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

Reaction de l'oxygene avec des complexes porphyriniques de Cr(II). On a isole le complexe (TPP) CrOCr(TPP) de la reaction CrO(TPP) avec Cr(II)(TPP). La formation de complexe μ-oxo similaires a ete demontree spectroscopiquement entre autre CrO(P)/Cr(P') ou P et P' peuvent etre semblables ou differents. TPP=la tetraphenylporphyrine

Oxochromium compounds. 2. Reaction of oxygen with chromium(II) and chromium(III) porphyrins and synthesis of a .mu.-oxo chromium porphyrin derivative

Homonuclear and heteronuclear oxo-bridged compounds of the transition elements

New salicylaldimine chelates of divalent and trivalent ruthenium have been synthesized from RuCl2(PPh3)3. The RuII complex trans- Ru(salen)(PPh3)2 is stable in the solid but very unstable to oxidation in solution. The RuIII derivative, Ru(salen)Cl(PPh3), displays magnetic and e.s.r. properties consistent with a low-spin d5 system under a ligand-field of rhombic symmetry.

Ruthenium complexes with a tetradentate salicylaldimine Schiff base

Electrospray mass spectrometric (ESMS) studies have been made on some representative examples of the trinuclear complexes [M 3 O(RCOO) 6 (H 2 O) 3 ] + (M=Cr, Fe; R=H, CH 3 , CH 3 CH 2 , (CH 3 ) 3 C) in methanol and pyridine/ methanol solutions. The nonbridging water ligands in the Cr(III) complexes partially exchange with the solvent molecules and ions containing the central Cr 3 O(RCOO) 6 core, and various combinations of terminal ligand are observed. At low first skimmer voltages, intact ions with three terminal ligands are detected, but as the skimmer voltage is increased, interaction with solvent molecules within the ion sourcecauses collisionally activated decompositions to occur, leading to progressive loss of the labile terminal groups

Electrospray mass spectrometric study of [M3O(RCOO)6L3]+ cations (M = chromium, iron; L = H2O, MeOH, py)

Tin(IV) alkoxides react with pentane-2,4-dione (acetylacetone) and other β-diketones to yield Sn(OR)3(chel) or Sn(OR)2(chel)2 derivatives. Sn(Opri)3(acac) has been shown to be dimeric in the solid state by a single-crystal X-ray diffraction study, the tin atoms being linked by two alkoxide bridges. In solution l19sn n.m.r. spectral data show that this single complex rapidly converts into a mixture of tin-containing species followed by slow disproportionation to the bis derivative Sn(OPri)2(acac)2 and Sn(Opri)4. The bis complexes Sn(OR)2(acac)2 appear to exist predominantly in solution with cis arrangements of alkoxide groups even when OBut or 2,2,6,6-tetramethylheptane-3,5-dione (dipivaloylmethane) are present.

Bruce O. West

Papers

Oxochromium compounds. 2. Reaction of oxygen with chromium(II) and chromium(III) porphyrins and synthesis of a .mu.-oxo chromium porphyrin derivative

Homonuclear and heteronuclear oxo-bridged compounds of the transition elements

Ruthenium complexes with a tetradentate salicylaldimine Schiff base

Electrospray mass spectrometric study of [M3O(RCOO)6L3]+ cations (M = chromium, iron; L = H2O, MeOH, py)

The Structures of Mono and Bis β-Diketonate Tin(IV) Alkoxide Complexes