Synthesis of Cyclophanic Chromium(0) Bis(carbene) Complexes

Double Michael addition of 1,4- and 1,3-xylylene diamines and 1,5-diaminobutane to the bimetallic α,β-unsaturated alkoxychromium(0) carbene complex 4 produces in good to excellent yields the corresponding cyclophane bimetallic complexes 5−7 as single isomers. In contrast, the reaction with 1,4-diaminobutane produces a different cyclophane complex, 8, derived from a 1,2- + 1,4-addition process.