Group II Organometallic Compounds

Carbon-13 shifts of Grignard reagents (Table 4.73) [479]) in ether solutions provide evidence that the Schlenck equilibrium is shifted in favor of the dialkylmagnesium compound There is practically no shift difference between dibenzylmagnesium and benzyl-magnesium chloride. 

The equilibrium favors the alkylmagnesium halide, however, upon addition of hexa-methylphosphoramide, as monitored by a deshielding of the benzylic carbon and shield-ings of benzenoid C-l and C-4 in benzylmagnesium chloride [479], 

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Coupling Reactions with Group II Organometallic Compounds... 

Organolithium compounds form a unique class of organometallic compounds with stability, solubility, and activity characteristics intermediate between those of the other Group I and the Group II organometallic compounds. 

Early work identified Group II organometallic compounds such as diethylzinc and ethylmagnesium bromide as coordinate initiators of oxirane polymerization. Under carefully controlled conditions with anhydrous, high-purity monomer, the initiator activity was usually found to be weak. Bailey (80) found that with propylene oxide, distilled and maintained anhydrous with molecular sieves, the rate of polymerization of propylene oxide with dibutylzinc actually decreased as the concentration of dibutylzinc increased. This observation strongly suggested that a trace cocatalyst was needed to effect polymerization. 

G. Salem, C. L. Raston, Preparation and Use of Grignard Reagents and Group II Organometallics in Organic Synthesis, in The Use of Organometallic Compounds in Organic Synthesis (F. R. Hartley, Ed.), Vol. 4, 159, Wiley, Chichester, 1987. 

Electronic Effects in Metallocenes and Certain Related Systems, 10, 79 Electronic Structure of Alkali Metal Adducts of Aromatic Hydrocarbons, 2, 115 Fast Exchange Reactions of Group I, II, and III Organometallic Compounds, 8,167 Fluorocarbon Derivatives of Metals, 1, 143 Heterocyclic Organoboranes, 2, 257... 

A) Ziegler method Catalyst systems can be prepared by reacting a nickel(II) salt with an organometallic compound of the main group metals but aluminum is preferred. 

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