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Simple Syntheses, Structural Diversity, and Tishchenko Reaction Catalysis of Neutral Homoleptic Rare Earth( II or III ) 3,5‐Di‐ tert ‐butylpyrazolates—The Structures of [Sc( t Bu 2 pz) 3 ], [Ln 2 ( t Bu 2 pz) 6 ] (Ln=La, Nd, Yb, Lu), and [Eu 4 ( t Bu 2 pz) 8 ]
Author(s) -
Deacon Glen B.,
Gitlits Alex,
Roesky Peter W.,
Bürgstein Markus R.,
Lim Kevin C.,
Skelton Brian W.,
White Allan H.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010105)7:1<127::aid-chem127>3.0.co;2-1
Subject(s) - homoleptic , chemistry , lanthanide , crystallography , stereochemistry , dimer , ion , metal , organic chemistry
The homoleptic rare‐earth pyrazolate complexes [Sc( t Bu 2 pz) 3 ], [Ln 2 ( t Bu 2 pz) 6 ] (Ln=La, Nd, Sm, Lu), [Eu 4 ( t Bu 2 pz) 8 ] and the mixed oxidation state species [Yb 2 ( t Bu 2 pz) 5 ] ( t Bu 2 pz=3,5‐di‐ tert ‐butylpyrazolate) have been prepared by a simple reaction between the corresponding rare‐earth metal and 3,5‐di‐ tert ‐butylpyrazole, in the presence of mercury, at elevated temperatures. In addition, [Yb 2 ( t Bu 2 pz) 6 ] was prepared by redox transmetallation/ligand exchange between ytterbium, diphenylmercury( II ) and t Bu 2 pzH in toluene, whilst the same reactants in toluene under different conditions or in diethyl ether gave [Yb 2 ( t Bu 2 pz) 5 ]. The complexes of the trivalent lanthanoids display dimeric structures [Ln 2 ( t Bu 2 pz) 6 ] (Ln=La, Nd, Yb, Lu) with chelating η 2 ‐terminal and η 2 : η 2 ‐bridging pyrazolate coordination. The considerably smaller Sc 3+ ion forms monomeric [Sc( t Bu 2 pz) 3 ] of putative D 3h molecular symmetry, with pyrazolate ligands solely η 2 ‐bonded. [Eu 4 ( t Bu 2 pz) 8 ] is a structurally remarkable tetranuclear Eu II complex with two types of europium centres in a linear array. The outer two are bonded to one terminal and two bridging pyrazolates, and the inner two are coordinated by four bridging ligands. Unprecedented μ ‐ η 5 : η 2 pyrazolate ligation is observed, with each outer Eu 2+ sandwiched between two η 5 ‐bonded pyrazolate groups, which are also η 2 ‐linked to an inner Eu 2+ . The two inner Eu 2+ ions are linked together by two equally occupied components of each of two symmetry related, disordered pyrazolate groups with one component η 4 : η 2 bridging and one η 3 : η 2 bridging. [La 2 ( t Bu 2 pz) 6 ] has also been shown to be a Tishchenko reaction catalyst with several organic substrates.