Reaktionen von mit Alkyl-Grignardreagenzien: Ein einfacher Weg zu Carbonyl(olefin)osmium(0)-Komplexen

Article abstract of DOI:10.1016/0022-328X(92)83150-G

From <(Mes)Os(CO)Cl2> (2) and RMgX, both dialkylosmium(II) complexes <(Mes)OsR2(CO)> (7: R = C2H5; 10: R = n-C3H7; 12: R = i-C3H7; 14: R = n-C4H9) and alkyl(halogeno)osmium(II) derivatives <(Mes)OsR(CO)X> (6: R = C2H5, X = I; 9: R = n-C3H7, X = I; 11: R = i-C3H7, X = I; 15: R = n-C4H9, X = I; 16: R = CH2CH2Ph, X = Br) have been prepared.It is shown that the type of Grignard reagent has a significant influence on the course of the reaction: whereas from 2 and i-C3H7MgI, besides the diiodo compound <(Mes)Os(CO)I2> (8) only the alkyl(iodo) complex 11 is formed, the corresponding reaction of 2 with i-C3H7MgX leads predominantly (X = Br) or exclusively (X = Cl) to the formation of the bis(isopropyl) derivative 12.Stepwise treatment of <(Mes)OsR(CO)X> (6, 9, 11, 15, 16) with AgBF4 and Al2O3 gives the carbonyl(olefin)osmium(0) complexes <(Mes)Os(CO)CH2=CHR)> (4; R = H; 13: R = CH3; 17: R = C2H5; 18: R = C6H5) in good to excellent yields.For 13, 17 and 18, a mixture of exo/endo isomers is obtained.Compounds 13 and 17 have also been prepared by hydride abstraction from <(Mes)Os(CH3)(C2H5)(CO)> (19) or 7 with PF6, followed by deprotonation of the hydrido(olefin)osmium cation <(Mes)OsH(CH2 = CHR)(CO)>⁺ with either NaH or basic Al2O3.