Binding of dinitrogen (N 2 ) to a transition metal center (M) and followed by its activation under milder conditions is no longer impossible; rather, it is routinely studied in laboratories by transition metal complexes. In contrast, binding of N 2 by main group elements has been a challenge for decades, until very recently, an exotic cAAC-borylene (cAAC = cyclic alkyl(amino) carbene) species showed similar binding affinity to kinetically inert and non-polar dinitrogen (N 2 ) gas under ambient conditions. Since then, N 2 binding by short lived borylene species has made a captivating news in different journals for its unusual features and future prospects. Herein, we carried out different types of DFT calculations, including EDA-NOCV analysis of the relevant cAAC-borondinitrogen complexes and their precursors, to shed light on the deeper insight of the bonding secret (EDA-NOCV = energy decomposition analysis coupled with natural orbital for chemical valence). The hidden bonding aspects have been uncovered and are presented in details. Additionally, similar calculations have been carried out in comparison with a selected stable dinitrogen bridged-diiron(I) complex. Singlet cAAC ligand is known to be an exotic stable species which, combined with the B Ar group, produces an intermediate singlet electron-deficient (cAAC)(B Ar) species possessing a high lying HOMO suitable for overlapping with the high lying π*-orbital of N 2 via effective π-backdonation. The B N 2 interaction energy has been compared with that of the Fe N 2 bond. Our thorough bonding analysis might answer the unasked questions of experimental chemists about how boron compounds could mimic the transition metal of dinitrogen binding and activation, uncovering hidden bonding aspects. Importantly, Pauling repulsion energy also plays a crucial role and decides the binding efficiency in terms of intrinsic interaction energy between the boron-center and the N 2 ligand.
Dinitrogen (N2) binding and its activation have been achieved by non-metal compounds like intermediate cAACborylene with the general formula of (cAAC)2(B-Dur)2(N2) [cAAC = cyclic alkyl(amino)carbene; Dur = aryl group, 2,3,5,6-tetramethylphenyl; B-Dur = aryl-borylene].
Dinitrogen (N2) binding and electron transfer reduction of N2 to ammonia (NH3) by the FeMoco cofactor of the nitrogenase enzyme are captivating. They are a part of the textbook for general chemistry. The nature of N2 bonding by reduced FeMoco is speculated based on the experimental evidence. The inorganic core MoFe7S9C1− possesses a Fe6(μ6‐C4−) unit. The mode of N2‐binding at one of the Fe‐centers of the elusive Fe6(μ6‐C4−) unit and the role of light element C4− is intriguing. In the past, the mode of N2‐binding and the kinetics of N2 reduction have been studied by spectroscopic and other tools. Herein, we report on the energy decomposition analysis coupled with natural orbital for chemical valence (EDA‐NOCV) calculations/analyses to shed light on the deeper insight of the N2 binding and especially on the influence of the C‐atom of previously reported Fe‐complexes with an EP3 donor set (E=C, Si). The role of the C‐atom in the iron‐carbon site has been studied by elaboration with deformation electron densities. The intrinsic interaction energy of the bond between Fe and N2 and pairwise orbital interactions between them have been quantitatively estimated. The influence of σ‐donation of three phosphine ligands and their effects on the Fe−N2 bond have been thoroughly studied.
Stabilizing the exotic chemical species possessing multiple bonds is often extremely challenging due to insufficient orbital overlap, especially involving one heavier element. Bulky aryl groups and/or carbene as ligand have previously stabilized the SiSi, GeGe, and BB triple bonds. Herein, theoretical calculations have been carried out to shed light on the stability and bonding of elusive silaboryne/germaboryne (Si/GeB triple bond) stabilized by donor base ligands ((cAAC)BE(Me)(L); E = Si, L = cAACMe, NHCMe, PMe3; E = Ge, L = cAACMe). The heavier analogues (Sn, Pb) have been further studied for comparison. Additionally, the effects of bulky substituents at the Si and N atoms on the structural parameters and stability of those species have been investigated. Energy decomposition analysis coupled with natural orbital for chemical valence (EDA‐NOCV; for Si) showed that cAAC/NHC ligands could stabilize the exotic BSi‐Me species more efficiently than PMe3 ligands. The BSi partial triple bond of the corresponding species possesses a mixture of one covalent electron sharing BSi σ‐bond and two dative π‐bonds (B ← Si, B → Si).
An electronic instrument bitscd on optical transmission toFor coagulation time, frcsh blood samples are collected from subjects by vcncpuncture. The chamber was filled upto a hcight of 17mm. The variation in the TI was directly used for measure' thc hcm:itologic:il p:ir:imcterscoagulntioii time, nicasnrcmcnt of coagulation time and the results ucre hcmatocrit and erythrocyte packing indcs of hc:rlthy and diseased sampler is dcvcloped.For hematocrit meiisurenient, thc instrument is calibrated by blood silnlplcs of different hematocrits, as measured by Wintrohe method. The coagulation time and hematocrit as measured by the TI variation show good agreement with that measured by capillary mcthod and Wintrobe technique, respectively. The erythrocyte packing index provides valuilble data on aggrcgation process of erythrocytes.
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