Pentacarbonyltungsten Complexes Research Articles

Synthesis of 1,1′‐bisphosphinoferrocenes using electrophilic addition reactions of tungsten coordinated phosphenium ions and phosphine triflates

[W(CO)5]-coordinated phosphine triflates undergo electrophilic substitution reactions with ferrocene. We have used this methodology to add PPh2 and PPhCl units to the 1 and 1′ positions of ferrocene to form tungsten pentacarbonyl complexes of 1,1′-bisdiphenylphosphinoferrocene, 1,1′-bischlorophenylphosphinoferrocene, and 1-diphenylphosphino-1′-chlorophenylphosphinoferrocene. The chlorophenylphosphinoferrocenes can be converted to phosphine triflates, and undergo further electrophilic substitutions, allowing us to introduce additional ferrocenyl, allyl, and alkynyl groups, forming tungsten pentacarbonyl complexes of C10H8Fe(PPh2)(PPhR) and C10H8Fe(PPhR)2 (R = allyl, phenylalkynyl, ferrocenyl).

Sub-Nanometer Mapping of the Interfacial Electric Field Profile Using a Vibrational Stark Shift Ruler.

The characterization of electrical double layers is important since the interfacial electric field and electrolyte environment directly affect the reaction mechanisms and catalytic rates of electrochemical processes. In this work, we introduce a spectroscopic method based on a Stark shift ruler that enables mapping the electric field strength across the electric double layer of electrode/electrolyte interfaces. We use the tungsten-pentacarbonyl(1,4-phenelenediisocyanide) complex attached to the gold surface as a molecular ruler. The carbonyl (CO) and isocyanide (NC) groups of the self-assembled monolayer (SAM) provide multiple vibrational reporters situated at different distances from the electrode. Measurements of Stark shifts under operando electrochemical conditions and direct comparisons to density functional theory (DFT) simulations reveal distance-dependent electric field strength from the electrode surface. This electric field profile can be described by the Gouy-Chapman-Stern model with Stern layer thickness of ∼4.5 Å, indicating substantial solvent and electrolyte penetration within the SAM. Significant electro-induction effect is observed on the W center that is ∼1.2 nm away from the surface despite rapid decay of the electric field (∼90%) within 1 nm. The applied methodology and reported findings should be particularly valuable for the characterization of a wide range of microenvironments surrounding molecular electrocatalysts at electrode interfaces and the positioning of electrocatalysts at specific distances from the electrode surface for optimal functionality.

Studies of the interactions of the tungsten pentacarbonyl fluoride anion with carbon dioxide

The FW(CO)5− anion was synthesized by photolysis of W(CO)6 in tetrahydrofuran solution upon the addition of anhydrous PPNF or nBu4NF, and was characterized by infrared and 19F NMR spectroscopies. The complex was shown to be very unstable in solution in the absence of a CO atmosphere. Addition of CO2 to FW(CO)5− in THF provided no evidence of CO2 insertion into the W-F bond, instead affording a bicarbonate tungsten pentacarbonyl complex resulting from hydrolysis by adventitious moisture.

Reactivity of an NHC-Coordinated Trisilacyclopropylidene with Transition Metal Carbonyl Compounds

The reaction of the NHC-coordinated trisilacyclopropylidene F with freshly prepared W(CO)6–n(thf)n (n = 1, 2) yielded in addition to the targeted tungsten pentacarbonyl complex 1 the unexpected NHC...

Synthesis and characterization of tetracarbonylmolybdenum(0) and pentacarbonyltungsten(0) complexes of TADDOL-derived, monodentate P-donor ligands

TADDOL-derived P-donor ligands are of interest as ligands in transition metal catalyzed transformations; however, few studies have been conducted on the steric and electronic properties of P-donor ligands derived from TADDOL. To gain more insight into these properties four tetracarbonylmolybdenum(0) and two pentacarbonyltungsten(0) complexes of monodentate P-donor ligands derived from TADDOL have been studied. These studies show that exchanging the chloro substituent on the phosphorus for OMe increases the donor ability of the ligand and that the cis-tetracarbonylmolybdenum(0) complex of the ligand having the OMe substituent spontaneously isomerizes in solution. X-ray crystallographic analyses indicate that the orientations of the 1,3,2-dioxaphosphepane ring and the aryl substituents are not always conserved, even within the same complex.

Generation and Trapping of Terminal Phosphinidene Complex [CF3P‐W(CO)5

AbstractThe LUMO of [CF3P−W(CO)5] is lower in energy than the LUMO of [ClP−W(CO)5] by 0.30 eV and [CF3P−W(CO)5] is the most electrophilic phosphinidene tungstenpentacarbonyl complex described so far. It is generated by reaction of dimethyl acetylenedicarboxylate with the appropriate 1‐trifluoromethylphosphole complex at 80 oC in toluene. It reacts normally with alkynes to give 1‐trifluoromethylphosphirene complexes. The reaction with alkenes works only with electron‐rich species. The phosphirane complexes appear to be unstable when electron‐poor C=C double bonds are used such as with trans‐stilbene. This highlights the importance of the P to C=C backbonding in the stability of the phosphirane adducts.

Synthesis of P-CPh3 Substituted Spirooxaphosphirane Complexes: Steric Effects Dominate the Product Formation

The reaction of Li/Cl phosphinidenoid pentacarbonyltungsten complex 2 with cyclobutanone and 3-oxetanone led to new, stable spirooxaphosphirane complexes 3 and 4. In contrast, formation of O–H insertion products 5 and 6 was the preferred reaction pathway in case of cyclopentanone and cyclohexanone; this is in contrast to spirooxaphosphirane complex formation with sterically less demanding P-substituents. All complexes have been characterized by heteronuclear NMR spectroscopy and single crystal X-ray analysis in case of 3 and 4.

Transition‐Metal Carbonyl Complexes and Electron‐Donating Properties of N‐Heterocyclic‐Carbene–Phosphinidene Adducts

Rhodium(I), tungsten(0), and molybdenum(0) carbonyl complexes of the N‐heterocyclic‐carbene–phosphinidene adducts IPr·PR [1a, R = H; 1b, R = Ph; 1c, R = Mes; IPr = 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene; Mes = 2,4,6‐trimethylphenyl] were prepared. The reaction of 1b with [Rh(µ‐Cl)(CO)2]2 afforded the dicarbonyl rhodium(I) complex cis‐[(IPr·PPh)RhCl(CO)2] (2) as the major product together with the tetranuclear complex [{µ‐(IPr·PPh)}2Rh4(µ‐Cl)4(CO)4] (3). The latter was characterized by X‐ray diffraction analysis. The tungsten pentacarbonyl complexes [(IPr·PR)W(CO)5] (4a, R = H; 4b, R = Ph; 4c, R = Mes) were isolated from the reactions of 1a–1c with [(Me3N)W(CO)5], whereas the reactions of 1a and 1b with [(thf)Mo(CO)5] (thf = tetrahydrofuran) gave the corresponding molybdenum complexes [(IPr·PR)Mo(CO)5] (5a, R = H; 5b, R = Ph). The molecular structures of the five carbonyl complexes were established by X‐ray diffraction analyses. The IR spectroscopic analysis of the CO stretching frequencies of the carbonyl complexes 2, 4, and 5 revealed the strong electron‐donating abilities of the phosphorus(I) ligands.

Experimental and four‐component relativistic DFT studies of tungsten carbonyl complexes

AbstractWe present a theoretical and experimental study of the structure and nuclear magnetic resonance (NMR) parameters of the pentacarbonyltungsten complexes of η1‐2‐(trimethylstannyl)‐4,5‐dimethylphosphinine, η2‐norbornene, and imidazolidine‐2‐thione. The three complexes have a pseudo‐octahedral molecular structure with the six ligands bonded to the tungsten atom. The η1‐2‐(trimethylstannyl)‐4,5‐dimethylphosphinine‐pentacarbonyl tungsten complex was synthesized for the first time. For all compounds, we present four‐component relativistic calculations of the NMR parameters at the Dirac–Kohn–Sham density functional level of theory using hybrid functionals. These large‐scale relativistic calculations of NMR chemical shifts and spin–spin coupling constants were compared with available experimental data, either taken from the literature or measured in this work. The inclusion of solvent effects modeled using a conductor‐like screening model was found to improve agreement between the calculated and experimental NMR parameters, and our best estimates for the NMR parameters are generally in good agreement with available experimental results. The present work demonstrates that four‐component relativistic theory has reached a level of maturity that makes it a convenient and accurate tool for modeling and understanding chemical shifts and indirect spin–spin coupling constants of organometallic compounds containing heavy elements, for which conventional non‐relativistic theory breaks down. Copyright © 2015 John Wiley & Sons, Ltd.

Intramolecularly C,N-Coordinated Homo- and Heteroleptic Organostannylenes

The synthesis of the C,N-chelated homoleptic organotetrylenes (L1)2E (1, E = Sn; 2, E = Pb) and of the tungsten pentacarbonyl complex (L1)2SnW(CO)5 (3), containing the sterically demanding C,N-chelating ligand L1 (L1 = [2-{(C6H3-2,6-Pri2)N═CH}C6H4]−) is reported. In contrast, the use of the C,N-chelated ligand L2 (L2 = [2-{(C6H3-2,6-Pri2)N═C(Me)}C6H2(OCH2O)]−) provided either the homoleptic stannylene (L2)2Sn (4) or the C,N-chelated chlorostannylene (L2)SnCl (5). All attempts to convert the latter into the corresponding ditin compound [L2Sn]2 failed, however, and resulted in the isolation of 4 and elemental tin. These attempts also provided the unprecedented complex [2-{(C6H3-2,6-Pri2)N═C(Me)}C6H2(OCH2O)][2-{(C6H3-2,6-Pri2)NHCH(Me)}C6H2(OCH2O)]Sn (6).

Improvement of the quadratic non-linear optical properties of pyrimidine chromophores by N-methylation and tungsten pentacarbonyl complexation

In this contribution, we report the synthesis of two series of compounds: 4-(arylvinyl)-1-methylpyrimidinium derivatives and tungsten pentacarbonyl complexes of 4-(arylvinyl)pyrimidines. Their second order non-linear properties, measured by Electric-Field Induced Second Harmonic generation (EFISH) method, and their photophysical behavior were thoroughly investigated and compared to the corresponding 4-(arylvinyl)pyrimidines. A strong enhancement of the NLO response was observed upon methylation or complexation by W(CO)5 of the pyrimidine ring. DFT theoretical calculations were performed to provide complementary insights on the structure-properties relationships in particular concerning the amplitude of the NLO response.

The Evolution of Terminal Allylphosphinidene Pentacarbonyltungsten Complex

DFT computations suggest that terminal allylphosphinidene pentacarbonyltungsten complex 1 can evolve either by intramolecular P + C˭C cycloaddition or by [1,2] H C to P shift to give 2 or 6. Upon thermolysis of the 7-allyl-7-phosphanorbornadiene precursor, the transient complex 1 gives two diastereomeric dimers 4a,b deriving from a head-to-tail P + C˭C intermolecular cycloaddition and another dimer 5 deriving from the [4 + 1] cycloaddition of 1 with 6, followed by an intramolecular hydrophosphination.

An Efficient Route for the Synthesis of 3-(4-Bromophenyl)-2-Phenyl-3,4-Dihydro-2H-Benzo[E][,32,]Oxazaphosphinine, its P-Chalcogenides and Metal Complexes

2-[(4-bromophenylamino)-methyl]-phenol (1) gave substantially pure 3-(4-bromophenyl)-2-phenyl-3,4-dihydro-2H-benzo[e][1,3,2]- oxazaphosphinine (2) on cyclization with phenyldichlorophosphine in toluene at 0 °C. Reaction of 2 with H2O2 in dichloromethane gave selectively 3. P-chalcogenides (4 and 5) were prepared by reacting 2 with elemental S and Se powder in toluene, whereas the tungsten pentacarbonyl complex 6 was prepared by reacting 2 with [W(CO)5(CH3CN)] in tetrahydrofuran at 25 °C. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures.

Multinuclear NMR Spectroscopic and X‐ray Crystallographic Studies of Electronic and Steric Effects of Phosphonous Acid Ligands and Their Chlorophosphite Ligand Precursors in Tungsten Pentacarb­onyl Complexes

Although phosphonous acid ligands have recently become of interest for use in transition metal complex catalysts for organic reactions such as alkene hydroformylations, the factors that affect the steric and electronic properties of these ligands have not been studied in detail. To gain insight into the electronic and steric properties of phosphonous acid ligands, we have prepared tungsten(0) pentacarbonyl complexes with chlorophosphite ligands derived from either 2,2′-biphenol or (±)-1,1′-bi-2-naphthol and have then hydrolyzed the coordinated ligands to generate tungsten(0) pentacarbonyl complexes with the corresponding phosphonous acid ligands. NMR measurements of the W–P coupling constants demonstrate that changing the biaryl groups from biphenyl to binaphthyl does not affect the electron-donor ability of the ligand, whereas changing the third substituent from chloro to oxo has a significant effect. Estimation of cone angles of the ligands from X-ray crystallographic data have shown that neither changing the biaryl group nor changing the third substituent have a significant effect on their cone angles. Further, these studies have identified important intra- and intermolecular interactions that favor certain ligand conformations. The data could be useful for the development of catalytic structure–activity relationships that could be used in the rational design of catalysts.

Coordination of CO to low-valent phosphorus centres and other related P–C bonding situations. A theoretical case study

The multi-faceted bonding of CO in molecular phosphorus compounds is described using calculated P–C bond strengths as a criterion. Full compliance matrices at coupled cluster level of HPCO (1a), singlet oxaphosphirane-3-ylidene HP(η2-CO)), the dimer (HPCO)2 as well as PCH, HPCH2 and H2P–CH3 were calculated to obtain quantifiable data and enable comparison. The quest for CO coordination and activation was examined for phosphaketenes 1a–f: the P–C compliance constants (in A mdyn−1) reveal a clear trend that shows a weakening of the P–CO bond strength from 1a to mono-ligation as in [(OC)5W{P(CO)Me}] (1c) (0.301), in H3BP(CO)Me (1b) (0.322), to bis-ligation as in [{(OC)5W}2P(CO)R] (1f) (0.488) to (H3BP)2(CO)Me (1d) (0.649). Availability of p-type electron density at phosphorus drastically strengthens the P–CO bond and weakens the C–O bond via π–back-donation, bis complexes are better described as weak CO (C→P) adducts to phosphorus. In complexes [(OC)5W{P(CO)R}] the CO activation by phosphorus equals that of CO activation through tungsten in pentacarbonyltungsten complexes. A comparative study of various CO bonding motifs in molecular compounds indicates that acyclic (2) or cyclic diphospha-urea derivatives (2–5) or isomers (6) display P–CO bond strengths (compliance constants range 0.502–0.640) well below that of the P–C bond of H2P–CH3 (0.364), thus providing insight into the bonding and the ease of CO extrusion, experimentally known for some cases. A highly unusual adduct of CO was obtained in silico through two-fold P-ligation in diphosphiren-3-ones 2a–d, the parent compound of which was found to be properly described as a side-on (PP)→(CO) complex, in contrast to its aza-analogue 2aN. A drastic weakening of the P–CO bond strength is observed from P2CO (2a) (0.502) to the C2-symmetrical (H3BP)2CO (2b) (0.913); the latter represents an extreme case of a weakly bound CO. Furthermore, calculated 31P NMR shifts and scalar 1J(P,E) couplings were correlated with P–CO and PC–O compliance constants as a tool for experimentalists.

Reaction of Li/Cl phosphinidenoid complexes with a phosphite substituted ketone: access to complexes with a novel mixed-valence polycyclic P,C-ligand system

Reaction of Li/Cl phosphinidenoid pentacarbonyltungsten(0) complexes 2a,b (R = CH(SiMe3)2, Cp*) with bifunctional phosphite-substituted ketone 3 yielded tungsten complexes 4a,b having a novel mixed-valence polycyclic P,C-cage ligand with a P–P bond. DFT calculations provide insight into an unusual product formation pathway.

Novel Spirooxaphosphirane Complexes

Reaction of a transient Li/Cl phosphinidenoid pentacarbonyltungsten complex 3 (R = C5Me5) with 3-oxetanone, dihydro-3(2H)-furanone, and dihydro-4H-pyran-4-one led to the novel spirooxaphosphirane c...

Tungsten carbonyl σ-complexes of nido-carborane thioethers

Nido-carborane thioethers Cs[X-(CH2)nSMe-7,8-C2B9H11)] (X = 7, 9, n = 0; X = 9, n = 1) were synthesized and their reactions with tungsten carbonyl W(CO)5(THF) were investigated. The corresponding pentacarbonyl tungsten complexes were isolated as cesium salts and characterized. Structure of cesium 7-methylthio-7,8-dicarba-nido-undecaborate was established by single crystal X-ray diffraction.

Generation and Reactivity of Methylphosphaketene in the Coordination Sphere of Tungsten

The [4 + 2] cycloadduct between the 1-methyl-2-keto-1,2-dihydrophosphinine pentacarbonyltungsten complex and dimethyl acetylenedicarboxylate can be used as a precursor for the methylphosphaketene tungsten complex under UV irradiation at room temperature. Under these conditions, the phosphaketene complex easily loses CO to give the methylphosphinidene complex. Highly reactive alcohols and primary alkylamines trap both the phosphaketene and the phosphinidene complexes. Less reactive phenol and bulky amines together with alkynes and conjugated dienes only trap the phosphinidene complex.

Tin(II) and Tin(IV) Compounds with Scorpion‐Shaped Ligands – Intramolecular N→Sn vs. Intermolecular O→Sn Coordination

AbstractThe syntheses of new potentially tetradentate ligands of the type RN(CH2CMe2OH)2 (1, R = Me2NCH2CH2; 2, R = MeOCH2CH2), their tin(II) derivatives RN(CH2CMe2O)2Sn (3, R = Me2NCH2CH2; 4, R = MeOCH2CH2), the pentacarbonyltungsten complexes RN(CH2CMe2O)2SnW(CO)5 (5, R = Me2NCH2CH2; 6, R = MeOCH2CH2) and their oxidation products with bromine, RN(CH2CMe2O)2SnBr2 (7, R = Me2NCH2CH2; 8, R = MeOCH2CH2), are reported. The compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, electrospray ionization mass spectrometry and single‐crystal X‐ray diffraction analysis. DFT calculations on compounds 3, 7 and 8 suggest the preference of dimeric over monomeric structures.