The one-step reaction of KReO 4 with benzoylhydrazine in the presence of concentrated HCl and PPh 3 afforded [Re V (NNC(Ph)O)(PPh 3 ) 2 Cl 2 ] 1 which was converted with carbon monoxide into the dinitrogen Re() complex [ReN 2 (CO) 2 (PPh 3 ) 2 Cl] 2 in good yield. A new class of ligands, of general formula HL n (n = 1-5), was obtained by conjugation of N-protected amino acids and benzoic acid with 2-aminothiazole. Complex 2 reacted with HL n to give neutral Re() chelate complexes [Re(L n )(CO)(PPh 3 ) 2 Cl] 5-9 (n = 1-5), by substitution of N 2 and CO groups. The molecular structure of complex 9 was determined by X-ray diffraction. When reactions between [Re(NNC-(Ph)O)(PPh 3 ) 2 Cl 2 ] 1 and HL n (n = 2, 5) were carried out in different stoichiometric ratios, neutral mono-and di-substituted Re() organodiazenido complexes [Re(NNCOPh)(L 2,5 )(PPh 3 ) 2 Cl] 10, 11 and [Re(NNCOPh)(L 5 ) 2 -(PPh 3 )] 12 were obtained. In these complexes the organodiazenido Re-N-N moiety adopts a linear conformation, as has been authenticated by X-ray diffraction analysis for 11 and 12. Treatment of Re() dinitrogen precursors [ReN 2 (P) 4 Cl] (P = PMe 2 Ph, 3 and PMePh 2 , 4) with ligands resulted in interesting dinuclear oxo-(µ-oxo)-Re() species [Re 2 (O) 3 (L n ) 2 (P) 2 ] (P = PMe 2 Ph, n = 1, 13; n = 2, 14; n = 4, 15. P = PMePh 2 , n = 2, 16). Suitable crystals for an X-ray analysis have been obtained for complex 14. The structure represents one of the few cases where, for steric reasons, the Re-O-Re bridging unit is not linear but rather bent. All the compounds have been characterized by elemental analyses, IR and NMR spectroscopy. The Re() complexes 5-7 and 9 were further characterized by electrochemical measurements.
The reaction of the newly synthesized aqua complex [Pt(terpy)(OH 2 )][BF 4 ] 2 with S-methyl 3-acyl-2-methyldithiocarbazates under a variety of experimental conditions has been studied. Using a 2 : 1 metal to ligand ratio in methanol, a platinum assisted cyclization was observed. The reaction products were ∆ 2 -1,3,4-oxadiazoline-5-thione derivatives and the binuclear tricationic complex [Pt 2 (µ-SMe)(terpy) 2 ] 3ϩ whose molecular structure has been determined by X-ray crystallography. This platinum assisted transformation is proposed as a new synthetic route to ∆ 2 -1,3,4-oxadiazoline-5-thiones under mild conditions. In the presence of an excess of a non-co-ordinating acid (HClO 4 , CH 3 SO 3 H or CF 3 SO 3 H) the cyclization is completely quenched and complexes with co-ordinated S-methyl 3-acyl-2-methyldithiocarbazates have been isolated. A general mechanism which accounts for the observed transformations is proposed on the basis of 1 H NMR and UV/Vis evidence.
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