The Influence of Stepwise P-Oxidation on the Coordination and Redox Behavior of W–Bisphosalkyne Complex Ligands

The terminal phosphine groups at the tungsten bisphosphine alkyne complex [Tp*W(CO)(I)(η2-C,C′-Ph2PC2PPh2)] (2) {Tp* = hydridotris(3,4,5-trimethylpyrazolyl)borate} were selectively oxidized by common methods to form the alkyne complexes 2EE (E = O, S) with either two phosphine oxide or two phosphine sulfide substituents. The respective mono-oxidized analogues 2E (E = O, S) were obtained by subjecting the already oxidized intermediates [Tp*W(CO)(I)(η2-C,C′-Ph2P(E)C2H)] 1E (E = O, S) to a late-stage phosphine introduction at the complex template. These modulations of the peripheral alkyne moiety have a clear impact on the redox potential of the metal-based oxidation altering the W(II/III) potential by +0.1 V on average per oxidized phosphine. In contrast to the comparable redox behavior of 2O and 2S, the coordination behavior of these complex ligands differs substantially. XRD studies show that complex 2 and the sulfide 2S act either as a P,P’- or P,S-chelate ligand leading to the dinuclear complexes [(2)Pd...