Über P?P–haltige cyclische Verbindungen. I

Die Umsetzung von N?N’?-Dimethylthioharnstoff mit PCl₃ führt zur cyclischen Verbindung I mit einer direkten Phosphor—Phosphor-Bindung. Die neue Verbindung ist durch ihre ³¹P- und ¹H-NMR-Spektren, das Schwingungs- und Massenspektrum und durch eine Röntgenstrukturanalyse charakterisiert. On P? P Containing Cyclic Compounds. I Reaction of N?N’?-dimethylthiourea with PCl₃ yields the cyclic compound I with a direct phosphorus—pphosphorus bond. The new compound is characterized by its ³¹P- and ¹H-nmr spectra, the vibration and mass spectra and an X-ray structural analysis.     

Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for Alternating Copolymerization of Epoxide and CO2: Telomerization Controlled by Carboxylate Anions

A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare‐earth metals was prepared and structurally characterized. The LaZn₃ system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO₂ with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn₃ system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h^?1. NMR analysis of the complex and end‐group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO₂.     

Phenylphosphonsäure-bis(methylamid) und seine Reaktionen mit Phosphor(III)-Halogeniden

Phenyl Phosphonic Bis(methylamide) and its Reactions with Phosphorus (III) Halides Preparation of phenyl phosphonic bis(methylamide), I , from phenyl phosphonic dichloride and methylamine is described. I is characterized by its nmr, mass, and vibration spectra and by its reactions with PCl₃, CH₃PCl₂, and C₆H₅PCl₂. The two reactions mentioned last yield C₆H₅P(O)[N(CH₃)P(CH₃)Cl]₂ ( IIIa ) and C₆H₅P(O)[N(CH₃)P(C₆H₅)Cl]₂ ( IIIb ), respectively.     

Markoff triples and quasifuchsian groups

We study the global behaviour of trees of Markoff triples overthe complex numbers. We relate this to the space of type-preservingrepresentations of the punctured torus group into SL(2,C). Inparticular, we explore which Markoff triples correspond to quasifuchsianrepresentations. We derive a variation of McShane's identityfor quasifuchsian groups. In the case of non-discrete representations,we attempt to relate the asymptotic behaviour of Markoff triplesto the realisability of laminations in hyperbolic 3-space. Wealso consider how some of these issues might be related formore general surfaces. 1991 Mathematics Subject Classification:57M50.