Binding nucleophiles to [Fe4Y4Cl4](2-) (Y = S or Se) can increase or suppress the rate of proton transfer to the cluster.
In the proton transfer reactions between [Fe 4Y 4Cl 4] (2-) (Y = S or Se) and [pyrH] (+) (pyr = pyrrolidine) in the presence of a variety of nucleophiles (L = I (-), Br (-), PhS (-), EtS (-) or ButNC), initial binding of the nucleophile can occur to generate [Fe 4Y 4Cl 4(L)] ( n- ). The subsequent rate of proton transfer depends markedly on the nature of L. Stopped-flow kinetic studies show that proton transfer from [pyrH] (+) to [Fe 4Y 4Cl 4] (2-) { (S) k 4 = (2.1 +/- 0.5) x 10 (4) dm (3) mol (-1) s (-1); (Se) k 4 = (8.0 +/- 0.5) x 10 (3) dm (3) mol (-1) s (-1)} is increased by prior binding of L = PhS (-) or Bu ( t )NC to form [Fe 4Y 4Cl 4(L)] (n-) ( (S) k 7 (L) approximately 1 x 10 (6) dm (3) mol (-1) s (-1)), but prior binding of L = I (-), Br (-), or EtS (-) to the clusters inhibits the rate of proton transfer {e.g. (S) k 7 (I) = (6.0 +/- 0.8) x 10 (2) dm (3) mol (-1) s (-1); (Se) k 7 (I) = (4.5 +/- 0.5) x 10 (2) dm (3) mol (-1) s (-1)}. This behavior is correlated with the bonding characteristics of L and the effect this has on bond length reorganization within the cluster upon proton transfer.
Chemistry, School of Natural Sciences, Newcastle University, Newcastle upon Tyne, UK.
Katie
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Bates
Richard A
RA
Henderson
D002713:Chlorine; D007501:Iron; D007700:Kinetics; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D012643:Selenium; D013455:Sulfur
D008024:Ligands; D009942:Organometallic Compounds; D011522:Protons; D002713:Chlorine; D013455:Sulfur; D007501:Iron; D012643:Selenium