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- 6-trienyl) amine (1) (remove)
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Synthesis, Molecular Structure and Reactivity of Di(1-cyclohepta-2,4,6-trienyl) thioether, S(C7H7)2 and Tri(1-cyclohepta-2,4,6-trienyl) amine, N(C7H7)3
(2004)
- This thesis describes the synthesis, characterization and coordination chemistry of di(1-cyclohepta-2,4,6-trienyl) thioether, S(C7H7)2 (1), tri(1-cyclohepta-2,4,6-trienyl) amine, N(C7H7)3 (24), and di(1-cyclohepta-2,4,6-trienyl) amine, NH(C7H7)2 (25). The reaction of tropylium bromide, C7H7Br, with the gas hydrogen sulfide (H2S) leads to the di(1-cyclohepta-2,4,6-trienyl) thioether, S(C7H7)2 (1), which can undergo Diels-Alder reactions with maleic anhydride, maleimide and N-phenyl maleimide to give the adducts S(C7H7)(C7H7C4H2O3) (4a), S(C7H7)(C7H7C4H3NO2) (4b) and S(C7H7)(C7H7C10H7NO2) (4c), respectively. In these three compounds, one cyclohepta-2,4,6-trienyl ring has remained intact, whereas the other seven-membered ring was involved in the Diels-Alder reaction. The advantage of the potential ligand S(C7H7)2 (1) in comparison to other simple sulfanes is that it can act as a chelate ligand, using one of the non-planar seven-membered rings. In general, the central double bond of one of the seven-membered rings becomes coordinated to the metal. The disadvantage of the sulfane 1 is its sensitivity towards oxidation and its low thermal stability. The reactions of either Cr(CO)5(thf) or Cr(CO)4(eta4-C7H8) with one equivalent of 1 lead to the monosubstituted derivative Cr(CO)5[PhCH2S(C7H7)] (7), in which one seven-membered ring has remained unchanged and the other seven-membered ring has been transformed into a benzyl substituent. From the reaction of 1 with a mixture of chromium(carbonyl)(acetonitrile) complexes, Cr(CO)6-x(CH3CN)x (x = 1, 2, 3), the pentacarbonyl Cr(CO)5[S(C7H7)2] (6) could be obtained, in which both cycloheptatrienyl ring substituents are freely pending. Using the same method as for the chromium complexes, tetracarbonyl molybdenum Mo(CO)4[(eta2-C7H7)S(C7H7)] (10) was obtained from the reactions of either Mo(CO)5(thf) or Mo(CO)4(eta4-C7H8) with the sulfane 1. In complex 10 the ligand S(C7H7)2 is coordinated to the metal both through a lone pair of electrons at the sulfur atom and the central C=C double bond of a cyclohepta-2,4,6-trienyl substituent. Mo(CO)5[S(C7H7)2] (9) could be obtained from Mo(CO)6-x(CH3CN)x (x = 1, 2, 3); in analogy to 6, the sulfane ligand in 9 is coordinated to molybdenum exclusively through a lone pair of electrons at the sulfur atom. From the intermediate W(CO)5(thf), the pentacarbonyltungsten complex W(CO)5[S(C7H7)2] (13) was obtained, which could be converted thermally to the benzyl complex W(CO)5[PhCH2S(C7H7)] (14). In the reaction with the mixture of tungsten(carbonyl)(acetonitrile) complexes, W(CO)6-x(CH3CN)x (x = 1, 2, 3), the compounds W(CO)4[(eta2-C7H7)S(C7H7)] (15) and W(CO)5[S(C7H7)2] (13) were obtained; complex 15 was the main product. The reactions of either Mn2(CO)10 (under irradiation) or Mn(CO)5X (X = Cl, Br) with di(1-cyclohepta-2,4,6-trienyl) thioether (1) led to the organothiolato-bridged dimer Mn2(CO)8[S(C7H7)]2 (17) in addition to ditropyl, (C7H7)2. Subsequent substitution of two carbonyl ligands in 17 by stronger sigma-donor-pi-acceptor ligands such as tert-butyl isocyanide and trimethyl phosphite (tBuNC and P(OMe)3) gave the complexes Mn2(CO)6[tBuNC]2[S(C7H7)]2 (18) and Mn2(CO)6[P(OMe)3]2[S(C7H7)]2 (19). Both 17 and 18 contain a planar Mn2S2 core with the 1-cyclohepta-2,4,6-trienyl substituents in anti-position. In addition, some investigations with tri(1-cyclohepta-2,4,6-trienyl) amine, N(C7H7)3 (24), and di(1-cyclohepta-2,4,6-trienyl) amine, NH(C7H7)2 (25) were carried out. In analogy to the sulfane S(C7H7)2 (1), 24 and 25 can undergo Diels-Alder reactions with maleimide and N-phenyl maleimide to give the educts (C7H7)2N(C7H7C4H3O2N) (26b), (C7H7)N(C7H7C10H7NO2)2 (26c), (C7H7)NH(C7H7C4H3O2N) (27b) and (C7H7)NH(C7H7C10H7NO2) (27c), respectively. Similar to the synthesis of 24 and 25, the mixed tertiary amines di(1-cyclohepta-2,4,6-trienyl)phenylamine, N(Ph)(C7H7)2 (28), and (1-cyclohepta-2,4,6-trienyl)diphenylamine, N(Ph)2(C7H7) (29) were prepared using aniline or diphenylamine. The reaction of N(C7H7)3 (24) with [C7H7]BF4 (1:1) leads to the N-tropylidene-N-(1-cyclohepta-2,4,6-trienyl)immonium tetrafluoroborate salt, [(C7H6)N(H)(C7H7)]BF4 (30). Compound 30 has also been obtained using NH(C7H7)2 (25) as the educt. As expected, the tertiary amine N(Ph)(C7H7)2 (28) reacted with [C7H7]BF4 to give the dark-red salt [(C7H6)N(Ph)(C7H7)]BF4 (31). Attempts to use the amine N(C7H7)3 (24) as a ligand in transition metal complexes were unsuccessful. However, NH(C7H7)2 (25) reacts with the mixture of tungsten(carbonyl)(acetonitrile) derivatives to give the chelate tetracarbonyl complex W(CO)4[(C7H7)NH(eta2-C7H7)] (32), which is similar to the sulfane complexes 10 and 15. Compared with the versatile phosphane ligand tri(1-cyclohepta-2,4,6-trienyl) phosphane, P(C7H7)3, the analogous amine N(C7H7)3 (24) is unable to act as a coordination ligand, probably as a result of the steric shielding of the lone pair of electrons at the nitrogen atom.
