A Layered or Modular Approach to Catalyst Design

In hydrogenase enzymes, there is an outer coordination sphere that does not involve direct interactions with the metal center of the active site or the coordinated substrate. However, this outer coordination sphere is important because it controls interactions between the catalytic core and the external environment. For example. 

Using the First Coordination Sphere to Control the Eneigies of Catalytic Intermediates 

nickel complexes are approximately ISkcalmor better hydride acceptors than the corresponding palladium complexes. The hydride acceptor ability of [M (diphosphine) 2] complexes is also a function of the substituents on the diphosphine ligands. The hydride acceptor abilities of [Ni(dppe)2] and [Ni(dmpe)2] are -63 and -SlkcalmoT, respectively (where dppe is bis(diphenylphosphino)ethane 

H2 pressure = 1 atm, pH = 8.5, energy in kcal mol ), reaction profile for H2 oxidation (c), same 

Using the Second Coordination Sphere to Control the Movement of Protons between the Metal and the Exterior of the Molecular Catalyst 

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