REGIOSELECTIVE COMPLEXATION OF UNPROTECTED CARBOHYDRATES BY PLATINUM(II) - SYNTHESIS, STRUCTURE, COMPLEXATION EQUILIBRIA, AND HYDROGEN-BONDING IN CARBONATE-DERIVED BIS(PHOSPHINE)PLATINUM(II) DIOLATE AND ALDITOLATE COMPLEXES

Treatment of bis(phosphine)platinum(II) carbonate complexes (LL)Pt(CO3 ) (e.g., LL = 1,3-bis(diphenylphosphino)propane) with vicinal diols (i .e., HOCR(1)R(2)CR(3)R(4)OH) gives equilibrium conversion to the corre sponding diolate complexes (LL)Pt(OCR(1)R(2)CR(3)R(4)O), which are rea dily isolated in good yield. From competition experiments, relative di ol complexation constants were determined as a function of both the di ol and the phosphine substituents and found to span a range of over 10 (4). Corresponding triolate and alditolate complexes were similarly pr epared, for which very distinct equilibrium isomeric regioselectivitie s are observed, favoring complexation of gamma,delta-threo diols. An X -ray structure of (dppp)Pt(D-mannitolate) shows that the mannitol is b onded to the platinum as its dianion via the oxygens on C3 and C4 to f orm a 2,5-dioxaplatinacyclopentane chelate ring and that three differe nt strong intramolecular hydrogen-bonding interactions are present bet ween the hydroxyl hydrogens and the metallacycle oxygens (O...O (av) = 2,65(2) A), forming five-, six-, and seven-membered rings. Crystal da ta for PtP2O6C33H38.CH2Cl2: P2(1)2(1)2(1), Z = 4, T approximate to 20 degrees C, a = 11.225(2) Angstrom, b = 15.875(3) Angstrom, c 19.964(4) Angstrom, R(F-o) = 0.058, R(w)(F-o) = 0.062.