BASE-FREE TRIS(INDENYL)LANTHANOID(III) COMPLEXES (LN = LA, PR, ND, SM) - SOLID-STATE STRUCTURE AND SOLUTION NMR NIR VIS SPECTROSCOPY/

Strictly base-free, well-crystallized [M(C9H7)(3)] (C9H7 = indenyl) wi th M = Nd 3, Pr 4 and La 5 was probably prepared for the first time fr om the corresponding tetrahydrofuran adducts, [M(C9H7)(3). THF]. Accor ding to X-ray crystallographic studies, the crystal parameters and mol ecular conformations of 3, 4 and 5 differ from those already reported for the homologues with M = Sm 1 and U 2. While the conformation of th e isostructural complexes 3 and 4 remains, nevertheless, reminiscent o f that of 2, the molecular architecture of 5 is, at least at lower tem perature, notably different and more similar to that of some earlier r eported Lewis base (L) adducts, [Ln(C9H7)(3). L]. Actually, 5 consists of infinite, polymeric zigzag chains, eta(5)-C9H7)(2)(mu-eta(1):eta(5 )-C9H7)](infinity), owing to one relatively short intermolecular La... C' contact of 309.7(4) pm. While crystalline 4 involves isolated molec ules, variable-temperature H-1-NMR spectra suggest that, inter alia, i n C6D5CD3 and CD2Cl2 solution short-lived oligomeric species compete i ncreasingly in concentration with the monomer as the temperature is lo wered. (C) 1998 Elsevier Science S.A. All rights reserved.