Linkage Isomerism in Thiophene Cyclometallated Palladium(II) Complexes. Crystal and Molecular Structure of the Isomers [Pd{n‐SC 4 H 2 C(H)=NCy}(O 2 CMe‐ O )(PPh 3 )] (n = 3, 4)

Treatment of 2‐SC 4 H 3 C(H)=NCy, a , or 3‐SC 4 H 3 C(H)=NCy, b , with palladium(II) acetate in toluene gave the dinuclear cyclometallated complexes [Pd{n‐SC 4 H 2 C(H)=NCy}(O 2 CMe)] 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‐SC 4 H 2 C(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‐SC 4 H 2 C(H)=NCy}(Cl)(PPh 3 )] (n = 5, 6a ; n = 3, 4 4b , 4b′ ) and [Pd{5‐SC 4 H 2 C(H)=NCy}{(Ph 2 PCH 2 CH 2 ) 2 PPh‐ P , P , P }](Cl), ( 5a ), and the dinuclear [{Pd[5‐SC 4 H 2 C(H)=NCy](O 2 CMe)} 2 {μ–Ph 2 P(CH 2 ) n PPh 2 }] (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.