THE FIRST PLATINUM(IV) COMPLEXES WITH GLUCOPYRANOSIDE LIGANDS - A NEWCOORDINATION MODE OF CARBOHYDRATES

[(PtMe3I)(4)] reacts with AgBF4 in acetone to give fac-[PtMe3(Me2CO)(3 )]BF4 (2) which was isolated as strongly moisture and air sensitive, c olorless crystals and characterized by microanalysis and NMR spectrosc opy (H-1, C-13, Pt-195). The X-ray structure analysis (orthorhombic, P cab, a = 15.599(3) Angstrom, b = 15.685(2) Angstrom, c = 15.763(3) Ang strom, Z = 8) reveals that 2 is monomeric and that the cation exhibits local C-3 upsilon, symmetry. The reaction of 2 with glucopyranoses (1 ,6-anhydro-beta-D-glucopyranose (3a), 1-methyl-alpha-D-glucopyranoside (3b), and 1-phenyl-beta-D-glucopyranoside (3c)) yields carbohydrate c omplexes [PtMe3L]BF4 (4a-4c, L = 3a-3c). The complexes were characteri zed by microanalysis, ESI mass spectrometry and by NMR spectroscopy (H -1, C-13, Pt-195) displaying that the carbohydrates act as tridentate chelating ligands coordinated by the hydroxyl groups 2-OH and 4-OH and by the acetal oxygen atom of the pyranose ring. This structure was al so confirmed by X-ray structure analysis of 4a (orthorhombic, P2(1)2(1 )2(1), a = 6.404(1) Angstrom, b = 8.636(2) Angstrom, 27.161(5) Angstro m, Z = 4). The cyclic system of the two five-membered and the one six- membered 1,3,2-dioxaplatina rings is not free from angle strain; two O -Pt-O angles are distinctly smaller than 90 degrees (O2-Pt-O5 73.6(2), O4-Pt-O5 75.6(2)degrees). The Pt-O bond to the acetal oxygen atom in the pyranose ring is significantly longer (Pt-O5 2.288(5) Angstrom) th an the two Pt-OH bonds (Pt-O2 2.246(5), Pt-O4 2.248(4) and belongs to the longest Pt-O bonds at all.