The nucleophilic hydrodefluorination of C3F 7 OCF=CF 2 with the complex hydrides Li[AlH 4 ], Li[BH 4 ] or Na[BH 4 ] proceeded non-stereoselectively and was accompanied by the formation of either cis- and trans-C 3 F 7 OCH=CFH and/or C 3 F 7 OCHFCF 2 H. The reaction of C 3 F 7 OCF=CF 2 with PBu 3 followed by treatment with BF 3 OMe 2 or BF 3 OEt 2 yielded [C 3 F 7 OCF=CFPBu 3 ] [BF 4 ] (cis and trans) and, probably, [f nms-Bu 3 PCF=CFPBu 3 ] [BF 4 ] 2 . The hydrolysis of the latter with pure water proceeded quickly while the former isomeric mixture formed the isomeric olefins C 3 F 7 OCF=CFH slowly. The usage of aqueous NaOH instead of water produced mainly trans-CHF=CHF. The metallation of C 3 F 7 OCF=CFH (cis:trans=45:55) to C 3 F 7 OCF=CFLi and its subsequent reaction with B(OMe) 3 and K[HF 2 ] gave the salt K[C 3 F 7 OCF=CFBF 3 ] in a different cis to trans ratio (25:75) with satisfactory yield.