H. Barrera

Metal complexes of mercaptoamines—III. Different behaviour of β- and γ-(N,N-dimethyl)-mercaptoamines

Abstract The complexes Ni6(MPDMA)12, [Ni6(MPDMAH)12]X12 X = (I, ClO4) and Pd2(MPDMA)2Cl2 (MPDMA = t-S(CH2)3N(CH3)2) have been prepared and characterized. An X-ray diffraction study shows that the structure of [Ni6(MPDMAH)12] (ClO4)12 consists of a cyclic hexanuclear array of nickel atoms linked by sulphur bridging ligands. Infrared and electronic spectra show that there is no chelation in any of the nickel complexes. However, coordination through the nitrogen atoms occurs in the palladium complex. This behaviour differs from that of the homologous β-mercaptoamine, which forms monomeric chelate complexes with both nickel and palladium.

Synthesis and vibrational spectra of[RSHgII]2+(ClO4)2 complexes. Crystal and molecular structure of bis(N-methylpiperidinium-4-thiolato)-mercury(II) perchlorate.

Abstract Hg(II) complexes have been prepared with γ-mercaptoamine ligands 1-methyl-4-mercaptopiperidine (4-MP), 1-methyl-3(mercaptomethyl)piperidine (3-MMP) and 1-methyl-2(2-mercaptoethyl)piperidine (2-MEP) with 1:1 and 1:2 metal to ligand ratios. Infrared and Raman spectra for all these compounds have been recorded and discussed. The spectral features agree with a linear SHgS structure and with the characteristic two-coordination of mercury in all the complexes. The structure of [Hg(4-MP)2](ClO4)2 has been determined by X-ray crystallography. The crystals are orthorhombic, space group C2221 (Z=4) in a unit cell of dimensions a= 13.161 (3) A, b= 6.589 (2) A and c= 24.740 (4) A. Solution of the structure by direct methods led to a final weighted R factor of 0.057 for 1339 independent reflections. The crystal structure consists of discrete [Hg(4-MP)2]2+ cations and ClO4− anions packed in layers paralell to the (100) plane.

Metal complexes of mercaptoamines—I. Synthesis and crystal and molecular structure of tetrakis (3-amino-1-propanethiolato) trinickel(II)chloride

Abstract The reaction of nickel(II)chloride with γ-mercapto-propylamine in ethanolic solution gives the complex [Ni 3 (MPA) 4 ]Cl 2 (MPA=NH 2 -(CH 2 ) 3 -S). The complexes [Ni 3 (MPA) 4 ]X 2 (X=Br, I, ClO 4 ) can be synthesized from the chloride complex by addition of the sodium salt in aqueous solution. The crystal structure consists of discrete divalent trinuclear cations and chloride anions. Each sulphur atom of the ligand acts as a bridge between two nickel atoms, and the nitrogen atoms complete the coordination around the terminal nickel atoms. The geometry around the metal atoms is square-planar. The electronic and IR spectra of the complexes [Ni 3 (MPA) 4 ]X 2 (X=Br, I, ClO 4 ) indicate that all these compounds are composed of the [Ni 3 (MPA) 4 ] 2+ and X − ions.

Synthesis, crystal structure, and spectroscopic characterization of af-dichloro-bd,ec-bis{μ[2-(1-methyl-2-piperidinyl)ethanethiolato]-S,N,μ-S} dipalladium(II)

Abstract The reaction of 2-(1-methyl-2-piperidinyl)ethanethiol with sodium tetrachloro-palladate(II) at pH = 8 yields a yellow precipitate of formula [Pd2(C8H16NS)2Cl2] which crystallized in the orthorhombic space group Pcab with a = 22.050(4) A, b = 14.644(3) A, c = 13.834(3) A, V = 4467(3) A3, and Z = 8. The organic ligands chelate to one Pd atom through the S and N atoms and bridges to another Pd atom through the S atom to form a dimer in which each molecule of the organic ligand has the same chirality. IR, UV—Vis and 1H NMR spectra are presented for this compound.

Macroscopic and microscopic ionization constants of the thiol and amine groups in 1-methyl-4-mercaptopiperidine

The acid dissociation constants of 1-methyl-4-mercaptopiperidine (pK(1) = 9.51, pK(2) = 11.33), the 1,1-dimethyl-4-mercaptopiperidinium ion (pK(A) = 9.59) and 1-methyl-4-(methylthio)piperidine (pK(B) = 10.18) have been determined potentiometrically in 3M sodium perchlorate (10% methanol) medium. The ultraviolet absorption of the mercaptide ion has been used to determine the relative proton affinity of the sulphur and nitrogen functions in 1-methyl-4-mercaptopiperidine under the same conditions, and its four microscopic constants (pK(a) = 9.49, pK(b) = 10.23, pK(c) = 11.34, pK(d) = 10.60) have been calculated; pK(A) has also been determined spectrophotometrically. From the results obtained, it can be concluded that the thiol group is more acidic than the amine group and that the Adams relation, K(a) + K(b) = K(1), holds very well when it is assumed that the spectrophotometric values for K(a), and K(b), can be replaced by K(A) and K(B) respectively.

Transition metal complexes of γ-mercaptoalkylpiperidines

SummaryComplexes with 1-methyl-3-(mercaptomethyl)piperidine (LH) and 1-methyl-2-(2-mercaptoethyl)piperidine (L′H) Ligands in their thiolato (R), andN-protonated (HR) orN-methylated (MeR) zwitterionic form, of stoichiometry MR2 (M=Ni, R=L or L′; M=Cd, R=L), MR (M=Cu or Ag, R=L and L′), [Ni(MeR)2]I2 · nH2O (R=L, n=1; R=L′, n=2), [Ni(HR)2]X2 (R=L or L′, X=ClO4; R=L′, X=Br), and [Ag(HR)] ClO4 (R=L′) have been prepared and characterized. According to i.r. and electronic spectra, and magnetic measurements the nickel complexes exhibit polymeric frameworks built up from mercapto-bridged metal atoms in square-planar environments. Complexes with copper, silver, and cadmium exhibit similar polymeric arrangements through bridging sulphur atoms but with a different geometry at the metal centers, the first two being mainly linear, as anticipated, and the latter tetrahedral. In no case does coordinationvia nitrogen take place and therefore these ligands behave simply as mercaptides.

Cobalt(III) complexes with aminothiolates

SummaryThis article describes some complexes of cobalt(III) with γ-mercaptopropylamine,N, N-dimethyl-γ-mercaptopropylamme andN,N-dimethyl-β-mercaptoethylamine. The compounds are of stoichiometry [Co(ligand)3], [Co3(ligand)6]X (X=Cl or Br) and [Co(ligand)3]X3 (X=Cl or ClO4). γ-Mercaptopropylamine yields both chelated and non-chelated compounds while theN,N-dimethyl derivatives yield only non-chelated complexes. This behaviour contrasts with the results obtained with nickel(II).

Transition metal complexes with 1-methyl-4,4-dimercaptopiperidine

Abstract The syntheses of Co(AH 2 ) 2 X 2 (AH 2 = 1-methyl-4, 4-dimercaptopiperidine, X = Cl Br, I, acetate, propanate, perchlorate, nitrate and sulphate), M(AH 2 ) Cl 2 (M = Cd, Zn) are described. According to IR and UV-visible data it seems most probable that the amino gem -dithiol (AH 2 ) coordinates Co via both sulphur atoms, but Zn and Cd via one sulphur. A square pyramidal geometry about Co and a tetrahedral geometry about Zn and Cd are proposed. In no case has coordination via nitrogen been found. Strong X-H…N hydrogen bonds have been observed in most of these complexes.

Reaction of carbon disulphide with bis(γ-mercaptopropylamine) nickel(II)

SummaryCarbon disulphide reacts with bis(γ-mercaptopropylamine)nickel(II) by insertion into the Ni-N bond to yield a planar dithiocarbamate complex, in which the Ni-S bond is broken and a sulphydryl group is formed.

Halometallates of 1-methyl-4,4-dimercapto-piperidinium. Evidence of strong hydrogen bonds with participating thiol groups

Abstract Chlorometallates of transition and B subgroup elements are readily prepared and precipitated by reaction of the corresponding metallic salts with 1-methyl-4,4-dimercaptopiperidinium chloride. These chlorometallates investigated were [ZnCl 4 ] 2− , [CdCl 3 ] − , [CoCl 4 ] 2− , [CuCl 5 ] 3− and [FeCl 4 ] 2− . Strong SH … Cl interactions, but not NH … Cl, have been evidenced by IR spectroscopy in the zinc, cadmium and cobalt complexes. The SH and NH absorptions are observed at ≅ 2480 cm −1 and 3060 cm −1 , respectively. Partial deuteration of the [ZnCl 4 ] 2− complex with d 1 -methanol, shifted these IR signals to 1800 and 2260 cm −1 , clearly evidencing a X-hydrogen type of bond. The SH … Cl interaction is smaller in the [FeCl 4 ] 2− complex, and practically nonexistent in the [CuCl 5 3− complex.