Reactions of dihalogenotriorgano-phosphorus, -arsenic and -antimony compounds with [Fe2(CO)9]. Single-crystal structures of the iron(III) complexes [(Ph3PO)2H][FeBr4] and [Ph4Sb][Fel4]·Ph3Sbl2and of [Fe(CO)3(Ph3P)2

Abstract

The reaction of [Fe2(CO)9] with compounds of stoichiometry R3EX2[R3E = Ph3P, (p-MeOC6H4)3P, Me2PhP, Me3As or Ph3Sb, X = I; R3E = Ph3P, Ph3As or Me3As, X = Br] has been investigated and shown to yield diverse products. A series of complexes with the ionic structure [R3EX][Fe(R3E)X3][E = P, R3= Ph3, Me2Ph or (p-MeOC6H4)3, X = I; R3E = Me3As; X = I or Br] has been obtained. The reaction of [Fe2(CO)9] with Ph3PBr2 and Ph3AsBr2, however, resulted in the formation of the iron(III) complexes [(Ph3E)2Br][FeBr4]. Hydrolysis of [(Ph3P)2Br][FeBr4] by trace quantities of water produces [(Ph3PO)2H][FeBr4], the crystal structure of which has been determined. Triphenylantimony diiodide reacted with [Fe2(CO)9] yielding the surprising ionic adduct [Ph4Sb][FeI4]·Ph3SbI2, remarkable not only for the phenyl migration at the antimony atom, but also for the formation of the rare [FeI4]– anion from a zerovalent iron carbonyl complex. The reaction of [Fe2(CO)9] with the milder diphosphine tetraiodide, I2Ph2PCH2CH2PPh2I2, produced [Fe(CO)3(Ph2PCH2CH2PPh2)I][I3], a complex in which three CO ligands are retained.