Linkage Isomerism in Thiophene Cyclometallated Palladium(II) Complexes. Crystal and Molecular Structure of the Isomers [Pd{n‐SC4H2C(H)=NCy}(O2CMe‐O)(PPh3)] (n = 3, 4)

Abstract

AbstractTreatment of 2‐SC4H3C(H)=NCy, a, or 3‐SC4H3C(H)=NCy, b, with palladium(II) acetate in toluene gave the dinuclear cyclometallated complexes [Pd{n‐SC4H2C(H)=NCy}(O2CMe)]2 (n = 5, 1a; n = 3, 1b; n = 4, 1b′), the latter two as a 1:1 mixture of linkage isomers, whose subsequent reactions produced isomeric mixtures in all cases. Reaction of 1a and 1b, 1b′ with aqueous sodium chloride or bromide yielded the corresponding halide‐bridged complexes [Pd{n‐SC4H2C(H)=NCy}(X)]2 (n = 5: X = Cl, 2a; X = Br, 3a; n = 3,4: X = Cl, 2b, 2b′; X = Br, 3b, 3b′) after metathesis. Reactions of the dinuclear compounds with tertiary phosphines in the appropriate molar ratio gave the mononuclear [Pd{n‐SC4H2C(H)=NCy}(Cl)(PPh3)] (n = 5, 6a; n = 3, 4 4b, 4b′) and [Pd{5‐SC4H2C(H)=NCy}{(Ph2PCH2CH2)2PPh‐P,P,P}](Cl), (5a), and the dinuclear [{Pd[5‐SC4H2C(H)=NCy](O2CMe)}2{μ–Ph2P(CH2)nPPh2}] (n = 2, 7a; n = 3, 8a; n = 4, 9a) complexes. The X‐ray crystal structure of complex 4b, 4b′ is described, establishing the presence of two isomers in the crystal lattice.