Hirshfeld surfaces and two-dimensional fingerprint plots are used to visualize and analyze intermolecular interactions in six new phosphoramidate structures, [2,6-F2-C6H3C(O)NH]P(O)[X]2 {X = N(C2H5)2 (1), [X]2 = NHCH2C(CH3)2CH2NH and with one CH3OH solvated molecule (2)}, [C6H5O]2P(O)Y [Y = NC4H8O (3), NHC6H4(3-Br) (4)] and [Z]2P(O)OP(O)[Z]2 [Z = N(CH3)(CH2C6H5) (5), NHC6H4(4-CH3) (6)]. Study of the short intermolecular contacts in structures (1)-(6) by Hirshfeld surfaces demonstrate that the O atom of P=O is a better H-atom acceptor than the O atom of C=O for (1) and (2), and also relative to the O atom of the C6H5O group for (3) and (4), and relative to the bridge O atom of the P(O)OP(O) segment for (5) and (6). The results confirm that the crystal packing is related to the kind of substituent linked to the P atom. Compounds (1), (2), (4) and (6), with characteristic N-H···O hydrogen bonds, show a pair of intense spikes (including the intermolecular H···O contacts) in the fingerprint plots, summarizing the major features of each structure in the related two-dimensional plot. For (3) and (5), without any N-H unit, the two short spikes are observed for (3) but are absent for (5). The upper d(e) and d(i) values (distances to the Hirshfeld surfaces for the nearest atoms outside and inside) in the fingerprint plots are more compact in (3) than in (4), and in (5) than in (6), reflecting the more efficient packing in (3) and (5). The tertiary N atoms of (3) and (5) do not take part in any intermolecular contacts involving H atoms. Moreover, structures (3)-(6) show greater contribution from C···H contacts relative to O···H contacts. Finally, Hirshfeld surfaces and fingerprint plots are employed for a comparison of the two independent molecules in the asymmetric unit of (1) and also, for a comparison of (6), in the orthorhombic crystal system, with the previously reported monoclinic polymorph (Pourayoubi, Fadaei et al., 2012).
Following the modular template synthesis using isonitriles,n ew unsymmetrically substituted five-membered saturated N-heterocyclic carbene (NHC)a nd N-heterocyclic oxo-carbene (NHOC) gold(I) complexes were prepared. With these species and already reported complexes,adetailed study concerning the catalytic activities of the complex classes available by the isonitrile routew as conducted. Thec atalytic properties of twelve different types of NHOCs, saturated and unsaturated NHC gold(I) pre-catalysts with different substituents,a sw ella s one representative of as ix-membered NHC and one N-acyclic carbene (NAC)g old(I) complex were analyzed by utilizing the phenol synthesisa satest reaction. Fort his reaction, the saturated NHC gold(I) complexes achieved higher conversions than the corresponding unsaturated NHCs andt he NHOC systems.W hile unsaturated NHC complexes show higher catalytic activity during the initial phase of the conversion, due to ah igher stability,h igher turnover numbers( TONs) were obtained for the corresponding saturated systems.Acyclopentadecyls ubstituenta tn itrogen turned out to be the privileged substituent for all of the unsymmetrical complexes. Furthermore,w ed etectedt hat light exclusion can significantly increase the catalytic activity of NHC gold(I) complexes for phenols ynthesis.
Different types of six-membered N-heterocyclic gold carbene complexes were prepared by using gold(I) isonitrile complexes as precursors in combination with suitably functionalized amines. The simple procedures provide an easy access to not only unsymmetrically substituted saturated carbene complexes but rarely reported types of carbene complexes such as six-membered N-heterocyclic oxo-carbene complexes, and six-membered partly unsaturated ligands can be obtained following the strategy.
The synthesis and isolation of the dinuclear NHC gold(I) allene-1,3-diyl complex Ph(IPrAu)CCCH(AuIPr) and the dinuclear NHC gold(I) propyne-1,3-diyl complex Ph(IPrAu)CH−CC−Au(IPr) are presented. The monoprotodeauration reactions of these dinuclear complexes selectively led to the mononuclear organogold complexes Ph(IPrAu)CCCH 2 and PhCH 2 −CC− Au(IPr), respectively. The experimental structures and the obtained analytical data of the synthesized complexes as well as the results of a computational DFT study of their thermodynamic stability are compared systematically.
The highly efficient eco-friendly synthesis of acetic acid (40% yield) directly from ethane is achieved by the unprecedented use of N-heterocyclic carbene (NHC) and N-heterocyclic oxo-carbene (NHOC) gold(I) catalysts in mild conditions. This is a selective and promising protocol to generate directly acetic acid from ethane, in comparison with the two most used methods: (i) the three-step, capital- and energy-intensive process based on the high-temperature conversion of methane to acetic acid; (ii) the current industrial methanol carbonylation processes, based in iridium and expensive rhodium catalysts. Green metrics determinations highlight the environmental advantages of the new ethane oxidation procedure. Comparison with previous reported published catalysts is performed to highlight the features of this remarkable protocol.
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