Facile Pyrazolylborate Ligand Degradation at Lanthanide Centers:  X-ray Crystal Structures of Pyrazolylborinate-Bridged Bimetallics

Abstract

Adventitious hydrolysis of a number of different complexes with the molecular formula Ln(Tp(Me2))(2)X [Tp(Me2) = (HB(dmpz)(3)), where X is a basic anionic ligand] in various solvents, yielded crystals of highly insoluble dimers of the general formula [Ln(Tp(Me2))(mu-BOp(Me2))](2) (1) [Ln = La, Ce, Sm; BOp(Me2) = (HBO(dmpz)(2))(2)(-); dmpzH = 3,5-dimethylpyrazole]. The results of several single-crystal X-ray determinations are reported. One metal nitrogen distance, that lying across from the two negatively charged bridging oxygen atoms, is 0.06 A longer than the others, suggesting an unusual trans influence at a lanthanide center. The formation of 1 is proposed to involve the intermediacy of Ln(Tp(Me2))(2)OH formed by protonolysis with adventitious water.

Potential Precursors for Terminal Methylidene Rare‐Earth‐Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand

“…Although compound 9‐Lu is stable in solution in [D 6 ]benzene at ambient temperature, heating to 40 °C for 4 h also led to degradation of the ancillary ligand, as did the utilization of various donors. In accordance with other already reported degradation processes, we assume C−H‐bond activation of one tert ‐butyl group or B−N bond cleavage to be responsible for the formation of multiple unidentified metal complexes in these reaction mixtures . It is also noteworthy, that the di(chlorido) derivative [Tp t Bu,Me LuCl 2 ] ( 5‐Lu ) does not undergo any “Tebbe‐like” reaction with AlMe 3 at ambient temperature, but leads to unidentified complicated reaction mixtures (ancillary ligand degradation) at elevated temperatures ( T =50 °C).…”

Synthesis and Reactivity of a Cerium(III) Scorpionate Complex Containing a Redox Non-Innocent 2,2′-Bipyridine Ligand

“…At both temperatures saturation was not reached at the maximum obtainable field, and this was observed reproducibility on separate samples, consistent with a system containing two unpaired electrons. There is also an essentially linear relationship of M and H from 35,000-70,000 Oe (M = 0.50 μB at 70,000 Oe) with ∂M/∂H for this range of fields lower than for the corresponding data at 5 K. , and a mechanism for this decomposition was postulated whereby dmpzH was generated [37]. As no other products could be identified during the formation of 3 it is not certain if the oxygen atom derives from initial coordination of the N-oxide or adventitious O2/H2O; however the isolation of 3 was reproducible, performed with the strict exclusion of oxygen and water, and was formed in higher yields than previously reported.…”

“…Whilst the solid state structure of 3 was obtained previously by Sella, no other characterization data were reported [37]; therefore we acquired elemental analysis and collected spectroscopic data for 3. Unusually in the original report 3 was reported to exhibit a dark red color [37], whilst the samples we obtained were pale yellow.…”

Hydrolysis of a (2‐Propanol)yttrium Triiodide Complex in the Presence of Glymes: Synthesis and X‐ray Structures of Hydroxo‐Bridged Dinuclear Yttrium Complexes and Their Applications in Materials Science

“…[3] Hydroxo complexes are also often proposed as intermediates in the degradation pathways of f-element organometallic and coordination compounds. [4] Polynuclear oxo and/or hydroxo complexes of lanthanides with [Ln 4 (µ 3 -OH) 4 ] 8+ , [5] [Ln 6 (µ 6 -O)(µ 3 -OH) 8 (H 2 O) 24 ] 8+ , [6] or [Ln 15 (µ 3 -OH) 20 (µ 5 -X)] 24+ [7] (X = halide) cores have been obtained by direct hydrolysis of lanthanide nitrates, perchlorates, or halides (chloride and iodide) in aqueous media. However, the high charge and polarizing power of lanthanides as well as the absence of any organic auxiliary ligands result in a high tendency to readily hydrolyze, thus making it difficult to control oligomerization of rare-earth centers.…”

“…[8] A common synthetic strategy for controlling the advancement of hydrolysis is to introduce auxiliary ligands such as carboxylates, polyketonates, polyamines, polyols, pyridonates, alkoxides, and amino acids in the metal coordination sphere (ligand-controlled hydrolysis). [9] We have previously reported octa-and nonanuclear oxo-hydroxo yttrium species, namely [Y 8 (µ 4 -O) 2 -(µ 3 -OH) 4 (µ,η 2 -AAA) 4 (η 4 -AAA) 6 (µ-OEt) 4 (µ 3 -OEt) 2 ] [10] and [Y 9 O 2 (OH) 8 (µ,η 2 -AAA) 8 (η 2 -AAA) 8 ] -, [11] using allylacetatoacetate MeCOCH 2 COOCH 2 CH=CH 2 (HAAA) as an auxiliary ligand. Scheme 1.…”