Supramolecular bulky phosphines comprising 1,3,5-triaza-7-phosphaadamantane and Zn(salphen)s: structural features and application in hydrosilylation catalysis

Anselmo, Daniele; Gramage‐Doria, Rafael; Besset, Tatiana; Escárcega‐Bobadilla, Martha V.; Salassa, Giovanni; Escudero‐Adán, Eduardo C.; Belmonte, Marta Martínez; Martín, Eddy; Reek, Joost N. H.; Kleij, Arjan W.

doi:10.1039/c3dt00078h

“…The latter has delivered access to their wide use as building blocks in self-assembled nanoarchitectures [11], auto-organized nanofibers [12], and many other different supramolecular host-guest systems [13,14,15]. This situation has inspired new strategies to develop a variety of supramolecular applications, such as self-assembled soft-matter [16,17,18,19], supramolecular sensors [20,21,22,23], and supramolecular catalysis [24,25,26].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of a Novel Zn-Salphen Building Block and Its Acrylic Terpolymer Counterparts as Tunable Supramolecular Recognition Systems

Zelada‐Guillén

¹

,

Cuéllar-Sánchez

²

,

Romero‐Ávila

³

et al. 2019

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In this work, we present the synthesis of a novel Zn-Salphen complex containing an allyl group, which was used as building block in the further preparation of a new family of functional terpolymers. These polymers were obtained through radical co-polymerization with methyl metacrylate (MMA) and n-butyl acrylate (nBuA) in different ratios. The supramolecular recognition behavior of each polymer was evaluated via potentiometric measurements against selected anions in aqueous media. Interestingly, this proof of concept study shows that these systems were selective against only fluoride (F−) or both, fluoride and acetate (OAc−), by tailoring the relative content of Zn-Salphen monomer, thus making them a promising starting point for modular design of chemical sensors through straightforward synthetic approaches.

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“… 20 , 22 In addition, unprecedented high enantioselectivity in the asymmetric hydroformylation of internal unfunctionalized alkenes 28 , 29 , 31 has been achieved. The ligand template strategy was also applied in the Heck reaction, 18 polymerization, 34 hydrogenation, 33 hydrosilylation, 36 and gold catalysis. 35 Divergent ligand templates have been used to generate nanospheres with multiple complexes in confined space.…”

Section: Discussionmentioning

confidence: 99%

Ligand Template Strategies for Catalyst Encapsulation

Jongkind

¹

,

Caumes

²

,

Hartendorp

³

et al. 2018

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ConspectusBinding of molecules in molecular cages based on self-assembled concave building blocks has been of great interest to scientists for decades. The binding of static molecular fragments inside cage-like molecular structures is generally based on complementarity of host and guest in terms of shape and interactions. The encapsulation of homogeneous catalysts in molecular cages is of interest as activity, selectivity, and stability can be controlled by the cage as second coordination sphere, reminiscent of how enzymes control chemical reactivity. Homogeneous catalysts, however, are not static guest molecules as catalysts change in shape, charge, and polarity during the catalytic cycle, representing the challenges involved in cage controlled catalysis. To address these issues, we developed a new strategy that we coined the “ligand template approach for catalyst encapsulation”. This strategy relies on ligand building blocks that contain multiple orthogonal binding sites: the central ligand (mostly phosphorus) is bound to the transition metal required for catalysis, while other binding sites are used to construct a cage structure around the transition metal atom through self-assembly. By design, the catalyst is inside the capsule during the catalytic cycle, as the central ligand is coordinated to the catalyst. As the approach is based on a self-assembly process of building blocks, the catalyst properties can be easily modulated by modification of building blocks involved.In this Account, we elaborate on template ligand strategies for single catalyst encapsulation, based on divergent ligand templates and the extension to nanospheres with multiple metal complexes, which are formed by assembly of convergent ligand templates. Using the mononuclear approach, a variety of encapsulated catalysts can be generated, which have led to highly (enantio)selective hydroformylation reactions for encapsulated rhodium atoms. Besides the successes of encapsulated rhodium catalysts in hydroformylation, mononuclear ligand template capsules have been applied in asymmetric hydrogenation, the Heck reaction, copolymerization, gold catalyzed cyclization reactions, and hydrosilylation reactions. By changing the capsule building blocks the electronic and steric properties around the transition metal atom have successfully been modified, which translates to changes in catalyst properties. Using the convergent ligand templates, nanospheres have been generated with up to 24 complexes inside the sphere, leading to very high local concentrations of the transition metal. The effect of local concentrations was explored in gold catalyzed cyclization reactions and ruthenium catalyzed water oxidation, and for both reactions, spectacular reaction rate enhancements have been observed. This Account shows that the template ligand approach to provide catalyst in well-defined specific environments is very versatile and leads to catalyst properties that are not achievable with traditional approaches.

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“…After the first Zn–PTA complexthe distorted tetrahedral [ZnCl 2 (PTA-κ N ) 2 ]was described in 2009 by Pombeiro and co-workers, Reek, Kleij et al investigated the reactivity of PTA with a number of square-planar Zn(salphen) complexes (salphen = N , N ′-bis(salicylidene)imine-1,2-phenylenediamine) in the context of supramolecular catalysis. It was found that PTA binds to zinc exclusively through the N atoms and can act as a bridge between two or even three Zn(salphen) units, giving [{Zn(salphen)} 2 (PTA-κ 2 N )] and [{Zn(salphen)} 3 (PTA-κ 3 N )] adducts in which the zinc ions have a distorted square planar geometry …”

Section: Introductionmentioning

confidence: 99%

“…For example, the association constant of pyridine with Zn(TPP) (TPP = meso -tetraphenylporphyrin) was found to be 7.7 × 10 3 M –1 (CH 2 Cl 2 , 25 °C), whereas under the sameor very similarconditions amines (including tertiary amines) have ca. 10-fold larger association constants. , By comparison, hexamethylenetetramine (HTMA)the all-nitrogen analogue of PTAwas found to make stronger axial bonds with Zn–porphyrins compared to pyridyl functions (probably also because of its low steric demand), and binding constants in the range 10 5 to 10 6 M –1 were measured for the axial N-binding of PTA to square planar Zn(salphen) complexes in toluene …”

Section: Introductionmentioning

confidence: 99%

Orthogonal Coordination Chemistry of PTA toward Ru(II) and Zn(II) (PTA = 1,3,5-Triaza-7-phosphaadamantane) for the Construction of 1D and 2D Metal-Mediated Porphyrin Networks

Battistin

¹

,

Vidal

²

,

Cavigli

³

et al. 2020

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This work demonstrates that PTA (1,3,5-triaza-7-phosphaadamantane) behaves as an orthogonal ligand between Ru(II) and Zn(II), since it selectively binds through the P atom to ruthenium and through one or more of the N atoms to zinc. This property of PTA was exploited for preparing the two monomeric porphyrin adducts with axially bound PTA, [Ru(TPP)(PTA-κ P ) 2 ] ( 1 , TPP = meso -tetraphenylporphyrin) and [Zn(TPP)(PTA-κ N )] ( 3 ). Next, we prepared a number of heterobimetallic Ru/Zn porphyrin polymeric networks—and two discrete molecular systems—mediated by P,N -bridging PTA in which either both metals reside inside a porphyrin core, or one metal belongs to a porphyrin, either Ru(TPP) or Zn(TPP), and the other to a complex or salt of the complementary metal (i.e., cis,cis,trans -[RuCl 2 (CO) 2 (PTA-κ P ) 2 ] ( 5 ), trans -[RuCl 2 (PTA-κ P ) 4 ] ( 7 ), Zn(CH 3 COO) 2 , and ZnCl 2 ). The molecular compounds 1 , 3 , trans -[{RuCl 2 (PTA-κ 2 P,N ) 4 }{Zn(TPP)} 4 ] ( 8 ), and [{Ru(TPP)(PTA-κ P )(PTA-κ 2 P,N )}{ZnCl 2 (OH 2 )}] ( 11 ), as well as the polymeric species [{Ru(TPP)(PTA-κ 2 P,N ) 2 }{Zn(TPP)}] ∞ ( 4 ), cis,cis,trans -[{RuCl 2 (CO) 2 (PTA-κ 2 P,N ) 2 }{Zn(TPP)}] ∞ ( 6 ), trans -[{RuCl 2 (PTA-κ 2 P,N ) 4 }{Zn(TPP)} 2 ] ∞ ( 9 ), and [{Ru(TPP)(PTA-κ 3 P,2N ) 2 }{Zn 9 (CH 3 COO) 16 (CH 3 OH) 2 (OH) 2 }] ∞ ( 10 ), were structurally characterized by single crystal X-ray diffraction. Compounds 4 , 6 , 9 , and 10 are the first examples of so...

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Supramolecular bulky phosphines comprising 1,3,5-triaza-7-phosphaadamantane and Zn(salphen)s: structural features and application in hydrosilylation catalysis

Cited by 15 publications

References 54 publications

Synthesis of a Novel Zn-Salphen Building Block and Its Acrylic Terpolymer Counterparts as Tunable Supramolecular Recognition Systems

Synthesis of a Novel Zn-Salphen Building Block and Its Acrylic Terpolymer Counterparts as Tunable Supramolecular Recognition Systems

Ligand Template Strategies for Catalyst Encapsulation

Orthogonal Coordination Chemistry of PTA toward Ru(II) and Zn(II) (PTA = 1,3,5-Triaza-7-phosphaadamantane) for the Construction of 1D and 2D Metal-Mediated Porphyrin Networks

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