Dithiolato- and halogenido-bridged nickel-iron complexes related to the active site of [NiFe]-Hases: preparation, structures, and electrocatalytic H production.

A new series of the structural and functional models for the active site of [NiFe]-Hases has been prepared by a simple and convenient synthetic route. Thus, treatment of diphosphines RN(PPh) (1a, R = p-MeCHCH; 1b, R = EtOCCH) with an equimolar NiCl·6HO, NiBr·3HO, and NiI in refluxing CHCl/MeOH or EtOH gave the mononuclear Ni complexes RN(PPh)NiX (2a, R = p-MeCHCH, X = Cl; 2b, R = EtOCCH, X = Cl; 3a, R = p-MeCHCH, X = Br; 3b, R = EtOCCH, X = Br; 4a, R = p-MeCHCH, X = I; 4b, R = EtOCCH, X = I) in 67-97% yields. Further treatment of complexes 2a,b-4a,b with an equimolar mononuclear Fe complex (dppv)(CO)Fe(pdt) and NaBF resulted in formation of the targeted model complexes [RN(PPh)Ni(μ-pdt)(μ-X)Fe(CO)(dppv)](BF) (5a, R = p-MeCHCH, X = Cl; 5b, R = EtOCCH, X = Cl; 6a, R = p-MeCHCH, X = Br; 6b, R = EtOCCH, X = Br; 7a, R = p-MeCHCH, X = I; 7b, R = EtOCCH, X = I) in 60-96% yields.

Hydrophilic Quaternary Ammonium-Group-Containing [FeFe]-Hydrogenase Models: Synthesis, Structures, and Electrocatalytic Hydrogen Production.

The first quaternary ammonium-group-containing [FeFe]-hydrogenase models [(μ-PDT)Fe (CO) {κ -(Ph P) N(CH ) NMe BzBr}] (2; PDT=propanedithiolate) and [(μ-PDT)Fe (CO) {μ-(Ph P) N(CH ) NMe BzBr}] (4) have been prepared by the quaternization of their precursors [(μ-PDT)Fe (CO) {κ -(Ph P) N(CH ) NMe }] (1) and [(μ-PDT)Fe (CO) {μ-(Ph P) N(CH ) NMe }] (3) with benzyl bromide in high yields. Although new complexes 1-4 have been fully characterized by spectroscopic and X-ray crystallographic studies, the chelated complexes 1 and 2 converted into their bridged isomers 3 and 4 at higher temperatures, thus demonstrating that these bridged isomers are thermodynamically favorable. An electrochemical study on hydrophilic models 2 and 4 in MeCN and MeCN/H O as solvents indicates that the reduction potentials are shifted to less-negative potentials as the water content increases.

Nonlinear control for a class of hydraulic servo system.

The dynamics of hydraulic systems are highly nonlinear and the system may be subjected to non-smooth and discontinuous nonlinearities due to directional change of valve opening, friction, etc. Aside from the nonlinear nature of hydraulic dynamics, hydraulic servo systems also have large extent of model uncertainties. To address these challenging issues, a robust state-feedback controller is designed by employing backstepping design technique such that the system output tracks a given signal arbitrarily well, and all signals in the closed-loop system remain bounded.