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Transition-Metal Complexes with Sulfur Ligands. 113. Syntheses, X-ray Crystal Structures, and Reactivity of Molybdenum(II) Complexes with Thioetherthiolate Ligands Having XS4 Donor Atom Sets (X = S, O, NH)

In quest of molybdenym complexes that have sulfur donors in their coordination sphere and exhibit reactivity toward small molecules such as CO,NO, NO(1+), N3(1-), and above all N2, the chemistry of [Mo("(R)XS4")] complexes have been investigated. Mo(II) complexes of the type [Mo(CO)2("(R)XS4")] (R = H, X = S, 1a; R = tert-butyl, X = S, 1b; R = H, X = NH, 2; R = H, X = O, 3) formed by reaction of [Mo(CO)4Cl2] or [Mo(CO)3(PPh3)2Cl2] and the thiols "(R)XS4"-H2 or corresponding thiolates. Complex 1a served as a structural reference and proved the Mo center to be seven-coordinate. The [Mo("S5")] fragment approximately forms a square pyramid atthe base of which the two cis CO ligands are coordinated. Crystal data of 1a.0.5Et2O: monoclinic space group P21/c; a = 14.182(7) ?, b = 14.525(11) ?, c = 11.421(15) ?, β = 108.98(7)°, Z = 4,R/Rw = 6.0/5.6. The [Mo("S5")] fragment of 1a exhibits the meso-configuration, and NMR spectra indicate the same configuration for the [Mo("(R)XS4")] fragments of the other CO complexes. Oxidation of 1-3 yielded theCs symmetrical Mo(IV) oxo complexes [Mo(=O)("(R)XS4")] (R = H, X = S, 4a; R = tert-butyl, X = S, 4b; R = H, X = NH, 5; R = H, X = O, 6). Complex 4a was characterized by X-ray structure analysis (orthorhombic space group P212121; a = 10.872(2) ?, b = 14.502(5) ?, c = 11.324(2) ?; Z = 4; R/Rw = 4.4/3.7%). When treated with PMe3, 1a, 1b and 2 yielded the thermolabile phosphine derivatives meso-[Mo(CO)(PMe3)("(R)XS4")] (R = H, X = S, 7; R = tert-butyl, X = S, 9; R = H, X = NH, 8) whereas the reaction of 3 gave [Mo(CO)(PMe3)2("OS4")] (10). Reaction of 7 with an excess of PMe3 resulted in cleavage of the bridging S(C2H4)2 unit from the "S5"(2-) ligand and formation of the Mo(IV) complex [Mo(PMe3)2("S2")2] (11). Complex 11 was characterized by X-ray structure analysis (monoclinic space group P21/c, a = 16.857(4) ?, b = 17.742(4) ?, c = 7.569(2) ?, β = 93.53(2)°, Z = 4, R/Rw = 2.8/2.6) and contains a Mo center surrounded by four S and two cis P donors in a pseudo-trigonal prismatic arrangement. Complexes 1a and 1b reacted with NO(1+) or NO gas to give the NO complexes [Mo(NO)("(R)S5")]BF4 (R = H, 12; R = tert-butyl, 13) and [Mo(NO)2("(bu)S5")] (14). NMR and IR spectra and reactivity suggest that 13 contains dinuclear cations which reversibly dissociate into mononuclear C1 symmetrical [Mo(NO)("(bu)S5")](1+) ions in solution. Complexes 13 and 14 added PMe3 or N3(1-) to give [Mo(NO)(PMe3)("(bu)S5")] (15), [Mo(NO)(N3)("(bu)S5")] (16) and NEt4[Mo(NO)2(N3)("(bu)S5")] (17). Although all complexes contain small molecules as ligands whichare substrates or inhibitors for nitrogenase and 16 and 17 even ...