The crystal structures of certain transitional metal complexes, in particular those containing mercuric chloride

• Main Author: Nowell, Ian William
• Published: University of Leicester 1969
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.737112

The main part of this thesis deals with the X-ray analysis of compounds formed by the reaction of d8 transition metal complexes with mercuric chloride. Equimolar amounts of dicarbonylcyclopentadienylcobalt(I) and mercuric chloride react to give a complex having the stoichiometry (?-C5H5)Co(CO)2 .HgCl2. The structure of this compound has been determined and is found to contain discreet mercuric chloride adducts. The bonding between the mercury and the cobalt atoms is best considered as involving a metal- donor metal metal bond, with dicarbonylcyclopentadienyl- -cobalt(I) acting as the Lewis base and mercuric chloride as the Lewis acid. This is one of a limited number of examples of this type of metal-metal bonding and an investigation was undertaken of the closely related compound (?-C5H5) Co(CO)2.3HgCl2. This complex was found to contain (?-C5H5)Co(CO)2HgCl+ cations, Cl-anions and HgCl2 molecules. Although no discreet mercuric chloride adducts are present, the cationic species can still be considered as containing a metal-donor Co-Hg bond, and the relative values of bond lengths found in the two dicarbonyl- -cyclopentadienylcobalt complexes are discussed. While pentacarbonyliron is known to give an unstable 1:1 adduct with mercuric chloride, suitably phosphine substituted iron carbonyls give rise to stable products. Thus, Fe(CO)3(PMe2?)2 was prepared and suitable reaction with mercuric chloride gave the complex Fe(CO)3(PMe2?)2.HgCl2. An attempted X-ray analysis of this compound has been undertaken. The structure of one of the products formed from the reaction of trifluoroacetonitrile with tetrakistriphenylphosphineplatinum(O) has been determined. The compound is found to have the molecular formula (?3P)2Pt(CF3CN)2NH, rather than the expected one of ((?3P)2Pt(CF3CN)3, and this has been attributed to hydrolysis of the trifluoroacetonitrile. The possible structures of certain other trifluoroacetonitrile complexes are discussed.