Magnesium, organic derivatives

These compounds are obtained by action of halogenated organic derivatives on lead alloys (magnesium or alkaline metal alloys). 

Many other cyclic and noncyclic organic carriers with remarkable ion selectivities have been used successfiilly as active hosts of various liquid membrane electrodes. These include the 14-crown-4-ether for lithium (30) 16-crown-5 derivatives for sodium bis-benzo-18-crown-6 ether for cesium the ionophore ETH 1001 [(R,R)-AA -bisd l-ethoxycarbonyl)undecyl-A,yVl-4,5-tctramcthyl-3,6-dioxaoctancdiamide] for calcium the natural macrocyclics nonactin and monensin for ammonia and sodium (31), respectively the ionophore ETH 1117 for magnesium calixarene derivatives for sodium (32) and macrocyclic thioethers for mercury and silver (33). 

Metals more electronegative than magnesium, like beryllium, zinc, cadmium and mercury, form useful reagents for specific purposes, but the metals themselves are not sufficiently active to form organic derivatives under normal laboratory conditions and are unwanted in the environment since they are toxic. Aluminum compounds are useful for industrial purposes, but their use in the laboratory is insignificant in comparison with Grignard reagents. 

These reagents are key intermediates in synthesis of cyclopropane derivatives. The structure and stereochemistry of lithium and magnesium cyclopropyl derivatives as well as their extensive use in organic synthesis have been thoroughly reviewed in previous and updated volumes of this series and no attempt will be made to elaborate on their chemistry here. Their extreme importance in the organometallic chemistry of cyclopropanes will be further revealed as this chapter progresses. 

Reactions of tin(IV) halides or organotin halides with organic derivatives of more electropositive metals provide the most important general synthetic routes to carbon-tin bonds (equation 6). The most frequently used R -M compounds are those of magnesium and lithium, with sodium, zinc, and aluminum having a more limited use. Some examples of these reactions are given in equations (7-9). 

Metathesis reactions are common in the preparation of organic derivatives of elements, using organo-lithium or -magnesium (Grignard) reagents produced by direct synthesis ... 

Various phosphates are produced from phosphoric acid which is made either by adding sulphuric acid to phosphate rock (wet process) or by burning phosphorus in air to give phosphorus pentoxide, which is then hydrated. Major uses of phosphoric acid are the production of phosphate and compound fertilizers, formation of sodium tripolyphosphate (which is used as a builder in detergents where it forms stable water-soluble complexes with calcium and magnesium ions) and the production of organic derivatives like triphenyl and tricresyl phosphate. These are used as plasticizers for synthetic polymers and plastics. 

Syntheses of RM(CO)5 compounds by reaction of [M(CO)5] with halides or by decarbonylation of acyl derivatives have been described. A third synthesis involves treatment of the pentacarbonyl halides M(CO)5X with an organic derivative of lithium or magnesium. Examples of this reaction include the treatment of Mn(CO)5Br with benzylmagnesium chloride to give the benzyl derivative C6H5CH2Mn(CO)5 93) and the reaction of Mn(CO)sBr with phenyllithium to give the phenyl derivative CsHsMn (CO)5 156). Disadvantages of reactions of this type include the formation of much Mn2(CO)io as a by-product and a low yield of the desired product. 

The organic derivatives of lithium and magnesium are the most important of the group I and II organometallics. The metals in these two groups are the most electropositive of the elements. The polarity of the metal-carbon bond is such as to place high electron density on carbon. This electronic distribution is responsible for the strong nucleophilicity and basicity that characterize these compounds. As... 

Magnesium and beryllium form organic derivatives which are essentially covalent in structure and highly reactive, the M—C bonds being strongly polarized they resemble organolithium compounds in several respects. 

The first metal-ate complex, sodium triethylzincate, " was obtained by John Wanklyn who treated diethylzinc with elemental sodium in an attempt to produce ethylsodium. A systematic and reliable approach to ate complexes is the addition of a more polar organometallic reagent (eg., an organolithium) to a less polar organic derivative of an alkali-earth metal, transition element, or metalloid. In this way, a wealth of ate complexes of berrylium, magnesium, zinc, copper, boron, aluminum, silicon, tin, and mercury as well as of nonmetals like phosphorus, sulfur, selenium, tellurium, and even iodine " have been obtained. 

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