REACTIONS OF TETRAKIS[BIS(TRIMETHYLSILYL) METHYL]DIALANE(4) WITH METHYLISOTHIOCYANATE AND PHENYLISOCYANATE - INSERTION INTO THE AL-AL BOND AND FRAGMENTATION

Tetrakis[bis(trimethylsilyl)methyl]dialane(4) 1 reacts with methyl iso thiocyanate under cleavage of the C=S double bond and insertion of the remaining isonitrile fragment into the Al-Al bond. As shown by crysta l structure determination a three-membered AlCN heterocycle (4) is for med 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 degrees. In contrast the reaction with the hard base phenyl isocyan ate 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 r eveals only one dialkyl aluminium fragment and a chelating ligand form ed by the trimerization of the isocyanate under loss of one CO group a nd addition of a hydrogen atom. 5 was also synthesized by the specific reaction of the chloro dialkyl aluminium compound (R=CH(SiMe(3))(2)) with Li[H5C6-N=C(O)-N(C6H5)-C(O)-N(H)-C6H5].