exo- and endo-tricarbonyl[(4b,5,6,7,8,8a-eta)-cis-N-methyl-2,3,4,4a,9,9a-hexahydro-1H-carbazole]chromium(0)

Acid-mediated hydride reduction of tricarbonyl(eta(6)-N-methyl-1,2,3,4-tetr ahydrocarbazole)chromium(0) affords either the cis-fused exo-hexahydrocarba zole-chromium(0) complex {[Cr(C13H17N)(Co)(3)], (I)} exclusively, or a sepa rable mixture of (I) and the endois-omer {[Cr(C13H17N)(CO)(3)], (II)}, depe nding upon the choice of hydride donor. The conformations of the hexahydroc arbazole systems differ in the orientation of the indoline moiety with resp ect to the saturated hexahydrocarbazole rings. The isolation of the exo-iso mer is unusual, as this complex arises via reaction at the sterically more hindered endo face of the coordinated ligand.