Carbon–fluorine bond cleavage as a route to hybrid ligands

Abstract

Intramolecular CF bond cleavage provides a convenient, high yield route to metal complexes of hybrid cyclopentadienyl-phosphine ligands. On treatment with proton sponge the complexes [Cp ∗RhCl{(C 6F 5) 2PCH 2CH 2P(C 6F 5) 2}]BF 4 and [Cp ∗RhCl{(C 6F 5) 2PC 6H 4SMe-2}]BF 4 undergo dehydrofluorinative CC coupling to give the complexes [{η 5,η 1,η 1-C 5Me 3[CH 2C 6F 4P(C 6F 5)CH 2] 2-1,3}RhCl]BF 4 and [{η 5,η 1,η 1-C 5Me 4CH 2C 6F 4P(C 6F 5)C 6H 4SMe-2}RhCl]BF 4 rapidly and in quantitative yield. The reaction between [Cp ∗RhCl{PPh 2(C 6F 5)}(CNR)]BF 4 (R=phenyl or cyclohexyl) and proton sponge produces [(η 5,η 1-C 5Me 4CH 2C 6F 4PPh 2)RhCl(CNR)]BF 4, but is far slower and much less clean than for the complexes of the chelating ligands. The neutral complex [Cp ∗RhCl 2{PPh 2(C 6F 5)}] undergoes no reaction with proton sponge. The proposed mechanism involves initial formation of an η 4-fulvene complex, and subsequent nucleophilic attack (S NAr) at an ortho-CF bond.