Isolation and Crystal Structure of Novel by-products Observed During the Formation of bis(thiosemicarbazones)

During the condensation of 4-methyl-4-phenyl-3-thiosemicarbazide (3) with 2,3-butanedione an unexpected by-product, 8a-methyl-6,8a-dihydro-8-methyl-2-[N-methyl-N-phenylamino]-5H-1,3,4-thiadiazolo[3,2-d][1,2,4]triazine-5-thione, (5) was obtained in addition to the desired bis(thiosemicarbazone) (4). An X-ray crystal structure was obtained and is presented together with a proposed mechanism for its formation. A brief investigation of the coordination chemistry of bicycle (5) was carried out. The formation of cyclic compounds during the synthesis of analogues with extended backbones is also described.     

Liquid extraction of molybdophosphoric and molybdoarsenic acids: application to the determination of phosphorus in the presence of arsenic

The radioisotopes phohphorus-32 and arsenic-74 have been used to study the extraction of molybdophosphoric and molybdoarsenic acids from aqueous solution with various organic solvents. A method is described for the gravivmetric determination of phosphorus in the presence of arsenic which makes use of solvent extraction with n-butyl acetate. The results obtained for the determination of phosphorus in various types of iron and steel are described.     

Acetylacetonate bis(thiosemicarbazone) complexes of copper and nickel: towards new copper radiopharmaceuticals

A series of copper(II) and nickel(II) 1,3-bis(thiosemicarbazonato) complexes have been synthesised by the reaction of the metal acetates with pyrazoline proligands. In each case the complexes have an overall neutral charge with a dianionic ligand. The copper 1,3-bis(4-methyl-3-thiosemicarbazonato complex has been characterised by X-ray crystallography, which shows the copper is in an essentially square-planar symmetric N(2)S(2) environment. The nickel 1,3-bis(4-methyl-3-thiosemicarbazonato) and nickel 1,3-bis(4-phenyl-3-thiosemicarbazonato) complexes have been characterised by X-ray crystallography and show that in these cases the nickel is in a distorted square-planar environment, but the bonding mode of the ligands is unusual; the nickel binds to one of the aza-methinic nitrogen atoms and one hydrazinic nitrogen, creating one five-membered N-N-C-S-Ni chelate ring and one four-membered N-C-S-Ni chelate ring. Interestingly, the X-ray structure of the ethyl analogue [1,3-bis(4-ethyl-3-thiosemicarbazonato)nickel(II)] shows that in this case the nickel is symmetrically coordinated in the usual manner. The nickel complexes are diamagnetic and the different coordination modes are confirmed in solution by NMR spectroscopy. The complexes are susceptible to oxidation in air and a nickel complex, in which the central methylene carbon has been oxidised, has been characterised by X-ray crystallography and NMR spectroscopy. Electrochemical measurements show that the copper complexes undergo a reversible one-electron reduction at biologically accessible potentials.     

Phenylphosphatrioxa-adamantanes: bulky, robust, electron-poor ligands that give very efficient rhodium(I) hydroformylation catalysts

The cage phosphines 1,3,5,7-tetramethyl-6-phenyl-2,4,8-trioxa-6-phosphaadamantane (1a) and 1,3,5,7-tetraethyl-6-phenyl-2,4,8,trioxa-6-phosphaadamantane (1b) have been made by the acid catalysed addition of PhPH(2) to the appropriate beta-diketones; the acid used (HCl, H(3)PO(4) or H(2)SO(4)) and its concentration affect the rate and selectivity of these condensation reactions. Phosphines 1a and 1b react with [PdCl(2)(NCPh)(2)] to form complexes trans-[PdCl(2)(1a)(2)](2a) and trans-[PdCl(2)(1b)(2)](2b) as mixtures of rac and meso diastereoisomers. The platinum(II) chemistry is more complicated and when 1a or 1b is added to [PtCl(2)(cod)], equilibrium mixtures of trans-[PtCl(2)L(2)] and [Pt(2)Cl(4)L(2)](L = or ) are formed in CH(2)Cl(2) solution. Meso/rac mixtures of trans-[MCl(CO)(1a)(2)] M = Ir (6a) or Rh (7a) are formed upon treatment of MCl(3).nH(2)O with an excess of 1a and the anionic cobalt complex [NHEt(3)][CoCl(3)(1a)](9) was isolated from the product formed by CoCl(2).6H(2)O and 1a. The nu(CO) values from the IR spectra of 6a and 7a suggest that 1a resembles a phosphonite in its bonding to Rh and Ir. Crystal structures of meso-2a, meso-2b, rac-6a and 9 are reported and in each case a small intracage C-P-C angle of ca. 94 degrees is observed; this may partly explain the bonding characteristics of ligands 1a and 1b. The cone angles for 1a and 1b are similar and large (ca. 200 degrees). Rhodium complexes of ligands 1a and 1b are hydroformylation catalysts with similarly high activity to catalysts derived from phosphites. The catalysts derived from 1a and 1b gave unusually low linear selectivity in the hydroformylation of hexenes. This feature has been further exploited in quaternary-selective hydroformylations of unsaturated esters; catalysts derived from 1a give better yields and regioselectivities than any previously reported catalyst.