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The complex [ReNCI,( PPh,),] reacts with the potentially bidentate 8-hydroxyquinoline (Hquin) and N-phenylsalicylideneimine (Hpsal), and potentially terdentate ligands di-2-pyridyl ketone and 2,6-bis( hydroxymethy1)pyridine (H,L) to form the products [ReOCl(quin),], [ReOCI,( PPh,) -(psal)], [ReOCI,{(C,H,N),C(O) (OH)}] and cis-[ReOCI,(PPh,)(HL)], respectively. The first three products are identical t o those isolated earlier by the reactions of trans-[ ReOCI,( PPh,),] with these ligands, while in the latter product the H L -ligand acts as a bidentate N.0--donor, spanning one axial (0trans to Re=O) and one equatorial co-ordination site. These reactions present an alternative synthetic route t o monooxorhenium(v) complexes. The complex cis-[ ReOCI,( PPh,) ( H L)] crystallizes in the orthorhombic space group P2,2,2, with cell parameters a = 10.01 9(3), b = 12.457(6), c = 19.53(1) A , U = 2436.5 A,, Z = 4, R = 0.059 and R' = 0.074 for 1330 reflections with F, > 40(F0).

The substitution kinetics of the complexes [Pt{4 -(o -CH 3 -Ph)-terpy} Cl]SbF 6 (CH 3 PhPtCl(Sb)), (ClPhPtCl), and [Pt{4 -(o -CF 3 -Ph)-terpy}Cl]SbF 6 (CF 3 PhPtCl), where terpy is 2,2 :6 ,2 -terpyridine, with the nucleophiles thiourea (TU), N,N -dimethylthiourea (DMTU), and N,N,N ,Ntetramethylthiourea (TMTU) were investigated in methanol as a solvent. The substitution reactions of the chloride displacement from the metal complexes by the nucleophiles were investigated as a function of nucleophile concentration and temperature under pseudo-first-order conditions using the stopped-flow technique. The reactions followed the simple rate law k obs = k 2 [Nu]. The results indicate that the introduction of substituents in the ortho position of the phenyl group on the ancillary ring of the terpy unit does influence the extent of π -backbonding in the terpy ring. This controls the electrophilicity of the platinum center, which in turn controls the lability of the chloro-leaving group. The strength of the electron-donating or -withdrawing ability of the substituents correlates with the reactivity of the complexes. Electron-donating