Molecular Routes to Metal−Carbides, −Nitrides, and −Oxides. 3. 1 Chemical Vapor Deposition Employing X 3 W⋮*CCMe 3 , Where X = CH 2 CMe 3 , O t Bu, and O t Bu- d 9 and *C = 12 C or 13 C, and a Comparison with the Chemistry of ( t BuO) 3 W⋮N

Low-pressure (10 - 3 Torr) chemical vapor deposition (LPCVD) employing a hot-walled quartz reactor (300−360 °C) and silica/quartz or silicon substrates have been carried out with X 3 W⋮*C t Bu, where X = CH 2 CMe 3, O t Bu, and OBu t - d 9 and *C = 12 C and 13 C. Thin films formed on SiO 2 or Si have been examined by XPS, RBS, XRD, SEM, and SIMS. The volatile components evolved under the LPCVD conditions were trapped in an N 2 (l)-cooled U-tube packed with glass beads and examined by GC−MS and 1 H and 13 C NMR spectroscopy. Gray-black reflective films of amorphous tungsten carbide were formed (320−360°C), when X = Me 3 CCH 2, contaminated with 5−9 atom % oxygen. The 12 C: 13 C ratio in the film was ca. 7:1, and the volatile components were Me 4 C, Me 3 C 13 CH 3 (54 mol % combined), Me 2 C CH 2 (35 mol %), Me 3 C 13 C⋮CCMe 3 (6 mol %), and Me 3 C 13 CH CHCMe 3 (5 mol %) for the LPCVD employing the 13 C-labeled alkylidyne carbon. Films grown from ( t BuO) 3 W⋮CCMe 3 were WO 2 (determined by XRD after annealing) contaminated with some carbon. The volatile components were Me 2 C CH 2 (45 mol %), t BuOH (38 mol %), and Me 4 C (5 mol %), together with Me 3 CC⋮CCMe 3, Me 3 CCH CHCMe 3, and Me 3 CCH 2 CH 2 CMe 3 (totaling ca. 10 mol %). Reactions employing ( t Bu- d 9 O) 3 W⋮CC(CH 3 ) 3 yielded perdeuterated isobutylene and tert -butyl alcohol together with (CH 3 ) 3 CCD 3, (CH 3 ) 3 CCD CDC(CH 3 ) 3, and (CH 3 ) 3 CCD 2 CD 2 C(CH 3 ) 3 . Reactions employing ( t BuO) 3 W⋮N were less clean because the precursor was less volatile and it decomposes with sublimation. Nevertheless, the films obtained were predominately WO 2 contaminated with small amounts of C and N (<4%), and the volatile components revealed the presence of NH 3, isobutylene, and t BuOH. Collectively these results show that the metal−ligand multiple bond is labile to hydrogen-transfer reactions, which may lead to loss of the W⋮X atom. In the case of WC formation, the elimination of Me 3 CC⋮CCMe 3 and Me 3 CCH CHCMe 3 implicate surface chemistry involving C−C coupling of alkylidyne and alkylidene ligands.