Five-coordinate iron carbonyl complexes with fluorocarbon-bridged ligands

Abstract

P(OCeH5)3] with iodine in dichloromethane was shown by infrared spectroscopy to afford a third product in addition to x-C5H6Fe(CO)2I and x-C6H6Fe(CO)LI; these three compounds were formed in approximately equal amounts. When this iodination was performed in benzene, however, the unknown product separated out while trace quantities of x-CsH5Fe(CO)2I and x-CóH5Fe(CO)LI remained in the benzene solution. The precipitate was shown to be ionic and characterization of the tetraphenylborate derivative showed it to be [x-C5H6Fe(CO)2L]B(CeH6)4. The neutral compounds x-C5H6Fe(CO)LI were identified by comparing their infrared spectra with the spectra of authentic samples previously synthesized from x-C6H6Fe(CO)2l.2SThe physical and spectroscopic data for the ionic complexes are given in the tables. Conductivity data and spectroscopic evidence show, respectively, these derivatives to be 1:1 electrolytes in acetone and diamagnetic. The infrared spectra of these compounds in solution contain two peaks corresponding to C-0 stretching modes; the frequencies decrease with the increase of the over-all ( -) donor ability of the phos-(28) A. L. du Preez, M.S. Thesis, University of Pretoria.Inorganic Chemistry phorus donor ligand as expected. The single cyclopentadienyl proton resonance in the nmr spectra of these ionic compounds is split into a doublet due to phosphorus-hydrogen coupling. The coupling constant could only be measured for the compounds containing the ligands P(C2H3)3 and P(0-f-CsH7)3.The formation of both ionic and neutral compounds in the iodination of the monosubstituted derivatives demonstrates that this reaction occurs by at least two mechanistic pathways, one involving a symmetric cleavage and the other an asymmetric cleavage of the dinuclear parent. A similar scheme has been proposed for the halogenation of [x-C6HóFe(CO)2]2 on the basis of the isolation of [x-C6H6Fe(CO)3 ]X and x-CsHjFe-(CO)2X (X = halogen) from the reaction mixture.29Acknowledgments.-The authors express their gratitude to Dr. K. G. R. Pachler, National Chemical Research Laboratory, CSIR, Pretoria, South Africa, for the measurement of the nmr spectra. A. L. du P. thanks the South African Council for Scientific and Industrial Research and the University of Pretoria for financial support.

Monosubstituted Derivatives of (L–L)Fe2(CO)6 (L–L = fluorocarbon bridged ligand)

“…On the other hand, 6 of FeA is fairly sensitive to the nature of the ligand, being lowest for the f,fos derivatives and increasing when arsenic replaces phosphorus as the donor atom. This is the trend usually observed in similar iron carbonyl complexes (2,13) and reflects the fact that phosphines are better a-donors and 7c-acceptors than arsines (8).…”

“…The fluorocarbon-bridged ligands f.AsP (n = 4, 6), and f,,fos and f.fars (n = 4, 6, 8) were prepared using published procedures (2,5).…”

“…unique ability to form complexes of formula (L-L)Fe2(CO), in which the two group V donor atoms and the double bond of the bridging group are coordinated to the iron atoms (1,2). The solid state structure of f,far~Fe,(CO)~ (3) is seen in Fig.…”

The Preparation of Iron Carbonyl Complexes of Fluorocarbon-Bridged Ligands

“…A number of iron carbonyl derivatives of fluorocarbon-bridged ditertiary arsines and phosphines have been described in recent years (1)(2)(3)(4). Of special interest have been the complexes formed by f4fars and f4fos la and lb.…”

Fluorocarbon-bridged ditertiary phosphine derivatives of rhodium carbonyl halides

“…As part of our continuing study of the reactions of fluorocarbon-bridged ditertiary phosphines and arsines (4)(5)(6)(7)(8), 3, we have prepared a number of Rh(1) complexes which present some interesting parallels with and differences from earlier studies. Herein we report the results of this work.…”