Synthesis, Structures, and Olefin Polymerization Capability of Vanadium(4+) Imido Compounds with fac-N₃ Donor Ligands

Abstract

One-pot reactions of V(NMe2)4 with a range of primary alkyl- and arylamines RNH2 and Me3SiCl afforded the corresponding five-coordinate vanadium(4+) imido compounds V(NR)Cl2(NHMe2)2 [R = 2,6-C6H3(i)Pr2 (1a, previously reported), 2-C6H4(t)Bu (1b), 2-C6H4CF3 (1c), (t)Bu (1d), Ad (Ad = adamantyl, 1e)]. The crystal structures of 1b (two diamorphic forms) and 1c featured N-H...Cl hydrogen-bonded chains. Reaction of 1a-e with the neutral face-capping, N3 donor ligands TACN (TACN = 1,4,7-trimethyltriazacyclononane) or TPM [TPM = tris(3,5-dimethylpyrazolyl)methane] gave the corresponding six-coordinate complexes V(NR)(TACN)Cl2 (2a-e) and V(NR)(TPM)Cl2 (3a-e). The X-ray structures of 2b, 2c, 2d, 3b, 3c, and 3e were determined. When activated with methylaluminoxane, certain of the complexes V(NR)(TPM)Cl2 (3) formed moderately active ethylene polymerization catalysts, whereas none of the compounds V(NR)(TACN)Cl2 (2) were active.

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

“…It is representative of a series of five-coordinate V(IV) imido complexes, V(=NR)(NHMe 2 ) 2 Cl 2 where R = five different bulky aryl or alkyl substituents. Their EPR parameters vary minimally as a function of R group as seen in Table 5 of Bigmore et al 47 Their A values have been converted from G to MHz using their reported g values. …”

Ethylene polymerization and ethylene/hexene copolymerization with vanadium(III) catalysts bearing heteroatom‐containing salicylaldiminato ligands

“…It is apparent from past decades studies that the predominant cause of this phenomenon is ascribed to reduction of catalytically active vanadium species to low‐valent, less active, or inactive species 3, 4. Design and synthesize ancillary ligands to stabilize the active species has proved to be an effective approach 5–25. A series of thermal robust vanadium catalysts have been reported recently, for example, the bis (benzimidazole) amine vanadium catalysts reported by Gibson's group displayed high efficiency for ethylene (co)polymerization and showed remarkable thermal stability 5(c).…”

“…A series of thermal robust vanadium catalysts have been reported recently, for example, the bis (benzimidazole) amine vanadium catalysts reported by Gibson's group displayed high efficiency for ethylene (co)polymerization and showed remarkable thermal stability 5(c). Aryloxide‐based vanadyl complexes, reported by Redshaw's group, exhibited excellent performance in olefin polymerization at an elevated temperature 17. High‐valent imido vanadium(IV or V) complexes were also tested as promising catalysts for ethylene (co) polymerization at an ambient temperature 15–17.…”

“…Aryloxide‐based vanadyl complexes, reported by Redshaw's group, exhibited excellent performance in olefin polymerization at an elevated temperature 17. High‐valent imido vanadium(IV or V) complexes were also tested as promising catalysts for ethylene (co) polymerization at an ambient temperature 15–17. The immobilization of soluble vanadium olefin polymerization catalysts onto inorganic supports (SiO 2 , MgCl 2 , MgO, etc.)…”

Stabilized Vanadium Catalyst for Olefin Polymerization by Site Isolation in a Metal–Organic Framework

“…With an interest in using MOF SBUs to stabilize vanadium catalysts for olefin polymerization, we targeted the material MFU-4l (Zn 5 Cl 4 (BTDD) 3 ;H 2 BTDD = bis(1H-1,2,3-triazolo [4,5-b],[4',5'-i])dibenzo[1,4]dioxin). [15] TheS BU of this triazole-based MOF features facial coordination of Zn 2+ by three nitrogen atoms, [16] as corpionate unit shown to structurally and functionally emulate the tris(pyrazolyl)borate [17] and tris(pyrazolyl)methane [18] ligands that provide effective vanadium catalysts for olefin polymerization. Based on this analogy between SBUsa nd small molecules,w e anticipated that incorporation of vanadium into MFU-4l by cation exchange would provide an effective vanadium catalyst, further benefitting from site isolation ( Figure 1).…”