Journal article

Authors list: Quitmann, CC; Bezugly, V; Wagner, FR; Müller-Buschbaum, K

Publication year: 2006

Pages: 1173-1186

Journal: Journal of Inorganic and General Chemistry

Volume number: 632

Issue number: 7

ISSN: 0044-2313

DOI Link: https://doi.org/10.1002/zaac.200500426

Publisher: Wiley

Abstract: 
Solvent free high-temperature oxidations of rare earth metals with the heterocycle pyrazole as well as in low to non-coordinating solvents were investigated to isolate intermediate stages between monomeric and polymeric pyrazolates of the lanthanides. Reaction conditions were tuned according to simultaneous DTA/ TG and temperature dependent X-ray powder diffraction experiments on known monomeric and polymeric pyrazolates, that gave rise to the idea that further structure intermediates could be isolated. Reactions in 1,2,3,4-tetrahydroquinoline gave the dimeric complex [Gd-2(PZ)(6)(PzH)(4)](PzH)(Tech) (1) as well as the triangular complex [Nd-3(Pz)(9)(PzH)(2)(PzH)(Tech)(2) (2). The solvent free melt synthesis resulted in a new polymeric form of (1)(infinity)[Eu(PZ)2(PzH)21 (3) (pyrazole, PzH = C3H3NNH; pyrazolate anion, Pz(-) = C3H3NN-; 1,2,3,4-tetrahydroquinoline, Tech = C9H13N). All three compounds contain coordinating pyrazolate amide groups and pyrazole molecules the latter decreasing in numbers upon condensation of the building units. According to simultaneous DTA/TG/MS investigations the condensation process can be identified with the release of pyrazole molecules.1 consists of dimeric molecules containing trivalent gadolinium, with a C.N. of eight. The two gadolinium atoms show different coordination polyhedra. Only a coordination and bridging is found for 1.2 consists of trimeric molecules containing trivalent neodymium. The neodymium atoms also exhibit different coordination polyhedra with C.N.s of eight and nine. Both pi and sigma coordination is found for 2, the it coordinating pyrazolate ligands acting as lids of the triangular units. Topological analysis of the electron localization function (ELF) for 2 calculated at the scalar-relativistic DFT level reveals only weakly covalent R donor eta(5)-Pz-Nd interactions compared to the stronger covalent a donor Pz-Nd interactions. The topological analysis of both, the ELF and the electron density reveals no significant differences of the respective charges of the Nd atoms. 3 exhibits a one-dimensional chain structure with Eau and a C.N of ten. It can thus be addressed the P form of the referring formula with a new arrangement of the coordinating ligands. Like the a form 3 shows a and pi coordination of pyrazole and pyrazolate ligands. Simultaneous DTA/TG analysis reveals that the low-temperature a form shows a phase transition into the beta form between 110 degrees C and 130 degrees C. The three compounds were investigated by low-temperature single crystal X-ray analysis, Mid IR and Far IR spectroscopy.

Harvard Citation style: Quitmann, C., Bezugly, V., Wagner, F. and Müller-Buschbaum, K. (2006) Condensation of rare earth pyrazolates: The dimeric, trimeric and polymeric units [Gd-2(Pz)(6)(PzH)4], [Nd-3(Pz)(9)(PzH)(2)] and (1)(infinity)[EU(Pz)(2)(PzH)(2)], Zeitschrift für anorganische und allgemeine Chemie = Journal of Inorganic and General Chemistry, 632(7), pp. 1173-1186. https://doi.org/10.1002/zaac.200500426

APA Citation style: Quitmann, C., Bezugly, V., Wagner, F., & Müller-Buschbaum, K. (2006). Condensation of rare earth pyrazolates: The dimeric, trimeric and polymeric units [Gd-2(Pz)(6)(PzH)4], [Nd-3(Pz)(9)(PzH)(2)] and (1)(infinity)[EU(Pz)(2)(PzH)(2)]. Zeitschrift für anorganische und allgemeine Chemie = Journal of Inorganic and General Chemistry. 632(7), 1173-1186. https://doi.org/10.1002/zaac.200500426