The influence of coverage on the structure and bonding of thiophene within chemisorbed overlayers on Cu(111) has been investigated. Normal incidence X-ray standing wavefield absorption (NIXSW) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS) were used to determine the adsorption site and orientation of thiophene. In the low coverage phase the thiophene molecule forms a pi -bonded species, adopting an atop adsorption site with a Cu-S separation of 2.62 +/- 0.03 Angstrom with the ring inclined by 26 +/- 5 degrees, On increasing coverage, thiophene undergoes a compressional phase transformation to a more weakly bound sulfur lone-pair-bonded species. In this new phase the thiophene still occupies an atop site but the Cu-S separation has increased by 0.2 Angstrom and the ring is now inclined at 44 +/- 6 degrees to the surface.