Initial steps in the surface chemistry of vapor phase lubrication by organophosphorus compounds

Abstract

The surface chemistry of trimethylphosphite (CH3O)3P has been studied on Cu(111) and Ni(111) surfaces in order to model the initial steps in the reactions of vapor phase lubrication by organophosphorus compounds. The initial reactions involve scission of the P–O bonds to deposit methoxy groups (CH3O(ad)) on the surfaces. On the Cu(111) surface the formation of CH3O(ad) species occurs only after oxidation of the surface. The CH3O(ad) groups on Cu(111) decompose by β‐hydride elimination to produce formaldehyde (O=CH2) and adsorbed hydrogen. CH3O(ad) groups are formed from (CH3O)3P on the clean Ni(111) surface and decompose by complete dehydrogenation to CO and adsorbed hydrogen atoms. This chemistry is very similar to that observed for CH3OH on these surfaces. These results suggest that alkoxides are important intermediates in the decomposition of vapor phase lubricants on metal surfaces.