TRANSITION-METAL COMPLEXES WITH SULFUR LIGANDS .113. SYNTHESES, X-RAYCRYSTAL-STRUCTURES, AND REACTIVITY OF MOLYBDENUM(II) COMPLEXES WITH THIOETHERTHIOLATE LIGANDS HAVING XS(4) DONOR ATOM SETS (X=S, O, NH)

In quest of molybdenum complexes that have sulfur donors in their coor dination sphere and exhibit reactivity toward small molecules such as CO, NO, NO+, N-3(-), and above all N-2, the chemistry of [Mo(''(R)XS(4 )'')] complexes has been investigated. Mo(II) complexes of the type [M o(CO)(2)(''(R)XS(4)'')] (R = H, X = S, 1a; R = tert-butyl, X = S, 1b; R = H, X = NH, 2; R = H, X = 0, 3) formed by reaction of [Mo(CO)(4)(Cl )(2)] or [Mo(CO)(3)(PPh(3))(2)(Cl)(2)] and the thiols ''(R)XS(4)''-H-2 or corresponding thiolates. Complex la served as a structural referen ce and proved the Mo center to be seven-coordinate. The [Mo(''S-5'')] fragment approximately forms a square pyramid at the base of which the two cis CO Ligands are coordinated. Crystal data of 1a 0.5Et(2)O: mon oclinic space group P2(1)/c; a = 14.182(7) Angstrom, b = 14.525(11) An gstrom, c = 11.421(15) Angstrom beta = 108.98(7)degrees, Z = 4, R/R(w) = 6.0/5.6. The [Mo(''S-5'')] fragment of 1a exhibits the meso-configu ration, and NMR spectra indicate the same configuration for the [Mo('' (R)XS(4)'')] fragments of the other CO complexes. Oxidation of 1-3 yie lded the C-s symmetrical Mo(IV) oxo complexes [Mo(=O)(''(R)XS(4)'')] ( R = H, X = S, 4a; R = tert-butyl, X = S, 4b; R = H, X = NH, 5; R = H, X = 0, 6). Complex 4a was characterized by X-ray structure analysis (o rthorhombic space group P2(1)2(1)2(1); a = 10.872(2), b = 14.502(5), c = 11.324(2) Angstrom; Z = 4; R/R(w) = 4.4/3.7%). When treated with PM e(3), 1a, 1b and 2 yielded the thermolabile-phosphine derivatives meso -[Mo(CO)(PMe(3))(''(R)XS(4)'')] (R = H, X = S, 7; R = tert-butyl, X = S, 9; R = H, X = NH, 8) whereas the reaction of 3 gave [Mo(CO)(PMe(3)) (2)(''OS4'')] (10). Reaction of 7 with an excess of PMe(3) resulted in cleavage of the bridging S(C2H4)(2) unit from the ''S-5''(2-) ligand and formation of the Mo(IV) complex [Mo(PMe(3))(2)(''S-2'')2] (11). Co mplex 11 was characterized by X-ray structure analysis (monoclinic spa ce group P2(1)/c, a = 16.857(4) Angstrom, b = 17.742(4) Angstrom, c = 7.569(2) Angstrom, beta = 93.53(2)degrees, Z = 4, R/R(w) = 2.8/2.6) an d contains a Mo center surrounded by four S and two cis P donors in a pseudo-trigonal prismatic arrangement. Complexes 1a and 1b reacted wit h NO+ or NO gas to give the NO complexes [Mo-(NO)(''S-R(5)'')]BF4 (R = H, 12; R = tert-butyl, 13) and [Mo(NO)(2)(''(US5)-U-bu'')] (14). NMR and IR spectra and reactivity suggest that 13 contains dinuclear catio ns which reversibly dissociate into mononuclear C-1 symmetrical[Mo-(NO )(''S-bu(5)'')](+) ions in solution. Complexes 13 and 14 added PMe(3) or N-3(-) to give [Mo(NO)(PMe(3))(''S-bu(5)'')] (15), [Mo(NO)(N-3)(''S -bu(5)'')] (16) and (NEt(4))[Mo(NO)(2)(N-3)(''S-bu(5)'')] (17). Althou gh all complexes contain small molecules as ligands which are substrat es or inhibitors for nitrogenase and 16 and 17 even molecules which th eoretically can conproportionate to give N-2, attempts to obtain N-2 c omplexes with [Mo(''(R)XS(4)'')] fragments remained unsuccessful.