Arylimidovanadium(V) Complexes for a Tridendritic Centrosymmetric Structural Motif or Axial Chirality

Oxovanadium(v)-catalyzed amination of carbon dioxide under ambient pressure for the synthesis of ureas

Carbon dioxide is regarded as a reliable C1 building block in organic synthesis because of the nontoxic, abundant, and economical characteristics of carbon dioxide. In this manuscript, a commercially available oxovanadium(v) compound was demonstrated to serve as an efficient catalyst for the catalytic amination of carbon dioxide under ambient pressure in the synthesis of ureas. The catalytic transformation of chiral amines into the corresponding chiral ureas without loss of chirality was also performed. Furthermore, a gram-scale catalytic urea synthesis under ambient pressure was successfully achieved to validate the scalability of this catalytic activation of carbon dioxide.

Catalytic activation of carbon dioxide as a C1 building block under ambient pressure was performed by using a commercially available oxovanadium(v) catalyst for the synthesis of ureas.

Alkoxide ligand controlled self-assembling of (imido)vanadium(V) compounds having a tetrahedral VO3N geometry

The reaction of (1S,2S)-(-)-1,2-diphenylethylenediamine with VO(OⁱPr)₃ in the presence of NaH was found to afford the binuclear (imido)vanadium(V) triisopropoxide, [(OⁱPr)₃V(N-meso-1,2-DPE-N)V(OⁱPr)₃] (DPE = diphenylethylene), (1a_RS/SS). Using (1R,2R)-(+)-1,2-diphenylethylenediamine as a starting material, one-step reaction also proceeded to form the binuclear (imido)vanadium(V) triisopropoxide, [(OⁱPr)₃V(N-meso-1,2-DPE-N)V(OⁱPr)₃], (1a_RS/RR). The single-crystal X-ray structure determination of 1a_RS/SS revealed the hydrogen-bonded self-assembled structure utilizing the advantage of anti-conformation through the intermolecular hydrogen bonds of C-H···O pattern between phenyl and isopropoxide moieties, wherein each vanadium atom is coordinated in a nearly tetrahedral VO₃N geometry (τ₄ = 0.017 and 0.057). On the contrary, a discrete (imido)vanadium(V) tris(triphenylsiloxide) unit, which possesses a nearly tetrahedral VO₃N arrangement around the vanadium metal center (τ₄ = 0.060), was observed in the crystal structure of the (4-methoxyphenylimido)vanadium(V) tris(triphenylsiloxide), [(p-MeOC₆H₄N)V(OSiPh₃)₃], (1b) with bulky triphenylsiloxide ligands.

Vanadium(v) phenolate complexes for ring opening homo- and co-polymerisation of ε-caprolactone, l-lactide and rac-lactide

Vanadium(v) di-, tri- and tetra-phenolate complexes have been screened for their ability to ring open homo- (and co-) polymerise ε-caprolactone, l-lactide and rac-lactide.

Design and redox function of conjugated complexes with polyanilines or quinonediimines

Because of their potential application as new electrical materials that depend on their redox properties, π-conjugated polymers and oligomers have attracted much attention. Polyanilines, which are chemically stable, are one of the promising classes of conducting π-conjugated polymers. Polyanilines exist in three different discrete redox forms, which include the fully reduced leucoemeraldine, the semioxidized emeraldine, and the fully oxidized pernigraniline base form. The redox-active 1,4-phenylenediamine (PD) and 1,4-benzoquinonediimine, unit molecules of the emeraldine base form, can bind to transition metals to afford novel conjugated complexes. The introduction of metal centers into π-conjugated polymers is expected to dramatically change their functions. In this Account, we describe our ongoing research into the construction of conjugated complexes with redox-active π-conjugated polyanilines and 1,4-benzoquinonediimines. These systems can form architecturally controlled functionalized systems that depend on their dynamic redox properties, resulting in highly selective and versatile electron-transfer reactions and functionalized materials. Complexation with metals (Pd, V, Cu, etc.) occurred via the two nitrogen atoms of the quinonediimine moiety of the emeraldine base form of poly(o-toluidine) to afford the single-strand or cross-linked network conjugated complexes with d,π-conjugation. The complexation of the redox-active π-conjugated 1,4-benzoquinonediimines, unit molecules of the emeraldine base form, with palladium(II) compounds yielded a variety of conjugated complexes. Through regulation of the coordination mode of the quinonediimine moiety, we were able to architecturally control the formation of conjugated bimetallic, polymeric, or macrocyclic complexes. Complexation modulated the redox function of the quinonediimine moiety. Introduced metals act as a metallic dopant, and the complexed quinonediimine is stabilized as an electron sink. Furthermore, chirality could be induced into a π-conjugated backbone through complexation with optically active transition compounds, resulting in chiral d,π-conjugated complexes. We could also modulate the functional properties of conjugated complexes based on the redox states of the redox-active π-conjugated moieties. We also demonstrated how complexes with redox-active π-conjugated molecules can control the architecture of redox-functionalized systems through the metal imido bonds of these systems. Using the one-pot preparation of (arylimido)vanadium(V) compounds from the corresponding anilines, we synthesized binuclear complexes with axial chirality and trinuclear complexes with a tridendritic centrosymmetric structural motif. Such structures showed a strong tendency to self-assemble.