C-H AND C-CL BOND ACTIVATION IN THE FORMATION OF CYCLOMETALATED PLATINUM(II) AND PLATINUM(IV) COMPOUNDS WITH CHLORINATED N-BENZYLIDENEBENZYLAMINES

Platinum substrate [Pt(2)Me(4)(mu-SMe(2))(2)] (1) reacts with chlorina ted imines 3,5-Cl2C6H2CH=NCH2C6H5 (2a) and 3-ClC6H4CH=NCH2C6H5 (2b) to yield cyclometallated platinum(II) compounds [PtMe(3,5-Cl2C6H2CH=NCH2 C6H5)(SMe(2))] (4a) and [PtMe(3-ClC6H3CH=NCH2C6H5)(SMe(2))] (4b), aris ing from C-H bond activation followed by loss of methane. A reaction i ntermediate [PtMe(2)(3,5-Cl2C6H3CH=NCH 2C6H5)(SMe(2))] (3a) was detect ed by H-1 NMR. The reaction of [Pt(2)Me(4)(mu-SMe(2))(2)] (1) with chl orinated imine 2,4-Cl2C6H3CH=NCH2C6H5 (2c) produces a mixture of-cyclo metallated platinum(II) compound [PtMe(2)Cl(4-ClC6H3CH=NCH2C6H5)(SMe(2 ))] (4c) and cyclometallated platinum(IV) compound [PtMe(2)Cl(4-ClC6H3 CH=NCH2C6H5)(SMe(2))] (4c') arising respectively from aryl C-H and ary l C-Cl bond activation. The reaction of complex 4a with triphenylphosp hine produces metallacycle cleavage and [PtMe(3,5-Cl2C6H2CH=NCH2C6H5)( PPh(3))(2)] (5a) is formed with the imine acting as a [C-] unidentate ligand. 5a crystallizes in the monoclinic space group P2(1)/n with a = 10.899(5) Angstrom, b,= 22.953(5) Angstrom and c = 17.588(9) Angstrom , beta = 95.14(5)degrees and Z = 4. Compounds 4b, 4c and 4c' react wit h PPh(3) to give cyclometallated compounds [PtMe(3-ClC6H3CH=NCH2C6H5)( PPh(3))] (5b), PtMe(2,4-Cl2C6H2CH=NCH2C6H5)(PPh(3))] (5c), and [PtMe(2 )Cl(4-ClC6H3CH=NCH2C6H5)(PPh(3))] (5c') respectively. The stereo-elect ronic effect of chlorine substituents, as well as the NMR parameters, are discussed in relation to the observed reactivity of these compound s.