Molybdenum complexes thiols

The reactions of dinuclear thioaldehyde and -ketone complexes with PR3 take a different course. When the dimeric complexes 112 are treated with PMe3 a Ti-S bond in 112 is cleaved and the monomeric complexes 113 are reversibly formed (see Scheme 26), 69 The reaction of 112 with benzene-thiol led to a Ti-C cleavage and formation of 1,3-propanedithiolato-(phenylthiolato) complex.69 The reaction of binuclear p-191 rf-thioketone molybdenum complexes related to 115 (M = Mo, E = S, R = Aryl) with P(OEt)3 also gave mononuclear complexes [Mo(CO)2(Et) i72-S = C(Aryl)2 (i75-C5H5)] by a rather complicated reaction sequence. When other phosphites were employed additionally binuclear complexes derived from addition of the phosphite to one molybdenum atom were isolated.225... 

The possible formation of molybdenum imido complexes during the reaction was also considered, but no conclusion concerning their possible role could be drawn. Note that a catalytic cycle in which a molybdenum complex reduces nitrobenzene (to aniline) forming an intermediate molybdenum-oxo complex has indeed been reported, but the reducing agent was a thiol, not CO... 

Ni(CN)3(NO)] - + iOa + HaO—[Ni(CN)3(NO)]2- + 20H-The importance of the redox nature of molybdenum centres in biological systems has been recognized in several studies. Model systems for nitrogenase, involving molybdate, catalytic amounts of iron(ii), and cysteine, effect the reduction of aliphatic nitriles to alkanes and ammonia in the presence of sodium borohydride. The reaction is accelerated by substrate concentrations of ATP, the active species being considered to be mononuclear molybdenum-thiol complexes. The dinuclear molybdenum complex (7) formed by... 

Molybdenum-based catalysts are highly active initiators, however, monomers with functionalities with acid hydrogen, such as alcohols, acids, or thiols jeopardize the activity. In contrast, ruthenium-based systems exhibit a higher stability towards these functionalities (19). An example for a molybdenum-based catalyst is (20) MoOCl2(t-BuO)2, where t-BuO is the tert-butyl oxide radical. The complex can be prepared by reacting M0OCI4 with potassium tert-butoxide, i.e., the potassium salt of terf-butanol. 

Trithiolene complexes are also known, for instance those of chromium, molybdenum, and tungsten [592f], having an octahedral geometry. Structures of the complexes above, as well as of a series of other thiolene (thiol) compounds, have been studied using various physical-chemical techniques (x-ray diffraction, NMR, EPR, and UV spectroscopy). Considerable attention has been devoted to their reducing and photochemical properties [1, vol.2]. 

A comprehensive review of spectrophotometric methods for the determination of ascorbic acid (1) was presented. Most of the methods are based on the reducing action of ascorbic acid, making use of an Fe(III)-Fe(II) redox system, and to a lesser extent Cu(II)-Cu(I), V(V)-V(IV) and phosphomolybdate/phosphotungstate-molybdenum/tungsten blue redox systems. A kinetic spectrophotometric method for the determination of L-ascorbic acid and thiols (RSH) was developed, whereby the absorbance of the Fe(II)-phen complex formed during the reaction of 1 or RSH with Fe(III)-phen was continuously measured at 510 nm by a double beam spectrophotometer equipped with a flow cell. The linearity range for 1 was 4-40 p,M and for RSH 8-80 xM. The method was validated for pharmaceutical dosage forms . 

Diamagnetic molybdenum (IV) thiolato complexes of the type [MoO(SR)4] were prepared by BH4 reduction of corresponding Mo precursors, by thiol exchange with [MoO (SC6H4CI-4) 4], or by reaction of [MoOCl (PPh2Me) 3]... 

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