Molybdenum sulfur dimers

A wide variety of other cydopentadienyl molybdenum-sulfur compounds are known including monomeric [Cp2Mo(SR)2],161,162 [Cp2MoS2] and [Cp2MoS4],163 dimeric... 

A molecular orbital study of molybdenum sulfur and sulfido bridged dimers bridged by... 

The molybdenum and tunsten diphenylacetylene compounds have been chemically useful primarily as precursors to the quadruple metal-metal bonded dimers [M(Por)]2, formed by solid-state vacuum pyrolysis reactions. However. Mo(TTP)()/"-PhC CPh) is also a useful substrate in atom-transfer reactions, reacting with Sx or Cp2TiS i to form Mo(TTP)=S. The reaction can be reversed by treatment of Mo(TTP)=S with PPh (which removes sulfur as PhxP=S) and PhC CPh. The order of preference for ligand binding to molybdenum 11) has been established to be PPh < PhC CPh < 4-picoline. ... 

III. The corresponding Kohn-Sham wave functions (Fig. 16b) show that the metallic edge states I and II are localized entirely on the molybdenum edge with sulfur dimers, whereas edge state III is associated with the fully covered sulfur edge (not shown). 

Molybdenum(V) chemistry is dominated by oxo complexes many of these exist as dimers, but monomeric species can be isolated from strongly addic solutions or under nonaqueous conditions. Non-oxo compounds are also known, both as monomers and as dimers or polymers with halide or sulfur bridges. ESR spectroscopy has been used extensively to investigate the properties of monomeric Mov systems, and has shown the participation of this oxidation state in the reactions of the oxomolybdoenzymes (see Section 36.6.7). 

Oxidation of the Mo 2 fragment is also induced by reacting Mo2(02CCH3)4 with [NR,] [J CN H.,)2] as is discussed in Section III.D.2. Oxidative addition across one of the dithiocarbamate C-S linkages leads to an oxidation state of 4+ for the molybdenum atoms in the resultant sulfur-bridged dimer (216, 217). 

Of the complexes studied, those with ancillary ligands that contain sulfur atoms have received the most attention. Among the most studied are the bis(dial-kyldithiocarbamate) molybdenum oxido complexes [196,197], Unfortunately, although these complexes react with certain enzyme substrates, their common problem as models for Moco active sites involves the propensity of the Movl dioxo and MoIV monoxo complexes to form a comproportionated Mov p-oxido dimer (Eq. 13 dtc = diethyldithiocarbamate). 

Cation 21 is the first homonuclear molybdenum carbonyl cluster to be characterized and is formed in a novel, sulfur-mediated disproportionation of two dimers into a trimer and a monomer with an accompanying electron transfer. Since there are nine CO groups per four Mo atoms in the product, but only 8 CO / 4 Mo in the starting dimers, a carbonyl-poor fraction must be produced. This fraction has been isolated but not characterized. 

---