Trispyrazolylborate Ligands Supported on Vinyl Addition Polynorbornenes and Their Copper Derivatives as Recyclable Catalysts

Abstract

Polynorbornenes prepared by vinyl addition polymerization and bearing pendant alkenyl groups serve as skeletons to support trispyrazolylborate ligands (Tp ) built at those alkenyl sites. Reaction with CuI in acetonitrile led to VA-PNB-Tp Cu(NCMe) (VA-PBN=vinyl addition polynorbornene) with a 0.8-1.4 mmol incorporation of Cu per gram of polymer. The presence of tetracoordinated copper(I) ions was been assessed by FTIR studies on the corresponding VA-PNB-Tp Cu(CO) adducts, in agreement with those on discrete Tp Cu(CO). The new materials were employed as heterogeneous catalysts in several carbene- and nitrene-transfer reactions, showing a behavior similar to that of the homogeneous counterparts but also being recycled several times maintaining a high degree of activity and selectivity. This is the first example of supported Tp ligands onto polymeric supports with catalytic applications.

Vinylic addition poly(norbornene-co-alkenylnorbornenes) synthesized with benzylic palladium catalysts: materials for manifold functionalization

“…The dramatic changes in the solubility of these VA-PNBs upon functionalization are known and they have been reported before for other functional groups, such as imidazolium fragments, by our research group. 16,17,42 In addition to the structural changes introduced by the new substituent, a modification of the conformational behavior of the rigid bicyclic units in the polymer backbone during the hydroboration/ oxidation or hydrosilylation processes could also contribute to this change in solubility behavior. 43 VA-PNB-co-VNB polymers are easily hydroborated under mild conditions in the presence of BHBr 2 •SMe 2 (Scheme 4).…”

Vinylic Addition Polynorbornene in Catalysis

“…Some alkenyl norbornene monomers are commercialy available and several reports can be found in the literature that show the polymerization and subsequent transformation of the pendant double bond in an epoxide, or an alcohol ,. [Ni(C 6 F 5 ) 2 (SbPh 3 ) 2 ] has also shown to be a suitable catalyst for the synthesis of alkenyl VA‐PNBs of different chain lengths (Scheme ) …”

“…A different type of ligand that has been rarely anchored to a solid support is trispyrazolylborate (Tp). The use of some of the alkenyl substituted VA‐PNBs shown in Scheme as starting materials, allows a synthetic route that leads to the VA‐PNB‐supported trispyrazolylborate derivatives 9 with a range of substitution patterns (Scheme ) . Despite the importance of Tp ligands in catalysis with different metals, the use of solid‐supported trispyrazolylborate complexes as recyclable catalysts had not been achieved.…”

“…As shown in Scheme , complexes 10 are recyclable catalysts in cyclopropanation reactions and, albeit a small activity loss after the first cycle, also reusable for the aziridination of alkenes and the nitrene insertion into C−H bonds …”

Heterogeneous Olefin Aziridination Reactions Catalyzed by Polymer‐Bound Tris(triazolyl)methane Copper Complexes

“…To the best of our knowledge, the use of polymeric supports for the olefin aziridination reaction is limited to a ruthenium-based system reported by Gallo [6] and a copper-based system previously described by Albeniz and our group. [7] We have previously described [8] the use of polystyrene-linked tris(triazolyl)methane copper(I) cationic catalysts for the transfer of carbene units from diazo compounds to several saturated and unsaturated substrates in batch and flow. Herein we report that a Cu(I) complex attached to polystyrene catalyzes the transfer of the NTs (Ts = p-toluenesulfonyl) group from PhI = NTs to olefins bearing aryl, alkyl or carboxyl substituents, in good to high yields and with acceptable ratios of recovery and recycling.…”