Titanium 1,4-tetramethylene

The metallocycle 1,4-tetramethylene bis(cyclopentadienyl)titanium-(IV), obtained by reacting CpTiCl2 with Li(CH2)4Li, decomposes at -30°C, yielding a mixture of 1-butene and ethylene (43). The pathway leading to 1-butene may involve a hydride intermediate, although whether this is formed by a- or /3-hydrogen atom elimination is uncertain, e.g.,... 

Finally, Coates and coworkers found that bis(phenoxyimine) titanium complex 31 was also capable of living 1,5-hexadiene polymerization and 1,5-hexadiene/propylene copolymerization (Hustad and Coates, 2002). Homopolymerization of 1,5-hexadiene with 31/MAO at 0°C produced a high molecular weight polymer with a narrow PDI (M = 268 000 g/mol, Mw/Mn = 1.27). The polymer showed the presence of two distinct units - the expected MCP units as well as 3-vinyl tetramethylene (3-VTM) units. As shown in Scheme 9.4, the MCP units are proposed to arise from 1,2-insertion of 1,5-hexadiene followed by a 1,2-cyclization. However, an initial 2,1-insertion of 1,5-hexadiene followed by a 1,2-cyclization forms a... 

We reported previously that the mechanical properties of the amorphous etheric poly[bis(methoxyethoxyethoxy)-phosphazene] (MEEP) were significantly improved by in situ polymerization of tetraethoxysilane (TEOS) (4). This work on etheric phosphazene composites was consistent with reports from the research groups of Mark (5) and Wilkes (6), where metal alkoxides were added to poly(dimethylsiloxane) and poly(tetramethylene oxide). We now extend the phosphazene sol-gel composites to include the more reactive metal alkoxides of titanium, zirconium, and aluminum, and we report that when polymerized in situ, each is compatible with the etheric phosphazene polymer. Dynamic mechanical and stress-strain techniques are utilized to evaluate and compare the mechanical properties of the different composites. Thermal and... 

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