M. Ramadan

Chromium, Molybdenum and Ruthenium Complexes of 2-Hydroxyacetophenone Schiff Bases

Interaction of the Schiff base 2-hydroxyacetophenonepropylimine (happramH) with M(CO)6, M=Cr or Mo under reduced pressure gave the dicarbonyl complex M(CO)2(happramH)2. The complex MoO(happram)2 was isolated from the reaction of Mo(CO)6 and happramH in air. Ru3(CO)12 and RuCl3 reacted with the Schiff base bis-(2-hydroxyacetophenone)ethylenediimine (hapenH2) to give Ru(CO)2(hapenH2) and [RuCl2(hapenH2)]Cl. Elemental, spectroscopic and magnetic studies of the reported complexes revealed the proposed structures. The thermal properties of the complexes were investigated by thermogravimetric techniques. Cyclic voltammetry of the complexes showed tautomeric redox processes due to ligand-based reduction and metal-based oxidation.

Reactions of Group 6 Metal Carbonyls with Salicylaldehyde Hydrazone

Abstract The interaction of salicylaldehyde hydrazone (shH) with Cr(CO)6 in the absence of oxygen resulted in the formation of the tris derivative Cr(sh)3, 1. Reactions of M(CO)6, M = Cr, Mo in air gave the oxo derivatives M(O)(sh)2, 2 and 3, with the metal atom in +4 formal oxidation state. Prolonged heating of a mixture of Mo(CO)6 and shH in air resulted in the formation of the dinuclear complex Mo2(O)6(shH), 4. Structures for the complexes were proposed based on the spectroscopic studies. Reactions of W(CO)6 with shH in air or under reduced pressure lead to the formation of the salicylaldehyde azine dimer via elimination of a hydrazine molecule. The structure of the dimer was confirmed by crystal structure determination and by FTIR and FT‐Raman spectroscopy.

REACTIONS OF CHROMIUM AND MOLYBDENUM CARBONYLS WITH A QUADRIDENTATE SCHIFF BASE

Abstract Interaction of a Schiff base derived from 2-hydroxyacetophenone and ethylenediamine (hapenH2) with M(CO)6, M = Cr and Mo, in THF under atmospheric pressure gave the oxo derivatives M(O) (hapen) with the metal atom in +4 formal oxidation state. IR spectra of the complexes revealed the presence of the M = O bond. The dihydride complex MoH2(CO) (hapen) was also isolated from the reaction of Mo(CO)6 and happen H2 under reduced pressure; v(CO) and v(Mo-H) frequencies were clearly indicated in its IR spectrum. The three complexes were found to be paramagnetic. Magnetic susceptibility measurements suggested that the d 4 Mo atom in MoH2 (CO) (hapen) exists in a low spin configuration. Electronic spectra of the ligand and its complexes in different donor solvents displayed bands due to compound-solvent, charge-transfer complexes.

Group VI Dinuclear Oxo Metal Complexes of Salicylideneimine‐2‐anisole Schiff Base

Interaction of the Schiff base salicylideneimine‐2‐anisole (salanH) with Cr(CO)6 yielded the dicarbonyl derivative Cr2O2(CO)2(salan)2. The dinuclear oxo complex M2O4(salan)2, M˭Mo and W, was isolated from the reaction of M(CO)6 with salanH. Elemental, spectroscopic and magnetic studies of the reported complexes allowed structures to be proposed. The thermal properties of the complexes were investigated by thermogravimetry.

Ruthenium, osmium and rhodium-2,3-bis(2¢-pyridyl)quinoxaline complexes

Ru3(CO)12 reacts with 2,3-bis (2′-pyridyl)quinoxaline (dpq) in benzene in the presence of either 2,2′(dipyridine (dpy) or pyridine (py) to give the mononuclear complexes Ru(CO)3(dpq) (1) and Ru(CO)2(dpq)(py) (2), respectively. On the other hand, reactions of Os3(CO)12 with dpq alone, or in the presence of dipyridine, yield only Os(CO)3(dpq) (3). Spectroscopic studies of the three complexes were consistent with the proposed structures. Reactions of RuCl3 with dpq, under reduced pressure in PhH/EtOH gave bis-[Ru(dpq)2Cl2]Cl (4). Magnetic measurements showed RuIII, d5, to be in a low-spin electronic configuration. Three complexes, Rh2(dpq)2Cl6(5), [Rh(dpq)2Cl2]Cl (6) and Rh(dpq)(py)Cl3(7), were isolated from reactions of RhCl3 with dpq. The type of product was dependent on the reactants and conditions. The complexes exhibit either irreversible or quasi-reversible ligand-based reductions. In addition, the zerovalent complexes (1)–(3) displayed one metal(based oxidation in their cyclic voltammograms, due to the formation of M+ species.

Reactions of chromium and molybdenum carbonyls with bis-(salicylaldehyde)ethylenediimine schiff-base ligand

Interaction of bis-(salicylaldehyde)ethylenediimine, salenH2, with M(CO)6 (M = Cr, Mo) in air gave M(O)(salen) complexes. Magnetic studies show that the metal exists in the +4 oxidation state. Cr(CO)6 reacted with salenH2 under reduced pressure to yield the dicarbonyl derivative Cr(CO)2(salenH2). Reactions of M(CO)6 with salenH2 in the presence of a secondary ligand L (L = H2O, pyridine) resulted in the formation of the square pyramidal complex M(L)(salenH2). UV-Vis spectra of the complexes exhibited visible bands due to metal-to-ligand charge transfer. Structures for the complexes are proposed on the basis of spectroscopic studies.

A novel structure arrangement of molybdenum dimethylglyoxime complexes. Compounds with MoON2C2 six-membered rings

Abstract Thermal reactions of Mo(CO)6 with dimethylglyoxime (H2DMG) in THF solutions, either in vacuum or under atmospheric pressure, gave three compounds with formulae Mo(H2DMG)3, I, Mo206(H2DMG)2, II and Mo204(CO)2(H2DMG)2 III. Spectroscopic studies of these complexes revealed that H2DMG is bonded to the molybdenum through the nitrogen atom of one oxime moiety and the oxygen of the other moiety. The hydrogen atom of the latter oxime was transferred to the nitrogen of the same group to form an NH group. 1H NMR studies of compounds II and III at various temperatures showed that the hydrogen atom of this NH group was rigid on the NMR time scale while the hydrogen atom of the other oxime was fluxional. A mechanism involving terminal-bridge CO and O exchange was proposed to explain the stereochemical nonrigidity of these complexes. Appearance of a resonance at about 7.1 ppm in the 1H NMR spectra of II and III due to a deshielded CH proton suggested some sort of aromaticity in these six membered chelates.

Spectroscopic and electrochemical activity studies of some molybdenum chrysenesemiquinone complexes

Abstract Five molybdenum complexes were isolated from the reactions of chrysenequinone and Mo(CO) 6 . All the isolated complexes were found to be dimeric and contained MoO bonds. The IR spectra of these complexes showed strong ν(CO) bands due to semiquinone type bonding. The vibrational spectrum of Mo 2 O 2 (CO) 4 (ChrySQ) 2 (ChrySQ = chrysenesemiquinone) also showed ν(CO) bonds due to terminal and bridged CO groups. Two complexes with stoichiometry of Mo 2 O 4 (CO) 2 (ChrySQ) 2 were found to be isomeric in cis and trans forms. The electronic absorption spectra of Mo 2 O 4 (CO) 2 (ChrySQ) 2 and Mo 2 O 2 (CO) 4 (ChrySQ) 2 in DMSO displayed bands due to the formation of molybdenum compound-solvent charge transfer complexes. The energies of the charge transfer complexes ( E CT ) were calculated either theoretically from the ionization potential of the donor and the electron affinity of the acceptor, or experimentally from the UV-vis spectra of the complexes. Examination of Mo 2 O 4 (CO) 2 (ChrySQ) 2 by cyclic voltammetry showed two quasi-reversible redox reactions due to tautomeric interconversions of the semiquinone-catechol couples through electron transfer.

Synthesis and spectroscopic studies of some new metal carbonyl derivatives of 1-(2-pyridylazo)-2-naphthol

Interaction of 1-(2-pyridylazo)-2-naphthol (PAN) with [Mo(CO)6] in air resulted in formation of the tricarbonyl oxo-complex [Mo(O)(CO)3(PAN)], 1. The dicarbonyl complex [Ru(CO)2(PAN)], 3, was obtained from the reaction of [Ru3(CO)12] with PAN. In presence of triphenyl phosphine (PPh3), the reaction of PAN with either Mo(CO)6 or Ru3(CO)12 gave [Mo(CO)3(PAN)(PPh3)], 2, and [Ru(CO)2(PAN)(PPh3)], 4. All the complexes were characterized by elemental analysis, mass spectrometry, IR, and NMR spectroscopy. The thermal properties of the complexes were also investigated by thermogravimetry.

Chromium, molybdenum and ruthenium complexes of chloranilic acid

Chloranilic acid (H2CA) reacts with Cr(CO)6 and CrCl3 to give the tris derivatives Cr(H2CA)3 and Cr(HCA)3. Spectroscopic measurements on the two complexes reveal that the ligand–metal bond is of the semiquinone type. Susceptibility determinations showed effective magnetic moments of 1.82 and 1.07 μB. Examination of Cr(H2CA)3 by cyclic voltammetry revealed two redox reactions due to tautomeric interconversion through electron transfer. Boiling Mo(CO)6 with H2CA in air gave MoO3(HCA) in which the molybdenum atom is in the + 5 oxidation state. The i.r. spectrum of the MoO3(HCA) displayed bands due to terminal M=O bonds. The cluster compound Ru3(CO)12 reacted with H2CA to give Ru3(CO)10(μ-H)(HCA), the i.r. spectrum of which revealed that the ligand is bound to the metal as a catechol moiety. The spectroscopic and magnetic studies of the molybdenum and ruthenium complexes confirmed the proposed structures.