A new R-0 value for Na-O bonds of 1.756(42) Angstrom was determined from 30
1 NaOn complexes. The bend valence sum analysis suggests a covalent interac
tion of the Na+ ion with aromatic rings and/or organic anions. The BVS anal
ysis of Na(15-crown-5)(+) cation complexes requires additional bonding inte
ractions which can be used to explain the enhanced stability of the cation
complex both in solution and in the solid state relative to that in the gas
phase.