New binucleating ligand with two [P,S] chelation pockets on a single phenyl ring: Syntheses and X-ray structures of 1,4-bis(diphenylphosphino)-2,5-difluoro-3,6-bis(methylthio)benzene and of bimetallic complex (CO) < inf> 3 Fe(μ-[(PPh < inf> 2 )(SMe)C < inf> 6 F < inf> 2 (SMe)(PPh < inf> 2 )])Fe(CO) < inf> 3

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Double deprotonations of 1,4-dibromo-2,5-difluorobenzene with LDA (2 equiv., T < -90 °C) generate a reasonably stable organodilithium intermediate. Quenching this reaction mixture with chlorophosphines ClPR2 produce p-bis(phosphino)benzenes R2P-C6Br2F2-PR2 (R = Ph, 4a; R = iPr, 4b). Facile lithium-bromine exchange occurs upon exposure of 4a to BuLi (2 equiv., -80 °C), leading to the generation of another organodilithium intermediate. Addition of MeS-SMe (2 equiv.) to such reaction mixtures gives 1,4-bis(diphenylphosphino)-2,5-difluoro-3,6-bis(methylthio)benzene (2). Compound 2 is the first example of a neutral binucleating ligand featuring the [P,S] chelating sites on the opposite sides of a single phenyl ring. Compound 4b does not undergo the analogous transformation when subjected to the same conditions (2BuLi/2MeS-SMe). Addition of 2 to Fe(CO)5/2(Me3NO · 2H2O) reaction mixtures led to the isolation of the bimetallic complex {(CO)3Fe[P,S]-C6F2-[P,S]Fe(CO)3} (3), ([P,S] represents the chelating pockets formed by adjacent -PPh2 and -SMe groups). All of the new compounds were characterized by spectroscopic and analytical techniques (multinuclear NMR, mass-spectrometry, and/or elemental analysis). In addition, compounds 2 and 3 were characterized via single crystal X-ray diffraction methods. © 2006 Elsevier B.V. All rights reserved.

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Journal of Organometallic Chemistry