Effect of high external pressures on the vibrational spectra of Zeise’s complexes, K[Pt(η-C2H4)Cl3] and [Pt(η-C2H4)Cl2]2

The pressure dependences (dν/dP) of the main IR and Raman bands of Zeise’s complexes, K[Pt(η²-C₂H₄)Cl₃] and [Pt(η²-C₂H₄)Cl₂]₂, have been determined for the first time for selected pressures up to ∼33 kbar with the aid of diamond-anvil cells. Neither complex undergoes a pressure-induced structural change throughout the pressure range investigated. The dν/dP values range from −0.13 to 0.79 cm⁻¹ kbar⁻¹. The negative values have proved particularly informative in identifying the location of the CC stretching modes of the Pt-ethylene groups, a topic of considerable disagreement in the literature.     

Thermal isomerizations of 1-(13)c-2,2,3,3-d(4)-cyclopropane to isotopically labeled trimethylene diradicals, 1-propylidenes, and propenes

The gas-phase thermal isomerizations of 1-13C-2,2,3,3-d4-cyclopropane lead to isotopically labeled propenes characteristic of both the traditional reaction mechanism involving a trimethylene diradical intermediate and a previously predicted, but never observed, path involving rate-limiting conversion of the cyclopropane to singlet 1-propylidenes, followed by a [1,2]-deuterium shift. The isomerizations give mixtures of both 1-13C-2,3,3,3-d4-propene and 1-13C-1,2,3,3-d4-propene, products characteristic of the two mechanisms that are clearly observable by 13C{1H} NMR spectroscopy.     

Addition curing thermosets endcapped with 4-amino [2.2] paracyclophane

A new family of addition curing polyimides were prepared that contained 4-amino [2.2]-paracyclophane as the endcap. An improved synthesis of the endcap 4-amino-[2.2] cyclophane was accomplished increasing the yield to 60% and simplifying the procedure. DSC and rheological analysis of endcapped polyimide oligomers confirmed that the onset for polymerization of the ethylene bridge was 250°C. ¹³C CP/MAS NMR was used to determine the structural changes of the oligomers after thermal treatment. The cyclophane capped polyimides were successfully compression molded to from void free neat resin specimens. T'_gs as high as 353°C were obtained by thermomechanical analysis for postcured samples. Preliminary thermal stability studies (TGA) suggest that these resins have a high onset of decomposition ranging from 549 to 567°C.     

Categoricity,amalgamation, and tameness

Theorem: For each 2 ≤ k < ω there is an -sentence ϕ_k such that (1) ϕ_k is categorical in μ if μ≤ℵ_k−2; (2) ϕ_k is not ℵ_k−2-Galois stable (3) ϕ_k is not categorical in any μ with μ>ℵ_k−2; (4) ϕ_k has the disjoint amalgamation property (5) For k > 2 (a) ϕ_k is (ℵ₀, ℵ_k−3)-tame; indeed, syntactic first-order types determine Galois types over models of cardinality at most ℵ_k−3; (b) ϕ_k is ℵ_m-Galois stable for m ≤ k − 3 (c) ϕ_k is not (ℵ_k−3, ℵ_k−2). The first author is partially supported by NSF grant DMS-0500841.