Lead phosphinates, coordination polymers

It was found that 16 exhibited regiospecific oligomerization of propene, 1-butene, and 1-pentene to yield linear atactic polymers as head-to-tail coupling of monomer units is favored by this catalyst [33]. The polymer chain grows by a P-hydride elimination mechanism, which competes with phosphine coordination, leading to a relatively... 

Infrared data suggests there is loss of tributylphosphine followed by coordination of the Cr(C0)2 moiety to an alkyne unit. The weight loss found in the TGA is consistent with loss of tributylphosphine and the endotherm observed is likely due to evaporation of the free phosphine. A similar process was noted for polymer 1 except this involved loss of carbon monoxide. In essence then, polymers 1 and 5 upon thermal treatment lead to the same highly-crosslinked and thermally stable polymer. 

Intensive studies by Shell on catalyst development for the ethylene/propylene/CO terpolymerization provided the most effective catalyst represented as [Pd(L"L )(S)2][X]2, where L"L (L = or L ) is a cis-chelating bis(phosphine) ligand, S is a solvent molecule, and X is an anion with low coordination capability. Ligand development leads to three patterns of stereoregular polymers those are, isotactic poly(propylene-ALT-CO), syndiotactic, and isotactic poly(styrene-ALT-CO). Noteworthy... 

Coordination centers studied include beryllium, lanthanum, cerium, titanium, zirconium, thorium, uranium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, aluminum, tin, and lead. Many nonmetallic elements have been incorporated into the bridging groups and side groups, so that, in all, some 30 elements have been included in polymers of the phosphinate type. Of most interest are some of the polymers with tetrahedral and octahedral centers. 

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