Chemistry of the azine phosphine ligand Z,E-PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4): crystal structure of [Mo(CO) 4{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4)}

Abstract

Condensation of Z-PPh 2CH 2C(Bu t)=NNH 2 with 4-nitroacetophenone gave the azine phosphine Z,E-PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4) ( I). The corresponding phsophine oxide II was prepared by treatment of I with H 2O 2. The phosphine I with [Mo(CO) 4(nbd)] (nbd=norbornadiene) gave [Mo(CO) 4{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4)}] ( 1a); the corresponding tungsten 1b and chromium 1c complexes were made similarly. The crystal structure of 1a was determined by X-ray diffraction and showed the presence of a six-membered chelate ring with the bulky 4-nitrophenyl group held close to the metal. Oxidation of 1a with bromine gave the seven-coordinate molybdenum (II) complex 2. Treatment of [PtMe 2(cod)] (cod=cycloocta-1,5-diene) with I at 20°C gave the dimethyl-platinum (II) complex [PtMe 2{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4)}] ( 3a) which with MeI gave the iodotrimethylplatinum(IV) complex 4. Treatment of 3a with C≡O opened the chelate ring to give the dimethyl(carbonyl)platinum(II) complex 5 containing a monodentate phosphine ligand. When 3a was heated in toluene solution at 110°C it gave the cyclometallated methylplatinum(II) complex [PtMe{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 3NO 2-4)}] ( 6). Treatment of 6 with MeI gave the platinum(IV) complex 7. The dichloropalladium(II) complex [PdCl 2{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 4NO 2-4)}] ( 3b) was prepared by treatment of [PdCl 2(NCPh) 2] with I in CH 2Cl 2. Treatment of [PtCl 2(NCMe) 2] with 2 equiv. of I gave the trans-bis(phosphine) complex 8. When 2 equiv. of I were treated with [PtCl 2(cod)] followed by NH 4PF 6 this gave the salt 9a containing two six-membered chelate rings; the analogous palladium(II) 9b) salt was also prepared. Treatment of 2 equiv. of I with [PtCl 2(cod)] followed by NH 4PF 6 gave the PF 6 salt 10 containing a six-membered chelate ring and a monodentate ligand. When 10 was treated with AgNO 3 followed by NH 4PF 6 this gave the bis-chelate complex 11 containing five- and six-membered chelate rings. Treatment of [IrCl(CO) 2( p-toluidine)] with I gave the cyclometallated iridium(III) hydride complex [IrHClCO{PPh 2CH 2C(Bu t)=N-N=CMe(C 6H 3NO 2-4)}] ( 12). [RuCl 2(PPh 3) 3] with the phosphine I resulted in the Ru(II) complex 13 in which the ortho hydrogens of the 4-nitrophenyl group are agostically interacting with ruthenium. Proton, Phosphorus-31, some carbon-13 NMR and IR data have been obtained. Crystals of 1a are orthorhombic, space group Pna2 1, with a = 1819.3(2), b = 1050.0(1), c = 1614.8(2) pm and Z = 4; final R = 0.0191 for 2616 observed reflections.