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(Fluoren-9-ylidene)methanedithiolato Complexes of Platinum:  Synthesis, Reactivity, and Luminescence1

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posted on 03.10.2005, 00:00 by José Vicente, Pablo González-Herrero, María Pérez-Cadenas, Peter G. Jones, Delia Bautista
Platinum(II) complexes with (fluoren-9-ylidene)methanedithiolato and its 2,7-di-tert-butyl- and 2,7-dimethoxy-substituted analogues were obtained by reacting different chloroplatinum(II) precursors with the piperidinium dithioates (pipH)[(2,7-R2C12H6)CHCS2] [R = H (1a), t-Bu (1b), or OMe (1c)] in the presence of piperidine. The anionic complexes Q2[Pt{S2CC(C12H6R2-2,7)}2] [R = H, (Pr4N)22a; R = t-Bu, (Pr4N)22b, (Et4N)22b; R = OMe, (Pr4N)22c] were prepared from PtCl2, piperidine, the corresponding QCl salt, and 1ac in molar ratio 1:2:2:2. In the absence of QCl, the complexes (pipH)22b and [Pt(pip)4]2b were isolated depending on the PtCl2:pip molar ratio. The neutral complexes [Pt{S2CC(C12H6R2-2,7)L2] [L = PPh3, R = H (3a), t-Bu (3b), OMe (3c); L = PEt3, R = H (4a), t-Bu (4b), OMe (4c); L2 = dbbpy, R = H (5a), t-Bu (5b), OMe (5c) (dbbpy = 4,4‘-di-tert-butyl-2,2‘-bipyridyl)] were similarly prepared from the corresponding precursors [PtCl2L2] and 1ac in the presence of piperidine. Oxidation of Q22b with [FeCp2]PF6 afforded the mixed Pt(II)−Pt(IV) complex Q2[Pt2{S2CC[C12H6(t-Bu)2-2,7]}4] (Q26, Q = Et4N+, Pr4N+). The protonation of (Pr4N)22b with 2 equiv of triflic acid gave the neutral dithioato complex [Pt2{S2CCH[C12H6(t-Bu)2-2,7]}4] (7). The same reaction in 1:1 molar ratio gave the mixed dithiolato/dithioato complex Pr4N[Pt{S2CC[C12H6(t-Bu)2-2,7]}{S2CCH[C12H6(t-Bu)2-2,7]}] (Pr4N8) while the corresponding DMANH+ salt was obtained by treating 7 with 2 equiv of 1,8-bis(dimethylamino)naphthalene (DMAN). The crystal structures of 3b and 5c·CH2Cl2 have been solved by X-ray crystallography. All the platinum complexes are photoluminescent at 77 K in CH2Cl2 or KBr matrix, except for Q26. Compounds 5ac and Q8 show room-temperature luminescence in fluid solution. The electronic absorption and emission spectra of the dithiolato complexes reveal charge-transfer absorption and emission energies which are significantly lower than those of analogous platinum complexes with previously described 1,1-ethylenedithiolato ligands and in most cases compare well to those of 1,2-dithiolene complexes.