Cyclometallated derivatives of palladium(II) with 1,4-benzodiazepin-2-ones. Crystal structure of ( L-H)Pd(PPh 3)Cl·CHCl 3 ( L = Prazepam: 7-chloro-1-cyclopropylmethyl-1,3-dihydro-5-phenyl-2 H-1,4-benzodiazepin-2-one). Synthesis of isoindolo[2,1-d][1,4]benzodiazepine derivatives by reaction of [( L-H)PdCl] 2 species with carbon monoxide

Abstract

The dimeric cyclometallated derivatives of palladium(II) [( L-H)PdCl] 2, 3 ( L = 1, Diazepam: 7-chloro-1,3-dihydro-1-methyl-5-phenyl-2 H-1,4-benzodiazepin-2-one) and 4 ( L = 2, Prazepam: 7-chloro-1-cyclopropylmethyl-1,3-dihydro-5-phenyl-2 H-1,4-benzodiazepin-2-one) react with triphenylphosphine to give the complexes ( L-H)Pd(PPh 3)Cl, 5( L = Diazepam) and 6 ( L = Prazepam). The crystal structure of 6 was determined by X-ray crystallography. The palladium atom is in a square planar arrangement. The deprotonated ligand is bound to the metal through the 4-nitrogen and the ortho-carbon atom of the 5-phenyl substituent. The phosphorous and the chlorine atoms are trans to the nitrogen and the carbon atoms, respectively: PdN = 2.085(2), PdP=2.263(1), PdCl = 2.377(1), PdC = 2.009(3) Å. The reaction of the dimeric derivatives [( L-H)PdCl] 2 with carbon monoxide was investigated. Under mild conditions (1 atm of CO, room temperature) the unstable ( L-H)Pd(CO)Cl derivatives. 7 ( L = Diazepam) and 8 ( L = Prazepam) are formed, but at high pressure and temperature (60–100 atm of CO, 45–50°C), extrusion of palladium occurs and tetracyclic derivatives having an isoindolo ring condensed on the 1,4-benzodiazepin-2-one system, 9–12, are obtained.