Four different pincer ligands, which prove that the disposition of the donor atoms in pincer ligands allows them to develop a marked ability to form less common coordination polyhedra and… Click to show full abstract
Four different pincer ligands, which prove that the disposition of the donor atoms in pincer ligands allows them to develop a marked ability to form less common coordination polyhedra and to favor unusual metal oxidation states, have been generated starting from OsH6(PiPr3)2 and 2-phenyl-6-(1H-pyrazol-3-yl)pyridine (Hpz-py-Ph) in order to stabilize phosphorescent, pentagonal-bipyramidal osmium(IV) emitters. Complex 1 reacts with the disubstituted heterocycle to give OsH2{κ3-N,N′,C-(pz-py-C6H4)}(PiPr3)2 (2), as a result of the activation of a phenyl o-CH bond and the pyrazolyl NH of the pyridine substituents. The addition of methyl trifluoromethanesulfonate (MeOTf) to 2 produces the methylation of the free N atom of the pz group and the formation of the salt [OsH2{κ3-N,N′,C-(Mepz-py-C6H4)}(PiPr3)2]OTf (3), which undergoes deprotonation of the metal center in the presence of KOtBu. The resulting monohydride OsH{κ3-N,N′,C-(Mepz-py-C6H4)}(PiPr3)2 (4) is unstable and evolves into OsH2{κ3-C,N,C′-(Mepz-py-C6H4)}...
               
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