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)

Abstract

A comparative study of the electrochemical and proton-reduction behaviour of diphosphine-dithiolate complexes [M 2 (CO) 4 (l-dppm){l-S(CH 2 ) n S}] (M 5 Fe, Ru; n 5 2, 3) -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 [27-32] 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]. 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). ExperimentalComplexes 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

Synthesis, Characterization and Electrochemical Studies of bis(Monothiolato) {FeFe} Complexes [Fe2(μ‐SC6H4‐OMe‐m)2(CO)5L] (L = CO, PCy3, PPh3)

“…This is followed by protonation in the second step to form the [(H)Fe II Fe I ] 0 intermediate, i. e., 1H , 2H , 3H . In the third step, the hydride intermediate is reduced ( E cat =−2.22 ( 1 ), −2.52 ( 2 ), −2.07 V ( 3 )) to form the [(H)Fe I Fe I ] − monoanion intermediate, i. e., [ 1H ] − , [ 2H ] − , [ 3H ] − , which eventually takes up a second proton to release H 2 and regenerates the original catalyst in the final step [75,92,119–121] . The possibility of an ECCE mechanism also cannot be ruled out.…”

“…In the third step, the hydride intermediate is reduced (E cat = À 2.22 (1), À 2.52 (2), À 2.07 V (3)) to form the [(H)Fe I Fe I ] À monoanion intermediate, i. e., [1H] À , [2H] À , [3H] À , which eventually takes up a second proton to release H 2 and regenerates the original catalyst in the final step. [75,92,[119][120][121] The possibility of an ECCE mechanism also cannot be ruled out. The complexes might therefore, follow either an ECEC or ECCE mechanism or both for hydrogen generation, an unambiguous assignment of which is not possible at this point.…”

Redox Activity, Ligand Protonation, and Variable Coordination Modes of Diimino-Pyrrole Complexes of Palladium

“…Complex 5 rapidly reacts with acids such as HBF 4 to generate H 2 and a complicated mixture of products. The measured redox potential of 5 is not reducing enough to perform an outer-sphere reduction of a proton, and so combined reactivity where the complex is protonated before generating H 2 is likely. , We are currently working to further elucidate the nature and reactivity of this species.…”