Molybdenum atom hexacarbonyl

The mononuclear metal carbonyls contain only one metal atom, and they have comparatively simple structures. For example, nickel tetracarbonyl is tetrahedral. The pentacarbonyls of iron, ruthenium, and osmium are trigonal bipyramidal, whereas the hexacarbonyls of vanadium, chromium, molybdenum, and tungsten are octahedral. These structures are shown in Figure 21.1. 

Finally, highly dehydroxylated alumina were prepared by heating at 800 °C under vacuum and their interaction with [Mo(CO)e] followed by infrared [19]. At room temperature, the hexacarbonyl molybdenum complex is physisorbed and the interaction of one oxygen atom of a CO ligand with defective aluminium sites (tetrahedral and octahedral sites were identified)... 

The starting point for most molybdenum-based carbonyl chemistry is the white crystalline air stable hexacarbonyl [Mo(CO)6], which is commercially available. Low valent compounds that are derived from this starting material tend to give products that obey the Effective Atomic Number Rule (EAN Rule). Since Mo° has a d configuration, six two-electron ligands are required to obey the EAN rule. 

A pure sample of (94, R = R = H cis) could be obtained (30°C, 60% yield) by treatment of (91) with (92 R = R = H) using molybdenum hexacarbonyl as mediator. Interestingly, with iron pentacarbonyl and 2,3-dimethyl-1,3-butadiene (92 R = R = Me), (91) formed only the alkylidene products (93 R = R = Me). The corresponding alkene (94, R = R = Me) did result exclusively from photochemical treatment of (91) with W(CO)6 at 0°C. Exposure of this alkene to Fe(CO)slhv isomerized it quantitatively to (93 R = R = Me), explaining the initial result. These, and other, findings allowed the authors to conclude that the mechanism involved an unusual 1,1-addition where the two silicon atoms added to the same carbon. Cl, of the diene, and the hydrogen atoms were shifted from Cl to C4 and C3. In addition, it was concluded that, in these reactions, a n-... 

A typical series of bidentate compounds are (8.138). While chain length does not appear greatly to affect bond angles at the P atom, it may decide between cis or trans isomer formation. Thus when molybdenum hexacarbonyl reacts with a two-carbon phosphine the trans compound (8.139a) is formed, but with a single carbon phosphine the cis derivative (8.139b) is obtained. 

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