Coordination mode of cyclohex-1-enylolonium cation and bridging pyridyl derivatives as gem -diol chelates to rhenium(I) and (VII)

Rhenium(I) and (VII) complexes with cyclohex-1-enylolonium cation and bridging pyridyl derivatives are reported. Additionally, the CO-bridged pyridyl and their related compounds have shown interesting behaviour in their reactivity towards compounds containing two amino groups. The unusual cationic compound: (2,6-diaza-cyclohex-1-enylolonium)2-aza-benzoate (H 2 den), was isolated from the reaction mixture of 1,2-di(pyridin-2-yl)ethane-1,2-dione with propane-1,3-diamine in methanol. The latter ligand: H 2 den, was used in the synthesis of rhenium(I) complex in its reaction with [Re(CO) 5 Cl] that gave rise to novel rhenium(I) complex fac -[Re(CO) 3 (Hhdm)] ( 1 ). The surprising aspect in the formation of ( 1 ) is the modification of H 2 den which was stabilized into a coordinated six-membered pyrimidine ring, 1,4,5,6-tetrahydropyrimidin-2-yl)di(pyridin-2-yl)methanol (H 2 hdm) chelate. The derived ligand acts as a tridentate monoanionic N 2 ,O-donor ligand towards the fac -[Re(CO) 3 ] + core. Surprisingly, the 2-aza-benzoate counter-ion that was present in the used ligand is not displayed in the crystal structure of complex 1 , and might have been stabilized into 2-aza-benzoic acid (picolinic acid). The reaction of the potential tridentate N 2 ,O-donor ligand 2,2′-dipyridylketone (dpk) with trans -[ReOI 2 (OEt)(PPh 3 ) 2 ] led to the isolation of [ReO 3 (dpk·OH)] ( 2 ). The ligand H 2 den and the rhenium complexes were spectroscopically characterized, and the structures of H 2 den, 1 and 2 were established by X-ray diffraction.