Synthesis and thermal chemistry of copper (I) guanidinates

Copper (I) guanidinate dimers were generated by a salt metathesis route and structurally characterized. The guanidinates differed from the known amidinate dimers because of a large torsion of the dimer ring. This had a direct effect on their thermal chemistry. The thermal reactivity was investigated by several methods, including a novel temperature-resolved, gas-phase method that was monitored by mass spectrometry. The copper guanidinates underwent carbodiimide deinsertion to produce copper metal at temperatures between 225 -and 250 degrees C in the gas phase and at 125 degrees C in solution. The amidinate investigated also showed copper deposition at 190 degrees C in the gas phase, and 135 degrees C in solution, but without carbodiimide deinsertion. The guanidinate compounds deposited crystalline copper at 225 degrees C in a simple chemical vapor deposition experiment.     

Pyrrole Denitrogenation and Fragmentation of Tetramethylethylenediamine Promoted by a NbII Cluster

A nitrogen center was abstracted from a pyrrolyl ring to form the dinuclear nitrido- and dienyl-bridged complex 1 during the reaction of [{(tmeda)Nb^IICl}₂(μ-Cl)₃Li(tmeda)] with the lithium salt of 2,5-dimethylpyrrole (tmeda=N,N,N′,N′-tetramethylethylenediamine). A second product from this reaction is the amido-carbene-hydride niobium complex 2 , which likewise forms under C−N bond cleavage.     

Synthesis and Structure of a Chromium(III) Complex Supported by a β-diketiminate and an Enediolate Ligand

Abstract  

The complex (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(9,10-dihydro-9,10-(ethenediolato)anthracene)(tetrahydrofuran)chromium(III) (1) has been synthesized and structurally characterized. Complex 1 crystallizes in the spacegroup Cc with the crystal cell parameters a = 22.285 (3) ?, b = 9.3317 (13) ?, c = 40.782 (6) ?, β = 99.338 (3)°, V = 8369 (2) ?³, and Z = 8. Two symmetry unique complex molecules were located in the asymmetric unit making Z′ = 2. The chromium atoms display square pyramidal coordination with THF located in the axial position. The previously neutral α-diketone moiety has been reduced by two electrons to an enediolate group with a corresponding increase of oxidation state of the chromium center.     

Synthesis of zinc, copper, nickel, cobalt, and iron complexes using tris(pyrazolyl)methane sulfonate ligands: a structural model for N,N,O binding in metalloenzymes

Ligands of intermediate steric bulk were designed to mimic metalloenzymes with histidine and carboxlyate binding sites. The reaction between tris(3-isopropylpyrazolyl)methane and butyllithium followed by SO3NMe3 in THF yielded the new ligand lithium tris(3-isopropylpyrazolyl)methane sulfonate (LiTpmsiPr). Various metal salts reacted with LiTpmsiPr to give the octahedral complexes M(TpmsiPr)2 (M = Zn, Cu, Ni, Co, Fe) in which each ligand has N,N,O binding to the metal. In the reaction between LiTpmsiPr and ZnCl2, in addition to the major product Zn(TpmsiPr)2, [LiTpmsiPrZnCl2].2THF was also formed as a minor product with a tetrahedral zinc atom coordinated to either N,N,Cl,Cl in the solid phase or N,N,N,Cl in acetonitrile solution. Although TpmsiPr is coordinatively flexible and can act as a bipodal or tripodal ligand, it appears to favor the formation of octahedral L2M complexes.     

Phenylamido and Diphenylamido Complexes of Chromium(II)

Abstract  Addition LiNHPh to a [(NacNac)Cr(μ-I)]₂ [NacNac = 2,4 pentane-N-N′-bis(2,6-diisopropylphenyl) ketiminato] in THF yields a dimeric anilido complex, 1, that crystallizes in P2₁/n with unit cell parameters a = 13.390(2) ?, b = 26.298(5) ?, c = 21.326(4) ?, β = 93.905(4)°, V = 7492(2) ?³ and Z = 4. The same reaction in the presence of aniline yields a monomeric anilido complex, 2, with a coordinated aniline molecule. Complex 2 crystallizes in P2 ₁ /c with unit cell parameters a = 28.530(5) ?, b = 10.8116(18) ?, c = 26.492(5) ?, β = 115.685(3)°, V = 7364(2) ?³ and Z = 8. Addition of aniline to isolated 1 yields 2. Addition of LiNPh₂ to [(NacNac)Cr(μ-I)]₂ in THF yields a monomeric complex that crystallizes in P2₁/n with the unit cell parameters a = 11.152(6) ?, b = 23.820(12) ?, c = 17.915(9) ?, β = 106.223(9)°, V = 4569(4) ?³ and Z = 4. All complexes have been spectroscopically and structurally characterized. Graphical Abstract  Addition of LiNHPh or LiNPh₂ to [(NacNac)Cr(μ-I)]₂ yields a dimeric or a monomeric complex whereas addition of LiNHPh in the presence of aniline yields the monomeric anilido complex.      

Synthesis and Structure of Chromium(II) Complexes Supported by Both a β-Diketiminate and an Amidinate Ligand

Abstract  

The complexes (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(μ₂-diisopropylacetamidinato) chromium(II) (1) and (bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato)(μ₂-dicyclohexylacetamidinato) chromium(II) (2) have been synthesized and structurally characterized. Complex 1 crystallizes in space group Pbcn with crystal cell parameters a = 10.7183(13) ?, b = 16.4093(19) ?, c = 20.687(2) ?, V = 3,638.3(7) ?³ and Z = 4. Complex 2 crystallizes in triclinic space group P-1 with crystal cell parameters a = 10.750(3) ?, b = 12.174(3) ?, c = 16.308(4) ?, α = 75.903(4)°, β = 82.137(4)°, γ = 85.511(4), V = 2,048.4(8) ?³ and Z = 2. The complexes adopt a spiro distorted square planar geometry and have similar structural parameters.     

The regioselective switch for amino-NHC mediated C-H activation of benzimidazole via Ni-Al synergistic catalysis

We have disclosed a new mode of a chemically regioselective switch for C-H bond functionalization of benzimidazole derivatives via a cooperative effect invoked by Ni-Al bimetallic catalysis to create a steric requirement for obtaining the linear product of styrene insertion. Yet, excluding the AlMe(3) cocatalyst switches the reaction toward branch selectivity.     

Consensus QSAR model for identifying novel H5N1 inhibitors

Due to the importance of neuraminidase in the pathogenesis of influenza virus infection, it has been regarded as the most important drug target for the treatment of influenza. Resistance to currently available drugs and new findings related to structure of the protein requires novel neuraminidase 1 (N1) inhibitors. In this study, a consensus QSAR model with defined applicability domain (AD) was developed using published N1 inhibitors. The consensus model was validated using an external validation set. The model achieved high sensitivity, specificity, and overall accuracy along with low false positive rate (FPR) and false discovery rate (FDR). The performance of model on the external validation set and training set were comparable, thus it was unlikely to be overfitted. The low FPR and low FDR will increase its accuracy in screening large chemical libraries. Screening of ZINC library resulted in 64,772 compounds as probable N1 inhibitors, while 173,674 compounds were defined to be outside the AD of the consensus model. The advantage of the current model is that it was developed using a large and diverse dataset and has a defined AD which prevents its use on compounds that it is not capable of predicting. The consensus model developed in this study is made available via the free software, PaDEL-DDPredictor.     

QSAR classification of metabolic activation of chemicals into covalently reactive species

Metabolic activation of chemicals into covalently reactive species might lead to toxicological consequences such as tissue necrosis, carcinogenicity, teratogenicity, or immune-mediated toxicities. Early prediction of this undesirable outcome can help in selecting candidates with increased chance of success, thus, reducing attrition at all stages of drug development. The ensemble modelling of mixed features was used for the development of a model to classify the metabolic activation of chemicals into covalently reactive species. The effects of the quality of base classifiers and performance measure for sorting were examined. An ensemble model of 13 naive Bayes classifiers was built from a diverse set of 1,479 compounds. The ensemble model was validated internally with five-fold cross validation and it has achieved sensitivity of 67.4% and specificity of 93.4% when tested on the training set. The final ensemble model was made available for public use.