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A remarkable intermolecular dehydrative coupling reaction with the formation of a C-C bond was found for the vinylidene complex 2 a, yielding the dinuclear bisvinylidene complex 4 a. Complex 2 a containing 1-hydroxyindan moiety was first formed from the reaction of o-propynyl benzaldehyde 1 a with [Ru]-Cl ([Ru]=Cp(PPh3 )2 Ru) by a cyclization process. For analogous aldehyde 1 b containing an additional 1,3-dioxolane group on the aryl ring, similar intermolecular coupling yields the dinuclear bisvinylidene complex 4 b. However, the fluoro group on the aryl ring in aldehyde 1 c inhibits the coupling reaction, giving only the vinylidene complex 2 c. For the reactions of [Ru]-Cl in MeOH with compounds 1 f, 1 g and 1 h, each with a ketone functionality, cyclization gives vinylidene complexes 2 f, 2 g and 2 h, respectively. However, no similar intermolecular coupling was observed, instead, the intramolecular dehydration yields 8 f, 8 g and 8 h, respectively. In CDCl3 , catalytic cyclization is observed for the o-propynylphenyl ketone 1 h with [Ru]-Cl at 50 °C giving the isochromene products 14 h. Furthermore, treatment of the o-propynylaryl α,β-unsaturated ketones 1 k-m and 1 n with [Ru]-Cl in MeOH affords the corresponding vinylidene complexes 10 k-m and 11 n each with 1-benzosuberone moiety in the presence of NH4 PF6 . These intramolecular cyclization products were formed by the addition of Cβ onto the terminal carbon of the alkene moiety. All these reaction products were characterized by spectroscopic methods. In addition, structures of complexes 4 a, and 10 l were confirmed by single crystal X-ray diffraction analysis.

The coupling reaction of N-propargyl semi-salen compound 1d on [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) generates the carbene complex 3d containing a substituted 2H-chromene unit in 7 d. The precursor vinylidene complex 2d is isolated from the reaction of the propargyl group of 1d with [Ru]-Cl in 12 h. Addition of an o-cresol moiety to Cα and Cβ of the vinylidene ligand of 2d takes place in a longer reaction time to yield 3d. Reactions of [Ru]-Cl with other analogous compounds 1a, 1b, and 1c, in excess, also afford carbene complexes 3a, 3b, and 3c, respectively, in 48 h via a similar coupling process. Their precursor vinylidene complexes 2a, 2b, and 2c are also observed in 12 h. Structures of 2 and 3 are determined on the basis of spectroscopic data. The solid state structure of the dppe analogue 3a′ is further confirmed by X-ray diffraction analysis. The added o-cresol part comes from compounds 1, instead of aldehyde which is confirmed by the cross-coupling reactions of 2 and 1 using mass spectrometry. For compariso...

Complexation of 2,7-bis(2-pyridyl)-1,8-naphthyridine (bpnp) with Cu2O in formic acid under aerobic conditions provided a dicopper complex [Cu2(bpnp)(μ-OH)(HCOO)3] (1). This complex has been characterized by X-ray crystallographic and spectroscopic analysis. With O2 as the oxidant, complex 1 is an efficient catalyst for the oxidative coupling of alcohols with amines or diamines, leading to the corresponding imines or diimines in good to excellent yields.

Reaction of the bis-aminophosphinimine [m-C6H4(HNCH2CH2N═PPh3)] with W(CO)6 afforded [m-C6H4{(CNCH2CH2NH)W(CO)5}2] (2), which underwent N-alkylation with benzyl bromide to yield [m-C6H4{(CNCH2CH2NCH2Ph)W(CO)5}2] (3). A carbene transfer reaction from W(0) to Ir(I) proceeded smoothly via the reaction of 3 with [Ir(COD)Cl]2 under mild conditions to give the diiridium(I) carbene complex [m-C6H4{(CNCH2CH2NH)Ir(CO)2Cl}2] (4). Ligand substitution of 4 with an excess of PPh3 produced the phosphine complex 5. All complexes have been characterized by spectroscopic and elemental analyses. Complexes 2 and 5 were further confirmed by X-ray diffraction studies. Complex 4 is an efficient catalyst for the reductive N,N′-dialkylation of phenylenediamines with alcohols. The mechanistic pathway of the catalysis involving the possible synergistic effect between two metal centers is discussed.

In an investigation into the chemical reactions of N-propargyl pyrroles 1 a-c, containing aldehyde, keto, and ester groups on the pyrrole ring, with [Ru]-Cl ([Ru]=Cp(PPh3 )2 Ru; Cp=C5 H5 ), an aldehyde group in the pyrrole ring is found to play a crucial role in stimulating the cyclization reaction. The reaction of 1 a, containing an aldehyde group, with [Ru]-Cl in the presence of NH4 PF6 yields the vinylidene complex 2 a, which further reacts with allyl amine to give the carbene complex 6 a with a pyrrolizine group. However, if 1 a is first reacted with allyl amine to yield the iminenyne 8 a, then the reaction of 8 a with [Ru]-Cl in the presence of NH4 PF6 yields the ruthenium complex 9 a, containing a cationic pyrrolopyrazinium group, which has been fully characterized by XRD analysis. These results can be adequately explained by coordination of the triple bond of the propargyl group to the ruthenium metal center first, followed by two processes, that is, formation of a vinylidene intermediate or direct nucleophilic attack. Additionally, the deprotonation of 2 a by R4 NOH yields the neutral acetylide complex 3 a. In the presence of NH4 PF6 , the attempted alkylation of 3 a resulted in the formation the Fischer-type amino-carbene complex 5 a as a result of the presence of NH3, which served as a nucleophile. With KPF6, the alkylation of 3 a with ethyl and benzyl bromoacetates afforded the disubstituted vinylidene complexes 10 a and 11 a, containing ester groups, which underwent deprotonation reactions to give the furyl complexes 12 a and 13 a, respectively. For 13 a, containing an O-benzyl group, subsequent 1,3-migration of the benzyl group was observed to yield product 14 a with a lactone unit. Similar reactivity was not observed for the corresponding N-propargyl pyrroles 1 b and 1 c, which contained keto and ester groups, respectively, on the pyrrole ring.

The coordination chemistry of RuII ions with [2-(diphenylphosphanyl)-N-(o-hydroxybenzylidene)]aniline (PNO-H) and the methylated analogue PNO-Me have been studied. Thus, [(PNO)RuCl(dmso)2] (1), [(PNO)2Ru] (2), [(PNO)RuCl(PPh3)] (3) and [(PNO)RuCl(CO)2] (4) were synthesized by reactions of various RuII precursors with PNO-H. Treatment of PNO-Me with [RuCl2(dmso)4] resulted in in the formation of [P,N-(PNO-Me)Ru(dmso)2Cl2] (5). However, complexation of PNO-Me with [RuCl2(CO)3(THF)] (THF = tetrahydrofuran) provided a mixture of [P,N-(PNO-Me)Ru(CO)2Cl2] (6) and 4 because O-demethylation took place during the reaction. All of the RuII complexes have been characterized by elemental analysis and spectroscopic techniques, as well as X-ray crystal structural analysis for 2, 4 and 6. The ruthenium complexes investigated in this work, except 2, are good precatalysts for the reductive amination of amine with alcohols, and 4 appears to be the best. Moreover, 4 can catalyze the direct amination of nitrobenzene with benzyl alcohol to the corresponding secondary amine.

The reaction of [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) with o-ethynyl-substituted methyl benzoate, followed by a sequential deprotonation and electrophilic alkylation reactions by further reacting with base and various alkyl haloacetates, respectively, generated several disubstituted ruthenium vinylidene complexes. In the deprotonation reactions of these disubstituted vinylidene complexes containing two ester groups, tandem cyclizations of the ligand is accompanied with a methanol elimination to generate a new organometallic product containing a three-ring indenofuranone ligand, which structure has been confirmed by a single-crystal X-ray diffraction analysis. Facile protonation and methylation are observed in these indenofuranone complexes. Additionally, for the simple furyl complex containing an O-benzyl group, a 1,3-migration of the benzyl group is observed to yield a lactone product and a Claisen rearrangement is also observed in analogous complexes with O-allyl or O-propargyl groups.

Reaction of the ruthenium allenylidene complex [Ru]═C═C═CPh2 (1, [Ru] = Cp(PPh3)2Ru) with the propargylic Grignard reagent R-C≡CCH2MgBr (R = CH3, CH2CH3, Ph) yielded a mixture of two acetylide comp...

The cyclization reaction of several diallyl aromatic amine molecules, each containing an ethynyl group at the ortho position of the aromatic ring, is accompanied by an aza-Claisen rearrangement, causing an allyl group migration to give substituted indole compounds. This cyclization is catalyzed by ruthenium triphenylphosphine and diphenylphosphinoethane (dppe) complexes as well as gold complexes with silver reagent. The less sterically crowded dppe complex is a more efficient catalyst. The mechanism involving a vinylidene intermediate is proposed on the basis of isolation of several intermediates in the ruthenium-catalyzed system. Single crystals of a metal complex with the cyclized ligand were obtained, and the structure was determined by an X-ray diffraction analysis.

A formal intramolecular olefin metathesis process between the C═C double bond of a vinylidene ligand and a pendant vinyl group in several ruthenium complexes, each with a ferrocenyl group, is followed by an additional intramolecular C−C bond formation between a Cp ligand of the ferrocenyl substituent and the vinylidene ligand. The regioselectivity of the C−C bond formation reaction at either the substituted or the nonsubstituted Cp group of the ferrocenyl group is possibly influenced by a steric effect between the neighboring substituent near the ferrocenyl group and the phosphine ligand on the ruthenium metal center. The structure of one ruthenium complex resulting from such a C−C bond formation has been fully characterized by a single-crystal X-ray diffraction analysis.

Reactions of the four 1,6-diynes 1−3 and 7, each with one terminal propargylic alcohol and one internal triple bond containing Me3Si groups, with [Ru]−Cl ([Ru] = Cp(PPh3)2Ru) led to two types of products. In the first type, only the propargylic group is involved in the reaction leading to vinylidene, allenylidene, or acetylide complexes. A C−C bond formation of two triple bonds in 1,6-diynes gave allylcarbene products of the second type. The reaction of 1 with [Ru]−Cl yielded only the first type, giving a mixture of two cationic complexes; the allenylidene complex 8 and the phosphonium acetylide complex 9, the latter resulting from further addition of a phosphine molecule to Cγ of 8. The same reaction in the presence of excess phosphine gave 9 only. However, with an additional methyl group, the 1,6-diyne 2 reacted with [Ru]−Cl to give the allylcarbene complex 11 also with a phosphonium group on the ligand. The reaction proceeds by a cyclization reaction involving two triple bonds on the metal accompanied ...

Iridium complexes [(CO)(2)Ir(NHC-R)Cl] (R = Et-, 3a; PhCH2-, 3b; CH3OCH2CH2-, 3c; o-CH3OC6H4CH2-, 3d; NHC: N-heterocyclic carbene) are prepared via the carbene transfer from [(NHC-R)W(CO)(5)] to [Ir(COD)Cl](2). By using substitution with (CO)-C-13, we are able to estimate the activation energy (Delta G double dagger) of the CO-exchange in 3a-d, which are in the range of 12-13 kcal mol(-1), significantly higher than those for the phosphine analog [(CO)(2)Ir(PCy3)Cl]. Reactions of 3b and 3d with an equimolar amount of PPh3 result in the formation of the corresponding [(NHC-R)Ir(CO)(PPh3)Cl] with the phosphine and NHC in trans arrangement. In contrast, the analogous reaction of 3a or 3c with phosphine undergoes substitution followed by the anion metathesis to yield the corresponding di-substituted [(NHC-R)Ir(CO)(PPh3)(2)]BF4 (5) directly. Treatment of 3b or 3d with excess of PPh3 leads to the similar product of disubstitution 5b and 5d. The analysis for the IR data of carbonyliridium complexes provides the estimation of electron-donating power of NHCs versus phosphines. The NHC moiety on the iridium center cannot be replaced by phosphines, even 1,2-bis(diphenylphohino)ethane (dppe). All the carbene moieties on the iridium complexes are inert toward sulfur treatment, indicating a strong interaction between NHC and the iridium centers. Complexes 3a-c are active on the catalysis of the oxidative cyclization of 2-(o-aminophenyl)ethanol to yield the indole compound. The phosphine substituted complexes or analogs are less active.

Both saturated and unsaturated N-benzyl substituted heterocyclic carbene (NHC) iridum(i) complexes were synthesized. The unsaturated carbene complex [(un-NHC-Bn)Ir(CO)(2)Cl] in the cis form was prepared via the carbene transfer from the corresponding silver complex to [Ir(COD)(2)Cl](2) followed by ligand substitution with CO, whereas the saturated complex was obtained via the transfer from (sat-NHC-Bn)W(CO)(5). The treatment of phosphines with (NHC)Ir(CO)(2)Cl complexes yielded the products with the phosphine ligand trans to the carbene moiety via substitution. X-Ray structural determination shows that distances of Ir-C((carbene)) in both (un-NHC-Bn)Ir(CO)(PR(3))Cl and (un-NHC-Bn)Ir(CO)(PR(3))Cl are essentially the same. Analyses of spectroscopic and crystal structural data of iridium complexes [(NHC)Ir(CO)(PR(3))Cl] and Vaska's complex show similar corresponding data in both types of complexes, suggesting that the studied NHC ligands and phosphines have similar bonding with Ir(i) metal center. All iridium complexes studied in this work illustrated their catalytically activity on N-alkylation of amine with alcohol via hydrogen transfer reduction. It appears no dramatic difference on the catalytic activity among these iridium carbene complexes; but the saturated carbene complex (sat-NHC-Bn)Ir(CO)(PR(3))Cl appears to be slightly more active. For example, the reaction of benzyl alcohol with aniline in the presence of catalyst (1 mol%) under basic conditions at 100 degrees C provided the secondary amine (N-benzylaniline) in 96% yield.

Reaction of o-(diphenylphosphino)(N-benzylidene)aniline (P∼N) with [Ir(COD)Cl]2 affords the substitution product [(P∼N)Ir(COD)Cl] (1). Treatment of 1 with AgBF4 yields the cyclometalated iridium hydride complex [P,N,C-(P∼N)Ir(COD)H]BF4 (2). On the other hand, under atmospheric pressure of CO, carrying out the substitution of [Ir(COD)Cl]2 with P∼N results in the formation of [P,N,C-(P∼N)Ir(CO)HCl] (5). Conversion of 4 into 5 can be achieved by the reaction of 4 with CO in the presence of tetraethylammonium chloride. Both 4 and 5 are characterized by spectroscopic and X-ray structural analyses. All iridium complexes are not good catalysts for hydroamination. However, the combination of 5 with NaB[3,5-C6H3(CF3)2]4 (denoted as NaBArF4) provides a potent catalytic system for both intra- and intermolecular hydroamination of alkynes. Intramolecular reaction of o-(2-phenylethynyl)anilines produces the corresponding indoles in good yields. Furthermore, intermolecular hydroamination takes place smoothly to generate...

Pyrazole-1-carboxamidine and formamidinesulfinic acid do not react because of the decomposition of the substrates under this conditions.

Coordination chemistry of a new pyridine imidazole-2-ylidene ligand (pyN∧C) system with sterically hindered substituents toward rhodium(I) metal ions has been investigated. The rhodium complex [(pyN∧C)RhCl(COD)] (COD = 1,5-cyclooctadiene) was prepared via the transmetallation from the silver complex [(C-pyN∧C)2Ag]AgI2. Upon the abstraction of chloride, the pyridinyl nitrogen coordinated to the metal center and formed [(C,N-pyN∧C)Rh(COD)]BF4 with the chelation of pyN∧C. The pyridinyl nitrogen donor was found to be labile and could be replaced by various donors such as phosphine, azide and halides. Substitution of COD by various donors does not proceed except strong π-acid ligands such as CO and P(OCH3)3. However, the chelation of pyN∧C was replaced by the bisphosphine (P∼P) to form [(P∼P)2Rh]BF4, which was subsequently oxidized to yield [(P∼P)2Rh(O2)]BF4.

Coordination of a chiral arsine–oxazoline ligand ( As – N ) toward (COD)PdCl 2 and (COD)PdMeCl leading to ( As – N )PdCl 2 ( 3 ) and ( As – N )PdMeCl ( 4 ) were reported. Both 3 and 4 were characterized by spectroscopic and X-ray single crystal diffraction methods. Treatment of 4 with AgBF 4 in the presence of acetonitrile resulted in the formation of [( As – N )PdMe(CH 3 CN)]BF 4 ( 6 ). Complex 6 catalyzed the copolymerization of CO and olefin, but in low conversions. In fact, the palladium black and [( As – N ) 2 Pd](BF 4 ) 2 ( 7 ) were formed from the copolymerization processes, which may explain the lower catalytic activity of 6 . Crystal structure of 7 was also determined.

Formation of mono- and dinuclear complexes containing ligands stemmed from the condensation of 2,6-diformyl-4-methylphenol derivatives with 2-(diphenylphosphino)aniline (P∼N) was investigated. Condensation of P∼N with 2,6-diformyl-4-methylanisole yielded the desired bis(imine-phosphine) L3, but provided the cyclized benzoazaphospholium compound with 2,6-diformyl-4-methylphenol. Complexation of L3 with (COD)PdCl2 gave the dinuclear complex 4. On the other hand, L3 underwent the intramolecular cyclization in the presence of (DME)NiCl2 via the formation of benzoazaphospholium rings. Template condensation of 2,6-diformyl-4-methylphenol with P∼N in the presence of metal ions yielded the mononuclear nickel(II) and palladium(II) complexes, respectively.

Dinuclear ruthenium cyclopropenyl complexes ([Ru] = (η5-C5H5)(PPh3)2Ru, R = CN, 3a; R = CH2CH2, 3b; R = Ph, 3c) are prepared by deprotonation of corresponding vinylidene complexes {[Ru]CC(CH2R)}2C6H42+ (2). For the vinylidene complex 2d (R = CO2Me) with an ester group, the deprotonation reaction leads to formation of the dinuclear bis-furyl complex (5d). Electrophilic addition of TCNQ to both three-membered rings of 3a yields the zwitterionic bis-vinylidene complex {[Ru]CC[CH(TCNQ)CN]}2C6H4 (4a), which, in the presence of MeOH/n-Bu4NOH, gives the methoxy-substituted bis-cyclopropenyl complex (6a). The proton-induced demethoxylation of 6a generates (7a). The reaction of TMSN3 with 3a gives the bis-tetrazolate complex {[Ru](N4C)CH(CH2CN)}2C6H4 (8a). Trinuclear tris-cyclopropenyl complexes (R = CN, 11a; R = CH2CH2, 11b; R = Ph, 11c) are obtained from deprotonation of {1,3,5-{[Ru]CC(CH2R)C6H4C⋮C}3C6H3}3+ (10). Complex 2b is characterized by X-ray diffraction analysis, and other complexes are characterized by ...

Both deuterium-labeled experimental and NMR spectroscopic analyses of poly(vinyl ether) offer the mechanistic insight into the polymerization, indicating that the cationic palladium aqua imine−phosphine complexes [(P∼N)PdMe(H2O)]BF4 (P∼N = o-C6H4(PPh2)(NCHAr)) promote the reaction via proton-transfer initiation. Insertion of vinyl ether into the Pd−Me bond in [(P∼N)PdMe(H2O)]BF4 does not proceed, but the single insertion of the same substrate into the Pd−acetal bond of [(P∼N)PdCOCH3(L)]BF4 provides the stable inserted product [(P∼N)PdCH(OEt)CH2COCH3]BF4, which has been characterized by an X-ray structural determination. However, these palladium complexes do not catalyze the polymerization or copolymerization of vinyl ether and carbon monoxide.

On treatment with SmI2 in THF, 1-ferrocenyl-3-phenyl-2-propen-1-one and its related ferrocene-substituted enones underwent cyclodimerizations to give aldols (2a–g) with 3,4-trans configuration. Further reduction by using increased amounts of SmI2 produced the corresponding diols. The stereoselectivity in this study was comparable with that in the SmI2-promoted cyclodimerization of chalcones, but in contrast to that in the SmI2-promoted cyclization-aldol reaction of 1,1’-dicinnamoylferrocenes. The thienyl- and furyl-substituted enones 5a and 5b could be visualized as an extended system of conjugated ketones, so that the SmI2-mediated coupling reactions occurred preferably by linkages of β-carbons with thiophene or furan rings, giving compounds 8a,b and 9a,b.

Substitution of silver complex of 2-chloro-7-(mesitylimidazolylidenylmethyl)naphthyridine (NpNHC) with palladium(II), rhodium(I) and iridium(I) metal precursors provided [Pd(C,N-NpNHC)(η3-allyl)](BF4) (5), RhCl(COD)(C-NpNHC) (6a) and IrCl(COD)(C-NpNHC) (6b), respectively. Abstraction of chloride from 6a and 6b with AgBF4 provided the chelation complexes [Rh(COD)(C,N-NpNHC)](BF4) (7a) and Ir(COD)(C,N-NpNHC)(BF4) (7b), respectively. All complexes were characterized using NMR and elemental analyses and the structural details of 5 and 6a were further confirmed using X-ray crystallography. In catalytic activity studies, complex 5 was found to be an effective catalyst in the hydrogen-transfer reduction of α,β-unsaturated carbonyl compounds into the corresponding saturated carbonyl compounds.

Treatment of [Cp(dppe)(CO)MoCC(Ph)CH2CHCH2]I (2) with MeONa caused nucleophilic attack to occur at the terminal CO ligand. This is followed by a coupling reaction of the resulting carbomethoxy group with Cα of the vinylidene ligand accompanied with coordination of the terminal olefin to afford Cp(dppe)MoC(COOMe)C(Ph)CH2CHCH2 (5). Similar coupling was observed when [Cp(dppe)(CO)MoCC(Ph)CH2Ph]I (3) was treated with MeONa, but the reaction afforded the neutral allylic complex Cp(dppe)Mo[CH(COOMe)C(Ph)CHPh] (6). The structures of complexes 5 and 6 have been determined by X-ray diffraction analysis.

The aryl propargylic alcohol 1-[2-(thiophen-3-yl)phenyl]prop-2-yn-1-ol (1a) is readily prepared from 2-(thiophen-3-yl)benzaldehyde. In the presence of visible light, treatment of 1a with one-half mole equivalent of [Ru]Cl ([Ru]Cp(dppe)Ru) (dppe=1,2-bis(diphenylphosphino)ethane) and NH4PF6 in O2 affords the naphtha[2,1-b]thiophene-4-carbaldehyde (4a) in high yields. The cyclization reaction of 1a proceeds through the formation of the carbene complex 2a that contains the naphtha[2,1-b]thiophene ring, which is isolated in a 1:1 stoichiometric reaction. The CC bond formation between the inner carbon of the terminal triple bond and the heterocyclic ring is confirmed by structure determination of 2a using single-crystal X-ray diffraction analysis. Facile oxygenation of 2a by O2 yields the aldehyde product 4a accompanied by the formation of phosphine oxide of dppe. Oxygen is most likely activated by coordination to the ruthenium center when one PPh2 unit of the dppe ligand dissociates. This dissociated PPh2 unit then reacts with the coordinated oxygen nearby to generate half-oxidized dppe ligand and an unobserved oxo–carbene intermediate. Coupling of the oxo/carbene ligands followed by demetalation then yields 4a. Presumably the resulting complex with the half-oxidized dppe ligand continuously promotes cyclization/oxygenation of 1a to yield the second aldehyde molecule. In alcohol such as MeOH or EtOH, the oxygenation reaction affords a mixture of 4a and the corresponding esters 5a or 5a'. Four other aryl propargylic alcohols 1b, 1c, 1d, 1e, which contain thiophen-2-yl, isopropenyl, fur-3-yl, and fur-2-yl, respectively, on the aryl ring are also prepared. Analogous aldehydes 4b, 4c, 4d, 4e are similarly prepared from 1b, 1c, 1d, 1e, respectively. For oxygenations of 1b, 1d, and 1e in alcohol, mixtures of aldehyde 4, ester 5, and acetal 8 are obtained. The carbene complex 2b obtained from 1b was also characterized by single-crystal X-ray diffraction analysis. The UV/Vis spectra of 2a and 2b consist of absorption bands with a high extinction coefficient. From DFT calculations on 2a and 2b, the visible light is found to populate the LUMO antibonding orbital of mainly RuC bonds, thereby weakening the RuC bond and promoting the oxygenation/demetalation reactions of 2.

Two cyclopropyl allenylidene complexes [Ru]=C=C=C(R)(C(3)H(5)) ([Ru]=[RuCp(PPh(3))(2)], Cp=Cyclopentadienyl; R=thiophene (2a) and R=Ph (2b)) are prepared from the reactions of [Ru]Cl with the corresponding 1-cyclopropyl-2-propyn-1-ol in the presence of KPF(6). Thermal treatment, halide-anion addition, and palladium-catalyzed reactions of 2a and 2b all lead to a ring expansion of the cyclopropyl group, giving the vinylidene complexes 4a and 4b, respectively, each with a five-membered ring. This ring expansion proceeds by C-C bond formation between Cβ of the cumulative double bond and a methylene group of the cyclopropyl ring. In the reaction of 2a with pyrrole, consecutive formation of two C-C bonds, one between C-2 of pyrrole and Cγ of 2a and the other between C-3 of pyrrole and Cα, results in the formation of 6a. The reaction proceeds by addition of pyrrole and 1,3-proton shifts. The hydrogenation of 2a by NaBH(4) is carried out in different solvents. The cumulative double bonds are reduced regioselectively to give a mixture of 7a and 8a. Interestingly, use of different solvents leads to different ratios of 7a and 8a. Presence of a protic solvent like methanol in dichloromethane or chloroform solution increases the yield of 8a, thus revealing that both the rates of hydroboration and deboronation increase. The structures of two new complexes 4a and 6a have been firmly established by X-ray diffraction analysis.

The three azirinyl complexes (R = CN, CHCH2, Ph) are obtained from deprotonation of isonitrile complexes. For R = Ph, three isomers including 1H- and 2H-azirinyl complexes are observed at low tempe...

Coordination of iridium(I) metal ions with a pyridinyl imidazol-2-ylidene ligand (pyNwedgeC-R) [R=Me, mesityl(2,4,6-trimethylphenyl)] that processes bulky substituents has been investigated. The iridium carbene complexes [(C-pyNwedgeC-R)IrCl(COD)] (COD=1,5-cyclooctadiene) are prepared via transmetalation from the corresponding silver carbene complexes. Upon the abstraction of chloride, the chelation of pyNwedgeC becomes feasible, resulting in the formation of [C,N-(pyNwedgeC-R)Ir(COD)](BF4) (4). The coordinated COD of complex 4 can be replaced by carbon monoxide to yield the corresponding carbonyl species [C,N-(pyNwedgeC-R)Ir(CO)2](BF4). The labile nature of the pyridinyl nitrogen donor is readily replaced by acetonitrile, as is evidenced by the NMR study. All iridium complexes show catalytic activity on the hydrogen-transfer reduction of carbonyl and nitro functionalities. By manipulation of the reaction conditions, the iridium-catalyzed reduction of nitroarenes can selectively provide aniline or azo compounds as the desired product.

In searching for aqua sodium species acting as Bronsted acids in catalysis, we explored the phenomenon that sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate dihydrate (NaBAr(F)4.2H2O) evidently provides one proton source to initiate the polymerization of vinyl ethers in anhydrous dichloromethane solutions. In addition, NaBAr(F)4 catalyzed efficiently in the polymerization of activated styrenes, such as p-methoxystyrene.

Five X-ray crystallographic structures of bianthronyl (1, 2b-5b) revealed the presence of long central C(sp3)-C(sp3) bonds (or =1.60 A) and mostly gauche conformation. DFT calculations were carried out to study the structural features of bianthronyl and related model molecules [corrected]. Our B3LYP/6-31G gas-phase calculation results suggest that steric effect plays a role in causing the long C-C sigma bond length (1.60 A), nonplanarity of the anthracenone moiety (20 degrees ), and preferred gauche conformation. However, when the gauche preference is weak, environmental effects such as solvation and packing forces can reverse it. As the degree of nonplanarity of the anthracenone moiety is consistently larger in the anti conformation than in the gauche and the ease of achieving nonplanarity is determined by flexibility of the central six-membered rings directly connected to the C(sp3)-C(sp3) bond, one way to control the structure and anti-gauche energy difference of closely related compounds is by changing the clamping group (Z) in the central six-membered ring.