Monomeric Calcium Amides

Most monomeric calcium amides involve the use of neutral donor molecules to prevent association. The only example of a three-coordinate mononuclear Ca amide, [Ca N(SiMe3)-(SiBu Ph2) 2(thf)], was prepared from CaF and KN(SiMe3)(SiBu Ph2) similar reaction... 

A comparison of these compounds with the corresponding zinc derivatives should clarify the influence of the empty d orbitals involved in the bonding situation of the alkaline earth metal bis(phosphanides). Whereas zinc bis[bis(trimethylsilyl)amide] is monomeric due to the steric demand of the bulky amide ligand [6], the trimethylsilyl substituted phosphanide leads to oligomers such as dimers or trimers [7], The influence of the pnicogen atom is small, thus the phosphorus and arsenic derivatives (Fig. 5.) look very similar [8] or even crystallize isotypically. In contrast to the d metals calcium, strontium and barium, zinc derivatives solely build up monocyclic ring systems. 

Methacrylamide Methyl methacrylate (76 g) is shaken for 7 days with ammonia solution (d 0.885 390 ml). The homogeneous solution is then evaporated in portions in a vacuum (19 mm) on a water-bath (78°), and the crude product is dried over calcium chloride to constant weight (65 g), broken into small pieces, and dissolved in methylene chloride (580 ml) boiling under reflux. The solution is filtered through a filter heated by hot water, and the residue is extracted again with methylene chloride (60 ml). When the filtrates are cooled in an ice-bath, monomeric methacrylamide crystallizes two further fractions can be obtained from the mother liquors, bringing the total yield of material melting at 95-109° up to 48 g (75%). To obtain the pure amide, as thin tablets, m.p. 110-111°, requires repeated recrystallization. 

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