B 1s binding energies in MBPh4, where M is Na, K, Rb, Cs, and NH4

The results of an x-ray photoelectron spectroscopy study of the B 1s binding energy (BE) shift in a series of tetraphenylborates, MBPh4, where M is Na, K, Rb, Cs, and NH4+, which are isostructural are presented. The data are recorded in terms of the relative shift of C 1s and B 1s and average values according to the relationship Δ = BE/sub C 1s/-BE/sub B 1s/, and generally the value of Δ was found to decrease as cation size increases. Values for cation size and electronegativity are also tabulated and show a reasonable correlation with Δ, suggesting a decrease in anion-cation charge transfer as cation size is increased. 1 table