To assess the relative electronic influence of highly substituted aryl isocyanides on transition metal centers, a series of C-4v-symmetric Cr(CNR)(CO)(5) complexes featuring various alkyl, aryl, and m-terphenyl substituents have been prepared. A correlation between carbonyl-ligand C-13{H-1} NMR chemical shift (delta(CO)) and calculated Cotton-Kraihanzel (C-K) force constant (k(CO)) is presented for these complexes to determine the relative changes in isocyanide sigma-donor/pi-acid ratio as a function of substituent identity and pattern. For nonfluorinated aryl isocyanides possessing alkyl or aryl substitution, minimal variation in effective sigma-donor/pi-acid ratio is observed over the series. In addition, aryl isocyanides featuring strongly electron-releasing substituents display an electronic influence that nearly matches that of nonfluorinated alkyl isocyanides. Lower sigma-donor/pi-acid ratios are displayed by polyfluorinated aryl isocyanide ligands. However, the degree of this attenuation relative to nonfluorinated aryl isocyanides is not substantial and significantly higher sigma-donor/pi-acid ratios than CO are observed in all, cases. Substituent patterns for polyfluorinated aryl isocyanides are identified that give,rise to low relative sigma-donor/pi--acid ratios but offer synthetic convenience for Coordination chemistry applications. In order to expand the range of available substitution patterns for comparison, the syntheses of the new m-terphenyl isocyanides CNArTripp2, CNp-MeArMes2, CNp-MeArDArF2, and CNp-FArDArF2 are also reported (Ar-Tripp2 = 2,6-(2,4,6-(i-Pr)(3)C6H2)(2)C6H3); p-MeArMes2 = 2,6-(2,4,6-Me3C6H2)(2)-4-Me-C6H2); p-MeArDArF2 = 2,6-(3,5-(CF3)(2)C6H3)(2)-4-Me-C6H2); p-FArDArF2 = 2,6-(3,5-(CF3)(2)C6H3)(2)-4-F-C6H2).