181129-77-1Relevant academic research and scientific papers
A new method of creating co-ordinative unsaturation: Synthesis and reactions of a reactive iridium(I) complex
Perera, Sarath D.,Shaw, Bernard L.,Thornton-Pett, Mark
, p. 3111 - 3119 (1996)
Treatment of [IrCl(CO)2(H2NC6H4Me-p)] with the azine diphosphine PPh2CH2C(But)=N-N=C(But)CH 2PPh2 1 in benzene gave the co-ordinatively saturated (18e) octahedral iridium(III) hydride [IrH(Cl)(CO)(PPh2CH=C(But)-N-N=C(But)CH 2PPh2}] 3 in which the P,N,P-terdentate diphosphine ligand had lost a hydrogen to give an ene-hydrazone backbone. On dissolution in methanol or ethanol, complex 3 immediately dissolved to give the isomeric but co-ordinatively unsaturated (16e) iridium(I) complex [Ir(CO){PPh2CH2C(But)=N-N=C(Bu t)CH2PPh2}]Cl 4a in which the P,N,P-terdentate ligand backbone contained an azine moiety. Complex 4a was readily converted to the corresponding PF6 salt 4b. On dissolution in dichloromethane or benzene 4a rapidly gave back 3. Treatment of 4b with acetylenes or olefins gave adducts [Ir(CO){PPh2CH2C(But)=N-N=FC(Bu t)CH2PPh2}L]PF6 in which L = MeO2CC≡CCO2Me 5a, HC≡CCO2Me 5b, MeN(O=C)CH=CHCO 8a, trans-MeO2CCH=CHCO2Me 8b, trans-EtO2CCH=CHCO2Et 8c, C2H4 8d or CH2=C=CH2 8c,8f. Proton NMR studies on the ethene adduct showed that the ethene ligand was rotating at ca. 20°C but at -40°C rotation had stopped. Allene gives a mixture of two isomeric adducts 8c and 8f. Complex 4b reacted with PhC≡CH in a different fashion to give the phenylacetylide hydride fac-[IrH(C≡CPh)(CO){PPh2CH2C(Bu t)=N-N=C(But)CH2PPh2}]PF6 6 which isomerised on heating to mer-[IrH(C≡CPh)(CO){PPh2CH2C(Bu t)=N-N=C(But)CH2PPh2}]PF6 7. Treatment of 4b with EtO2CN=NCO2Et gave an adduct [Ir(CO){PPh2CH=C(But)-N-N=C(But)CH 2PPh2}(EtO2CNHNCO2Et)]PF6 9 in which the diphosphine backbone had been deprotonated and the diethyl azocarboxylate protonated. Treatment of 4b with carbon monoxide gave the dicarbonyliridium complex [Ir(CO)2{PPh2CH2C(But)=N-N=Bu t)-CH2PPh2}]PF6 10. Treatment of 4b with dihydrogen gave a dihydridoiridium(III) adduct 11 in which the terdentate P,N,P diphosphine was in the fac arrangement. In solution 11 slowly isomerised over several hours to give a dihydride in which the terdentate P,N,P diphosphine was in the mer arrangement, i.e. the structure of the dihydride was 12. Complex 4b underwent other types of oxidative-addition reactions, i.e. with formic acid it gave the hydride mer-[IrH(O2CH)(CO){PPh2CH2C(Bu t)=N-N=C(But)CH2PPh2}]PF6 13, with methyl iodide the mer-methyliridium(III) adduct 14 and with bromine the mer-iridium(III) dibromide 15. The crystal structures of 5a and 8a were determined.
