Wolfgang Dietzsch

In(III), Tl(III) and V(IV) tris-chelates of the heterocyclic dithiolene and diselenolene ligands 1,3-dithiole-2-thione-4,5-dithiolate (dmit), 1,2-dithiole-3-thione-4,5-dithiolate (dmt) and 1,3-diselenole-2-selone-4,5-diselenolate (dsis). Crystal and molecular structure of (Bu4N)2 [V(dmt)3]

Abstract Synthesis and characterization of the first trischelates of the dichalcogenolene ligands 1,3-dithiole-2-thione-4,5-dithiolate (dmit), 1,2-dithiole-3-thione-4,5-dithiolate (dmt)and 1,3-diselenole-2-selone-4,5-diselenolate (dsis) with the central ions In(III), Tl(III) and V(IV) are reported. On (Bu4N)2[V(dmt)3] the first X-ray structure of a dithiolene tris-chelate containing unsymmetric ligand was carried out: the compound crystallizes monoclinic, space group P21/c, with four molecules in the unit cell; a = 16.264(3), b = 17.319(4), c = 21.554(4) A, β = 103.03(2)°. The ligand dmt causes a very low symmetry of the VS6 moiety in [V(dmt)3]2− having pseudo-meridional arrangement of the three ligands. The EPR parameters of the compounds (Bu4N)2[V(dmit)3] and (Bu4N)2[V(dmt)3] measured in liquid and frozen acetonic solution are compared with those of the tris(maleonitriledithiolato)vanadate(IV) anion supporting a geometry of the anion being between octahedral and trigonal prismatic.

Thio-oxalates: their ligand properties and coordination chemistry

A. Introduction 43 B. Topology, syntheses and structures of non-coordinated thio-oxalates 44 C. Modes of ligation in thio-oxalate complexes 47 D. Systematics of thio-oxalate complexes 48 (i) Monothio-oxalate, [02C-COS]z-, mto 51 (ii) l,l-Dithio-oxalate, [02C-CS,]*-, i-dto 51 (iii) 1,2-Dithio-oxalate, [SOC-COS]‘-, dto 56 (a) Solid state structure characteristics of dto complexes 58 (b) Syntheses of dto complexes 71 (c) Magnetic properties; EPR and Miissbauer data 87 (d) Electronic spectra 93 (e) IR, Raman and resonance Raman spectra 96 (f) ESCA spectra 98 (g) Redox behaviour 101 (h) Photoand thermochemical behaviour 103 (i) Ligand exchange reactions and mixed ligand complexes 104 (j) Analytical use of dto complexes 109 (iv) Trithio-oxalate, [SOC--CSJz-, trto 109 (v) Tetrathio-oxalate, [S,C-CSJ-, tto 112 (a) Metal-promoted head-to-head dimerizations of CSI 114 (b) Dimethyl tetrathio-oxalate, ttoMe,, and dimethyl ethenetetrathiolate, etthle, complexes 116 (c) Authentic tetrathio-oxalate synthesis and complex behaviour 118 (d) Related ligand systems containing the CISb core 121 Acknowledgements 123 References 123

Synthesis of Stable Sources for 1,2-Diselenolate Dianion Chemistry : Bis (2-Selenoxo-1,3-Diselenole-4,5-diselenolato) zincate (II) and 4,5-Benzoylseleno-1,3-diselenole-2-selenone

Abstract The synthesis of 4,5-benzoylseleno-1,3-diselenole-2-selenone via bis (2-selenoxo-1,3-diselenole-4,5-di-selenolato) zincate (II) as a precursor for selenium ligands and selenium heterocycles is described.

Mixed-ligand complexes of technetium IX. Oxidative ligand exchange reactions on tetraphenylarsonium-bis(dithiooxalato)nitridotechnetate(V), (Ph4As)2[TcN(dto)2]. X-ray crystal structure of a further modification of (Ph4As)2[TcN(dto)2]

Abstract (Ph 4 As) 2 [TcN(dto) 2 ] can be prepared starting from TcNCl 4 − or TcNCl 2 (Ph 3 P) 2 . The compound crystallizes in at least two modifications: as well as a triclinic form (S. F. Colmanet and M. F. Mackay, Inorg. Chim. Acta, 147 (1988) 173) a monoclinic one has been found (space group C 2/ c , Z = 4, a = 19.424(3), b = 11.254(2), c = 24.958(3) A, β = 107.68(1)°; R = 0.048). Distances and angles in the complex anions in both modifications are almost identical within experimental error. Oxidation of [TcN(dto) 2 ] 2− by Cl 2 produces the Tc(VI) complex TcNCl 4 − exclusively, whereas during the Br 2 oxidation technetium(VI) intermediates are generated containing mixed Br/dto coordination spheres which can be monitored easily by EPR spectroscopy.

Ligand exchange reactions between copper(II)- and nickel(II)-chelates of different sulfur- and selenium-containing ligands. VI [1]. Kinetics of ligands exchange reactions studied by stopped-flow ESR

Abstract The kinetics of ligand exchange reactions studied by means of stopped-flow ESR measurements are reported. The concentrations-time curves recorded for all reactions investigated correspond ton simple second-order rate laws. The rate constants of the reactions between copper(II) dithiolenes and Cu(Et 2 dsc) 2 (Et 2 dsc = diethyldiselenocarbamate) or Ni(Et 2 -dsc) 2 were found to be: [Cu(mnt) 2 ] 2– (mnt = maleo-nitriledithiolate) + Cu(Et 2 dsc) 2 , k 2 = (2.3 ±0.3)· 10 2 1 mol −1 s −1 ; [Cu(mnt) 2 ] 2− + Ni(Et 2 dsc) 2 , k 2 = (2.1 ± 0.1)· 10 2 1 mol −1 s −1 and [Cu(dmit) 2 ] 2− (dmit = isotrithione-3.4-dithiolate) + Ni(Et 2 dsc) 2 , k 2 = (2.5 ± 0.3)· 10 2 1 mol −1 s −1 . A rate constant of k 2 = (2.0 ± 0.3)· 10. 2 1 mol −1 s −1 was determined for the reaction between (Cu(Et 2 dsc) 2 and Cu(Et 2 -dtc) 2 (Et 2 dtc = diethyldithiocarbamate). Additional experiments suggest a chain mechanism for the ligand exchange reactions in which the mono-chelates e.g. [Cu(mnt)] s react as active sites.

Trans-1,2-dithiooxalate as bridging ligand—II ☆: The X-ray crystal structure of μ-1,2-dithiooxalato-bis[bis(triphenylphosphine)silver(I)]

Abstract The X-ray structure of (Ph3P)2Ag(SOC2SO)Ag(PPh3)2 shows this complex as the second authentic example containing a bridging trans-1,2-dithiooxalate ligand. The compound crystallizes in the monoclinic space group P21/c with a=13.159(2), b=11.895(2), c=20.939(5)A, β= 101.35(2)° and Z = 2. The structure was solved by Patterson and Fourier methods for 5649 diffractometer data and refined to a final R value of 0.066 for 03545 observed reflections. The dimensions of the dithiooxalate bridge are compared with those of the corresponding trans-dithiooxalate in (Ph4As)4 (O2C2S2)2In(SOC2SO)In(S2C2O2)2]. Differences between structures containing bridging trans-dithiooxalate or bridging cis-dithiooxalate, respectively, are discussed.

EPR evidence for a new, important limiting resonance structure in the explanation of the bonding of spin-crossover Fe(III) dichalcogenocarbamates

Abstract In 1931 Cambi and co-workers found that the magnetic moments of some Fe(III) dithiocarbamate complexes were intermediate between that expected for an S = 5 2 and an S = 1 2 electronic configuration. The high-field (low spin) limited resonance structure has been modelled as an S = 1 2 configuration of the d 5 iron(III). Strong evidence is presented that, in some cases, the high field structure consists of an unpaired electron on a nitrogen atom, with this nitrogen atom having donated an electron to the iron(II). The observed powder EPR spectra for four different iron(III) dichalcogenocarbamates have been successfully simulated using the model of an electron ( S = 1 2 interacting with a nucleus of M I =1. This interpretation is further strengthened by the observation of a three-line spectrum in a similar crystalline sample.

Ligand exchange reactions between metal(II) chelates of different sulfur and selenium containing ligands IX. Exchange behavior of chelates of 1,3-Dithiole-2-thione-4,5-dithiolate (dmit) and 1,1-Dichalcogenolates. X-ray Structure of Bu4N[Zn(dmit)(Et2dtc)]

Abstract Nickel, copper and zinc bis-chelates of 1,3- dithiole-2-thione-4,5-dithiolate react with diethyldithio-, -thioseleno-, and diseleno-carbamates of these metals in acetone forming the mixed ligand complexes [M(dmit)(XYCNEt2)]− (X=Y=S or Se; X=S, Y=Se) exclusively which can be isolated purely as salts of suitable cations. This synthesis can be extended to mixed ligand systems containing other geminal ligands demonstrated by (Bu4N)2 [Ni(dmit)- (i-mnt)] (i-mnt=1,1-dicyanoethene-2,2-dithiolate). EPR measurements on the copper compounds and 1H, 13C and 77Se NMR measurements on the nickel and zinc systems as well show that the four- membered chelate ring gains electron density in disfavor of the five-membered chelate ring during the mixed ligand complex formation. The ligand exchange reaction between the nickel complexes can be followed by means of UV-Vis spectroscopy. All reactions obey formally a second order rate law. The crystal and molecular structure of Bu4N[Zn- (dmit)(Et2dtc)] is reported. The compound crystallizes orthorhombic, space group Pna21 with four molecules in the unit cell; a=22.573(4), b= 9.892(1), c=14.964(3) A. Distorted tetrahedral coordination geometry is found for the ZnS4 moiety with a dihedral angle of 89.6(2)° between the chelate planes. The ZnS distances in the dithiolene (dmit) part of the molecule are clearly shortened in comparison to (Bu4N)2 [Zn(dmit)2].

Magnetic properties of spin-crossover systems in iron(III) thioseleno- and diselenocarbamates. Effect of dilution in the corresponding cobalt(III) or indium(III) complex matrices on EPR spectra

Abstract The temperature-dependent magnetic moments between 8 and 310 K have been measured for a series of iron(III) tris-thioselenocarbamates, Fe(SSeCNR 2 ) 3 , where NR 2 is N(CH 2 C 6 H 5 ) 2 , N(CH 2 ) 4 , N(CH 2 ) 5 , N(CH 2 ) 4 O or N(C 6 H 11 ) 2 . Whereas the dibenzyl, piperidyl and morpholyl derivatives clearly show spin-crossover behavior at room temperature reaching the low-spin state near liquid nitrogen temperature, the dicyclohexyl derivative is in the pure low-spin state at all temperatures measured. The pyrrolidyl complex, mainly high spin at higher temperatures, exhibits substantial spin-crossover behavior even at 8 K. The EPR powder spectra of the iron(III) tris-thioselenocarbamates, diluted (1:99%) with the corresponding cobalt(III) or indium(III) tris-thioselenocarbamate have been recorded between 120 K and room temperature. These spectra can be used as fingerprints to study qualitatively the influences of temperature and matrix effects on the electronic configuration of spin-crossover systems. In most cases they exhibit a relatively narrow signal at g ≈ 2 and two broad signals with g ≈ 4 and g ≈ 2 which have been attributed to the S =1/2 and S =5/2 state, respectively. Spectra for the corresponding tris- diselenocarbamates are also included and correlated.

Multinuclear (1H, 13C, 59Co, 77Se) NMR studies of thioseleno- and diselenocarbamato complexes of cobalt(III) and indium(III) in CDCl3 solution

Abstract The proton decoupled 13C NMR spectra of several Co(Se2CNR2)3, Co(SSeCNR2)3, In(Se2CNR2)3 and In(SSeCNR2)3 complexes(where R=organic substituent) have been measured in CDCl3 solution (23–64 mM). Each of the diselenocarbamate complexes exhibits a single peak for the NCSe2 carbon at 188–197 ppm for Co(III) and at 186–198 ppm for In(III) complexes. The alkyl carbons in the position alpha to the amine N also appear as a single peak. The In(SSeCNR2)3 complexes exhibit single peaks for the NCSSe carbons (192–202 ppm), but the alkyl carbons in the position alpha to the amine N appear as two distinct singlets, indicating hindered rotation about the SSeCNR2 bond. The Co(SSeCNR2)3 complexes exhibit four peaks of approximately equal intensity for the NCSSe carbon which is interpreted as evidence for the stereochemical rigidity of the facial and meridional isomers. The alkyl carbons in the position alpha to the amine N appear as six peaks (except for occasional accidental degeneracy) which is interpreted as evidence for hindered rotation about the SSeCNR2 bond in these two isomers. The 1H NMR spectra of these complexes have been measured in CDCl3 solution (30–63 mM). The 1H spectra of Co(Se2CNR2)3 are similar to those reported for Co(S2CNR2)3, but those for the Co(SSeCNR2)3 complexes are further split by hindered rotation about the SSeCNR2 bond rendering each R non-equivalent. The 1H spectra for the various derivatives of In(SSeCNR2)3 and In(Se2CNR2)3 are similar and indicate ra pid D⇄cL interconversion and evidence (in the case of In(SSeCNR2)3) for hindered rotation about the CN bond. The 59Co NMR spectra of the Co(Se2CNR2)3 complexes exhibit signals (6690–7260 ppm) in close agreement with results reported in the literature. The 59Co NMR signals of Co(SSeCNR2)3 are approximately identical to those of the corresponding Co(S2CNR2)3 complexes but are generally at lower field than for the corresponding Co(Se2CNR2)3 complexes. Similar to the dithiocarbamate complexes, there is evidence for a correlation between the 59Co chemical shifts and μeff2 for the corresponding Fe(SSeCNR2)3. The 77Se NMR spectra of these complexes have been measured in saturated CDCl3 solution. The 77Se spectra of the diselenocarbamates exhibits single peaks with In exhibiting a higher chemical shift (approx. 400 ppm) than the corresponding Co complex. This trend is seen in the corresponding thiosclenocarbamates, but the Co derivatives generally exhibit two peaks of approximately equal intensity, indicating the stereochemical rigidity of the fac and mer isomers.