Diphosphine Mobility at a Binuclear Metal Center: A Concerted Double Trigonal-Twist in Bis(dithiolate) Complexes [M₂(CO)₄(μ-dppm){μ-S(CH₂)_nS}] (M = Fe, Ru; n = 2, 3)

Abstract

Heating [M 2 (CO) 6 {μ-S(CH 2 ) n S}] (M=Fe, Ru; n=2 (edt), 3 (pdt)) with bis(diphenylphosphino)methane (dppm) in toluene affords the bridged-diphosphine complexes [M 2 (CO) 4 ( μ-dppm){μ-S(CH 2 ) n S}]. At room temperature, all show two separate environments for the methylene protons of the diphosphine ligand, while at higher temperatures these coalesce to a single peak. This behavior, which interconverts the two sulfur atoms, is ascribed to a concerted double trigonal-twist of the M(CO) 2 P moieties. No such fluxional behavior was observed for the nonlinked dithiolate complexes [Fe 2 (CO) 4 (μ-dppm)(μ-SR) 2 ] (R=Me, Ph, p-tolyl). The X-ray structures of [M 2 (CO) 4 ( μ-dppm)( μ-edt)] (M=Fe, Ru) and [Fe 2 (CO) 4 (μ-dppm)( μ-SMe) 2 ] are presented in order to compare them to the previously reported [M 2 (CO) 4 ( μ-dppm)( μ-pdt)].

A comparative study of the electrochemical and proton-reduction behaviour of diphosphine-dithiolate complexes [M2(CO)4(μ-dppm){μ-S(CH2) n S}] (M = Fe, Ru; n = 2, 3)

“…Complexes 1-4 were prepared according to published methods [24,26,27,57] (see ESI for details). IR spectra were recorded on a Nicolet 6700 FT-IR spectrometer in a solution cell fitted with calcium fluoride plates, subtraction Electronic supplementary material The online version of this article…”

“…Diphosphines have been widely used in this context and can either bridge the diiron centre or chelate to one end, bridging complexes, [Fe 2 (CO) 4 -(l-diphosphine)(l-dithiolate)] being thermodynamically stable with respect to isomeric chelate complexes [Fe 2 (CO) 4 -(j 2 -diphosphine)(l-dithiolate)]. Consequently a large number of diphosphine-bridged diiron-dithiolate complexes have been reported [23][24][25][26][27][28][29][30][31][32] but surprisingly little attention has been paid to their proton-reduction chemistry [27][28][29][30][31][32] even though some, for example [Fe 2 (CO) 4 (l-dppf)(l-pdt)] (dppf = 1,1 0 -bis(diphenylphosphino)ferrocene), have been shown to be efficient proton-reduction catalysts [29]. Similarly, given the large number of diiron complexes tested as proton-reduction catalysts, related diruthenium complexes have not been widely studied [53][54][55][56].…”

“…Similarly, given the large number of diiron complexes tested as proton-reduction catalysts, related diruthenium complexes have not been widely studied [53][54][55][56]. Herein we detail a comparative investigation of the electrochemistry and proton-reduction behaviour of diiron and diruthenium complexes [M 2 (CO) 4 (ldppm)(l-pdt)] [24,27,57] and [M 2 (CO) 4 (l-dppm)(l-edt)] [26,27,57] (Fig. 1).…”

“…Herein we detail a comparative investigation of the electrochemistry and proton-reduction behaviour of diiron and diruthenium complexes [M 2 (CO) 4 (ldppm)(l-pdt)] [24,27,57] and [M 2 (CO) 4 (l-dppm)(l-edt)] [26,27,57] (Fig. 1). …”

“…Consequently a large number of diphosphine-bridged diiron-dithiolate complexes have been reported [23][24][25][26][27][28][29][30][31][32] but surprisingly little attention has been paid to their proton-reduction chemistry [27-32] even though some, for example [Fe 2 (CO) 4 (l-dppf)(l-pdt)] (dppf = 1,1 0 -bis(diphenylphosphino)ferrocene), have been shown to be efficient proton-reduction catalysts [29]. Similarly, given the large number of diiron complexes tested as proton-reduction catalysts, related diruthenium complexes have not been widely studied [53][54][55][56].…”