Functionalization of P4 Using a Lewis Acid Stabilized Bicyclo[1.1.0]tetraphosphabutane Anion

Reacting white phosphorus (P₄) with sterically encumbered aryl lithium reagents (aryl=2,6‐dimesitylphenyl or 2,4,6‐tBu₃C₆H₂) and B(C₆F₅)₃ gives the unique, isolable Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutane anion. Subsequent alkylation of the nucleophilic site of the RP₄ anion gives access to non‐symmetrical disubstituted bicyclic tetraphosphorus compounds. This novel method enables P? C bond formation in a controlled fashion using white phosphorus as starting material.     

Effect of alkali metal coordination on gas-phase chemistry of the diphosphate ion: the MH(2)P(2)O(7) (-) ions

Systematic experimental and theoretical studies on anionic phosphate species in the gas phase are almost nonexistent, even though they could provide a benchmark for enhanced comprehension of their liquid-phase chemical behavior. Gaseous MH(2)P(2)O(7) (-) ions (M=Li, Na, K, Rb, Cs), obtained from electrospray ionization of solutions containing H(4)P(2)O(7) and MOH or M salts as a source of M(+) ions were structurally assayed by collisionally activated dissociation (CAD) mass spectrometry and theoretical calculations at the B3LYP/6-31+G* level of theory. The joint application of mass spectrometric techniques and theoretical methods allowed the MH(2)P(2)O(7) (-) ions to be identified as having a structure in which the linear diphosphate anion is coordinated to the M(+) ion (I) and provides information on gas-phase isomerization processes in the [PO(3)...MH(2)PO(4)](-) clusters II and the [P(2)O(6)...M...H(2)O](-) clusters IV. Studies of gas-phase reactivity by Fourier transform ion cyclotron resonance (FTICR) and triple quadrupole (TQ) mass spectrometry revealed that the MH(2)P(2)O(7) (-) ions react with selected nucleophiles by clustering, proton transfer and addition-elimination mechanisms. The influence of the coordination of alkali metal ions on the chemical behavior of pyrophosphate is discussed.     

Gas-phase chemistry of diphosphate anions as a tool to investigate the intrinsic requirements of phosphate ester enzymatic reactions: the [M1M2HP2O7]- ions

Experimental studies on gaseous inorganic phosphate ions are practically nonexistent, yet they can prove helpful for a better understanding of the mechanisms of phosphate ester enzymatic processes. The present contribution extends our previous investigations on the gas-phase ion chemistry of diphosphate species to the [M(1)M(2)HP(2)O(7)](-) ions where M(1) and M(2) are the same or different and correspond to the Li, Na, K, Cs, and Rb cations. The diphosphate ions are formed by electrospray ionization of 10(-4) M solutions of Na(5)P(3)O(10) in CH(3)CN/H(2)O (1/1) and MOH bases or M salts as a source of M(+) cations. The joint application of mass spectrometric techniques and quantum-mechanical calculations makes it possible to characterize the gaseous [M(1)M(2)HP(2)O(7)](-) ions as a mixed ionic population formed by two isomeric species: linear diphosphate anion coordinated to two M(+) cations (group I) and [PO(3)M(1)M(2)HPO(4)](-) clusters (group II). The relative gas-phase stabilities and activation barriers for the isomerization I-->II, which depend on the nature of the M(+) cations, highlight the electronic susceptibility of P-O-P bond breaking in the active site of enzymes. The previously unexplored gas-phase reactivity of [M(1)M(2)HP(2)O(7)](-) ions towards alcohols of different acidity was investigated by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). The reaction proceeds by addition of the alcohol molecule followed by elimination of a water molecule.     

2-Bromophospholide ions: synthesis and theoretical study

DFT calculations at the B3 LYP/6-311++G(3df,2p) level indicate that the 2-bromophospholide ion could be stable toward self-arylation as a result of the lowered nucleophilicity of the in-plane phosphorus lone pair (the corresponding sigma(P) orbital is lowered by 0.7 eV compared with the corresponding orbital of the parent phospholide ion, and the negative charge at P is reduced from -0.435 to -0.369 e). Accordingly, the synthesis of 2-bromo-3,4-dimethylphospholide was successfully carried out by quantitative base-induced dealkylation of 2-bromo-1-(2-ethoxycarbonylethyl)-3,4-dimethylphosphole. This ion reacts with FeCl2 to give the corresponding 2,2'-dibromo-3,3',4,4'-tetramethyl-1,1'-diphosphaferrocene as a poorly stable mixture of meso- and rac-diastereomers in 18% yield.     

Unexpected structural diversity in alkali metal azide-crown ether complexes: syntheses, X-ray structures, and quantum-chemical calculations

A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N3)], [Na([15]crown-5)(N3)], [Na([15]crown-5)(H2O)2]N3, [K([18]crown-6)(N3)(H2O)], [Rb([18]crown-6)(N3)(H2O)], [Cs([18]crown-6)(N3)]2, and [Cs([18]crown-6)(N3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the M-N(terminal) metal-azide bond length and charge densities on the metal (M) and terminal nitrogen centre (N(terminal)) in these complexes has allowed the nature of the metal-azide bond to be probed in each case. The bonding in these complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre and minimising ligand-ligand repulsions. The structures of the crown ether complexes determined in this work show the subtle interplay of such factors. The significant role of hydrogen bonding is also demonstrated, most clearly in the structures of the K and Rb dimers, but also in the chain structure of the hydrated Cs complex.     

ChemInform Abstract: Bonding,Structure, and Stability of Ternary Hydrides A2MH2 (A: Li,Na; M: Pd,Pt).

ChemInform 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.     

LaNiO2: Synthesis and structural characterization

The preparation of a single phase LaNiO₂ by controlled H₂ reduction of the perovskite LaNiO₃ is reported. The different steps of the synthesis are detailed. The structural characterization is made by X-ray diffraction (XRD) and neutron powder diffraction (NPD) and discussed; the derived crystal structure is the infinite-layer CaCuO₂. Both XRD and NPD patterns are characterized by anisotropic shape broadening originating from size effect linked to the reduction process. From NPD, the LaNiO₂ powder is composed of platelet-like crystallites having an average thickness equal to 20 nm along the [001] direction. A modulation of the neutron diffraction background is observed and discussed in connection to the reduction process.     

Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N‐(2‐Pyridylethyl)‐N′‐(2,6‐diisopropylphenyl)pivalamidine

N‐(2,6‐Diisopropylphenyl)‐N′‐(2‐pyridylethyl)pivalamidine (Dipp‐N=C(tBu)‐N(H)‐C₂H₄‐Py) ( 1 ), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}] ( 6 ), [Mg{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}₂] ( 3 ), and heteroleptic [{(Me₃Si)₂N}Ae{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}], with Ae being Ca ( 2 a ) and Sr ( 2 b ). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β‐metalation and an immediate deamidation reaction yielding [(thf)₂Na{Dipp‐N=C(tBu)‐N(H)}] ( 4 a ) or [(thf)₂K{Dipp‐N=C(tBu)‐N(H)}] ( 4 b ), respectively, as well as 2‐vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI₂ in tetrahydrofuran yields N‐(2,6‐diisopropylphenyl)pivalamidine (Dipp‐N=C(tBu)‐NH₂) ( 5 ), or [(thf)₄Ca{Dipp‐N=C(tBu)‐N(H)}₂] ( 7 ), respectively. The reaction of AN(SiMe₃)₂ (A=Na, K) with less bulky formamidine Dipp‐N=C(H)‐N(H)‐C₂H₄‐Py ( 8 ) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 a ) or [(thf)K{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 b ), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β‐metalation/deamidation of N‐(2‐pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single‐crystal X‐ray structure analysis and are maintained in solution.     

Synthetic, structural, and theoretical investigations of alkali metal germanium hydrides--contact molecules and separated ions

The preparation of a series of crown ether ligated alkali metal (M=K, Rb, Cs) germyl derivatives M(crown ether)_nGeH₃ through the hydrolysis of the respective tris(trimethylsilyl)germanides is reported. Depending on the alkali metal and the crown ether diameter, the hydrides display either contact molecules or separated ions in the solid state, providing a unique structural insight into the geometry of the obscure GeH₃^? ion. Germyl derivatives displaying M? Ge bonds in the solid state are of the general formula [M([18]crown‐6)(thf)GeH₃] with M=K ( 1 ) and M=Rb ( 4 ). The compounds display an unexpected geometry with two of the GeH₃ hydrogen atoms closely approaching the metal center, resulting in a partially inverted structure. Interestingly, the lone pair at germanium is not pointed towards the alkali metal, rather two of the three hydrides are approaching the alkali metal center to display M? H interactions. Separated ions display alkali metal cations bound to two crown ethers in a sandwich‐type arrangement and non‐coordinated GeH₃^? ions to afford complexes of the type [M(crown ether)₂][GeH₃] with M=K, crown ether=[15]crown‐5 ( 2 ); M=K, crown ether=[12]crown‐4 ( 3 ); and M=Cs, crown ether=[18]crown‐6 ( 5 ). The highly reactive germyl derivatives were characterized by using X‐ray crystallography, ¹H and ¹³C NMR, and IR spectroscopy. Density functional theory (DFT) and second‐order Møller–Plesset perturbation theory (MP2) calculations were performed to analyze the geometry of the GeH₃^? ion in the contact molecules 1 and 4 .     

Cathode generation of thiolate anions and the correlation between their oxidationE 1/2 and nucleophilic reactivity

Cathode reduction of a series of aliphatic, aromatic, and heteroaromatic thiols on a rotating disk Pt electrode in abs. MeCN against the background of 0.1N Bu₄NClO₄ was investigated. It was found that this process results in the formation of the corresponding thiolate anions whose oxidation half-wave potentials are linearly correlated with their nucleophilicity in theS _N 2 reaction.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2539–2544, November, 1992.     

Exploring the Anion–Cation Interaction in m‐Terphenyltetrafluorosilicates by Using Multinuclear NMR Spectroscopy,X‐ray Diffraction,and ICR‐FT‐MS

The synthesis of a series of m‐terphenyl‐substituted tetrafluorosilicates with different cations (Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Tl⁺) is described and the interactions between the anion and cation are investigated in the solid, solution, and gas states by using multinuclear NMR spectroscopy, X‐ray diffraction, and ion cyclotron resonance Fourier‐transform mass spectrometry (ICR‐FT‐MS). In solution, heteronuclear NMR spectroscopy parameters show only limited sensitivity to the nature of the cation, which furthermore can be affected by solvent effects. More pronounced effects are observed in the structural data obtained from X‐ray diffraction studies, which are in good agreement with experimental gas‐phase data from ESIMS. ESIMS also reveals the existence of dimeric species of the type [M(DmpSiF₄)₂]^? (Dmp=2,6‐dimesitylphenyl), the stability of which was determined by normalized collision energy experiments.     

Stability and Conversion of Tin Zintl Anions in Liquid Ammonia Investigated by NMR Spectroscopy

Homoatomic polyanions of post‐transition main‐group metals, namely, Zintl anions, are precast in analogous Zintl phases and can react in solution to form new materials. Despite comprehensible reaction approaches, the formed products cannot be planned in advance, as hitherto undetected and therefore disregarded side reactions take place. The outcomes and interpretations of the reactions of Zintl anions are so far based mainly on crystal structures, which only allow characterization of the product that has the lowest solubility. Here we present the results of our investigation of the stability of highly charged tin Zintl anions in liquid ammonia, which is not exclusively based on solution effects but also on the oxidative influence of the solvent. This allows for a deeper understanding of the ongoing processes in solution and opens doors to the directed synthesis of transition metal complexes of Sn₄^4?, here shown by its reactivity towards MesCu.     

ChemInform Abstract: Na14K6Tl18M (M: Mg,Zn, Cd,Hg) and Na13.5Sm0.5K6Tl18Na: Novel Phases of Mg2Zn11-Type Structure with Octahedral and Centered Icosahedral Clusters.

ChemInform 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.     

Developing a Hetero‐Alkali‐Metal Chemistry of 2,2,6,6‐Tetramethylpiperidide (TMP): Stoichiometric and Structural Diversity within a Series of Lithium/Sodium,Lithium/Potassium and Sodium/Potassium TMP Compounds

Studied extensively in solution and in the solid state, Li(TMP) (TMP=2,2,6,6‐tetramethylpiperidide) is an important utility reagent popular as a strongly basic, weakly nucleophilic tool for C? H metallation. Recently, there has been a surge in interest in mixed metal derivatives containing the bulky TMP anion. Herein, we start to develop hetero (alkali metal) TMP chemistry by reporting the N,N,N′,N′‐tetramethylethylenediamine (TMEDA)‐hemisolvated sodium–lithium cycloheterodimer [(tmeda)Na(μ‐tmp)₂Li], and its TMEDA‐free variant [{Na(μ‐tmp)Li(μ‐tmp)}_∞], which provides a rare example of a crystallographically authenticated polymeric alkali metal amide. Experimental observations suggest that the former is a kinetic intermediate en route to the latter thermodynamic product. Furthermore, a third modification, the mixed potassium–lithium‐rich cycloheterotrimer [(tmeda)K(μ‐tmp)Li(μ‐tmp)Li(μ‐tmp)], has also been synthesised and crystallographically characterised. On moving to the bulkier tridentate donor N,N,N′,N′′,N′′‐pentamethyldiethylenediamine (PMDETA), the additional ligation forces the sodium–lithium and potassium–dilithium ring species to open giving the acyclic arc‐shaped complexes [(pmdeta)Na(μ‐tmp)Li(tmp)] and [(pmdeta)K(μ‐tmp)Li(μ‐tmp)Li(tmp)], respectively. Completing the series, the potassium–lithium and potassium–sodium derivatives [(pmdeta)K(μ‐tmp)₂M] (M=Li, Na) have also been isolated as closed structures with a distinctly asymmetric central MN₂K ring. Collectively, these seven new bimetallic compounds display five distinct structural motifs, four of which have never hitherto been witnessed in TMP chemistry and three of which are unprecedented in the vast structural library of alkali metal amide chemistry.