Titanium Complexes Supported by an [OSSO]-Type Bis(phenolato) Ligand Based on a trans-Cyclooctanediyl Platform: Synthesis, Structures, and 1-Hexene Polymerization

Abstract

trans-Cyclooctanediyl-bridged [OSSO]-type ligand 4 reacts with TiCl(4)(thf)(2) in toluene to produce the corresponding titanium(IV) dichloro complexes as an inseparable mixture of cis-α isomer 6a and cis-β isomer 6b in a ratio of 2:1, whereas treatment of dilithio salt of 4 with TiCl(3)(thf)(3) in Et(2)O afforded chloride-bridged dimeric titanium(III) complex 8, which indicated the antiferromagnetic character in a nonpolar solvent solution. Di(isopropoxy) titanium(IV) complex 10 having a C(2)-symmetric cis-α configuration was synthesized by the reaction of 4 with Ti(O(i)Pr)(4) in toluene as yellow crystals. Moreover, the reaction of 4 with Ti(NEt(2))(4) in toluene resulted in the unexpected formation of [OSSO]-type bis(phenolato)-bridged dinuclear diamido titanium(IV) complex 11, which adopted a distorted tetrahedral geometry on the titanium center. These titanium complexes were characterized on the basis of their NMR spectroscopic data, and the molecular structures of complexes 8, 10, and 11 were established by single crystal X-ray diffraction. The titanium(IV) and (III) complexes 6 and 8 upon activation with a cocatalyst in toluene polymerized 1-hexene isospecifically to produce poly(1-hexene) having high molecular weight (M(w) = 22,000-52,000 g mol(-1)) and relatively narrow polydispersity (M(w)/M(n) = 1.7-1.8), albeit with low activity [0.27-1.0 g mmol(cat)(-1) h(-1)].

Neutral Methyl and Cationic Aluminum Complexes Supported by a trans-1,2-Cyclooctanediyl-Bridged [OSSO]-Type Bis(phenolato) Ligand: Synthesis, Structures, and Use in Catalysis for Propylene Oxide Polymerization

“…The Al1–C1 bond length in 4 (1.953(2) Å) is close to those in reported [OSO]- and [OSSO]-type aluminum complexes (1.930–1.948 Å) and noticeably shortened relative to those of the corresponding five-coordinated methyl aluminum complexes incorporating [ONNO]-type ligands within the range 1.963–1.972 Å. , The S–C–C–S dihedral angle (67.81(13)°) deviates somewhat from the ideal 60° of the gauche conformation. Similar deviations, attributed to the conformation of cyclooctane rings, were observed in starting [OSSO]-type ligand 3 (75.3(3)°) and the related [OSSO]-type metal complexes (63.9(2)–76.7(3)°). − …”

“…Beyond the ubiquitous [ONNO]-type ligands, sulfur-linked bis(phenolate) [OSSO]-type ligands have also proven the formation of six-coordinated cationic aluminum species by Okuda . On the other hand, we have recently reported the development of the new [OSSO]-type ligand 1 based on a trans -1,2-cyclooctanediyl platform, along with the synthesis of several group 4 and 5 transition-metal complexes (Scheme ). − Upon activation with B(C 6 F 5 ) 3 or (Ph 3 C)[B(C 6 F 5 ) 4 ], dibenzylzirconium complex 2 achieved high activity up to 2500 g mmol –1 h –1 and complete isospecific polymerization of 1-hexene ([ mmmm ] >95%) . Moreover, the dibenzylhafnium complex 3 upon activation with dMAO (dried methylaluminoxane) led to the combination of high activity and controlled isotacticity in the polymerization of 1-hexene, 4-methyl-1-pentene, and propylene .…”

“…On the other hand, we have recently reported the development of the new [OSSO]-type ligand 1 based on a trans -1,2-cyclooctanediyl platform, along with the synthesis of several group 4 and 5 transition-metal complexes (Scheme ). − Upon activation with B(C 6 F 5 ) 3 or (Ph 3 C)[B(C 6 F 5 ) 4 ], dibenzylzirconium complex 2 achieved high activity up to 2500 g mmol –1 h –1 and complete isospecific polymerization of 1-hexene ([ mmmm ] >95%) . Moreover, the dibenzylhafnium complex 3 upon activation with dMAO (dried methylaluminoxane) led to the combination of high activity and controlled isotacticity in the polymerization of 1-hexene, 4-methyl-1-pentene, and propylene . As an extension of our previous work and taking into account the interest devoted to aluminum compounds supported by the [OSSO]-type ligand 1 , we present here the synthesis and characterization of a methylaluminum complex bearing the [OSSO]-type ligand together with the formation of its solvent-free dimeric cation derivative.…”

Highly Active and Isospecific Styrene Polymerization Catalyzed by Zirconium Complexes Bearing Aryl-substituted [OSSO]-Type Bis(phenolate) Ligands

“…Recently, we have succeeded in the development of an [OSSO]-type bis(phenolate) ligand ( 4 ) based on a trans -1,2-cyclooctanediyl platform and the preparation of several early-transition metal and aluminum complexes [43,44,45,46,47,48]. We have also found that zirconium(IV) and hafnium(IV) complexes 5 [49,50] and 6 [51] incorporating ligand 4 with activator could promote precisely isospecific polymerizations of α-olefins such as 1-hexene, 4-methyl-1-pentene, and propylene involving excellent activity (Scheme 1).…”

Carbazolyl-Substituted [OSSO]-Type Zirconium(IV) Complex as a Precatalyst for the Oligomerization and Polymerization of α-Olefins

“…Among them, dianionic [OSSO]-type tetradentate ligands, based on two phenoxide frameworks with two sulfur donors at the ortho-or benzyl-positions have been of great interest so far . We have reported several Group 4 and 5 metal complexes having an original [OSSO]-type bis(phenolate) ligand possessing a trans-1,2-cyclooctanediyl platform [38][39][40][41][42][43][44][45]. The combination of these complexes and activators could achieve the controlled isotactic polymerization of various α-olefins involving excellent activity.…”