Studies of the synthesis, structure, and reduction of trans-dichloro bis(2,3-dihydro-4- and 7-methylbenzo[b]thiophene)palladium(II) complexes

trans-Dichlorobis(2,3-dihydro-4- and -7-methylbenzo[b]thiophene)palladium(II), 1b and 1c, have been prepared by reaction of 2,3-dihydro-4- and -7-methylbenzo[b]thiophenes with palladium(II) chloride. Both 1b and 1c exhibit complex 1 H and 13 C NMR spectra as a result of inversion of the sulfur-containing ligands. Their structures were confirmed by single crystal X-ray studies. 1b crystallized in the triclinic space group [Formula: see text] (a = 7.219(2), b = 8.441(5), c = 8.494(7) Å, α = 61.47(5)°, β = 88.85(4)°, γ = 84.40(3)°, and R = 0.067 for 1372 observed of 1760 unique reflections). 1c also crystallized in the triclinic space group [Formula: see text] (a = 7.730(3), b = 8.056(3), c = 8.516(4) Å, α = 62.87(3)°, β = 82.31(3)°, γ = 88.82(3)°, and R = 0,040 for 1425 observed of 1825 unique reflections), 1b and 1c and the complex 1a (prepared from 2,3-dihydrobenzo[b]thiophene) were unstable in the presence of molecular hydrogen at ambient conditions, liberating the parent dihydrobenzothiophenes and forming elemental palladium. 1a was also unstable to the organic hydrogen donor tetrahydronaphthalene, again forming Pd and 2,3-dihydrobenzothiophene. Complexes 1a–c were shown to promote the shift of CO/H 2 O to hydrogen and CO 2 although most of the hydrogen was consumed by the reduction of Pd(II) to Pd 0 .