Having established optimal reaction conditions, we sought to isolate the ketenyl anion. Due to its lower solubility the 12-crown-4 complex of the sodium salt of 2 turned out to be most straightforward to purify and could be isolated as yellow solid in an excellent 92% yield. The ketenyl anion [2•(Na•(12-c-4)2)] is characterized by signals at 24.8 and 145.2 ppm in the 13 C{ 1 H} NMR spectrum for the C1 and C2 atom of the ketenyl moiety, which are closer to the values reported for IIb than for IIa (Table ). The C-C-O vibration of 2 in acetonitrile appears at 2074 cm -1 in the IR spectrum which is only slightly red shifted compared to the vibration reported for IIa (2086 cm -1 ) and blue-shifted compared to IIb (2047 cm -1 ), suggesting an intermediate bond strength. Single crystals of 2 were obtained by slow evaporation of a saturated DCM solution in the presence of 1 equiv. of [2.2.2]-cryptand (crypt) (Figure ). Due to the encapsulation of the sodium ion by the cryptand, a solvent-separated ion pair is formed. The same structure was observed for the crown-ether complex [2•(Na•(12-c-4)2)], yet of lower quality (see the Supporting Information). [2•(Na•crypt)] represents the first "free" ketenyl ion exhibiting no direct metalanion interaction in the solid state, which hence allows a discussion of the ketenyl structure without being disturbed by the counter cation. In contrast, the two structures reported for ketenyl anions until to date exhibit a direct interaction with the metal cation, either via the C1 carbon atom (IIa•crown) or via the oxygen atom (IIb) or both (IIa•THF)∞. ) and Table .