The study of the nucleophilic degradation of S8 by the methanide complex [Mn(CO)4[(PPh2)2CH]] (2) has led to the preparation of a unique class of polysulfide derivatives of formula [(CO)4Mn[(PPh2)2C-Sn-C(PPh2)2]-Mn(CO)4]. The structures of 3 (n = 6), 4 (n = 2), and 7 (n = 1) have been determined by X-ray crystallography, whereas those polysulfides with the sulfur chains S7, S5, S4, and S3 have been detected by spectroscopic methods. The polysulfides with n > 2 lose sulfur spontaneously, a process that can be accelerated by treatment with PPh3 or Na/Hg. Complexes 3, 4, and 7 were protonated at the two methanide carbon atoms to give the cationic dinuclear derivatives [(CO)4Mn[(PPh2)2C(H)-Sn-C(H)-(PPh2)2]Mn(CO)4]2+ (8, n=6; 9, n=2; 10, n = 1). The 1H NMR spectrum of 9 suggests the existence of intramolecular C-H...S interactions, in agreement with the X-ray structural determination of this complex. By treatment of 4 and 7 with one equivalent of HBF4 it is possible to selectively protonate just one methanide carbon atom, which allows the isolation of the mixed cationic derivatives R(CO)4Mn[(PPh2)2C(H)-Sn-C(PPh2)2]Mn(CO)4]+ (11, n = 2; 6, n = 1). Additionally, heterometallic complexes containing a bridging disulfide unit, of general formula [(CO)4Mn[(PPh2)2C(AuPPh3)S-SC-(AuPPh3)(PPh2)2]Mn(CO)4]2+ (12) and [(CO)4Mn[(PPh2)2C(H)S-SC(AuPPh3)-(PPh2)2]Mn(CO)4]+ (13), were prepared by reaction of 4 and 11, respectively, with [AuCl(PPh3)] in the presence of TlPF6.

This work presents a new application for MoO 3 combined with carbon paste to prepare a microcomposite electrode (Mo(VI) Ox /CPE) for the simultaneous determination of paracetamol (PCM) and Allure Red (AR) by square-wave voltammetry (SWV). The anodic peak currents for PCM and AR were 70.0 and 80.0 % high compared with an unmodified carbon paste electrode.The surface areas of Mo(VI) Ox /CPE and CPE were evaluated by cyclic voltammetry. The detection limit were 0.14 and 0.38 μmol/L for PCM and AR respectively. The relative standard deviations (RSDs) were 2.0 % (n = 7). Stability, shelf life and possible interferences were also evaluated with very acceptable results.

This report describes the simultaneous detection of the two dyes most commonly used in food, tartrazine (TZ) and sunset yellow (SY), based on a microcomposite of carbon paste decorated with La 2 O 3 and TiO 2. Anodic currents for SY-TZ were observed at 0.89-1.21 V by cyclic voltammetry (CV) separated with a ΔV of 0.32 V. The increased anodic peak currents compared to that of the unmodified carbon paste electrode were almost 50 and 41% for SY-TZ, respectively. The detection limits with the optimal amount of Lawere 0.02 and 0.03 µmol/L, respectively. The relative standard deviation (RSD) based on fifty measurements was less than 3%. The versatility and novelty of the sensor were tested with food samples containing these substances and other substances.

No abstract

Several diepoxyhexanoates and epoxyhexenoates were prepared by epoxidation of methyl 2‐methyl‐2,4‐hexadienoate or by Darzens condensation. Their 1 H‐ and 13C‐NMR. spectra were measured and assigned. Comparison of these data with the spectra of the antibiotics hedamycin (1) and pluramycin A (2) allowed the determi‐nation of the relative configurations in the side chains of these antibiotics. They were found to be (14R*,16S*,17R*,18S*) for hedamycin (1) and (14R*,16S*,17Z) for pluramycin A (2).