Allenylidene ligand of [Ru(η5-C5H5)(C=C=CPh2)(CO)(PPri3)]BF4 as entry to novel unsaturated η1-carbon ligands containing azetidine and hexahydroquinoline skeletons

The allenylidene complex [RU(eta(5)-C5H5)(C=C=CPh2)(CO)(PPr3i)]BF4 (1) reacts with dicyclohexylcarbodiimide to give the iminiumazetidinylidenemethyl complex [RU(eta(5)-C5H5){CH= CCPh2N(Cy)=C=N=C(CH2)(4)CH2}(CO)(PPr3i)]BF4 (2), as a 4:1 mixture of isomers Z (za) and E (2b). The structure of 2a was determined by an X-ray investigation, revealing a Ru-C distance of 2.070(4) Angstrom. Treatment of the isomeric mixture of 2 with sodium methoxide in tetrahydrofuran at room temperature affords the iminoazetidinylidenemethyl complex Ru- (eta(5)-C5H5){(Z)-CH=CCPh2N(Cy)C=NC=CH(CH2)(3)CH2}(CO)(PPr3i) (6), which reacts with HBF4. OEt2 to give [RU(eta(5)-C5H5){(Z)-CH=CCPh2N(Cy)C=N(H)C=CH (CH2)(3)CH2}(CO)(PPr3i)]BF4 (7), as a result of the protonation of the exocyclic nitrogen atom of the unsaturated eta(1)-carbon ligand of 6. In the solid state and in solution at low temperature, complex 7 is stable. However, in solution at room temperature, complex 7 evolves into [Ru(eta(5)-C5H5){(Z)CH=CCPh2C(CH2)(4)CN(H)=CNHCy}(CO)(PPr3i)]BF4(8), which reacts with sodium methoxide in tetrahydrofuran at room temperature to give the hexahydroquinolinylidenemethyl complex Ru(eta(5)-C5H5){(Z)-CH=CCPh2C(CH2)(4)CN=CNHCy}(CO)(PPr3i) (9), as a result of the deprotonation of the endocyclic nitrogen atom of 8. The structure of 9 was also determined by an X-ray investigation, revealing, in this case, a Ru-C distance of 2.113(4) Angstrom. The formation of the azetidine and hexahydroquinoline skeletons of the ligands of these compounds is discussed.