Metathesis route

Potentially, phosphaalkenes can be precursors to phosphinidenes in the same manner that carbenes can be formed from alkenes. This latter metathesis route deserves more attention in light of the recognition that stable carbenes can be in equilibrium with their dimers [11]. However, a discussion on phosphaalkenes is outside the scope of the present survey. 

The chemistry of lanthanide nitridoborates was developed by the more flexible and more efficient solid-state metathesis route by using nitridoborate salts and a lanthanide trichloride, at reaction temperatures as low as 600 °C. This type of reaction has been previously established and studied in some detail for reactions, such as the synthesis of lanthanide nitrides (LnN). Following this concept, lanthanum nitridoborates are obtained from reactions of lanthanum trichloride and lithium nitridoborate (or calcium nitridoborate), performed in a salt-balanced manner with respect to the formation of the co-produced liCl ... 

Dyson et al. also showed that it is important to account for the chloride concentration in the ionic liquid [87]. These authors proved that chloride impurities, resulting from the synthesis of the ionic liquid, have a strong influence on hydrogenation activity. This was demonstrated by a comparison of hydrogenation activity in [BMIM][BF4] which was made via the classical ion-exchange reaction (metathesis route, Scheme 41.2 (1)), with a chloride concentration of 0.2 mol kg-1, and the same ionic liquid which was made by direct conversion of... 

Scheme 41.2 Metathesis route and direct alkylation route for the synthesis of [BMIM][BF4].

Fiirstner A, Muller T (1998) Metathesis Route to Resin Glycosides Formal Total Synthesis of Tricolorin A. J Org Chem 63 424... 

The metathesis route opens up new opportunities for the synthesis of new copolymers by copolymerizing 6,7-dihydro-2(3//)-oxepinone with other cyclic olefins such as norbomene, even though this approach has barely been exploited until now [121]. 

Both the melting point and viscosity of an ionic liquid are highly dependent on their purity and values in the literature differ accordingly. In the 1-alkyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ionic liquids, which are the ones most widely used in catalysis thus far, halide impurities are usually present to varying degrees, due to the metathesis route commonly used for their preparation (see Section 2.3). The effect of different chloride concentrations present on the viscosity of [C4Ciim][BF4] is shown in Figure 2.5.1161... 

Other insect pheromones have been prepared by the co-author (3) using similar cross metathesis routes as illustrated in Eqs 1 and 2. Descriptions of other insect pheromones are provided (4). 

Liquid crystalline polymers (LCPs) have gained attraction as materials with interesting optical, mechanical and rheological properties [3-7]. This review summarizes research on thermotropic liquid crystalhne polymers synthesized by metathesis routes, as this chemistry has proven to be a versatile way to build up well-defined polymer architectures [8]. Recent results promise to ejq)and the possible uses of these methods. 

Metathesis routes have been used to prepare terminal amido, phosphide, and thiolato complexes (equations 8 10) from Cp 2AnCl2 starting materials. For the bulky bis(trimethylsilyl)phosphido ligand, only mono substitution occurs. 

Jordan and coworkers have recently prepared several ansa-bis(indenyl) compounds (AlMe2L)indenyl 2SiMe2 and 1,2- (AlMe2L)indenyl 2C2H4 (L = THE, Et20, 1,4-dioxane) by a salt metathesis route. These were reacted with M(NMc2)4 (M = Zr, Hf) to eliminate [Me2AlNMc2]2 and form ansa-metallocene complexes of bis(dimethylamido)zirconium and bis(dimethylamido)hafmum. A simple tris(indenyl)aluminum compound has been prepared by reaction of bis(indenyl)mer-cury with aluminum metal. ... 

More recently Zintl phases have been used to prepare novel semiconducting phases such as nanocrystals. Group IV nanoparticles have been prepared either by metathesis route or an oxidation of a binary Zintl phase. 

Another novel ligand system which has recently been applied to ytterbium(II) systems is the P-diketiminato ligand [10]. In addition to the formation of compounds via the metathesis route, the insertion of a nitrile into a metal-(aza-allyl) bond can also lead to the formation of p-diketiminato compounds. Although no structural data is available, at present, this p diketiminato ligand has a remarkable effect upon the Yb chemical shift. 

Salt metathesis routes have also been used to prepare cyclopentadienyl-amido diene complexes. Treatment of 27 with Mg(butadiene) affords a 5 95 mixture of the prone and supine isomers of (77s 7]1-CsMe4SiMe2NR)Ti(7]4-CH2=CHCH=CH2) (35, prone 36, supine Scheme 6), respectively.25 Crystallographic characterization of 36 produced metrical parameters consistent with a it2, rf butadiene, contrasting the zirconium congener where more a2, it character is observed. 

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