Vesicles formed in water by synthetic macro-amphiphiles have attracted much attention as nanocontainers having properties that extend the physical and chemical limits of liposomes. We sought to develop ABA block copolymeric amphiphiles that self-assemble into unilamellar vesicles that can be further oxidatively destabilized. We selected poly(ethylene glycol) (PEG) as the hydrophilic A blocks, owing to its resistance to protein adsorption and low toxicity. As hydrophobic B blocks, we selected poly(propylene sulphide) (PPS), owing to its extreme hydrophobicity, its low glass-transition temperature, and most importantly its oxidative conversion from a hydrophobe to a hydrophile, poly(propylene sulphoxide) and ultimately poly(propylene sulphone). This is the first example of the use of oxidative conversions to destabilize such carriers. This new class of oxidation-responsive polymeric vesicles may find applications as nanocontainers in drug delivery, biosensing and biodetection.

The five-coordinate complexes of the type [RuCl(PNNP)]PF 6 (PNNP ) tetradentate ligand with a P 2 N 2 donor set) are prepared by chloride abstraction from [RuCl 2 (PNNP)]. A mixture of ∆-cis-β-and Λ-cis-β-[RuCl 2 (1a-κ 4 P,N,N,P)] (2a; 1a ) N, N′-bis[o-(diphenylphosphino)benzylidene]-2,2′-diimino-1,1′-(S)-binaphthylene), prepared by reaction of 1a with [RuCl 2 -(PPh 3 ) 3 ], reacts with Tl[PF 6 ], giving the five-coordinate [RuCl(1a-κ 4 P,N,N,P)]PF 6 (3a). The related trans-[RuCl 2 (1b-κ 4 P,N,N,P)] (2b; 1b ) N, N′-bis[o-(diphenylphosphino)benzylidene]-(1S,2S)-diiminocyclohexane) reacts with Tl[PF 6 ] to give [RuCl(1b-κ 4 P,N,N,P)]PF 6 (3b). With the amino ligand N, N′-bis[o-(diphenylphosphino)benzylidene]-(1S,2S)-diaminocyclohexane (1c), the aqua complex [RuCl(OH 2 )(1c-κ 4 P,N,N,P)]PF 6 (5c) is obtained by reaction of Tl-[PF 6 ] with [RuCl 2 (PPh 3 )(1c-κ 3 P,N,N)] (4), which has been isolated and structurally characterized. The reactivity of the five-coordinate 2b with CO and oxygen donors such as water, Et 2 O, THF, and methanol is reported. Both 3 and 5 catalyze the asymmetric epoxidation of olefins with hydrogen peroxide as oxidant. Enantiomeric excesses up to 42% were obtained in the enantioselective epoxidation of styrene and of other unfunctionalized olefins. The reaction is highly stereospecific, as the epoxidation of (Z)-2-methylstyrene gives a cis:trans ratio of 99:1.

With personal pleasure, we dedicate this Perspective to the memory of Luigi M. Venanzi, who, apart from his many scientific contributions, was a major promotor of NMR spectroscopy within the Swiss and international Inorganic Chemistry communities.Diffusion data from pulsed-field gradient spin-echo (PGSE) methods are shown to be qualitatively useful in the investigation of problems involving unknown molecular aggregation and/or the nature of inter-ionic interactions in metal complexes. For charged species possessing anions such as PF À 6 , BF À 4 , CF 3 SO À 3 or BArF À , both 19 F-and 1 H-PGSE methods offer a valid alternative and, sometimes, unique view of gross and subtle solution molecular structure and dynamics. Problems associated with solvents, concentration, and reproducibility are discussed.1. Introduction. ± Although organometallic chemistry (and especially homogeneous catalysis) continues to move from strength to strength [1 ± 5], the applications of modern NMR methods in these areas have lagged somewhat behind. Slowly, but surely, three-dimensional structures are being solved with NOE-and ROE-NMR methods [6 ± 9]; nevertheless, there are areas, e.g., determining molecular size, aggregation, and/ or the nature of interionic interactions, where NMR spectroscopic possibilities have not been sufficiently explored.A promising NMR method involves the use of pulsed-field gradient spin-echo (PGSE) experiments [10], which can measure the diffusion coefficients of molecules and thus provide information on particle size. PGSE Methods were introduced in 1965 by Stejskal and co-workers [11] [12] and, since then, have been widely used. In the 1970s, this approach was used to determine diffusion coefficients of organic molecules [13]. In the following decade, variants of this technique have been applied to problems in polymer chemistry [14]. Recently, diffusion data on dendrimers [15 ± 20] and peptides [21 ± 24] as well as on molecules in various environments, e.g., in porous silica [25], and zeolites [26], have been obtained. However, there are very few applications of PGSE methods in coordination and/or organometallic chemistry [27 ± 35].In an interesting and recent application, Beck et al. [27] have studied the polymerization catalyst precursors 1 ± 5. Their results prompted the authors to suggest that these zirconium complexes can exist as ion-quadruples in the presence of a boronbased cocatalyst. In their construction of novel Pt-molecules, Olenyuk et al. [28] employed diffusion data to support a self-assembled dodecahedron structure of the product of the reaction shown in the Scheme. In a bio-inorganic application, Gorman et al.[15] estimated the hydrodynamic radii of the iron-sulphur based dendrimers, abbreviated below, using PGSE studies. These three examples are impressive as much for their scarcity as for their elegance.

New Pd(0) olefin complexes, 2−5, of a binaphthalene-based chiral P,N(oxazoline) auxiliary, (S,R)-2-[4-(isopropyl)oxazol-2-yl]-2‘-diphenylphosphino-1,1‘-binaphthyl, 1, have been prepared (olefin = fumaronitrile, maleic anhydride, 4-cyclopentene-1,3-dione, and dibenzylideneacetone). These compounds reveal different dynamic behavior in solution as shown by 2-D exchange spectroscopy. Ligand 1 affords excellent enantioselectivity (up to 99% ee) in the allylic amination of a 1,3-diphenyl allyl precursor. The solid-state structure of [Pd(η3-PhCHCHCHMe)(1)]OTf, 15, has been determined and shows two different diastereomeric cations within one unit cell; that is both the si and re faces of the allyl crystallize together, the first example of this for a moderately large allyl ligand. The structure of PdCl2(1) is also reported and reveals (as does that for 15) that the oxazoline ring of 1 is twisted relative to the P−Pd−N coordination plane, thus placing this ring substituent above and not below the coordination plane. A more exact solid-state structure for Pd2(dba)3 has been determined.