Chalcogen-labeled cores

Cluster Assembly Mechanisms Chalcogen-Labeled Cores... 

Scheme 5.10 Chalcogen-labeled cluster syntheses (M = Mo, W). Roman numerals refer to reaction types indicated in the text. For clarity, only general cluster core frameworks are depicted. Terminal ligands (not shown) 40, M- Bu3tach and Fe-(Cl or SR) (upper left reaction only) all other clusters, W-Tp, Mo-Tp, Fe-Cl (40, 42), Fe-PEtj (43), Fe-(Q )H (44).

The main characteristic of the M038 core was found in the distinction between the equatorial and axial chalcogen atoms in the /X2-8 ligands (see (66) without additional X). Generally, the equatorial Mo-8 bond distance was longer than the Mo-8 axial distance. Consequently, the equatorial 8 atoms were more labile towards abstraction and substitution, as was demonstrated by the preparation of 8 /8 " -labelled isotopomers of [M03 87(82)3]. Vibrational spectra of a range of salts of [Mo38b] estabhshed that they are correctly represented as [Mo3(/u.3-8)(/u.-8)3(/u.,/u, -82)3] -... 

Chalcogen incorporation was monitored in the syntheses in Scheme 5.10 compound labels 40-44 in this scheme refer to general cluster core configurations without specific reference to terminal ligands. All reactions involved heterometallic clusters prepared from the facially chelated mononuclear molybdenum or tungsten trisulfide species 38 and 39, and from the previously described MoFe3S4 cubane 12-Mo site-specific... 

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