Half-Lantern Pt(II) and Pt(III) Complexes. New Cyclometalated Platinum Derivatives

The divalent complex Pt (bzq) (μ-L) 2 (1) Hbzq = benzo[hquinolone, HL = CF3C4H2N2SH: 4- (trifluoromethyl) pyrimidine-2-thiol] was obtained from equimolar amounts of Pt (bzq) (NCMe) 2ClO4 and 4- (trifluoromethyl) pyrimidine-2-thiol with an excess of NEt3. The presence of a low intensity absorption band at 486 nm (CH2Cl2), assignable to a metal-metal-to-ligand charge transfer transition (1MMLCT) dσ* (Pt) 2→π* (bzq), is indicative of the existence of two platinum centers located in close proximity because the rigidity of the half-lantern structure allows the preservation of these interactions in solution. Compound 1 undergoes two-electron oxidation upon treatment with halogens X2 (X2: Cl2, Br2 or I2) to give the corresponding dihalodiplatinum (III) complexes Pt (bzq) (μ-L) X2 (L = CF3C4H2N2S-κN, S; X: Cl 2, Br 3, I 4). Complexes 2–4 were also obtained by reaction of 1 with HX (molar ratio 1: 2, 10% excess of HX) in THF with yields of about 80% and compound 2 was also obtained by reaction of Pt (bzq) (μ-Cl) 2 with HL (4- (trifluoromethyl) pyrimidine-2-thiol) in molar ratio 1: 2 in THF, although in small yield. The X-ray structures of 2 and 3 confirmed the half-lantern structure and the anti configuration of the molecules. Both of them show Pt–Pt distances (2. 61188 (15) Å 2, 2. 61767 (16) Å 3) in the low range of those observed in Pt2 (III, III) X2 half-lantern complexes.