| Research Abstract |
Polymerization of 3,6-di (p-tolyl) -1,2-diisocyanobenzene was induced by trans-methyl-palladium (II) bromide bis (dimethylphenylphosphine) complex to give poly [5,8-di (p-tolyl) -2,3-quinoxaline] s, which have helical structures. In an oligomerization of 1,2-diisocyano-3,6-di (p-tolyl) benzene induced by trans-MePdBrP_2^* having chiral phosphine ligands P^*= [ (S)-2-methyl] _2PPh, a diastereomeric pair of [quinque (quinoxaline-2,3-diyl) ] palladium (II) phosphine complexes thus prepared have been separated to the corresponding (M,S) -and (P,S) -complexes having two chiral elements, one based on the helicity of the backbone of quinque (quinoxaline-2,3-diyl) and the other of the phosphine ligands. Both diastereomerically pure palladium (II) complexes, (M,S) -and (P,S) -complexes, induced a screw-sense selective polymerization of 3,6-di (p-tolyl) -1,2-diisocyanobenzene with the extension of the helical conformation of the starting palladium (II) complexes. Optically active 2'-methoxy-1,1'-binaphtyl-2-palladium (II) -iodide bis (dimethylphenylphosphine) complex, which was been prepared by the reaction of 2'-methoxy-1,1'-binaphtyl-2-iodide with palladium (0) tris (dimethylphenylphosphine) complex, induced the polymerization of 3,6-di (p-tolyl) -1,2-diisocyanobenzene in good yield, but in low stereoselectivity. In contrast, a screw sense selective polymerization of 3,6-di (p-tolyl) -1,2-diisocyanobenzene was achieved by optically active 1,1'-binaphtyl-2-palladium (II) iodide bis (dimethylphenylphosphine) complex catalyst.
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