Conclusions

X-ray photoelectron and vibrational spectroscopies havebeen used tocharacterize an HCNH intermediate formed via nitro-gen-hydrogen bond formation in HCN on the W (100)-(5X1)-C surface. At 500 K, NH bond formation is observed in an HCNH intermediate with a greatly weakened CN bond. Atomic carbon and atomic nitrogen are also formed from decomposition of HCN to provide hydrogen for NH bond formation. HCNH is proposed to re-form gaseous HCN on further heatingto 650 K and decompose to atomic carbon and nitrogen. At 200 K, two species are thought to be present on the surface, one an end-bound HCN which forms-HCN at 450 K or forms the HCNH intermediate and a CN species (state) thought to be bound parallel to the surface which decomposes to form atomic carbon and nitrogen. Comparison to studies of acetonitrile on the same surface that also evidence NH bond formation shows general features of the bonding of nitriles to this surface.

Acknowledgment. This work was supported by a NSF-Presidential Young Investigator Award, No. CHE-8451307, and the Harvard Materials Research Laboratory, NSF DMR-80-20247. We thank R. J. Madix for the use of the high-resolution electron energy spectrometer.