C−N and C−C Coupling Reactions: Preparation of New N-Heterocyclic Ruthenium Derivatives

Abstract

Three novel types of complexes containing heterocyclic ligands are prepared by condensation of the allenylidene ligand of [Ru(η5-C5H5)(CCCPh2)(CO)(PiPr3)]BF4 (1) with propargylamines. Complex 1 reacts with propargylamine to give initially [Ru(η5-C5H5){C(CHCPh2)NHCH2C⋮CH}(CO)(PiPr3)]BF4 (2). Treatment of 2 with KOH in methanol affords the bicyclic derivative Ru(η5-C5H5){4-methylidene-6,6-diphenyl-2-azabicyclo[3.1.0]hex-2-en-1-yl}(CO)(PiPr3) (3). The formation of 3 takes place via the intermediate Ru(η5-C5H5){C(CHCPh2)NCH2C⋮CH}(CO)(PiPr3) (4), which is isolated when the deprotonation of 2 is carried out in tetrahydrofuran as solvent. In contrast to propargylamine, the addition of 1,1-diethylpropargylamine to 1 leads to the dihydropyridiniumyl derivative [Ru(η5-C5H5){2,2-diethyl-5-diphenylidene-2,5-dihydropyridinium-6-yl)(CO)(PiPr3)]BF4 (5) in a one-pot synthesis. Complex 1 also reacts with N-methylpropargylamine. The reaction affords [Ru(η5-C5H5){C(CHCPh2)N(CH3)CH2C⋮CH}(CO)(PiPr3)]BF4 (6). Treatment of 6 with sodium methoxide, at −78 °C, gives a 1:1 mixture of the dihydronaphthopyrrolyl diastereomers (RRuSC,SRuRC)-[Ru(η5-C5H5){9-phenyl-4,4a-dihydronaphtho[2,3-c]-1-pyrrolyl})(CO)(PiPr3) (7a) and (RRuRC,SRuSC)-[Ru(η5-C5H5){9-phenyl-4,4a-dihydronaphtho[2,3-c]-1-pyrrolyl})(CO)(PiPr3) (7b). Complexes 3 and 5 and the enantiomeric mixture 7a have been characterized by X-ray diffraction analysis.