Different Products of the Reduction of (N),C,N‐Chelated Antimony(III) Compounds: Competitive Formation of Monomeric Stibinidenes versus 1 H ‐2,1‐Benzazastiboles

The reduction of N,C,N‐chelated antimony(III) chlorides [C 6 H 3 ‐2,6‐(CH=NR) 2 ]SbCl 2 (R=Ph ( 1 ), t Bu ( 2 ), Dip ( 3 ); Dip=2,6‐ i Pr 2 C 6 H 3 ) with an appropriate amount of KC 8 or Li[AlH 4 ] resulted in the formation of rare examples of monomeric stibinidenes [C 6 H 3 ‐2,6‐(CH=NR) 2 ]Sb (R=Ph ( 4 ), t Bu ( 5 ), Dip ( 6 )). Similarly, the reduction of compounds 1 or 2 by two equivalents of K[B( s Bu) 3 H] led to the stibinidenes 4 and 5 . In contrast, the analogous reaction of compound 3 resulted in the formation of an unprecedented stibinidene [C 6 H 3 ‐2‐(CH=NR)‐6‐(CH 2 NHR)]Sb ( 7 ) (R=Dip), in which the hydrogen atoms that come from the K[B( s Bu) 3 H] are incorporated into the ligand backbone. To gain further insight into this intriguing reactivity with K[B( s Bu) 3 H] and to assess the influence of the substitution at both the antimony atom and pendant substituents, we prepared compounds [C 6 H 3 ‐2‐(CH=NDip)]Sb(Ph)Cl ( 8 ) and [C 6 H 2 ‐2‐(CH=NDip)‐4,6‐( t Bu) 2 ]SbCl 2 ( 9 ). The treatment of compound 8 with K[B( s Bu) 3 H] smoothly led to the 1‐Ph‐2‐Dip‐1 H ‐2,1‐benzazastibole ( 11 ), whereas the reaction of compound 9 with K[B( s Bu) 3 H] resulted in either t Bu‐substituted 1‐Cl‐2‐Dip‐1 H ‐2,1‐benzazastibole ( 13 ) or the formation of unprecedented Sb−Sb dimer bis(2‐Dip‐1 H ‐2,1‐benzazastibole) ( 12 ) depending on the reaction stoichiometry. The miscellaneous reactivity of antimony(III) precursors with reducing agents together with the structure and bonding of the resulting products has also been investigated from a theoretical point of view.