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

Abstract

The divalent complex [{Pt(bzq)(μ-L)}2] (1) [Hbzq = benzo[h]quinolone, HL = CF3C4H2N2SH: 4-(trifluoromethyl)pyrimidine-2-thiol] was obtained from equimolar amounts of [Pt(bzq)(NCMe)2]ClO4 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[arrow right]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)X}2] (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.