Molybdenum hexacarbonyl
Molybdenum
Colorless solid
Fixed
1.96 g · cm -3 ( 25 ° C)
150 ° C.
156 ° C.
Insoluble in water
Risk
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Molybdenum hexacarbonyl is a chemical compound having the formula Mo (CO) 6 This colorless compound is chromium and tungsten as its analogs, a volatile, relatively air- stable complex of molybdenum in the oxidation state zero. Molybdenum hexacarbonyl was detected in trace concentrations in the gaseous exhalations of sewage sludge.
Representation
Molybdenum hexacarbonyl is represented by the reduction of Molybdänhexachlorid ( MoCl6 ) under Kohlenstoffmonoxiddruck. However, it is often made in this manner in the laboratory, because the required equipment is expensive, and the compound can be acquired inexpensively.
They can be represented in the presence of Devarda alloy as halide acceptor by reductive Hochdruckcarbonylierung of molybdenum ( V) chloride.
Properties and Structure
Molybdenum hexacarbonyl has an octahedral ( Oh). The six Kohlenstoffmonoxidliganden are positioned radially around the central molybdenum atom. The dipole moment of the complex is 0 Debye. The Mo-C distance is 206 pm. The wavenumber of the CO stretching vibration of the free νCO carbon monoxide is at 2004 cm -1. It is a stable 18- Valenzelektronenkomplex.
The compound is relatively stable in air. It is sparingly soluble in nonpolar organic solvents. Like all metal carbonyls is molybdenum hexacarbonyl from improper handling of a source of volatile metal and carbon monoxide.
Reactions
The Kohlenstoffmonoxidliganden in molybdenum hexacarbonyl can be substituted by other ligands. It behaves similarly to the analogous tungsten complex. Molybänhexacarbonyl reacts with 2,2 '-bipyridine in a heteroleptic complex of Mo ( CO) 4 ( bipy). UV photolysis of molybdenum hexacarbonyl in tetrahydrofuran provides a substituted THF complex of Mo ( CO) 5 (THF). Many metal carbonyls are similar photochemically activated. The thermal reaction of molybdenum hexacarbonyl with piperidine provides a complex in which two Kohlenstoffmonoxidliganden piperidine are replaced by Mo (CO ) 4 ( piperidine ) 2 The two piperidine ligands in this yellow compound are labile bound, so that other ligands can be introduced under mild conditions. For example, the reaction of [Mo (CO ) 4 ( piperidine ) 2] and triphenyl phosphine in dichloromethane, the cis-substituted [Mo ( CO) 4 (PPh3) 2 ] complex. By refluxing in acetonitrile molybdenum hexacarbonyl is converted to the tris -acetonitrile derivative. The resulting air-sensitive compound is used as a source of Mo ( CO) 3 fragment. The reaction with allyl chloride gives [ MoCl (allyl ) (CO ) 2 ( MeCN) 2].
Use
Molybdenum hexacarbonyl and related derivatives can be used as a catalyst in organic synthesis, for example, for alkyne metathesis and Pauson -Khand reaction.
Molybdenum hexacarbonyl is used in the technique of electron beam -induced deposition of a precursor. As it evaporates easily and decays by the electron beam, it provides an easily accessible source of molybdenum atoms.