Umsetzungen des Tetrakis[bis(trimethylsilyl)methyl]dialans(4) mit Methylisothiocyanat und Phenylisocyanat – Insertion in die Al?Al-Bindung bzw. Fragmentierung

Reactions of Tetrakisbis(trimethylsilyl)methyl]dialane(4) with Methylisothiocyanate and Phenylisocyanate – Insertion into the Al? Al Bond and Fragmentation Tetrakisbis(trimethylsilyl)methyl]dialane(4) 1 reacts with methyl isothiocyanate under cleavage of the C?S double bond and insertion of the remaining isonitrile fragment into the Al? Al bond. As shown by crystal structure determination a three-membered AlCN heterocycle ( 4 ) is formed by the interaction of the nitrogen lone pair with one unsaturated Al atom leading to an acute angle at the aluminium center N? Al? C of 36.6°. In contrast the reaction with the hard base phenyl isocyanate yields a mixture of many unknown compounds, from which only one ( 5 ) could be isolated in a very poor yield. The crystal structure of 5 reveals only one dialkyl aluminium fragment and a chelating ligand formed by the trimerization of the isocyanate under loss of one CO group and addition of a hydrogen atom. 5 was also synthesized by the specific reaction of the chloro dialkyl aluminium compound (R = CH(SiMe₃)₂) with LiH₅C₆? N?C(O)? N(C₆H₅)? C(O)? N(H)? C₆H₅].