Molybdenum interaction with hydroxylated

Molybdenum(VI) and tungsten(VI) are found to form only one of two possible isomeric ery-r/zro-type dimetallates analogously to 14 (O Fig. 2) with fourfoldly deprotonated ribitol. One of the terminal hydroxyl functions is not part of the coordination site. Even the formed isomer proves to have low stability due to unfavorable steric interaction between the terminal carbon atoms of the sickle conformer [25,26,37]. 

Molybdenum Carbonyl Catalysts. The elucidation of the structure and activity of molybdenum carbonyl catalyst systems, the first catalysts reported active for metathesis, continues to be the subject of investigation. Brenner and BurwelE " have identified the dominant surface species formed during the interaction of Mo(CO)6 with 7-alumina at various temperatures. Sub-carbonyl species, Mo(CO)y ads Cy = 3,4, 5, or 6), are formed in the reversible decomposition of Mo(CO)e at temperatures below 100° Activation at 100° C of Mo(CO)6 on partially hydroxylated alumina forms... 

A similar trend was found concerning the extractability of molybdenum by ammonia solution [41]. Signals due to bulk M0O3 were neither detected in the X-ray diffractograms nor in the UV-Vis spectra of the impregnated faujasites [40,41,43]. Corma et al., by means of IR spectroscopy, observed an interaction of molybdenum species incorporated in USY with all hydroxyls except the external silanol groups [39]. Furthermore,they found similar nsi/n o ratios at the surface and in the bulk from which they concluded that molybdenum species (as depicted in Fig. 1) are well dispersed in the zeolite pore system. 

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