Amino-cumulenylidenes

Class C. Neutral si -Carbon Ligands Amino- and Nonamino-Cumulenylidenes... 

Heteroatom-substituted allenylidene and higher odd-chain cumulenylidene complexes [M]=C(=C) =CR R ( = 1, 3, 5 R /R = NR2, OR, SR, SeR) are directly related to the classical Fischer-type carbene complexes, being regarded as their functional carbo-mers [5-7]. However, although two of the first allenylidene complexes synthesized were the amino-allenylidene derivatives [M =C=C=CPh (NMe2) 1(00)5] (M = Or, W) [8], the chemistry of these compounds has been much less developed [9, 10]. In fact, as aheady discussed in Chapter 6 the chemistry of metallacumulenes is largely dominated by the all-carbon substituted representatives... 

As already commented in the introduction of this article, theoretical calculations have suggested an increased stability of odd-chain metallacumulenes bearing Ti-donor substituents when compared to their all-carbon substituted counterparts [16]. However, despite this theoretical prediction, synthetic efforts directed to the preparation of heteroatom-substituted metallacumulenes longer than allenylidenes have been scarce till now. All the reported examples belong to the family of amino-substituted Group 6 cumulenylidenes. In this section a survey of their chemistry is presented. 

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