Abstract
The low-valent and low-coordinate quintuply-bonded dichromium complex, [(OEt2)KCr(κ1:κ2-N2Ndipp)]2 (1) was supported by the sterically hindered three-nitrogen donor ligand, Li2[N2Ndipp](N2Ndipp= 4-methyl-2,6-(NDipp)2pyridine) (Dipp = 2, 6-iPr2-C6H3). Treatment of 1 with 1 equiv of CaI2 leads to the formation of the hetereotrinuclear metal complex, {Ca(THF)2Cr2[μ3-κ1:κ2-(N2Ndipp)2]} (2), with the Cr-Cr quintuple bond retained. Treatment of 2 with organic azides gives Cr imido complexes. Reaction of 2 with p-tolyl azide gives {Ca[Cr(p-tolylN)(μ-p-tolylN)]2[μ3-κ1:κ2-(N2Ndipp)2]} (4), in which two imido groups bridge and two imido groups chelate to chromium atoms. Treatment of 2 with trimethylsilyl azide produces the complex, {(μ-THF)[Cr2Ca(μ-TMSN)2][μ3-κ1:κ2-(N2Ndipp)2]} (5). Reaction of 2 with 1-adamantyl azide generates the complex, {Ca(1AdN)Cr(μ-1AdN)2Cr[μ3-κ1:κ2-(N2Ndipp)2]} (6). For comparison, we carry out the reaction of 1 with YbI2(THF)2 to give rise to the formation of {Yb(THF)2Cr2[μ3-κ1:κ2-(N2Ndipp)2]} (3), which is confirmed by the 1H NMR spectroscopy. Treatment of 3 with trimethylsilyl azide leads to the isolation of {[YbCr2(μ-TMSN)3][μ3-κ1:κ2-(N2Ndipp)2]} (7), which is structurally similar to 5. The three metal centers of 5 and 7 are bound via the nitrogen atom of a trimethylsilyl imido group. Moreover, the bonding fashion of N2Ndipp in its product is transformed from bridging to chelating. In addition, treatment of 2 with diphenylzinc generates the complex, {(THF)Ca[Cr(η1-C6H5)]2[μ3-κ1:κ2-(N2Ndipp)2]} (8), in which both phenyl rings are terminally coordinated to chromium atoms. The result is different from the carbozincation of alkynes and alkenes. In the second part of this thesis, treatment of Li2[N2Nmes](Mes = 2,4,6-CH3C6H2) with CrCl3 leads to the formation of Cr2[μ3-κ1:κ2-(N2Nmes)2]3 (9), where two Cr atoms are spanned by three N2Nmes ligands. However, we could not obtain the diamagnetic product upon reduction of 9. Afterwards, treatment of Li2[N2Nmes] with CrCl2 generates the complex, {[(Cl)Cr(μ-Cl)Cr(THF)][μ3-κ1:κ2-(N2Nmes)2]} (10), in which two Cr atoms are ligated bridged by two N2Nmes ligands. Nevertheless, stepwise reduction of 10 generates orange intermediate, and then leads to the formation of 9. The isolation of the diamagnetic product is still not achieved.