J.C. Bayón

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.

Complexes of 1-methyl-4-mercaptopiperidine with zinc(II), cadmium(II) and mercury(II) halides

The preparation of a series of complexes formed by 1-methyl-4-mercaptopiperidine (AH) and divalent zinc, cadmium and mercury halides is reported together with some spectral and physical properties. The results of a crystallographic study allows to establish the structure of those of formula [M2(AH)2X4]H2O (M = Zn, Cd, Hg; X = Br, I) consisting of dimers and involving tetrahedral environment with sulphur-bridges for the metal atoms. Polymeric structures are proposed for the complexes of formulae Cd(AH)Cl2 and Hg2Cl4(AH).

Complexes of tetracyanobiimidazole.4.dimers of Cu(I)

Abstract In this paper we described dimeric complexes of Cu(I) with 4,4′,5,5′-tetracyano-2,2′-biimidazole (H2Tcbiim). These compounds contain the dianion (Tcbiim2−) acting as a quadridentate bridge betwee Cu(I) ions in combinations with phosphine, phosphite, pyridine, and quinuclidine ligands. Syntheses and interconversions among these species are recorded. The structure of Cu2[P(OPh)3]2(Py)2Tcbiim Py was determined by X-ray crystallography. The composition Cu2P2O6C61N11H45 crystallizes in the P 1 triclinic space group with a = 10.456(3) A, b = 15.060(5) A, c = 10.438(2) A, α = 94.89(2), β = 115.93(2), γ = 72.76(2) and Z = 1 molecule per cell. A final agreement of R = 0.035, Rw = 0.042 was obtained for 2743 observed reflections. The dimeric molecule has an inversion center between the 2,2′ carbon atoms of Tcbiim2−. Each Cu atom is tetrahedrally coordinated with angles ranging from 101°–126°. As a result of steric crowding by the phenyl rings of P(OPh)3 the copper atoms are somewhat sequestered. The influence of the stric and electronic factors can be seen in the oxidation potentials obtained from cyclic voltammetry. The potentials for the successive one electron oxidation of the dimers vary greatly with the donor strength of the ligands.

Synthesis, reactivity and catalytic properties of rhodium complexes of (R,R)-1-benzyl-3,4-dithioetherpyrrolidines

Abstract Complexes [Rh(cod)(degusR)]ClO4, where cod is 1,5-cyclooctadiene and degusR represents the homochiral dithioethers (R,R)-1-benzyl-3,4-bis(methylsulfanyl)pyrrolidine, (R,R)-1-benzyl-3,4-bis(isopropylsulfanyl)pyrrolidine and (R,R)-1-benzyl-3,4-bis(phenylsulfanyl)pyrrolidine were prepared and characterized. Their reactivity with CO and PPh3 was investigated. The complexes were assayed as catalysts in hydroformylation of styrene, hydrogenation of acrylic acids and hydroboration of styrene. Although these complexes containing dithioethers behave as catalytic precursors in hydroformylation reaction, the results suggest that mononuclear hydride rhodium carbonyl species is responsible for the catalytic activity. The cationic complexes are not active in the hydrogenation of acrylic acids in the conditions tested. These complexes are moderately active in the hydroboration of styrene with catecholborane, but their selectivities are not satisfactory.

Polymeric thiolate complexes in solution. Stability constants of the zinc(II) complexes of 1-methyl-4-mercaptopiperidine

The equilibrium reaction between ZnII and 1-methyl-4-mercaptopiperidine has been studied by e.m.f. measurements with a glass electrode at 25 °C in a 3 mol dm–3(sodium) perchlorate medium [+10%(v/v) CH3OH]. Conclusions drawn from graphical methods based on the ‘core + links’ hypothesis are in agreement with the results obtained from the numerical treatment. The e.m.f. data obtained in the range 4 < –log[H+] < 9 can be explained by assuming the existence of the following species: [Zn3(HA)6]6+(log ψ3, 6= 39.71 ± 0.01), [Zn5(HA)12]10+(log ψ5,12= 79.87 ± 0.01), and [Zn2(HA)6]4+(log ψ2,6= 35.26 ± 0.02) where HA is the uncharged ligand. A mechanism for the formation of these species and their possible geometries are suggested.

Complexes of tetracynobiimidazole. 3. Platinum and palladium species

Abstract In this paper we describe monomeric complexes of Pd(II) and Pt(II) with 4,4′,5,5′-tetracyano-2,2′-biimidazole (H 2 Tcbiim). These compounds always contain the dianion (Tcbiim = ) in accord with the greater acidity expected for the cyanosubstituted ring system. The structure of [N(Bu) 4 ] 2 [Pt(CN) 2 Tcbiim)] was determined by x-ray crystallography. The composition PtC 44 H 72 N 12 crystallizes in the P 1 triclinic space group with a = 16.664(3) A, b = 12.422(4) A, c = 13.842(4) A, α = 112.47(2), β = 111.01(2), γ = 89.40(2) and Z = 2 molecules/cell. A final agreement or R = 0.038 was obtained for 5359 observed reflections. The structure confirms planar bidentate chelation by Tcbiimu = and an irregular square planar coordination for the platinum atom. The preparation of a series of salts M[Pt(CN) 2 (Tcbiim)], M = NBu 4 + , NH 4 + , Ba 2+ and for K + both the platinum and palladium analogs, are described. The neutral molecule Pt(COD)Tcbiim was also prepared. Activity of these species under oxidation conditions are discussed in relation to the pi accepting properties of the title ligand.

Isostructuralism in double complex salts series: [M(H2O)x(NH3)6−x] [M′(CN)6] and [M(H2O)x(NH3)6−x] [CuCl5] (M, M′ = Co(III), Cr(III); x = 0, 1, 2). Crystal structure of [Cr(H2O)(NH3)5] [CuCl5]

Isostructuralism in two series of double complex salts [M(H2O)x(NH3)6−x] [M′(CN)6] (M, M′= Co(III), Cr(III); x = 0, 1, 2) and [M(H2O)x- (NH3)6−x] [CuCl5] (M = Co(III), Cr(III); x = 0, 1, 2) is reported by the use of X-ray powder diffraction methods. Compounds from the first series belong to the space group R 3, while those from the second belong to the Fd3c group. The crystal structure of [Cr(H2O)(NH3)5] [CuCl5], solved by single crystal X-ray diffraction methods, is cubic, space group Fd3c, with a = 22.208(3) A, V = 10952 A3, Z = 32, Dx = 1.92 g cm−1, μ = 9.57 cm−1, F(000) = 6336, Mw = 395.98. Disorder of the water molecule of the [Cr(H2O)(NH3)5]3+ cation among the six coordination sites of the octahedrally coordinated Cr(III) ion was found. A possible explanation of the isomorphism between the compounds within each series is proposed.

Dicyanoimidazole complexes of Cu(I): a carbonyl assisted alcoholysis of nitrile

We describe a series of compounds which result from the reaction of Cu(1) with 4,5dicyanoimidazole. This ligand is far more acidic than imidazole and in all cases forms complexes as the anion. The presence of carbon monoxide with Cu(I) assists in the rapid alcoholysis of one of the nitrile groups. The resulting imino-ester remains coordinated to the copper in the phosphine derivative as confirmed by X-ray crystallography. The composition CUC~~H~~N4Pz crystallizes in the space group Pbca with a = 14.140(4), b = 21.466(7), c = 24.577(8) a and Z = 8 molecules per cell. The copper is four coordinate and the bidentate imino-ester imidazole is nearly planar.

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.