Dialkylaminofluorophosphine complexes of rhodium(I)

Abstract

Diethylaminodifluorophosphine, PF2NEt2, forms dimeric, halogen-bridged rhodium(1) complexes [RhX(PF2NEt2)2]2 (X = C1 or I) which react reversibly with an excess of the ligand to give non-ionic, five-coordinate complexes RhX(PF2NEt2)4. Dimethylaminodifluorophosphine, PF2NMe2, forms analogous complexes but, in contrast with diethylaminodifluorophosphine, the complex RhC1(PF2NMe2), decom- poses thermally to give initially an isolable tris complex RhC1(PF2NMe2),, which has no known counterpart in CO or PF, chemistry. The tris-complex decomposes thermally to give [RhC1(PF2NMe2),l2. Bis(dimethylamino)fluorophosphine, PF(NMe&, forms a tris complex, RhCl{PF(NMe2)2)3, but a dimeric bis-ligand complex could not be isolated. In contrast with tertiary phosphines and phosphites, the fluorophosphines do not form ionic rhodium(1) species. Monomeric derivatives such as R ~ ( ~ C ~ C ) ( P F ~ N E ~ ~ ) ~ , Rh(C5H5)(PF2NEt2)2, RhC1(PF2NEt2)(PPh3), and RhC1(PPh3)(PF2NEt2)2 have been prepared. The complexes [RhCl(CO)2]2 and [RhC1(PF2NEt2)2] undergo ligand redistribution on mixing, the product consisting mainly of [RhC1(CO)(PF2NEt2)]2. 19F n.m.r, data are reported and used inter aha to show that R ~ ( ~ C ~ C ) ( P F ~ N E ~ ~ ) ~ , but not Rh(C5H5)(PF2NEt2)2, exchanges rapidly with free PF2NEt2, and that, in RhC1- (PPh3)(PF2NEt2)2, the fluorophosphine ligands are mutually cis. Bands in the infrared arising from P-F vibrations are reported and discussed. The dialkylaminofluoro- phosphines appear to be poorer n-acceptors and/or better o-donors than PI?, but are better n-acceptors than phosphites.