(1) after purification in an isolated yield of 93%. The 13 C NMR spectrum of 1 shows highly distinctive resonances at 120.1, 115.9 and -13.2 ppm. This latter resonance with a negative chemical shift corresponds to the central carbon in the [NCCCO] -anion, and is significantly upfield shifted from the analogous signals in the aforementioned phosphorus-bound ketenate species (A, B, C, Scheme 1b) that resonate at 5.8, 2.4 and 36.2 ppm, respectively. The IR spectrum of 1 showed an absorption at 2176 cm -1 that corresponds to nitrile stretchν(CN), the carbonyl absorption band ν(CO) is found at 1462 cm -1 , while the ν(CCO) andν(CCN) are found at 2120 and 2242 cm -1 , respectively. However, it should be noted that due to the highly delocalized nature of the anion in 1, all the vibrational modes are highly concerted and not localized on one particular bond. In comparison, the ν(CCO) absorption band is found at 2086 and 2047 cm -1 in B and C, respectively. The observed red shifting of ν(CCO) in 1 presumably results from the reduction of bond order due to delocalization.