L. James Wright

Functionalization of metallabenzenes through nucleophilic aromatic substitution of hydrogen.

The cationic metallabenzenes [Ir(C(5)H(4){SMe-1})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (1) and [Os(C(5)H(4){SMe-1})(CO)(2)(PPh(3))(2)][CF(3)SO(3)] (2) undergo regioselective nucleophilic aromatic substitution of hydrogen at the metallabenzene ring position γ to the metal in a two-step process that first involves treatment with appropriate nucleophiles and then oxidation. Thus, reaction between compound 1 and NaBH(4), MeLi, or NaOEt gives the corresponding neutral iridacyclohexa-1,4-diene complexes Ir(C(5)H(3){SMe-1}{H-3}{Nu-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2) (Nu = H (3), Me (4), OEt (5)). Similarly, reaction between 2 and NaBH(4) or MeLi gives the corresponding osmacyclohexa-1,4-diene complexes Os(C(5)H(3){SMe-1}{H-3}{Nu-3})(CO)(2)(PPh(3))(2) (Nu = H (8), Me (9)). The metallacyclohexa-1,4-diene rings in all these compounds are rearomatized on treatment with the oxidizing agent O(2), CuCl(2), or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Accordingly, the cationic metallabenzene 1 or 2 is returned after reaction between 3 and DDQ/NEt(4)PF(6) or between 8 and DDQ/NaO(3)SCF(3), respectively. The substituted cationic iridabenzene [Ir(C(5)H(3){SMe-1}{Me-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (6) or [Ir(C(5)H(4){SMe-1}{OEt-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (7) is produced in a similar manner through reaction between 4 or 5, respectively, and DDQ/NEt(4)PF(6), and the substituted cationic osmabenzene [Os(C(5)H(3){SMe-1}{Me-3})(CO)(2)(PPh(3))(2)]Cl (10) is formed in good yield on treatment of 9 with CuCl(2). The starting cationic iridabenzene 1 is conveniently prepared by treatment of the neutral iridabenzene Ir(C(5)H(4){SMe-1})Cl(2)(PPh(3))(2) with NaS(2)CNEt(2) and NEt(4)PF(6), and the related starting cationic osmabenzene 2 is obtained by treatment of Os(C(5)H(4){S-1})(CO)(PPh(3))(2) with CF(3)SO(3)CH(3) and CO. The stepwise transformations of 1 into 6 or 7 as well as 2 into 10 provide the first examples in metallabenzene chemistry of regioselective nucleophilic aromatic substitutions of hydrogen by external nucleophiles. DFT calculations have been used to rationalize the preferred sites for nucleophilic attack at the metallabenzene rings of 1 and 2. The crystal structures of 1, 3, 6, and 7 have been obtained.

Design and synthesis of copper complexes of novel ligands based on the pyridine thiolate group

The versatile coordination properties of 2,2′-dipyridyldisulfide (dpds) enables a series of different copper complexes to be isolated in good yield, including [CuCl2(μ-dpds)] (1) which has a one-dimensional helical structure and [Cu(μ-Cl)(μ-dpds)] (4) which has a two-dimensional sheet structure. Flexible movement of the disulfide group in the dpds ligand facilitates the formation of complexes with a diverse range of structures. Compound 1 transforms into 4 almost quantitatively on standing in contact with methanol. After prolonged standing 4 slowly converts to the stable, betain-containing product, [Cu(μ-1-(2-pyridine)pyridiniumthiolato)(μ-Cl)] (8) with the concomitant production of elemental sulfur. The bromide congener of 4 undergoes the same transformation. The free ligand, 1-(2-pyridine)pyridiniumthiolate, can be released from 8 by treatment with CN−. On treatment of bis(2-pyridylthio)methane (BPTM) with CuCl2 [CuCl2(BPTM)]n (9) is formed. This complex has an infinite helical chain structure. Reaction between tris(2-pyridylthio)methane (TPTMH) and CuBr gave [CuBr(TPTM)] (12) and with [Cu(NCCH3)4]PF6 in the presence of oxygen, the complex [Cu(CH3CN)(TPTM)]PF6 (14) is formed. Complex 14 is the first structurally characterised example of a complex containing a Cu(II)–C(sp3) bond.

Reaction between the thiocarbonyl complex, Os(CS)(CO)(PPh3)3, and propyne: crystal structure of a new sulfur-substituted osmabenzene

Abstract Reaction between Os(CS)(CO)(PPh 3 ) 3 and propyne gives a complex mixture of products from which can be isolated the simple oxidative addition product Os(CCMe)H(CS)(CO)(PPh 3 ) 2 ( 1 ) and the osmabenzene Os(η 2 -C[S]CMeCHCHC Me)(CO)(PPh 3 ) 2 ( 2 ), where the two propyne molecules in the osmabenzene ring have linked tail-to-tail. Treatment of 1 with HCl gives, as the ultimate product, the propenylthioacyl complex, Os(η 2 -C[S]CHCHMe)Cl(CO)(PPh 3 ) 2 ( 3 ). The crystal structures of compounds 1 – 3 have been determined.

Bromination and nitration reactions of metallated (Ru and Os) multiaromatic ligands and crystal structures of selected products

Abstract Three nitrogen-containing aromatic heterocycles, 2-(1′-naphthyl)pyridine, 2-phenylquinoline, and 2,3-diphenylquinoxaline, have been mercurated in the naphthyl or phenyl ring 2-position and then symmetrised to form the mercury compounds Ar2Hg (Ar=Nppy (3), Phqn (1) or Dpqx (5), respectively). These reagents are suitable for trans-metallation and reaction with MHCl(CO)(PPh3)3 affords the complexes M(η2-C,NAr)Cl(CO)(PPh3)2, (6, M=Ru, Ar=Nppy; 7, M=Os, Ar=Nppy; 8, M=Ru, Ar=Phqn; 9, M=Os, Ar=Phqn; 10, M=Ru, Ar=Dpqx; 11, M=Os, Ar=Dpqx) in which each product features an aryl ligand that forms a strongly chelated five-membered ring through coordination of the heterocyclic N atom. The chloride ligand in each of the complexes 6–11 can be replaced by dimethyl dithiocarbamate to give ultimately the mono-triphenylphosphine complexes, M(η2-Ar)(η2-S2CNMe2)(CO)(PPh3) (12, M=Ru, Ar=Nppy; 13, M=Os, Ar=Nppy; 14, M=Ru, Ar=Phqn; 15, M=Os, Ar=Phqn; 16, M=Ru, Ar=Dpqx; 17, M=Os, Ar=Dpqx). Similarly, compound 10 when treated with Na(acac) gives Ru(η2-Dpqx)(η2-acac)(CO)(PPh3) (18), while treatment with trifluoroacetic acid gives Ru(η2-Dpqx)(O2CCF3)(CO)(PPh3)2 (19). Many of these complexes were found to be very robust, making them suitable for electrophilic aromatic substitution reactions under harsh conditions. In each case, the presence of the metal had both an activating and a directing effect on the aryl ring to which it was bonded. Bromination or nitration reactions, both of which are not normally possible with organometallic substrates, were carried out successfully, giving rise to monobrominated or dinitrated products, respectively. The following compounds were characterised, M(η2-Ar-4-Br)Cl(CO)(PPh3)2 (20, M=Ru, Ar=Phqn; 21, M=Os, Ar=Phqn; 22, M=Ru, Ar=Dpqx; 24, M=Os, Ar=Dpqx), M(η2-Dpqx-4-Br)(η2-S2CNMe2)(CO)(PPh3) (23, M=Ru; 25, M=Os), Os(η2-Ar)Cl(CO)(PPh3)2 (26, Ar=Nppy-6,8-(NO2)2; 27, Ar=Phqn-4,6-(NO2)2). Crystal structures of compounds 7, 12, 15, 18, 19, 21, 23 and 25 have been determined.

Coordinatively unsaturated σ-aryl complexes of ruthenium(II) and osmium(II)

Abstract The hydrido complexes MHCl(CO)(PPh3)3 (M = Ru, Os) react with the organomercury compounds R2Hg (R = phenyl, p-tolyl, o-tolyl, trans-β-styryl) to give the five-coordinate, σ aryl and alkenyl complexes MRCl(CO)(PPh3)2 in high yield. Bromide and iodide analogues of these compounds can be prepared through reaction with silver perchlorate followed by addition of excess bromide or iodide ions. The X-ray crystal structures of two of the complexes, Ru(p-tolyl)Cl(CO)(PPh3)2 and Ru(o-tolyl)Cl(CO)(PPh3)2, have been determined.

A Metallaanthracene and Derived Metallaanthraquinone

Metalla-analogues of archetypal aromatic molecules are attracting ever increasing interest. Although metallabenzenes (which fall within this class) have been well studied, fused-ring metallabenzenes are rare and of the linear polycyclic metallaaromatic hydrocarbons, only metallanaphthalene is known. Herein we report the first metallaanthracene, [Ir(C13 H8 {CH2 CO2 Me-5})Cl(PPh3 )2 ]O3 SCF3 (5), which represents the next member of this series of polycyclic compounds. Structurally, 5 has a number of features in common with anthracene including fused-ring planarity and bond-length alternation. In analogues of classic reactions of anthracene, 5 forms a Diels-Alder adduct with maleic anhydride and on oxidation the unprecedented fused-ring metallaanthraquinone, [Ir(C15 H6 O{Br-6}{OMe-7}{=O-8}{=O-15})Br(PPh3 )2 ], is obtained.

Reactions of the dichloroboryl complex of osmium, Os(BCl2)Cl(CO)(PPh3)2, with water, alcohols, and amines: Crystal structures of Os[B(OH)2]Cl(CO)(PPh3)2, Os[B(OEt)2]Cl(CO)(PPh3)2, and Os[BN(CH3)C6H4N(CH3)]Cl(CO)(PPh3)2

Abstract Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)2, and water replaces both chloride substituents on the boryl ligand, without cleavage of the OsB bond, giving yellow Os[B(OH)2]Cl(CO)(PPh3)2 (1). Compound 1 can be regarded as an example of a ‘metalla–boronic acid’ (LnMB(OH)2) and in the solid state, X-ray crystal structure determination reveals that molecules of 1 are tetragonal pyramidal in geometry (OsB, 2.056(3) A) and are arranged in pairs, as hydrogen-bonded dimers. This same arrangement is found in the crystalline state for simple boronic acids. Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)2, and methanol and ethanol produces yellow Os[B(OMe)2]Cl(CO)(PPh3)2 (2a) and yellow Os[B(OEt)2]Cl(CO)(PPh3)2 (2b), respectively. The crystal structure of 2b reveals a tetragonal pyramidal geometry with the diethoxyboryl ligand in the apical site and with an OsB bond distance of 2.081(5) A. Reaction between Os(BCl2)Cl(CO)(PPh3)2, and N,N′-dimethyl-o-phenylenediamine and N,N′-dimethyl-ethylenediamine produces yellow Os [ BN ( CH 3 ) C 6 H 4 N ( CH 3 )] Cl ( CO )( PPh 3 ) 2 (5) and yellow Os [ BN ( CH 3 ) C 2 H 4 N ( CH 3 )] Cl ( CO )( PPh 3 ) 2 (6), respectively. Compounds 1, 2a, 2b, 5, and 6 all react with carbon monoxide to give the colourless, six-coordinate complexes Os[B(OH)2]Cl(CO)2(PPh3)2 (3), Os[B(OMe)2]Cl(CO)2(PPh3)2 (4a), Os[B(OEt)2]Cl(CO)2(PPh3)2 (4b), Os [ BN ( CH 3 ) C 6 H 4 N ( CH 3 )] Cl ( CO ) 2 ( PPh 3 ) 2 (7), and Os [ BN ( CH 3 ) C 2 H 4 N ( CH 3 )] Cl ( CO ) 2 ( PPh 3 ) 2 (8), respectively, but in the case of 6 only, this CO uptake is easily reversible. The crystal structure of 5 is also reported.

Synthesis and Structures of cis- and trans-[Os(Bcat)(aryl)(CO)2 (PPh3 )2 ]: Compounds of Relevance to the Metal-Catalyzed Hydroboration Reaction and the Metal-Mediated Borylation of Arenes.

Support for key steps of the mechanism for the transition metal catalyzed hydroboration reaction is provided by the characterization and reactions of 1, a cis-(boryl)(aryl) complex of osmium(II). This compound readily eliminates o-tolylBcat to give the osmium(0) intermediate 2, which in the presence of HBcat reestablishes the osmium-boron bond by forming 3. R=o-tolyl, H2 cat=catechol=1,2-(HO)2 C6 H4 .

Extending the range of neutral N-donor ligands available for metal catalysts: N-[1-alkylpyridin-4(1H)-ylidene]amides in palladium-catalyzed cross-coupling reactions.

N-[1-Alkylpyridin-4(1H)-ylidene]amides (PYAs) are a new class of easily prepared, neutral N-donor ligands that share some features in common with N-heterocyclic carbenes. They are strongly electron-donating toward metal centers, and a palladium(II) complex of one of these ligands has been shown to successfully catalyze both the Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions.

Direct nitration of aryl groups σ-bound to ruthenium(II)

A new method has been developed for the preparation of nitroaryl transition metal complexes using copper(II) nitrate in the presence of acetic anhydride (Menke conditions) to directly nitrate an aryl group which is already σ-bound to a transition metal centre. Under these conditions ruthenium(II) aryl complexes of the type: (where R1=R2=H; R1=H, R2=CH3; R1=CH3, R2=H) react to yield three distinct types of nitroaryl-containing products (I–III). The preparation and characterisation of these compounds are described. X-ray crystallographic data for one example of each of the three types of compound, are also reported. The compounds that have been studied crystallographically are Ru(C6H4NO2-4)(η2-O2CCH3)(CO)(PPh3)2 (1a), C45H37NO5P2Ru·(CH2Cl2)0.5, a = 20.254(5), b=19.437(8), c=22.629(3) A, β=115.390(10)°, monoclinic, space group C2/c, Z=8; Ru(C6H4N[O]O-2)- Cl(CO)(PPh3)2 (4a), C43H34ClNO3P2Ru, a=9.331(3), b=12.443(2), c=16.346(3) A, α=82.81(2), β=85.03(2), γ=74.76(2)°, triclinic, space group P1, Z=2; Ru(C6H2CH3-2,NO2-4,N[O]O-6)Cl(CO)(PPh3)2 (5b), C44H35Cl- N2O5P2Ru·(CH2Cl2)2, a=19.497(3), b=14.502(3), c=19.340(5) A, β=122.79(1)°, monoclinic, space group Cc, Z=4.