The Chemistry Of Spin-Coated Rhodium-Ferrocenyl Complexes Supported On Silanol-Capped Silicon Wafers

A series of rhodium beta-diketonato complexes [Rh(FcCOCHCOR)(CO)(2)] and [Rh(FcCOCHCOR)(CO)(PPh3)] with R = CF3, CH3, Ph = C6H5 and Fc (ferrocenyl = Fe-II(C5H5)(C5H4)) were spin-coated on two-dimensional silanol-functionalised silicon wafers. Chemical reactions were observed that do not occur in ethanol solutions. Si-OH fragments on the wafers substituted ligands and oxidatively added to the Rh(I) centres. A multitude of different surface species could be identified with X-ray photoelectron spectroscopy (XPS). These included the parent spin-coated rhodium(I) complexes and rhodium(I) species that resulted from b-diketonato displacement from parent rhodium complexes by surface silanol OH's to generate [wafer-(O)(2)-Rh-(CO)(2)](circle minus) and [wafer-(O)(2)-Rh-(CO)(PPh3)](circle minus) units. Several Rh-III surface species that inter alia resulted from oxidative addition of surface Si-OH groups to surface-coordinated RhI core atoms were also identified. Efficacy of beta-diketonato ligand substitution by the silanol surfaces is a kinetically driven process and can be related to the rate of solution-phase beta-diketonato substitution by 1,10-phenanthroline from parent [Rh(FcCOCHCOR)(CO)(2)] and [Rh(FcCOCHCOR)(CO)(PPh3)] complexes. The binding energies of the Rh-I and Rh-III 3d(5/2) photoelectron lines were found to be functions of Gordy scale R-group electronegativities and they are also linearly related to electrochemically determined RhI oxidation potentials. (C) 2021 Elsevier Ltd. All rights reserved.