Tertiary diamine complexes

Work with TED (triethylenedimaine) showed that reasonable metalation rates were obtained only at ratios of 1 1 in benzene. The reaction required 2.5 hours in refluxing benzene for completion. The bright yellow, crystalline product had a modest solubility in benzene and precipitated from solution. The solid complex may be pyrophoric in large amounts. The solubilities of various organolithium-tertiary diamine complexes are listed in Table II. 

Table II. Solubility of Organolithium—Tertiary Diamine Complexes...

Langer (13) has also disclosed the use of alkyllithium and dialkyl-magnesium tertiary diamine complexes as catalysts for copolymerization of ethylene and other monomers such as butadiene, styrene, and acrylonitrile to form block polymers. Examples are given in which polybuta-dienyllithium initiates a polyethylene block, as well as vice-versa. Random copolymers of these two were also prepared, and other investigators have used not only tertiary diamines but hexamethylphosphoramide (14) and tetramethylurea (15) as nitrogenous base cocatalysts in such polymerizations. Antkowiak and co-workers (11) showed the similarity of action of diglyme and TMEDA in copolymerizations of styrene and... 

Crassous et al.177) studied the polymerization of ethylene using n-butyllithium in conjunction with the tertiary diamines TMEDA, TEEDA (tetraethylethylenedi-amine) and PMDT (pentamethyldiethylenetriamine). In contrast to the situation with TMEDA the rate of polymerization was found to show a first order dependence upon the complexed chain end concentration. Steric hindrance seems to prevent the dimerization of the chain ends. Examination of the n-BuLi. TEEDA complex by -NMR shows that the displacement to high field of the protons a to the lithium induced by complexation is much smaller with TEEDA than with TMEDA or PMDT. With [TEEDA] < [RLi] time-averaged signals were obtained showing that the exchange process... 

Synthetic Aspects of Tertiary Diamine Organolithium Complexes... 

The results reported here describe an investigation of the optimum conditions of preparation of the tertiary diamine phenyllithium, benzyl-lithium, allyllithium, and lithiated TMEDA complexes. These reagents were allowed to react with some common reagents to help delineate the synthetic usefulness of the complexes. 

Reactivity of Various Tertiary Diamines in the Preparation of Tertiary Diamine Organolithium Complexes by Metalation. Previous work has shown that the reactivity and the rate of metalation for Reaction 2 of the tertiary diamine organolithium complexes is a function of the tertiary diamine in the complex (1,9). In the specific case of the metala-... 

It might be expected that in the presence of TMEDA or other tertiary diamines anomalous reaction products might be obtained with organolithium compounds such as benzyllithium. A number of reports in the literature disclose instances of the expected reaction products from reactions such as carbonation to the carboxylic acid and addition to benzophenone (I, 3, 4, 12). The phenyllithium-TMEDA (1 1) complex in benzene was allowed to react with benzophenone to give a 95% yield of triphenylcarbinol and with cyclohexanone to yield 59% of the 1-phenylcyclohexanol. The reaction with excess trimethylsilyl chloride is apparently quantitative. The main consideration in using these complexes is to use low temperatures for reaction and aqueous washes of ammonium chloride solution in the work-up to remove all of the tertiary diamine (the odor can be detected in low concentrations.)... 

The crystalline yellow 1 1 benzyllithium-TMEDA complex has a lower solubility in toluene than does the (benzyllithium )2-TMEDA complex which tends to form oils. Because of its higher solubility and to eliminate as much of the tertiary diamine as possible, the 2 1 complex was used for synthetic evaluations. It is probably the optimum ratio to use in this benzyllithium system. Solutions of up to 38 wt % benzyl-lithium in toluene or about 59 wt % of the (benzyllithium )2-TMEDA complex have been prepared. At ratios of 4 1 or more in toluene, a dark-red tar or oil also separated from the solution. With hexane as the solvent, yellow crystals of the 1 1 benzyllithium-TMEDA complex precipitated at a ratio of 2 1 or more, a dark-red oil separated instead. 

The solutions of (benzyllithium )2-TMEDA were much more convenient to use than the solid, relatively insoluble benzyllithium-TED complex. The reaction yields vary between these two complexes. Whether this is a function of the different solvent systems used for each, lack of optimization, or the actual tertiary diamine present was not examined, however. 

Although alkyllithiums are used mainly in these N-chelated complexes, other alkali metal alkyls may also be used. For example, organo-sodium reagents have been solubilized in hydrocarbon solvents by chelating tertiary diamines and used as polymerization catalysts by workers at Borg-Wamer Corp. (22),... 

The reactivity of the organolithium compounds is increased by adding molecules capable of solvating the lithium cations. Tetramethylenediamine (TMEDA) is commonly used for organolithium reagents. This tertiary diamine can chelate lithium. The resulting complexes generally are able to effect deprotonation at accelerated rates.In the case of phenyllithium, NMR studies show that the compound is tetrameric in 1 2 ether-cyclohexane, but dimeric in 1 9 TMEDA-cyclohexane. ... 

This study constitutes a further example of how efficient catalytic reactions can be developed despite the presence of complex solution equilibria. Originally, this chemistry was developed in a non-donor solvent rather than using an excess of donor as solvent. By so doing, the critical effects of additives, both chiral and achiral, are more readily appreciated. Indeed, incorporation of lithium bromide and an achiral, bidentate ligand in addition to 5 are essential for selectivity. The effects of these additives are particularly interesting. Tertiary diamines, e.g. 6 and its analogues,... 

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