J.G.M. van der Linden

Metal complexes with two different sulfur containing ligands. Electron transfer series of the [M-S′2S″2]Z-type

Abstract An electron transfer series of complexes of the [M-S′ 2 S″ 2 ] Z -type has been investigated, using maleonitrile dithiolate and N,N-di-n-butyldithiocarbamate as the ligands (M=Ni, Cu, and Au). Monoanionic (z= −1) M(mnt)(dtc) − with M=Ni, Cu, and neutral (z= 0) (M(mnt)(dtc) with M=Cu, Au complexes have been prepared. Voltammetric data show these complexes to exist as part of a two membered series z= 0 or −1, the members being convertible by reversible one electron steps. The E 1 2 values are intermediate between those for the complexes with unmixed ligands.

Metal complexes with two different sulfur containing ligands—II

Abstract The synthesis and characterization of a series of mixed 1,1-/1,2-dithiolene complexes, M [S 2 C 2 (CN) 2 ][S 2 CNR 2 ] z with z = −1, M = Ni, Cu, Pd, Pt and with z = 0, M = Ni, Cu, Au, M [S 2 C 2 (CN) 2 ][S 2 CNCN] 2− , M = Ni, Pd, and Ni[S 2 C 2 (CN) 2 ][S 2 COC 2 H 5 ] − are reported. Voltammetric studies in dichloromethane revealed that the mixed complexes could be oxidized in a one electron step, the half-wave potentials of which were generally in the middle between those for the unmixed complexes. The CN stretching frequencies observed in the i.r. spectra of the M [S 2 C 2 (CN) 2 ][S 2 CNR 2 ] z complexes are reported.

Stability constants of tin(II) and calcium diphosphonate complexes

Abstract Stoichiometric stability constants were determined for tin(II) and calcium species with six different diphosphonates in 0.1 M Me 4 NN0 3 -containing solutions. Several protonated; hydroxylated, mono- and binuclear metal complexes have been identified. The relative amounts of these species present in aqueous solutions are strongly influenced by the pH Diphosphonates were found to be able to stabilize supersaturated tin(II) hydroxide solutions. The order of the observed increasing stability of tin(II) disphosphonates MDP

Preparation and properties of monothio- and monoselenocarbamate Complexes of gold(I) and rhodium(I)

Abstract The complexes (C6H5)3)PAuL and ((C6H5)3P)2 Rh(CO)L (L =SC(O)NR2 and SeC(O)NR2) have been prepared. Infrared data reveal the monothio- and selenocarbamate complexes to be monodentate coordinated with the metal atom via the sulfur or selenium, respectively. The kinetic parameters of the hindered rotation around the bonds in the gold complexes have been determined from n.m.r. spectra. The values for the activation energies have the same order of magnitude as those found for other hindered rotation processes in dithiocarbamate complexes.

Preparation and electrochemical behaviour of tris dithiocarbamato complexes [Bu4N]M(Et2dtc)3 with M = Ba, Zn, Cd, and Hg

Abstract The compounds [Bu4N]M(R2dtc)3 (M = Ba, Zn, Cd and Hg; R = Me, Et) have been prepared. Conductivity measurements and an electrochemical oxidation study with pulse polarographic and cyclic voltammetric techniques show that in acetone solutions the barium tris anion, Ba(Et2dtc)−3, is completely dissociated into the bis complex, Ba(Et2dtc)2 and a ligand ion, Et2dtc−; the zinc and mercury tris anions are not completely dissociated and the cadmium anion only to a minor extent.

Electrochemical redox behaviour of dithiocarbamates and diselenocarbamates of nickel, palladium and platinum

Abstract An electrochemical study of M(dtc)2 complexes, M = Pd, Pt, established that these complexes can be reduced to the unstable M(dtc)−2 species and irreversibly oxidized to the tris complexes, M(dtc)+3, although in low yields. A detailed study of the redox behaviour of the platinum tris compound, Pt(dtc)+3, revealed that a two electron transfer process occurred, with a very rapid decomposition of the reduced species, according to Pt(dtc)+3 → Pt(dtc)−3 → Pt(dtc)2 + dtc− The electrochemical behaviour of the diseleno complexes, M(dsc)2 and electrochemically generated M(dsc)+3, M = Ni, Pd, Pt, closely parallels that of their dtc congeners.

STRUCTURE AND PROPERTIES OF N,N-DI-n-BUTYLDITHIOCARBAMATO-1, 2-DICYANOETHENE-1, 2-DITHIOLATO-GOLD(III)

Abstract The crystal and molecular structure and some spectral data of the compound N,N-di-n-butyldithiocarbamato-1, 2-dicyanoethene-1, 2-dithiolato-gold(III), AuS2CN(C4H9)2S2C2(CN)2, are reported. The crystal structure has been determined from a three-dimensional single-crystal X-ray diffraction study. The orthorombic cell, space group Pbca, with a=14.066(3), b=28.980(2) and c=9.192(2) A, contains eight formula units. Intensity data were collected on an automatic diffractometer. The structural parameters were refined by full-matrix least-squares methods to a conventional R-factor of 0.047 for 1587 independent non-zero reflections. The structure determination proved the compound to be a mixed dithiocarbamato-dithiolato complex, Au(dtc)(mnt), (dtc=N,N-di-n-butyl-dithiocarbamate, mnt=maleonitriledithiolate ≡ 1, 2-dicyanoethene-1, 2-dithiolate), as expected from spectral data. The gold atom is in approximately square-planar coordination, however, deviations from mm2 (C2#) symmetry are considerable. Au-S bond...

Two silicon-bridged cyclopentadienyl Fe2S4 cluster units connected through an Fe(III)S6 unit. Crystal and molecular structure of [((CH3)2SiCp′2)2Fe5(μ3-S2)2(μ4-S2)2(μ4-S4)]FeCl4

Abstract The reaction of (CH 3 ) 2 Si[Cp′Fe(CO) 2 ] 2 with elemental sulfur in refluxing toluene resulted in the formation of two new iron-sulfur cluster compounds. Prolonged crystallisation from CH 2 Cl 2 -hexane mixtures of one of these compounds resulted in crystals of the title compound. An X-ray diffraction study revealed that two (CH 3 ) 2 SiCp′ 2 Fe 2 units are connected to a central Fe(III) ion via four disulfido ligands and a tetrasulfido ligand. This iron atom is octahedrally coordinated by six sulfur atoms. Of the six Fe(III)S distances four are close to 2.30 A and the other two are about 2.20 A. In both the (Ch 3 ) 2 SiCp′ 2 Fe 2 units each iron atom is coordinated to three sulfur atoms and one Cp ring. This results in twelve FeS distances: six of them are in a narrow range from 2.165 to 2.184 A, whereas the other six vary from 2.240 to 2.286 A. The FeFe distances are 2.561 and 2.581 A. The SS distances range from 2.041 to 2.073 A. The FeCl distances in the FeCl 4 − ion, centred around 2.16 A, show the presence of Fe(III) in this ion.

Electrochemical investigation of the electron-poor/precise (n=5/6) complexes [Fe2(CO)n(μ-PR2)(μ-PR′2)] (n=5, RR′But; n=6, RR′Ph; RBut, R′Ph; RBut, R′Cy). EPR study of the radical anion [Fe2(μ-PBut2)2(CO)5]·.−

Abstract The redox behavior of the bis(phosphido)-bridged diiron carbonyl complexes [Fe 2 (CO) n (μ-PR 2 )(μ-PR′ 2 )] ( n =5, RR′Bu t ; n =6, RR′Ph; RBu t , R′Ph; RBu t , R′Cy) has been studied electrochemically at a platinum electrode in THF (0.1 M in Bu 4 N[PF 6 ]). The electron-poor complex ( n =5, RR′Bu t ) shows two well-defined reduction steps at −1.34 and −2.35 V assigned to the formation of the radical anion [Fe 2 (CO) 5 (μ- PBu t 2 )] .− and the dianion [Fe 2 (CO) 5 (μ-PBu t 2 ) 2 ] 2− . The uninegative radical ion has been further investigated by EPR spectroscopy. The fluid as well as the rigid solution spectra indicate that the two phosphido bridges are linking the two iron centers in the same manner and that the unpaired electron is metal centered. The electron- precise complexes ( n =6) are reduced at approximately the same potentials (−1.74 to −1.91 V) in two closely spaced one-electron steps. Molecular configurational changes accompany these reductions and make both processes, reduction and re-oxidation, quite slow.

A comparative electrochemical study of the iron-sulfur cluster series Fe4SxCp4 (x=4–6) in benzonitrile

Abstract The electrochemical redox behaviour of the compounds Fe 4 S x Cp 4 (x=4–6) has been investigated at a platinum electrode in benzonitrile solutions, using pulse polarographic and cyclic voltammetric techniques. In this solvent Fe 4 S 4 Cp 4 exhibits four reversible oxidation reactions, earlier noted in acetonitrile, and a thus far unknown irreversible reduction. Fe 4 S 5 Cp 4 shows two reductions one of which is reversible, and three reversible oxidations. Fe 4 S 6 Cp 4 shows a reversible reduction and two reversible oxidations, and also a third, previously undetected, irreversible one-electron oxidation. Thus far not reported detailed electrochemical data for these compounds (e.g. current functions and reversibility criteria) are measured under the same experimental conditions. In this way a detailed comparative study of the electrochemical properties of the Fe 4 S x Cp 4 compounds is possible. Some attention is paid to the nature of the decomposition products resulting from the irreversible transitions.