Bis(dinitrogen)bis(1,2-bis(diphenylphosphino)ethane)molybdenum(0)
Chemical compound
From Wikipedia, the free encyclopedia
trans-Bis(dinitrogen)bis[1,2-bis(diphenylphosphino)ethane]molybdenum(0) is a coordination complex with the formula Mo(N2)2(dppe)2. It is a relatively air stable yellow-orange solid. It is notable as being the first discovered dinitrogen complex of molybdenum.[1]
2(n2)2revd2.png)
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| Identifiers | |
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3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| 59731 | |
PubChem CID |
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| Properties | |
| C52H48MoN4P4 | |
| Molar mass | 948.83 g·mol−1 |
| Appearance | Yellow-orange crystals[1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure
Mo(N2)2(dppe)2 is an octahedral complex with idealized D2h 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.[2] 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.[3]
Synthesis
The first synthetic route to Mo(N2)2(dppe)2 involved a reduction of molybdenum(III) acetylacetonate with triethylaluminium in the presence of dppe and molecular nitrogen.
A higher yielding synthesis involves a four-step process.[4] In the first step, molybdenum(V) chloride is reduced by acetonitrile (CH3CN) to give [MoCl4(CH3CN)2]. Acetonitrile is displaced by tetrahydrofuran (THF) to give [MoCl4(THF)2]. This Mo(IV) compound is reduced by tin powder to [MoCl3(thf)3]. The desired compound is formed in the presence of nitrogen gas, dppe ligand, and magnesium turnings as the reductant:
- 3 Mg + 2 MoCl3(THF)3 + 4 Ph2PCH2CH2PPh2 + 4 N2 → 2 trans-[Mo(N2)2(Ph2PCH2CH2PPh2)2] + 3 MgCl2 + 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(N2)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.[3]