Charles J. Cameron

The reactions of K2ReX6 (X = Br OR I) and Re3X9 (X = Cl, Br OR I) with alkyl and aryl isocyanides

Abstract The reactions of alkyl isocyanides (RNC) and aryl isocyanides (ArNC) with the rhenium halides K2ReX6 (X = Br or I) and Re3X9 (X = Cl, Br or I) have been investigated. When the K2Rex6 salts are treated with neat isocyanide at room temperature, or with isocyanide ligands in polar solvents under reflux conditions, then the homoleptic isocyanide cations [Re(CNR)6]+ or [Re(CNAr)6]+, are isolated. Under less forcing conditions, various rhenium(III) and rhenium(I) species, e.g. [Re(CNCMe3)5I2]+ and Re(CNAr)5I, which may be considered as intermediates on the way to the formation of the homoleptic species, can be obtained. The rhenium(I) complexes Re(CNAr)5I3, which are believed to contain the coordinated triiodide ligand, have also been isolated and characterized. One route to these complexes is through the reaction of Re(CNAr)5I with I2. Reactions of the trinuclear halides Re3X9 (X = Cl, Br or I) with alkyl isocyanides at room temperature are found, in all instances, to provide adducts of the type Re3X9(CNR)3. Under reflux conditions, Re3Cl9 and Re3Cl9(PEtPh2)3 react with Me3CNC to fom products of cluster disruption, viz. [Re(CNCMe3)6]+ and [Re(CNCMe3)4(PEtPh2)2]+, respectively. The spectroscopic and electrochemical properties of complexes derived in this study are reported. These results are compared with those reported previously by Freni et al.

The vibrational spectra of the homoleptic isocyanide complexes [Re(CNR)6]PF6, (R = Me, Ph, and 4-MeC6H4)

Abstract Raman and infrared spectra of the complexes [Re(CNR) 6 ]PF 6 (R = Me, Ph, and 4-MeC 6 H 4 ) have been obtained in the solid state and in solution. Fundamental vibrations have been assigned on the basis of local O h symmetry for the Re(CNC) 6 skeletons and for the PF 6 − anions. The methyl and phenyl internal modes of the methyl isocyanide and phenyl isocyanide complexes have been assigned in terms of C 3 v and C 2 v symmetry, respectively. The Raman-active ν(N≡C) bands of the complexes have anomalous relative intensities, the E g bands being considerably more intense than the bands assigned to the totally symmetrical A 1g vibrations. Although this feature has been reported for metal carbonyls, it has not previously been mentioned for metal isocyanide complexes.

Redox Reactions Of Polyhydride Complexes of Rhenium: electrochemistry and Reactions With Alkyl Isocyanides

The dark red octahydride complex of dirhenium, Re2H8(PPh3)4, undergoes a reversible one-electron oxidation to the blue mono-cation [Re2H8(PPh3)4]+ (Ebuit;12 −0.24 V vs. SCE by cyclic voltammetry). The X-band ESR spectrum of a dichloromethane glass (−160°C) containing the monocation is in accord with the HOMO being a delocalized metal-based orbital. Treatment of the heptahydrides ReH7(PR3)2 (PR3 = PPh3 or PEtPh2) with C6H11NC or Me3CNC in the presence of KPF6 leads to the elimination of hydrogen and the formation of [Re(CNR)4(PR3)2]PF6. Electrochemical oxidation of ReH5(PPh3)2L (L = PPh3, PEt2Ph, pyridine, piperidine or cyclohexylamine) activities these molecules to attack by RNC to afford rhenium(I) species

Formation of mononuclear and dinuclear halide complexes of rhenium from reactions of the polyhydrides Re2H8(PR3)4 and ReH7(PR3)2 with allyl halides and other halogen-containing reagents

H2, and propene by allyl chloride. The dinuclear core of Re2H8(PPh3), is preserved upon reaction with allyl chloride and bromide to give the quadruply bonded dirhenium species (Ph3PC3H5)2Re2X8 (X = C1 or Br) plus H2 and propene. In contrast to this, the reaction with allyl iodide results in the cleavage of the Re-Re bond and the formation of (Ph3PC3H5)2Re16. The mononuclear polyhydride complex ReH7(PPh3)2 also reacts with the chlorocarbons CCl,, CHCl,, CH2C12, Me3CC1, and C6H5Cl to produce tr~nr-ReCl,(PPh,)~ with the concomitant evolution of H2 and some hydrocarbons. The treatment of Re2H8(PPh3), with gaseous hydrogen chloride in methanol is unusual in that crystals of the mixed rhenium(II1)-rhenium(1V) salt (Ph3PH)2Re&186(Ph3PH)ReC15(PPh3) are formed. The course of these reactions is discussed, and the properties of the rhenium-containing complexes are described.

The conversion of quadruply bonded dirhenium(III) complexes to mononuclear pentakis(isocyanide) complexes of the type Re(CNAr)5X (Ar = 2,4,6-Tri-t-butylphenyl and X = C1 or Br)

Preparation et caracterisation du complexe Re(CNAr) 5 X. Spectrometrie IR et RMN, voltammetrie cyclique