Raman and infrared spectra are reported for the tungsten-methylidyne complex trans-W(drop CH)(PMe3)(4)Cl (1) and its deuterated isotopomers W(drop CD)(PMe3)(4)Cl (1-d(1)) and W(drop CH)(PMe3-d(9))(4)Cl (1-d(36)) The bands attributable to the vibrational modes of the W dropC-H fragment are clearly identified on the basis of their frequency shifts upon isotopic substitution: v(1)[v(C-H)] congruent to 2980 cm(-1) (1, 1-d(36)), 2,240 cm(-1) (1-d(1)); v(2)[v-W dropC)] congruent to 911 cm(-1) (1, 1-d(36)), 871 cm(-1) (1, 1-d(36)), 871 cm(-1) (1-d(1)); v(3)[lambda (W dropC-H)] = 788/755 cm(-1) (1), 642/611 cm(-1) (1-d(1)). These data and normal-coordinate calculations on both the W dropC-H and W(drop CH)P4Cl fragments of these compounds reveal that the W dropC stretch is negligibly coupled either to the C-H stretch or to motions involving the ancillary ligands; thus, for 1, the W dropC force constant given by the pseudodiatomic-oscillator approximation (5.945 mdyne,Angstrom (-1)) is within 2% of the best value from the normal-coordinate calculations (6.021 mdyne Angstrom (-1)). The W dropC stretching frequency is much smaller than those previously assigned for the M drop CR stretches of metal-alkylidyne complexes with larger R groups (R := Me, Ph; v congruent to 1270-1600 cm(-1)); normal-coordinate calculations on the general W dropC-B oscillator, where B is a dummy atom of variable mass, reveal that this disparity is the result of large mixing between v(W dropC) and v(C-B) for cases where B is heavier than and, in some cases, of mixing among v(W dropC) and internal vibrational modes of B. The W dropC force constant is consistent with the W dropC bond length, based on an empirical bond-distance/force-constant correlation for selected third-transition-series metal complexes. The relatively low C-H stretching frequency and force constant (5.207 mdyne Angstrom (-1)) are consistent with a C-H bond length that is longer than typical for an sp-hybridized carbon atom, suggesting that this bond is correspondingly rich in carbon p-orbital character.