Transmetalation Products Research Articles

Variable Reactivity of a N-Heterocyclic Phosphenium Complex: P-C Bond Activation or "Abnormal" Deprotonation.

The reaction of an N-heterocyclic phosphenium complex of manganese with MeLi/Et3 NHCl under formal addition of CH4 to the Mn=P double bond can be reversed upon UV photolysis, providing a rare example for selective P-C(alkyl) bond activation. Action of LDA on the phosphenium complex does not proceed via attack at phosphorus but rather via C4-deprotonation to yield a unique P-analogue of an "abnormal" carbene. A transmetalation product of the original complex was fully characterized. The C-metalation is also applicable to bis-phosphenium complexes of other metals.

Palladium-Catalyzed Enantioselective Arylation of Aryl Sulfenate Anions: A Combined Experimental and Computational Study.

A novel approach to produce chiral diaryl sulfoxides from aryl benzyl sulfoxides and aryl bromides via an enantioselective arylation of aryl sulfenate anions is reported. A (JosiPhos)Pd-based catalyst successfully promotes the asymmetric arylation reaction with good functional group compatibility. A wide range of enantioenriched diaryl, aryl heteroaryl, and even diheteroaryl sulfoxides were generated. Many of the sulfoxides prepared herein would be difficult to prepare via classic enantioselective oxidation of sulfides, including Ph(Ph-d5)SO (90% ee, 95% yield). A DFT-based computational study suggested that chiral induction originates from two primary factors: (i) both a kinetic and a thermodynamic preference for oxidative addition that places the bromide trans to the JosiPhos-diarylphosphine moiety and (ii) Curtin-Hammett-type control over the interconversion between O- and S-bound isomers of palladium sulfenate species following rapid interconversion between re- and si-bound transmetalation products, re/si-Pd-OSPh (re/si-PdO-trans).

Insertion reactions of bis(silyl)methyl-lithium Li{CH[SiN(Me2)Me2]2} with RCN (R = But, Ph) and their transmetalation products

Four new azaallylamino metallic complexes have been prepared. The insertion reactions of Li{CH[SiN(Me2)Me2]2}(1) with ButCN or PhCN generated azaallyla-mino-lithium Li{[N(Me2)Si(Me2)C(H)C(But)]N[Si(Me2)N(Me2)]·ButCN} (2) or 1,3- diazaallylamino-lithium Li{[N(Me2)Si(Me2)C(H)C(Ph))]N[C(Ph)NSi(Me2)N(Me2)]} (3), respectively. Further transmetalation reaction of 2 with ZrCl4 afforded complex Cl3Zr{[N(Me2)Si(Me2)C(H)C(But)]N[Si(Me2)N(Me2)]}(4), and 3 with SnCl4 yielded Cl3Sn{[N(Me2)Si(Me2)C(H)C(Ph)]N[C(Ph)N(Si(Cl)(Me2))]} (5). The crystal structures of 2, 4 and 5 were reported. Their formation involved 1,3- and 1,5-shift of the bulky silyl group [-Si(NMe2)Me2]. A mechanism of the halogenation reaction is proposed based on the structural parameters of 5.

Iron complexes of a bidentate picolyl-NHC ligand: synthesis, structure and reactivity.

The synthesis, structure and reactivity of bidentate picolyl N-heterocyclic carbene (NHC) iron compounds were studied. Compounds [FeBr(HL)2]Br (1), [FeBr(HL)(HMDS)] (2) and [FeBr2(HL)] (3) (HL = 1-mesityl-3-(pyridin-2-ylmethyl)imidazol-1-ylidene, HMDS = hexamethyldisilazide) were prepared from H2LBr with suitable amounts of Fe(HMDS)2 or in situ prepared [Fe(HMDS)Br]. The deprotonation of 1 with 2 eq. of LiHMDS gave [FeL2] (4), featuring dearomatized pyridine moieties with exocyclic C-C double bonds. The protonation of 4 with 2 eq. of PPh3·HBr results in the formation of 1. Attempted deprotonation of 3 using benzyl Grignard as the base resulted in transmetalation products [FeBnBr(HL)] (5) and [FeBn2(HL)] (6). Exposure of 6 to CO resulted in the formation of diamagnetic compound [Fe(CO)3(HL)] (7) and dibenzyl ketone. Prolonged exposure of 7 to CO with heating induces pyridine dissociation, affording [Fe(CO)4(HL-κC)] (8). Treatment of compound 6 with an equimolar amount of p-methoxybenzyl bromide yielded homo- and cross-coupling products.

Acid-Promoted Selective Carbon–Fluorine Bond Activation and Functionalization of Hexafluoropropene by Nickel Complexes Supported with Phosphine Ligands

The electron-rich complex Ni(PMe3)4 was utilized to react with perfluoropropene to obtain Ni(CF2═CFCF3)(PMe3)3 (1). The selective C–F bond activation process of the π-coordinated perfluoropropene in 1 was conducted with the promotion of Lewis acids (ZnCl2, LiBr, and LiI) under mild conditions to afford the products Ni(CF3C═CF2)(PMe3)2X (X = Cl (2), Br (3), I (4)). The structures of complexes 2 and 3 determined by X-ray single-crystal diffraction confirmed that the C–F bond activation occurred at the geminal position of the trifluoromethyl group. Surprisingly, CF3COOH as a protonic acid could also carry out a similar activation reaction to give rise to Ni(CF3C═CF2)(CF3COO)(PMe3)2 (7), while only the addition products Ni(CF2CFHCF3)(CH3COO)(PMe3) (5) and Ni(CF2CFHCF3)(CH3SO3)(PMe3) (6) were obtained with CH3COOH and CH3SO3H. The transmetalation products Ni(CF3C═CF2)Ph(PMe3)2 (8), Ni(CF3C═CF2)(p-MeOPh)(PMe3)2 (9), and Ni(CF3C═CF2)(C≡CPh)(PMe3)2 (10) were obtained through the reactions of Ni(CF3C═CF2)(PMe3)2Cl...

Speciation of Gd-based MRI contrast agents and potential products of transmetalation with iron ions or parenteral iron supplements

The risk of transmetalation reactions between gadolinium complexes used as contrast agents for magnetic resonance imaging (MRI) and iron ions is examined under physiological conditions. A fast separation of gadopentetate (Gd-DTPA) and gadoterate (Gd-DOTA) and the respective Fe transmetalation products was accomplished by high-performance liquid chromatography. For detection, the LC system was coupled to an Orbitrap electrospray ionization mass spectrometer to achieve a detection limit as low as 50 nmol/L for Fe-DTPA. In vitro experiments revealed the formation of Fe-DTPA in blood plasma samples with Gd-DTPA and Fe(III) citrate. Analysis after different incubation times of the sample showed that the exchange of the metal ions is significantly dependent on time. If this reaction takes place in the body of MRI patients, this could explain why the disease nephrogenic systemic fibrosis (NSF) develops only after a longer retention of the linear Gd complex in the patient's body. Transmetalation either with endogenous Fe(II)/Fe(III) ions or with parenteral Fe supplements with Gd-DTPA could not be proven under the applied conditions. The high stability of Gd-DOTA is responsible that transmetalation between this macrocylic complex and neither of the Fe species was observed. These findings are important because NSF only develops after administration of Gd complexes with linear ligands. The results indicate that transmetalation reactions may be a trigger for the development of NSF, if free Fe(III) ions are accessible during a prolonged dwell time of Gd complexes with linear ligands in the patient's body.

Mechanistic Insights into the Aerobic Copper(I)-Catalyzed Cross-Coupling of S-Acyl Thiosalicylamide Thiol Esters and Boronic Acids

The Density Functional Theory (DFT) method is used to elucidate the nature of the active species and the mechanism of the aerobic CuI-catalyzed cross-coupling of S-acyl thiosalicylamide thiol esters and boronic acids reported previously (J. Am. Chem. Soc.2007, 129, 15734-15735; Angew. Chem., Int. Ed.2009,48, 1417-1421). The energetically lowest isomer of the proposed active species [LC(O)R1]Cu-(O2)-Cu[LC(O)R1]2+, 2a, (where L = thiolatosalicylamide) is found to be I1(OO,OO) with a μ-η2:η2-peroxo Cu2O2-core, while its isomers I2(OO,OO) with a bis-(μ-O) Cu2O2-core and I3(OO,OO) with a (μ-η1:η1) Cu2O2-core lie only a few kcal/mol higher and separated by 4-7kcal/mol energy barriers. In all these isomers, the thiol ester is coordinated to the Cu-centers via its two O-ends. Isomers with (SO,OO) and (SO,SO) coordination modes of the thiol esters lie slightly higher and are separated with moderate energy barriers. We found the latter isomers to be vital for the reported CuI-templated cross-coupling of S-acyl thiosalicylamide thiol esters and boronic acids under aerobic conditions. The presence of an anion (halide, carboxylate modeled as formate) in the reaction medium is found to be necessary. Its coordination to the active catalyst I1(SO,SO) is the first step of the proposed anion-assisted transmetalation by boronic acid. Overall the transmetalation reaction requires 34.0 kcal/mol and is 24.0 kcal/mol exergonic. This conclusion is in reasonable agreement with available experiments. The C-C bond formation in the transmetalation product requires a 6.3 kcal/mol lower energy barrier and is highly exergonic.

Tetrylenes Chelated by Hybrid Amido–Amino Ligand: Derivatives of 2-[(N,N-Dimethylamino)methyl]aniline

Reaction of 2-[(dimethylamino)methyl]aniline with butyllithium, followed by conversion with trimethylsilyl, triphenylsilyl, triphenylgermyl, trimethylstannyl, or tri-n-butylstannyl chloride, gives the corresponding substituted aniline. These compounds were further deprotonated by butyllithium and reacted with germanium, tin, and lead dichlorides, respectively, in both stoichiometric ratios 2:1 and 1:1, providing the target homo- ([2-(Me(2)NCH(2))C(6)H(4)(YR(3))N](2)M) and heteroleptic ([2-(Me(2)NCH(2))C(6)H(4)(YR(3))N]MCl) germylenes and stannylenes, where M = Ge, Sn, Y = Si, Ge, and R = Me, Ph. Unlike all of these cases, the heteroleptic plumbylene can only be obtained with this reaction when the amide is substituted by a trimethylsilyl moiety. Anilines substituted by trimethyltin or tri-n-butyltin moieties gave transmetalation products after the second deprotonation by butyllithium. The trimethyltin-substituted stannylenes could likewise not be obtained by hexamethyldisilazane elimination of (trimethylstannyl)-2-[(dimethylamino)methyl]aniline with 0.5 mol equiv of either bis[bis(trimethylsilyl)amido]tin or {bis[bis(trimethylsilyl)amido]tin chloride}. Products of these reactions are heterocubanes with compositions {[2-(Me(2)NCH(2))C(6)H(4)N]Sn}(4) and [2-(Me(2)NCH(2))C(6)H(4)N](2)(μ(2)-SnMe(2))(2), respectively, and Me(4)Sn or Me(3)SnCl. The structures of trimethylsilyl- and triphenylgermyl-substituted germylenes, stannylenes, and plumbylenes, as well as a number of their precursors, in the crystalline state, were investigated by X-ray diffraction and NMR spectroscopy in solution. Density functional theory methods were used for evaluation of the structures of several compounds.

Analysis of the Contrast Agent Magnevist and Its Transmetalation Products in Blood Plasma by Capillary Electrophoresis/Electrospray Ionization Time-of-Flight Mass Spectrometry

To study transmetalation effects of the gadolinium-based contrast agent Magnevist (Gd-DTPA), the first analytical method for the simultaneous determination of Gd-DTPA and its transmetalation products in complex clinical samples was developed. The high separation efficiency of capillary electrophoresis (CE) was employed to separate Gd-DTPA, Fe-DTPA, Cu-DTPA, Zn-DTPA, and the free DTPA (diethylenetriaminepentaacetic acid) ligand. The coupling of CE with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) provided the required sensitivity and excellent selectivity for the analysis of complex samples, such as blood plasma and whole blood. Separation and detection parameters were optimized, and crucial steps for CE/MS method development are pointed out. Limit of detection (LOD) is 5 x 10(-7) mol/L, limit of quantification (LOQ) is 1.7 x 10(-6) mol/L, and the linear range comprises 2 decades, starting at the limit of quantification. To determine recovery rates, precision, and accuracy of the method, blank plasma samples were spiked with Gd-DTPA in three different concentrations. Blood plasma samples from 10 patients with normal renal function, having received Magnevist, were analyzed for Gd-DTPA and possible transmetalation products by CE/ESI-TOF-MS. The method was validated by determination of the total Gd concentration using inductively coupled plasma optical emission spectroscopy (ICP-OES). Transmetalation assays of Magnevist with and without supplementary iron were carried out in incubated whole blood samples.

Synthesis of a Hafnocene Disilene Complex

Reaction of the magnesium transmetalation product of a 1,2-dipotassiodisilane with hafnocene dichloride gives a disilene hafnocene complex. X-ray crystallography of the respective trimethylphosphane adduct provides structural proof for this assignment.

Mechanism of the Palladium-Catalyzed Metal−Carbon Bond Formation. A Dual Pathway for the Transmetalation Step

The mechanism of the transmetalation step in the metal-carbon bond-formation process catalyzed by palladium complexes has been studied by spectroscopic and kinetic methods. The reaction of properly designed model complexes [structure: see text], resulting from oxidative addition of a Mo-I moiety to a palladium center, with aryltributyltinacetylides Bu(3)Sn-C [triple bond] C-(p-XC(6)H(4)) (11a, X = H; 11b, X = Cl) yields the products of transmetalation [structure: see text] (5a,b). The reaction, which shows a strong dependence on the nature of the phosphine ligand PR(3) (Ph > Bu > Me) and less so on the nature of the p-substituent X group, proceeds through two competing pathways, depending on the initial concentration of substrate. At high [3] (approximately equal to 10(-2) M), the transmetalation proceeds through an intermediate species (12) formed by the interaction of complex 3 with 11a. This associative complex accumulates in the presence of added PPh(3) and has been characterized spectroscopically. At low [3] (approximately equal to 10(-4) M), the reaction rate shows an inverse dependence on the concentration of the complex. This is due to the formation of a solvent-coordinate species (13), in which PPh(3) has been substituted by a dimethylformamide (DMF) molecule, as shown by UV-vis and (31)P NMR spectroscopy. Values of k(obs) depend on the concentration and nature of the aryltributyltinacetylides, in agreement with the existence of a kinetically detectable intermediate. A dimeric iodide bridged complex [structure: see text](14) has been obtained during attempts at isolating 13, which changes quantitatively into 13 upon dissolution in DMF and reacts with 11a to give the transmetalation product.

Transmetalation reactions with nitrogen-containing "pincer"-class ligands on platinum(II) centers

The transmetalation reaction of the aryllithium compound [Li(NCN)]2 (NCN is the monoanionic "pincer" ligand [C6H3(CH2NMe2)2-2,6]-) with the cyclometalated arylplatinum complex [PtCl(NCN)] afforded the bisaryl platinum(II) complex [Pt(NCN)2] (3) containing one η3-N,C,N-terdentate and the other η1-C-monodentate-bonded pincer ligand. Spectroscopic analyses on 3 suggest that η3 to η1 interconversion of the ligand binding mode (or vice versa) is inhibited. Two independent X-ray structure determinations on crystals of 3 revealed the existence of a rare polymorph containing one and three crystallographically independent molecules, respectively, in the unit cell. A similar transmetalation reaction with lithium and platinum complexes containing heteroleptic NCNRR' ligands (NCNRR' is [C6H3(CH2NRR')-2,6]- with R = R' = Me or R = Me, R' = Et) pointed to the formation of a heterodinuclear cationic bisaryl platinum lithium species as an intermediate of a preequilibrium to the final transmetalation products, involving, rapid transcyclometalation (TCM) reactions. These TCM reactions comprise the exchange of the monoanionic NCNRR' ligands between the platinum(II) and lithium centers. A consequence of the latter properties is that the strong Pt—N bonds in [PtX(NCN)] complexes are considerably weakened by the presence of Li+ cations.Key words: transmetalation, transcyclometalation (TCM), platinum, bisaryl complex, polymorphism.

Transmetalation of Tetraalkynyltin Compounds with Grignard Reagents: Access to Mono- and Dialkyltin Products.

Monoalkyltrialkynyl- and dialkyldialkynyltin compounds can be selectively synthesized by transmetalation of tetraalkynyltin compounds with Grignard reagents; an example is given in Equation (1). This reaction provides a route to mono- and dialkyltin compounds that avoids the use of strongly electrophilic reagents. The labile tin-alkynyl bonds allow the transmetalation products to be converted into alkyltin oxides, chlorides, and alkoxides.

Synthesis and Characterization of Substituted Benzyl Zinc Derivatives ‐ Molecular Structures of (tmeda) Li‐CH (GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)Ph]N(H)Si(SiMe3)3

AbstractThe reaction of lithium phenyl(trimethylsilyl)methanide with phenyl(trimethylsilyl)methylzinc chloride‐tmeda in the presence of tmeda yields the addition product, a bis(tmeda)‐lithium dialkylchlorozincate. The elimination of lithium chloride leads to the formation of a tmeda adduct of bis[phenyl‐(trimethylsilyl)methyl]zinc. The metathesis reaction of phenyl(trimethylsilyl)methylzinc chloride‐tmeda with lithium tris(trimethylsilyl)silylamide allows the isolation of the corresponding heteroleptic tmeda complex of an alkylzinc amide. The metalation of phenyl(trimethylstannyl)methane with butyllithium yields the transmetalation product benzyllithium. From the metathesis reaction of this lithium base with anhydrous zinc(II) chloride in the presence of tmeda, the tmeda adduct of dibenzylzinc crystallizes. The molecular structures of (tmeda)LiCH(GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)‐Ph[N(H)Si(SiMe3)3 are reported. Whereas lithium bonds in an η3‐fashion, the zinc atom forms a σ(ZnC) bond. The extremely wide ZnNSi angle in (tmeda)Zn[CH(SiMe3)‐Ph[N(H)Si(SiMe3)3 of 157° is remarkable.

Mechanism of the Palladium-Catalyzed Metal−Carbon Bond Formation. Isolation of Oxidative Addition and Transmetalation Intermediates

To investigate the reaction mechanism of the Pd-catalyzed metal−carbon bond formation, the model compounds [η5-1-Ph2P-2,4-Ph2C5H2](CO)3MI (M = Mo, 12; M = W, 13) have been prepared and their reactions studied under coupling conditions. Treatment of 12 and 13 with stoichiometric amounts of zerovalent palladium yields the complexes [η5-1-Ph2P-2,4-Ph2C5H2](CO)3MPd(PPh3)I (M = Mo, 16; M = W, 17) by oxidative addition of the M−I moieties on Pd0. Subsequent reaction of intermediates 16 and 17 with 4-nitro-1-[2-(tributylstannyl)ethynyl]benzene (Bu3SnC⋮C(C6H4)p-NO2, 18) leads to the formation of the transmetalation products [η5-1-Ph2P-2,4-Ph2C5H2](CO)3MPd(PPh3)C⋮C(C6H4)p-NO2 (M = Mo, 19; W, 20), which have been isolated and characterized. Complexes 13 and 17 have been also characterized by X-ray analysis.

A Study of Heterotetranuclear Transmetalation Products by Fast Atom Bombardment Mass Spectrometry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Study of Heterotetranuclear Transmetalation Products by Fast Atom Bombardment Mass SpectrometryJoel B. Carlson, Geoffrey Davies, and Paul VourosCite this: Inorg. Chem. 1994, 33, 11, 2334–2340Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ic00089a006RIGHTS & PERMISSIONSArticle Views37Altmetric-Citations10LEARN 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 (684 KB) Get e-Alerts Get e-Alerts

Transmetalation of tetranuclear copper complexes with tin transmetalators. Molecular structure of cis-dichloro-bis(trans-S-methyl isopropylidenehydrazinecarbodithioato)tin(IV) and consideration of transmetalation mechanisms

Tin complexes Sn(NS)2Cl2(D) and Sn(NS)4(E) (NS is monoanionic S-methyl isopropylidenehydrazinecarbodithioate) are very good transmetalators of tetranuclear copper(I) target [NCuCl]4 (I: N is N,N-diethylnicotinamide). An X-ray crystallographic study shows that D is cis-dichloro-bis(trans-S-methyl isopropylidenehydrazinecarbodithioato)tin(IV). Evidence that I reacts with 1 or 2 mol of D via strong precursors D·I and D2·I that contain NS ligands bridging tin to copper is used to discuss the transmetalation sequence. The tin-containing transmetalation products include the remarkable air-stable copper(I)-tin(IV) complex N3Cu2Sn(NS)2Cl4 obtained from the reaction of I with equimolar E.

Stoichiometry, products and kinetics of monotransmetalation and complexation of dimeric complexes [N 2CuCl 2] 2 and [N 2NiCl 2] 2 (N is N,N-diethylnicotinamide) with M(NS) 2 reagents in nitrobenzene

This study reports the stoichiometry, products and kinetics of rapid monotransmetalation of the dimeric (μ,μ-dichloro) dichlorotetrakis-( N,N-diethylnicotinamide)dicopper(II) complex N 2ClCu(Cl,Cl)CuClN 2 ( I) with M(NS) 2 reagents, where M is Co, Ni and Zn and NS is a monoanionic S-methyl hydrazinecarbodithioate Schiff base ligand in transmetalators A and B. The isolated transmetalation products are the heterometallic dimers N 2ClCu(Cl,Cl)MClN(H 2O)· H 2O. The stoichiometry and kinetics of complexation of I by A (M=Cu) and of the reaction of the corresponding nickel(II) dimer N 2ClNi(Cl,Cl)NiClN 2 ( II) with transmetalator A (M=Co) are also described. The results are compared with those for monotransmetalation of other halocopper targets with M(NS) 2 transmetalators.

Single-phase Cu 0.50Ni 0.50 alloy preparation by thermolysis of a simple heteropolymetallic precursor

We have found that thermolysis of the heteropolymetallic transmetalation product ( μ 4- O) L 4 Cu 2( Ni( H 2 O)) 2 Cl 6 (L  N,N-diethylnicotinamide) in argon at 350°C is a direct, low-temperature route to the single-phase copper-nickel alloy Cu 0.50Ni 0.50. Homologous heteropolymetallic precursors also give other stoichiometric copper-nickel alloys under the same conditions.

ChemInform Abstract: Stoichiometry and Products of Transmetalation of Dimeric Copper(I) Complexes L2Cu2X2 (L is an N,N,N′,N′‐Tetraalkylethylenediamine; X: Cl or Br) by M(NS)2 Reagents in Aprotic Solvents.

AbstractThe transmetalation products (III) and (IV) from the title reaction of (I) with (II) are obtained in quantitative yield.