Metal metathesis

The production of CPO is based on relatively inexpensive cycHc substances these must be derivatized, however, to meet the requirements of resistance to heat softening and suitabiUty for metallization. Metathesis polymerization is problem-prone, since relatively large amounts of catalyst (WCl, C2H AlCl2) must be removed by solvent extraction (216). In the process, the price of CPO, at small batches, is several times higher than that of BPA-PC. 

That was in fact for zirconium alkoxides that Bradley developed all the major synthetic approaches to the alkoxides ofhigh-valent metals—metathesis of ZrCl4or (more preferably [PyH]2ZrCl6)with ammonia [201] (method 5), alcoholysis of Zr(NR2)4 [1579] (method 4), alcohol interchange reactions... 

Divalent lanthanide chemistry has been dominated by the most readily accessible divalent lanthanide metals samarium(II), europium(II), and ytterbium(II) (classical ) for decades, and a large number of divalent lanthanide compounds have been prepared [92], There are three routes to generate divalent organolanthanide complexes oxidative reaction of lanthanide metal, metathesis reaction of a divalent lanthanide halide, and reductive reaction of a trivalent lanthanide complex. 

Scheme 1. Synthesis of Ru a-aUsyne and diyne constructs by alkali metal metathesis.

Figure 2. Early transition metal CT-aUsyne complexes formed via alkali metal metathesis.

Zirconium Reagents. Ethenylation can be effected via hydrozirconated terminal alkynes (Scheme 83). The alkenylzirconocene gives the -aUcenyl product. The reaction is carried out in the presence of zinc chloride. Presumably metal metathesis occurs before the palladium-mediated coupling takes place. The coupling is regiospecific with initial... 

When coordinated to palladium, the rr-indenyl ligand tends to slip from the if - to the 77 -coordination mode, and most of the complexes synthesized show severe distortions or clear -indenyl coordination. Thus, although being a cyclopentadienyl analog, it is rare to find a true Tj -indenyl coordination to palladium, however common for other transition metals. Metathesis with Li[indenide] and ligand-substitution reactions are common preparative routes for indenyl derivatives. The insertion of an alkyne into Pd-G bonds of vinyl substituted aryls, followed by intramolecular alkene insertion, also leads to highly substituted indenyl palladium complexes. Equation (66) shows one of these examples. ... 

Chromium Molybdenum, and Tungsten. Triple metal-metal bonded complexes of the types [MaLe] (M = Mo or W, L = NRj, OR, or R) and [ M(CO)aCp a] have been reviewed. Although MO calculations suggest the structures of the former should be eclipsed, the known examples, which contain bulky terminal ligands, have ethane-like, staggered conformations. Attempts to determine the mechanism by which [MaLg] complexes are formed have, as yet, been unsuccessful although it is clear that metal-metal metathesis reactions between [MOaLe] and [WaLe] occur far less readily than do those between [ Mo(CO)aCp a] and [ W(CO)aCp a]. ... 

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