The internal functionalization of the Keplerate-type capsule Mo132 has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single-crystal X-ray diffraction analysis of the glutarate containing {Mo132 } species. A detailed NMR solution study of the ligand-exchange process allowed determining the binding constant KL of acetate (AcO(-) ), succinate (HSucc(-) ) or glutarate (HGlu(-) ) ligands at the 30 inner coordinating sites, which vary such as K AcO -
Scandium and yttrium amide complexes Ln{ONXO(R1,R2)}(N(SiHMe2)2)(THF)n (Ln = Sc, n = 0 or Y, n = 1; X = NMe2 or OMe; R(1) = Cumyl or p-Cl-Cumyl; R(2) = Me or Cumyl) were prepared by aminolysis of Ln[N(SiHMe2)2]3(THF) with the corresponding tetradentate diamino- or alkoxy-amino-bis(phenol) pro-ligands {ONXO(R1,R2)}H2. In the solid state and in toluene solution, the scandium complexes are monomeric and 5-coordinated, while the analogous yttrium complexes all bear an extra THF-coordinated molecule and are 6-coordinated. Sc{ONXO(R1,R2)}(N(SiHMe2)2) complexes are single-site initiators for the ring-opening polymerization (ROP) of racemic lactide but are less active than their yttrium analogues Y{ONXO(R1,R2)}(N(SiHMe2)2)(THF); also, in contrast to the latter ones, they are inactive in the ROP of the more demanding racemic β-butyrolactone. On the other hand, the scandium amide complexes feature a significantly improved control over the ROP of lactide, yielding PLAs with much narrower molecular weight distributions (Đ(M) < 1.1 for Sc vs. 1.5-2.0 for Y). The yttrium complex with the very bulky o,p-dicumyl-substituted ligand is more heteroselective than its scandium analogue (P(r) = 0.88 vs. 0.83), while the opposite is observed with complexes based on p-methyl-substituted ligands (P(r) = 0.50 in toluene or 0.72-0.75 in THF for Y vs. P(r) = 0.75-0.83 for Sc in toluene). These reactivity and selectivity trends are rationalized by a much more sterically crowded coordination sphere in scandium than in yttrium complexes.
The long diphosphine 5,11-diphenylphosphanyl-25,26-dipropyloxy-27,28-bis(2-propenyloxy) calix[4]arene (cone) (5), in which the two phosphorus atoms are separated by a semi-rigid linking unit, was prepared in four steps starting from calix[4]arene. Reaction of 5 with AuCl(SEt(2)) or [RuCl(2)(p-cymene)](2) led to calixarenes bearing two metallated pendant arms, [5·(AuCl)(2)] and [5·{RuCl(2)(p-cymene)}(2)], respectively. In the presence of AgBF(4) or [Ni(C(5)H(5))(1,5-cyclooctadiene)]BF(4), diphosphine 5 displayed a marked tendency to form oligomeric material, but under high dilution conditions dimeric species were obtained selectively. The inability of 5 to form chelate complexes was further illustrated by its reaction with [PdCl(2)(1,5-cyclooctadiene)(2)], which led quantitatively to a rare complex in which a diphosphine spans across the dinuclear [PdCl(μ-Cl)(2)PdCl] unit.
Keywords: Calixarenes / Diphosphane / Nickel / Silver / Chelates / Strained ligands 5,26,27,arene (6) (6)]BF 4 quantitatively. These complexes were both characterised by a singlecrystal X-ray diffraction study. In the nickel complex the ligand shows a bite angle of 104.5°, which lies in the range
A unique, covalently constructed capsular catalyst obtained by reaction of [Ni(η 5 -C 5 H 5 )(1,5-cyclooctadiene)] BF 4 with the double-calixarene-derived diphosphine 1,3-bis (5-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]aren-17-yl)- [a]
The cover picture shows the structure of a calix[4]arene‐based ligand with an unusually large bite angle. Calix[4]arenes constitute versatile macrocyclic compounds, which can be obtained by condensation of phenols with formaldehyde. The so‐called CALDIPs, which are diphosphanes built upon such a skeleton, have recently found applications in a variety of C–C bond‐forming reactions, including polymerisation reactions. In the presence of group 8–10 transition metals, CALDIP ligands form straightforwardly dynamic chelate complexes, in which the ligand bite angle undergoes periodic variation. In the article by C. Jeunesse, D. Matt et al. on p. 4917 ff, a new chelate complex is described in which a CALDIP ligand adopts an unexpectedly large bite angle of 139°, which thus illustrates the great flexibility of the calix[4]arene core. The key ligand is depicted as superimposed over the sky of Strasbourg city (photo courtesy of Dr. R. Ruppert, UdS). Phenol–formaldehyde condensation products were already synthesised in Strasbourg by A. Baeyer in 1872.
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