available experimental data, whereas the HF results are inadequate and the MP2 results are satisfactory only for the 5d and (partly) the 4d transition metal complexes, but not for the 3d transition metal complexes. The calculated DFT frequencies are accurate enough to suggest reassignments in the vibrational spectrum of Fe(CO)5. In the case of Ru(CO)5, Os(CO)5, Pd(CO)4, and Pt(CO)4 where experimental data are scarce, the DFT predictions may guide future experimental work. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A structural, synthetic, spectroscopic and computational investigation of [M(CO)4][Sb2F11]2, M = Pd, Pt, is presented. The square planar [M(CO)4]2+ cations are found to be a vital element of a series of thermally stable, superelectrophilic metal carbonyl cations.

Three-dimensional quantum scattering calculations have been carried out for the electronically nonadiabatic Br([sup 2]P[sub 1/2])+H[sub 2]→HBr+H reaction. The calculations have been done using two methods: the time-independent hyperspherical close-coupling formalism for the total angular momentum quantum number J=0 and the generalized R-matrix propagation method with negative-imaginary potentials which absorb the reactive flux for J>=0, but employing the coupled-states approximation for J>0. The (2x2) diabatic model, which was originally developed by Truhlar and co-workers, has been employed in the present calculations. The results calculated with the two methods agree very well with those obtained by Truhlar and co-workers, indicating that our results are numerically converged. Detailed analyses of the calculated probabilities show that the electronically nonadiabatic transitions from Br([sup 2]P[sub 1/2])+H[sub 2](ν) to Br([sup 2]P[sub 3/2])+H[sub 2](ν+1) effectively occur in the entrance region of the potential surface but that the contribution of the electronically nonadiabatic chemical reaction, Br([sup 2]P[sub 1/2])+H[sub 2](ν)→HBr+H, is small. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]