Ways in which osocyanides are used in organic chemistry are examined. Chemoselectivity and bond-making processes in relation to MCRs are also reviewed.
This review highlights recent studies discovering unconventional halogen bonding (HaB) that involves positively charged metal centers. These centers provide their filled d‐orbitals for HaB, and thus ...behave as nucleophilic components toward the noncovalent interaction. This role of some electron‐rich transition metal centers can be considered an oxymoron in the sense that the metal is, in most cases, formally cationic; consequently, its electron donor function is unexpected. The importance of Ha⋅⋅⋅d‐M (Ha=halogen; M is Group 9 (Rh, Ir), 10 (Ni, Pd, Pt), or 11 (Cu, Au)) interactions in crystal engineering is emphasized by showing remarkable examples (reported and uncovered by our processing of the Cambridge Structural Database), where this Ha⋅⋅⋅d‐M directional interaction guides the formation of solid supramolecular assemblies of different dimensionalities.
Metal centers provide their filled d‐orbitals for halogen bonding, and behave as nucleophilic components toward the noncovalent interaction.
The isocyanide trans‐PdBr2(CNC6H4‐4‐X′)2 (X′=Br, I) and nitrile trans‐PtX2(NCC6H4‐4‐X′)2 (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is ...determined by hitherto unreported four‐center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen‐bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic‐like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol−1.
The assembly of trans‐MX2L2 (M=Pt, 4‐X′C6H4CN; Pd, 4‐X′C6H4NC) occurred via the previously unreported four‐center heteroleptic cyclic nodes based exclusively on halogen bonding. These nodes serve as supramolecular synthons to form 2D‐layered structures.
► Acyclic diaminocarbenes (ADCs). ► ADC-based catalysts for organic transformations.
Starting from the first reported application of complexes bearing acyclic diaminocarbene (ADC) ligands as ...catalysts ca. 5 years ago, these compounds have been successfully employed for several useful organic transformations, viz. cross-coupling reactions (Suzuki–Miyaura, Heck, Sonogashira, Buchwald–Hartwig, and Kumada) and some cyclizations/additions to substrates having the CC and CC bonds. In these processes, ADC–metal complexes behave as an attractive alternative to extremely popular N-heterocyclic carbenes (NHCs). This review attempts to systematize studies published until now and to explain various observations and initial ideas on mechanisms and driving forces of ADC-based catalysts as well as to draw attention to the potential and the advantages that application of ADCs gives to synthetic organometallic and organic chemistry.
Facile gold-catalyzed heterocyclization based upon intermolecular trapping of the generated α-oxo gold carbenes with various cyanamides R2R3NCN (R2/R3 = Alk/Alk, −(CH2)2O(CH2)2–, Ar/Ar, Ar/H) has ...been developed. In most cases, 2-amino-1,3-oxazoles functionalized at the nitrogen atom as well as at the fifth position of the heterocyclic ring (12 examples) were isolated in good to moderate yields.
•Synthesis, properties, and identification of metal-free amidoximes.•Synthesis and structural features of amidoxime complexes.•Comparison of chemistry of amidoximes with that of conventional ...oximes.•Metal-mediated and metal-catalyzed reactions involving uncomplexed amidoximes.•Reactions of amidoxime ligands.
Although the versatile chemistry of conventional oximes has been extensively reviewed over the years in both the organic chemistry literature and the coordination chemistry literature, amidoximes, RC(NH2)NOH, have so far received substantially less attention. Taking into account the increased publication activity on the subject, we systematically review the data on the routes for preparation of amidoxime complexes, the coordination patterns of ligands, and the classification of metal-involving reactions of amidoxime species. This survey includes a comparison of the coordination chemistry and metal-involving reactions of amidoximes with those of conventional ketoximes and aldoximes.
Predominantly, carbon atoms of various species function as acceptors of noncovalent interactions when they are part of a π-system. Here, we report on the discovery of a halogen bond involving the ...isocyano carbon lone pair. The co-crystallization or mechanochemical liquid-assisted grinding of model mesityl isocyanide with four iodoperfluorobenezenes leads to a series of halogen-bonded adducts with isocyanides. The obtained adducts were characterized by single-crystal and powder X-ray diffraction, solid-state IR and
C NMR spectroscopies, and also by thermogravimetric analysis. The formation of the halogen bond with the isocyano group leads to a strong reduction of the isocyanide odor (3- to 46-fold gas phase concentration decrease). This manipulation makes isocyanides more suitable for laboratory storage and usage while preserving their reactivity, which is found to be similar between the adducts and the parent isocyanide in some common transformations, such as ligation to metal centers and the multi-component Ugi reaction.
Gold(
i
)-catalyzed highly regioselective hydration of alkynylsulfones comprises an efficient 100% atom-economic route to β-ketosulfones. The reaction proceeds under mild mercury-free conditions (Ph
...3
PAuNTf
2
0.5-5 mol%, THF, rt or 60 °C), it demonstrates a high functional group tolerance (more than 30 examples; yields up to 99%), and can be easily scaled up. The developed hydration methodology was successfully integrated into the one-pot syntheses of valuable heterocycles.
Gold(
i
)-catalyzed highly regioselective hydration of alkynylsulfones comprises an efficient 100% atom-economic route to β-ketosulfones.
Internal alkynes have been shown to undergo oxidation to substituted benzils (1,2‐diarylethane‐1,2‐diones) by α‐picoline N‐oxide in the presence of Ph3PAuNТf2 (5 mol‐%). In addition to the ...unsubstituted benzil, the method allows preparing, under markedly mild conditions (50 °C in chlorobenzene), various non‐symmetrical products, including heteroaromatic versions thereof which are much more difficult to obtain otherwise. This gold(I)‐catalyzed transformation was integrated into one‐pot reaction sequence delivering a range of 5‐ to 7‐membered ring systems (imidazoles, quinoxalines, 1,2,4‐triazines, pyrazines, and 1,4‐diazepines), thus linking these important heterocyclic motifs to the internal alkyne reagent space.
Internal alkynes have been shown to undergo oxidation to substituted benzils (1,2‐diarylethane‐1,2‐diones) by α‐picoline N‐oxide in the presence of Ph3PAuNТf2 (5 mol‐%).
The theoretical data for the half‐lantern complexes {Pt(CN^
)(μ‐SN^
)}2 1–3; CN^
is cyclometalated 2‐Ph‐benzothiazole; SN^
is 2‐SH‐pyridine (1), 2‐SH‐benzoxazole (2), 2‐SH‐tetrafluorobenzothiazole ...(3) indicate that the Pt⋅⋅⋅Pt orbital interaction increases the nucleophilicity of the outer dz2
orbitals to provide assembly with electrophilic species. Complexes 1–3 were co‐crystallized with bifunctional halogen bonding (XB) donors to give adducts (1–3)2⋅(1,4‐diiodotetrafluorobenzene) and infinite polymeric 1⋅1,1′‐diiodoperfluorodiphenyln. X‐ray crystallography revealed that the supramolecular assembly is achieved through (Aryl)I⋅⋅⋅dz2
PtII XBs between iodine σ‐holes and lone pairs of the positively charged (PtII)2 centers acting as nucleophilic sites. The polymer includes a curved linear chain ⋅⋅⋅Pt2⋅⋅⋅I(areneF)I⋅⋅⋅Pt2⋅⋅⋅ involving XB between iodine atoms of the perfluoroarene linkers and (PtII)2 moieties. The 195Pt NMR, UV/Vis, and CV studies indicate that XB is preserved in CH(D)2Cl2 solutions.
Shedding light: Half‐lantern dz2PtII2 complexes in which the PtII2 center exhibits increased nucleophilicity of the outer orbitals were assembled with symmetric diiodoperfluoroarene halogen bonding (XB) donors to give extended supramolecular arrays formed through (Aryl)I⋅⋅⋅dz2PtII XB, which were studied by XRD and by extensive theoretical calculations. Cyclic voltammetric, 195Pt NMR, and UV/Vis studies provided evidence that the XB is preserved in solution.
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