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Preparation and Characterization of 4-Azoniaheptatrienyl, 4-Azaheptatrienyl, Ruthenapyrrolinone, and Pyrrolinyl Complexes of Ruthenium

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journal contribution
posted on 08.12.2003, 00:00 by María L. Buil, Miguel A. Esteruelas, Ana M. López, Enrique Oñate
The allenylidene complex [Ru(η5-C5H5)(CCCPh2)(CO)(PiPr3)]BF4 (1) adds the N−H bond of diallylamine to afford the N-allyl-4-azonia-1,3,6-heptatrienyl derivative [Ru(η5-C5H5){C(CHCPh2)N(CH2CHCH2)2}(CO)(PiPr3)]BF4 (2). Treatment of 2 with sodium methoxide in tetrahydrofuran produces the deprotonation of the NCH2 group of one of the allyl groups and the formation of a 1:1 mixture of the ruthenapyrrolinone complex (RRu,RC- (3) and the pyrrolinyl compound (RRu,SC- (4). Protonation of 4 with HBF4·OEt2 in diethyl ether initially leads to the heterocyclic derivative (RRu,SC- (5), containing a C−N double bond. In dichloromethane, complex 5 is unstable and evolves into the N-allyl-4-azonia-1,3,5-heptatrienyl complex [Ru(η5-C5H5){C(CHCPh2)N(CHCHCH3)CH2CHCH2}(CO)(PiPr3)]BF4 (6). The process involves the opening of the five-membered heterocycle and a proton transfer from the −CH2CN− group to the CH2 carbon atom of the vinyl substituent of the heterocycle. Complex 1 also reacts with allylamine. The reaction leads to the 4-azonia-1,3,6-heptatrienyl derivative [Ru(η5-C5H5){C(CHCPh2)NH(CH2CHCH2)}(CO)(PiPr3)]BF4 (7). In contrast to 2, the deprotonation of 7 with sodium methoxide in tetrahydrofuran takes place at the nitrogen atom. In toluene at 70 °C, the resulting 4-aza-1,3,6-heptatrienyl complex Ru(η5-C5H5){C(CHCPh2)NCH2CHCH2}(CO)(PiPr3) (8) isomerizes into the conjugated 4-aza-1,3,5-heptatrienyl derivative Ru(η5-C5H5){C(CHCPh2)NCHCHCH3}(CO)(PiPr3) (9), as a result of a 1,3-sigmatropic rearrangement in the allyl unit. Complexes 3, 4, 5, and 9 have been characterized by X-ray diffraction analysis.