Catalytic C–N bond formation in guanylation reaction by N-heterocyclic carbene supported magnesium(II) and zinc(II) amide complexes

• NHC supported magnesium and zinc bis(amide) complexes.
• Catalytic addition of amines to carbodiimides.
• Catalytic C–N bond formation in guanylation reaction.
• X-ray structures of NHC adducts of magnesium and zinc bis(amides).

The catalytic activity of N-heterocyclic carbene (NHC) supported magnesium(II) and a zinc(II) amide complex towards the addition of N–H bond of amine to carbodiimide was studied. Treatment of a free carbene i.e., 1,3-di-tert-butylimidazol-2-ylidene (ItBu) with magnesium and zinc bis(amide) i.e., M[N(SiMe3)2]2, M = Mg or Zn in toluene led to the formation of ItBu:M[N(SiMe3)2]2, M = Mg(1) and Zn(2) compounds, respectively. Both 1 and 2 were characterized by multinuclear (1H, 13C and 29Si) NMR spectroscopy and single X-ray crystal structure analysis. Solid state structures revealed that both complexes are monomeric in nature and their magnesium and zinc atoms are three coordinated and distorted trigonal planar in geometries. Furthermore, compounds 1 and 2 were tested as catalysts for the guanylation reaction of addition of amine to carbodiimide and turned to be excellent catalysts.

Two new examples of well defined NHC supported magnesium and zinc bis(amide) complexes have been shown. And also, catalytic addition of various aromatic primary and cyclic secondary amines to carbodiimides led to the formation of guanidines has been established.Figure optionsDownload as PowerPoint slide