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The synthesis of the first dithioaoetylacetonate of a Group VI transition metal has been achieved by reduction of the 3,5-dimethyl-1,2-dithiolium cation with divalent chromium. The physical properties of the dark green monomer [Cr(SacSac)3] are reported.

The product of iodination of the DNA-binding dye Hoechst 33258,4-[5′- (4′′′-methylpiperazin-1′′′-yl)-2′,5′-bi-1H-benzimidazol-2′-yl]phenol (1), has been identified as the monoiodo derivative, i.e. 2-iodo-4-[5′- (4′′′-methylpiperazin-1′′′-yl)-2′,5′-bi-1H-benzimidazol-2′-yl]phenol (2), by mass spectrometry and by comparison of the 1H and 13C n.m.r . spectra of (1) and (2) with those of 2,5-disubstituted benzimidazole model compounds (3) and (4).

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When an anhydrous mixture of liquid hydrogen sulphide and liquid sulphur dioxide contained in a sealed tube at -78 �C is gently warmed, the liquid remains clear until the temperature reaches c. -40 �C, when sulphur is slowly deposited. Careful measurements reveal that the two compounds always react in the mole ratio, H2S : SO2 = 3 : 2, which contrasts with the stoichiometric equation 2H2S + SO2 =2H2O + 3S, widely quoted for their reaction in the moist gaseous phase or in aqueous solution. This low temperature reaction forms the basis of a novel high vacuum method for estimating milligram quantities of hydrogen sulphide when in the presence of gases, such as carbon dioxide, whose volatilities are sufficiently similar to preclude the use of normal low-temperature vacuum fractionation methods.