Rhenium(Ill) and (V) complexes with schiff bases

Abstract

Some rhenium(V) complexes with Schiff base (S.B.) of the type cis or trans-ReOX 2(S.B.)PPh 3 and ReOX(S.B.) 2 (X = CI or Br and S.B. = N-methylsalicylideneiminate (Me-sal), N-phenylsalicylideneiminate (Ph-sal), half N,N′-ethylenebis(salicylideneiminate) (half sal 2en) or 8-hydroxyquinolinate(Oxine)) have been already published [1, 2]. In this note we report the results of the reactions between ReOX 2(S.B.)PPh 3 and dimethylphenylphosphine (PMe 2Ph). By reaction of cis or trans-ReOX 2(S.B.)PPh 3 with an excess (1:8) of PMe 2Ph in dry benzene Complex M.p. colour .μ(eff.) vRe=O vC=N vC-O vRe-X ReCl 2(Me-sal)(PMe 2Ph) 2 183 red 2.1 c ]1589 1297 308 ReBr 2(Me-sal)(PMe 2Ph) 2 204 red 2.0 1590 1289 ReCl 2 (Ph-sal)(PMe 2Ph) 2 207 red 2.1 1590 1288 310 ReBr 2(Ph-sal)(PMe 2Ph) 2 190 red 2.0 1588 1286 Re 2 Cl 4(sal 2en)(PMe 2Ph) 4 199 red 2.0 1605 1300 308 cis-ReOCl 2(Me-sal)PMe 2Ph 182 light green diam. 965 1610 1285 320, 292 trans-ReOCl 2(Me-sal)PMe 2Ph 179 dark green diam. 975 1609 1290 308 cis-ReOCl 2(Ph-sal)PMe 2Ph 229 bright green diam. 976 1600 1290 318, 273 cis-ReOCl 2(oxine)PMe 2Ph 274 dark green diam. 962 1316 329, 290 trans-ReOCl 2(oxine)PMe 2Ph 258 dark green diam. 974 1319 300 Re 20 2Cl 4(sal 2en)(PMe 2Ph) 2 241 emerald green diam. 960 1600 1285 321 the trans-ReX 2(S.B.)(PMe 2Ph) 2 complexes were obtained (save when S.B. = Oxine), with a reduction of rhenium from (V) to (III). The reaction goes through the formation of cis or trans-ReOX 2(S.B.)PMe 2Ph, according to the starting isomer, where the substitution of PPh 3 with PMe 2Ph is observed. ▪ The intermediate complexes were isolated only when the cis and trans-ReOCl 2(Me-sal)PPh 3, cisReOCl/(Ph-sal)/PPh 3, trans.Re 20 2Cl 4/(sal 2en)/(PPh 3) and cis and trans-ReOX 2(oxine)PPh 3 starting complexeswere used. The cis isomers, with the exception of the complexes with Oxine ligand, were collected only when the reaction was carried out at room temperature. We can notice that the substitution of PPh 3 keeps the conformation unchanged. When 8-hydroxyquinolinate complexes are used only the substitution occurs and the reduction of rhenium involves the leaving of this ligand and the formation of the known ReX 3(PMe 2Ph) 3 complexes. The reduction occurs with all the other complexes, even though the reaction time is very different according to the compound symmetry and, with subordinate importance, to the used Schiff base. Cis derivatives in general react very easily in respect to trans analogues as well as Ph-sal complexes in respect to the sal 2en or Me-sal analogues. It is important to notice that both cis and trans rhenium(V) complexes give rise to reduced complexes with the same trans configuration. The characterization of all the complexes was performed by elemental analysis, magnetic susceptibilitymeasurements in solid and in solution, i.r. spectra. In Table I some general properties and important i.r. frequencies are reported.