Synthesis and Characterization of Novel Guanidine Ligands Featuring Biphenyl or Binaphthyl Backbones

In this paper we report on the synthesis and characterization of several new 2,2`-bisguanidino-1,1`-biphenyl and -binaphthyl ligands as well as the electron donor 3,3`,4,4`-tetrakis(tetramethylguanidino)-1,1`-biphenyl. Chiral bisguanidine ligands were prepared with binaphthyl backbones. The solid-state structures were analysed by single-crystal X-ray diffraction. UV/Vis and Raman spectra provided a qualitative insight into the rotational barriers in solution and in the solid state. Finally, late-transition-metal complexes of two of these ligands were prepared. These complexes prefer a kappa(1) rather than a kappa(2) coordination mode. The discussion of the experimental results is complemented by quantum chemical (DFT) calculations. Finally, we report on the first catalytic test reactions.