Reactions of phosphorus fluorides and ortho-carborane ditertiary aminophosphines

Abstract

Fluorophosphine bidentate ligands containing o-carborane as backbone can be prepared by the reaction of the lithium- o-carboranes and PF 2X derivatives to give only two species: the unsymmetrical (C 6H 5) 2P[B 10H 10C 2]PF 2 and the cyclic FP[B 10H 10C 2] 2PF, both in low yield. However, exchange of F and NMe 2 groups by use of PF 5 or PF 3 provides a facile way to produce several new fluorophosphines. Phosphorus pentafluoride forms solid adducts with the o-phosphino derivatives (C 6H 5) 2P[B 10H 10C 2]P(NMe 2) 2, (Me 2N) 2P[B 10H 10C 2]P(NMe 2) 2 and (C 6H 5) 2P[B 10H 10C 2]H. All the adducts contain a phosphorus-phosphorus bond as evidenced from i.r., NMR and stoichiometry. The stability of the adducts reflects the strength of the PP bond formed upon complexation. When suspensions or solutions of the adducts are heated they exchange F and NMe 2 groups and no redox occurs. The products (C 6H 5) 2P[B 10H 10C 2]P(F)NMe 2(I) and Me 2N(F)P[B 10H 10C 2]P(F)NMe 2(II) react further with PF 5 giving (C 6H 5) 2P[B 10H 10C 2]PF 2(III) and F 2P[B 10H 10C 2]PF 2(IV). The precursors also react with phosphorus trifluoride to produce only (I) and (Me 2N) 2P[B 10H 10C 2]P(F)NMe 2(V) regardless of the reaction conditions. All the products I–V have been identified by 1H, 19F, and 31P NMR and i.r. spectroscopy, mass spectrometry, and elemental analysis. The NMR spectra of the novel (IV) have been analysed as X 2AA 1X 1 2 spin system.