Sulfurization and Selenization of the Halfsandwich Nitrosylmetal

The photo-induced decarbonylation o f Cp*Cr(CO)2NO in acetonitrile solution in the presence o f excess sulfur leads to the cjWo-pentasulfido complex Cp*Cr(NO)(S5) (1 a), while in the case o f limited sulfur supply the binuclear bis(//-disulfido) complex Cp*2Cr2(NO)2(/i-S2)2 (4 a) is formed preferentially. The corresponding reaction with elemental selenium produces Cp*2Cr2(N O )2(//-Se2)2 (4b), irrespective o f the available amount o f selenium. Photodecarbonylation o f Cp*M o(CO)2NO gives only the binuclear derivates Cp*2M o2(N O )2(//-E2) (E = S (5 a), Se (5 b)) which are also obtained by treating Cp*M o(NO)I2 with H2S or H2Se, respective­ ly. Nitrosyl loss predominates if the tungsten complex Cp*W (NO)I2 is reacted with H2S; in an argon atmosphere the products are Cp*W(S)(S2)(I) (7 a) and Cp*2W2(S)2(u-S)2 (8 a), while in air some Cp*W (NO)(S5) (3a) and the oxo compounds C p*W (0)(S2)I (7c), Cp*2W2(Ö)2(//-S)2 (8c) and C p*,W ,(S)(0)(//-S)2 (8d) are formed. The analogous reaction with H2Se leads to Cp* W (NO)(Se5) (3b), Cp*2W2(0 )2(/z-Se)2 (9c) and Cp*2W2(Se)(O)0u-Se)2 (9d), respectively. The binuclear tungsten complexes 8 a,c,d and 9c,d contain a central W(/i-E),W framework (E = S or Se) which is unaffected by air, while terminal sulfido and selenido ligands are quanti­ tatively converted into the corresponding terminal oxo ligands in the presence o f air in CH2C12 or THF solution. With the preparation o f Cp*2W2(0 )2(//-E)2 (E = S (8c) and Se (9c)), the series o f dioxo complexes containing a pair o f monochalcogen bridges (E = O, S, Se, Te) has become complete. The new complexes have been characterized by their IR (v(NO)), 'H and 13C N M R (Cp*) spectra as well as by electron-impact mass spectrometry. According to the X-ray structure analyses, the binuclear compounds Cp*2Cr2(N O )2(//-S2)2 (4 a) and Cp*2M o2(N O )2(//-Se2)2 (5 b) contain two 14-electron [C p*M (N O )j fragments which are connected by a pair o f dichalcogen (rj],tj2-E2) bridging ligands (M = Cr or M o, E = S or Se). The central M2E2 four-membered ring is not planar, and the binuclear molecules are chiral.