Dicarbonyl Complexes Research Articles

Schiff Base Complexes of Rhodium(I) with Tridentate N‐Methyl‐S‐methyldithiocarbazate Ligands

AbstractSchiff bases derived from the condensation of β‐diketones with N‐methyl‐S‐methyldithiocarbazates yield cis dicarbonyl complexes Rh(CO)2 (Schiff) on reaction with [Rh(μ‐Cl)(CO)2]2. Those derived from aromatic aldehydes form trans dicarbonyl complexes. These complexes with excess of triphenylphosphine give only Rh(CO)(PPh3)(Schiff). cis‐1,5‐cyclooctadiene (COD) reacts with cis dicarbonyl complexes to yield the carbonyl‐free product Rh(COD)(Schiff); similar reactions have not been observed in the case of trans‐dicarbonyl complexes. Oxidative addition of bromine to these complexes yields dibromo derivative in which the Schiff base acts as bidentate chelate. Rh(PPh3)2(Schiff) complexes have been obtained from the reaction of above Schiff bases with Rh(PPh3)3Cl. The structures of these new complexes have been determined based on IR and 1H NMR spectra.

ChemInform Abstract: Reactions of the Dicarbonyl Complex Re2Cl4(dppm)2(CO)2 with Nitriles and Isocyanides.

AbstractThe title reactions of the dicarbonyl complex (I), for which due to a disorder problem it was not possible to distinguish between a cis and trans position of the bridging and terminal carbonyl groups, generate the diamagnetic salts (II).

Reactions of the molybdenum(II) dicarbonyl complexes with mercury(II) halides and pseudohalides

The reactions of the molybdenum(II) dicarbonyl complexes, [MoBr(π-allyl)(CO) 2(L) 2] (L = CH 3CN, py) and (MoBr(π-allyl)(CO) 2(L,L)] (L,L = bipy, phen, dppe) with HgX 2 (X = Cl, CN, SCN) give several new complexes via a displacement reaction involving Br or/and L ligands or a simple adduct formation reaction.

Some Substituent Effects in the Formation of Binuclear Metalladienes and 1,2-Dimetallacycloheptadienones From Reactions Between (η-C5H5)2Rh2(μ-CO)(CF3C2CF3) and Alkynes

The reaction between (η-C5H5)2Rh2(CO)(CF3C2CF3)(1) and alkynes, RC=CR′, can proceed by two alternative pathways. One gives the complexes (η- C5H5)2Rh2{C4(CF3)2RR′CO} (2) in which a pentadienone unit bridges the Rh - Rh bond. The other produces the binuclear metalladiene complexes (η-C5H5)2Rh2{C4(CF3)2RR?} (3) plus the dicarbonyl complex (η-C5H5)2Rh2(CO)2(CF3C2CF3) (4). The formation of (2) is strongly favoured with the dialkylacetylenes BuC≡CBu and MeC =CR (R = Et, Pri, But). With the unsymmetrical acetylenes, two isomers of (2) are isolated. The tendency to form (3) + (4) increases when there are electron-withdrawing substituents such as CN on the alkyne, and becomes dominant when the alkyne is polar (e.g. MeC≡CR with R = Ph, CF3 or CO2Me). The reactions with MeC≡CR are highly regioselective, with only one of the two possible regioisomers being isolated in each case. This has the methyl group in the 3-position of the metalladiene ring. Unexpected products formed in the reactions with MeC≡Cet and MeC≡CPri have been characterized by X-ray crystallography. One is a 1,2- dimetallacycloheptadienone complex, (η-C5H5)2Rh2{C4(CF3)2Me(CMe2OH)CO}. The compound crystallizes with 16 molecules in the orthorhombic space group Fdd2 in a unit cell of dimensions a 31.728(15), b 27.923(14), c 9.275(5) Ǻ. The structure was solved by heavy atom methods and refined to R 0.037 based on 2644 observed reflections. The CMe2(OH) group is adjacent to the carbonyl in the bridging group. The other is a binuclear metalladiene complex (η-C5H5)2Rh2{C4(CF3)2Me( COMe )}. It crystallizes with eight molecules in the orthorhombic space group P bca in a unit cell of dimensions a 17.349(8), b 15.819(8), c 13.720(7) Ǻ. The structure was solved by heavy atom methods and refined to R 0.053 based on 3045 observed reflections above background. The acyl group is adjacent to the metal in the metalladiene ring. These two complexes are formed from (1) and impurities present in the alkynes.

Reactions of the dicarbonyl complex Re2Cl4(dppm)2(CO)2 with nitriles and isocyanides. Synthesis of [Re2Cl3(dppm)2(CO)2L]n+ (n = 0, 1; L = RCN, RNC) and the structural characterization of [Re2Cl3(dppm)2(CO)2(NCC2H5)]PF6

Reactions of the dicarbonyl complex Re2Cl4(dppm)2(CO)2 with nitriles and isocyanides. Synthesis of [Re2Cl3(dppm)2(CO)2L]n+ (n = 0, 1; L = RCN, RNC) and the structural characterization of [Re2Cl3(dppm)2(CO)2(NCC2H5)]PF6

MICHAEL-TYPE ADDITIONS TO α,β-ENOYLIRON(CYCLOPENTADIENYL)DICARBONYL COMPLEXES AND ITS APPLICATION TO β-LACTAM SYNTHESIS

Abstract Michael-type additions of amines and thiols to α,β-enoyliron(cyclopentadienyl)dicarbonyl complexes were carried out to give the corresponding new β-aminoalkanoyl- and β-thioalkanoyliron complexes in good to excellent yields. A β-aminoalkanoyliron complex was treated with bromine in the presence of triethylamine to give the expected β-lactam in an excellent yield.

Ansa-Metallocene derivatives : IX. Electrochemical reactions of tetramethylethylene-bridged titanocene dichloride and dicarbonyl derivatives

In the reduction of tetramethylethylene-bridged (CH 13) 4C 2(C 5H 4) 2TiCl 2 under argon, studied by cyclic voltammetry, a first reduction to the Ti III stage occurs at a potential of −0.92 V vs. SCE, close to that of (C 5H 5) 2TiCl 2, and a second reduction to the Ti II stage at a potential of −2.53 V, about 0.3 V more negative than in the corresponding reduction of the unbridged analogue. Decay of the tetramethylethylene-bridged Ti II product is considerably faster than that of its unbridged analogue. Changes induced by the presence of an N 2 or H 2 atmosphere indicate the occurrence of secondary reactions. In the presence of CO, reduction to (CH 3) 4C 2(C 5H 4) 2Ti(CO) 2 occurs at −2.0 V. This tetramethylethylene-bridged titanocene dicarbonyl complex, which is also formed by reduction of (CH 3) 4C 2(C 5H 4) 2TiCl 2 with Mg metal under CO, undergoes irreversible reduction and oxidation at −2.78 and −0.08 V, respectively. When the latter process is conducted in the presence of Cl −, the dichloride (CH 3) 4C 2(C 5H 4) 2TiCl 2 is regenerated.

Reactions of tricarbonylphosphine complexes (bipy)P(4- XC 6H 4) 3Mo(CO) 3 (X = Cl, F, Me, MeO) with tin(IV) derivatives R nSnCl 4- n( n = 0,1,3)

The reactions of the tricarbonylphosphine complexes (bipy)(P)Mo(CO) 3 (bipy = 2,2′-bipyridine (P)=P(4-ClC 6H 4) 3, P(4-FC 6H 4 3, P(4-FC 6H 4) 3 and P(4- CH 3OC 6H 4) 3) with SnCl 4 yield new seven-coordinate compounds of the type (bipy)P(4-XC 6H 4) 3(CO) 2Mo(Cl)(SnCl 3) X = F, Cl, CH 3). When X = MeO the complex (bipy)(CO) 3Mo(Cl)(SnCl 3 is obtained. The halides CH 3SnCl 3 and C 6H 5SnCl 3 enter into similar reactions to give new dicarbonyl complexes (bipy)- P(4-XC 6H 4) 3(CO) 2Mo(Cl)(SnRCl 2) and tricarbonyl complexes (bipy)- (CO) 3Mo(Cl)(SnRCl 2) (R = CH 3, C 6H 5).

Five-coordinate dicarbonyl complexes of rhodium(I): [RhX(CO)2(PPh3)2] (X = Cl, Br, I)

The complexes trans-[RhX(CO)PPh3)2] (1, X = Cl, Br, I) react with CO to form [RhX(CO)2(PPh3)2] (2), and not to form cis-[RhX(CO)(PPh3)2]. Complexes 2 contain equivalent axial carbonyl ligands. It is proposed that a series of dicarbonyl complexes, including 2, is formed during decarbonylation reactions catalyzed by 1.

Stannanedithiocarboxylates: novel α-functional organotin ligands

In spite of the high nucleophilicity of organotin anions, their addition to heteroallenes to form a stable SnC bond is restricted to carbon disulfide. The resulting stannanedithiocarboxylates R 3SnCS 2 − have been alkylated to give the dithioesters R 3SnCS 3R′ as the first α-thiocarbonyltin compounds. The synthesis of transition metal complexes such as R 3SnCS 2M(CO) 4 (M = Mn, Re) requires the isolation of the dioxane adducts R 3SnCS 2M′ · nC 4H 8O 2 (M′ = Li, Na, K). The thermal substitution of the chelate complexes by σ-donor ligands of Main Group V elements proceeds stereospecifically with the formation of fac tricarbonylmetal compounds. Photolytic activation leads to disubstitution in most cases; only with tricyclohexylphosphine is the mer-isomer obtained as the kinetic product. The trans-disubstituted dicarbonyl complexes tend to revert to the monosubstituted species, and the recombination has been followed by IR and UV spectroscopy. The controlled synthesis of monocoordinate stannanedithiocarboxylato complexes has been achieved by substitution of the CO group with bidentate donor ligands. All the stannanedithiocarboxylates show an unexpected diamagnetic shift of the tin-119 NMR signals, which span the range from δ −120 to −260 ppm (relative to Me 4Sn) and are among the highest shieldings observed for tetraorganotin compounds.

The reactions of carbon monoxide with series of dirhenium species [Re 2Cl 4(PMe 2Ph) 4] n+ (n = 0, 1, 2) possessing rhenium—rhenium bond orders of 4, 3.5 and 3

The complexes [Re 2Cl 4(PMe 2Ph) 4](PF 6), n, where n = 1, 1 or 5, which possess ReRe multiple bonds of orders 3, 3.5 and 4, respectively, react with carbon monoxide in 2-methoxyethanol to afford the reductive cleavage product ReCl(CO) 3(PMe 2Ph) 2 in high yield. In other solvents (ethanol and toluene), these reactions are complicated by competing side reactions which can result in redox chemistry at the dirhenium units without the incoporation of CO into the products. The reactions in ethanol and toluene lead to the formation of Re 2Cl 5(PMe 2Ph) 3, Re 2Cl 6(PMe 2Ph) 2, trans-ReCl 4(PMe 2Ph) 2, ReCl(CO) 2(PMe 2Ph) 3 and/or ReCl 3(CO)(PMe 2Ph) 3, in addition to ReCl(CO) 3(PMe 2Ph) 2, depending upon the reaction conditions. The electrochemical properties of the carbonyl containing prosducts ReCl(CO) 2(PMe 2Ph) 3, ReCl(CO) 3(PMe 2Ph) 2 and ReCl 3(CO) 2(PMe 2Ph) 3, as well as those of the previuosly described rhenium(II) dicarbonyl complex ReCl 2(CO) 2(P-n-Pr 3) 2, have been studied using the cyclic voltammetry technique.

Infrared study of polystyrene-bound rhodium under hydroformylation conditions

The spectra of [RhH(CO)(PPh 3) 3] bound to phosphinated gel-form polystyrene-divinylbenzene beads were recorded at ambient temperature and 18 atm total pressure. Hydrogen and carbon monoxide saturation partial pressures were varied. The resulting spectra are interpreted by comparison with published homogeneous spectra. Two predominant species were observed at 0.67 CO/H 2, a bis(phosphine)dicarbonyl complex and a dimer. The relative amounts of each were affected by the CO/H 2 ratio. An absorbance band characteristic of aldehydes was used to establish hydroformylation activity.

ChemInform Abstract: SYNTHESIS OF 5‐AMINO‐4‐CYANOPYRAZOLE FROM 1,1‐DICYANOALKENES AND ELEMENTAL DINITROGEN USING A TUNGSTEN COMPLEX

AbstractDer aus Wolframhexachlorid zugängliche Komplex (VII) ergibt bei der elektrochemischen Reduktion das Amino‐cyano‐pyrazol (VIII).

Ionic hydrogenation of acetylene- and allenearenechromium-dicarbonyl complexes

1. The ionic hydrogenation of chelated acetylene- and allenearenechromium dicarbonyl complexes under mild conditions proceeds with a conversion of the acetylenic and allenic ligands to the olefinic ligand. 2. The protonation of a mixture of isomeric allenearenechromium, dicarbonyl complexes leads to the formation of the previously unknown chelated cationic allylarenechromium dicarbonyl complex.

Electric field gradient at iron in dicarbonyl complexes of (tetraphenylporphyrinato)- and (octamethyltetrabenzoporphyrinato)iron(II)

Electric field gradient at iron in dicarbonyl complexes of (tetraphenylporphyrinato)- and (octamethyltetrabenzoporphyrinato)iron(II)

Synthesis of 5-amino-4-cyanopyrazole from 1,1-dicyanoalkenes and elemental dinitrogen using a tungsten complex

Electrochemical reduction of the dinitrogen-derived dicyanovinly hydrazido(2–) complex [WF(dppe)2N[graphic omitted]HCCN2]+[BF4]-[dppe = bis(diphenylphosphino)ethane] in tetrahydrofuran yields 5-amino-4-cyanopyrazole in up to 50% yield; when carried out under N2, the metal-containing product of reduction is [WF(dppe)2N2H2]+[BF4]–, but under CO the dicarbonyl complex W(dppe)2(CO)2 is formed.

Neutral and cationic dicarbonyl complexes of manganese (I) with diphosphines

The reaction of BrMn(CO) 5 with dppm in refluxing toluene gives the neutral compunds cis-cis-BrMn(CO) 2(dppm) 2 which has been shown by 31P NMR spectroscopy to have one dppm monodentate and the other bidendate. This complex reacts with TIPF 6 in dichloromethane solution to give the salt cis-[Mn(CO) 2-(dppm) 2]PF 6 or, if the reaction is carried out in the presence of CO, the salt mer-[Mn(CO) 3(dppm) 2]PF 6 which also has one monodentate dppm (by 31P NMR). The cationic complex cis-[Mn(CO) 2(dppm) 2] + isomerizes to the transisomer when irradiated with UV light, while heating of the latter gives back the cis-isomer. The perchlorate salts of the cation cis-[Mn(CO) 2(dppm) 2 + can be prepared by reacting fac-O 3ClOMn(CO) 3(dppm) withdppm in refluxing toluene, and trans-[Mn(CO) 2(diphos)(diphos)′] +, diphos or diphos′ being dppm or dppe, by treating the fac-O 3ClMn(CO) 3(diphos) with dppm or dppe under UV irradiation.

Chelate cyclopentadienylmanganese dicarbonyl complexes

Cyclopentadienylmanganese tricarbonyl complexes with allyloxymethyl- and propargyloxymethyl substituents have been synthesized. Under UV irradiation, they give new chelate cyclopentadienylmanganese dicarbonyl complexes with coordinated vinyl and ethinyl groups. In the case of cyclopentadienylmanganese-cricarbonyl complexes having two such substituents, only mono-bridged chelate dicarbonyl compounds have been obtained. α-Oxo-ω-cyanoalkyl derivatives of cyclopentadienylmanganese tricarbonyl give under UV irradiation new chelate complexes with σ-coordination between the metal and the nitrogen atom of cyano groups. An attempt to obtain chelate complexes by the same method from ω-cyanoalkyl derivatives of cyclopentadienylmanganese tricarbonyl failed.

Organometallic derivatives of the transition metals : VIII. Bonding and molecular motions in silyl transition metal complexes studied by 29Si NMR

Complexes of the general type [(η 5-C 5H 5)Fe(L) 2R], L  CO, PR′ 3; R  silyl, polysilyl, and silylmethyl, have been studied using 29Si NMR. Chemical shift and nuclear Overhauser effect data have been obtained and related to the chemical bonding and molecular motion of the complexes. For the various dicarbonyl complexes sigma inductive effects by the iron substituent are noted, while upon phosphine substitution pi effects are observed with directly bonded silicon atoms present. From NOE η values segmental motion of the various chains may be noted, with the Fe iron atom effectively anchoring one end of the system.

The role of binuclear rhodium complexes as possible intermediates in the formation of cyclopentadienone-rhodium complexes. Reactions between (η-C5H5),Rh2(CO)(CF3C2CF3) and symmetrically disubstituted alkynes

A stepwise pathway for the formation of cyclopentadienone complexes (η-C5H5)Rh{C4R4CO} from (#-C5H5)Rh(CO)2 and RC≡CR has been elucidated. When solutions of (η-C5H5)Rh(CO)2 are heated, there is loss of CO and (η-C5H5),Rh2(CO)3 is formed. This reacts with alkynes to give binuclear complexes such as (η-C5H5),Rh2(CO)2(CF3C2CF3) gives (ηC5H5)2Rh2(CO)(ButC2But). Removal of CO from (η-C5H5)2Rh2(CO)2(CF3C2CF3) gives (η-C5H5)2Rh2(CO)(CF3C2CF3) and this monocarbonyl complex reacts with more alkyne, R'C≡CR', to form the bis-alkyne complex (η-C5H5)2Rh2(CO)(CF3C2CF3)(R'C2R')(R' = SiMe3) and then the pentadienone complex (η-C5H5)2Rh2{C4(CF3)2R'2CO} (R' = =Me, Me3Si, CF3). In some instances (R' = Ph, But, CO2Me), this reaction gives equimolar amounts of the metallodiene complex (η-C5H5)2Rh2{C4{CF3)2R'2} plus the dicarbonyl complex (η-C5H,)2Rh2(CO)2(CF3C2CF3). The binuclear pentadienone complexes (η-C5H5),Rh2{C4R2R'2CO) (R = CF, and R' = Me; or R = R' = Et) can be converted into mononuclear cyclopentadienone complexes (η-C5H5)Rh{C4R2R'2CO} by heating in the presence of CO or alkyne, or both.