Formation of Tri‐ and Tetranuclear Titanacycles through Decamethyltitanocene‐Mediated Intermolecular C–C Coupling of Dinitriles

Abstract

The reactions of [Cp*2 Ti(η(2) -Me3 SiC2 SiMe3 )] (Cp*=η(5) -pentamethylcyclopentadienyl) with various dicyano compounds were investigated. Nitrile-nitrile CC couplings result in multinuclear complexes owing to the bifunctionality of the substrates. Applying 1,3- or 1,4-dicyanobenzene led to tri- and tetranuclear complexes of the rare 1-metalla-2,5-diaza-cyclopenta-2,4-dienes. These are potential catalysts and were tested in the ring-opening polymerization of ε-caprolactone. The reaction with adiponitrile as alkyl dinitrile afforded a trinuclear 1-metalla-2,5-diaza-cyclopent-3-ene through additional protonation of the nitrogen atoms. The structure and bonding of the products were investigated by X-ray crystallography and DFT analysis to understand the molecular organization in the macrocycles.

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).…”

“…Using imidazole 5, 4,5-dimethylimidazole 6, benzimidazole 7 and 5,6-dimethylbenzimidazole 8 with the metallocene precursors [Cp 2 Ti(η 2 -C 2 (SiMe 3 ) 2 )] 1 and [Cp 2 Zr(py)(η 2 -C 2 (SiMe 3 ) 2 )] 2 resulted in the formation of the molecular rectangles 10-15. Reactions with zirconium were performed in n-hexane (12) or in a mixture of toluene/n-hexane (13) at 60°C without stirring and nearly black to violet crystals suitable for X-ray diffraction were obtained in moderate to good yields of 32-78 %. Reactions with zirconium were performed in n-hexane (12) or in a mixture of toluene/n-hexane (13) at 60°C without stirring and nearly black to violet crystals suitable for X-ray diffraction were obtained in moderate to good yields of 32-78 %.…”

“…Here, the increased steric demand hinders the formation of rectangles or squares. The Ti-N and Zr-N distances of the triangles 16-19 are on average slightly longer (2.28-2.37 Å) than in the tetramers (10)(11)(12)(13)(14)(15). Table 3 shows the distances between the metal centers, the angles between the metal centers und the bridging ligands, and the angles between the metal centers and their sum for the complexes 16-19.…”

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

“…Later by C‐C coupling reactions of benzodinitriles like 1,3‐ and 1,4‐dicyanobenzene by using Cp* 2 Ti(η 2 ‐btmsa) depending on the substitution of the cyano groups tri‐ or tetranuclear complex were obtained (Scheme ) …”

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

“…These were established by C−C couplings of aryl nitriles at [Cp* 2 M] (M=Ti, Zr) and isolated in high yields . This method could also be extended to dicyanobenzenes, thus forming tri‐ and tetranuclear compounds . Exploring the reactivity of Cp* 2 M(N=C(Ph)−C(Ph)=N) (M=Ti, Zr) towards H 2 , CO 2 or CH 3 −C≡N showed that the C−C bond of the five‐membered metallacycles was easily cleaved .…”