Synthesis and reactions of isocyanate and carbamoyl complexes of rhenium |
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Authors: | G La Monica S Cenini M Freni |
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Institution: | Istituto di Chimica Generale, C.N.R. Center, Via Venezian, 21, 20133, Milano Italy |
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Abstract: | Re(CO)2(NO)(PPh3)2 reacts with aroyl azides RCON3 (R = C6H5, p-CH3C6H4) in benzene to form isocyanate complexes of formula Re(CO)(NO)-(PPh3)2(RCONCO) (I). When the reaction is carried out in protic solvents such as ethanol, carbamoyl derivatives of formula Re(NCO)(NO)(PPh3)2-(CONHCOR) (II) are obtained, which give Re(NCO)(NO)(PPh3)2(CO)(NHCOR) when dissolved in chloroform, a terminal carbonyl ligand being formed from the carbamoyl group.I can be transformed into II by reaction with gaseous HCl, via Re(CO)-(NO)(PPh3)2 {C(OH)=NCOR}]+Cl- followed by anion exchange with NaN3. II reacts with mineral acids HX (X = Cl, BF4) to give amide derivatives of formula Re(NCO)(NO)(PPh3)2(CO)(NH2COR)]+ X- which when X = Cl can be easily transformed into Re(NCO)(NO)(PPh3)2(CO)Cl, the amide ligand being removed. Both the protonation reactions of I and II are reversible. IR and 1H NMR data of the new compounds and the mechanisms of formation of I and II are reported and discussed. |
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