Cross olefin metathesis for the selective functionalization, ferrocenylation, and solubilisation in water of olefin-terminated dendrimers, polymers, and gold nanoparticles and for a divergent dendrimer construction

Olefin cross metathesis was used to efficiently functionalize, polyolefin dendrimers, polymers, and gold nanoparticles using the second-generation Grubbs catalyst. In these structures, the tethers were lengthened to prevent the facile cross metathesis that otherwise predominates in polyolefin dendrimers having short tethers. This synthetic strategy allows the one-step access to polyacid, polyester, and polyferrocenyl structures from polyolefins. Cross metathesis is also used to efficiently achieve an iterative divergent dendritic construction. All the cross metathesis reactions were monitored by H-1 NMR showing the chemio-, regio-, and stereoselectivity. MALDI-TOF mass spectrometry was a very useful technique to confirm the efficiency of this synthetic strateg

Synthesis, Chemistry, DFT Calculations, and ROMP Activity of Monomeric Benzylidene Complexes Containing a Chelating Diphosphine and of Four Generations of Metallodendritic Analogues. Positive and Negative Dendritic Effects and Formation of Dendritic Ruthenium−Polynorbornene Stars

The reaction of Hoveyda's catalyst [Ru{η2-(CHAr)}(PCy3)Cl2] (1; Ar = o-O-i-Pr-C6H4) with the diphosphine PhCH2N(CH2PCy2)2 (2) gives the new air-stable green ruthenium carbene complex [Ru{η1-(CHAr)}{η2-(Cy2PCH2)2N(CH2Ph)}Cl2] (3A), in which 2 models a dendritic branch of poly(diphosphine) dendrimers DAB-dendr-[N(CH2PCy2)2]n (G1, n = 4; G2, n = 8; G3, n = 16; G4, n = 32). The complex 3A reversibly dimerizes in concentrated solution, a trend favored at low temperature. The structure of 3A was also confirmed by DFT calculations, which also establish the dimeric structure of 3B and the fact that the dimerization energy of 3A is small. Facile halide abstraction is shown by MALDI-TOF mass spectroscopy, and reaction with AgPF6 gives the air-stable green dicationic dimer 5, whose structure has been confirmed by DFT calculations and whose reactions with ligands (I- and DMSO) gives monomeric alkylidene complexes. The diiodo analogue of 3A, 7A, is also synthesized by addition of NaI to either 3A or 5 and dimerizes more readily than the dichloro analogue 3A. On the basis of this chemistry, metallodendrimers DAB-dendr-[PCy2CH2NCH2PCy2Ru(CHAr)(PPh3)(Cl)2]n (8−11) derived from the four first generations of DAB polyamines containing, respectively, 4, 8, 16, and 32 ruthenium branches have been synthesized and characterized by elemental and standard spectroscopic analysis. Dimerization of the ruthenium alkylidene species of these dendrimers is found to increase upon dilution, which is taken into account by intradendritic dimerization and larger extension of the branches, providing more freedom for dimerization in dilute solution. These dendritic ruthenium−carbene complexes are shown to initiate the ROMP of norbornene at room temperature to form star-shaped metallodendritic polymers. Interestingly, the metallodendrimer G1 initiates the ROMP of norbornene much faster than the model ruthenium complex 3, the overall rate order being G1 > G2 > G3 > model. The dramatic positive dendritic effect is rationalized in terms of the labilization of a ruthenium−phosphorus bond at each Ru within the dendrimers. Such a speculative dissociative metathesis mechanism (3A, 16e → 14e) would be in accord with the limited ROMP activity, the lack of RCM activity, the instability in air, and the DFT calculations showing that the interaction of 3A with ethylene is repulsive. The second dendritic effect, negative among the generations, is taken into account by the increasing bulk as the generation number increases, slowing down the approach of Ru by norbornene. Cleavage of the polynorbornene branches of these metallodendritic polymer stars using ethyl vinyl ether followed by SEC analysis shows that the observed masses are close to the theoretical ones, indicating that dendritic-star polymers have formed in the ROMP process

Olefin metathesis in nano-sized systems

The interplay between olefin metathesis and dendrimers and other nano systems is addressed in this mini review mostly based on the authors’ own contributions over the last decade. Two subjects are presented and discussed: (i) The catalysis of olefin metathesis by dendritic nano-catalysts via either covalent attachment (ROMP) or, more usefully, dendrimer encapsulation – ring closing metathesis (RCM), cross metathesis (CM), enyne metathesis reactions (EYM) – for reactions in water without a co-solvent and (ii) construction and functionalization of dendrimers by CM reactions

Mo6Br8-Cluster-cored organometallic stars and dendrimers

Theoctahedralmolybdenumcluster[n-Bu4N]2[Mo6Br8(CF3SO3)6]undergoessubstitutionofallsixterminaltriflateligands withtheorganometallicpyridineligands[RuCp(PPh3)2(g1-C2-4-pyridinyl)],1,and1-ferrocenyl-2-(4-pyridinyl)acetylene,5,to give the new light and air sensitive hexa-functionalized Mo6 clusters 4 and 7 respectively, and with the dendronic phenolate ligand p-NaO–C6H4C{CH2CH2CH2Si(Me)2Fc}3, 8, to give the air-sensitive Mo6-cluster-cored octadecylferrocenyl dendrimer 9 that discloses a single CV wave in CH2Cl2 and recognizes the biologically important adenosyl triphosphate di-anion (ATP2-). The organometallic pyridines 1 and 5 were also coordinated toAg+ to give the new trinuclearAgRu2 andAgFc2 cationic complexes 2 and 6 respectively for comparison of the structures and electronic delocalization with those of the clusters.L’agrégat octaédrique [n-Bu4N]2[Mo6Br8(CF3SO3)6] subit la substitution des six coordinats triflates terminaux avec les ligandspyridiniquesorganométalliques[RuCp(PPh3)2(g1-C2-4-pyridinyl)],1,et1-ferrocenyl-2-(4-pyridinyl)acetylene,5,pour donner de nouveaux agrégats hexamolybdène hexafonctionnels 4 et 7, respectivement. Avec le phénate dendronique p-NaO– C6H4C{CH2CH2CH2Si(Me)2Fc}3,8, le dendrimère hexamolybdène octadécylferrocényle9est obtenu. Ce composé donne une seule vague en voltammétrie cyclique dans CH2Cl2 et reconnaît le dianion de l’ATP, dont l’importance est connue en biologie. Lespyridinesorganométalliques1et5ontaussiétécoordonéesàAg+ pourdonnerlesnouveauxcomplexestrinucléairesAgRu2 et AgFc2 2 et 6 respectivement, afin de comparer leur structure électronique à celles des agrégats.info:eu-repo/semantics/publishedVersio

From simple monopyridine clusters [Mo6Br13(Py-R)][n-Bu4N] and hexapyridine clusters [Mo6X8(Py-R)6][OSO2CF3]4 (X = Br or I) to cluster-cored organometallic stars, dendrons, and dendrimers

Hexasubstitution of apical triflate ligands in the octahedral clusters [M]2[Mo6X8(CF3SO3)6] (M = n-Bu4N or Cs, X = Br or I) and monosubstitution in [n-Bu4N]2[Mo6Br13(CF3SO3)] was carried out in tetrahydrofuran at 60 degrees C with simple pyridines and then extended to organometallic pyridines, yielding cluster-cored stars, and to dendronic polyallyl- and polyferrocenylpyridines, yielding cluster-cored polyallyl and polyferrocenyl dendrimers and dendrons. The orange pyridine-substituted clusters, whose pyridine protons are deshielded in 1H NMR (a practical tool for characterization), are air-stable and thermally stable with simple pyridines, light- and air-sensitive with organometallic pyridines, and air-fragile and thermally fragile with large dendronized pyridines.info:eu-repo/semantics/publishedVersio