Carboranylimine-complexed titanium (IV) organometallics: An investigation of synthesis, structure and catalytic polymerization

Semi‐Crystalline Polar Polyethylene: Ester‐Functionalized Linear Polyolefins Enabled by a Functional‐Group‐Tolerant, Cationic Nickel Catalyst

“…The degree of branching was further reduced by increasing ethylene pressures to 4o r7atm, thereby favoring ethylene coordination and insertion over chain-walking.AtÀ20 8 8Cand 7atm of ethylene (entry 7), highly linear PE could be obtained (T m = 135 8 8C, < 1b ranch/1000 carbons). [15] Copolymerizations of ethylene and methyl 10-undecenoate [12,14,23] (both biorenewable monomers) [25] were con-ducted using rac-3 (Scheme 3; Table 2). During this time, molecular weights increased linearly with conversion, values remained consistently low ( = 1.25), and number average molecular weights (M n )a pproached 500 kDa, which was in good agreement with theoretical values.I ts hould be noted that the increased values observed as polymerization temperature was decreased (entries 4and 5) were most likely due to the deleterious effect of polymer precipitation from solution at those temperatures.C omparing the ethylene polymerization activity of rac-3 to other a-diimine nickel catalysts under identical conditions revealed that the activity was comparable to the complex derived from rac-2 and an acenaphthene linker, [17c] but half as active as the prototypical Brookhart catalyst derived from 2,6-diisopropylaniline and an acenaphthene linker (Supporting Information).…”

“…[7] While the latter has been achieved with free radical polymerization of ethylene,t he high temperatures and pressures required result in ah ighly branched amorphous PE material lacking the desired semi-crystalline properties of linear PE. [11][12][13][14] In contrast, late transition metal complexes pioneered by Brookhart and co-workers in the late 1990's [15] display enhanced stability toward polar functional monomers and can produce high molecular weight polymers in acontrolled/ living manner. [11][12][13][14] In contrast, late transition metal complexes pioneered by Brookhart and co-workers in the late 1990's [15] display enhanced stability toward polar functional monomers and can produce high molecular weight polymers in acontrolled/ living manner.…”

N,O-Type Carborane-Based Materials

“…Provided that the pyrrol moieties could be deprotonated, these compounds might provide rich coordination chemistry. Reaction of o-carboranylmethyl ammonium salt with commercially available phenyl aldehyde provided the phenyl(carboranylmethyl)imine 12 (Chart 2 and Scheme 3) in good yield [57]. Another interesting series of compounds is that of chiral bis(oxazolilnyl)-m-carboranes 13-14 that were synthesized via a multistep synthesis [58].…”

“…The introduction of carborane into the hmpH backbone provokes a bigger decrease of the alcohol pKa value, with respect to the related phenyl-hmpH (phhmpH) derivative (Scheme 4), in addition to an increase of the size and hydrophobicity of 1-4 with respect to phhmpH. Reaction of o-carboranylmethyl ammonium salt with commercially available phenyl aldehyde provided the phenyl(carboranylmethyl)imine 12 (Chart 2 and Scheme 3) in good yield [57]. Another interesting series of compounds is that of chiral bis(oxazolilnyl)-m-carboranes 13-14 that were synthesized via a multistep synthesis [58].…”

“…In situ deprotonation of 12 followed by reaction with TiCl 4 afforded complex 29 (Scheme 10) [57]. This complex is an efficient catalyst for α-olefin polymerization to produce high molecular weight polyethylene and poly(ethylene/methyl-10-undecannoate).…”