Reactions of bis[bis(trimethylsilyl)methyl]germylene and the corresponding stannylene with diazidosilanes

The reactions of bis[bis(trimethylsilyl)methyl]-germylene ( 1 ) and the corresponding stannylene ( 2 ) with di-tert-butyldiazidosilane gave N-(azidosilyl)germanimine ( 4 ) and the stannanimine ( 5 ) in quantitative yields. The structures have been confirmed by single-crystal X-ray diffraction. Crystal data for 4 : space group P1 , Z = 2, a = 9.236 (1), b = 12.066 (1), c = 17.068 (1) Å, α = 98.45 (1), β = 90.43, γ = 110.27 (1)°. V = 1761.3 ų, R = 0.051, and Rw = 0.069 based on 4218 reflections with |Fo²| ⩾ 3σ|Fo²|. For 5 : space group P1 , Z = 2, a = 9.183 (1), b = 12.193 (1), c = 17.292 (1) Å, α = 98.74 (1), β = 90.21, γ = 109.96 (1)°, V = 1795.5 ų, R = 0.040, and Rw = 0.051 based on 4795 reflections. The similar reactions of 1 and 2 with 1,3-diazidohexamethyltrisilane ( 16 ) provided azatrisilacyclobutanes quantitatively.     

Asymmetry and magnetism in bis(oximato)-bridged heterobimetallic compounds: a computational approach

A density functional study of exchange coupling was carried out for a series of heterobinuclear oximato-bridged transition metal complexes. Model calculations were used to examine the influence of the electronic configuration of the metal atoms on the coupling constants. This analysis was complemented by a study of the variation of the coupling constant with the most usual structural distortions within this family of compounds. The influence of the nature of the terminal ligands as well as that of the symmetry on the bridge were also investigated.     

A Cyclic (Alkyl)(boryl)germylene Derived from a Cyclic (Alkyl)(amino)germylene

A cyclic (alkyl)(amino)germylene undergoes a ring expansion reaction with dibromomesitylborane (MesBBr₂) to afford a six‐membered dibromogermane derivative. In the presence of Lewis bases (PMe₃ or ^MeNHC), reduction of the latter with two equivalents of potassium graphite (KC₈) gives rise to cyclic (alkyl)(boryl)germylene–Lewis base adducts. Upon heating, the germylene—PMe₃ adduct reacts with H₂ to yield a germane, probably via a base‐free germylene featuring a small HOMO–LUMO gap.     

Expanding the steric coverage offered by bis(amidosilyl) chelates: isolation of low-coordinate N-heterocyclic germylene complexes

The synthesis and coordination chemistry of a series of dianionic bis(amido)silyl and bis(amido)disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr(3)) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate N-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium(IV) dimers of the general form [LGe(μ-S)](2) (L = bis(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete Ge═S double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGe═S units to occur. Notably, the new triarylsilyl groups (4-RC(6)H(4))(3)Si- (R = (t)Bu and (i)Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, -SiPh(3,) and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry.     

Co-ordination compounds of glyoxal bis(dimethylhydrazone)

Complexes derived from glyoxal bis(dimethylhydrazone) (GDMH) have been prepared and characterised; they are of the general types MX₂(GDMH) (M  Co, Zn, Cd; X  Cl, Br and M  Zn, X  SCN) and MX₂(GDMH)₂ (M  Co, Ni; X  SCN). In all the complexes the ligand is chelating;MX₂(GDMH) are tetrahedral monomers while MX₂(GDMH)₂ contain six co-ordinated metal atoms. The ligand is monoprotonated in mineral acids and the salts [GDMH₂][CoBr₄] and [GDMH₂]PdBr₄ have been isolated from acidic solution.     

Synthesis and characterization of bis(dicarboxylato)dimolybdenum(II) compounds

The reaction of tetrakis(μ-acetato)dimolybdenum(II) in aqueous suspension with various dicarboxylic acids yields compounds of the general formula, Mo₂(dicarboxylate)₂·nH₂O. Phthalic acid also gives tri- and tetra-phthalates, and 1,8-naphthalene dicarboxylic acid yields only the tris complex. For malonic and acetylenedicarboxylic acids, only partial substitution occurs. Tetrakis(μ-acetato)dimolybdenum(II) in aqueous suspension also reacts with monocarboxylic acids, and with benzoic acid, Mo₂(benzoate)₄ is obtained. A polymeric structure is suggested for these compounds in the light of their spectral properties.     

Preparation and study of bis(theophyllinato) copper(II) compounds

Bis(theophyllinato) copper(II) dihydrate and its anhydrous form, were prepared. Their thermal, spectral and magnetic behaviours were investigated. Magnetic susceptibility studies show that the dihydrate form can be fitted to the Curie law. The magnetic behaviour of the anhydrous form is interpreted in terms of antiferromangetically exchange-coupled pairs of copper atoms. The change in magnetic properties as the dihydrate is dehydrated implies that structural rearrangement in first coordination sphere of copper accompanies the dehydration process. For bis(theophyllinato)copper(II) dihydrate we propose a pseudo octahedral coordination of copper(II) in a polymeric chain, and for the anhydrous form four-coordination in binuclear units.     

Base-promoted three-component cascade approach to unsymmetrical bis(indolyl)methanes

Here we report a base-catalyzed reaction of two different indoles with aldehydes under heating to produce unsymmetrical bis(indolyl)methanes (BIMs), in which one of the indole ring must be N-substituted. Mixture of EtOH-H₂O is used as solvent. The reaction did not give symmetrical BIMs of N-substituted indoles or N–H indoles. However, traces of latter were formed in few cases, especially when electron-rich aldehydes were used. Diversely substituted indoles and aldehydes were used for the reaction. The reaction proceeds via 3-indolylalcohol, which we confirmed through isolation. The method also gives good yield on multigram scale reaction.     

Preparation of bis(diazo) compounds incorporated into butadiyne and thiophene units, and generation and characterization of bis(carbene) from these compounds

[9-[10-(4-t-Butyl-2,6-dimethyl)phenyl]anthryl](4-bromo-2,6-dimethylphenyl)diazomethane (1-N(2)) was found to be stable enough to survive under Sonogashira and Suzuki coupling reaction conditions, and bis(diazo) compounds incorporated into the 1,4-positions of butadiyne (3-2N(2)) and the 2,5-position of thiophene (4-2N(2)) were prepared. Irradiation of those bis(diazo) compounds generated bis(carbenes), which were characterized by ESR and UV-vis spectroscopic techniques in a matrix at low temperature, as well as time-resolved UV-vis spectroscopy in solution at room temperature. These studies revealed that both of the bis(carbenes), 3 and 4, have a singlet quinoidal diradical ground state with a very small singlet-triplet energy gap of less than 1 kcal/mol. A remarkable increase in the lifetime of bis(carbenes) as opposed to that of monocarbene (1) was noted and was interpreted to indicate that bis(carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout a pi-net framework. Despite the stability, both bis(carbenes) are readily trapped by molecular oxygen to afford bis(ketones) as main products.     

Efficient and versatile single pot approach to dipyrromethanes and bis(heterocyclyl)methanes

An efficient single pot route is presented involving the use of O, N-perhydro 1,3-heterocycles as carbonyl equivalents for the synthesis of 5-substituted dipyrromethanes, 5,10-disubstituted tripyrranes and bis(heterocyclyl)methanes.     

Reactions of (2,3-dimethylenetetramethylene)bis(dipropylborane) with carbonyl compounds

(2,3-Dimethylenetetramethylene)bis(dipropylborane) (1) prepared by borylation of 2,3-dimethylbutadienediyl dipotassium reacts with ketones to form symmetrical diols in a yield of 46–73%. [4+2]-Cycloaddition reactions of diborane1 with 1,2-dicarbonyl compounds proceed highly stereospecifically, affording onlycis-isomers of 4,5-dimethylenecyclohexane1, 2-diols.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 155–159, January, 1993.     

Synthesis, characterization and bromination of bis(phosphinoferrocenyl) gold(I) compounds

Reaction of [(dppf)Au₂Br₂] (3) {dppf = 1,1′-bis(diphenylphosphino)ferrocene} and [(dippf)Au₂Br₂] (4) {dippf = 1,1′-bis(diisopropylphosphino)ferrocene} with excess bromine yields two new complexes [(C₅H₄Br₃)(PR₂)AuBr] (R = Ph, 5; R = i-Pr, 6). Bromination of the free diphosphinoferrocene ligands produces the expected brominated cyclopentenes (C₅H₄Br₃)(PR₂) (R = Ph, 7; R = i-Pr, 8) in good yields; however, these compounds could not be complexed to gold due to reduced basicity of 7 and 8. When the bromination is performed under wet aerobic conditions the oxidized pseudo-centrosymmetric product, [doppf][FeBr₄] (9) {doppf = 1,1′-bis(oxodiphenylphosphino)ferrocene, is formed as the major product. Solid-state structures of 1, 2, 4, 6, and 9 have been established by means of single-crystal X-ray crystallography.