Pentacarbonyl Complexes Research Articles

Reactive intermediates relevant to the carbonylation of CH(3)Mn(CO)(5). Activation parameters for key dynamic processes.

Reported is a time-resolved infrared and optical kinetics investigation of the transient species CH(3)C(O)Mn(CO)(4) (I(Mn)) generated by flash photolysis of the acetyl manganese pentacarbonyl complex CH(3)C(O)Mn(CO)(5) (A(Mn)) in cyclohexane and in tetrahydrofuran. Activation parameters were determined for CO trapping of I(Mn) to regenerate A(Mn) (rate = k(CO) [CO][I(Mn)]) as well as the methyl migration pathway to form methylmanganese pentacarbonyl CH(3)Mn(CO)(5) (M(Mn)) (rate = k(M)[I(Mn)]). These values were Delta H(++)(CO) = 31 +/- 1 kJ mol(-1), Delta S(++)(CO) = -64 +/- 3 J mol(-1) K(-1), Delta H(++)(M) = 35 +/- 1 kJ mol(-1), and Delta S(++)(M) = -111 +/- 3 J mol(-1) K(-1). Substantially different activation parameters were found for the methyl migration kinetics of I(Mn) in THF solutions where Delta H(++)(M) = 68 +/- 4 kJ mol(-1) and Delta S(++)(M) = 10 +/- 10 J mol(-1) K(-1), consistent with the earlier conclusion (Boese, W. T.; Ford, P. C. J. Am. Chem. Soc. 1995, 117, 8381-8391) that the composition of I(Mn) is different in these two media. The possible isotope effect on k(M) was also evaluated by studying the intermediates generated from flash photolysis of CD(3)C(O)Mn(CO)(5) in cyclohexane, but this was found to be nearly negligible (k(M)(h)/k(M)(d) (298 K) = 0.97 +/- 0.05, Delta H(++)(M)(d) = 37 +/- 4 kJ mol(-1), and Delta S(++)(M)(d) = -104 +/- 12 J mol(-1) K(-1)). The relevance to the migratory insertion mechanism of CH(3)Mn(CO)(5), a model for catalytic carbonylations, is discussed.

Electron Delocalization in Acyclic andN-Heterocyclic Carbenes and Their Complexes: A Combined Experimental and Theoretical Charge-Density Study

Combined experimental and theoretical charge-density studies on free and metal-coordinated N-heterocyclic carbenes have been performed to investigate the extent of electron delocalization in these remarkable species. Tracing the orientation of the major axis of the bond ellipticity (the least negative curvature in the electron density distribution) along the complete bond paths distinguishes unambiguously between fully delocalized systems and those with interrupted cyclic electron delocalization. Evaluation of charge-density-based properties such as atomic quadrupole moments serves as a direct and quantitative measure of the extent of pi-electron delocalization and reveals consistency between theory and experiment. A detailed topological analysis of theoretical charge densities for two benchmark carbene systems, viz., 1,2-dimethylpyrazol-3-ylidene 1a and 1,3-dimethylimidazol-2-ylidene 2a, and their corresponding stable chromium pentacarbonyl complexes 1 and 2, highlights the advantages of charge-density-based criteria to analyze such complex electronic situations. Thus, 1a and 2a display a different extent of electron delocalization; yet nearly identical p(pi) occupations at the carbene center are computed for 1a and 2a. However, atomic quadrupoles Q(zz) - the charge-density analogues of p(pi) occupation - reveal faithfully the electronic differences in 1a and 2a and demonstrate the sensitivity of charge-density-based properties to the bonding situation. The acyclic aminocarbene (iPr(2)N)(2)CCr(CO)(4) has also been studied, and the high barrier to rotation about the C-N bond is shown not to arise solely from p(pi)-p(pi) bonding.

Metalated 1,3-azaphospholes: synthesis of lithium-1,3-benzazaphospholides and reactivity towards organoelement and organometal halides

Metalation of benzazaphospholes 1a– e with t-BuLi provided the ambident anions 1a– e Li in high selectivity. A crystal structure analysis of 1b Li ·3THF reveals monomers and coordination of lithium at nitrogen. The tungsten pentacarbonyl complexes also react preferably at nitrogen as shown by the reaction of 2a and 2d with t-BuLi. Addition at the PC bond is a minor process in the case of 2a. Compounds 1a, c Li as well as 2d Li react with alkyl halides at phosphorus to give the 3-alkyl-1,3-benzazaphospholes 3a and 3d or the respective W(CO) 5 complex 4d. Even acetyl and pivaloyl chloride attack 1e Li at phosphorus affording the P-acyl derivatives 5e and 6e. Silylation can occur at nitrogen or phosphorus to give 7 and/or 8 depending on steric and electronic effects exerted by the substituent in position 2. The different effect of 2- t-butyl groups on the steric hindrance at N and P is illustrated by the molecular geometry of 1d determined by crystal structure analysis. Soft organometallic halides such as Me 3SnCl, CpFe(CO) 2I and CpW(CO) 3Cl react with 1 Li preferably at phosphorus affording the stannyl or monomer organo-transition metal derivatives 9– 11. The products are characterized by multinuclear NMR data of all new compounds.

Asymmetric Pauson-Khand reactions using camphor-derived chelating thiols as chiral controllers.

A convenient procedure for the preparation of enantiopure 10-(R-thio)-2-exo-bornanethiols from (1S)-camphor-10-thiol has been developed. The ethynyl derivatives of these thiols gave excellent diastereoselectivities (up to 98:2) in Pauson-Khand reactions with norbornene and norbornadiene through the intermediacy of a chelated dicobalt pentacarbonyl complex. Thermal reaction conditions starting from the preformed chelated complex gave better results than N-oxide-promoted runs with in situ generation of the chelated intermediate. The corresponding adducts have been elaborated through a protocol consisting of conjugate addition, samarium iodide-promoted cleavage of the chiral auxiliary, and retro-Diels-Alder reaction to afford 4-substituted 2-cyclopentenones in high enantiomeric purity.

ChemInform Abstract: The Catalytic Transformation of Thiiranes to Cyclic Disulfides by Tungsten Carbonyl Complexes

Abstract This report reviews our recent studies of the catalytic transformations of thiiranes and vinylthiiranes by tungsten pentacarbonyl complexes. Whereas the thiranes yield only macrocyclic polydisulfides, the latter reactions yield only the cyclic monodisulfides known as 3,6-dihydro-1,2-dithiins.

Acylamino Chromium Carbene Complexes: Direct Carbonyl Insertion, Formation of Münchnones, and Trapping with Dipolarophiles.

Acylamino Chromium Carbene Complexes: Direct Carbonyl Insertion, Formation of Münchnones, and Trapping with Dipolarophiles.

Physical Organic Chemistry of Transition Metal Carbene Complexes. 17.1 Kinetics of the Reactions of (Arylthioalkoxycarbene)pentacarbonyl Complexes of Chromium(0) and Tungsten(0) with Thiolate Ions in Aqueous Acetonitrile: pKa Values of the Metal-Protonated Tetrahedral Adducts Formed between Carbene Complexes and Thiolate Ion [J. Am. Chem. Soc. 1999, 121, 11384−11394

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionPhysical Organic Chemistry of Transition Metal Carbene Complexes. 17.1 Kinetics of the Reactions of (Arylthioalkoxycarbene)pentacarbonyl Complexes of Chromium(0) and Tungsten(0) with Thiolate Ions in Aqueous Acetonitrile: pKa Values of the Metal-Protonated Tetrahedral Adducts Formed between Carbene Complexes and Thiolate Ion [J. Am. Chem. Soc.1999, 121, 11384−11394].Claude F. Bernasconi and Mahammad AliCite this: J. Am. Chem. Soc. 2000, 122, 29, 7152Publication Date (Web):July 8, 2000Publication History Published online8 July 2000Published inissue 26 July 2000https://doi.org/10.1021/ja004653rCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views304Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (9 KB) Get e-Alerts Get e-Alerts

The synthesis and characterisation of two mononuclear tungsten pentacarbonyl complexes of 4,4′-bipyridine and 1,2-bis(4-pyridyl)ethane

The mononuclear tungsten pentacarbonyl complexes with 1,2-bis(4-pyridyl)ethane and 4,4′-bipyridine were synthesised by the irradiation, with a UV source, of solutions of tungsten hexacarbonyl and the relevant N-containing ligand. Both complexes were characterised by single-crystal X-ray diffraction and in both structures, the coordination geometry of the tungsten atom is slightly distorted from octahedral.

A new route to pentafluorophenylmolybdenum(0) carbonyl complexes. Synthesis and X-ray crystal structure of PPN[Mo(C 6F 5)(CO) 5

In order to facilitate studies of the synthesis and reactivity of pentafluorophenylmolybdenum(0) carbonyl complexes, an efficient synthetic route to the pentacarbonyl complex, [Mo(C 6F 5)(CO) 5] −, has been sought. It has now been shown that the known organometallic compounds AgC 6F 5 and PPN[MoCl(CO) 5] [PPN=bis(triphenylphosphoranylidene)ammonium] react to give PPN[Mo(C 6F 5)(CO) 5] in high purity and good yield. This compound has been characterized by IR, NMR, elemental analysis, and X-ray crystallography.

Preparation and reaction of desymmetrised cobalt alkyne complexes

Prochiral alkyne hexacarbonyl dicobalt complexes are desymmetrised directly with brucine N-oxide in the presence of a phosphine or phosphite ligand to produce the corresponding phosphorus-containing pentacarbonyl complex with appreciable enantiomeric excess. In Pauson–Khand reactions, it is found that the enantiomeric integrity of the desymmetrised complex is conserved in the cyclopentenone product. Moreover, the major enantiomer obtained in these reactions is opposite to that from a direct brucine N-oxide promoted Pauson–Khand reaction, allowing the preparation of either enantiomeric cyclopentenone in enriched form from a single source of chirality.

The catalytic transformation of thiiranes to cyclic disulfides by tungsten carbonyl complexes

This report reviews our recent studies of the catalytic transformations of thiiranes and vinylthiiranes by tungsten pentacarbonyl complexes. Whereas the thiranes yield only macrocyclic polydisulfides, the latter reactions yield only the cyclic monodisulfides known as 3,6-dihydro-1,2-dithiins.

Glycosylmanganese pentacarbonyl complexes: an organomanganese-based approach to the synthesis of C-glycosyl derivatives

Preparation, structure and reactions of glycosylmanganese pentacarbonyl complexes are discussed. Anomerically pure complexes of pyranosyl and furanosyl complexes were prepared in excellent yield. The conformations of the anomeric glucosyl and mannosyl complexes were derived from detailed analysis of their 1D and 2D 1H- and 13C-NMR spectra including NOE data. The complexes are further characterized by 55Mn-NMR chemical shifts and 55Mn, 13C one-bond coupling constants. These compounds undergo various migratory insertion reactions resulting in formation of C-glycosyl derivatives. Applications of this technology to the synthesis of C-glycosyl and C-aryl glycosidic systems are discussed.

Physical Organic Chemistry of Transition Metal Carbene Complexes. 17.1 Kinetics of the Reactions of (Arylthioalkoxycarbene)pentacarbonyl Complexes of Chromium(0) and Tungsten(0) with Thiolate Ions in Aqueous Acetonitrile: pKa Values of the Metal-Protonated Tetrahedral Adducts Formed between Carbene Complexes and Thiolate Ion

Physical Organic Chemistry of Transition Metal Carbene Complexes. 17.¹ Kinetics of the Reactions of (Arylthioalkoxycarbene)pentacarbonyl Complexes of Chromium(0) and Tungsten(0) with Thiolate Ions in Aqueous Acetonitrile: p<i>K</i>_a Values of the Metal-Protonated Tetrahedral Adducts Formed between Carbene Complexes and Thiolate Ion

Coordination Chemistry, Structure, and Reactivity of Thiouracil Derivatives of Tungsten(0) Hexacarbonyl: A Theoretical and Experimental Investigation into the Chelation/Dechelation of Thiouracil via CO Loss and Addition.

The synthesis of 2-thiouracil and 6-methyl-2-uracil derivatives of tungsten carbonyl from the reaction of photogenerated W(CO)(5)(solvent) (solvent = MeOH or THF) and the corresponding [Et(4)N][thiouracilate] is described. The crystal structure of the [Et(4)N][W(CO)(5)(2-thiouracilate)], 1, derivative is reported where the thiouracilate is found to be bound to the tungsten center via the exocyclic sulfur atom. In the solid-state structure of 1 two anions are associated by means of two hydrogen bonds between the metal bound nucleobases. These pentacarbonyl complexes stereoselectively lose cis carbonyl ligands, as is apparent from (13)C-labeling studies, to provide the endocyclic nitrogen N(1)-chelated tungsten tetracarbonyl derivatives, e.g., [Et(4)N][W(CO)(4)(2-thiouracilate)], 3. The kinetics of the loss of CO from the pentacarbonyl anions to afford the metal tetracarbonyls, and the reverse of that process, were monitored by means of in situ infrared spectroscopy in the nu(CO) region as a function of temperature. These studies reveal that the tetracarbonyl anions in CO-saturated acetonitrile ([CO] approximately 6 x 10(-)(3) M) are unstable with respect to the formation of the pentacarbonyl derivatives, i.e., the equilibrium 1 right harpoon over left harpoon 3 + CO lies to the left under an atmosphere of carbon monoxide. From the activation parameters determined for the dissociative CO loss process (DeltaH() = 82.0 +/- 3.6 kJ mol(-)(1) and DeltaS() = -44.9 +/- 9.6 J mol(-)(1) K(-)(1) for complex 1) it is apparent that the sulfur-bound thiouracilate ligand is serving as a pi-donor during CO dissociation, i.e., behaving as a cis-labilizing ligand. Ab initio geometry optimizations carried out for the process 1 right harpoon over left harpoon 3 + CO at the Hartree-Fock and DFT levels support these experimental observations. For example, complex 1 is shown to be more stable than 3 + CO and chelation via the endocyclic N(1) donor is favored over N(3) binding. Finally, the "16-electron" intermediate resulting from CO dissociation in 1 was found to possess a significantly shortened W-S interaction, presumably due to the pi-donating ability of the thiouracilate ligand.

Direct synthesis of cyclic and polymeric phosphazenes bearing diphenylphosphine groups and their complexes with [W(CO) 5] fragments

The reactions of the cyclotriphosphazenes [N 3P 3Cl 6] or [N 3P 3(O 2C 12H 8) 2Cl 2] with the phenolic phosphine PPh 2(C 6H 4-OH) in the presence of Cs 2CO 3 give, respectively, the cyclic phosphazene phosphines [N 3P 3(OC 6H 4PPh 2) 6] ( 1) and [N 3P 3(O 2C 12H 8) 2(OC 6H 4PPh 2) 2] ( 2), very pure and in high yield. The similar reaction with the linear polyphosphazene {[NP(O 2C 12H 8)] 0.65[NPCl 2] 0.35} n in THF gives the diphenylphosphine polymer {[NP(O 2C 12H 8)] 0.65[NP(OC 6H 4PPh 2) 2] 0.35} n ( 3). The phenolic tungsten pentacarbonyl complex {W(CO) 5[PPh 2(C 6H 4-OH)]} reacts in the same way with those cyclic and polymeric phosphazenes to give the corresponding complexes {N 3P 3[OC 6H 4PPh 2-W(CO) 5] 6} ( 4), [N 3P 3(O 2C 12H 8) 2(OC 6H 4PPh 2-W(CO) 5) 2] ( 5), and {[NP(O 2C 12H 8)] 0.65[NP(OC 6H 4PPh 2-W(CO) 5) 2] 0.35} n ( 6).

First structural characterisation of 1,2,4-selenadiphosphole and 1,2,4-telluradiphosphole ring systems. Crystal and molecular structures of the η 1-complexes [M(CO) 5(P 2SeC 2Bu t2)] (M=Cr, W) and [W(CO) 5(P 2TeC 2Bu t2)

The molecular geometries of the 1,2,4-selenadiphosphole and the 1,2,4-telluradiphosphole aromatic ring systems, established by single crystal X-ray diffraction studies on their metal pentacarbonyl complexes, are presented and discussed together with theoretical data.

1,3-Distanna-2-phospha-[3]ferrocenophanes - Synthesis, Reactivity and NMR Spectroscopic Properties

1,1,3,3-Tetramethyl-2-organo(R)-1,3-distanna-2-phospha-[3]ferrocenophanes [R = Me (2a), tBu (2b), C6H11 (2c), Ph (2d)] and one arsa-analogue 2d(As) were obtained from the reaction of 1,1′-bis(chlorodimethylstannyl)ferrocene 1 with either bis(trimethylsilyl)methylphosphane or the dilithio derivatives, Li2PR and Li2AsPh, respectively. All compounds 2 react with chalcogens (oxygen, sulfur, selenium) by cleavage of the Sn-P bonds and formation of the known 1,3-distanna-2-chalcogena-[3]ferrocenophanes. In contrast, 2d traps pentacarbonylmetal fragments [M(CO)5] to give the stable phosphane complexes [M = Cr (4d), Mo (5d), W (6d)]. The 1,1′-bis(diorganophosphanostannyl)ferrocenes [R = tBu (3b), Ph (3d)] were prepared for comparison of NMR data. The ferrocenophanes 2 are fluxional with respect to fast movement of the cyclopentadienyl rings which induces inversion at the pyramidal phosphorus atom. This dynamic process is slow in the cases of 2d(As) and of the pentacarbonyl complexes 4d - 6d. All new compounds were characterised by 1H, 13C, 31P and 119Sn NMR spectroscopy. Various 2D heteronuclear shift correlations (e.g. 31P/1H and 119Sn/1H ) were carried out for the compounds 2 and also for non-cyclic derivatives such as bis(trimethylstannyl)phenvlphosphane and -arsane in order to determine absolute signs of coupling constants [e.g. 1J(119Sn,31P) &gt; 0 and 2J(119Sn,117Sn) &lt; 0]. The NMR data suggest that the molecular frameworks of the ferrocenophanes 2 are not particularly strained.

Camphor-Derived, Chelating Auxiliaries for the Highly Diastereoselective Intermolecular Pauson-Khand Reaction: Experimental and Computational Studies.

A family of enantiomerically pure (2R)-10-(alkylthio)isoborneols [methylthio (1), neopentylthio (2), phenylthio (3)], specifically designed as chiral auxiliaries suitable for chirality transfer to cobalt in Pauson-Khand reactions, has been synthesized. The dicobalt hexacarbonyl complexes of the alkoxyacetylenes derived from these alcohols (10a-12a) can be converted to the rather stable, internally chelated, pentacarbonyl complexes 10b-12b by treatment with NMO. The intermolecular Pauson-Khand reactions of 10b-12b with strained olefins take place with synthetically useful rates at low temperatures (down to -20 degrees C), with high yields and diastereoselectivities: norbornene (77%; 92:8), norbornadiene (82%; 96:4), bicyclo[3.2.0]hept-6-ene (91%; 93:7). The major diastereomer of the adduct of 10b with norbornadiene, 14, has been used as the starting point for a synthesis of (S)-(-)-4-alkyl-2-cyclopentenones through a sequence consisting of completely diastereoselective conjugate addition, reductive cleavage with recovery (>95%) of the chiral auxiliary, and retro Diels-Alder reaction. The stereochemical course of the reaction of 10b with norbornadiene has been analyzed and rationalized by theoretical means by using a combined semiempirical [PM3(tm)]/density functional theory [VWN-Perdew-Wang 91] approach.

The First Carbonyl Bond Dissociation Energies of M(CO)5and M(CO)4(C2H2) (M = Fe, Ru, and Os): The Role of the Acetylene Ligand from a Density Functional Perspective

Recent kinetics experiments have shown that the rate of carbonyl substitution in complexes of the type M(CO)4(C2R2), where M = Fe, Ru, and Os, is accelerated by factors of 102−1013 over their respective pentacarbonyl complexes. These substitution reactions have been shown to be dissociative in nature and show a marked metal dependence of the rate. The origin of the increased reactivity of these alkyne complexes was studied with nonlocal density functional theory (BLYP functional), using both effective core potential (ECP) and all-electron basis sets, in conjunction with Frenking's charge decomposition analysis (CDA) scheme and Bader's atoms in molecules (AIM) analysis. We found that the BLYP/ECP method predicted geometries very close to experiment for both the parent carbonyl and alkyne complexes (in this study C2H2 was used). The calculated CO bond dissociation energies (BDEs) were also found to agree well with experiment and mirrored the metal dependence trends observed experimentally for both M(CO)5 an...

Studies of a Reluctant Ligand. An X-ray Crystallographic and NMR Spectroscopic Analysis of (OC)5W(η1-PPh2CH2PPh2) and Its (OC)5W(μ-PPh2CH2PPh2)W(CO)5 Derivative

Tungsten pentacarbonyl complexes, (OC)5W(η1-PPh2CH2PPh2) (1) and (OC)5W(μ-PPh2CH2PPh2)W(CO)5 (2), have been synthesized from (OC)5WNH2Ph and Ph2PCH2PPh2 in toluene, and their solid-state structures have been determined by single-crystal X-ray diffraction. The lone pair of electrons on the dangling phosphine in 1 is oriented toward the W(CO)5 unit in the solid state, and 13C{1H} and 31P{1H} NMR data suggest that this conformation may also be dominant in solution. Phosphorus−phosphorus coupling in 1 (2JPP = 106 Hz) is significantly larger than in any previously reported complex of Ph2PCH2PPh2 and is highly dependent on changes in temperature and solvent. Also observed is an unprecedented long-range phosphorus−carbon coupling (4JPC = 3.0 Hz) between the dangling phosphine and the equatorial carbonyl carbons of 1, which is attributed to a conformational and/or “through-space” enhancement. On the basis of the structural and spectral data, the reluctance of 1 to react with (OC)5WNH2Ph to give 2 is explained in ...