Tetrylenes are Able to Discern between Isomeric Structures of Unsaturated Osmium(IV) Polyhydrides.

Hexahydride OsH(PPr) (1) releases H to form the isomeric tetrahydrides 2 a and 2 b of general formula OsH(PPr). Tetrylenes E{N(SiMe)} (E=Ge, Sn) are able to selectively trap these isomers distinguishing between them. Tetrylene Ge{N(SiMe)} catches 2 b to generate OsH{Ge[N(SiMe)]}(PPr) (3), which has a piano stool geometry, while Sn{N(SiMe)} captures 2 a to give OsH{Sn[N(SiMe)]}(PPr) (4) with the donor atoms defining a pentagonal bipyramid around the osmium center.

A Lead-μ-Tetrylide Complex with Osmium(IV) Terminal Components.

A bare lead atom is a σ-donor ligand capable of linearly bonding and stabilizing two units of a classical polyhydride complex, with a high-valent metal center. As a proof of concept, we have prepared and characterized the μ-tetrylide complex (PPr)HOs═Pb═OsH(PPr) in the reaction of OsH(PPr) with Pb{N(SiMe)}. Although the Pb-Os bonds exhibit electrostatic interaction, the main orbital interactions result from two dative σ bonds from the lead atom to the osmium centers.

-Pincers in Platinum Bimetallic Complexes: Influence of the Pincer and Bridging Ligands on the Metal-Metal Bond and the Photophysical Properties.

Precursors PtCl{κ--[py-CHMe-py]} (), PtCl{κ--[py-O-CH-O-py]} (), Pt(OH){κ--[py-CHMe-py]} (), and Pt(OH){κ--[py-O-CH-O-py]} () were used to prepare d-platinum bimetallic complexes. Precursors and react with AgBF and 7-azaindole (H) to give [Pt{κ--[py-CHMe-py]}{κ--[H]}]BF () and [Pt{κ--[py-O-CH-O-py]}{κ--[H]}]BF () and and with indolo[2,3-]indole (H) to generate Pt{κ--[H]}{κ--[py-CHMe-py]} () and Pt{κ--[H]}{κ--[py-O-CH-O-py]} (). Subsequent addition of and to - affords bimetallic derivatives [{Pt[κ--(py-CHMe-py)]}{μ--[]}]BF (), [{Pt[κ--(py-O-CH-O-py)]}{μ--[]}]BF (), and {Pt[κ--(py-CHMe-py)]}{μ--[]} ().

C-H, N-H, and O-H Bond Activations to Prepare Phosphorescent Hydride-Iridium(III)-Phosphine Emitters with Photocatalytic Achievement in C-C Coupling Reactions.

Complex IrH(PPr) () activates two different σ-bonds of 3-phenoxy-1-phenylisoquinoline, 2-(1-benzimidazol-2-yl)-6-phenylpyridine, 2-(1-indol-2-yl)-6-phenylpyridine, 2-(2-hydroxyphenyl)-6-phenylpyridine, -(2-hydroxyphenyl)-'-phenylimidazolylidene, and 1,3-di(2-pyridyl)-4,6-dimethylbenzene to give IrH{κ--[CH-isoqui-O-CH]}(PPr) (), IrH{κ--[NBzim-py-CH]}(PPr) (), IrH{κ--[Ind-py-CH]}(PPr) (), IrH{κ--[CH-py-CHO]}(PPr) (), IrH{κ--[CH-Im-CHO]}(PPr) (), and IrH{κ--[py-CHMe-CHN]}(PPr) (), respectively. The activations are sequential, with the second generally being the slowest. Accordingly, dihydride intermediates IrH{κ--[CH-isoqui-O-CH]}(PPr) (), IrH{κ--[NBzim-py-CH]}(PPr) (), IrH{κ--[Ind-py-CH]}(PPr) (), and IrH{κ--[py-CHMe-py]}(PPr) () were characterized spectroscopically.

Unequivocal Characterization of an Osmium Complex with a Terminal Sulfide Ligand and Its Transformation into Hydrosulfide and Methylsulfide.

Deprotonation of the thioamidate group of [OsH{κ-,-[NHC(CH)S]}(≡CPh)(IPr)(PPr)]OTf [; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CFSO] results in the release of acetonitrile and formation of the terminal sulfide complex OsH(S)(≡CPh)(IPr)(PPr) (), which has been transformed into the hydrosulfide [OsH(SH)(≡CPh)(IPr)(PPr)]OTf () and the methylsulfide [OsH(SMe)(≡CPh)(IPr)(PPr)]OTf () through protonation and methylation reactions, respectively. The structure, spectroscopic characteristics, and reactivity of these compounds are compared. Reactions of and with 2-hydroxypyridine and 2-mercaptopyridine afford [OsH{κ-,-[X-py]}(≡CPh)(IPr)(PPr)]OTf [X = O (), S()].

Two Synthetic Tools to Deepen the Understanding of the Influence of Stereochemistry on the Properties of Iridium(III) Heteroleptic Emitters.

Two complementary procedures are presented to prepare -pyridyl-iridium(III) emitters of the class [++] with two orthometalated ligands of the 2-phenylpyridine type () and a third ligand (). They allowed to obtain four emitters of this class and to compare their properties with those of the -pyridyl isomers. The finding starts from IrH(PPr), which reacts with 2-(-tolyl)pyridine to give -[Ir{κ--[CMeH-py]}] with an almost quantitative yield.

Preparation, Aromaticity, and Bromination of Spiro Iridafurans.

Iridium centers of [Ir(μ-Cl)(CH)] () activate the C(sp)-H bond of benzylideneacetone to give [Ir(μ-Cl){κ--[C(Ph)CHC(Me)O]}] (), which is the starting point for the preparation of the spiro iridafurans IrCl{κ--[C(Ph)CHC(Me)O]}(PPr) (), [Ir{κ--[C(Ph)CHC(Me)O]}(MeCN)]BF (), [Ir(μ-OH){κ--[C(Ph)CHC(Me)O]}] (), Ir{κ--[C(Ph)CHC(Me)O]}{κ--[CMeH-py]} (), and Ir{κ--[C(Ph)CHC(Me)O]}{κ--[acac]} (). The five-membered rings are orthogonally arranged with the oxygen atoms in in an octahedral environment of the iridium atom. Spiro iridafurans are aromatic.

Competition between ,,-Pincer and ,-Chelate Ligands in Platinum(II).

Replacement of the chloride ligand of PtCl{κ-,,-[py-CHR-py]} (R = H (), Me ()) and PtCl{κ-,,-[py-O-CH-O-py]} () by hydroxido gives Pt(OH){κ-,,-[py-CHR-py]} (R = H (), Me ()) and Pt(OH){κ-,,-[py-O-CH-O-py]} (). These compounds promote deprotonation of 3-(2-pyridyl)pyrazole, 3-(2-pyridyl)-5-methylpyrazole, 3-(2-pyridyl)-5-trifluoromethylpyrazole, and 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole. The coordination of the anions generates square-planar derivatives, which in solution exist as a unique species or equilibria between isomers.

Synthesis, Structure, and Photophysical Properties of Platinum(II) (,,') Pincer Complexes Derived from Purine Nucleobases†.

The synthesis of a series of Pt{κ-,,'-[L]}X (X = Cl, RC≡C) pincer complexes derived from purine and purine nucleosides is reported. In these complexes, the 6-phenylpurine skeleton provides the ,-cyclometalated fragment, whereas an amine, imine, or pyridine substituent of the phenyl ring supplies the additional '-coordination point to the pincer complex. The purine ,-fragment has two coordination positions with the metal (1 and 7), but the formation of the platinum complexes is totally regioselective.

Silyl-Osmium(IV)-Trihydride Complexes Stabilized by a Pincer Ether-Diphosphine: Formation and Reactions with Alkynes.

Complex OsH{κ-,,-[xant(PPr)]} () activates the Si-H bond of triethylsilane, triphenylsilane, and 1,1,1,3,5,5,5-heptamethyltrisiloxane to give the silyl-osmium(IV)-trihydride derivatives OsH(SiR){κ-,,-[xant(PPr)]} [SiR = SiEt (), SiPh (), SiMe(OSiMe) ()] and H. The activation takes place via an unsaturated tetrahydride intermediate, resulting from the dissociation of the oxygen atom of the pincer ligand 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(PPr)). This intermediate, which has been trapped to form OsH{κ-,-[xant(PPr)]}(PPr) (), coordinates the Si-H bond of the silanes to subsequently undergo a homolytic cleavage.

Rhodium-Promoted C-H Bond Activation of Quinoline, Methylquinolines, and Related Mono-Substituted Quinolines.

The C-H bond activation of methylquinolines, quinoline, 3-methoxyquinoline, and 3-(trifluoromethyl)quinoline promoted by the square-planar rhodium(I) complex RhH{κ-P,O,P-[xant(PPr)]} [; xant(PPr) = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene] has been systematically studied. Results reveal that the activation of the heteroring is preferred over the activation of the carbocycle, and the activated position depends upon the position of the substituent in the substrate. Thus, 3-, 4-, and 5-methylquinoline reacts with to quantitatively form square-planar rhodium(I)-(2-quinolinyl) derivatives, whereas 2-, 6-, and 7-methylquinoline quantitatively leads to rhodium(I)-(4-quinolinyl) species.

Reactions of an Osmium-Hexahydride Complex with 2-Butyne and 3-Hexyne and Their Performance in the Migratory Hydroboration of Aliphatic Internal Alkynes.

Reactions of the hexahydride OsH(PPr) () with 2-butyne and 3-hexyne and the behavior of the resulting species toward pinacolborane (pinBH) have been investigated in the search for new hydroboration processes. Complex reacts with 2-butyne to give 1-butene and the osmacyclopropene OsH(η-CMe)(PPr) (). In toluene, at 80 °C, the coordinated hydrocarbon isomerizes into a η-butenediyl form to afford OsH(η-CHCHCHCH)(PPr) ().

Ligand Design and Preparation, Photophysical Properties, and Device Performance of an Encapsulated-Type -Tris(heteroleptic) Iridium(III) Emitter.

The organic molecule 2-(1-phenyl-1-(pyridin-2-yl)ethyl)-6-(3-(1-phenyl-1-(pyridin-2-yl)ethyl)phenyl)pyridine () has been designed, prepared, and employed to synthesize the encapsulated-type -tris(heteroleptic) iridium(III) derivative Ir(κ-'L). Its formation takes place as a result of the coordination of the heterocycles to the iridium center and the -CH bond activation of the phenyl groups. Dimer [Ir(μ-Cl)(η-COD)] is suitable for the preparation of this compound of class [Ir(9h)] (9h = 9-electron donor hexadentate ligand), but Ir(acac) is a more appropriate starting material.

Osmathiazole Ring: Extrapolation of an Aromatic Purely Organic System to Organometallic Chemistry.

An osmathiazole skeleton has been generated starting from the cation of the salt [OsH(OH)(≡CPh)(IPr)(PPr)]OTf (; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CFSO) and thioacetamide; its aromaticity degree was compared with that of thiazole, and its aromatic reactivity was confirmed through a reaction with phenylacetylene. Salt reacts with the thioamide to initially afford the synthetic intermediate [OsH{κ--[NHC(CH)S]}(≡CPh)(IPr)(PPr)]OTf (). Thioamidate and alkylidyne ligands of couple in acetonitrile at 70 °C, forming a 1:1 mixture of the salts [OsH{κ--[C(Ph)NHC(CH)S]}(CHCN)(IPr)(PPr)]OTf () and [Os{κ--[CH(Ph)NHC(CH)S]}(CHCN)(IPr)]OTf ().

Acetylides for the Preparation of Phosphorescent Iridium(III) Complexes: Iridaoxazoles and Their Transformation into Hydroxycarbenes and -Tetradentate Ligands.

The preparation of three families of phosphorescent iridium(III) emitters, including iridaoxazole derivatives, hydroxycarbene compounds, and -tetradentate containing complexes, has been performed starting from dimers -[Ir(μ-η-C≡CR){κ--(MeCH-py)}] (R = Bu (), Ph ()). Reactions of with benzamide, acetamide, phenylacetamide, and trifluoroacetamide lead to the iridaoxazole derivatives Ir{κ--[C(CHBu)NC()O]}{κ--(MeCH-py)} (R = Ph (), Me (), CHPh (), CF ()) with a disposition of carbons and heteroatoms around the metal center. In 2-methyltetrahydrofuran and dichloromethane, water promotes the C-N rupture of the IrC-N bond of the iridaoxazole ring of to form amidate-iridium(III)-hydroxycarbene derivatives Ir{κ-[NHC()O]}{κ--(MeCH-py)}{═C(CHBu)OH} (R = Me (), CHPh (), CF ()).

Homogeneous catalysis with polyhydride complexes.

Roles of the hydrogen atoms attached to the metal center of transition metal polyhydride complexes, LMH ( ≥ 3), are analyzed for about forty types of organic reactions catalyzed by such class of species. Reactions involve nearly every main organic functional group and represent friendly environmental procedures of synthesis of relevant and necessary molecules in several areas ranging from energy and environment to medicine or pharmacology. Catalysts are mainly complexes of group 8 metals, along with rhenium and iridium, and manganese and cobalt to a lesser extent.

Metathesis between E-C(sp ) and H-C(sp ) σ-Bonds (E=Si, Ge; n=2, 3) on an Osmium-Polyhydride.

The silylation of a phosphine of OsH (P Pr ) is performed via net-metathesis between Si-C(sp ) and H-C(sp ) σ-bonds (n=2, 3). Complex OsH (P Pr ) activates the Si-H bond of Et SiH and Ph SiH to give OsH (SiR )(P Pr ) , which yield OsH {κ -P,η -SiH-[ Pr PCH(Me)CH SiR H]}(P Pr ) and R-H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first-order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state.

Alkynyl Ligands as Building Blocks for the Preparation of Phosphorescent Iridium(III) Emitters: Alternative Synthetic Precursors and Procedures.

Alkynyl ligands stabilize dimers [Ir(μ-X)(3b)] with a cis disposition of the heterocycles of the 3b ligands, in contrast to chloride. Thus, the complexes of this class─[Ir(μ-η-C≡CPh){κ-,-(CH-Isoqui)}] (Isoqui = isoquinoline) and [Ir(μ-η-C≡CR){κ-,-(MeCH-py)}] (R = Ph, Bu)─have been prepared in high yields, starting from the dihydroxo-bridged dimers [Ir(μ-OH){κ-,-(CH-Isoqui)}] and [Ir(μ-OH){κ-,-(MeCH-py)}] and terminal alkynes. Subsequently, the acetylide ligands have been employed as building blocks to prepare the orange and green iridium(III) phosphorescent emitters, Ir{κ-,-[C(CHPh)Npy]}{κ-,-(CH-Isoqui)} and Ir{κ-,-[C(CHR)Npy]}{κ-,-(MeCH-py)} (R = Ph, Bu), respectively, with an octahedral structure of carbon and nitrogen atoms.

C-Cl Oxidative Addition and C-C Reductive Elimination Reactions in the Context of the Rhodium-Promoted Direct Arylation.

A cycle of stoichiometric elemental reactions defining the direct arylation promoted by a redox-pair Rh(I)-Rh(III) is reported. Starting from the rhodium(I)-aryl complex RhPh{κ-P,O,P-[xant(PPr)]} (xant(PPr) = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene), the reactions include C-Cl oxidative addition of organic chlorides, halide abstraction from the resulting six-coordinate rhodium(III) derivatives, C-C reductive coupling between the initial aryl ligand and the added organic group, oxidative addition of a C-H bond of a new arene, and deprotonation of the generated hydride-rhodium(III)-aryl species to form a new rhodium(I)-aryl derivative. In this context, the kinetics of the oxidative additions of 2-chloropyridine, chlorobenzene, benzyl chloride, and dichloromethane to RhPh{κ-P,O,P-[xant(PPr)]} and the C-C reductive eliminations of biphenyl and benzylbenzene from [RhPh{κ-P,O,P-[xant(PPr)]}]BF and [RhPh(CHPh){κ-P,O,P-[xant(PPr)]}]BF, respectively, have been studied.

Dissimilarity in the Chemical Behavior of Osmaoxazolium Salts and Osmaoxazoles: Two Different Aromatic Metalladiheterocycles.

The preparation of aromatic hydride-osmaoxazolium and hydride-oxazole compounds is reported and their reactivity toward phenylacetylene investigated. Complex [OsH(OH)(≡CPh)(IPr)(PPr)]OTf (; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene, OTf = CFSO) reacts with acetonitrile and benzonitrile to give [OsH{κ--[C(Ph)NHC(R)O]}(NCR)(IPr)(PPr)]OTf (R = Me (), Ph ()) via amidate intermediates, which are generated by addition of the hydroxide ligand to the nitrile. In agreement with this, the addition of 2-phenylacetamide to acetonitrile solutions of gives [OsH{κ--[C(Ph)NHC(CHPh)O]}(NCCH)(IPr)(PPr)]OTf ().

Azolium Control of the Osmium-Promoted Aromatic C-H Bond Activation in 1,3-Disubstituted Substrates.

The hexahydride complex OsH(PPr) promotes the C-H bond activation of the 1,3-disubstituted phenyl group of the [BF] and [BPh] salts of the cations 1-(3-(isoquinolin-1-yl)phenyl)-3-methylimidazolium and 1-(3-(isoquinolin-1-yl)phenyl)-3-methylbenzimidazolium. The reactions selectively afford neutral and cationic trihydride-osmium(IV) derivatives bearing κ-- or κ--chelating ligands, a cationic dihydride-osmium(IV) complex stabilized by a κ--pincer group, and a bimetallic hexahydride formed by two trihydride-osmium(IV) fragments. The metal centers of the hexahydride are separated by a bridging ligand, composed of κ-- and κ--chelating moieties, which allows electronic communication between the metal centers.

Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid.

The reaction of the hexahydride OsH(PPr) with a P,Ge,P-germylene-diphosphine affords an osmium tetrahydride derivative bearing a Ge,P-chelate, which arises from the hydrogenolysis of a P-C(sp) bond. This Os(IV)-Ge(II) compound is a pioneering example of a bifunctional catalyst based on the coordination of a σ-donor acid, which is active in the dehydrogenation of formic acid to H and CO. The kinetics of the dehydrogenation, the characterization of the resting state of the catalysis, and DFT calculations point out that the hydrogen formation (the fast stage) exclusively occurs on the coordination sphere of the basic metal center, whereas both the metal center and the σ-donor Lewis acid cooperatively participate in the CO release (the rate-determining step).

-Tris(heteroleptic) Red Phosphorescent Iridium(III) Complexes Bearing a Dianionic ,,','-Tetradentate Ligand.

1-Phenyl-3-(1-phenyl-1-(pyridin-2-yl)ethyl)isoquinoline (HMeL) has been prepared by Pd(-XantPhos)-catalyzed "" to synthesize new phosphorescent red iridium(III) emitters (601-732 nm), including the carbonyl derivative Ir(κ--,'--,'-MeL)Cl(CO) and the acetylacetonate compound Ir(κ--,'--,'-MeL)(acac). The tetradentate 6e-donor ligand (6tt') of these complexes is formed by two different bidentate units, namely, an orthometalated 2-phenylisoquinoline and an orthometalated 2-benzylpyridine. The link between the bidentate units reduces the number of possible stereoisomers of the structures [6tt' + 3b] (3b = bidentate 3e-donor ligand), with respect to a [3b + 3b' + 3b″] emitter containing three free bidentate units, and it permits a noticeable stereocontrol.

Hydration of Aliphatic Nitriles Catalyzed by an Osmium Polyhydride: Evidence for an Alternative Mechanism.

The hexahydride OsH(PPr) competently catalyzes the hydration of aliphatic nitriles to amides. The main metal species under the catalytic conditions are the trihydride osmium(IV) amidate derivatives OsH{κ-,-[HNC(O)R]}(PPr), which have been isolated and fully characterized for R = Pr and Bu. The rate of hydration is proportional to the concentrations of the catalyst precursor, nitrile, and water.