Cyclometallated Derivatives of Palladium(II) with 1,4-Benzodiazepin-2-ones. Crystal Structure of (L-H)Pd(PPh3)Cl.CHCl3 (L = Prazepam: 7-chloro-1-cyclopropylmethyl-1,3-dihydro-5-phenyl-2H-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

The dimeric cyclometallated derivatives of palladium(II) [(L-H)PdCl]2, 3 (L = 1, Diazepam: 7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) and 4 (L = 2, Prazepam: 7-chloro-1-cyclopropylmethyl-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2 -one) react with triphenylphosphine to give the complexes (L-H)Pd(PPh3)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) angstrom. 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-degrees-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.