Unprecedented Use of NHC Gold (I) Complexes as Catalysts for the Selective Oxidation of Ethane to Acetic Acid.

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.

Hirshfeld surface analysis of new phosphoramidates.

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).

Diphenyl (o-tolyl-amido)-phospho-nate.

The asymmetric unit of the title compound, C(19)H(18)NO(3)P, contains two independent mol-ecules in which the P atoms are found in slightly distorted tetrahedral environments. In the crystal, pairs of inter-molecular N-H⋯O(P) hydrogen bonds form two independent centrosymmetric dimers.

Diphenyl (cyclo-pentyl-amido)-phospho-nate.

In the title mol-ecule, C(17)H(20)NO(3)P, the P atom is bonded in a distorted tetra-hedral environment. The dihedral angle between the two phenyl rings is 23.52 (10)°. The phosphoryl and N-H groups are anti with respect to one another. The -CH(2)-CH(2)-CH(2)-CH(2)- sequence of atoms in the cyclo-pentyl ring is disordered over two sets of sites with refined occupancies of 0.574 (10) and 0.426 (10). In the crystal, mol-ecules are linked via N-H⋯O=P hydrogen bonds to form extended chains along [010].

Tetra-phenyl piperazine-1,4-diyldiphos-pho-nate.

The mol-ecule of the title compound, C(28)H(28)N(2)O(6)P(2), is organized around an inversion center located at the centre of the piperazine ring. Both piperazine N atoms are substituted by P(O)(OC(6)H(5))(2) phospho-ester groups. The P atoms display a slightly distorted tetra-hedral environment; the N atoms show some deviation from planarity. The O atoms of the P=O groups are involved in inter-molecular C-H⋯O hydrogen bonds, building R(2) (2)(22) rings, in extended chains parallel to the a axis. C-H⋯π inter-actions involving the phenyl rings further stabilize the packing.

Diphenyl (p-tolyl-amido)-phosphate.

The P atom in the title compound, C(19)H(18)NO(3)P, exhibits a distorted tetra-hedral configuration while the N atom shows a planar coordination. In the crystal, inter-molecular N-H⋯O hydrogen bonds form centrosymmetric dimers.

Diphenyl (2-chloro-benzyl-amido)-phosphate.

In the title compound, C(19)H(17)ClNO(3)P, the P atom exhibits a distorted tetra-hedral configuration. In the crystal, pairs of inter-molecular N-H⋯O(P) hydrogen bonds form centrosymmetric dimers.

Diphenyl (benzyl-amido)phosphate.

The title compound, C(19)H(18)NO(3)P, was prepared by the reaction of diphenyl phospho-rochloridate and benzyl-amine. In the crystal structure, mol-ecules are linked via N-H⋯O=P hydrogen bonds into extended chains parallel to the c axis.