AMIDO, IMIDO AND CARBENE COMPLEXES OF CHROMIUM

Interaction of CrCl2 with LiNHAr, Ar* = 2,6-(Pr2C6H3)-C-i, in thf gav e the homoleptic amide Cr-II (NHAr)(4) [Li(thf)](2) (1), which resist ed further deprotonation by strong bases. Interaction of Cr(Nmes)(2) C l-2,mes = 2,4,6-Me3C6H2, with LiNHmes gave the mesitylimido complex [C r-VI(Nmes)(3)(NHmes)]Li(Et2O)(2) (2), which also resisted further depr otonation. Pentamethylcyclopentadienyl chromium(V) complexes CpCr(NAr ')X-2, X = SC6H5, Ar' = 2-(PrC6H4)-C-i, (3); 4-Me-C6H4 (4), 2-(BuC6H4) -C-t, (5), have been prepared by interaction of (CpCrBr2)(2) with Li( Ar'NSPh). Reaction of (CpCrBr2)(2) with mesitylnitrene, generated fro m mesN(3) in situ, gave the ionic Cr-III species [CpCrBr3][mesNH(3)], (6). (3) and (5) as well as the previously reported CpCr(NBut)X-2 ca n be transformed to the corresponding chlorides (7)-(9), by reaction w ith BCl3. Finally, interactions of Cr(mes)(2)(thf)(3) with the carbene CN(Pr-i)C2Me2NPri = L gave Cr(mes)(2)L-2 (10). The X-ray crystal stru ctures of compounds (1)-(3), (6), (7), (9) and (10) have been determin ed. (1) is a molecular cluster with square planar Cr-II and with two [ Li(thf)](+) ions bridging the nitrogen atoms of pairs of amide ligands on opposite sides of the square. (2) has a distorted tetrahedral meta l geometry with one [Li(Et2O)(2)](+) ion bridging the nitrogen atoms o f two imido ligands. (3) has a monomeric pseudo tetrahedral structure, as do (7) and (9) and the anion in (6). (10) has a trans square plana r structure in which the Cr-C distances to the mesityl and carbene lig ands are equal within error.