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Keywords:

  • cycloaddition;
  • nitrile;
  • metallapyridinium;
  • metallapyridine;
  • osmium

Abstract

A novel [4+2] cycloaddition reaction between osmium alkenylcarbyne complex [OsHCl2{[TRIPLE BOND]CC(PPh3)[DOUBLE BOND]CHPh}(PPh3)2]+BF4− (1) and nitriles (acetonitrile and benzonitrile) provided metallapyridiniums [OsCl2{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhCR[DOUBLE BOND]NH}(PPh3)2]+BF4− (R=CH3 (2), Ph (3)) and OsCl3{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhCPh[DOUBLE BOND]NH}(PPh3) (4). A possible mechanism was proposed. Treatment of 2 with n-BuLi and NEt3 afforded osmapyridines OsCl2{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhCCH3[DOUBLE BOND]N}(PPh3)2 (5) and [OsCl{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhCCH3[DOUBLE BOND]N}(C6H5N)(PPh3)2]+BF4− (6). The ligands of osmapyridiniums 2 and 4 were changed, thus providing a series of osmapyridiniums [OsCl(SCN){[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}(PPh3)2]+Cl (7), OsCl(SCN)2{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}(PPh3) (8), Os(SCN)3{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}(PPh3) (9), [OsCl{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}(CH3CN)(PPh3)2]+(BF4−)2 (10), [OsCl{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}-(η2-1,10-phenanthroline)(PPh3)]+(BF4−)Cl (11), [OsCl{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhC(CH3)[DOUBLE BOND]NH}(η2-8-hydroxyquinoline) (PPh3)]+BF4− (12), and [Os{[DOUBLE BOND]CHC(PPh3)[DOUBLE BOND]CPhCPh[DOUBLE BOND]NH}(CH3CN)3(PPh3)]+(BF4−)3 (13). Most of these products were characterized by NMR spectroscopy, elemental analysis and single crystal X-ray diffraction.