Yttrium and Neodymium Di- and Monohalide Complexes Based on Scorpionate (Poly(pyrazolyl)borate) Ligands

• Published in: Inorganic chemistry Vol. 39; no. 20; pp. 4476 - 4487
• Main Authors: Long, David P, Chandrasekaran, A, Day, Roberta O, Bianconi, Patricia A, Rheingold, Arnold L
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.10.2000
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic991179l

The syntheses of a series of well-characterized complexes of the type TpRYX2(solvent) n (1 and 2, R = H, X = Br, Cl, solvent = THF, n = 2; 4, R = Me, X = Cl, solvent = THF, n = 1; 5, R = Me, X = Cl, solvent = 3,5-dimethylpyrazole, n = 1; 7, R = Ph, X = Cl, solvent = THF, n = 1) and the novel solvent-free bis(poly(pyrazolylborate) complexes [(TpR)(BpR‘)YX] (8, R = R‘ =Me, X = Cl; 9, R = H, R‘ = Ph, X = Br) are presented. The data demonstrate that the steric, dynamic, and coordination behavior of these complexes are heavily influenced by the choice of scorpionate ligand substituents, showing the versatility of this ligand system for catalyst design. The coordinated THF solvent molecules of complexes 1, 2, and 4 are seen to undergo a dynamic solvation/desolvation equilibrium in solution that is fast on the NMR time scale. The position of this equilibrium is solvent-dependent and can be evaluated in complex 4 by observation of the line broadening of the 3-methyl resonance in the 1H NMR spectra taken in different deuterated solvents. Complex 5, formed by slow hydrolysis of 4, has been characterized by an X-ray diffraction structure determination and shown to adopt a distorted octahedral geometry that is thought to be similar to that of complex 4. The Nd analogues of these complexes (3, R = H, X = I, solvent = THF, n = 2; 6, R = Me, X = I, solvent = THF, n = 1) have been characterized by X-ray diffraction structure determinations:  3 shows a distorted capped octahedral structure, and 6 a distorted octahedral structure similar to that of 5. The solvent-free complex 8 is shown by 1H and 13C NMR spectroscopic analysis to be nonfluxional in solution on the NMR time scale, although 9 appears able to weakly coordinate solvents containing donor groups such as halides.