(Fluoren-9-ylidene)methanedithiolato Complexes of Gold:  Synthesis, Luminescence, and Charge-Transfer Adducts¹

Abstract

Piperidinium 9H-fluorene-9-carbodithioate and its 2,7-di-tert-butyl-substituted analogue [(pipH)(S(2)CCH(C(12)H(6)R(2)-2,7)), R = H (1a), t-Bu (1b)] and 2,7-bis(octyloxy)-9H-fluorene-9-carbodithioic acid [HS(2)CCH(C(12)H(6)(OC(8)H(17))(2)-2,7), 2] and its tautomer [2,7-bis(octyloxy)fluoren-9-ylidene]methanedithiol [(HS)(2)C=C(C(12)H(6)(OC(8)H(17))(2)-2,7), 3] were employed for the preparation of gold complexes with the (fluoren-9-ylidene)methanedithiolato ligand and its substituted analogues. The gold(I) compounds Q(2)[Au(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)], where Q(+) = PPN(+) or Pr(4)N(+) for R = H (Q(2)4a) or Q(+) = Pr(4)N(+) for R = OC(8)H(17) [(Pr(4)N)(2)4c], were synthesized by reacting Q[AuCl(2)] with 1a or 2 (1:1) and excess piperidine or diethylamine. Complexes of the type [(Au(PR'3))(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with R = H and R' = Me (5a), Et (5b), Ph (5c), and Cy (5d) or R = t-Bu and R' = Me (5e), Et (5f), Ph (5g), and Cy (5h) were obtained by reacting [AuCl(PR'(3))] with 1a,b (1:2) and piperidine. The reactions of 1a,b or 2 with Q[AuCl(4)] (2:1) and piperidine or diethylamine gave Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with Q(+) = PPN(+) for R = H [(PPN)6a], Q(+) = PPN(+) or Bu(4)N(+) for R = t-Bu (Q6b), and Q(+) = Bu(4)N(+) for R = OC(8)H(17) [(Bu(4)N)6c]. Complexes Q6a-c reacted with excess triflic acid to give [Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(kappa(2)-S,S-S(2)CCH(C(12)H(6)R(2)-2,7))] [R = H (7a), t-Bu (7b), OC(8)H(17) (7c)]. By reaction of (Bu(4)N)6b with PhICl(2) (1:1) the complex Bu(4)N[AuCl(2)(kappa(2)-S,S-S(2)C=C(C(12)H(6)(t-Bu)(2)-2,7))] [(Bu(4)N)8b] was obtained. The dithioato complexes [Au(SC(S)CH(C(12)H(8)))(PCy(3))] (9) and [Au(n)(S(2)CCH(C(12)H(8)))(n)] (10) were obtained from the reactions of 1a with [AuCl(PCy(3))] or [AuCl(SMe(2))], respectively (1:1), in the absence of a base. Charge-transfer adducts of general composition Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)].1.5TCNQ.xCH(2)Cl(2) [Q(+) = PPN(+), R = H, x = 0 (11a); Q(+) = PPN(+), R = t-Bu, x = 2 (11b); Q(+) = Bu(4)N(+), R = OC(8)H(17), x = 0 (11c)] were obtained from Q6a-c and TCNQ (1:2). The crystal structures of 5c.THF, 5e.(2)/(3)CH(2)Cl(2), 5g.CH(2)Cl(2), (PPN)6a.2Me(2)CO, and 11b were solved by X-ray diffraction studies. All the gold(I) complexes here described are photoluminescent at 77 K, and their emissions can be generally ascribed to LMMCT (Q(2)4a,c, 5a-h, 10) or LMCT (9) excited states.

Copper Complexes with (2,7‐Di‐tert‐butylfluoren‐9‐ylidene)methanedithiolate: Oxidatively Promoted Dithioate Condensation

“…[46] The bond length of the uncoordinated C(9)=C(10) double bond [1.360(4) (4a) or 1.369(5) Å (4c)] is similar to the corresponding distances found for 1,1-ethylenedithiolato ligands, [28] which are usually close to the higher limit of the range found for C(sp 2 )=C(sp 2 ) double bonds (1.294-1.392 Å), [47] whereas the C(29)-C(30) distance of 1.401(4) (4a) or 1.396(5) Å (4c) is slightly longer, as expected for a coordinated C=C bond. The Cu(1)-Cu(2) distance of 2.6999(5) (4a) or 2.7568(6) Å (4c) is slightly shorter than the sum of the van der Waals radii for Cu (2.80 Å [48] ) and typical of the cuprophilic interactions found in numerous di-or polynuclear copper() complexes with bridging thiolato ligands.…”

“…3 or PCy 3 ligands in 4a,b or the PPh 2 groups of the dppf ligand in 4c. Thus, the 1 H NMR spectra show only two singlets for the tBu groups and two sets of resonances for the aromatic protons; the two signals corresponding to the 1-H and 8-H atoms are considerably downfield-shifted, as is the case for coordinated (fluoren-9-ylidene)methanedithiolato ligands, [28] and also the most affected by the lack of symmetry of the tBu-fy groups, appearing at very different chemical shifts (ranges δ = 9.61-9.71 and 8.55-8.69 ppm, respectively). The 13 C{ 1 H} NMR spectra show two sets of resonances for the carbon atoms of the ligand except for the C-9 and CS 2 atoms, each of which gives rise to only one resonance; the CS 2 resonance appears as a slightly broad signal for 4a,b, but in the case of 4c resolves as a triplet because of coupling with two equivalent phosphorus atoms.…”

“…In some cases, dithioato complexes have been obtained when the reactions are carried out in the absence of a base. [28] The synthesis of Cu I complexes with (tBu-Hfy)-CS 2 -was undertaken in order to use them as precursors for the preparation of complexes with the dithiolato ligand (tBu-fy)CS 2 2-. The reaction of the piperidinium dithioate 1 with [Cu(NCMe) 4 ]PF 6 in a 1:1 molar ratio in MeCN gave the dark brown complex [Cu n {S 2 C(tBu-Hfy)} n ] (2; Scheme 2), which precipitated in almost quantitative yield.…”

“…We have previously observed that the (fluoren-9-ylidene)methanedithiolato ligand and its 2,7-disubstituted derivatives facilitate the oxidation of Au I to Au III [28] and Pt II to Pt IV , [29] which can be attributed to their stronger electron-donating character as compared with other, more commonly studied 1,1-ethylenedithiolato ligands.…”

“…These ligands have revealed remarkable differences with respect to the previously used 1,1-ethylenedithiolates; these differences are largely attributable to the absence of strongly electron-withdrawing substituents and affect the photophysical properties and redox behavior of their metal complexes. [28,29] Given the multiple coordination possibilities and stoichiometries observed for copper/dithiolate systems, we thought it of interest to carry out an initial exploration of the chemistry of copper complexes with (2,7-di-tert-butylfluoren-9-ylidene)methanedithiolate [(tBu-fy)=CS 2 2-(I) Scheme 1], and to study the effects of the strongly electrondonating character of this ligand on their structures and reactivity. In this paper, we describe the preparation of a series of Cu I complexes with 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate [(tBu-Hfy)CS 2 -(II), the protonated precursor of I] obtained from the piperidinium salt (pipH) [ …”