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The Ni-catalyzed N-arylation of b-fluoroalkylamines with broad scope is reported for the first time. Use of the air-stable pre-catalyst (PAd2-DalPhos)Ni(o-tol)Cl allows for reactions to be conducted at room temperature (25 oC, NaOtBu), or by use of a commercially available dual-base system (100 oC, DBU/NaOTf), to circumvent decomposition of the N-(b-fluoroalkyl)aniline product. The mild protocols disclosed herein feature broad (hetero)aryl (pseudo)halide scope (X = Cl, Br, I, and for the first time phenol derived electrophiles), encompassing base sensitive substrates and enantioretentive transformations, in a manner that is unmatched by any previously reported catalyst system.

The first nickel-catalyzed N-arylation of amides with (hetero)aryl (pseudo)halides employing an organic amine base is described. By using a bis(cyclooctadienyl)nickel/8-[2-(dicyclohexylphosphinyl)phenyl]-1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantane catalyst mixture in combination with DBU/NaTFA as a dual-base system, a diversity of (hetero)aryl chloride, bromide, tosylate, and mesylate electrophiles were successfully cross-coupled with structurally diverse primary amides, as well as a selection of secondary amide, lac­tam, and oxazolidone nucleophiles.

A comparative study of the performance of (PN)M(N(SiMe3)2) (M = Mn, Fe, Co, and Ni) pre-catalysts supported by N-phosphinoamidinate ligation, as well as M(N(SiMe3)2)n (M = Li, Na, K, Mn, Fe, and Co) pre-catalysts, in the hydrosilative reduction of selected tertiary amide test substrates using PhSiH3 is reported. Encouraged by the performance observed herein for (PN)Ni(N(SiMe3)2) in the reduction of both N,N-dibenzylbenzamide and N,N-diisopropylbenzamide, further competitive testing involving the known complex (PN)Ni(NHdipp) (dipp = 2,6-diisopropylphenyl), as well as the new and crystallographically characterized mononuclear complexes (PN)Ni(OR) (R = 2,6-dimethylphenyl or tBu), revealed (PN)Ni(OtBu) to be particularly effective in such reduction chemistry, including transformations involving the secondary amides N-benzylbenzamide and caprolactam.

The development of Ni-catalyzed C-N cross-couplings of sulfonamides with (hetero)aryl chlorides is reported. These transformations, which were previously achievable only with Pd catalysis, are enabled by use of air-stable (L)NiCl(o-tol) pre-catalysts (L=PhPAd-DalPhos and PAd2-DalPhos), without photocatalysis. The collective scope of (pseudo)halide electrophiles (X=Cl, Br, I, OTs, and OC(O)NEt2 ) demonstrated herein is unprecedented for any reported catalyst system for sulfonamide C-N cross-coupling (Pd, Cu, Ni, or other). Preliminary competition experiments and relevant coordination chemistry studies are also presented.

We report herein on the results of our combined experimental/computational study regarding the catalytic performance of PAd-DalPhos (L1) in nickel-catalyzed ammonia arylation for primary aniline synthesis. Primary arylamine C–N reductive eliminations occurring from arylnickel(II) parent amido complexes of the type (L)Ni(Ph)(NH2) were modeled by use of density-functional theory (DFT) methods, for a series of L1 derivatives. The dual aims were to assess the effect of structural modifications to L1 on potentially rate-limiting C–N reductive elimination and to identify promising candidates for experimental inquiry. Increasing the steric demand of the Paryl groups from o-tolyl (in L1) to mesityl (in L16) resulted in a significant lowering of the barrier to C–N reductive elimination (ΔG⧧RE), which can be attributed in part to interactions between the ligand Paryl groups and the nickel-bound amido ligand, as observed in noncovalent interaction (NCI) plots of the reductive elimination transition-state structures....

We report herein on the synthesis of new heteroaryl analogues of PAd-DalPhos and related bis(di(o-tolyl)phosphino) ancillary ligand variants based on pyridine or thiophene backbone structures, and their application in nickel-catalyzed C(sp2)-N cross-couplings under challenging reaction conditions. The 3,4-disubstituted thiophene-based ancillary ligand ThioPAd-DalPhos (L8) was observed to be particularly effective in the nickel-catalyzed C(sp2)-N cross-coupling of primary alkylamines, and the derived precatalyst (L8)NiCl(o-tolyl) (C2) was found to offer improved performance versus the related PAd-DalPhos-derived precatalyst C1 in such transformations. In using C2, cross-couplings of various primary alkylamines and (hetero)aryl-X electrophiles (X = Cl, Br, OTs) proceeded under unprecedentedly mild reaction conditions (0.25–0.50 mol % Ni), including examples conducted at room temperature. Also reported herein are the results of our combined experimental/DFT computational study directed toward gaining insight...

We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)2) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+; d5–d8) in the isomerization–hydroboration of 1-octene, cis-4-octene, or trans-4-octene (1a–c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)2, (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6-iPr2C6H3) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydroboration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formati...

The competitive catalytic screening of 18 known and newly prepared Mor-DalPhos ligand variants in the palladium-catalyzed cross-coupling of chlorobenzene with aniline, octylamine, morpholine, indole, ammonia, or acetone is presented, including ligands derived from the new secondary phosphine HP(Me2Ad)2 (Me2Ad = 3,5-dimethyladamantyl). Although triarylphosphine ancillary ligand variants performed poorly in these test reactions, ligands featuring either PAd2 or P(Me2Ad)2 donors (Ad = 1-adamantyl) gave rise to superior catalytic performance. Multiple Mor-DalPhos variants proved effective in cross-couplings involving aniline, octylamine, or morpholine; conversely, only a smaller subset of ligands proved useful in related cross-couplings of indole, ammonia, or acetone. In the case of the N-arylation of indole, a Mor-DalPhos ligand variant featuring ortho-disposed PAd2 and dimethylmorpholino donor fragments (L13) proved superior to all other ligands surveyed, including the parent ligand Mor-DalPhos (L5). Conversely, L5 was found to be superior to all other ligands in the palladium-catalyzed monoarylation of ammonia. Ligand L6 (i.e., the P(Me2Ad)2 variant of L5) proved superior to all other ligands in the monoarylation of acetone and, with the exception of indole N-arylation, was the most broadly useful of the Mor-DalPhos ligands surveyed herein.

We report herein on the synthesis and catalytic application of a family of o-phenylene-bridged bisphosphine ancillary ligands featuring a bulky N-heterocyclic phosphine (NHP) donor fragment paired with an adjacent PR2 donor group (R = alkyl, aryl), whereby the incorporation of phosphorus into either a saturated or unsaturated heterocyclic ring serves as a means of modulating the donicity of the NHP fragment. Screening of these ancillary ligands in representative nickel-catalyzed C(sp2)–N cross-coupling test reactions allowed for the identification of one variant, featuring a saturated NHP structure and an adjacent diphenylphosphino donor group (i.e., NHP-DalPhos), as being particularly effective in reactions involving primary alkylamines. Notably, application of the derived precatalyst (NHP-DalPhos)NiCl(o-tolyl) (C1) enabled the typically challenging monoarylation of structurally diverse primary alkylamines with (hetero)aryl chlorides or bromides at room temperature. Also described are the results of our ...

The successful application of (DPEPhos)Ni(mesityl)Br (C1) as a pre-catalyst in the Suzuki–Miyaura cross-coupling of heteroaryl chlorides or bromides and heteroaryl boronic acids is reported. The use of C1 in this context allows for such reactions to be conducted under mild conditions (2 mol% Ni, 25 °C), including cross-couplings leading to unsymmetrical biheteroaryls. Successful transformations of this type involving problematic pyridinyl boronic acid substrates (10 mol% Ni, 60 °C) are also described.

The influence of ancillary ligand and nickel oxidation state in the nickel-catalyzed C(sp2)–N cross-coupling of aryl chlorides is examined by use of experimental and DFT methods for the first time, focusing on (L)NiCl and (L)Ni(o-tolyl)Cl pre-catalysts (PAd-DalPhos, L1; dppf, L2). Whereas Ni(II) pre-catalysts generally out-performed Ni(I) species in our study, the viability and in some cases superiority of Ni(I) pre-catalysts in challenging aminations is established. Computational analyses support the viability of Ni(0)/Ni(II) cycles featuring rate-limiting C–N reductive elimination, as well as parallel Ni(I)/Ni(III) mechanisms involving rate-limiting C–Cl oxidative addition.

Whereas the metal-catalyzed C(sp2)–N cross-coupling of cyclopropylamine with aryl electrophiles represents an attractive route to pharmaceutically relevant N-arylcyclopropylamines, few catalysts that are capable of effecting such transformations have been identified. Herein, the nickel-catalyzed C(sp2)–N cross-coupling of cyclopropylamine and related nucleophiles, including ammonium salts, with (hetero)aryl (pseudo)halides is reported for the first time, with the demonstrated scope of reactivity exceeding that displayed by all previously reported catalysts (Pd, Cu, or other). Our preliminary efforts to effect the N-arylation of cyclopropylamine with (hetero)aryl chlorides at room temperature by use of (L)NiCl(o-tolyl) precatalysts (L = PAd-DalPhos, C1; L = JosiPhos CyPF-Cy, C2) were unsuccessful, despite the established efficacy of C1 and C2 in transformations of other primary alkylamines. However, systematic modification of the ancillary ligand (L) structure enabled success in such transformations, with ...

A catalyst system capable of effecting the cross-coupling of ammonia or primary alkylamines with (hetero)aryl sulfamates, carbamates, or pivalates is reported for the first time. The air-stable nickel(II) pre-catalyst C1 tolerates a broad spectrum of heterocyclic functionality within both reaction partners, as well as ether, nitrile, pyrrole, trifluoromethyl, and boronate ester substituents. In the case of reactions involving primary alkylamines and (hetero)aryl sulfamates and carbamates, room-temperature cross-couplings were achieved.

The synthesis and/or NMR/X-ray characterization of a new series of (L)AuCl complexes is reported, featuring BippyPhos, AdJohnPhos, silyl ether based ligands including OTips-DalPhos, and PAd-DalPhos. These complexes, along with previously reported analogues featuring cataCXium-A, tBuJohnPhos, and Mor-DalPhos, were screened as precatalysts using LiB(C6F5)4·2.5Et2O as an activator in the hydrohydrazination of terminal aryl alkynes with hydrazine hydrate under unprecedentedly mild conditions (25 °C, 1 mol % Au). The precatalyst (cataCXium-A)AuCl proved to be particularly effective in such transformations, demonstrating useful scope.

Synthesis and characterization of the new air-stable pre-catalyst (DPEPhos)Ni(2-mesityl)Br (C1) is reported, along with the application of this pre-catalyst in the cross-coupling of secondary amines/azoles with activated (hetero)aryl chlorides to afford tertiary (hetero)anilines. The performance of C1 in these cross-couplings is competitive with some of the best and/or most widely employed nickel catalysts for such transformations.

The first examples of stoichiometric dehydrogenative B-H/C(sp3 )-H benzylic borylation reactions, which are of relevance to catalytic methylarene (di)borylation, are reported. These unusual transformations involving a (κ2 -P,N)Pt(η3 -benzyl) complex, and either pinacolborane or catecholborane, proceed cleanly at room temperature. Density functional calculations suggest that borylation occurs via successive σ-bond metathesis steps, whereby a PtII -H intermediate engages in C(sp3 )-H bond activation-induced dehydrogenation.

Previous reports in the literature have established the utility of 1,1′-bis(diphenylphosphino)ferrocene (DPPF, LPh) in the nickel-catalyzed cross-coupling of (hetero)aryl electrophiles with primary or secondary amines. In an effort to evaluate the effect of varying the PR2-donor groups on catalytic performance in such transformations, a series of 10 structurally varied 1,1′-bis(bis(alkyl/aryl)phosphino)ferrocene ancillary ligands (LX) were systematically examined in selected competitive test cross-couplings of (hetero)aryl halides with furfurylamine, morpholine, and indole employing Ni(COD)2/LX catalyst mixtures. In addition to the excellent performance observed for the parent ligand LPh in a number of the test transformations explored, selected dialkylphosphino (e.g., DiPPF, LiPr) and meta-disubstituted diarylphosphino variants of LPh also proved highly effective. In particular, the electron-deficient ligand variant LCF3 featuring 3,5-bis(trifluoromethyl)phenyl groups on phosphorus was found to exhibit s...

The nickel-catalyzed cyclization of in situ generated ortho-chlorobenzophenone hydrazone derivatives, to afford 3-(hetero)aryl-1H-indazoles, is documented for the first time. The product 1H-indazoles can be transformed subsequently in a one-pot procedure into 1,3-di(hetero)aryl-1H-indazoles via copper-catalyzed N-arylation with (hetero)aryl bromides.

The synthesis and characterization of the new air-stable precatalyst (L1)Ni(o-tol)Cl (C1; where L1 = JosiPhos CyPF-Cy) is reported, along with the results of a comparative reactivity survey involving C1 and analogous PAd-DalPhos- and DPPF-containing precatalysts (C2 and C3, respectively) in representative nickel-catalyzed C(sp2)–N cross-coupling reactions. Precatalyst C1 was found to be competitive with, and in some cases complementary to, C2 in the monoarylation of ammonia and primary alkylamines with (hetero)aryl chlorides, including in otherwise challenging room temperature transformations. (Pseudo)halide comparison studies involving the cross-coupling of furfurylamine at room temperature revealed that in contrast to C2 precatalyst C1 performs less effectively with aryl bromides. Whereas C3 was found to be ineffective for such transformations, this DPPF-derived precatalyst proved superior to C1 and C2 in reactions involving the secondary dialkylamine test substrate morpholine.

The utility of RockPhos, Ad-BippyPhos, JosiPhos (CyPF-tBu), and Mor-DalPhos in palladium-catalyzed C–O cross-coupling reactions involving aliphatic alcohols and (hetero)aryl halides under analogous conditions was examined, both at room temperature and at elevated temperature (90 °C). In general, the RockPhos-based catalyst system proved superior, especially at room temperature, but catalysts based on the other ligands examined also proved effective across a range of C–O cross-couplings, in some cases providing better catalytic performance than RockPhos. New reactivity was established in terms of the scope of room temperature reactions. Proof-of-principle examples of such cross-couplings involving aryl mesylates were also demonstrated.

We report convenient and high-yielding syntheses of new phosphine-functionalized dihydroimidazolium salts and demonstrate their utility as ligand precursors for Buchwald–Hartwig amination. Several examples of the general formula [1-Mes-3-{2-(PR2)phenyl}imidazolidin-2-ylium][BF4] have been prepared, where phosphines of varying steric and electronic properties (R = Ph (9), Cy (10), 1-Ad (11)) are tethered by an o-phenylene group. The synthesis was not adaptable to N-aryl groups other than mesityl, giving unexpected phosphonium salt species instead. The synthesis was adapted to flexible benzyl-linked variants of the formula [1-Ar-3-{2-(PCy2)benzyl}imidazolidin-2-ylium][BF4], which allowed more steric variation of the dihydroimidazolium N-aryl group (Ar = Mes (21), Dipp (22)). A preliminary study of these hybrid NHC/P ligands in Buchwald–Hartwig amination catalysis (in situ precatalyst formation) revealed 11 to be the most active of the series. Premixing the isolated free NHC ligand 1-Mes-3-{2-(PAd2)phenyl}im...

An examination of the [{Pd(cinnamyl)Cl}(2)]/Mor-DalPhos (Mor-DalPhos = di(1-adamantyl)-2-morpholinophenylphosphine) catalyst system in Buchwald-Hartwig aminations employing ammonia was conducted to better understand the catalyst formation process and to guide the development of precatalysts for otherwise challenging room-temperature ammonia monoarylations. The combination of [{Pd(cinnamyl)Cl}(2)] and Mor-DalPhos afforded [(κ(2)-P,N-Mor-DalPhos)Pd(η(1)-cinnamyl)Cl] (2), which, in the presence of a base and chlorobenzene, generated [(κ(2)-P,N-Mor-DalPhos)Pd(Ph)Cl] (1 a). Halide abstraction from 1 a afforded [(κ(3)-P,N,O-Mor-DalPhos)Pd(Ph)]OTf (5), bringing to light a potential stabilizing interaction that is offered by Mor-DalPhos. An examination of [(κ(2)-P,N-Mor-DalPhos)Pd(aryl)Cl] (1 b-f) and related precatalysts for the coupling of ammonia and chlorobenzene at room temperature established the suitability of 1 a in such challenging applications. The scope of reactivity for the use of 1 a (5 mol %) encompassed a range of (hetero)aryl (pseudo)halides (X = Cl, Br, I, OTs) with diverse substituents (alkyl, aryl, ether, thioether, ketone, amine, fluoro, trifluoromethyl, and nitrile), including chemoselective arylations.

The first nickel-catalyzed N-arylation of amides with (hetero)aryl (pseudo)halides is reported, enabled by use of the air-stable pre-catalyst (PAd-DalPhos)Ni(o-tolyl)Cl (C1). A range of structurally diverse primary amides and lactams were cross-coupled successfully with activated (hetero)aryl chloride, bromide, triflate, tosylate, mesylate, and sulfamate electrophiles.

An efficient one-pot transition metal-free procedure for the synthesis of new pyrazolo[1,5-a]quinoxalin-4(5H)-ones from easily prepared 1-(2-chlorophenyl-5-ethylcarboxylate)pyrazoles and various primary alkylamines is described. The key steps involved in the synthesis of the new 5,6-fused ring system are the formation of an amide intermediate followed by an intramolecular N-arylation reaction via nucleophilic aromatic substitution.

Preparation of enols: when treated with [{Pd(cinnamyl)Cl}(2)]/cataCXium A (nBuPAd(2), Ad=adamantyl) under an atmosphere of CO, aryl ketones react with aryl halides in a carbonylative C-O coupling reaction to form (Z)-vinyl benzoates.

We report the extension and optimization of the [Pd(cinnamyl)Cl]2/DalPhos catalyst system, previously found effective for the mono-α-arylation of acetone, to the mono-α-arylation of a variety of carbonyl-containing compounds with aryl halides and heteroaryl halides. Aryl methyl ketones, heteroaryl methyl ketones, propiophenones, malonates, and methoxyacetone can be α-arylated under relatively mild conditions and in good yields. We also report the limitations of the ligand/catalyst system towards other classes of carbonyl-containing compounds.

While Mor-DalPhos/Pd precatalyst mixtures have in general proven to be highly effective for the monoarylation of ammonia employing a range of (hetero)aryl (pseudo)halide cross-coupling partners, we have observed previously that 1-bromo-2-(phenylethynyl)benzene (Ar*Br) is a challenging substrate for this catalyst system. We report herein on our efforts to examine some possible modes of catalyst inhibition by this substrate. Treatment of [CpPd(allyl)] with Mor-DalPhos in the presence of Ar*Br afforded [(κ2-P,N-Mor-DalPhos)Pd(Br)(Ar*)] (1; 85%), which was transformed into [(κ3-P,N,O-Mor-DalPhos)Pd(Ar*)]+OTf– (3; 83%) upon treatment with AgOTf. The characterization of 3 establishes the ability of the Mor-DalPhos ligand to adopt a κ3-P,N,O structure, which may influence the course of some Pd-catalyzed amination processes. While treatment of 1 with AgOTf in the presence of ammonia, or alternatively treatment of 3 with ammonia, resulted in the clean formation of [(κ2-P,N-Mor-DalPhos)Pd(NH3)(Ar*)]+OTf– (2), our e...

The efficacy of phosphine-free Pt precatalysts including PtCl2 and (COD)PtCl2 in promoting the cyclohydroamination of primary as well as secondary alkyl/arylamines tethered to α-olefins is demonstr...

The catalytic utility of [κ2-{3-iPr2P-2-O-indene}Rh(COD)] (COD = η4−1,5-cyclooctadiene) 1a in the hydroformylation of styrenes was examined. Complex 1a was shown to be an effective pre-catalyst in benzene and tetrahydrofuran, exhibiting good conversions to aldehyde and high branched-to-linear selectivity for styrene, 4-chlorostyrene, and 4-methylstyrene under reasonably mild conditions (1000 psi syngas; 1.8 mol% Rh, 45 °C, 2–5 h). Under analogous conditions, the iridium congener of 1a proved inactive for hydroformylation. The synthesis and crystallographic characterization of the new complex [κ2-{2-iPr2PC6H4O}Rh(COD)] 2 is also reported; the catalytic performance of 2 in the hydroformylation of styrene was found to be comparable to that of 1a under similar catalytic conditions.

The syntheses of 2-(di-tert-butylphosphino)-N,N-dimethylaniline (L1, 71%) and 2-(di-1-adamantylphosphino)-N,N-dimethylaniline (L2, 74 %), and their application in Buchwald-Hartwig amination, are reported. In combination with [Pd(allyl)Cl](2) or [Pd(cinnamyl)Cl](2), these structurally simple and air-stable P,N ligands enable the cross-coupling of aryl and heteroaryl chlorides, including those bearing as substituents enolizable ketones, ethers, esters, carboxylic acids, phenols, alcohols, olefins, amides, and halogens, to a diverse range of amine and related substrates that includes primary alkyl- and arylamines, cyclic and acyclic secondary amines, N-H imines, hydrazones, lithium amide, and ammonia. In many cases, the reactions can be performed at low catalyst loadings (0.5-0.02 mol % Pd) with excellent functional group tolerance and chemoselectivity. Examples of cross-coupling reactions involving 1,4-bromochlorobenzene and iodobenzene are also reported. Under similar conditions, inferior catalytic performance was achieved when using Pd(OAc)(2), PdCl(2), [PdCl(2)(cod)] (cod = 1,5-cyclooctadiene), [PdCl(2)(MeCN)(2)], or [Pd(2)(dba)(3)] (dba = dibenzylideneacetone) in combination with L1 or L2, or by use of [Pd(allyl)Cl](2) or [Pd(cinnamyl)Cl](2) with variants of L1 and L2 bearing less basic or less sterically demanding substituents on phosphorus or lacking an ortho-dimethylamino fragment. Given current limitations associated with established ligand classes with regard to maintaining high activity across the diverse possible range of C-N coupling applications, L1 and L2 represent unusually versatile ligand systems for the cross-coupling of aryl chlorides and amines.

A series of Ru-based complexes supported by P,N-substituted indene or indenide ligands have been prepared and tested for activity in the atom transfer radical addition of CCl4 to alkenes. The catalytic performance was found to be influenced by the charge and substitution pattern of the P,N ligand and other coligands, as well as the nature of the counteranion, with the best of these catalysts being effective at low catalyst loadings and under mild conditions.

Heating of [(COD)M(κ2-3-PiPr2-2-NMe2-indene)]+X- (M = Rh or Ir; X = BF4, PF6; COD = η4-1,5-cyclooctadiene) in a mixture of water and THF (48 h, 60 °C) afforded the neutral (COD)M(κ2-P,O) complexes (M = Rh, 5a, 80%; M = Ir, 5b, 74%). Similarly, thermolysis of [(COD)M(κ2-3-P(S)iPr2-2-NMe2-indene)]+BF4- (M = Rh or Ir) in a mixture of water and CH2Cl2 (14 h, 60 °C) produced the neutral (COD)M(κ2-P(S),O) complexes (M = Rh, 13a, 91%; M = Ir, 13b, 90%). Subsequent preparation of 1-PiPr2-2-indanone (8, 91%) enabled the non-hydrolytic synthesis of 5b in 70% isolated yield via treatment with 0.5[(COD)IrCl]2 in the presence of NEt3. Lithiation of (o-PiPr2)phenol followed by quenching with 0.5[(COD)IrCl]2 afforded the neutral (COD)Ir(κ2-P,O) complex 10 (91%). Single-crystal X-ray diffraction data are provided for 5b, 10, 13a, and 13b. Whereas 5a, 13a, and 13b performed poorly as catalysts for the hydrogenation of alkenes, the known complex (COD)Ir(OPh)(PCy3) 2 as well as 5b and 10 proved to be excellent catalysts for...

New Au(I) complexes featuring ligands of the type κ1-3-R2P-indene (κ1-1a, R = iPr; κ1-1b, R = Ph) and κ1-1-R2P-2-Me2N-indene (κ1-1c, R = iPr; κ1-1d, R = Ph) were prepared and structurally characterized. Dicoordinate neutral complexes (κ1-1)AuCl (2−5) were prepared by reacting 1 with Me2SAuCl, with isolated yields ranging from 56 to 88%. Addition of a second equivalent of 1a to 2 resulted in formation of the tricoordinate neutral species (κ1-1a)2AuCl (6; 69%). By treating 6 with AgOTf, the corresponding cationic complex [(κ1-1a)2Au]+OTf- ([7]+OTf-; 72%) was obtained. The catalytic performance of these new Au(I) compounds in the hydrosilylation of various aldehydes was compared to that of catalyst systems derived from a combination of R3P (R = Et, nBu, tBu, Cy, or Ph) or N-heterocyclic carbene ligands and Me2SAuCl. While for the phosphine-substituted indene complexes, a catalyst mixture of 3 mol % 2 and 20 mol % 1a was found to be optimal, a catalyst derived from 3 mol % Me2SAuCl and 20 mol % Et3P, nBu3P, o...

A family of neutral, cationic, and formally zwitterionic Rh(I) and Ir(I) complexes featuring 1-PiPr2-2-NMe2-indene (3a), 3-PiPr2-2-NMe2-indene (3b), or 3-PiPr2-2-NMe2-indenide (3c) ligands have been prepared and structurally characterized. Whereas treatment of 3a with 0.5 equiv of [(COD)RhCl]2 afforded (COD)RhCl(κ1-P,N-3a) (4a) in 96% isolated yield, [(COD)M(κ2-P,N-3a)]+X- ([5a]+PF6-, M = Rh; [6a]+SO3CF3-, M = Ir) complexes were obtained in 14% and 41% isolated yield from 3a and the appropriate in-situ-prepared [(COD)M(THF)2]+X- precursor. The isomeric complexes [(COD)M(κ2-P,N-3b)]+X- ([5b]+X-, M = Rh; [6b]+X-, M = Ir) were prepared using a similar protocol employing NEt3, with isolated yields ranging from 37% to 94% depending on the identity of M and X. The zwitterionic complexes (COD)M(κ2-P,N-3c) (5c, M = Rh; 6c, M = Ir) were prepared in 89% and 93% isolated yield, either upon treatment of [5b]+X- or [6b]+X- with NaN(SiMe3)2 or via addition of 0.5 equiv of [(COD)MCl]2 to [3c]Li. The Rh(I) complexes (CO)...

The first examples of acetone mono-α-arylation at room temperature are described, enabled by use of a [Pd(cinnamyl)Cl]2 /JosiPhos catalyst system. (Hetero)aryl chloride, bromide, and iodide electrophiles featuring or lacking ortho-substitution, and comprising a range of functionalities (e.g., alkoxy, cyano, fluoro, trifluoromethyl, or alkenyl) and heteroaryl motifs (e.g., pyrrole, pyridine, isoquinoline, quinoline, quinaldine, (benzo)thiophene, benzothiazole, or benzodioxole) were successfully accommodated. Proof-of-principle experiments confirm that other (hetero)aryl methyl ketones can also be employed in such room temperature mono-α-arylations. The established substrate scope is the most extensive reported to date for acetone mono-α-arylation under any conditions, and more generally represents the first room temperature ketone mono-α-arylations employing a structurally diverse set of (hetero)aryl chlorides.

The ability of neutral Rh and Ir phosphinoenolate complexes of the type (COD)M(κ2-3-PiPr2-2-O-indene) (M = Rh, 2a; M = Ir, 2b; COD = η4-1,5-cyclooctadiene) to mediate the addition of triethylsilane to styrene was explored under various reaction conditions in which the solvent, temperature and substrate ratio were altered. Throughout the course of these catalytic studies, head-to-head performance comparisons were made with Wilkinson’s catalyst ((PPh3)3RhCl; 3) and Crabtree’s catalyst ( [ ( COD ) Ir ( PCy 3 ) ( Py ) ] + PF 6 - ; Cy = cyclohexyl; Py = pyridine; 4). While 2a proved to be an active catalyst for dehydrogenative silylation, exhibiting selectivity for E-1-triethylsilyl-2-phenylethene (5a) comparable to that of 3 under appropriate conditions, the Ir analogue 2b displayed rather poor catalytic productivity. In contrast, 4 exhibited good catalytic activity, generating 5a as well as 1-triethylsilyl-1-phenylethane (5c) as major products. Crystallographic data for 2a · 0.25CH2Cl2 are also reported.

Treatment of 1-PiPr2-indene or 1-PiPr2-2-NMe2-indene (1a) with elemental sulfur afforded 3-iPr2P(S)-indene or 1-iPr2P(S)-2-NMe2-indene (4a) in 81% and 85% isolated yield, respectively. Addition of 4a to [(COD)M(THF)2]+BF4- afforded the corresponding [(COD)M(kappa2-N,S-4a)]+BF4- complexes (M = Rh, 5a, 76%; M = Ir, 5b, 59%; COD = eta4-1,5-cyclooctadiene), which were found to exhibit temperature-dependent NMR spectral features that were rationalized in terms of a dynamic process involving M-NMe2 dissociation, rotation about the indenyl-NMe2 bond, inversion at nitrogen, and re-coordination to M. Analysis of variable-temperature NMR data collected for 5a and 5b each yielded a value for DeltaG(double dagger) of ca. 14 kcal/mol for this process. Exposure of 5a or 5b to NaN(SiMe3)2 generated the corresponding (COD)M(kappa2-C,S-1-iPr2P(S)-2-NMe2-(C1-indenyl)) complex (M = Rh, 6a, 70%; M = Ir, 6b, 86%) in which the metal is incorporated into an M-C-P-S ring via coordination to the indenyl ring in an eta1-fashion, as well as to sulfur. Alternatively, complex 6b was prepared cleanly via lithiation of 4a followed by treatment with 0.5 equiv of [(COD)IrCl]2. The ability of 5a,b and 6a,b to mediate the addition of triethylsilane to styrene was also explored, and their performance was compared with that of Wilkinson's Catalyst ((PPh3)3RhCl) and Crabtree's catalyst ([(COD)Ir(PCy3)(Py)]+PF6-; Cy = cyclohexyl; Py = pyridine). Single-crystal X-ray diffraction data are provided for 4a, 2-NMe2-3-iPr2P(S)-indene (4b), 6a, and 6b.

Synthesis of a series of rhodium complexes bearing a tridentate bis(8-quinolyl)methylsilyl (NSiN) ligand is reported. Bis(8-quinolyl)methylsilane (1) reacted with (PPh3)3RhCl via oxidative addition at the Si−H bond to afford (NSiN)Rh(H)Cl(PPh3) (2). Several coordinatively unsaturated, 16-electron complexes were synthesized, including the cationic complex [(NSiN)Rh(H)(PPh3)][B(C6F5)4] (3) and the neutral complex (NSiN)Rh(CH2Ph)2 (12). The X-ray structures of 3 and 12 reveal a square-pyramidal geometry about the Rh center, with the silyl group occupying an apical position. The dicationic complex [(NSiN)Rh(CH3CN)3][OTf]2 (11), synthesized by reaction of [(NSiN)RhCl2]2 (10) with 2 equiv of AgOTf in acetonitrile, exhibits moderate activity as a catalyst for alkene hydrogenation and for H/Cl exchange between Ph3SiH and CH2Cl2. Complex 2 reacts with 2 equiv of PhCH2MgCl in benzene to afford (NSiN)Rh(CH2Ph)Cl(PPh3) (6). Chlorination of 2 by DBU in CH2Cl2 afforded the solvent-activated Rh(III) product (NSiN)RhCl2(...

The structural and reactivity properties of new Pt(II) and Au(III) complexes featuring κ 2 -2-NMe 2 -3-P i Pr 2 -indene (1b) or κ 2 -2-NMe 2 -3-P i Pr 2 -indenide (1c) ancillary ligands are examined. Complex [1c]AuMe 2 (3), a formally zwitterionic relative of the neutral complex [1b]PtMe 2 (2b), was prepared in 41% isolated yield from [lc]Li and 0.5 [Me 2 AuCl] 2 . Whereas 2b was observed to react with H 2 O, Ph 3 SiH, and PhSiH 3 over 48 h at 50 °C, complex 3 proved unreactive under these reaction conditions. Similarly, 2b exhibited modest catalytic activity for the addition of triethylsilane to styrene, while no conversion was achieved by use of 3 as a catalyst. Observations made during the course of examining the catalytic abilities of [1b]PtClMe (7) and 7/AgX (X = BF 4 or OTf) for this addition reaction prompted the rational preparation of the dinuclear cation [{(1b)PtMe} 2 Cl]+BF 4 - ([8]+BF 4 - ; 61%) as well as the monomeric cations [(1b)PtMeL]+BF 4 - (L = SMe 2 , [9] + BF 4 - , 77%; L = MeCN, [10] + BF 4 - , 84%). Single-crystal X-ray diffraction data are provided for 2b, 3, [8] + BF 4 - , and [9]+BF 4 - .

Treatment of trichlorovinylsilane with 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol (3 equiv.) in the presence of excess triethylamine produces the fluorous vinylsilane, 1, which can be isolated in 74% yield as an analytically pure oil. The addition of bis(pentafluorophenyl)borane to 1 produces the fluorous boranes, 2a–2b, as an analytically pure, isomeric mixture of anti-Markovnikov and Markovnikov hydroboration products in 38% isolated yield. Compounds 2a–2b are soluble in both arene solvents and perfluoro(methylcyclohexane). Treatment of 2a–2b with excess trimethylphosphine generates a mixture of products, including the Lewis adduct, 3, which can be isolated as an analytically pure oil in 15% yield. When exposed to either dimethylaminopyridine or piperidine at room temperature, the trimethylphosphine donor in 3 is cleanly displaced, based on in situ 31P NMR studies; under similar conditions, triethylamine does not react with 3. Addition of either dimethylaminopyridine or piperidine to 2a–2b, followed by purification and subsequent treatment with an excess of either hydrogen chloride or p-toluenesulfonic acid, results in cleavage of the Si–O linkages and the regeneration of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol.Key words: fluorous, borane, silane, Lewis acid.

1-(Diphenylphosphino)-2-(dimethylamino)indene (2c) has been prepared in 61% yield and upon exposure to Al2O3 is mostly isomerized to 3-(diphenylphosphino)-2-(dimethylamino)indene (2d) (2c:2d ≈ 1:3); similarly, 1-(diisopropylphosphino)-2-(dimethylamino)indene (2a) is only partially converted to the corresponding C3 isomer (2b) upon treatment with Al2O3 (2a:2b ≈ 3:1). In contrast, 1-(diisopropylphosphino)indene (6a) has been prepared in 92% yield and is easily converted to 3-(diisopropylphosphino)indene (6b) on passing over Al2O3; 0.5 equiv of [(η4-COD)RhCl]2 and 6b combine to give [(κ1-P-6b)(η4-COD)RhCl] (7) in 79% yield. Treatment of either 2-(dimethylamino)indene (1) or 6b with a stoichiometric amount of n-BuLi, followed by the addition of 0.5 equiv of [(η4-COD)RhCl]2, produces the (η5-indenyl)rhodium(I) complexes 8 (53% yield) and 9 (88% yield), respectively, in which the pnictogen donor is apparently not coordinated to the rhodium center. When 2.5 equiv of n-BuLi is combined with 6b and subsequently tr...

Reactions involving Fe(NO)2(CO)2 and the bis(phosphine) ligands bis(diphenylphosphino)methane (DPPM), bis(diphenylphosphino)acetylene (DPPA), 1,6-bis(diphenylphosphino)hexane (DPPH), and 1,4-bis(diphenyl phosphino)benzene (DPPB) have been examined. From these reactions, the mononuclear complex, Fe(κ1-DPPM)(NO)2(CO) 3, linear dinuclear species of the type Fe2(µ-L)(NO)4(CO)2 (L = Ph2PCH2PPh2 4, Ph2PC[Formula: see text]CPPh2 5, Ph2PCH2(CH3)4CH2PPh2 6, and Ph2P(p-C6H4)PPh2 7), and macrocyclic dinuclear species of the type Fe2(µ-L)2(NO)4 (L = Ph2PCH2PPh2 8 and Ph2PC[Formula: see text]CPPh2 9) were isolated and spectroscopically characterized. For 4, 5, 8, and 9, the solid-state molecular structures of the products were determined by use of single-crystal X-ray diffraction techniques. Key words: dinitrosyliron, iron nitrosyls, dinuclear macrocycles, bis(phosphine) complexes.

Herein we establish the utility of a three-coordinate (N-phosphinoamidinate)cobalt(amido) pre-catalyst that is capable of effecting challenging alkene isomerization/hydroboration processes at room temperature, leading to the selective terminal addition of the boron group.

The complex [Rh(η3-benzyl)(dippe)] (1; dippe=bis(diisopropylphosphino)ethane=(ethane-1,2-diyl)bis[diisopropylphosphine]) reacted cleanly with Mes*PH2 (2; Mes*=2,4,6-tBu3C6H2) to provide a new Rh species [Rh(H)(dippe)(L)] (3), L being the 2,3-dihydro-3,3-dimethyl-1H-phosphindole ligand 4 (=tBu2C6H2(CMe2CH2PH)) (Scheme 1). Complex 3 was converted to the corresponding chloride [Rh(Cl)(dippe)(L)] (6) when treated with CH2Cl2, whereas the dimeric species [Rh2{μ-tBu2C6H2(CMe2CH2P)}(μ-H)(dippe)2] (7) was formed upon thermolysis in toluene (Scheme 2). The structures of 6 and 7⋅C7H8 were determined by X-ray crystallography. Complexes 1 and 3 served as catalyst precursors for the dehydrogenative coupling of C−H and P−H bonds in the conversion of 2 to 4 (Scheme 3). Deuteration studies with Mes*PD2 exposed a complex series of bond-activation pathways that appear to involve C−H activation of the dippe ligand by the Rh-atom (Schemes 4 and 5)

Indenylsilanes bearing organic and organometallic substituents have been prepared in order to probe the effect of substitution on the rate of [1,5]-silicon shifts in this class of compounds. In an attempt to prepare 1,1,3-tris(trimethylsilyl)indene (7), the hitherto unknown silicon-functionalized bis(trimethylsilyl)dibenzo[a,d]fulvalene (9) was unexpectedly generated; this species was characterized by use of both NMR spectroscopy and X-ray crystallography and was rationally prepared in 68% yield from 3,3‘-bis(1-(trimethylsilyl))indene (16). The molecular dynamics of 1,3-dimethyl-1-(trimethylsilyl)indene (18) and the crystallographically characterized chromium complex (η6-1,3-dimethyl-1-exo-(trimethylsilyl)indene)tricarbonylchromium (22) were examined by use of 1D-selective inversion and 2D-EXSY NMR techniques; surprisingly, the presence of chromium and methyl substituents has a negligible effect on the rate of [1,5]-silicon shifts (ΔG⧧ = 23−24 kcal mol-1) versus the parent compound 1-(trimethylsilyl)inden...

The electrochemical reduction of the intermediates generated from the reaction of Co(I)TPP− (TPP=tetraphenyl porphyrin) with benzyl chloride (PhCH2Cl) or butyl bromide (BuBr) have been studied by use of electrochemistry and IR-spectroelectrochemistry. The rates of formation of PhCH2Co(III)TPP, and of decomposition of the reduction product [PhCH2Co(II)TPP]− are much faster than those found for the corresponding BuBr system. The decomposition of [RCo(II)TPP]− proceeds via homolytic CoC bond cleavage, to generate the corresponding organic radical at negative potential, where RCo(III)TPP can be reduced to [RCo(II)TPP]−. A mechanism involving the reaction of organic radicals with the porphyrin ring and transfer from cobalt to a nitrogen of the pyrrole ring, leading to the formation of an N-alkyl cobalt porphyrin complex is proposed, which is consistent with the destruction of catalyst during electrocatalytic carboxylation and reduction of an organic halide.