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• 1663-45-2 1,2-bis-(diphenylphosphino)ethane 

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Synthesis and M?ssbauer effect study of several novel bridged derivatives of Me2Si[(η5-C5H4) 2Fe2(CO)4] and the crystal structure of Me2Si[(η5-C5H4) 2(CO)Fe(μ-CO)2Fe(Ph2PCH2PPh 2)]

Irradiation of a benzene solution containing Me2Si[(η5-C5H4)Fe(CO) 2]2 (1) and either Ph2PCH2PPh2 or Ph2PCH2CH2PPh2 has led to the isolation of the monosubstituted complexes Me2Si[(η5-C5H4) 2(CO)Fe-(μ-CO)2Fe(Ph2P(CH2) nPPh2)], where n is one, 2a, or two, 2b. The key feature in these syntheses is the use of a 450-W medium-pressure Hg lamp which has lost a considerable amount of its intensity through at least 2000 h of use. The crystal and molecular structure of 2a has been determined by single-crystal X-ray diffraction. Complex 2a crystallizes in the space group P21/c with a = 12.389 (4) A?, b = 21.525 (7) A?, c = 13.507 (3) A?, and β = 91.81 (2)° with Z = 4. The structure is refined to R1 = 0.057 and R2 = 0.063 for 3270 independent reflections having I > 3σ(I). The Mo?ssbauer effect spectra of 1 and 2 as well as of the complexes with intramolecular bidentate bis(phosphine) ligands, 3, and intermolecular bridging bis-(phosphine) ligands, 4, have been measured. The resulting spectra indicate only one iron site in 1, 3, and [(η5-C5H5)Fe(CO)2]2 (5) whereas two iron sites are observed in 2 and 4. The Me2Si bridge in 1 has little effect on the symmetry at the iron site as indicated by the similarity of its Mo?ssbauer quadrupole splitting with that of 5. In addition, the average isomer shift increases upon phosphine substitution as a result of more extensive phosphine to iron π-bonding. The variation in the isomer shift in view of the almost constant iron-iron bond distance in these dimers provides further experimental support for the lack of direct iron-iron bonding in these compounds.

Synthesis, characterization, and electrochemistry of the bis-bridged complexes Me2Si[η5-C5H4Fe(CO)] 2[Ph2P(CH2)n PPh2] (n = 1-3) and [Me2Si[(η5-C5H4) 2Fe2(CO)3]]2[Ph ...

Full title: Synthesis, characterization, and electrochemistry of the bis-bridged complexes Me2Si[η5-C5H4Fe(CO)] 2[Ph2P(CH2)n PPh2] (n = 1-3) and [Me2Si[(η5-C5H4) 2Fe2(CO)3]]2[Ph2P(CH 2)nPPh2] (n = 2, 3). Molecular structures of Me2Si[η5-C5H4Fe(CO)] 2[Ph2P(CH2)nPPh2] where n = 1 and 3. Photolysis of Me2Si[η5-C5H4Fe(CO) 2]2 (1) with a series of bis(phosphines) (L = Ph2P(CH2)nPPh2, where n = 1, 2, and 3) leads to the formation of substituted dinuclear and tetranuclear compounds of the form Me2Si[η5-C5H4Fe(CO)] 2[L] and [Me2Si[(η5-C5H4) 2Fe2(CO)3]]2[L], respectively. The ratio of these two types of compounds is dependent upon the ligand size (number of methylene units), stoichiometry, and the overall concentration employed. With the small ligands and dilute conditions, formation of the dinuclear product is favored. Under more concentrated reaction conditions and when an excess of 1 is used, the tetranuclear type of product becomes dominant. The electrochemistry of the dinuclear compounds indicate that both the silyl and the bis(phosphine) bridges are capable of stabilizing a two-electron oxidation product. This is demonstrated in the case of L = dppm where we observe, by fast-scan cyclic voltammetry, two, one-electron reversible oxidation steps. The structure of Me2Si[η5-C5H4Fe(CO)] 2[dppm] (3a) is determined by X-ray diffraction. It crystallizes in the space group Pnma (No. 62) with a = 13.754 (4) A?, b = 17.707 (4) A?, c = 13.771 (3) A? and α, β, and γ = 90.00° with Z = 4. The structure was refined to R1 = 0.041 and R2 = 0.045 for 2226 independent reflections having I > 3σ(I). The structure of Me2Si[η5-C5H4Fe(CO)] 2[dppp] (3c) is also determined by X-ray diffraction. It crystallizes in the space group P1 (No. 2) with a = 11.638 (11) A?, b = 11.833 (11) A?, c = 16.289 (14) A?, α = 111.22 (6)°, β = 72.67 (7)°, and γ = 107.02 (7)° with Z = 2. The structure is refined to R1 = 0.067 and R2 = 0.076 for 4115 independent reflections having I > 3σ(I). The overall geometry of 3a compared to 3c implies that some distortion occurs from the steric requirements of the larger dppp ligand. This includes a significant lengthening of the Fe-Fe bond in complex 3c by 0.024 (3) A? relative to 3a.

DOUBLY LINKED DINUCLEAR TRANSITION METAL COMPLEXES. SYNTHESIS OF Me3Si2L (L = dppe, dppm)

Photolysis of Me2Si2 in the presence of bis-phosphine ligands (dppe and dppm) gives good yields of doubly linked diiron complexes.In the reaction with dppe, a mechanically linked tetranuclear species can also be isolated.