(dmit) and its dinuclear Ni(II) complex: spectroscopic and structural characterization

The optical properties of the dmit ion (dmits4,5-dimercapto-1,3-dithiol-2-thiolate) have been characterized under a range of conditions. The oxidatively sensitive anion is highly solvatochromic: lmaxs504 (H2O), 514 (MeOH), 568 (MeCN), and 632 nm (DMF). With a shift in absorption maximum of 4000 cm (DMF versus H2O), dmit 2y is possibly the most solvatochromic species known. The dianion is monoprotonated by NH4 q and binds CS2 to form a thioxanthate (C3S5PCS2 ). C NMR measurements of C-enriched dmit demonstrated that C3S5PCS2 2y exchanges with free CS2 via an associative pathway involving binding of a second molecule of CS2. Titration with acid showed that the M2dmit (MsNa, Cs) dissolves to give the dianion in protic solvents, rather than Hdmit. The conversion of aC3S5 2y to its b-isomer (‘Steimecke rearrangement’) occurs very slowly with purified Na2dmit, in contrast to the literature method. The salt (NBu4)2[Ni(dmit)2] is also highly solvatochromic but its behavior does not follow any simple pattern. Treatment of (NBu4)2[Ni(dmit)2] with 1/3 equiv. of [Ni(NCMe)6](BF4)2 gave the dinuclear compound (NBu4)2[Ni2(dmit)3], the first Ni–dmit 2y complex with a Ni/ dmit ratio that is not 1:2. The binuclear salt crystallizes as the CH2Cl2 solvate as dark purple prisms. The planar Ni(dmit)2 2y is bridged to Ni(dmit) via two sulfur atoms; the anion features a short Ni–Ni distance of 2.71 A. q2000 Elsevier Science Ltd All rights reserved. ̊