Syntheses and redox properties of mixed isocyanide, carbonyl, or nitrile complexes of rhenium(I)trans-[Re(CNMe)L(Ph2PCH2CH2PPh2)2]X [L = CNR (R = alkyl or aryl), CO, or NCMe; X = Cl, BF4, or PF6

Abstract

Complexes trans-[Re(CNMe)L(dppe)2]X[1;L = CNR (R = Me, But, Ph, C6H4Me-4, C6H4Cl-4, or C6H2Pri3-2,4,6,), CO, or NCMe; dppe = Ph2PCH2CH2PPH2; X = Cl, BF4, or PF6] were prepared from the reaction of trans-[ReCl(CNMe)(dppe)2] with the appropriate substrate (L), either in the presence to TIX (1; X = BF4 or PF6), in tetrahydrofuran (thf) or CH2Cl2, or in the absence of the thallium salt (1; X = Cl) in refluxing CH2Cl2; the latter route was also applied to the syntheses of trans-[Re(CNR)2(dppe)2]Cl [R = Me or C6H2Pri3-2,4,6 (2)] directly from the dinitrogen complex trans-[ReCl(N2)(dppe)2]. At a platinum electrode, in thf or NCMe–0.2 mol dm–3[Bu4N][BF4], complexes (1) undergo at least one reversible single-electron oxidation by cyclic voltammetry. The observed values of the half-wave oxidation potential are in agreement with those predicted from the application of equations relating the electrochemical ligand parameter PL′ electron richness Es′ and polarisability β of the binding metal centre; these parameters were also estimated for the {Re(CNR)(dppe)2}+ sites. An expression is also proposed to estimate the redox potential of mixed-ligand complexes of the type [M′sL(L′)](M′s= 14-electron metal site), as the average of the redox potential of [M′sL2] and [M′sL′2]; the conditions for its application are discussed and it was shown to be valid for complexes (1).