A series of diastereomeric syn and anti Cr(CO)3 complexes of 1-substituted indanes have been prepared by thermolysis of Cr(CO)6 or by arene exchange with naphthalene-Cr(CO)3 (3). The regioselectivity of nucleophilic addition of a-nitrile carbon nucleophiles to syn and anti 1-R-indane Cr(CO)3 complexes (R = OMe 4, Me 10) has been investigated and compared with that of analogous reactions with indaneCr(CO)3 (1). The results of an X-ray study of syn- and anti-4 are presented. Nucleophilic additions are shown to be sensitive to the steric and electronic effects of the benzylic substituent and the nucleophile. When the reaction mixtures are warmed to 0°C, equilibration of the regioisomeric cyclohexadienyl intermediates takes place.