Umsetzung von Isothiocyanaten und Isonitrilen mit R₂Al–AlR₂ [R = CH(SiMe₃)₂]; ein‐ und zweifache Insertion von Isonitril in die Aluminium‐Aluminium‐Bindung

Reaction of Isothiocyanates and Isonitriles with R 2 Al–AlR 2 [R = CH(SiMe 3 ) 2 ]; Single and Double Insertion of Isonitrile into the Al–Al Bond Tetrakis[bis(trimethylsilyl)methyl]dialuminium(4) 1 reacts with phenyl or tert ‐butyl isothiocyanate with cleavage of the C = S double bond. Two compounds are formed: R 2 Al‐S‐AlR 2 [R = CH(SiMe 3 ) 2 ] 3 and R 2 Al‐C(NR')‐AlR 2 ( 4 R' = C 6 H 5 ; 5 R'= CMe 3 ) with a sulfur atom or an isonitrile group inserted between the aluminium atoms. Compounds 4 and 5 were isolated in high yield by the reaction of 1 with the appropriate isonitriles. By using an excess of phenyl isonitrile a dark red compound 6 is obtained with two isonitrile units inserted into the Al–Al bond and formation of a C–C single bond. According to crystal structure determinations of 4 and 6 a three‐membered heterocycle is formed by the interaction of the nitrogen lone‐pair to one of the Al atoms in 4 , while in 6 both Al atoms are four‐coordinated by bonding to a nitrogen and a carbon atom with formation of two across the C–C bond anellated four‐membered heterocycles. As shown by NMR spectroscopy the molecular structure of 4 with one stereochemically saturated and one unsaturated Al atom is unchanged in solution even upon heating to 100°C.