Ahmed M. El-Hendawy

Schiff base complexes of ruthenium(III), molybdenum(VI) and uranium(VI), and use of the former as catalytic organic oxidants

Abstract The new complexes [RuIIIX2(AsPh3)2(HL)] (X  Cl, Br; HL  monoanions of Schiff bases formed from condensation of 2,3-dihydroxybenzaldehyde and aniline or its o- and p-substituted derivatives), cis-[MoO2(HL)2] and trans-[UO2(HL)2 · nH2O] (n = 0 or 2) have been isolated. They were characterized by spectroscopic techniques and investigated by cyclic voltammetry. The ruthenium(III) complexes were found to be effective catalysts for oxidation of primary alcohols to aldehydes, secondary alcohols to ketones and 3,5-di(tert-butyl)catechol to the corresponding o-benzoquinone in the presence of N-methyl-morpholine-N-oxide as co-oxidant.

Complexes of ruthenium(III) derived from O,O-donor ligands

Abstract The complexes [Ru, III Cl 2 (PPh 3 ) 2 L] (L = monoanions of maltol, kojic acid, tropolone and acetylacetone) were prepared and characterized by spectroscopic and electrochemical measurements. The catalytic oxidation of alcohols in the presence of excess N-methylmorpholine-N-oxide by [Ru III Cl 2 (PPh 3 ) 2 (acac)] has also been reported.

Complexes of lawsone with uranium, molybdenum, ruthenium and osmium, and their use as organic oxidants

Abstract The new complexes trans-[UO2(NQ)2], cis-[MoO2(NQ)2] and [MIII Cl2(EPh3)2 NQ] (M = Ru, E = As; M = Os,E = P; HNQ = lawsone, 2-hydroxyl-1,4-naphthoquinone) have been prepared. They were characterized by spectroscopic techniques and investigated by cyclic voltammetry. The complex [RuCl2(AsPh3)2NQ] was found to be a more efficient catalyst than that of the osmium complex for the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones in the presence of N-methylmorpholine-N-oxide as co-oxidant.

Complexes of naphthalene-2,3-diol (H2ND) with group VI and group VIII metals, and the X-ray crystal structure of cis-(NH4)2[Mo2O5(ND)2]·2H2O

Abstract The new naphthalene-2,3-diolato (2 — ) (ND) complexes cis-[M2O5(ND)2]2−, cis-[MO2(ND)2]2− (M = Mo, W), trans-UO2(ND)·3H2O, trans-[OsO2(ND)2]2− and cis-M′(PPh3)2(ND) (M′= Pd, Pt) have been isolated. The X-ray crystal structure of cis-(NH4)2[MO2O5(ND)2]·2H2O has been determined. The crystals are orthorhombic, space group Pbca, a = 9.084(4), b = 13.625(4), c = 39.512(18) A, Z = 8, R = 0.041 from 2554 observed reflections. The naphthalene-2,3-diolato ligands function as bidentate bridges, one oxygen atom of each spanning two cis-MoO2 units while the other lies trans to a symmetric MoOMo bridge. The two naphthalene units are splayed by ca 18° and sheared by ca 24° with respect to each other. Raman, IR, 1H and 13C NMR spectra of the complexes have been recorded.

Studies on transition-metal oxo and nitrido complexes. Part 9. Periodato and tellurato oxo-ruthenium complexes as organic oxidants. X-Ray crystal structure of trans-NaK5[RuO2(HIO6)2]·8H2O

Salts of the anion trans-[RuO2(HIO6)2]6–, earlier formulated as [Ru(OH)2(IO6)2]6–, and of [RuO2(H2TeO6)2]6– have been prepared, and the X-ray crystal structure of the complex trans-NaK5[RuO2(HIO6)2]·8H2O determined [monoclinic, space group C2/c, a= 26.869(14), b= 7.359(2), c= 11.471(3)A, β= 94.47(3)°, Z= 4, R= 0.059]. Vibrational and electronic spectra for these diamagnetic ‘ruthenyl’ complexes are also reported. The periodato complexes function as overall six-electron oxidants in aqueous solution, converting primary alcohols to carboxylic acids and secondary alcohols to ketones; such reactions can be rendered catalytic if periodate is used as a co-oxidant. The tellurato complex functions as a two-electron oxidant for alcohols.

Studies on transition–metal oxo and nitrido complexes. Part 10. New oxo–ruthenium and oxo–osmium pyridine complexes, and use of the former as catalysts for oxidation of alcohols

The new complexes trans-[RuO2(py)4]2+, trans-[OsO2(py)3(H2O)]2+, trans-[MO2(py)2X2](M = Ru or Os; X = Cl or Br, py = pyridine) and trans-[Ru2O6(py)4] are reported. Both trans-[RuO2(py)4]2+ and trans-[Ru2O6(py)4] in CH2Cl2 are efficient oxidants for primary alcohols to aldehydes and secondary alcohols to ketones, and function catalytically, with N-methylmorpholine N-oxide (mmo) or [NBun4][IO4] as co-oxidants. A simple preparation of trans-[Ru(py)4Cl2] and the isolation of [OsO4·L], [OsO2L2(O2C2H4)], and [OsO2L2(O2C6H10)](L = pyridine N-oxide) are also reported. Complexes were characterised by Raman, i.r. and 1H n.m.r. spectroscopy.

Antineoplastic Activity of New Transition Metal Complexes of 6-Methylpyridine-2-carbaldehyde-N(4)-ethylthiosemicarbazone: X-Ray Crystal Structures of [VO(2)(mpETSC)] and [Pt(mpETSC)Cl].

New complexes of dioxovanadium(V), zinc(II), ruthenium(II), palladium(II), and platinum(II) with 6-methylpyridine-2-carbaldehyde-N(4)-ethylthiosemicarbazone (HmpETSC) have been synthesized. The composition of these complexes is discussed on the basis of elemental analyses, IR, Raman, NMR (1H, 13C, and 31P), and electronic spectral data. The X-ray crystal structures of [VO2(mpETSC)] and [Pt(mpETSC)Cl] are also reported. The HmpETSC and its [Zn(HmpETSC)Cl2] and [Pd(mpETSC)Cl] complexes exhibit antineoplastic activity against colon cancer human cell lines (HCT 116).

Tetraphenylphosphonium perosmate(VII) as an oxidant: comparison of [OsO4]− with [RuO4]−

SummaryThe osmium(VII) salt (Ph4P)[OsO4] functions as a stoichiometric oxidant for benzylic and allylic alcohols, oxidising primary alcohols to aldehydes and secondary alcohols to ketones. Its vibrational spectra and cyclic voltammetric behaviour are compared with those of the perruthenate ion, [RuO4]−.

Complexes of ruthenium(II) and (III) derived from O,N-donor ligands, and their efficiency as catalytic oxidants for alcohols

Abstract The new complexes [RuIICl2(PPh3)2L] (L = benzoic hydrazide, bhz; substituted derivatives, R-bhz; R =p-Cl,p-CH3,o-NH2 and phenylacetic hydrazide) and [RuIIIX2 (AsPh3)2L′] (L′ = monoanions of 8-hydroxyquinoline, 8-hq;o-aminophenol; 2-amino-3- hydroxypyridine; X = Cl or Br) have been isolated. They were characterized by spectroscopic techniques and their redox behaviour was studied by cyclic voltammetry. The ruthenium(III) complexes were found to be more effective catalysts than those of ruthenium(II) for the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones in the presence of N-methylmorpholine-N-oxide as co-oxidant. Turnovers reached 400 with the catalyst [RuIIICl2(AsPh3)2(8-hq)].

Osmium(III)o-semiquinonato complexes and their use as catalysts for the oxidation of alcohols

Abstract The new complexes [Os 111 Cl 2 (PPh 3 ) 2 SQ′] (SQ′ = o -semiquinone; 1,2-benzosemiquinone (SQ), 4-methyl-1,2-benzosemiquinone, 3,5-di(tert-butyl)-l,2-benzosemiquinone, tetrachloro(tetrabromo)-l,2-benzosemiquinone and 2,3-naphthosemiquinone) have been isolated. They were characterised by spectroscopic techniques and investigated by cyclic voltammetry. The complex [OsCl 2 (PPh 3 ) 2 SQ] was found to be more efficient than the reported [Os 111 Cl 2 (PPh 3 ) 2 acac] as a catalyst for the oxidation of primary alcohols to aldehydes and of secondary alcohols to ketones in the presence of N -methylmorpholine- N -oxide as co-oxidant.