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)(=C=C=CPh2)(CO) (PiPr3)]BF4 (1) with propargylamines. Complex 1 reacts with propargylamine to give initially [Ru(η5-C5H5)- {C(CH=CPh2)=NHCH2C≡CH}(CO)(Pi Pr3)]BF4 (2). Treatment of 2 with KOH in methanol affords the bicyclic derivative Ru(η5-C5H5){4-methylidene-6,6-diphenyl-2-az abicyclo[3.1.0]- hex-2-en-1-yl}(CO)(PiPr3) (3). The formation of 3 takes place via the intermediate Ru(η5- C5H5){C(CH=CPh2)=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(CH=CPh2)=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.