Oxido Pincer Ligands – Exploring the Coordination Chemistry of Bis(hydroxymethyl)pyridine Ligands for the Late Transition Metals

Coordination of the 2,6‐bis(hydroxymethyl)pyridine‐based oxido pincer ligands RR′pydimH 2 [R = R′ = H (pydimH 2 ); R = R′ = Me (pydipH 2 ); R = 2‐tolyl, R′ = Me (pydotH 2 )] towards late transition metals Co II , Ni II , Cu II , Zn II , Pd II and Pt II allows the formation of molecular species (complexes), which exhibit three main structural motifs in the solid state. The two main species are pentacoordinate [(RR′pydimH 2 )MCl 2 ] and hexacoordinate [(RR′pydimH 2 ) 2 M]X 2 , both of which are stable in solution and can be interconverted by changing the solvent polarity. The disproportionation equilibrium [(RR′pydimH 2 )MCl 2 ] [rlhar2] [(RR′pydimH 2 ) 2 M] 2+ + [MCl 4 ] 2– was studied by optical spectroscopy. The chiral ligand pydotH 2 allows the formation of chiral complexes. In the square‐planar complexes [(pydimH 2 ) 2 MCl 2 ] (M = Pd II or Pt II ) the oxido donor functions of the ligands do not take part in the coordination.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)