Mariana Dennehy

Poly[(μ3-1,1-dioxo-1,2-benzoisothiazole-3-thiolato-κ3N:S3:S3)silver(I)]

The centrosymmetric title compound, [Ag(C(7)H(4)NO(2)S(2))]n, consists of dinuclear units in which two thiosaccharinate anions each bridge two Ag atoms via an endocyclic N atom and an exocyclic S atom across a crystallographic centre of inversion midway between the Ag atoms. The dimeric units are connected via Ag-S(exo) interactions to create two-dimensional networks. The thiosaccharinate anions bridge in a mu3-S:S:N manner. The Ag...Ag distance can be considered a strong argentophilic interaction.

A triclinic polymorph of cyclo-tetra-μ-thiosaccharinato-κ8S:S-tetrakis[(triphenylphosphane-κP)silver(I)].

The triclinic structure of the title compound, cyclo-tetrakis(μ-1,1-dioxo-1λ(6),2-benzothiazole-3-thiolato-κ(2)S:S)tetrakis[(triphenylphosphane-κP)silver(I)], [Ag(4)(C(7)H(4)NO(2)S(2))(4)(C(18)H(15)P)(4)], is a polymorph of the previously reported monoclinic structure [Dennehy, Mandolesi, Quinzani & Jennings (2007). Z. Anorg. Allg. Chem. 633, 2746-2752]. In both polymorphs, the complex lies on a crystallographic inversion centre and the bond distances are closely comparable. Some differences can be found in the interatomic angles and torsion angles involving the inner Ag(4)S(4) skeleton. The polymorphs contain essentially identical two-dimensional layers, but with different layer stacking arrangements. In the triclinic form, all layers are related by lattice translation, while in the monoclinic form they are arranged around glide planes so that adjacent layers are mirrored with respect to each other.

Bismuth (III) sulfide as additive: towards better lubricity without toxicity

Purpose The purpose of this study is to design a fluid formulation with good lubricant properties by using an environmentally friendly additive for: high and low contact pressure conditions and steel/steel and polymer/steel systems. Design/methodology/approach Bismuth (III) sulfide (Bi2S3, “green chemistry” synthesis) is added to a commercial vinyl-terminated silicone fluid (PDMS-Vi) to obtain different weight-per cent mixtures. Tribological performance of formulations is studied from Reichert’s tests (steel/steel system) and block on ring tests (polymer/steel). The results are compared with formulations prepared with commercial bismuth (III) sulfide (Bi2S3), molybdenum (IV) sulfide (MoS2) and graphite. Findings An orthorhombic crystal lattice (XRD ) and a high-purity product (XRF) are evidenced for synthesized Bi2S3. Lubricant properties increase when the weight-per cent of the synthesized Bi2S3 increases in formulations. The wear area decreases up to 90 per cent according to Reichert’s tests. The synthesized Bi2S3 shows a better tribological behavior when compared to commercial Bi2S3, MoS2 and graphite. Originality/value Replacement of lead derivatives by an environmentally friendly lubricant in extreme pressure (EP) formulations and excellent performance compared to commercially used additives are achieved.