Neuartige Cyclopentadienyl‐N‐silylphosphazen‐Komplexe der Seltenerdmetalle Yttrium und Lutetium

Abstract

We report the investigation of four new monoanionic cyclopentadienyl‐N‐silylphosphazene ligands [C5R4‐SiMe2‐NPR′3]– (CpSiNP–) 1–4. In this system the amido moiety of the classical dianionic chelate ligand (CpSiN2–) is displaced by an isoelectronic phosphazene donor function (CpSiNP–). The iminophosphorane‐functionalized tetramethylcyclopentadiene ligands have been prepared by the reaction of two equivalents of tris(tert‐butyl)iminophosphorane or tris(dimethylamino)iminophosphorane with tetramethyl or tert‐butyl‐substituted chlorodimethylsilyl‐1,3‐cyclopentadiene. The molecular structures of the protonated species of two representatives 1‐H and 2‐H were established by X‐ray diffraction analysis. Furthermore the metallation of the ligand [C5R4‐SiMe2‐NPtBu3]H (2‐H) was explored by the aryl elimination pathway using chelate stabilized arene complexes of rare‐earth metals (RE) [RE(dmba)3][RE = Y, Lu; (dmba–) = ortho‐metalated N,N‐dimethylbenzylamine]. The resulting cyclopentadienyl diaryl complexes of the type [(η5‐C5Me4‐SiMe2‐NPtBu3)RE(dmba)2] [RE = Y (5); Lu(6)] were completely characterized by NMR spectroscopy, elemental analysis and X‐ray diffraction analysis. The coordination number of the central atom in each case is nine. Five RE–C bonds to the Cp fragment, two RE–C bonds to the aryl‐carbon atom and two RE–N bonds to the chelating amino function are realized. The phosphazene unit with uncommonly large Si–N–P angles of 173° (5) and 166° (6) do not form a bond in terms of the Constrained‐Geometry ligand concept at least in these complexes. It seems that on the one hand the high coordination number and on the other hand the stable chelate structure of the coordinated amino‐aryl ligand is responsible for this result.

Phosphasalen Yttrium Complexes: Highly Active and Stereoselective Initiators for Lactide Polymerization

“…As a consequence, the 31 P{ 1 H} NMR spectrum of complex 1 in THF recorded on a 500 MHz instrument exhibits two signals of equal intensity, very close to each other (Figure ). These signals are not part of a doublet as they are separated by 25 Hz, which is significantly larger than previously reported 2 J YP coupling constants for similar complexes. ,− , When the spectrum was recorded on a lower frequency (300 MHz) instrument, the signals were not resolved and merged into a single broad signal.…”

“…These signals are not part of a doublet as they are separated by 25 Hz, which is significantly larger than previously reported 2 J YP coupling constants for similar complexes. 5a,12i−m, 14 When the spectrum was recorded on a lower frequency (300 MHz) instrument, the signals were not resolved and merged into a single broad signal.…”