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

The surface chemistry of trimethylphosphite (CH3O)(3)P has been studied on Cu(111) and Ni(111) surfaces in order to model the initial steps in the rea ctions of vapor phase lubrication by organophosphorus compounds. The initia l reactions involve scission of the P-O bonds to deposit methoxy groups (CH 3O(ad)) on the surfaces. On the Cu(111) surface the formation of CH3O(ad) s pecies occurs only after oxidation of the surface. The CH3O(ad) groups on C u(111) decompose by beta-hydride elimination to produce formaldehyde (O=CH2 ) and adsorbed hydrogen. CH3O(ad) groups are formed from (CH3O)(3)P on the clean Ni(111) surface and decompose by complete dehydrogenation to CO and a dsorbed hydrogen atoms. This chemistry is very similar to that observed for CH3OH on these surfaces. These results suggest that alkoxides are importan t intermediates in the decomposition of vapor phase lubricants on metal sur faces.