Neutral Pyridyl-Functionalized C,N-ortho-Chelated Aminoaryl Platinum(II) Corner Building Blocks for Application in Coordination Reactions

Two homoleptic pyridyl-functionalized C,N-ortho-chelating aminoaryl platinum(II) complexes, cis-[Pt(eta(2)-C,N)] (3a,b), were prepared via an unconventional method involving the initial synthesis of a bromide-functionalized C,N-chelating aminoaryl platinum(II) precursor complex 8, to which subsequently pyridyl groups were attached via a Suzuki-Miyaura C-C coupling reaction. The electron-donating properties of the pyridyl nitrogen atoms of the resulting complexes (3a,b) were used in complexation reactions with monocationic NCN-pincer (NCN = [C6H3(CH2NMe2)(2-)2,6]-) platinum(II) (11a) and palladium(II) (12a) nitrate complexes [M(NCN)(NO3)], thereby obtaining four trimetallic coordination complexes 16-19. The difference in the pyridine-metal coordination behavior between platinum and palladium was studied by varying the ratios of the reagents and by variable-temperature NMR experiments. IR and Raman analyses of 11a and 12a were performed to determine the coordination behavior of the nitrate counteranion, and it was found that both NO3- and H2O coordinate to the metal centers. The crystal structure determinations of free pyridyl complex 3a, [Pt(NCN)(NO3)] (11a), and [Pt(NCN)(NO3)].(H2O) (11b), as well as the crystal structure of trisplatinum coordination complex 16, are reported.