NEW N-H ... PT INTERACTIONS - THE NATURE OF THE BOND

Acetylated 8-aminoquinoline, 7, is shown to be a ligand which, once complexed to Pt(II) containing cyclometalated ligands, gives rise to cationic complexes containing new three-center N-H---Pt bonds. The presence of this bonding can be deduced by H-1 and 15N NMR spectroscopy in that the magnitudes of the spin-spin couplings 1J(Pt-195, H-1) and 1J(N-15, H-1) can be used to analyze these interactions. In solution these new three-center bonds are not very strong, and there is exchange between coordinated and uncordinated 7 as shown by phase-sensitive H-1 NOESY. The solid-state structure of the cyclometalated complex [Pt{(2,6-CH2Ph2)C6H3}(7)] (CF3SO3) (6) was determined by X-ray diffraction and reveals that the hydrogen of the N-H is ca. 2.2(1) angstrom from the metal. Crystal data for 6: monoclinic Cc, a = 15.429(1) angstrom, b = 14.194(1) angstrom, c = 19.185(2) A, beta = 101.89(1)degrees, V = 4111.4 angstrom3, and Z = 4. The combination of X-ray distances and NMR coupling constants provides insight both in to new and previously postulated N-H---Pt bonds.