Synthesis and characterization of liquid platinum compounds

Liquid platinum complexes were obtained with a ligand with alkyl chains tha t attach to the coordination plane perpendicularly and herewith render a cl ose packing of the molecules difficult for certain chain lengths. Bis(O, O' -dialkyldithiophosphato)platinum(II) complexes, Pt(C(x)dtp)(2) where the al kyl chains are methyl (x = 1), ethyl (x = 2), propyl (x = 3), butyl (x = 4) , pentyl (x = 5), hexyl (x = 6), heptyl (x = 7), dodecyl (x = 12), and octa decyl (x = 18), were investigated. The platinum compounds were synthesized via two routes: reaction of tetrachloroplatinate(IT) with ammonium-O,O'-dia lkyldithiophosphates or oxidative addition of (O,O'-dialkylthiophosphoryl)d isulfides to tris(styrene)platinum(0). The melting temperatures as a functi on of the alkyl chain length show a minimum for the complex with pentyl gro ups. The complexes with pentyl and hexyl groups are liquid at room temperat ure, and the complexes with butyl and heptyl groups melt only slightly abov e room temperature. Depending on the complex, the low melting temperatures are induced by an unfavorable packing of the molecules in the solid state, reflected in a low melting enthalpy, or melting entropy. The molecular weig hts of the liquid complexes are between 700 and 800 and, therefore, extraor dinarily high for liquid metal compounds. Depending on the alkyl groups, th e complexes decompose at 172-241 degrees C. Crystals of bis(O,O'-diethyldit hiophosphato)platinum(II), Pt(C(2)dtp)(2), are monoclinic, space group P2(1 )/n, a = 8.90, b = 8.70, c = 12.45 Angstrom, alpha = gamma = 90 degrees, be ta = 100.89 degrees, and Z = 4. (C) 2000 Elsevier Science S.A. All rights r eserved.