SYNTHESES, X-RAY CRYSTAL-STRUCTURES, AND SPECTROSCOPIC PROPERTIES OF NEW NICKEL DITHIOLENES AND RELATED-COMPOUNDS

The direct addition of nickel powder to the reaction mixtures of 1,3-d ialkyl-4,5-dioxoimidazolidine-2-thione (1) with the thionation Lawesso n reagent produces [Ni-II(R(2)timdt(-))(2)] (R(2)timdt = 1,3-dialkylmi dazolidine-2,4,5-trithione). These complexes belong to a new class of nickel-dithiolenes, showing remarkably high absorption (epsilon approx imate to 80000 dm(3) mol(-1) cm(-1), lambda approximate to 1000 nm) in the near-infrared region (near-IR), accompanied by high photochemical stability that makes these complexes promising near-IR dyes. In the a bsence of nickel the reaction yields generally the compounds 4-b']diim dazolyl-1,3,8,10-tetraalkane-2,9-dithione (2) instead of the expected 1,3-dialkylimidazolidine-2,4,5-trithione. However, with bulky substitu ents on the nitrogen atoms, well-characterized reaction products have not been obtained until now. Only in the R = Pr-i case, the new tetrat hiocino isomer ]diimidazolyl-1,3,6,8-tetraisopropane-2,7-dithione (3) in trace amounts and the bis(1,3-diisopropyl-2-thioxoimidazolin-4-yl) disulfide (4) were isolated from the reaction with the Lawesson reagen t and P4S10, respectively. Reaction of 5 with different amounts of I-2 leads to a variety of products, and among them the following derivati ves have been characterized: [Ni-II(Pr(2)(i)timdt(-))(2)]. 2I(2) (6) a neutral adduct in which each I-2 molecule interacts with each periphe ral thione sulfur atom of 5; [Ni-II(Pr(2)(i)timdt(-))(2)]. 2I(2) . 1/2 I(2) (7), which differs from 6 with the presence of half diiodine as a guest; with a larger diiodine excess (starting from a 1:10 molar rati o) a partial oxidation of 5 is achieved and [Ni-II(Pr(2)(i)timdt(-))(2 )] [Ni-II(I)(2)(Pr(2)(i)timdt)(2)]. 5I(2) (8) is formed, a ligand mixe d-valence compound in which the square-planar complex 5 and the octahe dral complex [Ni-II(I)(2)(Pr(2-)(i)timdt)(2)] (the ligand in neutral f orm) are bound by diiodine molecules in such a way that a sequence of 12 iodine atoms (S . I-2 ... I-2 ... I-... I-2 ... I-... I-2 ... I-2 . S) is formed. Spectroscopic and X-ray diffractometric studies of 3 (m onoclinic, space group P2(1)/n, a = 13.104(6) Angstrom, b = 15.091(6) Angstrom, c = 6.067(7) Angstrom, beta = 103.00(2)degrees, Z = 2), 4 (m onoclinic, space group C2/c, a = 18.717(5) Angstrom, b = 8.846(5) Angs trom, c = 14.475(5) Angstrom, beta = 97.78(2)degrees, Z = 4), 5 (ortho rhombic, space group Pna2(1), a = 18.806(5) Angstrom, b = 5.628(7) Ang strom, c = 23.665(5) Angstrom, Z = 4), 7 (triclinic, space group <P(1) over bar>, a = 9.126(7) Angstrom, b = 9.153(7) Angstrom, c = 12.924(6) Angstrom, alpha = 82.11(2), beta = 70.14(2), gamma = 72.51(2)degrees, Z = 1), and 8 (monoclinic, space group C2/c, a = 21.971(6) Angstrom, b = 28.081(5) Angstrom, c = 12.207(8) Angstrom, beta = 93.57(2)degrees , Z = 4) are given.