Rhodium (I) complexes of the dppn ligand, 3,6-bis (2′-pyridyl) pyridazine and X-ray structure of [Rh (CO) (dppn) (PPh 3 ) ] (PF 6 )

Abstract The reaction of the 3,6-bis (2′-pyridyl) pyridazine (dppn) ligand, with one and two equivalents of [Rh (CO) 2 S n ] (PF 6 ) , (s = THF) , yields respectively the mononuclear complex [Rh (CO) 2 (dppn) ] (PF 6 ) 1 and the binuclear complex [Rh 2 (CO) 4 (dppn) ] (PF 6 ) 2 3. Furthermore, the reaction of 1 with PPh 3 results in a substitution reaction to give [Rh (CO) (dppn) (PPh 3 ) 2 ] (PF 6 ) 2. The unsaturated complex 3 reacts with the monodentate phosphine PPh 3 to yield a mixture of the known compound [Rh (CO) 2 (PPh 3 ) 2 ] (PF 6 ) and of the mononuclear [Rh (CO) (dppn) (PPh 3 ) ] (PF 6 ) 4, the crystal structure of which was established by X-ray diffraction. Moreover, 3 reacts with the bis (diphenylphosphino) methane (dppm) ligand in a 1 : 2 ratio to form the binuclear A-frame complex [Rh 2 (CO) 2 (dppn) ( μ -dppm) 2 ] (PF 6 ) 2 5. However, the reaction of 3 with excess dppm (1 : 4 ratio) gives the known complex [Rh (CO) (dppm) 2 ] (PF 6 ) 6.