Electrochemistry of Triphenylarsine-substituted Tungsten(0) Fischer carbene complexes

• Order of oxidation for cis-[AsPh3(CO)4WC(OEt)(Ar)]: Ar = C4H3S > C4H3O > C4H3NMe.
• Order of reduction for cis-[AsPh3(CO)4WC(OEt)(Ar)]: Ar = C4H3S > C4H3O > C4H3NMe.
• Increasing order of oxidation potential ∝ decreasing order of the energy of HOMO.
• Increasing order of reduction potential ∝ decreasing order of the energy of LUMO.

A combined electrochemical and density functional theory study on four triphenylarsine-substituted tetracarbonyl tungsten(0) Fischer carbene complexes of general formula [(CO)4(AsPh3)WC(OEt)(Ar)], with Ar = 2-thienyl (1), 2-furyl (2), 2-(N-methyl)pyrrolyl (3), 2,2′-bithienyl (4), revealed that electrochemical properties for these complexes follow the same trend as analogous pentacarbonyl and triphenylphosphine-substituted tetracarbonyl complexes in literature. The current results made it possible to establish a general trend for Fischer-type W-carbene complexes containing an aryl substituent, namely (largest metal oxidation and largest carbene carbon reduction potential) [(L)(CO)4WC(OEt)(2-thienyl)] > [(L)(CO)4WC(OEt)(2-furyl)] > [(L)(CO)4WC(OEt)(2-(N-methyl)pyrrolyl)] (L = CO, PPh3 or AsPh3).

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