Calcium alkoxides monomeric

Recently (33, 59), soluble monomeric alkoxides (aryloxides) of calcium and barium have been synthesized by the reactions of their iodides with the potassium salts of sterically hindered alcohols (phenols). 

Alkaline-earth alkoxides are insoluble and involatile in contrast to the double alkoxides formed by dissolving the alkaline earth metal in a solution of niobium or tantalum isopropoxide in propan-2-ol. With the exception of the magnesium derivative which decomposes on heating, they can be sublimed in vacuo, thermal stability diminishing in the order Ba > Sr > Ca. The calcium and strontium derivatives are monomeric in refluxing benzene, the others are insoluble. Attempts to elucidate structures by n.m.r. spectroscopy were foiled by the rapid exchange of geminal dimethyl protons (see also p. 66). 

Interest in the synthesis and structural characterisation of less common metalloorganophosphide systems has continued. A range of alkali metal complexes of the phosphide anion (48) has been prepared from the lithio-phosphide by simple metathesis with alkali metal alkoxides. The lithio-phosphide exists as a dimer, but crystallisation of the sodium and potassium drivatives in the presence of TMEDA results in the formation of monomeric species. The caesium triphosphenide (49), involving a phosphorus analogue of the allyl anion, has been prepared from the previously described sodium complex. Unlike the sodium and potassium complexes, which are monomeric, the caesium complex has a polymeric structure. A variety of arylphosphide complexes of magnesium, calcium, strontium and barium have been prepared and their solid state structures characterised. Cop-per(I)-, silver(I)- and gold(I)-complexes of the cyclo-(P ion have also... 

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