On the Reduction of NC Chelated Organoantimony(III) Chlorides

The conversion of organolithium compound LLi, for which L = [o‐C6H4(CH=NC6H3iPr2‐2,6)]–, with antimony chloride gave the molecular chlorides LSbCl2 (1) and L2SbCl (2) depending on the molar ratio used (either 1:1 or 2:1). Bothcompounds were characterized by using 1H and 13C NMR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. The reaction of 1 with two molar equivalents of K[B(sBu)3H] led to smooth formation of compound L4Sb4 (3) as a result of hydrogen elimination from the unstable hydrido compound. On the contrary, a similar reaction between 2 and K[B(sBu)3H] (1:1) did not result in hydrogen elimination and the formation of expected distibine L2SbSbL2, but an addition of an in situ generated L2Sb–H bond across the C=N functionality in the pendant arm of one of the ligands was observed. The reduction of compound 2 with an excess amount of magnesium was strongly dependent on the reaction time. The distibine L2SbSbL2 (5) could be isolated after 4–5 h from this reaction mixture. Elongation of the reaction time to 1 d (and more) gave a more complicated reaction mixture, in which three products, distibine 5, compound 3 and organomagnesium compound L2Mg(THF) (6), were characterized by single‐crystal X‐ray diffraction in addition to other unidentified products. These results can be rationalized by a migration of the ligand L from the antimony atom to the magnesium, thus explaining formation of both L4Sb4 (3) compound and L2Mg(THF) (6). Attempts to reduce organoantimony compounds LSbCl2 and L2SbCl that contain the NC chelating ligand [o‐C6H4(CH=NC6H3iPr2‐2,6)]– by preparation from unstable hydrido precursors is described. The result of the reaction stronglydepends on the structure of the precursor and proceeds as the expected reduction (LSbCl2) or as an addition across the C=N double bond of the ligand backbone (L2SbCl).