The palladium-catalyzed alternating copolymerization of fluoroalkenes, represented as CH2= CH-CH2-CnF2n+1, with CO was performed using (R,S)-BINAPHOS (2e) as a ligand. The CH2-CnF(2n+1) group is the most electronegative substituent ever reported for the copolymerization (Taft's sigma* value of 0.90 for CH2CF3). The copolymer obtained from CH2=CH-CH2-C8F17 (1a) existed as a mixture of polyspiroketal and polyketone, while that from CH2=CH-CH2-C4F9 (1b) was a pure polyspiroketal, as was revealed by infrared and C-13 -CP/MAS NMR spectroscopies. The terminal structure of the polymer from 1b was confirmed by MALDI-TOF MS spectrometry. Detailed NMR studies suggested that the much higher reactivity with (R,S)-BINAPHOS (2e) than that with the conventional ligand DIPPP (2a) can be attributed to the unique 1,2-insertion of the fluoroalkene into acylpalladium species. The existence of an electronegative substituent on the a-carbon of the palladium center is successfully avoided in the 1,2insertion mechanism.