The aim of this work is to convince practitioners of (31)P NMR methods to regard simple GIAO quantum chemical calculations as a safe tool in structural analysis of organophosphorus compounds. A comparative analysis of calculated GIAO versus experimental (31)P NMR chemical shifts (CSs) for a wide range of phosphorus containing model compounds was carried out. A variety of combinations (at the HF, DFT (B3LYP and PBE1PBE), and MP2 levels using 6-31G(d), 6-31+G(d), 6-31G(2d), 6-31G(d,p), 6-31+G(d,p), 6-311G(d), 6-311G(2d,2p), 6-311++G(d,p), 6-311++G(2d,2p), and 6-311++G(3df,3pd) basis sets) were tested. On the whole, it is shown that, in contrast to what is claimed in the literature, high level of theory is not needed to obtain rather accurate predictions of (31)P CSs by the GIAO method. The PBE1PBE/6-31G(d)//PBE1PBE/6-31G(d) level can be recommended for express estimation of (31)P CSs. The PBE1PBE/6-31G(2d)//PBE1PBE/6-31G(d) combination can be recommended for routine applications. The PBE1PBE/6-311G(2d,2p)//PBE1PBE/6-31+G(d) level can be proposed to obtain better results at a reasonable cost. Scaling by linear regression parameters significantly improves results. The results obtained using these combinations were demonstrated in (31)P CS calculations for a variety of medium (large) size organic compounds of practical interest. Care has to be taken for compounds that may be involved in exchange between different structural forms (self-associates, associates with solvent, tautomers, and conformers). For phosphorus located near the atoms of third period elements ((CH3)3PS and P(SCH3)3) the impact of relativistic effects may be notable.
This paper describes the exohedral N-decoration of multiwalled carbon nanotubes (MWCNTs) with NH-aziridine groups via [2 + 1] cycloaddition of a tert-butyl-oxycarbonyl nitrene followed by controlled thermal decomposition of the cyclization product. The chemical grafting with N-containing groups deeply modifies the properties of the starting MWCNTs, generating new surface microenvironments with specific base (Brønsted) and electronic properties. Both of these features translate into a highly versatile single-phase heterogeneous catalyst (MW@N) with remarkable chemical and electrochemical performance. Its surface base character promotes the Knoevenagel condensation with activity superior to that of related state of the art N-doped and N-decorated carbon nanomaterials; the N-induced electronic surface redistribution drives the generation of high-energy surface "C" sites suitable for O activation and its subsequent electrochemical reduction (ORR).
Heating of a mixture of [Ni(CH2CH2)(dtbpe)] (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane)
and 2,6-dimesitylphenylphosphine (DmpPH2) in toluene gives
the secondary phosphine (Dmp)P(Et)(H) (1) as the main
product. However, thermolysis of [Ni(CH3)2(dtbpe)]
in the presence of DmpPH2 in toluene leads to the mononuclear
nickel phosphanido hydride complex [NiH{P(Dmp)(H)}(dtbpe)] (2), the product of an oxidative addition of a primary phosphine
to nickel(0). The structure of complex 2 was confirmed
by single-crystal X-ray diffraction and DNMR studies. The mutual exchange
of tautomers in which the Ni–H and P–H hydrogen atoms
interchange as well as the position of the hydrido and the phosphanido
ligand occurs in solution. The stoichiometric reaction of 2 with 1-hexene proceeds regiospecifically to form the secondary phosphine
(Dmp)P(Hex)(H) (3).
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