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Direct C-H functionalization of privileged and biologically relevant azoles and indoles represents an important chemical transformation in molecular science. Despite significant progress in the palladium-catalyzed regioselective C-H functionalization of azoles and indoles, the use of abundant and less expensive nickel catalyst is underdeveloped. In the recent past, the nickel-catalyzed regioselective C-H alkylation, arylation, alkenylation and alkynylation of azoles and indoles have been substantially explored, which can be applied to the complex organic molecule synthesis. In this Account, we summarize the developments in nickel-catalyzed regioselective functionalization of azoles and indoles with a considerable focus on the reaction mechanism.

We describe the synthesis of new NNN-oxazolinyl-pincer nickel complexes and their application in the transfer hydrogenation of ketones. Achiral NNN-ligands, R′2-oxazolinyl-2-C6H4-NH-C(O)CH2NEt2 [(R′2-OxNNNEt2)–H; R’ = H (3a), R′ = Me (3b)], and chiral ligands, (R)-R′-oxazolinyl-2-C6H4-NH-C(O)CH2NEt2 [(R)-(R′-OxNNNEt2)–H; R′ = Ph (3c), R′ = CH2Ph (3d), R′ = iPr (3e), R′ = CH2iPr (3f)], were efficiently synthesized. Treatment of these ligands with (DME)NiCl2 afforded the desired amido-pincer nickel complexes, (R′2-OxNNNEt2)NiCl [R′ = H (4a), R′ = Me (4b)] and (R′-OxNNNEt2)NiCl [R′ = Ph (4c), R′ = CH2Ph (4d), R′ = iPr (4e), R′ = CH2iPr (4f)], in good yields. All the ligand precursors and nickel complexes were thoroughly characterized by various analytical techniques. The molecular structures of 4a, 4d and 4f were established by X-ray crystallography. The developed nickel complexes were found to be efficient catalysts for the transfer hydrogenation of ketones using iPrOH as a viable hydrogen source. Enantioselectivity in hydrogenation was not observed with the developed chiral catalysts.

Nickel-catalyzed enantioselective hydrogenation of enamines leading to the efficient synthesis of 3- R -Boc-amino-4-(2,4,5-trifluorophenyl)butyric esters, the key intermediate of the blockbuster antidiabetic drug ( R )-SITAGLIPTIN, is described. The sitagliptin motifs were isolated in more than 99% yield and with 75-92% ee using the earth-abundant nickel catalyst. Upon chiral resolution with ( R )- and ( S )-1-phenylethylamines, the partially enantioenriched ( R )- and ( S )-Boc-3-amino-4-(2,4,5-trifluorophenyl)butanoic acids provided > 99.5% ee of the crucial sitagliptin intermediate. The asymmetric hydrogenation protocol was scaled up to 10 g with consistency in yield and ee , and has been reproduced in multiple batches.

Alkenylation of benzothiazoles and related azoles with alkenyl bromides is achieved employing the well-defined and air-stable nickel complexes, (bpy)NiBr2 and [Ni(bpy)3][NiBr4], as catalysts. Numerous electronically distinct alkenyl bromides efficiently coupled with substituted benzothiazoles, oxazoles, and benzimidazoles under the catalytic conditions to afford 2-alkenylated azoles. An extensive mechanistic study of the alkenylation of benzothiazole using (bpy)NiBr2 highlights a single-electron transfer process for the reaction involving the two-step one-electron oxidative addition of alkenyl bromide. The substrate benzothiazole plays a significant and diverse role in the reaction, and C–H bond cleavage is reversible in nature. Detailed kinetic analysis and control reactivity studies are indicative of a Ni(I)/Ni(III) pathway for the alkenylation comprising the rate-influencing reductive elimination step.

A mild and efficient nickel-catalyzed method for the chemo and regioselective coupling of unactivated alkyl chlorides with the C–H bond of indoles and pyrroles at 60 °C is described., A mild and efficient nickel-catalyzed method for the coupling of unactivated primary and secondary alkyl chlorides with the C–H bond of indoles and pyrroles is described which demonstrates a high level of chemo and regioselectivity. The reaction tolerates numerous functionalities, such as halide, alkenyl, alkynyl, ether, thioether, furanyl, pyrrolyl, indolyl and carbazolyl groups including acyclic and cyclic alkyls under the reaction conditions. Mechanistic investigation highlights that the alkylation proceeds through a single-electron transfer (SET) process with Ni(i)-species being the active catalyst. Overall, the alkylation follows a Ni(i)/Ni(iii) pathway involving the rate-influencing two-step single-electron oxidative addition of alkyl chlorides.

Nickel-catalyzed regioselective C–H bond alkenylation of indoles and related heteroarenes with alkenyl bromides is accomplished under relatively mild conditions. This method allows the straightforward synthesis of C-2 alkenylated indoles employing an air-stable and well-defined nickel catalyst, (bpy)NiBr2, providing a solution to the limitations associated with hydroindolation and oxidative alkenylation. The reaction conceded the coupling of indole derivatives with various alkenyl bromides, such as aromatic and heteroaromatics, α- and β-substituted as well as exo- and endo-cyclic alkenyl compounds. An extensive mechanistic investigation, including controlled study, reactivity experiments, kinetics and labeling studies, and EPR and XPS analyses, highlights that the alkenylation proceeds through a single-electron transfer process comprising an odd-electron oxidative addition of alkenyl bromide. Furthermore, the alkenylation operates via a probable Ni(I)/Ni(III) pathway involving the rate-limiting C–H nickel...

Selective hydrogenation of nitriles and alkynes is crucial considering the vast applications of reduced products in industries and in the synthesis of bioactive compounds. Particularly, the late 3d transition metal catalysts (manganese, iron, cobalt, nickel and copper) have shown promising activity for the hydrogenation of nitriles to primary amines, secondary amines and imines. Similarly, semihydrogenation of alkynes to E- and Z-alkenes by 3d metals is adequately successful both via the transfer hydrogenation and by using molecular hydrogen. The emergence of 3d transition metals in the selective synthesis of industrially relevant amines, imines and alkenes makes this protocol more attractive. Herein, we provide a concise overview on the late 3d transition metal-catalyzed hydrogenation of nitriles to amines and imines as well as semihydrogenation of alkynes to alkenes.

The nickel system (THF)2NiBr2/phen has recently been shown as an efficient catalyst for the C–H bond alkynylation of diverse heteroarenes with (triisopropylsilyl)alkynyl bromide via monodentate chelation assistance. Herein, we report an extensive mechanistic investigation for the direct alkynylation of indoles involving the well-defined nickel catalyst, which features a coordinative insertion pathway of alkynyl bromide with the Ni(II) catalyst. Catalytic relevant nickel complexes, (phen)NiCl2 (5), (phen)2NiCl2 (6) and [(phen)3Ni]·NiCl4 (7) were isolated, and the complexes 6 and 7 were structurally characterized. Well-defined complexes were as competent as the in situ generated catalyst system (THF)2NiBr2/phen for the alkynylation of indoles. Various controlled studies and reactivity experiments were performed to understand the probable pathway for the alkynylation reaction. Kinetics analysis highlights that the complex (phen)NiX2 acts as a precatalyst, and the involvement of substrate indole and LiOtBu ar...

Regioselective C(2)-H difluoroalkylation of C-3 unsubstituted indoles with commonly available fluoroalkyl bromides is successfully achieved employing a simple nickel catalyst system, (DME)NiCl2 /Xantphos. This methodology shows excellent regioselectivity and exhibits a broad substrate scope. Various functional groups, such as -OMe, -F, and -Br, are tolerated on the indole backbone to give the difluoroalkylated products in moderate to good yields. Preliminary mechanistic findings demonstrate that the reaction is homogeneous in nature and involves a radical manifold. Synthetic utility of this nickel-catalyzed method is demonstrated by synthesizing melatonin receptor antagonist Luzindole derivative.

The quinolinyl-based pincer nickel complex, κN,κN,κN-{C9H6N-(μ-N)-C6H4–NMe2}NiCl [(QNNNMe2)NiCl; (1)] has recently been demonstrated to be an efficient and robust catalyst for the alkylation of azoles with alkyl halides under copper-free conditions. Herein, we report the detailed mechanistic investigation for the alkylation of azoles catalyzed by (QNNNMe2)NiCl (1), which highlights an iodine-atom transfer (IAT) mechanism for the reaction involving a NiII/NiIII process. Deuterium labeling experiments indicate reversible cleavage of the benzothiazole C–H bond, and kinetic studies underline a fractional negative rate order with the substrate benzothiazole. The involvement of an alkyl radical during the alkylation is validated by radical clock and external additive experiments. An active intermediate species (QNNNMe2)Ni(benzothiazolyl) (5a) has been isolated and structurally characterized. The complex (QNNNMe2)Ni(benzothiazolyl) (5a) is found to be the resting state of catalyst 1. Kinetic analysis of electron...

Nickel-catalyzed oxidative C(sp2)–H/C(sp3)–H coupling of indoles with toluene derivatives is successfully achieved in the presence of 2-iodobutane as the oxidant. This method allows the selective C-2 benzylation of indoles with toluene derivatives over the alkylation with 2-iodobutane and permits the coupling of diversified indoles via the monochelation assistance. The reaction proceeded through a single-electron-transfer (SET) process, wherein both the C–H nickelation of indole and the C–H activation of toluene derivatives have a significant effect on the entire reaction rate. The synthetic utility of this nickel-catalyzed protocol is demonstrated by the facile removal of the directing group and by the convenient synthesis of the melatonin receptor antagonist Luzindole derivatives.

An efficient solvent-free nickel-catalyzed method for C-H bond arylation of arenes and indoles has been developed, which proceeds expeditiously through chelation assistance. The reaction is highly selective for mono-arylation and tolerates sensitive and structurally diverse functionalities, such as halides, ethers, amines, indole, pyrrole and carbazole. This reaction represents the first example of a nickel-catalyzed C-H arylation by monochelate assistance and symbolizes a rare precedent in solvent-free C-H arylation. Mechanistic investigations by various controlled reactions, kinetic studies, and deuterium labeling experiments suggest that the arylation follows a single electron transfer (SET) pathway involving the turnover-limiting C-H nickelation process.

(Quinolinyl)amido-ligated palladium(II) complexes have been synthesized and applied in the catalytic C–H bond arylation of benzothiazoles. The tridentate ligand precursors R2N-C(O)CH2-(NH)-C9H6N [(R2NNN8-Q)–H; R2N = morpholinyl, Me-N-piperazinyl] and the pincer palladium complexes [κN,κN,κN-{R2N-C(O)CH2-(μ-N)-C9H6N}]PdX [(R2NNN8-Q)PdX {R2N = Et2N, morpholinyl, Me-N-piperazinyl; X = OAc or Cl}] were efficiently synthesized, and characterized by various analytical techniques. The iodo derivative (Et2NNN8-Q)PdI was obtained in excellent yield by the treatment of the complex (Et2NNN8-Q)PdCl with KI. The molecular structures of complexes (Et2NNN8-Q)Pd(OAc) (2a), (Et2NNN8-Q)PdCl (3a) and (Et2NNN8-Q)PdI (4a) were elucidated by X-ray crystallography. Complex 3a was found to be the most efficient catalyst for direct C–H bond arylation of substituted benzothiazoles with diverse aryl iodides using a mild base, K2CO3. The working catalyst system 3a is highly robust and can be recycled and reused several times for the arylation of benzothiazole without loss of catalytic activity. Preliminary mechanistic investigations using controlled studies and kinetic analysis have been performed, which greatly support a molecular mechanism for the arylation.

This chapter describes the chemistry of phosphine-ether and phosphine-thioether ligated copper(I) complexes. The synthesis and characterization of some of these complexes are discussed, including the X-ray structure description. Particularly, the photophysical properties of copper(I) complexes have been highlighted in detail. Some of the copper(I) complexes show excellent photoluminescence property and are comparable with the noble metal counterpart. Catalytic activity of copper(I) complexes ligated with phosphine-ether and phosphine-thioether has been discussed in detail.

A nickel-catalyzed direct C-2 alkylation of indoles through monodentate-chelation assistance has been described. This reaction proceeds via an unusual strategy by the use of a well-designed and defined (quinolinyl)amido–nickel catalyst, [{κN,κN,κN-Et2NCH2C(O)(μ-N)C9H6N}Ni(OAc)], providing a solution to the limitations associated with bidentate-chelate auxiliaries. The method allows coupling of indoles with various unactivated primary and secondary alkyl halides with ample substrate scope. This uniquely strategized alkylation proceeded through crucial C–H activation and via an alkyl radical intermediate. The reaction by this approach represents a rare example of Ni-catalyzed monodentate-chelate-assisted C–H functionalization.

The quinoline-based pincer nickel(II) complexes κN,κN,κN-{R2N-C6H4-(μ-N)-C9H6N}NiX ((R2NNNQ)NiCl: R = Me, 2a; R = Et, 2b) were synthesized by the reaction of the ligand precursors (R2NNNQ)H (R = Me, 1a; R = Et, 1b) with (DME)NiCl2 in the presence of Et3N. Similarly, the pincer nickel(II) derivatives (R2NNNQ)NiX (R = Me, X = Br, 3a; R = Et, X = Br, 3b; R = Me, X = OAc, 4a) were obtained by treatment of the ligands (R2NNNQ)H with the nickel precursor (THF)2NiBr2 or Ni(OAc)2. All of these complexes were characterized by 1H and 13C NMR spectroscopy as well as by elemental analysis. Further, the molecular structures of 2a and 3a,b were elucidated by X-ray crystallography. Complex 2a is found to be an efficient catalyst for the direct C–H bond alkylation of substituted benzothiazoles and oxazoles with various unactivated alkyl halides containing β-hydrogens under mild reaction conditions. The catalyst 2a is very robust and was recycled and reused five times for the alkylation reaction without a decrease in its ...

Quinolinamide-based pincer copper(II) complexes, κN,κN,κN-{C9H6N-(μ-N)-C(O)CH2NEt2}CuX [(QNNNEt2)CuX (X = Cl, 2; X = Br, 3; X = OAc, 4)], were synthesized by the reaction of ligand (QNNNEt2)-H (1) with CuX2 (X = Cl, Br or OAc) in the presence of Et3N. The reaction of (QNNNEt2)-H with CuX (X = Cl, Br or OAc) also afforded the Cu(II) complexes 2, 3 and 4, respectively, instead of the expected Cu(I) pincer complexes. The formation of Cu(II) complexes from Cu(I) precursors most likely occurred via the disproportionation reaction of Cu(I) into Cu(0) and Cu(II). A cationic complex [(QNNNEt2)Cu(CH3CN)]OTf (5) was synthesized by the treatment of neutral complex 2 with AgOTf. On the other hand, the reaction of (QNNNEt2)-H (1) with [Cu(MeCN)4]ClO4 produced cationic Cu(I) complex, [(QNN(H)NEt2)Cu(CH3CN)]ClO4 (6), in good yield. All complexes 2–5 were characterized by elemental analysis and HRMS measurements. Furthermore, the molecular structures of 2, 3 and 4 were elucidated by X-ray crystallography. Complex 4 crystallizes in a dimeric and catemeric pattern. The cationic complex 5 was found to be an efficient catalyst for the Kumada coupling reaction of diverse nonactivated alkyl chlorides and bromides with alkyl magnesium chloride under mild reaction conditions.

A metal-free method for the regioselective C-3 acetoxylation of the N-substituted indoles with PhI(OAc)2 is described under mild reaction conditions. This method tolerates a broad range of functional groups with moderate to good yields. The π-electron-deficient aryl-substituents on the N-atom of indoles and the acidic reaction medium remarkably favor C-3 acetoxylation.

Regioselective C–H bond palladation of the hybrid pincer-type ligands, 3-R2PO-C6H4-1-CH2NiPr2 [R2POCNiPr2–H; R = Ph (1a), R = Et2N (1b)] has been described to accomplish mono- and binuclear palladacycles. The reactions of the ligands R2POCNiPr2–H (1a, 1b) with Pd(COD)Cl2 in the presence of K3PO4 afforded the mononuclear pincer complexes {κP,κC,κN-2-(R2PO)-C6H3-6-(CH2NiPr2)}PdCl (R2POCNiPr2)PdCl [R = Ph (2a), R = Et2N (2b)], whereas similar reactions in the presence of Et3N produced the chloro-bridged binuclear palladacycles [{κP,κC-2-(R2PO)-C6H3-4-(CH2NiPr2)}(μ-Cl)Pd]2 {R = Ph (4a), R = Et2N (4b)} via the regioselective ligands C(2)–H and C(4)–H bond activation, respectively. Similarly, the reaction of a previously reported ligand iPr2POCNiPr2–H (1c) with Pd(COD)Cl2 in the presence of Et3N affords a chloro-bridged binuclear complex [{κP,κC-2-(iPr2PO)-C6H3-4-(CH2NiPr2)}(μ-Cl)Pd]2 (4c) via the regioselective C(4)–H bond palladation. On the contrary, using Pd(OAc)2 instead of Pd(COD)Cl2 in the palladation reaction of 1a, in the presence or absence of base, leads to the exclusive formation of the acetate-bridged binuclear palladacycle [{κP,κC-2-(Ph2PO)-C6H3-4-(CH2NiPr2)}(μ-OAc)Pd]2 (5a). Mechanistic detail for this regioselective C–H bond activation to achieve mono- and binuclear palladacycles has been demonstrated, which highlights that the coordinating ability of the external base, sterics between the coordinated base and N-arm of the POCN ligand as well as the electrophilicity of the palladium center are crucial to the regioselective palladation. The palladium complex 4c was shown to be the active catalyst for the direct arylation of azoles with aryl iodides under mild reaction conditions.

Application of palladacycle complexes in catalytic organic transformation is rapidly expanding. This chapter is mainly focused on the use of palladacycle precatalysts in C H bond functionalizations, as well as an overview of palladacycle intermediates in directed C H bond functionalization reactions. The described palladacycle precatalysts are more efficient and more selective than the traditional palladium complexes for C H bond functionalization processes. The second part of the chapter summarizes the involvement of palladacycle intermediates in various directed C H bond functionalizations that are proposed with experimental evidence. Some of the palladacycle intermediates described are shown to be competent as catalyst precursors. It has been demonstrated that the formation of palladacycle (precatalyst or intermediate) makes the C H functionalization process more facile, because of the high stability associated with palladacycles.

Inexpensive cobalt catalysts derived from N-heterocylic carbenes (NHC) allowed efficient catalytic C-H bond arylations on heteroaryl-substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri-ortho-substituted biaryls. Likewise, challenging direct alkylations with β-hydrogen-containing primary and even secondary alkyl chlorides proceeded on pyridyl- and pyrimidyl-substituted arenes and heteroarenes. The cobalt-catalyzed C-H bond functionalizations occurred efficiently at ambient reaction temperature with excellent levels of site-selectivities and ample scope. Mechanistic studies highlighted that electron-deficient aryl chlorides reacted preferentially, while the arenes kinetic C-H bond acidity was found to largely govern their reactivity.

A nitrogen and phosphorus ligand-free catalytic system derived from inexpensive [(diglyme)NiBr2] allowed for efficient direct CH bond alkylations of heteroarenes with unactivated β-hydrogen-containing alkyl halides under basic reaction conditions.

Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products--that is, secondary alkyl arenes--with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts--specifically 'pincer'-ligated iridium complexes--and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.

The adamantyl-substituted pincer-ligand precursor AdPCP-H [(AdPCP = κ3-C6H3-2,6-(CH2PAd2)2); Ad = 1-adamantyl] has been synthesized by the reaction of 1,3-dibromoxylene with di-1-adamantylphosphine in the presence of triethylamine. Treatment of AdPCP-H with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) affords the pincer-ligated complex (AdPCP)IrHCl, which was crystallographically characterized. Dehydrohalogenation of (AdPCP)IrHCl either with LiBEt3H or with KOtBu, under hydrogen atmosphere, yields the hydrides (AdPCP)IrH2 and (AdPCP)IrH4. (AdPCP)IrH2 catalyzes dehydrogenation of alkanes with a level of activity comparable to that of the previously reported (tBuPCP)IrH2, while it is thermally much more robust than the tBuPCP analogue, as well as iPrPCP or tBuPOCOP pincer complexes.

The short-bite aminobis(phosphonite), PhN{P(-OC10H6(mu-S)C10H6O-)}2 (2), containing a mesocyclic thioether backbone is synthesized by either treating PhN(PCl2)2 with 2 equiv of thiobis(2,2'-naphthol) or reacting chlorophosphite (-OC10H6(mu-S)C10H6O-)PCl (1) with aniline in the presence of a base. Treatment of 2 with an equimolar amount of Pd(COD)Cl2 in the presence of H2O affords a P-N-P-bridged and P,S-metalated binuclear complex, [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2Pd2Cl2{P(-OC10H6(mu-S)C10H6O-)(O)-kappaP,kappaS}2] (3), whereas the same reaction with 2 equiv of Pd(COD)Cl2 in the presence of H2O and Et3N produces the mononuclear anionic complex [{(-OC10H6(mu-S)C10H6O-)P(O)-kappaP,kappaS}PdCl2](Et3NH) (5). By contrast, reaction of 2 with 2 equiv of Pd(COD)Cl2 and H2O in the absence of Et3N gives the hydrogen phosphonate coordinated complex [{(-OC10H6(mu-S)C10H6O-)P(OH)}PdCl2] (4) which converts to the anionic complex in solution or in the presence of a base. Compound 2 on treatment with Pt(COD)X2 (X = Cl or I) afforded P-coordinated four-membered chelate complexes [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2PtX2] (6 X = Cl, 7 X = I). The crystal structures of compounds 2, 3, 5, and 7 are reported. Compound 3 is the first example of a crystallographically characterized binuclear palladium complex containing a bidentate bridging ligand and its hydrolyzed fragments forming metallacycles containing a palladium-phosphorus sigma bond. All palladium complexes proved to be very good catalysts for the Suzuki-Miyaura and Mizoroki-Heck cross-coupling and amination reactions with excellent turnover numbers (TON up to 1.46 x 105 in the case of the Suzuki-Miyaura reaction).

Large bite bisphosphite ligand, 2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2 (2), is obtained by reacting chlorophosphite, {-OC10H6(μ-S)C10H6O-}PCl (1) with 2,6-pyridinedimethanol in presence of triethylamine.Treatment of 2 with aqueous solution of H2O2 or elemental sulfur resulted in the formation of bis(oxide) or bis(sulfide) derivatives, 2,6-C5H3N{CH2OP(E)(–OC10H6)(μ-S)(C10H6O–)}2 (3, E = O; 4, E = S) in quantitative yield.The 10-membered cationic chelate complex, [RuCl(η6-C10H14)η2-2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2-κP,κP]Cl (5) is produced in the reaction between [Ru(p-cymene)(μ-Cl)(Cl)]2 and bisphosphite 2, whereas the neutral chelate complex, cis-[Rh(CO)Cl{2,6-C5H3N{CH2OP(–OC10H6(μ-S)C10H6O–)}2}-κP,κP] (6) is isolated in the reaction of 2 with 0.5 equiv.of [Rh(CO)2Cl]2.Compound 2 on treatment with M(COD)Cl2 (M = Pd, Pt) produce the chelate complexes, [MCl2{η2-2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2}-κP,κP] (7, M = Pd;10, M = Pt).Similarly the reaction of bisphosphite 2 with Pd(COD)MeCl affords cis-[PdMe(Cl)η2-2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2-κP,κP] (8).Treatment of 2 with [Pd(η3- C3H5)Cl]2 in the presence of AgClO4 furnish the cationic complex, [Pd(η3-C3H5)η2-2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2-κP,κP]ClO4 (9). The binuclear complex, [Au2Cl2{2,6-C5H3N{CH2OP(–OC10H6)(μ-S)(C10H6O–)}2}-κP,κP] (11) is obtained in the reaction of compound 2 with two equiv. of AuCl(SMe2), where the ligand exhibits bridged bidentate mode of coordination. All the complexes are characterized by the 1H NMR, 31P NMR, elemental analysis and mass spectroscopy data. The cationic ruthenium complex 5 is proved to be an active catalyst for the hydrogenation of styrene and α-methyl styrene., © Elsevier

Group 11 metal complexes of the mesocyclic thioether aminophosphonites [-OC 10 H 6 (μ-S)C 10 H 6 O-]PNC 4 H 8 E {2a: E = O; 2b: E = NMe; IUPAC names: 4-(dinaphtho[2,1-d:1',2'-g][1,3,6,2 ]dioxathiaphosphocin-4-yl)morpholine (2a), 1-(dinaphtho[2,1-d:1',2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)-4-methylpiperazine (2b)} are reported. Thioether aminophosphonites 2a and 2b react with CuX (X = Cl, Br, and I) in a 1:1 molar ratio to give the tricoordinate, dimeric complexes [{[{-OC 10 H 6 (μ-S)C 10 H 6 O-}PNC 4 H 8 E-kP ]Cu(μ-X)} 2 ] (4a: E = O, X = Cl; 4b: E = NMe, X = Cl; 5a: E = O, X = Br; 5b: E = NMe, X = Br; 6a: E = O, X = I; 6b: E = NMe, X = I), whereas with 2:1 molar ratios monomeric complexes of the type [{ [-OCioH6(μ-S)C 10 H 6 O-]PNC 4 H 8 O-kP )2CuX] (7a: E = O, X = Cl; 7b: E = NMe, X = Cl; 8a: E = O, X = Br; 8b: E = NMe, X = Br; 9a: E = O, X = I; 9b: E = NMe, X = I) are obtained in excellent yield. The P,S-chelated cationic complexes [{ [-OC 10 H 6 (μ-S)C 10 H 6 O -]PNC 4 H 8 E-kP,kS} 2 Cu ]BF4 (lOa: E = O; lOb: E = NMe) are obtained when 2a and 2b are treated with half an equivalent of [(MeCN) 4 Cu]BF 4 . Similarly, the silver complexes [{[{-OC 10 H 6 (μ-S)C 10 H 6 O-}PNC 4 H 8 E-kP,kS]-AgCF 3 SO 3 } 2 ] (lla: E = 0: lib: E = NMe) and [{[-OC 10 H 6 (μ-S)C 10 H 6 O -]PNC4H8E-kP,kS )Ag(PPh 3 )]CF 3 SO 3 (12a: E = O; 12b: E = NMe) are synthesized by the treatment of thioether aminophosphonites 2a and 2b with AgOTf and [Ag(PPh 3 )][OTf], respectively. Reactions of 2a and 2b with [AuCl(SMe 2 )] produce the simple monomeric gold(I) complexes [([-OC 10 H 6 (μ -S)C 10 H 6 O -]PNC 4 H 8 E-kP}AuCl] (13a: E = 0; 13b: E = NMe). The iodo derivatives [{[-OC 10 H 6 (μ-S)-CioH60-]PNC 4 H 8 E-kP}AuI] (14a: E = 0; 14b: E = NMe) are obtained by the halide-exchange reaction of 13a and 13b with Cul at room temperature. The structures of complexes 5a, 7a, 8a, 13a, 13b, and 14a are confirmed by single-crystal X-ray diffraction studies. In all of these complexes, the sulfur atom in the mesocyclic ring shows coordinative interaction towards the phosphorus atom, and in 5a, 7a, 8a, and 14a towards the metal center as well.

A metal-free method for the regioselective C-3 acetoxylation of the N-substituted indoles with PhI(OAc)2 is described under mild reaction conditions. This method tolerates a broad range of functional groups with moderate to good yields. The π-electron-deficient aryl-substituents on the N-atom of indoles and the acidic reaction medium remarkably favor C-3 acetoxylation.

Transition metal complexes of bis(2-diphenylphosphinoxynaphthalen-1-yl) methane (1) are described. Bis(phosphinite) 1 reacts with Group 6 metal carbonyls, [Rh(CO)(2)Cl](2), anhydrous NiCl2, [Pd(C3H5)Cl](2)/AgBF4 and Pt(COD)I-2 to give the corresponding 10-membered chelate complexes 2, 3 and 5-8. Reaction of 1 with [Rh(COD)Cl](2) in the presence of AgBF4 affords a cationic complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappa P, kappa P}]BF4 (4). Treatment of 1 with AuCl(SMe2) gives mononuclear chelate complex, [(AuCl){Ph2P(-OC10H6)(mu-CH2)(C10H6O-) PPh2-kappa P, kappa P}] (9) as well as a binuclear complex, [Au(Cl){mu-Ph2P(-OC10H6)(mu-CH2)(C10H6O-) PPh2- kappa P, kappa P} AuCl] (10) with ligand 1 exhibiting both chelating and bridged bidentate modes of coordination respectively. The molecular structures of 2, 6, 7, 9 and 10 are determined by X-ray studies. The mixture of Pd(OAc)(2) and 1 effectively catalyzes Suzuki cross-coupling reactions of a range of aryl halides with aryl boronic acid in MeOH at room temperature or at 60 degrees C, giving generally high yields even under low catalytic loads. The cationic rhodium(I) complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-) PPh2-kappa P, kappa P}]BF4 (4) catalyzes the hydrogenation of styrenes to afford the corresponding alkyl benzenes in THF at room temperature or at 70 degrees C with excellent turnover frequencies.

Well-defined and efficient POCN-ligated palladium complexes have been developed for the direct C-H bond arylation of azoles with aryl iodides. The phosphinite-amine pincer ligands 1-(R2PO)-C6H4-3-(CH2N(i)Pr2) [(R2)POCN(iPr2)-H; R = (i)Pr (), R = (t)Bu ()] and corresponding palladium complexes {2-(R2PO)-C6H3-6-(CH2N(i)Pr2)}PdCl [((R2)POCN(iPr2))PdCl; R = (i)Pr (), R = (t)Bu ()] were synthesized in good yields. Treatment of palladium complex with KI and AgOAc afforded the complexes ((iPr2)POCN(iPr2))PdI () and ((iPr2)POCN(iPr2))Pd(OAc) (), respectively. Similarly, the reaction of with benzothiazolyl-lithium produces the ((iPr2)POCN(iPr2))Pd(benzothiazolyl) () complex in a quantitative yield. The pincer palladium complex efficiently catalyzes the C-H bond arylation of benzothiazole, substituted-benzoxazoles and 5-aryl oxazoles with diverse aryl iodides in the presence of CuI as a co-catalyst under mild reaction conditions. This represents the first example of a pincer palladium complex being applied for the direct C-H bond arylation of any heterocycle with low catalyst loading. A preliminary mechanistic investigation reveals that palladium nanoparticles are presumably not the catalytically active form of and supports the direct involvement of the catalyst , with complex being a probable key intermediate in the catalytic reaction.

The title reaction proceeds under ambient temperature and low catalyst loading with excellent chemo- and site-selectivities for a broad substrate scope.

Large-bite bisphosphite ligand 1,3-C(6)H(4){OPOC(10)H(6)(mu-S)C(10)H(6)O}(2) (3), is obtained by reacting chlorophosphonite {OC(10)H(6)(mu-S)C(10)H(6)O}PCl (2) with resorcinol in the presence of triethylamine. Treatment of 3 with CuCl in 1:1 molar ratio produces a 1D-coordination polymer [CuCl{(-OC(10)H(6)(mu-S)C(10)H(6)O-) P(-OC(6)H(4)O-)P(-OC(10)H(6)(mu-S)C(10)H(6)O-)}-kappa P,kappa P](infinity) (4) in good yield. Similar reaction of 3 with two equivalents of AuCl(SMe(2)) affords a dinuclear complex, [Au(2)Cl(2){(-OC(10)H(6)(mu-S)C(10)H(6)O-) P(-OC(6)H(4)O-)P(-OC(10)H(6)(mu-S)C(10)H(6)O-)}-kappa P,kappa P] (5). Single crystal X-ray structures of the ligand 3 and the complexes 4 and 5 are reported. The gold complex 5 shows dimeric structure supported by strong Au center dot center dot center dot Au aurophilic interactions. (C) 2009 Elsevier B. V. .

Copper(I) complexes of short-bite aminobis(phosphonite), PhN{P(-OC(10)H(6)(mu-S)C(10)H(6)O-)}(2) (1) have been synthesized. Reactions of 1 with an excess of CuX (X = Cl, Br, and I) afforded the ligand-bridged binuclear complexes, [PhN(PR-kappa P)(2){Cu(mu-X)(MeCN)}(2)] (2, X Cl; 3, X = Br; 4, X = 1; R = -OC(10)H(6)(mu-S)C(10)H(6)O-), whereas treatment with 0.5 equiv. of [Cu(MeCN)(4)]PF(6) produces the mononuclear bischelated cationic complex, [(PhN(PR-kappa P)(2)}(2)Cu](PF(6)) (5). Single crystal X-ray structures of complexes 3 and 4 are reported. Complex 3 shows strong pi-pi stacking interactions between the naphthyl moieties, whereas complex 4 shows ligand-supported Cu center dot center dot center dot Cu metallophilic interactions. (C) 2008

A facile and less expensive monophosphinite ligand 2-(diphenylphosphinoxy)-naphthyl, C10H7OPPh2(1) has been synthesized from the reaction of β-naphthol with chlorodiphenylphosphine. The mixture of Pd(OAc)2 and 1 catalyzes the Suzuki cross-coupling of a variety of aryl halides with aryl boronic acids at room temperature or at 60°C, giving generally high yields even under low catalytic loads. The effect of solvent, base and catalyst loading on the coupling reaction of aryl halide with arylboronic acid is also described., © Elsevier

Ruthenium(II), copper(I) and silver(I) complexes of large bite bisphosphinite Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2 (1) are described. Reactions of bisphosphinite 1 with [Ru(η6-p-cymene)(μ-Cl)Cl]2 and RuCl2(PPh3)3 afford mono- and bis-chelate complexes [RuCl(η6-p-cymene){η2-Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2-κP,κP}]Cl (2) and trans-[RuCl2{η2-Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2-κP,κP}2] (3), respectively. Treatment of 1 with CuX (X = Cl, Br and I) furnish 10-membered chelate complexes of the type [Cu(X){η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}] (4, X = Cl; 5, X = Br; 6, X = I), whereas [Cu(MeCN)4]PF6 affords a bis-chelated cationic complex [Cu{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}2][PF6] (7). Reaction between 1 and AgOTf produce both mono- and bis-chelated complexes [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}(SO3CF3)] (8) and [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}2][SO3CF3] (9), respectively; whereas the similar reaction of 1 with[Ag(OTf)PPh3] affords chelate complex of the type [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}(PPh3)(SO3CF3)] (10). All the complexes were characterized by 1H NMR, 31P NMR, elemental analysis and mass spectrometry, including low-temperature NMR studies in the case of silver complexes. The molecular structures of 4 and 6 are determined by X-ray diffraction studies. Ruthenium complexes 2 and 3 promote catalytic hydrogenation of styrene and phenylacetylene with good turnover numbers., © Elsevier

The molecule of the title compound, C10H7OP(S)(C6H5)(2) or C22H17OPS, exhibits distorted tetrahedral geometry about the P atom. The P=S bond of 1.9355 (4)angstrom is shorter than that found in Ph3P=S [1.950 (3)angstrom] because the replacement of one carbon on phosphorus by oxygen increases the effective electronegativity of the P atom, thereby enhancing p pi-d pi back-donation from a lone-pair orbital of the S atom.

The title compound, C10H7OP(Se)(C6H5)2 or C22H17OPSe, is isomorphous and isostructural with its sulfur analog and shows a distorted tetra­hedral geometry about the P atom. The P=Se bond of 2.0890 (5) A is shorter than that of 2.106 (1) A found in Ph3P=Se because the replacement of one carbon on phospho­rus by oxygen increases the effective electronegativity of the P atom, thereby enhancing pπ–dπ back-donation from a lone-pair orbital of the chalcogen atom and shortens the P=Se bond.