Main Group Metal Compounds Research Articles

When Is a Bond Broken? The Polarizability Perspective.

The question of when a chemical bond can be said to be broken is of fundamental chemical interest but has not been widely studied. Herein we propose that the maxima of static polarizability along bond dissociation coordinates naturally define cutoff points for bond rupture, as they represent the onset of localization of shared electron density into constituent fragments. Examples of computed polarizability maxima over the course of bond cleavage in main-group and transition metal compounds are provided, across covalent, dative and charge-shift bonds. The behavior along reaction paths is also considered. Overall, the static polarizability is found to be a sensitive reporter of electronic structure reorganization associated with bond stretching, and thus can serve as a metric for describing bond cleavage (or diagnose the absence of a chemical bond).

Speciation and Photoluminescent Properties of a 2,6‐Bis(pyrrol‐2‐yl)pyridine in Three Protonation States

Abstract2,6‐Bis(pyrrol‐2‐yl)pyridines are important building blocks for supramolecular assemblies and photoluminescent main group and transition metal compounds. Sterically encumbered 2,6‐bis(5‐(2,4,6‐trimethylphenyl)‐3‐phenyl‐1H‐pyrrol‐2‐yl)pyridine, H2MesPDPPh, can adopt monomeric and dimeric structures in the solid state and in solution, controlled by competing inter‐ and intramolecular hydrogen bonds. Deprotonation in the presence of lithium cations provides Li2MesPDPPh, which can be isolated in monomeric and dimeric forms depending on solvent polarity. Protonation of H2MesPDPPh disrupts intramolecular hydrogen bonding and provides the monomeric pyridinium salt [H3MesPDPPh]Cl. Independent of solvent polarity, all three derivatives exhibit intense fluorescence in solution. The absorption and emission spectra are highly sensitive to the level of protonation, which can be rationalized by the effects of (de)protonation on the HOMO and LUMO of the tricyclic π‐system.

Redox-active ligands - a viable route to reactive main group metal compounds.

Anionic redox-active ligands such as o-amidophenolates, catecholates, dithiolenes, 1,2-benzendithiolates, 2-amidobenzenethiolates, reduced α-diimines, ferrocenyl and porphyrinates are capable of reversible oxidation and thus have the ability to act as sources of electrons for metal centres. These and other non-innocent ligands have been employed in coordination complexes of base transition metals to influence their redox chemistry and afford compounds with useful catalytic, optical, magnetic and conducting properties. Despite the focus in contemporary main group chemistry on designing reactive compounds with potential catalytic activity, comparatively few studies exploring the chemistry of main group metal complexes incorporating redox-active ligands have been reported. This article highlights relevant chemical reactivity and electrochemical studies that probe the oxidation/reduction of main group metal compounds possessing redox-active ligands and comments on the prospects for this relatively untapped avenue of research.

Magnesium Pincer Complexes and Their Applications in Catalytic Semihydrogenation of Alkynes and Hydrogenation of Alkenes: Evidence for Metal-Ligand Cooperation.

The development of catalysts for environmentally benign organic transformations is a very active area of research. Most of the catalysts reported so far are based on transition-metal complexes. In recent years, examples of catalysis by main-group metal compounds have been reported. Herein, we report a series of magnesium pincer complexes, which were characterized by NMR and X-ray single-crystal diffraction. Reversible activation of H2 via aromatization/dearomatization metal–ligand cooperation was studied. Utilizing the obtained complexes, the unprecedented homogeneous main-group metal catalyzed semihydrogenation of alkynes and hydrogenation of alkenes were demonstrated under base-free conditions, affording Z-alkenes and alkanes as products, respectively, with excellent yields and selectivities. Control experiments and DFT studies reveal the involvement of metal–ligand cooperation in the hydrogenation reactions. This study not only provides a new approach for the semihydrogenation of alkynes and hydrogenation of alkenes catalyzed by magnesium but also offers opportunities for the hydrogenation of other compounds catalyzed by main-group metal complexes.

Catalysis using transition metal complexes featuring main group metal and metalloid compounds as supporting ligands.

Recent development in catalytic application of transition metal complexes having an M–E bond (E = main group metal or metalloid element), which is stabilized by a multidentate ligand, is summarized. Main group metal and metalloid supporting ligands furnish unusual electronic and steric environments and molecular functions to transition metals, which are not easily available with standard organic supporting ligands such as phosphines and amines. These characteristics often realize remarkable catalytic activity, unique product selectivity, and new molecular transformations. This perspective demonstrates the promising utility of main group metal and metalloid compounds as a new class of supporting ligands for transition metal catalysts in synthetic chemistry.

From organotin hydrides to heteronuclear main group metal compounds: isolation of the first neutral bismuth/tin clusters.

From conversions of Ar2SnH2 (Ar = Tripp, Dipp; Tripp = 2,4,6-Triisopropylphenyl, Dipp = 2,6-Diisopropylphenyl), and a bismuth(III) amide, Bi[N(SiMe3)2]3, we isolated the first representatives of mixed, uncharged Bi/Sn clusters, Bi8Sn3Ar6. Along with unprecedented bicyclo[2.2.0]hexanes, (HAr2Sn)2Sn2Bi4, these have been characterized by single crystal X-Ray diffraction, heteronuclear NMR, vibrational and UV-Vis spectroscopy. Quantum-chemical calculations were carried out in order to understand bonding within the isolated polyhedral compounds.

Flexible and Versatile Pincer-Type PGeP and PSnP Ligand Frameworks

We describe the synthesis and application of two phosphine-functionalized pincer-type N-heterocyclic carbene analogues [(PNNP)E] (E = Ge, Sn) and their reactivity toward main group and precious metal compounds. These flexible tetrelene ligands feature unusual coordination geometries and strong P–E interactions and are expandable to digermylene or distannylene compounds on reaction with ECl2. The compounds were also successfully applied as ligands for the synthesis of Cu, Ag, Au, and Pt complexes. The inherent flexibility of the ligand scaffold enabled different structural arrangements driven by the coordination requirements of the metal centers and intermetallic interactions.

Synthesis, characterization, and catalytic performance of Aluminum and Tin Compounds with β-diketiminato ligand

Two new tin (II) and tin (IV) compounds [LSnCl] (1) and [LSnCl3] (2), bearing the β-diketiminato ligand LH (L = HC(CMeNAr)2, Ar = 2,6-Et2C6H3) were synthesized by the reactions of LH with n-BuLi, then respectively with SnCl2 and SnCl4. Two new aluminum alkyl compounds, [LAlMe2] (3) and [LAlEt2] (4), were synthesized in high yield from the reactions of LH with AlMe3 and AlEt2, respectively. Compound [LAlI2] (5) was synthesized from the reaction of 3 with I2 in good yield. All these main group metal compounds bearing β-diketiminato ligand LH were fully characterized by 1H NMR and 13C NMR spectroscopy, and elemental analysis. Meanwhile, compounds 1, 2, 3, and 5 were characterized by single crystal X-ray structural analysis. Moreover, the well-defined compounds 1–4 were investigated to show good catalytic activity in hydroboration of terminal alkynes.

Reactions of Germylenes and Stannylenes with Halo(hydrocarbyl)- and Chloro(amino)phosphines: Oxidative Addition versus Ligand Transfer.

Oxidative addition (OA) is an important elementary step in chemistry, but it has been studied mainly in the context of transition-metal-catalyzed reactions and mainly with carbon-X substrates (X = halogen, H). Reports of main-group metal compounds undergoing OA are rare by comparison, and those involving phosphorus-halogen substrates are rarer still. Acyclic and cyclic diazagermylenes and -stannylenes react with chloro(hydrocarbyl)phosphines with the intermediacy of oxidative addition products. Stannylenes react faster than germylenes, and these reactions are first-order in both reactants and slowed by steric bulk. Kinetic data and the structures of intermediates and products had suggested an adduct/insertion mechanism for these reactions. To gain further insight into these transformations, the work presented herein was extended to chloro(hydrocarbyl)phosphines with varying organic substituents. These studies confirmed prior conclusions concerning the rate-diminishing effect of steric bulk, and the rate dependence on leaving groups also seems to suggest adduct/insertion or SN2 mechanisms. Importantly, these new data now also point to associative decomposition pathways. In the course of the investigation, it was discovered that aliphatic chloro(amino)phosphines react differently with the carbene analogues, giving oxidative addition products for germylenes but metathesis reactions for stannylenes.

ChemInform Abstract: Applications of N‐Heterocyclic Imines in Main Group Chemistry

AbstractReview: [51 refs.

Oxidative addition of organic disulfides to low valent N,C,N-chelated organobismuth(I) compound: Isolation, structure and coordination capability of substituted bismuth(III) bis(arylsulfides)

The reaction between in situ prepared THF solution of N,C,N-chelated organobismuth(I) [LBi]n compound (not isolated), via reaction of LBiCl2 (1) (where L = [o,o-C6H3(CH2NMe2)2]) with K[B(s-Bu)3H] (K-Selectride), and a set of diorganodisulfides ArSSAr gave organobismuth(III) compounds LBi(SAr)22–7 (where Ar = 2-pyridyl (2), 4-metylthiazol-2-yl (3), thiofen-2-yl (4), 4-tert-butyl-1-iso-propyl-1H-imidazol-2-yl (5), 1-phenyl-1H-tetrazol-5-yl (6), 2-aminophenyl (7)). Compounds 2–7 were characterized by the help of elemental analysis, 1H and 13C NMR spectroscopy and in the case of 2, 3 and 6 by the help of single-crystal X-ray diffraction analysis. Compound 7 was unstable in solution and decomposed to compound LBi[S(NH)C6H4] (8), containing five-membered BiSNC2 ring, and the 2-aminothiophenol. Attempts to selectively cleave the Bi–N bond involved in this ring by an acid (such as HCl or acetic acid) failed and led only to the isolation of 1 or acetate LBi(Ac)2 and elimination of 2-aminothiophenol. Finally, the coordination capability of compound 2 toward both main group (SbCl3, BiCl3, GeCl2 and SnCl2) and transition metal (PdCl2 and PtCl2) compounds was studied.

ChemInform Abstract: Agostic Bonds in Cyclometalation

AbstractReview: 131 refs.

Quantitative Computational Thermochemistry of Transition Metal Species

The correlation consistent Composite Approach (ccCA), which has been shown to achieve chemical accuracy (+/-1 kcal mol-1) for a large benchmark set of main group and s-block metal compounds, is used to compute enthalpies of formation for a set of 17 3d transition metal species. The training set includes a variety of metals, ligands, and bonding types. Using the correlation consistent basis sets for the 3d transition metals, we find that gas-phase enthalpies of formation can be efficiently calculated for inorganic and organometallic molecules with ccCA. However, until the reliability of gas-phase transition metal thermochemistry is improved, both experimentally and theoretically, a large experimental training set where uncertainties are near +/-1 kcal mol-1 (akin to commonly used main group benchmarking sets) remains an ambitious goal. For now, an average deviation of +/-3 kcal mol-1 appears to be the initial goal of "chemical accuracy" for ab initio transition metal model chemistries. The ccCA is also compared to a more robust but relatively expensive composite approach primarily utilizing large basis set coupled cluster computations. For a smaller training set of eight molecules, ccCA has a mean absolute deviation (MAD) of 3.4 kcal mol-1 versus the large basis set coupled-cluster-based model chemistry, which has a MAD of 3.1 kcal mol-1. However, the agreement for transition metal complexes is more system dependent than observed in previous benchmark studies of composite methods and main group compounds.

JIRO TSUJI. Palladium reagents and catalysts: new perspectives for the 21st century. Wiley–VCH, 2004. 670 pp. ISBN 0470850337 (paperback)

JIRO TSUJI. Palladium reagents and catalysts: new perspectives for the 21st century. Wiley–VCH, 2004. 670 pp. ISBN 0470850337 (paperback)

Energy decomposition analysis of the chemical bond in main group and transition metal compounds.

The nature of the chemical bond in the main group diborane(4) compounds X2B-BX2 (X = H,F,Cl,Br,I) and in the Fischer- and Schrock-type transition metal carbene and carbyne complexes and heavier homologues (CO)5W-CH2, (CO)5W-E(OH)2, Cl4W-EH2, Cl(CO)4W-EH and Cl3W-EH (E = C,Si,Ge,Sn,Pb) have been investigated with an energy decomposition analysis (EDA). The results give a deep insight into the nature of the chemical interactions. The EDA results can be used as a bridge between the heuristic models of experimental chemists which have been proven as useful ordering schemes for experimental observations and the physical mechanism which leads to a chemical bond. At the time the data give a well defined qantitative answer to the questions about the strength of the covalent and electrostatic interactions and about the contributions of sigma and pi electrons to the covalent bond.

Editorial: main group metal compounds

Applied Organometallic ChemistryVolume 17, Issue 1 p. 1-1 EditorialFree Access Editorial: main group metal compounds Peter Craig, Peter CraigSearch for more papers by this authorMarcel Gielen, Marcel GielenSearch for more papers by this author Peter Craig, Peter CraigSearch for more papers by this authorMarcel Gielen, Marcel GielenSearch for more papers by this author First published: 06 December 2002 https://doi.org/10.1002/aoc.405Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume17, Issue1January 2003Pages 1-1 RelatedInformation

Exploring the Lewis basicity of the metalloligand [Pt2(µ-Se)2(PPh3)4] on metal substrates by electrospray mass spectrometry. Synthesis, characterization and structural studies of new platinum selenido phosphine complexes containing the {Pt2Se2} core

Electrospray Mass Spectrometry (ESMS) has been used as a tool to probe the reactivity of the metalloligand [Pt2(μ-Se)2(PPh3)4] with metal substrates, which lead to the formation of charged coordination complexes via loss of halides or other labile ligands. Among the numerous metal substrates used in the displacement reactions are Au(anpy)Cl2 (anpy = cyclometallated 2-anilinopyridyl), HgPhCl and Pb(NO3)2. Acid titration on the Lewis basic metalloligand leads to the identification and isolation of the doubly-protonated species, [Pt2(μ-SeH)2(PPh3)4]2+, whose sulfide analogue cannot be isolated. A three-step strategy is employed in the use of ESMS as a probe: (i) preliminary screening of the metalloligand with an array of acidic main group and transition group metal compounds, (ii) identification of potentially stable and isolable products formed in situ based on ion distribution and simulated isotope patterns and (iii) promising reactions are repeated on a laboratory scale, and target products are isolated and characterized. X-Ray diffraction studies have been performed on single crystals of [Pt2(μ-SeH)2(PPh3)4][ClO4]2, [Pt2(μ3-Se)2(PPh3)4(CdCl2)] and {Pt2(μ3-Se)2(PPh3)4[Pb(NO3)]}{NO3}. These results suggested that in general a parallel chemistry can be developed on the intermetallic selenides as on the sulfides. However, there are chemical and structural differences which are highlighted in this paper.

Synthesis and Characterization of (−)-1-Menthyl-4,7-dimethylindene and Its Main Group Metal Compounds with Lithium, Sodium, Potassium, and Tin

(−)-3-Menthyl-4,7-dimethylindene and (−)-4,7-diisopropyl-3-menthylindene were prepared in 63 and 48% yield, respectively, through a 1,1‘-bis(diphenylphosphino)ferrocene-palladium-catalyzed cross-coupling reaction of menthylzinc with 3-(4,7-dimethylindenyl) trifluoromethanesulfonate or 3-(4,7-diisopropylindenyl) trifluoromethanesulfonate. Several other methods including addition of menthyl Grignard to 1-indanone, addition of (indenyl)lithium to menthone, or coupling of 3-bromoindene with menthyl Grignard for preparing 1-(or 3-)menthylindene were inferior to direct substitution of menthyl sulfonate esters by (indenyl)lithium. (−)-3-Menthyl-4,7-dimethylindene could be deprotonated to form a single diastereomeric lithium salt that was characterized by X-ray crystallography. (−)-4,7-Diisopropyl-3-menthylindene was deprotonated to form a lithium salt. Formation of the sodium and potassium salts of (−)-3-menthyl-4,7-dimethylindene was possible, but the products were not stereochemically characterized. 1-Trialkyl...

X-ray photoelectron spectroscopic studies of sulfates and bisulfates interpreted by X? and band structure calculations

Valence-band and core-level x-ray photoelectron spectroscopy (XPS) studies of sulfate and bisulfate ions are reported. Sulfate and bisulfate ions cannot be distinguished in their core XPS spectra. The valence band region shows a significant difference in the relative intensity and separation of two prominent peaks, and this difference can be used to distinguish between sulfate and bisulfate because the separation is larger in the case of sulfate (∼4 eV) than for bisulfates (∼3 eV). We show that this difference can be used in a wide range of sulfate and bisulfates, including main group and transition metal compounds: Li2SO4, Na2SO4, K2SO4, MgSO4, Al2(SO4)3, Fe2(SO4)3, FeSO4, Ni2SO4, Ag2SO4, (NH4)2SO4, NaHSO4, KHSO4 and NH4HSO4 (some of these are hydrated). The sulfate and bisulfate spectra can be interpreted by cluster (multiple scattered-wave Xα calculations) and band structure calculations. A careful analysis of the valence band spectra of Li2SO4H2O interpreted by band structure calculation results shows that the water of crystallization can be identified in the valence band region. Copyright © 2000 John Wiley & Sons, Ltd.

ChemInform Abstract: Main Group and Transition Metal Compounds with Silanediolate [R2SiO2]2‐ and α,ω‐Siloxane Diolate [O(R2SiO)n]2‐ Ligands

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.