Interconversion of metallabenzenes and cyclic η2-allene-coordinated complexes.
Treatment of the osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)]Cl (1) with excess 8-hydroxyquinoline produces monosubstituted osmabenzene [Os{CH C(PPh(3))CHC(PPh(3))CH}(C(9)H(6)NO)Cl(PPh(3))]Cl (2) or disubstituted osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}(C(9)H(6)NO)(2)]Cl (3) under different reaction conditions. Osmabenzene 2 evolves into cyclic η(2)-allene-coordinated complex [Os{CH=C(PPh(3))CH=(η(2)-C=CH(2))}(C(9)H(6)NO)(PPh(3))(2)]Cl (4) in the presence of excess PPh(3) and NaOH, presumably involving a P-C bond cleavage of the metallacycle. Reaction of 4 with excess 8-hydroxyquinoline under air affords the S(N) Ar product [(C(9)H(6)NO)Os{CHC(PPh(3))CHCHC}(C(9)H(6)NO)(PPh(3))]Cl (5). Complex 4 is fairly reactive to a nucleophile in the presence of acid, which could react with water to give carbonyl complex [Os{CH=C(PPh(3))CH=CH(2)}(C(9)H(6)NO)(CO)(PPh(3))(2)]Cl (6). Complex 4 also reacts with PPh(3) in the presence of acid and results in a transformation to [Os{CHC(PPh(3))CHCHC}(C(9)H(6)NO)Cl(PPh(3))(2)]Cl (7) and [Os{CH=C(PPh(3))CH=(η(2)-C=CH(PPh(3)))}(C(9)H(6)NO)Cl(PPh(3))]Cl (8). Further investigation shows that the ratio of 7 and 8 is highly dependent on the amount of the acid in the reaction.
State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China.
Ran
R
Lin
Jing
J
Zhao
Hanyu
H
Chen
Hong
H
Zhang
Haiping
H
Xia