Photoinduced Reductive C-O Couplings from Unsymmetrical Bis-Cyclometalated Pt(IV) Dicarboxylato Complexes.

Unsymmetrical bis-cyclometalated dicarboxylato complexes (-6-32)-[Pt(tpy)(OCR)] [tpy = cyclometalated 2-(-tolyl)pyridine, R = -Bu (), Me (), Ph (), CF ()], are obtained from the reaction of -[Pt(tpy)] with the appropriate PhI(OCR) reagent. Treatment of complexes of this type with different carboxylates (R'CO) results in the formation of mixed-carboxylato derivatives, namely (-6-43)-[Pt(tpy)(OCMe)(OCR')] [R' = -Bu (), CF (), Ph ()], (-6-34)-[Pt(tpy)(OCCF)(OCR')] [R' = -Bu (), Me (), Ph ()], and (-6-34)-[Pt(tpy)(OC--Bu)(OCMe)] (). Irradiation of - and - with UV light (365 nm) in MeCN gives 5-methyl-2-(2-pyridyl)phenyl pivalate (), 5-methyl-2-(2-pyridyl)phenyl acetate () or 5-methyl-2-(2-pyridyl)phenyl benzoate () as the major photoproduct from most complexes, resulting from a reductive C-O coupling between a tpy ligand and a carboxylato ligand.

Synthesis, Luminescence, and Electrochemistry of Tris-Chelate Platinum(IV) Complexes with Cyclometalated N-Heterocyclic Carbene Ligands and Aromatic Diimines.

Dicationic, -symmetrical, tris-chelate Pt(IV) complexes of general formula [Pt(trz)(N∧N)](OTf), bearing two cyclometalated 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) ligands and one aromatic diimine [N∧N = 2,2'-bipyridine (bpy, ), 4,4'-di--butyl-2,2'-bipyridine (dbbpy, ), 4,4'-dimethoxi-2,2'-bipyridine (dMeO-bpy, ), 1,10-phenanthroline (phen, ), 4,7-diphenyl-1,10-phenanthroline (bphen, ), dipyrido[3,2-:2',3'-]phenazine (dppz, ), or 2,3-diphenylpyrazino[2,3-][1,10]phenanthroline (dpprzphen, )] are obtained through chloride abstraction from [PtCl(trz)] () using AgOTf in the presence of the corresponding diimine. Complexes show long-lived phosphorescence from LC excited states involving the diimine ligand, with quantum yields that reach 0.18 in solution and 0.

Luminescent Platinum(II) Complexes with Terdentate N∧C∧C Ligands.

The synthesis, structure, and luminescence of Pt(II) complexes of the type [Pt(N∧C∧C)(L)] are reported, where N∧C∧C is a terdentate ligand resulting from the cycloplatination of 2-(3,5-diphenoxyphenyl)pyridine or 2-(4,4″-dimethyl-[1,1':3',1″-terphenyl]-5'-yl)pyridine, and L represents a monodentate ancillary ligand, which can be γ-picoline, 4-pyridinecarboxaldehyde, PPh, butyl or 2,6-dimethylphenyl isocyanide, CO, or the N-heterocyclic carbenes 1-butyl-3-methylimidazol-2-ylidene or 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene. Derivatives bearing CO, isocyanides, or carbenes showed the highest stabilities in solution, whereas the pyridine and PPh derivatives establish ligand-exchange equilibria in acetonitrile. Different supramolecular structures are observed in the solid state, which largely depend on the nature of the ancillary ligand.

Photoinduced Reductive C-C and C-Heteroatom Couplings from Bis-cyclometalated Pt(IV) Alkynyl Complexes.

Unsymmetrical dicarboxylato complexes [Pt(tpy)(OCR)] [tpy = cyclometalated 2-(-tolyl)pyridine, R = Me, CF] react with the terminal alkynes 4-methoxyphenylacetylene, phenylacetylene, 4-(trifluoromethyl)phenylacetylene or 3,5-difluorophenylacetylene in the presence of a base to produce complexes -[Pt(tpy)(OCR)(CCAr)], in which the metalated carbon atoms are in a meridional arrangement. Irradiation of the trifluoroacetato derivatives with a 365 nm LED source leads to isomerization to the facial complexes, which can be converted to chlorido derivatives upon reaction with NHCl. In contrast, irradiation of the acetato derivatives leads to four different processes, namely, reduction to -[Pt(tpy)], annulations involving one of the tpy ligands and the C and C atoms of the alkynyl to give benzoquinolizinium derivatives, isomerization to the facial geometry, or C-O couplings between the acetato ligand and one tpy.

Photochemically Induced Cyclometalations at Simple Platinum(II) Precursors.

Photochemical cycloplatinations of 2-arylpyridines and related C∧N ligands, as well as terdentate heteroaromatic N∧N∧C, N∧C∧N, and N∧C∧C compounds, are demonstrated using (BuN)[PtCl] or [PtCl(NCPh)] as precursors at room temperature. Mono- or bis-cyclometalated Pt(II) complexes with C∧N ligands are obtained depending on excitation wavelength and precursor. Monitoring experiments show that photoexcitation enables both the N-coordination and the subsequent C-H metalation.

Reductive Elimination Reactions in Gold(III) Complexes Leading to C(sp)-X (X = C, N, P, O, Halogen) Bond Formation: Inner-Sphere vs S2 Pathways.

The reactions leading to the formation of C-heteroatom bonds in the coordination sphere of Au(III) complexes are uncommon, and their mechanisms are not well known. This work reports on the synthesis and reductive elimination reactions of a series of Au(III) methyl complexes containing different Au-heteroatom bonds. Complexes [Au(CF)(Me)(X)(PR)] (R = Ph, X = OTf, OClO, ONO, OC(O)CF, F, Cl, Br; R = Cy, X = Me, OTf, Br) were obtained by the reaction of -[Au(CF)(Me)(PR)] (R = Ph, Cy) with HX.

Phosphorescent Tris-cyclometalated Pt(IV) Complexes with Mesoionic -Heterocyclic Carbene and 2-Arylpyridine Ligands.

The synthesis, structure, photophysical properties, and electrochemistry of the first series of Pt(IV) tris-chelates bearing cyclometalated aryl-NHC ligands are reported. The complexes have the general formula [Pt(trz)(C∧N)], combining two units of the cyclometalated, mesoionic aryl-NHC ligand 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) with a cyclometalated 2-arylpyridine [C∧N = 2-(2,4-difluorophenyl)pyridine (dfppy), 2-phenylpyridine (ppy), 2-(-tolyl)pyridine (tpy), 2-(2-thienyl)pyridine (thpy), 2-(9,9-dimethylfluoren-2-yl)pyridine (flpy)], and presenting a arrangement or metalated aryls. They exhibit a significant photostability under UV irradiation and long-lived phosphorescence in the blue to yellow color range, arising from LC excited states involving the C∧N ligands, with quantum yields of up to 0.

Phosphorescent biaryl platinum(IV) complexes obtained through double metalation of dibenzoiodolium ions.

The first series of neutral, tris-chelate, phosphorecent Pt(IV) complexes is reported, which combine two cyclometalated 2-arylpyridine ligands and a dimetalated biaryl. The introduction of biaryl ligands is achieved under mild conditions through the oxidative addition of dibenzoiodolium ions to Pt(II) precursors to give Pt(IV) intermediates with a singly metalated 2-(2-iodoaryl)aryl ligand, followed by the reductive metalation of the C-I bond. The modulation of emission characteristics derivatization of both types of ligands is demonstrated.

Luminescent halido(aryl) Pt(IV) complexes obtained oxidative addition of iodobenzene or diaryliodonium salts to bis-cyclometalated Pt(II) precursors.

The synthesis of bis-cyclometalated halido(aryl) Pt(IV) complexes [PtX(Ar)(C^N)], with C^N = cyclometalated 4-(-butyl)-2-phenylpyridine (bppy), 2-(-tolyl)pyridine (tpy), 2-(2-thienyl)pyridine (thpy), or 1-phenylisoquinoline (piq), X = I, Cl, or F, and Ar = Ph (for all C^N ligands) or -BuPh (for C^N = tpy), and the photophysical properties of the chlorido and fluorido series is reported. The oxidative addition of iodobenzene to -[Pt(C^N)] precursors is demonstrated to occur in MeCN under irradiation with visible light to give complexes [PtI(Ph)(C^N)], presumably involving radical species that also produce the activation of the solvent to give cyanomethyl complexes [PtI(CHCN)(C^N)]. The introduction of an aryl ligand can also be achieved by reacting -[Pt(C^N)] with (ArI)PF (Ar = Ph, -BuPh), which affords cationic intermediates of the type [Pt(Ar)(C^N)(NCMe)].

Visible light driven generation and alkyne insertion reactions of stable bis-cyclometalated Pt(iv) hydrides.

Hydride complexes resulting from the oxidative addition of C-H bonds are intermediates in hydrocarbon activation and functionalization reactions. The discovery of metal systems that enable their direct formation through photoexcitation with visible light could lead to advantageous synthetic methodologies. In this study, easily accessible dimers [Pt(μ-Cl)(C^N)] (C^N = cyclometalated 2-arylpyridine) are demonstrated as a very convenient source of Pt(C^N) subunits, which promote photooxidative C-H addition reactions with different 2-arylpyridines (N'^C'H) upon irradiation with blue light.

Strongly Luminescent Pt(IV) Complexes with a Mesoionic -Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties.

The synthesis, electrochemistry, and photophysical properties of a series of bis-cyclometalated Pt(IV) complexes that combine the mesoionic aryl-NHC ligand 4-butyl-3-methyl-1-phenyl-1-1,2,3-triazol-5-ylidene (trz) with either 1-phenylpyrazole or 2-arylpyridine (CN) are reported. The complexes (-6-54)-[PtCl(CN)(trz)] bearing cyclometalating 2-arylpyridines present phosphorescent emissions in the blue to yellow color range, which essentially arise from LC(CN) states, and reach quantum yields of ca. 0.

Stereoselective Formation of Facial Tris-Cyclometalated Pt Complexes: Dual Phosphorescence from Heteroleptic Derivatives.

A stereoselective synthetic route to homo- and heteroleptic facial tris-cyclometalated Pt complexes is reported, involving the oxidative addition of 2-(2-pyridyl)- or 2-(1-isoquinolinyl)benzenediazonium salts to cis-[Pt(C^N) ] precursors, with C^N=cyclometalated 2-(p-tolyl)pyridine (tpy), 2-phenylquinoline (pq), 2-(2-thienyl)pyridine or 1-phenylisoquinoline (piq), to produce labile diazenide intermediates that undergo photochemical or thermal elimination of N . The method allows the preparation of derivatives bearing cyclometalated ligands of low π-π* transition energies. The new complexes exhibit phosphorescence in fluid solution at room temperature arising from triplet ligand-centered ( LC) excited states, which, in the cases of the heteroleptic derivatives, involve the ligand with the lowest π-π* gap.

Selective synthesis, reactivity and luminescence of unsymmetrical bis-cyclometalated Pt(iv) complexes.

Pt(ii) complexes cis-N,N-[PtCl(C^N)(N'^C'H)], where C^N represents a monocyclometalated 2,6-diaryl- or 2-arylpyridine ligand and N'^C'H is an N-coordinated 2-arylpyridine, are selectively obtained from bridge-cleavage reactions of dimers [Pt(μ-Cl)(C^N)] with excess N'^C'H at room temperature; isolation and characterization of derivatives of this kind is reported for the first time. Oxidation with PhICl affords Pt(iv) complexes [PtCl(C^N)(C'^N')], bearing two cyclometalated ligands in an unsymmetrical arrangement. The abstraction of the two chlorides using AgOTf at 120 °C in the presence of an additional 2-arylpyridine ligand leads to mer isomers of tris-cyclometalated Pt(iv) complexes if C^N derives from a 2-arylpyridine, whereas it results in a reductive C-C coupling if C^N is a monocyclometalated 2,6-diarylpyridine.

Luminescent Platinum(IV) Complexes Bearing Cyclometalated 1,2,3-Triazolylidene and Bi- or Terdentate 2,6-Diarylpyridine Ligands.

The synthesis, structure, and photophysical properties of luminescent Pt complexes that combine cyclometalated 1,2,3-triazolylidene and bi- or terdentate 2,6-diarylpyridine ligands are reported. The targeted complexes represent the first examples of Pt species with a cyclometalated mesoionic aryl-NHC ligand. They exhibit moderate or weak emissions in fluid solution at 298 K arising from LC states, which become very intense in poly(methyl methacrylate) (PMMA) matrices at 298 K.

Influence of Ancillary Ligands and Isomerism on the Luminescence of Bis-cyclometalated Platinum(IV) Complexes.

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.

Spotlight on the ligand: luminescent cyclometalated Pt(iv) complexes containing a fluorenyl moiety.

The synthesis, electrochemistry and photophysical properties of a family of Pt(iv) complexes with cyclometalated 2-(9,9-dimethylfluoren-2-yl)pyridine (flpy) are reported. Homoleptic and heteroleptic tris-cyclometalated complexes with a meridional configuration, mer-[Pt(C^N)2(flpy)]OTf, with C^N = flpy or cyclometalated 2-phenylpyridine (ppy), were prepared by reacting the bis-cyclometalated precursors [Pt(C^N)2Cl2] with flpyH in the presence of two equivalents of AgOTf. The corresponding facial isomers were obtained by photoisomerization.

Aromatic C-H Activation in the Triplet Excited State of Cyclometalated Platinum(II) Complexes Using Visible Light.

The visible-light driven cyclometalation of arene substrates containing an N-donor heteroaromatic moiety as directing group by monocyclometalated Pt(II) complexes is reported. Precursors of the type [PtMe(C^N)(N^CH)], where N^CH is 2-phenylpyridine (ppyH) or related compunds with diverse electronic properties and C^N is the corresponding cyclometalated ligand, afford homoleptic cis-[Pt(C^N)2] complexes upon irradiation with blue LEDs at room temperature with evolution of methane. Heteroleptic derivatives cis-[Pt(ppy)(C'^N')] are obtained analogously from [PtMe(ppy)(N'^C'H)], where N'^C'H represents an extended set of heteroaromatic compounds.

Developing strongly luminescent platinum(IV) complexes: facile synthesis of bis-cyclometalated neutral emitters.

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.

Exploring excited-state tunability in luminescent tris-cyclometalated platinum(IV) complexes: synthesis of heteroleptic derivatives and computational calculations.

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.

Novel types of tetra-, hexa-, octa-, and dodecanuclear silver clusters containing (2,7-Di-tert-butylfluoren-9-ylidene)methanedithiolate.

The reaction of AgClO(4) with piperidinium 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate (pipH)[S(2)C(t-Bu-Hfy)] (1) (t-Bu-Hfy = 2,7-di-tert-butylfluoren-9-yl) afforded [Ag(n){S(2)C(t-Bu-Hfy)}(n)] (2), which reacted with phosphines to give [Ag{S(2)C(t-Bu-Hfy)}L(2)] [L = PPh(3) (3a); L(2) = bis(diphenylphosphino)ethane (dppe, 3b), 1,1'-bis(diphenylphosphino)ferrocene (dppf, 3c). By reacting complex 2 with AgClO(4) and piperidine in a 1:1:1 molar ratio, the dodecanuclear cluster [Ag(12){S(2)C(t-Bu-fy)}(6)] (4) (t-Bu-fy = 2,7-di-tert-butylfluoren-9-ylidene) was obtained. Compound 4 can also be directly prepared from the reaction of 1 with AgClO(4) and piperidine in a 1:2:1 molar ratio.

Dinuclear copper(I) and copper(I)/silver(I) complexes with condensed dithiolato ligands.

The Cu(III) complex Pr 4N[Cu{S 2C=( t-Bu-fy)} 2] ( 1) ( t-Bu-fy = 2,7-di- tert-butylfluoren-9-ylidene) reacts with [Cu(PR 3) 4]ClO 4 in 1:1 molar ratio in MeCN to give the dinuclear complexes [Cu 2{[SC=( t-Bu-fy)] 2S}(PR 3) n ] [ n = 2, R = Ph ( 2a); n = 3, R = To ( 3b); To = p-tolyl]. The analogue of 2a with R = To ( 2b) can be obtained from the reaction of 3b with 1/8 equiv of S 8. Compound 2b establishes a thioketene-exchange equilibrium in solution leading to the formation of [Cu 4{S 2C=( t-Bu-fy)} 2(PTo 3) 4] ( 4b) and [Cu 2{[SC=( t-Bu-fy)] 3S}(PTo 3) 2] ( 5b).

Synthesis, structure, and luminescence of di- and trinuclear palladium/gold and platinum/gold complexes with (2,7-di-tert-butylfluoren-9-ylidene)methanedithiolate.

Acetone solutions of [Au(OClO3)(PCy3)] react with complexes [M{S2C=(t-Bu-fy)}2]2- [t-Bu-fy=2,7-di-tert-butylfluoren-9-ylidene; M=Pd (2a), Pt (2b)] or [M{S2C=(t-Bu-fy)}(dbbpy)] [dbbpy=4,4'-di-tert-butyl-2,2'-bipyridyl; M=Pd (3a), Pt (3b)] to give the heteronuclear complexes [M{S2C=(t-Bu-fy)}2{Au(PCy3)}2] [2:1 molar ratio; M=Pd (4a), Pt (4b)], [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}]ClO4 [1:1 molar ratio; M=Pd (5a), Pt (5b)], or [M{S2C=(t-Bu-fy)}(dbbpy){Au(PCy3)}2](ClO4)2 [2:1 molar ratio; M=Pd (6a), Pt (6b)]. The crystal structures of 3a, 4a, 4b, 5b, and 6a have been solved by single-crystal X-ray studies and, in the cases of the heteronuclear derivatives, reveal the formation of short Pd..

(Fluoren-9-ylidene)methanedithiolato complexes of platinum: synthesis, reactivity, and luminescence.

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{S(2)C=C(C12H6R(2)-2,7)}2] [R = H, (Pr(4)N)(2)2a; R = t-Bu, (Pr4N)(2)2b, (Et4N)(2)2b; R = OMe, (Pr4N)(2)2c] were prepared from PtCl(2), piperidine, the corresponding QCl salt, and 1a-c in molar ratio 1:2:2:2. In the absence of QCl, the complexes (pipH)(2)2b and [Pt(pip)(4)]2b were isolated depending on the PtCl(2):pip molar ratio.

(Fluoren-9-ylidene)methanedithiolato complexes of gold: synthesis, luminescence, and charge-transfer adducts.

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.