Effect of a single methyl substituent on the electronic structure of cobaltocene studied by computationally assisted MATI spectroscopy.

Metallocenes represent archetypical organometallic compounds playing key roles in various fields of fundamental and applied chemistry. Many of their unique properties arise from low ionization energies (IE) which can be tuned by introducing substituents into the rings. Here we report the first mass-analyzed threshold ionization (MATI) spectrum of a methylmetallocene, (Cp')(Cp)Co (Cp' = η-CHMe, Cp = η-CH).

An investigation into the Brønsted acidity of the perfluorinated alkoxy silanes {(FC)CO}SiH and {(FC)CO}Si(Cl)H.

The perfluorinated alkoxy silanes {(FC)CO}SiH (1) and {(FC)CO}Si(Cl)H (2) were prepared and fully characterized. Despite the high calculated Brønsted acidities, all attempts to deprotonate 1 and 2 to give the conjugate silanide ions failed due to the exceptionally short and strong Si-H bonds. In the solid state, the Si-H units are not involved in any intermolecular interactions, but instead the crystal packing consists of exceptionally short and strong F⋯F interactions.

Praseodymium Metallacrown-Based NMR Probe for Enantioselective Discrimination of Mandelate Anions in Water.

Recently, the enhanced interest in water-soluble aminohydroximate Ln(III)-Cu(II) metallacrowns (MC) is largely due to their fascinating structural chemistry, diverse properties and ease of synthesis. We examined the water-soluble praseodymium(III) alaninehydroximate complex Pr(HO)[15-MC-5]·3Cl () as a highly effective chiral lanthanide shift reagent for NMR analysis of the biologically relevant (R/S)-mandelate (MA) anions in aqueous media. The R-MA and S-MA enantiomers can be easily discriminated in the presence of small (1.

The reactivity of antimony and bismuth ,,-pincer compounds toward K[BEtH] - the formation of heterocyclic compounds . element-element bonds stable terminal Sb-H bonds.

The oxidative addition of CFSOCHSi(CH) (NpOTf) toward organopnictogen(I) ,,-pincer compounds, [2,6-(DippNCH)CH]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPrCH) produced compounds [2,6-(DippNCH)CH]E(Np)(OTf) (2-E, where E = Sb, Bi). By analogy, the reduction of [2,6-(MeNCH)CH]ECl (3-E, where E = Sb, Bi) followed by treatment with NpOTf or MeI gave compounds [2,6-(MeNCH)CH]E(R)(X) (R/X = Np/OTf 4-E, where E = Sb, Bi; R/X = Me/I 5-Sb). The reactivity of these compounds toward 1 eq.

Beyond simple hetero Diels-Alder cycloadditions. A new type of element-ligand cooperativity at N,C,N-coordinated arsinidene and stibinidene centres in the reaction with an electron-deficient alkyne.

The reactivity of two types of organopnictogen(I) N,C,N-pincer ligand coordinated compound, [2,6-(DippNCH)CH]E (1-E, where E = As, Sb, Bi; Dipp = 2,6-iPrCH) and [2-(DippNCH)-6-(DippNHCH)CH]E (6-E, where E = As or Sb), toward an electron-deficient alkyne, dimethyl acetylenedicarboxylate (DMAD), is reported. All reactions represent remarkable examples of element-ligand cooperation (ELC). In the first step, all compounds react dearomatization of a latent heteropnictole ring producing rare examples of hetero Diels-Alder (DA) adducts.

Magnetically induced ring currents in metallocenothiaporphyrins.

The magnetically induced current-density susceptibility tensor (CDT) of the lowest singlet and triplet states of the metallocenothiaporphyrins, where the metal is V, Cr, Mn, Fe, Co, Ni, Mo, Tc, Ru, or Rh, have been studied with the gauge-including magnetically induced currents (GIMIC) method. The compounds containing V, Mn, Co, Tc or Rh were studied as cations because the neutral molecules have an odd number of electrons. The calculations show that the aromatic nature of most of the studied molecules follows the Hückel and Baird rules of aromaticity.

Perfluorinated Trialkoxysilanol with Dramatically Increased Brønsted Acidity.

The Brønsted acidity of the perfluorinated trialkoxysilanol {(F C) CO} SiOH is more than 13 orders of magnitude higher than that of orthosilicic acid, Si(OH) , and even more for most previously known silanols. It is easily deprotonated by simple amines and pyridines to give the conjugate silanolates [OSi{OC(CF ) } ] , which possess extremely short Si-O bonds, comparable to those of silanones.

Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane.

The aryltellurenyl cation [2-(tBuNCH)C H Te] , a Lewis super acid, and the weakly coordinating carborane anion [CB H ] , an extremely weak Brønsted acid (pK =131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C H Te][CB H ], in which the Brønsted acidity (pK 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude.

Water-Soluble Bismuth(III) Polynuclear Tyrosinehydroximate Metallamacrocyclic Complex: Structural Parallels to Lanthanide Metallacrowns.

Recently there has been a great deal of interest and associated research into aspects of the coordination chemistry of lanthanides and bismuth-elements that show intriguing common features. This work focuses on the synthesis and characterization of a novel bismuth(III) polynuclear metallamacrocyclic complex derived from aminohydroxamic acid, in order to compare the coordination ability of Bi with the similarly sized La ions. A polynuclear tyrosinehydroximate Bi(OH)[15-MC-5](NO) () was obtained according to the synthetic routes previously described for water-soluble Ln(III)-Cu(II) 15-MC-5 metallacrowns.

Substituent effects on the electronic structures of sandwich compounds: new understandings provided by DFT-assisted laser ionization spectroscopy of bisarene complexes.

Recent advances on substituent effects in transition metal bisarene complexes studied with high-resolution threshold ionization spectroscopy are reviewed to demonstrate new aspects of the ligand influence on electronic structures of sandwich molecules. Unprecedented accuracy in the determination of ionization energies provided by the laser techniques makes it possible to reveal and describe quantitatively such fine phenomena as isotope effects, the mutual substituent influence or variations of substituent effects on replacing the central metal atom with its Group analogues. In combination with DFT calculations, laser ionization spectroscopy unveils mechanisms of the ligand influence on unique redox properties of sandwich complexes which are of key importance for their practical use.

Reversible C=C Bond Activation by an Intramolecularly Coordinated Antimony(I) Compound.

The reaction of N,C,N-chelated stibinidene ArSb (1) (Ar=C H -2,6-(CH=NtBu) ) with selected N-alkyl/aryl-maleimides RN(C(O)CH) (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring.

The first water-soluble polynuclear metallamacrocyclic Sr(ii)-Cu(ii) complex based on simple glycinehydroximate ligands.

Recently, aminohydroximate ligands have found wide applications in the fascinating class of polynuclear metallamacrocyclic compounds named 15-MC-5 metallacrowns. The enhanced interest in water-soluble aminohydroximate Ln(iii)-Cu(ii) complexes is largely due to their rich coordination chemistry, diverse properties and ease of synthesis. We examined glycinehydroxamic acid as a simple ligand for the preparation of the first water-soluble polynuclear metallamacrocyclic Sr(ii)-Cu(ii) compound.

Rydberg state mediated multiphoton ionization of (η-CH)(η-CH)Cr: DFT-supported experimental insights into the molecular and electronic structures of excited sandwich complexes.

The resonance-enhanced multiphoton ionization (REMPI) of a mixed sandwich complex has been achieved for the first time when exciting (η7-C7H7)(η5-C5H5)Cr via the Rydberg 4pz state. The REMPI spectrum is indicative of unexpectedly small changes of the sandwich geometry on excitation. Time-dependent DFT calculations reveal fine effects of the ligand nature on the molecular and electronic structure variations accompanying electronic excitation.

From a 2,1-Benzazaarsole to Elusive 1-Arsanaphthalenes in One Step.

The 2,1-benzazaarsole (1) showed a diene-like reactivity towards selected alkynes RC≡CR (R=CO Me, C F N) thus forming 1-arsa-1,4-dihydro-iminonaphthalenes 2 a and 3 a as hardly isolable intermediates, that underwent facile CH→NH proton migration leading to before elusive substituted 1-arsanaphthalenes 2 b and 3 b that could be completely structurally characterized.

The Weakly Coordinating Tris(trichlorosilyl)silyl Anion.

Closely following the procedure for the preparation of the base-stabilized dichlorosilylene complex NHC ⋅SiCl reported by Roesky, Stalke, and co-workers (Angew. Chem. Int.

Facile activation of alkynes with a boraguanidinato-stabilized germylene: a combined experimental and theoretical study.

A boraguanidinato-stabilized germylene, [(i-Pr)NB(N-2,6-MeCH)]Ge, reacts with alkynes RC[triple bond, length as m-dash]CR selectively in a 2 : 1 molar ratio to afford 3,4-R,R'-1,2-digermacyclobut-3-enes 1a-e as the products of formal [2 + 2 + 2] cyclization [R/R' = Me/Me (1a), Ph/Ph (1b), Ph/H (1c), t-Bu/H (1d) and Cy/H (1e)]. Ferrocenyl-substituted alkynes react similarly, yielding the corresponding ferrocenylated 3,4-R,R'-1,2-digermacyclobut-3-enes 2a-d [where R/R' = Fc/H (2a), Fc/Me (2b), Fc/Ph (2c), and Fc/Fc (2d); Fc = ferrocenyl]. By contrast, only one of the triple bonds available in conjugated diynes RC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CR is activated with the germylene, while the second one remains intact even in the presence of an excess of the germylene.

DFT-Supported Threshold Ionization Study of Chromium Biphenyl Complexes: Unveiling the Mechanisms of Substituent Influence on Redox Properties of Sandwich Compounds.

High-resolution mass-analyzed threshold ionization (MATI) spectra of (η -Ph ) Cr and (η -Ph )(η -PhMe)Cr demonstrate that the Ph groups work as electron donors, decreasing the ionization energy of the gas-phase bisarene complexes. In contrast to electrochemical data, a close similarity of the Ph and Me group effects on the oxidation of free sandwich molecules has been revealed. However, DFT calculations testify for the opposite shifts of the electron density caused by the Me and Ph substituents in the neutral complexes, the latter behaving as an electron-accepting fragment.

Germylenes and stannylenes stabilized within N2PE rings (E = Ge or Sn): combined experimental and theoretical study.

The deprotonation of aminophosphanes PhP(NHR)2 (R = t-Bu or Dip; Dip = 2,6-i-Pr2C6H3) and t-BuP(NHDip)2 using n-BuLi gave, depending on the stoichiometry, both the dilithium compounds {[PhP(Nt-Bu)2]Li2}2 (), [PhP(Nt-Bu)(NDip)]Li2·(Et2O) (), [t-BuP(NDip)2]Li2·(Et2O)2 () and [t-BuP(NDip)2]Li2·(tmeda)2 (), and the monolithium compounds [PhP(NHt-Bu)(NR)]Li·(tmeda) (R = t-Bu , Dip ) and [t-BuP(NHDip)(NDip)]Li·(tmeda) (). Treatment of , and with GeCl2·dioxane or SnCl2 in a 1 : 1 stoichiometric ratio gave the corresponding tetrylenes [PhP(Nt-Bu)2]E (E = Ge , Sn ), [PhP(Nt-Bu)(NDip)]Ge () and [t-BuP(NDip)2]E (E = Ge , Sn ). The heteroleptic germylene [Ph(H)P(Nt-Bu)2]GeCl () was obtained by the reaction of the monolithium compound [PhP(NHt-Bu)(Nt-Bu)]Li·(tmeda) () with GeCl2·dioxane in a 1 : 1 stoichiometric ratio, as a result of a spontaneous NH → PH tautomeric shift in the ligand backbone.

Samarocene oxide: from an undesired decomposition product to a new reagent.

Samarocene oxide [Cp*2Sm-O-SmCp*2] is mostly considered as an undesired decomposition product of the well-established but highly air-sensitive samarocene, [Cp*2Sm(thf)2]. [Cp*2Sm-O-SmCp*2] is often formed by accidental exposure of [Cp*2Sm(thf)2] to air or wet solvents. We show here that [Cp*2Sm-O-SmCp*2] acts as a mild oxide base and thus is a valuable synthetic equivalent for "O(2-)".

Electronic excited states of chromium and vanadium bisarene complexes revisited: interpretation of the absorption spectra on the basis of TD DFT calculations.

The nature and energies of the (arene)2Cr, (arene)2V and (arene)2Cr(+) (arene = η(6)-C6H6, η(6)-C6H5Me, η(6)-1,3-C6H4Me2, and η(6)-1,3,5-C6H3Me3) electronic excited states have been determined on the basis of the time-dependent density functional theory (TD DFT) approach and comparison with the gas-phase and condensed-phase absorption spectra. Both valence-shell and Rydberg electronic excitations were taken into account. The TD DFT results appear to describe correctly the influence of the metal atom and the ligand on the band positions and intensities in the UV-visible absorption spectra as well as the mixing of Rydberg and intravalency states.

Anhydrous mono- and dinuclear tris(quinolinolate) complexes of scandium: the missing structures of rare earth metal 8-quinolinolates.

The first monomeric anhydrous scandium tris(8-quinolinolate) complex 1 with the 2-amino-8-quinolinolate ligands and the Sc(2)Q(6) dinuclear complex 2 with the unsubstituted 8-quinolinolate ligands have been synthesized and characterized by X-ray analysis and DFT calculations. The intramolecular hydrogen bonds appear to be responsible for the unique monomeric structure of complex 1. The DFT-based analysis of the electron density topology reveals the (3,-1) critical points corresponding to the O···H and N···H bonds.