Russell S. Drago

On the electronegativities of the group IV elements

Abstract Reported values for the electronegativities of the Group IV elements are critically reviewed and it is concluded that the electronegativities of Si, Ge, Sn and Pb are essentially constant or decrease slightly. It is further concluded that in contrast to a previous suggestion, the electronegativity differences have essentially no effect upon the chemistry of these elements, and cannot be correlated with either the nuclear quadrupole coupling of the tetrahalides or the chemical shift of the alkyl derivatives.

Donor and acceptor properties of some trisubstituted oxy compounds of the group IV elements

The donor and acceptor properties of the compounds R3MOC6H5 (where R = CH3 or C2H5 and M = C, Si, Ge, Sn and Pb) and C6H5)3MOH were investigated in detail. The results cannot be correlated with the “new” electronegativity scale proposed for the Group IV elements. Changes in the extent of π-bonding between the central element and oxygen are proposed as the dominant effect giving rise to the observed trends. Contrary to previous reports no hydrogen bonding interaction could be detected between (C6H5)3SnOH or (C6H5)3PbOH and (C2H5)2O. The donors (C2H5)2O. (CH3)2SO and HC(O)N(CH3)2 were all investigated in this study. In every instance a reversible dehydration reaction occurred. The infrared spectra of these systems is discussed. It was found that the compounds R3MOH (where R is CH3 or C2H5 and M is tin or lead) could be titrated with phenol in the presence of molecular sieves. This procedure may be of value in the synthesis of group IV compounds which are sensitive to light and heat.

Solvates of some methyllead compounds and their 207PbCH3 coupling constants

Abstract Some solvates of the trimethyllead(IV) cation and dimethyllead(IV) cation have been prepared and their structures investigated by infrared and nuclear magnetic resonance spectroscopy. Solvates have been isolated with one or two solvent molecules coordinated to trimethyllead(IV) cation and two or four solvent molecules coordinated to dimethyllead(IV) cation. The effect of solvent on J ( 207 Pb–CH 2 ) in the trimethyllead cation has been found to be similar to the effect of solvent on J (Tl–CH 3 ) in the dimethylthallium(III) cation.

Normal Coordinate Analysis of PF5, PF2Cl3, and PCl5

Normal coordinate analyses have been performed for the series of phosphorus (V) halides—PF5, PF2Cl3, PCl5. The effect of including interaction force constants has been studied in detail. The bond‐stretching force constants have been interpreted in connection with molecular orbital calculations for these molecules.

Erratum: Semiempirical Calculations of Some 2H and 14N Nuclear Quadrupole Coupling Constants

A parameterized LCAO method for the calculation of nuclear field gradients is described. The principal difference between this and other theories concerns the treatment of the two‐center contribution to the field gradient. In our method, the two‐center terms are included as parameters proportional to their respective nuclear terms. Only three parameters are necessary, one for triple and double bonds, one for single bonds, and one for a bond to hydrogen. The method developed herein not only successfully reproduces 14N field gradients, but also 2H field gradients, heretofore not possible with other semiempirical methods.

Use of a relationship between J(13CH) and τ to evaluate anisotropic contributions to τ-anisotropies in the τ-values of the group IV tetramethyl derivatives

A linear relationship is reported between 13Cue5f8H spin-spin coupling constants, J(13Cue5f8H), and proton chemical shifts, τ, for a restricted series of methyl derivatives. The existence of this relationship is rationalized and the relationship is employed: (a) to justify an earlier interpretation of the chemical shift data for the tetramethyl derivatives of the group IV elements; (b) to conclude that the chemical shift data cannot be employed to evaluate electronegativities of the central group IV element in these compounds; (c) to aid in evaluating the anisotropic contributions to the chemical shifts of the methyl halides and other compounds. The 13Cue5f8H spin-spin coupling constants indicate that the hybridization of the methyl carbon atom in the tetramethyl derivatives of the group IV elements changes with the effectiveness of central element-carbon overlap.

Preparation and properties of some alkane-soluble liquid transition metal complexes

Abstract A series of nickel(II) compounds have been prepared which are derivatives of reported β-diketonates, N,N-dithiocarbamates, or O,O′-dithiophosphates. The transition metal ton complexes reported here are unusual in that they are liquids or low melting waxes that are very soluble in hydrocarbon solvents such at pentane and squalane. Because of their properties, techniques used for the isolation and subsequent purifftcation of the complexes are different than those employed for the lighter homologues. The ligand substituents profoundly affect the propertim of the compounds. In contrast to the reported complexes, the ntckel(II) bis-β-diketonates prepared in this study undergo the monomer-trimer transition close to room temperature. For example, in the compound in which the methyl groups of nickel(II) acetylacetone are replaced by n-heptyl groups, the transition from diamagnetic purple solid monomer to paramagnetic green liquid trimer occurs at about 17°C. It occurs at 42°C for the n-nonyl derivative. The t-nonyl (1,1-dimethylheptyl) derivative melts at +2°C since the bulky groups adjacent to the carbonyls prevent trimer formation and hinder crystallization.

Coordination and Activation of Dioxygen

Abstract Investigations of cobalt dioxygen adducts have lead to a simple, unified description of these complexes. Extension of this description to other metal dioxygen adducts gives insight into the function of biological and catalytic systems. Taking advantage of the high oxidizing power of O2 in a controlled and selective manner is an important goal of chemists. Knowledge of the perturbation made on O2 by coordination to metals is essential to understanding ways to activate it.

A spectrophotometric investigation of iron(III) chlorine in pyridine

Abstract The incorporation of the solvent pyridine into the Coordination Model for non-aqueous solvents is most illuminating with regards to the importance of non-specific solvation. This is a strongly coordinating solvent with poor solvating properties. The species formed when FeCl 3 is dissolved in pyridine have been investigated in both dilute and concentrated solutions over a mole ratio range of 0 to 10 moles of chloride per mole of iron(III). It has been shown that the three species formed which can be detected by ultraviolet-visible spectroscopy and molar conductance techniques are FeCl 4 − , (FeCl 3 .nC 5 H 5 N) and a metastable species of low Cl − /Fe III ratio.

Spin‐Forbidden Transition of NO Observed in Solution Spectra

Abstract : The transition occurs at 3.5 ev in the UV spectra of NO dissolved in organic solvents. The observed vibrational frequencies range from 1/1100 cm in CCl4 to 1/1600 cm in CH3OH. These trends are correlated to the shift of electron density out of the Pi antibondin level upon formation of hydrogen bonds with the solvent. Investigations of the absorption spectrum of nitric oxide in polar solvents led to the discovery of a band with well resolved vibrational fine structure commencing at 3850A and extending to shorter wavelengths. This band is not observed in the gaseous spectra. The band was analyzed by assuming that it is due to a spinforbidden transition at about 4.5 ev above the ground state. (Author)