Different coordinating behaviour of the imino-phosphoranes Ph3P = NC(O)CH2Cl and Ph3P = NC(O)-2-NC5H4 towards M-II complexes (M = Pd, Pt)

The coordination behaviour of the iminophosphorane ligands Ph3P=NC(O)CH2Cl and Ph3P=NC(O)-2-NC5H4 towards different Pd-II and Pt-II substrates has bee n explored. The iminophosphorane Ph3P=NC(O)CH2Cl shows a poor coordination ability, always binding through the iminic N atom. Thus, Ph3P=NC(O)CH2Cl re acts with PdCl2(NCPh)(2), [M((CP)-P-boolean AND)(NCMe)(2)]ClO4 (M=Pd, Pt) a nd CPd(dmba)(NCMe)(2)]ClO4 (2:1,1:1 and 1:1 molar ratio, respectively, (CP) -P-boolean AND=ortho-CH2C6H4P(o-Tol)(2)-C,P; dmba = C6H4CH2NMe2-2), resulti ng in the formation of trans-PdCl2{N(=PPh3)C(O)CH2Cl}(2), 1, [M((CP)-P-bool ean AND){N(=PPh3)C(O)CH2Cl}(NCMe)]ClO4 (M=Pd, 2; Pt, 3) and [Pd(dmba){N(=PP h3)C(O)CH2Cl}(NCMe)\ClO4, 4. However, the iminophosophorane Ph3P=NC(O)-2-NC 5H4 displays at least three different coordination modes, as a function of the starting material. The reaction of Ph3P=NC(O)-2-NC5H4 with PdCl2(NCPh)( 2) or PtCl2 (1:1 molar ratio) gives cis-Cl2M{N(=PPh3)C(O)-2-NC5H4} (M = Pd, 5; Pt, 6) in which the ligand acts as an N,N-chelate. The reaction with th e bis-solvate orthometallated complexes [M((CP)-P-boolean AND)(NCMe)(2)]ClO 4 (M=Pd, Pt) and [Pd(dmba)(NCMe)(2)]ClO4 (1:1 molar ratio) gives the bis-ch elate complexes [M((CP)-P-boolean AND)(NC5H4-2-C(O)N=PPh3}]ClO4 (M = Pd 7, Pt 8) and [Pd(dmba){NC5H4-2-C(O)N=PPh3}]ClO4, 9, in which the iminophosphor ane ligand is coordinated through the pyridinic nitrogen atom and the carbo nyl oxygen atom. The X-ray crystal structure of 9 has been determined. The reaction with [Pd(dmba)(PPh3)(THF)]ClO4 (1:1 molar ratio) gives the cationi c derivative [Pd(dmba)(PPh3){NC5H4-2-C(O)N= PPh3)]ClO4, 10, in which the im inophosphorane ligand is coordinated only through the pyridinic nitrogen at om. Finally, the iminophosphorane reacts with [Pd(mu-Cl)(dmba)](2) (2:1 mol ar ratio) resulting in the cleavage of the chlorine bridging system by the pyridinic n atom and formation of [Pd(dmba)Cl{NC5H4-2-C(O)N=PPh3}], 11.