Elliott L. Blinn

THE REACTIVITY OF THE COORDINATED MERCAPTO GROUP WITH VARIOUS METAL IONS

Abstract The reactions of tris(2-mercaptoethylamine)cobalt(III), Col3, with cadmium(II), copper(II) and zinc(II) has resulted in the isolation of [Cd(CoL3)2]CdBr4,[Zn(CoL3)2]ZnBr4 and[Cu(CoL3)2]Br·2CuBr.These complexes have been characterized by chemical analyses, electronic and infrared spectra and conductivity measurements. The metal ions, Cd, Zn, Cu are believed to be coordinated by one CoL3 ligand and a bridging bromide. The reactions oftris(2-mercaptoethylamine)cobalt(III) with potential reducing metal ions such as Fe+2 or VO+2 and oxidizing metal ions such as Cr(H2O)+36, UO+42, andCe+4 has resulted in the isolation of salts of Co(CoL3)+32. Possible mechanisms which will result in the formation of the Co(CoL3)+32 cation are discussed.

Oxovanadium(IV) complexes containing bidentate nitrogen-sulfur and oxygen-sulfur ligands☆

Abstract A number of oxovanadium(IV) complexes containing nitrogen-sulfur and oxygen-sulfur bidentate ligands have been synthesized. The ligands employed include 2-aminoethanethiol, N-n-decyl-2-aminoethanethiol o-aminobenzenethiol, and 2-mercaptopyridine N-oxide. All the resulting oxovanadium(IV) complexes have the formula VOL2, where L is the bidentate ligand. At tempst to prepare the N,N,-dialkyl-2-aminoethanethiol complexes of oxovanadium(IV) resulted in failure. Pyridine adducts of bis(2-mercaptopyridine N-oxide) oxovanadium(IV) (VO(PTO)2Py) and the pyridine adduct of bis(o-aminobenethiolo)oxovanadium(IV) (VO-(ABT)2Py) have also been prepared. The stereochemistry of these complexese has been interpreted using chemical analyses and infrared and visible spectral data and all of these complexes appear to have square pyramidal geometries except bis(2-mercaptopyridine N-oxide)oxovanadium(IV). An attempt was made to correlate the specific Lewis base acceptor and infrared spectra. It was found that the reaction of VO(ABT)2Py with a variety of 4-substituted pyridine N-oxides (pyno) resulted in a systematic change in the visible spectra, and these changes were correlated to the Hammett σpyno values.

Molybdenum and tungsten complexes with metallo-ligands having sulfur donor atoms

Abstract The reaction of Mo(CO)6 with 2,3-pentanedione- bis(β-mercaptoethylimino)nickel(II), Nipe, under mild conditions, results in the formation of NipeMo(CO)4, while more forcing conditions give a different product, [NipeMo(CO)3]2. From an analogous reaction, a tungsten compound of the latter formula was also isolated. The chromium analogue was prepared in a similar manner but lacked the purity necessary to give good analyses. The molybdenum and tungsten complexes were characterized by chemical analyses and solution molecular weight. The magnetic moments of these complexes are anomalous, 2.3–2.4 BM, and suggest that the coordination number of the nickel is greater than four. Electronic spectra support this hypothesis. Cyclic voltammetry data indicate that the M(CO)3 moiety withdraws electron density from the nickel ion in the metallo-ligand. Reactions of Mo(CO)6 and W(CO)6 with bis(2-mercaptoethylamine)nickel(II) (Ni(MEA)2) gave the complexes Ni(MEA)2M2(CO)10 (M = Mo, W) which were characterized by analyses and infrared and electronic spectra.

A comparison of the affinity of metal ions for the ligand bis(β-mercaptoethylamine)nickel(II)

Abstract The affinities of cadmium(II) and nickel(II) for a coordinated mercapto group were compared by investigating the equilibria between Cd +2 or Ni +2 ( M ), Ni L 2 ( L = β -mercaptoethylamine) and the trinuclear complex [ M (Ni L 2 ) 2 ] +2 . Radiotracers were used to study the equilibria. It was found that the coordinated mercapto group has a greater affinity for the “soft” cadmium(II) than the harder nickel (II). This indicates that the hardness or softness of the central ion takes precedence over crystal field stabilization energy considerations when predicting the stability of these trinuclear complexes.

The effect of NNS type ligands on the stereochemistry and electronic properties of nickel(II) complexes

A series of complexes of the general stoichiometry of (NiLX)n have been prepared where L is NH2(CH2)nNH(CH2)2S and n is 2, 3, 4 and X is chloride or B(C6H5)4. All the complexes in which the anion is a chloride are diamagnetic, while the B(C6H5)4 complexes have magnetic moments varying from 1.07 BM to 1.29 BM. These complexes containing the tetraphenylborate counteranion adhere to the Curie-Weiss law from 300 K77 K. In solution most of these complexes appear to be dimers. However, in the solid from the NiLB(C6H5)4 complexes appear to be more polymeric. Based on spectral and magnetic data these complexes appear to have both square planar diamagnetic sites and paramagnetic sites in which the nickel(II) has a coordination number greater than four.

The reduction of carbon dioxide employing 1,4,7,10-tetramethyl-1,4,7,10 tetraazacyclododecane nickel(II) as a electron relay catalyst

Photolysis of a mixture of [Ni(Me4[12]aneN4)(H2O)]2+, [Ru(bipy)3]2+, ascorbate and carbon dioxide resulted in the formation of carbon monoxide, hydrogen and formic acid. The electrolysis of [Ni(Me4[12]aneN4)(H2O)]2+, in the presence of carbon dioxide and various electrolytes resulted in the formation of formic acid. More formic acid was formed in the presence of sodium perchlorate than sodium chloride. [Ni(Me4[12]aneN4)(H2O)]2+, preferentially reduces carbon dioxide versus a proton in aqueous solution regardless whether this nickel(I) complex is generated electrochemically or photochemically. This photo or electro generated nickel(I) complex also interacts strongly with CO and ascorbate but not with a proton above the pH of 4.

Nickel(II) complexes bonded to 12-membered macrocyclic ligands

Abstract Information has been obtained on how ring size, steric factors and the mode of coordination of tetraaza macrocycles will affect the field strength of the macrocycle and how these parameters affect the equilibrium in water or in a water-ethanol mixture between the five-coordinate nickel(II) complexes containing the macrocycle, R 4 [12]aneN 4 , where R is CH 3 and CH 2 C 6 H 5 , and the planar [Ni(R 4 [12]aneN 4 )] 2+ species. On the basis of spectral data it is concluded that steric factors influence the ligand field strength more than the size of the macrocycle for macrocycles that do not bond in a planar manner to the nickel(II). However, for square planar complexes both the size of the macrocyclic ligand and the steric factors play significant roles in the ligand field strength. The equilibrium between the high spin, five-coordinate, [Ni(R 4 [12]aneN 4 )H 2 O] 2+ complexes and the planar or nearly planar [Ni(R 4 [12]aneN 4 )] 2+ is dominated by the solvation properties of these complexes. The more carbon atoms on the R group, the larger the K , ΔS and ΔH values for the above equilibrium. In the presence of excess chloride ions, [Ni(Me 4 [12]aneN 4 )H 2 O] 2+ is converted to [Ni(Me 4 [12]aneN 4 )Cl] + . By increasing the percentage of ethanol in an ethanol-water mixture of [Ni(Me 4 [12]aneN 4 )Cl 2 , the equilibrium shifts to produce more [Ni(Me 4 [12]aneN 4 )Cl] + and less [Ni(Me 4 [12]aneN 4 )H 2 O] 2+ . The tetrabenzyl[12]aneN 4 nickel(II) complex is more difficult to oxidize and easier to reduce than the tetramethyl[12]aneN 4 nickel(II) complexes and the chloride complexes are easier to oxidize than the nitrate complexes in CH 3 CN. In water and in ethanol-water mixtures the [Ni(Me 4 [12]aneN 4 )H 2 O] 2+ /[Ni(Me 4 [12]aneN 4 )H 2 O] + couple is quasi-reversible but in CH 3 CN only the cathodic reaction is observed.

The Reactions of Silver(I) With Tetraaza Macrocyclic Ligands

Abstract The reactions of silver(I) with 1,4,7,11-tetraazacyclotetradecane (isocyclam), 1,4,8,1 l-tetraazacyclotetra-decane (cyclam) and 1,4,8,12-tetraazacyclopentadecane ([I5]aneN4) resulted in the production of silver and a silver(II) tetraaza macrocyclic complex, AgL2 + The mechanisms of these reactions involve the formation of AgLl+ which is oxidized by silver(I) to Ag and AgL2 +. However, the reaction of 1,4,7,10-tetraazacycIododecane ([12]aneN4) with silver(I) resulted in the formation of an unstable complex. Silver(I) did not react with 1,4,7,10-tetrabenzyl-1,4,7,10-tetraazacycIododecane. The most stable Ag(II) complex in aqueous solution with regards to decomposition contains the [15]aneN4 ligand, while the Ag(II) complex containing [12]aneN4 is the least stable. Attempts to oxidize benzyl alcohol to benzyl aldehyde using [Ag(cyclam)](ClO4)2 were unsuccessful.

Nickel(II) complexes of schiff bases derived from pyrrole-2-aldehyde and dipropylenetriamine

Abstract The preparation and physical and chemical properties of a variety of square planar nickel(II) complexes containing a Schiff base ligand derived from pyrrole-2-aldehyde and dipropylenetriamine are reported. This Schiff base ligands has five potential donor atoms. The general formula of these complexes is Ni(HBPTU)X, where X = Br−, B(C6H5)4−, PF6−, or SCN− and HBPTU represents the uninegative ligand of 1,11-bis(2-pyrrolyl)2,6,10-triaza-1, 10-undecadiene, H2BPTU. All these complexes have anomalous magnetic moments between 0·5 and 0·9 BM and appear to be polymeric in nitromethane and acetonitrile. In the solid state, HBPTU coordinates to the nickel(II) as a tetranitromehtan and acetonitrile. In the solid state, HBPTU coordinates to the nickel(II) as a tetradentate ligand, while in solution, the HBPTU functions as a tridentate ligand and contains a dangling imine and a pyrrole group. In solution, Ni(HBPTU)X self-associates by means of hydrogen bonding.

Metallo-ligands containing terminal oxygen donors bonded to a manganese–carbonyl moiety

The reactions of [Mn(CO)5Br] with [M(salen)][M = Co, Cu, Zn, Pd, Ni, or Sn; salen =N,N′-ethylenebis(salicylideneiminate)], [Co(salphen)][salphen =N,N′-o-phenylenebis(salicylideneiminate)], or [Co(salchd)][salchd =N,N′-cyclohexane-1,2-diylbis(salicylideneiminate)] in a variety of solvents resulted in the substitution products having the general formula [(ML)Mn(CO)3Br](L = salen, salphen, or salchd). The reaction of 4-ethyl-5-methyl-3,6-diazaocta-3,5-diene-1,8-dithiolatonickel(II), [NiL′], with [Mn(CO)5Br] resulted in the substitution product [(NiL′)Mn(CO)3Br]. These complexes were characterized by i.r. and electronic spectra and magnetic and cyclic voltammetry measurements. Chemical and physical data indicate that the metallo-ligand moieties of these bimetallic complexes bond weakly to the Mn(CO)3Br moiety.