Abstract The existence of a linear relationship the form Y=a x1+b x2+c between the charge density - calculated by semiempirical SCF -LCAO -MO-methods - and the 13C -chemical shifts of mesoionic compounds has been shown. An influence of substituents in pyridinium betaines on the chemical shift is not observable.
A linear relationship is found to exist between the carbonyl stretching frequency ( vC=O) and the carbon-13 chemical shift data [δ(13C=O)] for the carbonyl group of 0.345 mole % acetone in a mixed solvent solution ranging from 1.5 to 70.8 mole % CHCl3/CCl4. The correlation shows that as vC=O decreases in frequency δ(13C=O) increases in frequency as the concentration of CHCl3 increases in the acetone/CHCl3/CCl4 solutions. However, the relationship between vC=O and the mole % CHCl3/CCl4 and between δ(13C=O) and the mole % CHCl3/CCl4 is not linear over the concentration range studied. Both hydrogen bonding and bulk dielectric effects most likely contribute to the change in both the IR and NMR data with change in the CHCl3/CCl4 ratio.
Carbon spectra of a range
of 2- and 4-substituted benzhydryl cations have been measured in super acid at
variable (low) temperatures. In the 4-substituted benzhydryl cations the
chemical shift of the para carbon in the unsubstituted ring [δ(C4?)]
proves to be an excellent probe for changes in charge density at the cationic
carbon, as shown by its correlation with σp+ (r
0.990). Measurement of δ(C4?) for the 2- substituted benzhydryl cations
provides a direct measure of σ0+ for side-chain benzene
derivatives; these values are OMe -0.59, Me -0.10, F
0.19, Cl 0.26, Br 0.29 and CF3 0.69.
Chloride abstraction, using AgPF6, from tri(1- cyclohepta-2,4,6-trienyl)phosphane platinum and palladium dichloride, [P]MCl2 [M = Pt (1), Pd (2)], affords the complexes {[P]MCl}PF6 [M = Pt (3), Pd (4)] in good yields. The central metal is coordinated by the chloro ligand, the phosphorus atom and by three η2-C=C units, one of each C7H7 ring. This assignment of a highly symmetrical C3v structure is based on a consistent set of NMR data (1H, 13C, 31P, 195Pt NMR), in agreement with NMR data of the corresponding known neutral iridium and rhodium complexes [P]MCl [M = Ir (5), Rh (6)]. The chemical shift δ103Rh of 6 was determined, and a nearly linear relationship δ195Pt / δ103Rh was established.
RECOVERY OF THE CHARGE DENSITY LINEAR CONDUCTOR ON KNOWN POTENTIAL DISTRIBUTION