Showing papers by "James Alexis Platts published in 1997"
TL;DR: In this article, the removal of a fluorine atom from its central position in a cubic-like Li14F13+ cluster creates an F−center vacancy that may or may not be occupied by the remaining odd electron.
Abstract: The removal of a fluorine atom from its central position in a cubiclike Li14F13+ cluster creates an F‐center vacancy that may or may not be occupied by the remaining odd electron. The topology exhibited by the electron density in Li14F12+, the F‐center cluster, enables one to make a clear distinction between the two possible forms that the odd electron can assume. If it possesses a separate identity, then a local maximum in the electron density will be found within the vacancy and the F‐center will behave quantum mechanically as an open system, bounded by a surface of local zero flux in the gradient vector field of the electron density. If, however, the density of the odd electron is primarily delocalized onto the neighboring ions, then a cage critical point, a local minimum in the density, will be found at the center of the vacancy. Without an associated local maximum, the vacancy has no boundary and is undefined. Self‐consistent field (SCF) calculations with geometry optimization of the Li14F13+ cluster...
47 citations
TL;DR: In this article, the effects of methyl and phenyl substituents on the ylidic carbon are investigated: methyl substitution enhances basicity slightly, but phenyl substitution decreases it dramatically.
Abstract: Ab initio calculations on nitrogen and phosphorous ylides, and their complexes with methane and acetylene, are reported. A hydrogen bond strength of 35 kJ mol–1 is found between H3N–CH2 and acetylene at the MP2/6-311++G(3d,3p) level; even with methane as the proton donor some stabilisation (ca. 5 kJ mol–1) is predicted. Complexes of H3P–CH2 are found to be rather less stable (19 kJ mol–1 with acetylene). Topological analysis of the charge density indicates a fundamental difference in the bonding between H3N–CH2 and H3P–CH2, with significant double bond character only in the latter. Atoms in molecules decomposition identifies the source of the hydrogen bond strength to be stabilisation of C in the N ylides and stabilisation of P in the P ylides. The effects of methyl and phenyl substituents on the ylidic carbon are investigated: methyl substitution enhances basicity slightly, but phenyl substitution decreases it dramatically. There is some suggestion that this may be a steric as well as an electronic effect.
26 citations