The combination of (i) quantitative LEED, infrared and STM structural analyses of complex adsorbate structures with (ii) SCAC (single crystal adsorption calorimetry) measurements of energetics, on the one hand, and state-of-the-art first principles DFT slab calculations of these systems on the other has provided a unique experimentally benchmarked approach to chemical bonding in structurally complex chemisorption systems.@footnote 1@ Of particular importance to reactivity in molecular systems at surfaces, this has given rise to the new concept of surface and promoter-induced molecular polarisation, and its relationship to stereo-electronically driven chemical reactivity in catalysis.@footnote 2@ The presentation will draw particularly on our recent results for CO + K coadsorption on Co{1010},@footnote 2-4@ C@sub 6@H@sub 6@ adsorption on Ni{111}@footnote 5@ and on Ir{100}@footnote 6@ and coadsorption with O, CO and NO on Ni{111}@footnote 7@ and anisole adsorption on Pt{110}.@footnote 8@ @FootnoteText@ @footnote 1@"Adsorption Energetics and Bonding from Femtomole Calorimetry and from First Principles Theory", Advances in Catalysis, 43 (2000) 207-259. @footnote 2@Q. Ge, R. Kose and D. A. King. "A Role for Induced Molecular Polarisation in Catalytic Promotion: CO Coadsorbed with K on Co{1010}", J. Am. Chem. Soc., 122 (2000) 10610-10614. @footnote 3@S. J. Jenkins and D. A. King. "Full Structure Determination of an Alkali Metal/CO Co-Adsorption Phase, for Co{1010} (2x2)-(K + CO)", Phys. Rev. B, 51 (1995) 17063-17067. @footnote 4@P. Kaukasoina, M. Lindroos, P. Hu, D. A. King and C. J. Barnes. "The Coadsorption of CO and K on Co{1010}", Surf. Sci., 349 (1996) 19-42. @footnote 5@R. L. Toomes and D. A. King "Realistic Molecular Distortions and Strong Substrate Buckling Induced by the Chemisorption of Benzene on Ni{111}", J. Chem. Phys, 105 (1996) 11305-11312. @footnote 6@G. Held, M. P. Bessent, S. Titmuss and D. A. King. "Benzene Adsorption on Ir{100} Studied by LEED I-V Analysis: Evidence for Formation of Tilted Benzyne", J. Chem. Phys., in press. @footnote 7@K. Johnson, B. Sauerhammer, S. Titmuss and D. A. King. S. Titmuss, D. A. King, to be published. @footnote 8@Y. P. Tan, S. Khatua, S. Jenkins and D. A. King, to be published.