Regioselective Complexation of 1,2:9,10-Dibenzo[2.2]paracyclophanedienes

Abstract

1,2:9,10-Dibenzo[2.2]paracyclophane-1,9-diene, 1, and its 4′,5′,4″,5″-tetrakis(p-t-butylphenyl) derivative, 2b, regioselectively from the tricarbonylchromium(0) complexes 3, 5 and 4, 6, respectively, in which the (CO)₃Cr units are attached to the phane arene units. This is manifestation of the increased π-basicities of their bent arene moieties; surprisingly even the second (CO)₃Cr unit prefers the bent arene in spite of the electron withdrawing effect of the first one.