Synthesis of (indenylidene)phosphoranes - A novel class of ligand precursors for main-group and transition metal organometallics

IndPPh(2) (1) reacts with RCH2Br to form the phosphonium salts [RCH2P(Ph)(2)Ind]Br-+(-) (2: R = Ph; 3: R = C6F5) in high yields. Oxidation of 1 with H2O2 in THF proceeds smoothly to give the phosphane oxide IndP(O)Ph-2 (4). Dehydrobromination of 2 and 3 with NaH in THF yields the corresponding indenylidenephosphoranes C9H6=P(Ph)(2)CH2R (5: R = Ph; 6: R = C6F5). Further deprotonation of 6 with excess NaH results in formation of sodium 1-{[(pentafluorophenyl)methylidene]-diphenylphosphoranyl}indenide (7), isolated as a solvate with three THF molecules. A detailed NMR study of new ligand precursors and X-ray structure studies of 5 and 7 have been accomplished. A short F-->Na coordination contact in the molecular structure of 7 has been detected. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).