DABCO donor-acceptor complexes

The long known132 electron donor-acceptor complexes between tertiary amines and carbon tetrahahdes are simple systems. Thus, l,4-diaza[2,2,2]bicyclooctane (DABCO) or quinuclidine afford solid complexes with carbon tetrabromide142. 

X-ray crystal analysis indicates that the DABCO/CBiq complex consists of alternating planes of the diamine and carbon tetrabromide in which each acceptor is bound to two donor units. The quinuclidine/CBr4 complex consists of pairs of donor-acceptor systems in which every quinuclidine molecule is bound to only a single molecule of carbon tetrabromide. 

The ability of the boron atom of 59 to engage in a donor-acceptor interaction was illustrated with DMAP and DABCO (DABCO = diazabi-cyclo-[2.2.2]-octane) that readily formed the corresponding Lewis adducts. Interestingly, a similar behavior was retained after coordination of the phosphorus atom to palladium. The formation of the Lewis base adducts 66a and 66b of complex 65 (Scheme 38) was supported by solid-state 31P and nB CP/MAS-NMR spectroscopy (<5 1 B = 5-6 ppm), although the occurrence of decomposition and/or dissociation processes impeded spectroscopic characterization in solution and recrystallization to obtain X-ray quality crystals. Compounds 66a and 66b substantiate the ability of ambiphilic compounds to engage concomitantly into the coordination of donor and acceptor moieties. Such a dual behavior opens interesting perspectives for the preparation of metallo-polymers and multimetallic complexes. 

The zinc complex of 8c and 8d is treated with a bidentate ligand, DABCO, to form the sandwich dimer complex 9 (Scheme 3.15). Thus-obtained complex 9 is considered to be a unique redox system, which is composed of the electron acceptor moiety surrounded by the donor x-conjugated pendant groups [35]. 

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