Two tridentate thioether pincer ligands, 1,3-(RSCH2)(2)C6H4 (R = Bu-t, 1a; R = Pr-i, 1b) underwent cyclometalation using [(COE)(2)RhCl](2) in air/moisture-free benzene at room temperature. The resultant complexes, [mu-ClRh(H)(RSCH2)(2)C6H3-2,6](2) (R = Bu-t, 2a; R = Pr-i, 2b) are dimeric both in the solid state and in solution. A battery of variable-temperature one- and two-dimensional H-1 NMR experiments showed conclusively that both complexes undergo dynamic exchange in solution. Exchange between two dimeric diastereomers of 2a in solution occurred via rotation about the Rh-C-ipso bond. The dynamic exchange of 2b was significantly more complex as an additional exchange mechanism, sulfur inversion, occurred, which resulted in the exchange between several diastereomers in solution.