Tris-cyclometalated Pt(IV) complexes are reported for the first time. The facial isomers exhibit long-lived 3LC emissions with quantum yields up to 0.49, the highest ever found for Pt(IV) complexes, combined with a strong oxidizing character in the excited state.

The synthesis, structure, electrochemistry, and photophysical properties of a series of heteroleptic tris- cyclometalated Pt(IV) complexes are reported. The complexes mer-[Pt(C^N)2 (C'^N')]OTf, with C^N=C-deprotonated 2-(2,4-difluorophenyl)pyridine (dfppy) or 2-phenylpyridine (ppy), and C'^N'=C-deprotonated 2-(2-thienyl)pyridine (thpy) or 1-phenylisoquinoline (piq), were obtained by reacting bis- cyclometalated precursors [Pt(C^N)2 Cl2] with AgOTf (2 equiv) and an excess of the N'^C'H pro-ligand. The complex mer-[Pt(dfppy)2 (ppy)]OTf was obtained analogously and photoisomerized to its fac counterpart. The new complexes display long-lived luminescence at room temperature in the blue to orange color range. The emitting states involve electronic transitions almost exclusively localized on the ligand with the lowest π-π* energy gap and have very little metal character. DFT and time-dependent DFT (TD-DFT) calculations on mer-[Pt(ppy)2 (C'^N')](+) (C'^N'=thpy, piq) and mer/fac-[Pt(ppy)3](+) support this assignment and provide a basis for the understanding of the luminescence of tris-cyclometalated Pt(IV) complexes. Excited states of LMCT character may become thermally accessible from the emitting state in the mer isomers containing dfppy or ppy as chromophoric ligands, leading to strong nonradiative deactivation. This effect does not operate in the fac isomers or the mer complexes containing thpy or piq, for which nonradiative deactivation originates mainly from vibrational coupling to the ground state.

The synthesis, characterization, and photophysical properties of a wide variety of bis-cyclometalated Pt(IV) complexes featuring a C2-symmetrical or unsymmetrical {Pt(ppy)2} unit (sym or unsym complexes, respectively; ppy = C-deprotonated 2-phenylpyridine) and different ancillary ligands are reported. Complexes sym-[Pt(ppy)2X2] (X = OTf(-), OAc(-)) were obtained by chloride abstraction from sym-[Pt(ppy)2Cl2] using the corresponding AgX salts, and the triflate derivative was employed to obtain homologous complexes with X = F(-), Br(-), I(-), trifluoroacetate (TFA(-)). Complexes unsym-[Pt(ppy)2(Me)X] (X = OTf(-), F(-)) were prepared by reacting unsym-[Pt(ppy)2(Me)Cl] with AgOTf or AgF, respectively, and the triflate derivative was employed as precursor for the synthesis of the homologues with X = Br(-), I(-), or TFA(-) through its reaction with the appropriate anionic ligands. The previously reported complexes unsym-[Pt(ppy)2X2] (X = Cl(-), Br(-), OAc(-), TFA(-)) are included in the photophysical study to assess the influence of the arrangement of the cyclometalated ligands. Density functional theory (DFT) and time-dependent DFT calculations on selected derivatives were performed for a better interpretation of the observed excited-state properties. Complexes sym-[Pt(ppy)2X2] (except X = I(-)) exhibit phosphorescent emissions in fluid solutions at 298 K arising from essentially (3)LC(ppy) excited states, which are very similar in shape and energy. However, their efficiencies are heavily dependent on the nature of the ancillary ligands, which affect the energy of deactivating ligand-to-ligand charge transfer (LLCT) or ligand-to-metal charge transfer (LMCT) states. The fluoride derivative sym-[Pt(ppy)2F2] shows the highest quantum yield of this series (Φ = 0.398), mainly because the relatively high metal-to-ligand charge transfer admixture in its emitting state leads to a high radiative rate constant. Complexes unsym-[Pt(ppy)2X2] emit from (3)LC(ppy) states in frozen matrices at 77 K, but their emissions are totally quenched in fluid solution at 298 K because of the presence of low-lying, dissociative LMCT excited states, which also cause photoisomerization reactions. Complexes unsym-[Pt(ppy)2(Me)X] (X = F(-), Cl(-), Br(-), TFA(-)) show strong emissions in fluid solutions at 298 K (Φ = 0.52-0.63) because deactivating LMCT states lie at high energies. However, derivative unsym-[Pt(ppy)2(Me)I] is only weakly emissive at 298 K because of the presence of low-lying LLCT [p(I) → π*(ppy)] states.

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.

A straightforward, one-pot procedure has been developed for the synthesis of bis-cyclometalated chloro(methyl)platinum(IV) complexes with a wide variety of heteroaromatic ligands of the 2-arylpyridine type. The new compounds exhibit phosphorescent emissions in the blue to orange colour range and represent the most efficient Pt(IV) emitters reported to date, with quantum yields up to 0.81 in fluid solutions at room temperature.

The dihydridoruthenium(IV) compound [RuH2Cl2(P i Pr3)2] (2), which is obtained on treatment of [RuCl2(C8H12)] n with P i Pr3 in 2-butanol in the presence of H2, reacts with PhC⋮CH in CH2Cl2 at 25 °C to give a mixture of [RuCl2(CCHPh)(P i Pr3)2] (4) and [RuCl2(CHCH2Ph)(P i Pr3)2] (5). Both complexes 4 and 5 as well as the methylcarbene derivative [RuCl2(CHCH3)(P i Pr3)2] (6) have been isolated; moreover, compounds 2 and 5 have been characterized by X-ray crystal structure analyses.

Aryl palladium complexes [Pd{C 6 H 4 CH 2 C(O)NRR 0 -2}I(N ∧ N)] (N ∧ N = N,N,N 0 ,N 0 -tetramethylethylenediamine = tmeda, NRR 0 = NH 2 (1a), NHMe (1b), NMe 2 (1c); N ∧ N = 4,4 0 -di-tert-butyl-2,2 0 -bipyridyl (dbbpy), NRR 0 = NHMe (1b 0 )) are prepared by oxidative addition of the corresponding 2-(2-iodophenyl)acetamide to "Pd(dba) 2 " ([Pd 2 (dba) 3 ] 3 dba; dba = dibenzylideneacetone) in the presence of the N ∧ N chelating ligand. Cationic cyclometalated derivatives [are obtained by reacting the appropriate complex 1 with AgOTf. The reaction of 2b 0 with PPh 3 affords [Pd{C 6 H 4 CH 2 C(O)NHMe-2}(dbbpy)(PPh 3 )]OTf (3b 0 ). Neutral amidate complexes of the type [Pd{κ 2 C,N-C 6 H 4 CH 2 C(O)NR-2}(N ∧ N)] (N ∧ N = tmeda, R = H (4a), Me (4b); N ∧ N = dbbpy, R = Me (4b 0 )) are obtained upon deprotonation of the corresponding complex 1 with KO t Bu. The complex [Pd{C 6 H 4 CH 2 C(O)NHMe-2}{CH(CN) 2 }(dbbpy)] (5b 0 ) has been prepared by reacting 4b 0 with malononitrile. Acyl derivatives [Pd{C(O)C 6 H 4 CH 2 C(O)NRR 0 -2}I(N ∧ N)] (N ∧ N = tmeda, NRR 0 = NH 2 (6a), NHMe (6b), NMe 2 (6c); N ∧ N = dbbpy, NRR 0 = NHMe (6b 0 )) have been prepared by reacting the corresponding complex 1 with CO at low temperature; when N ∧ N = tmeda, prolonged reaction times and high temperatures lead to Pd(0) and isoquinoline-1,3(2H,4H)-dione (7a), a 1:2 mixture of 2-methylisoquinoline-1,3(2H,4H)-dione (7b) and 3-(dimethylamino)-1H-2-benzopyran-1-one (8b), or 3-(methylamino)-1H-2-benzopyran-1-one (8c), respectively. Similar results are obtained from the reactions of 2a-c with CO under much milder conditions, while 2b 0 reacts with CO in acetone to give the isochroman-1-one derivative N,3,3-trimethyl-1-oxo-3,4-dihydro-1H-2-benzopyrane-4-carboxamide (9). While the reaction of 1b 0 with 1 equiv of XyNC (Xy = 2,6-dimethylphenyl) gives the iminoacyl complex [Pd{C(dNXy)-C 6 H 4 CH 2 C(O)NHMe-2}I(dbbpy)] (10b 0

The cyclopalladated complexes [Pd{κ 2 C,O-C 6 H 4 CH 2 C(O)NRR′-2}(tmeda)]TfO [R = R′ = H (1a), R = Me, R′ = H (1b), R = R′ = Me (1c)] react with alkynes XC CX′ in 1:3 molar ratio to give the eight-membered palladacycles [Pd{κ 2 C,O-C(X)C(X′)C 6 H 4 CH 2 C(O)NRR′-2}-(tmeda)]TfO [R = R′ = H and X = X′ = Ph (2aa), CO 2 Me (2ab), Et (2ac) or X = Ph, X′ = Me (2ad); R = Me, R′ = H and X = X′ = Ph (2ba), CO 2 Me (2bb), Et (2bc) or X = Ph, X′ = Me (2bd); R = R′ = Me and X = X′ = Ph (2ca)]. The treatment of complexes 2aa, 2ac, 2ad, 2ba, 2bc, and 2bd with CO at 50 °C affords the corresponding benzo[d]azocine-2,4(1H,3H)-diones (3), which result from the insertion of a molecule of CO into the Pd−C bond and subsequent C−N reductive coupling and formation of (tmedaH)TfO. The reaction of 2ab with CO in MeOH gives (MeO 2 C) 2 C C(CO 2 Me)C 6 H 4 CH 2 C(O)NH 2 -2 (4ab). Complexes 2aa and 2ab react with 1 equiv of R″NC 1:1 to give [Pd{C(X) C(X′)C 6 H 4 CH 2 C(O)NH 2 -2}(CNR″)(tmeda)]TfO [R″ = t-Bu, X = X′ = Ph (5a), CO 2 Me (5b); R = Xy, X = X′ = Ph (5a′), CO 2 Me (5b′)]. While 2aa reacts with 1 equiv of R″NC in refluxing CHCl 3 to give a low yield of the compound XyHNC(O)C(Ph)C(Ph)C 6 H 4 CH 2 C(O)NH 2 -2 (6a) when R″ = Xy, the complex 2aa, 2ba, or 2ca affords the acrylonitrile derivative NCC(Ph)C(Ph)C 6 H 4 CH 2 C(O)NRR′-2 [R = R′ = H (7a), R = Me, R′ = H (7b), R = R′ = Me (7c)] when R″ = t-Bu; alternatively, the latter derivatives can be obtained by refluxing in situ generated solutions of the corresponding cyano complexes [Pd{C(Ph)C(Ph)C 6 H 4 CH 2 C(O)NRR′-2}(CN)(tmeda)] in CHCl 3 . The intermediate cyano complex with R = R′ = H (8) has been isolated and characterized. The reactions of 2aa, 2ba, 2ca, and 2ac with 4 equiv of XyNC give [Pd 3 (CNXy) 6 ] and mixtures from which the compounds XyNHC(O)C(Ph)C(Ph)C 6 H 4 CH 2 CN-2 (9, from 2aa), XyNHC(O)C(Ph) C(Ph)C 6 H 4 CH 2 C(O)NRR′-2 [R = Me, R′ = H (6b), R = R′ = Me (6c), from 2ba or 2ca, respectively], or [Pd{C( NXy)C(Et)C(Et)C 6 H 4 CH 2 CN-2}Cl(CNXy) 2 ] (10, from 2ac) can be isolated. The crystal structures of 2aa•2Et 2 O, 3aa, 3ac, 8, 9, and 10 have been determined.