''trans''-Bis(dinitrogen)bis
,2-bis(diphenylphosphino)ethaneolybdenum(0) is a coordination complex with the formula Mo(N
2)
2(dppe)
2. It is a relatively air stable yellow-orange solid. It is notable as being the first discovered dinitrogen containing complex of molybdenum.
Structure
Mo(N
2)
2(dppe)
2 is an octahedral complex with idealized D
2h point group symmetry. The dinitrogen ligands are mutually trans across the metal center. The Mo-N bond has a length of 2.01 Å, and the N-N bond has a length of 1.10 Å. This length is close to the free nitrogen bond length, but coordination to the metal weakens the N-N bond making it susceptible to electrophilic attack.
Synthesis
The first synthetic route to Mo(N
2)
2(DPPE)
2 involved a reduction of molybdenum(III) acetylacetonate with triethylaluminium in the presence of dppe and nitrogen.
A higher yielding synthesis involves a four-step process.
In the first step,
molybdenum(V) chloride
Molybdenum(V) chloride is the inorganic compound with the empirical formula . This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents.
Structure
Usually cal ...
is reduced by acetonitrile (CH
3CN) to give
oCl4(CH3CN)2 Acetonitrile is displaced by tetrahydrofuran (THF) to give
oCl4(THF)2 This Mo(IV) compound is reduced by tin powder to
oCl3(thf)3 The desired compound is formed in the presence of nitrogen gas, dppe ligand, and magnesium turnings as the reductant:
: 3 Mg + 2 MoCl
3(THF)
3 + 4 Ph
2PCH
2CH
2PPh
2 + 4 N
2 → 2 ''trans''-
o(N2)2(Ph2PCH2CH2PPh2)2 + 3 MgCl
2 + 6 THF
Reactivity
The terminal nitrogen is susceptible to electrophilic attack, allowing for the fixation of nitrogen to ammonia in the presence of acid. In this way, Mo(N
2)
2(dppe)
2 serves as a model for biological nitrogen fixation. Carbon-nitrogen bonds can also be formed with this complex through condensation reactions with ketones and aldehydes, and substitution reactions with acid chlorides. The terminal nitrogen can also be silylated.
See also
*
Transition metal dinitrogen complex
Transition metal dinitrogen complexes are coordination compounds that contain transition metals as ion centers the dinitrogen molecules (N2) as ligands.
Historical background
Transition metal complexes of N2 have been studied since 1965 whe ...
*
Nitrogen fixation
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...
References
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Coordination complexes
Molybdenum(0) compounds
Phosphine complexes
Nitrogen compounds