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)(3)Fe(mu-[(PPh2)(SMe)C6F2(SMe)(PPh2)]

摘要

Double deprotonations of 1,4-dibromo-2,5-difluorobenzene with LDA (2 equiv., T < -90 degrees C) generate a reasonably stable organodilithium intermediate. Quenching this reaction mixture with chlorophosphines CIPR2 produce p-bis(phosphino) benzenes R(2)p-C6Br2F2PR2 (R = Ph, 4a; R = Pr-i, 4b). Facile lithium-bromine exchange occurs upon exposure of 4a to BuLi (2 equiv., -80 degrees C), leading to the generation of another organodilithium. intermediate. Addition of MeS-We (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 (.) 2H(2)O) reaction mixtures led to the isolation of the bimetallic complex {(CO)(3)Fe[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. (c) 2006 Elsevier B.V. All rights reserved.