Vanadium(V) Oxo and Imido Calix[8]arene Complexes: Synthesis, Structural Studies, and Ethylene Homo/Copolymerisation Capability

Abstract

Interaction of p‐tert‐butylcalix[8]areneH8 (L8H8) with [NaVO(OtBu)4] (formed in situ from VOCl3) afforded the complex [Na(NCMe)5][(VO)2L8H]⋅4 MeCN (1⋅4 MeCN). Increasing [NaVO(OtBu)4] to 4 equiv led to [Na(NCMe)6]2[(Na(VO)4L8)(Na(NCMe))3]2⋅10 MeCN (2⋅10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(OtBu)3] with L8H8 afforded the alkali‐metal‐free complex [(VO)4L8(μ3‐O)2] (3); solvates 3⋅3 MeCN and 3⋅3 CH2Cl2 were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert‐butoxide was added to L8H8 and then treated with 2 equiv of VOCl3; crystallisation afforded [(VO2)2Li6[L8](thf)2(OtBu)2(Et2O)2]⋅Et2O (4⋅Et2O). Upon extraction into acetonitrile, [Li(NCMe)4][(VO)2L8H]⋅8 MeCN (5⋅8 MeCN) was formed. Use of the imido precursors [V(NtBu)(OtBu)3] and [V(Np‐tolyl)(OtBu)3] and L8H8, afforded [tBuNH3][{V(p‐tolylN)}2L8H]⋅3 1/2 MeCN (6⋅3 1/2 MeCN). The molecular structures of 1 to 6 are reported. Complexes 1, 3, and 4 were screened as precatalysts for the polymerisation of ethylene in the presence of cocatalysts at various temperatures and for the copolymerisation of ethylene with propylene. Activities as high as 136 000 g (mmol(V) h)−1 were sometimes achieved; higher molecular weight polymers could be obtained versus the benchmark [VO(OEt)Cl2]. For copolymerisation, incorporation of propylene was 7.1–10.9 mol % (compare 10 mol % for [VO(OEt)Cl2]), although catalytic activities were lower than [VO(OEt)Cl2].

INSIGHTS into the structures adopted by titanocalix[6 and 8]arenes and their use in the ring opening polymerization of cyclic esters

“…8 Furthermore, the systems incorporating vanadium have exhibited high catalytic activities in the area of α-olefin polymerization. 9 In the area of ring opening polymerization (ROP) of cyclic esters, reports using metallocalix [n]arenes are scant. In the case of tungstocalix [6 and 8]arenes, we observed how different sized calixarene rings and their associated conformations can drastically affect the catalytic activity for the ROP of ε-caprolactone (ε-CL).…”

Synthesis of ultra‐high‐molecular‐weight ethylene‐propylene copolymer via quasi‐living copolymerization with N‐heterocyclic carbene ligated vanadium complexes

“…However, it is difficult to synthesize UHMW ethylene‐propylene copolymers with high propylene content using the traditional vanadium catalysts in industry. Vanadium complex catalyst for ethylene/propylene copolymerization has attracted more and more attention . UHMW ethylene‐propylene copolymers could be synthesized by vanadium complex catalysts .…”

Synthesis of Disentangled Ultra‐High Molecular Weight Polyethylene using Vanadium(V)‐Based Catalysts

“…Multinuclear vanadium species have also been synthesized and tested for their ability to promote the polymerization of ethylene; some complexes show the ability to produce UHMWPE …”