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Issue 13, 2005
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Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer ligands and metal complexes

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Abstract

Reactions of the diphosphine 1,3-C6H4(CH2PH2)2 and fluorous alkenes H2C[double bond, length as m-dash]CHRfn (Rfn = (CF2)n−1CF3; n = 6, 8) at 75 °C in the presence of AIBN give the title ligands 1,3-C6H4(CH2P(CH2CH2Rfn)2)2 (3-Rfn) and byproducts 1,3-C6H4(CH3)(CH2P(CH2CH2Rfn)2) (4-Rfn) in 1 : 3 to 1 : 5 ratios. Workups give 3-Rfn in 4–17% yields. Similar results are obtained photochemically. Reaction of 1,3-C6H4(CH2Br)2 and HP(CH2CH2Rf8)2 (5) at 80 °C (neat, 1 : 2 mol ratio) gives instead of simple substitution the metacyclophane [1,3-C6H4(CH2[upper bond 1 start]P(CH2CH2Rf8)2[lower bond 1 start]CH2-1,3-C6H4CH2P[lower bond 1 end](CH2CH2Rf8)2C[upper bond 1 end]H2]2+2Br, which upon treatment with LiAlH4 yields 3-Rf8 (20%), 4-Rf8, and other products. Efforts to better access 3-Rf8, either by altering stoichiometry or using various combinations of the phosphine borane (H3B)PH(CH2CH2Rf8)2 and base, are unsuccessful. Reactions of 3-Rfn with Pd(O2CCF3)2 and [IrCl(COE)2]2 (COE = cyclooctene) give the palladium and iridium pincer complexes (2,6,1-C6H3(CH2[upper bond 1 start]P(CH2CH2Rfn)2)2)Pd[upper bond 1 end](O2CCF3) (10-Rfn; 80–90%) and (2,6,1-C6H3(CH2[upper bond 1 start]P(CH2CH2Rf8)2)2)Ir[upper bond 1 end](Cl)(H) (11-Rf8; 29%), which exhibit CF3C6F11/toluene partition coefficients of >96 : <4. The crystal structure of 10-Rf8 shows CH2CH2Rf8 groups with all-anti conformations that extend in parallel above and below the palladium square plane to create fluorous lattice domains. NMR monitoring shows a precursor to 11-Rf8 that is believed to be a COE adduct.

Graphical abstract: Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer ligands and metal complexes

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Publication details

The article was received on 15 Feb 2005, accepted on 19 May 2005 and first published on 09 Jun 2005


Article type: Paper
DOI: 10.1039/B502309B
Citation: Dalton Trans., 2005,0, 2275-2283
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    Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer ligands and metal complexes

    R. Tuba, V. Tesevic, L. V. Dinh, F. Hampel and J. A. Gladysz, Dalton Trans., 2005, 0, 2275
    DOI: 10.1039/B502309B

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