Directed Reduction of Six‐Membered Nitrogen Heterocycles—Selective Formation of Polynuclear Titanium Complexes

Abstract

Two, three, four, or eight N‐heterocycles react in the coordination sphere of titanium(II) compounds to give polynuclear titanium complexes (see picture, red=TiCp2, blue=N, white=C). Simultaneously occurring CC couplings mark a new strategy for the synthesis of self‐assembled compounds of the early transition metals.

Self‐Assembly Reactions To Form Multinuclear Zirconium(III) and Titanium(III) Complexes with Imidazole Derivatives as Bridging Ligands

“…This supports spontaneously C-C coupling reactions of 1,3-or 1,4dicyanobenzene, [12] adiponitrile, [12] 2,6-dicyanopyridine [13] or pyrazine [9,14] without or of quinoxalines [15] with C-H bond activation reactions and enable for instance the formation of the trinuclear complexes IV and V (Scheme 2). This supports spontaneously C-C coupling reactions of 1,3-or 1,4dicyanobenzene, [12] adiponitrile, [12] 2,6-dicyanopyridine [13] or pyrazine [9,14] without or of quinoxalines [15] with C-H bond activation reactions and enable for instance the formation of the trinuclear complexes IV and V (Scheme 2).…”

“…Complex 10 crystallizes in a rectangle with four different edge lengths and four different angles at the vertices. [9,10] The distance between titanium centers in the molecular square with pyrazine as bridging ligands was 7.20 Å. The complex has a "butterfly-like" arrangement ( Figure 6 left), and the zirconium atoms form a slightly distorted tetrahedron (Figure 6 right).…”

“…N-heterocyclic ligands are very prominent in the coordination chemistry due to their electronic and steric versatility. [9][10][11] The first example of a tetrahedrally coordinated titanium complex was a pyridine bridged cationic titanium(IV) complex synthesized by the reaction of [Cp 2 Ti(Cl)(NC 5 H 5 )] and AgOSO 2 CF 3 . [7,8] Molecular architectures with such bridging ligands are known for the low valent titanium.…”

“…[7,8] Molecular architectures with such bridging ligands are known for the low valent titanium. [9] Tetranuclear complexes employing four equal bridging ligands led to molecular squares of different sizes (I, II). [11] First self-assembly reactions to form multinuclear titanium(III) complexes with six membered N-heterocycles were shown by our group in 2004.…”

Syntheses and molecular structures of half-sandwich iridium metallarectangles containing bridging 2,5-dihydroxy-1,4- benzoquinonato (dhbq) ligands

“…After the first case of molecular square [{Pd(en)(l-4,4 0 -bipy)} 4 ](NO 3 ) 8 reported by Fujita and coworkers in 1990 [5], a series of supramolecules with platinum or palladium were developed in host-guest chemistry -encapsulating compounds, recognizing or trapping guest molecules, microreactors for specific reactions [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Using metal centers as corners and organic linkers in the build up of molecular architectures led to materials with new properties.…”