The use of conductivity measurements in organic solvents for the characterisation of coordination compounds

“All new is well-forgotten old”, the proverb goes. The current “fluorine boom” is news only to a novice in the field: the exceptional importance of fluorinated organic compounds in numerous areas has been known for a long time. The sharpest increase in the number of fluorine-containing pharmaceuticals and agrochemicals is dated back to 30 years ago. Also around that time (1979), the first monograph devoted to industrial applications of organofluorine compounds was published, covering not only fluorine-containing biologically active materials but also refrigerants, propellants, surfactants, textile chemicals, polymers, and dyes. The increasingly broad realization of the key role of organofluorine compounds in numerous areas has recently attracted many new scientists to the field. The development of new methods for the selective introduction of fluorine and fluorinecontaining groups into organic molecules for biologically active and other useful materials has become a hot area. Over 100 reviews, book chapters, and highlights on this subject have appeared in the literature in the past few years. As citing all of these publications in this review article is impossible, we provide references to only the most recent, general, and comprehensive ones. Molecules bearing a trifluoromethyl group constitute one of the most important classes of selectively fluorinated compounds. As early as 1928, Lehmann reported his observations of biological activity of some trifluoromethylated organic derivatives and already in 1959 Yale published a detailed review article entitled “The Trifluoromethyl Group in Medicinal Chemistry”. Since then, numerous books and reviews have appeared in the literature covering various aspects of trifluoromethylated organic and organometallic compounds. Within this family, derivatives bearing the CF3 group on aromatic rings are particularly numerous and important. Some examples of such compounds used as active ingredients of pharmaceuticals and agrochemicals are shown in Scheme 1. Trifluoromethylated building blocks and intermediates are clearly needed to make such molecules. The simplest trifluoromethylated aromatic compound, benzotrifluoride, was originally prepared by Swarts at the end of the 19th century. In his work, Swarts treated benzotrichloride with “two thirds of its weight of antimony fluoride” to obtain a mixture of PhCF2Cl and PhCF3, from which the two were separated and isolated pure by distillation. In the early 1930s, two industrial groups, one from Kinetic Chemicals, Inc. and one from I. G. Farbenindustrie AG patented their discoveries on the successful use of HF instead of SbF3 for the Swarts reaction. These inventions were the starting point for the modern large-scale manufacturing of trifluoromethylated aromatics. Other methods have been developed for conversion of various C1 units on the ring to CF3 with a variety of fluorinating agents. While representing an outstanding discovery and a classic of organic and organofluorine chemistry, the Swarts reaction is nonetheless neither atom-economical nor environmentally benign, as it deals with stoichiometric quantities of hazardous chemicals and generates large amounts of chlorine waste. To convert a CH3 group on the ring to CF3, the methyl is first exhaustively chlorinated to produce 3 equiv of HCl as a

Aromatic Trifluoromethylation with Metal Complexes

Laboratory for Advanced Materials and New Catalysis, School of Chemistry and Materials Science, Hubei University, Wuhan 430062, China,Laboratory of Natural Gas Utilization and Applied Catalysis, Dalian Institute of Chemical Physics of Chinese Academy of Sciences, Dalian 116023,China, and Jingmen Technological College, Jingmen 448000, ChinaReceived June 30, 2004

Advances in Homogeneous and Heterogeneous Catalytic Asymmetric Epoxidation

The reactions of ruthenium(II) complexes, [RuHCl(CO)(PPh3)2(B)] [B = PPh3, pyridine (py) or piperidine (pip)], with bidentate Schiff base ligands derived by condensing salicylaldehyde with aniline, o-, m- or p-toluidine have been carried out. The products were characterised by analytical, i.r., electronic, 1H-n.m.r. and 31P-n.m.r. spectral studies and are formulated as [RuCl(CO)(L)(PPh3)(B)] (L = Schiff base anion; B = PPh3, py or pip). An octahedral structure has been tentatively proposed for the new complexes. The Schiff bases and the new complexes were tested in vitro to evaluate their activity against the fungus Aspergillus flavus.

Ruthenium(II) complexes containing bidentate Schiff bases and their antifungal activity

Ligand environment and the structure of schiff base adducts and tetracoordinated metal-chelates

The molecular structures and magnetic properties of μ3-tetranuclear β-diketonate copper complexes [Cu(bzac)(μ3-OC2H4OCH3)]4 and [Cu(μ-dbm)(μ3-OC2H4OCH3)]4

The reaction of dioxygen with αβγδ-tetraphenyl-porphinatochromium (II) in toluene proceeds in two stages; a µ-oxo-chromium(III) intermediate is formed initially and this then further reacts with dioxygen to give the title complex, the structure of which has been determined by X-ray crystallography.

The autoxidation of a chromium (II) porphyrin: synthesis and structural characterisation by X-ray crystallography of αβγδ-tetraphenyl-porphinato-oxochromium(IV)

Synthesis and magnetic properties of .mu.-organoimido-bridged iron(III) salicylaldimine compounds. Structure of (.mu.-p-tolylimido)bis[(N,N'-ethane-1,2-diylbis(salicylaldiminato))iron(III)] ([Fe(salen)]2N(Tol))

Three major applications have been found for rare-earth compounds in Metal Organic Chemical Vapour Depostion (MOCVD) or Chemical Vapour Deposition (CVD). Yttrium 2,2,6,6-tetramethyl-3,5-heptanedionates and 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionates have been used in conjunction with barium and copper(II) β-diketonates to deposit YBa2Cu3O7−δ as superconducting thin films. Rare-earth fluorides and chlorides have been used for CFD doping of rare earths into MOCVD-deposited ZnS, whilst yttrium chloride has been used, with barium iodide and copper(I) chloride, to produce YBa2Cu3O7−δ superconducting material by CVD. Lanthanoid (Ln) tris(cyclopentadienyl) compounds, Ln(C5H5)3 or Ln(C5H4Me)3, have been used for doping of rare earths into 13–15 (III–V) semiconductors. Their volatility, structure/volatility relationships, and preparations are discussed. Possible alternative reagents and problems to be faced in doping 12–16 (II–VI) semiconductors are also considered.

Bruce O. West

Papers

The molecular structures and magnetic properties of μ3-tetranuclear β-diketonate copper complexes [Cu(bzac)(μ3-OC2H4OCH3)]4 and [Cu(μ-dbm)(μ3-OC2H4OCH3)]4

The autoxidation of a chromium (II) porphyrin: synthesis and structural characterisation by X-ray crystallography of αβγδ-tetraphenyl-porphinato-oxochromium(IV)

Synthesis and magnetic properties of .mu.-organoimido-bridged iron(III) salicylaldimine compounds. Structure of (.mu.-p-tolylimido)bis[(N,N'-ethane-1,2-diylbis(salicylaldiminato))iron(III)] ([Fe(salen)]2N(Tol))

CVD of metal organic and other rare-earth compounds

The structure of hydrated lead(II) dimethylacetate, [Pb6(O2CCH(CH3)2)12] 4H2O: A hexanuclear carboxylate