960
Inorg. Chem. 1993, 32, 960-964
Transition Metal Complexes with Sulfur Ligands. 95.' N 2 H 2 , N 2 H 4 , NH3, and N3- Complexes with Sulfur Dominated [Ru(PPhJ)('buS4')]Fragments ('buS4'2- = 1,2-Bis((2-mercapto-3,5-di-ferf-butylphenyl) thio)ethanato( 2-) ) Dieter Sellmann,' Joachim Kiippler, Matthias Moll, and Fak Knoch Institut fur Anorganische Chemie der Universitiit Erlangen-Nurnberg, Egerlandstrasse 1, D-8520 Erlangen, Germany
Received October 23, I992 [Ru(C1H)(PPh3)('b%S4')] (1) ('buS4'2-= 1,2-bis((2-mercapto-3,5-di-tert-butylphenyl)thio)ethane(2-)) was obtained by one-pot synthesis from [RuC12(PPh3)3], 'bUS4'-Li2,and HCl gas. Elimination of HCl from 1 by reaction with bases gave [RU(PP~~)('~US~')] (2). 2 formally contains a coordinatively unsaturated Ru center and reacted with Lewis buses such as N3-, NH3, and N2H4, yielding very soluble [Ru(L)(PPh3)("J"S4')] complexes (L = N3- (3),NH3 (4), N2H4 (5)). Oxidation of the hydrazine complex 5 led to the dinuclear diazene complex [p-N2H2(Ru(PPh3)('bS4')]2](a),which was characterized by an X-ray structure analysis. Crystals of 64CHzC12 are monoclinic, space group C 2 / c , with u = 2870.0(16) pm, b = 1380.4(4) pm, c = 2849.2(13) pm, 9, = 93.65(4)O, V = 11 265(9) X 106 pm3, 2 = 4, and R (R,) = 0.075 (0.072) for 5801 reflections. The diazene (HN==NH) ligand of 6 is stabilized by intramolecular N-H.-(S)2 hydrogen bonds, steric protection, and a Ru-N-N-Ru 4c-6e- r bond, but according to NMR experiments,6 is still highly reactive in solution. 4-6 can be regarded as model compounds for the active centers of nitrogenases, because they contain intermediates of N2 fixation bound to transition metal centers in a coordination sphere dominated by sulfur donors.
Introduction Diazene, HN=NH, is regarded a key intermediate of enzymatic N2 reduction,2 although it is extremely unstable in free state and decomposes above -180 0C.3 Stabilization of N2H2 at standard conditions could be achieved in a few cases by coordination to transition metals, but the resulting diazene complexes, e.g., [p-N2Hz{CpM(CO)2)2] (M = Mn, Re),4,S [p-N2H2(M'(C0)5)2J (M' = Cr, Mo, W),-and [Cr(CO)rN2Hr CpMn(C0)2],g are still rare and usually contain metalorganic complex fragments. The same holds for the mononuclear [W(N2H2)(CO)2(NO)(PCy3)2],lORecently the Ru complex [ ~ - N ~ H ~ R u ~ ( L * ) ~was D Preported1] B] (DPB = biphenylenediporphyrinato(4-), L* = 1-tert-butyl-5-phenylimidamle),in which N2H2bridges two cofacial ruthenium porphyrins. Of particular interest are [p-N2H2{Ru(PPh3)('S4'))2]l 2 ('Sq(2-= 1,2-bis((2mercaptophenyl)thio)ethane(2-)) and [p-N2H2(Fe('N~S4())2] l3 Author to whom correspondence should be addressed. Part 94: Sellmann, D.; Prechtel, W.; Knoch, F.;Moll, M. Inorg. Chem., in press. (a) Chatt, J.; Richards, R. L. In The Chemistry and Biochemisfry of Nitrogen Fixation; Postgate, J. R., Ed.; Plenum: London, 1971. (b) Chatt, J.; Leigh, G. J. Chem. SOC.Rev. 1972, I, 121. Wiberg, N.; Fischer, G.; Bachhuber, H. Chem. Ber. 1974, 107, 1456. Sellmann, D. J. Organomet. Chem. 1972, 44, C46. Sellmann, D.; Kleinschmidt, E. Z . Narurforsch. 1977, 32b, 795. (a) Sellmann, D.; Brandl, A.; Endell, R. J. Organomet. Chem. 1973, 49,C22. (b) Sellmann, D.; Brandl, A.; Endell, R. J . Organomer. Chem. 1976, 111, 303.
Sellmann, D.; Brandl, A.; Endell, R. J. Organomet. Chem. 1975, 97, 229.
(a) Sellmann, D.; Brandl, A.; Endell, R. Angew. Chem. 1973,85, 1121; Angew. Chem.,fnf.Ed. Engl. 1973,IZ. 1019. (b)Sellmann, D.; Brandl, A.; Endell, R. Z . Naturforsch. 1978, 33B, 542. (a) Sellmann, D.; Jiklden, K. Angew. Chem. 1977, 89, 480; Angew. Chem., I n t . Ed. Engl. 1977, 16, 464. (b) Sellmann, D.; Gerlach, R.; Jiklden, K. J. Organomer. Chem. 1979, 178. 433. Hillhouse, G. L. Personal communication, 200th National Meeting of the American Chemical Society, Washington, DC, 1990. Collman, J. P.; Hutchison, J. E.; Lopez, M.A,; Guilard, R.; Reed, R. A. J. Am. Chem. Soc. 1991, 113, 2794. (a) Sellmann, D.; Bdhlen, E.; Waeber, M.; Huttner, G.; Zsolnai, L. Angew. Chem. 1985, 97,984; Angew. Chem., Int. Ed. Engl. 1985.24, 981. (b) Sellmann, D.; Waeber, M. Z . Nafurforsch. 1986, 418, 877. (a) Sellmann, D.; Soglowek, W.; Knoch, F.; Moll, M. Angew. Chem. 1989, 101, 1244; Angew. Chem., Inr. Ed. Engl. 1989, 28, 1271. (b) Sellmann, D.; Soglowek, W.; Knoch, F.; Moll, M. Inorg. Chem., in press.
0020-166919311332-0960$04.00/0
('NHSl2-= 2,2'-bis( (2-mercaptophenyl)thio)diethylamine(2-)), because they contain iron or the homologous rutheniumand sulfur dominated coordination spheres as it is assumed for the metals in nitrogenases. All nitrogenasesisolated so far contain ironI4and most of them in addition either molybdenumIs or vanadium.l6 The discovery of a nitrogenase containing exclusively iron" suggests that in all nitrogenases coordination, activation, and reduction of N2 take place at the iron centers. For this reason, iron complexes with sulfur ligands and vacant coordination sites for binding N2 or its reduction productsN2H2, N2H4,and NH3, can be regarded model compounds for nitrogenases with respect to structureand function, and ruthenium complexes become of interest, if analogous iron complexes are too labile to be isolated and characterized. X-ray diffraction studies of [~-NZHZ{RU(PP~~)('S,')~ l 2 and [p-N2H2(Fe("~S
