TY - JOUR
T1 - 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(tBu2pz)3], [Ln2(tBu2pz)6] (Ln = La, Nd, Yb, Lu), and [Eu4(tBu2pz)8]
AU - Deacon, Glen B.
AU - Gitlits, Alex
AU - Roesky, Peter W.
AU - Bürgstein, Markus R.
AU - Lim, Kevin C.
AU - Skelton, Brian W.
AU - White, Allan H.
PY - 2001/1/5
Y1 - 2001/1/5
N2 - The homoleptic rare-earth pyrazolate complexes [Sc(tBu2pz)3], [Ln2(tBu2pz)6] (Ln = La, Nd, Sm, Lu), [Eu4(tBu2pz)8] and the mixed oxidation state species [Yb2(tBu2pz)5] (tBu2pz = 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, [Yb2(tBu2pz)6] was prepared by redox transmetallation/ligand exchange between ytterbium, diphenyl-mercury(II) and tBu2pzH in toluene, whilst the same reactants in toluene under different conditions or in diethyl ether gave [Yb2(tBu2pz)5]. The complexes of the trivalent lanthanoids display dimeric structures [Ln2(tBu2pz)6] (Ln = La, Nd, Yb, Lu) with chelating η2-terminal and η2:η2-bridging pyrazolate coordination. The considerably smaller Sc3+ ion forms monomeric [Sc(tBu2pz)3] of putative D3h molecular symmetry, with pyrazolate ligands solely η2-bonded. [Eu4(tBu2pz)8] is a structurally remarkable tetranuclear EuII 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-η5:η2 pyrazolate ligation is observed, with each outer Eu2+ sandwiched between two η5-bonded pyrazolate groups, which are also η2-linked to an inner Eu2+. The two inner Eu2+ ions are linked together by two equally occupied components of each of two symmetry related, disordered pyrazolate groups with one component η4:η2 bridging and one η3:η2 bridging. [La2-(tBu2pz)6] has also been shown to be a Tishchenko reaction catalyst with several organic substrates.
AB - The homoleptic rare-earth pyrazolate complexes [Sc(tBu2pz)3], [Ln2(tBu2pz)6] (Ln = La, Nd, Sm, Lu), [Eu4(tBu2pz)8] and the mixed oxidation state species [Yb2(tBu2pz)5] (tBu2pz = 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, [Yb2(tBu2pz)6] was prepared by redox transmetallation/ligand exchange between ytterbium, diphenyl-mercury(II) and tBu2pzH in toluene, whilst the same reactants in toluene under different conditions or in diethyl ether gave [Yb2(tBu2pz)5]. The complexes of the trivalent lanthanoids display dimeric structures [Ln2(tBu2pz)6] (Ln = La, Nd, Yb, Lu) with chelating η2-terminal and η2:η2-bridging pyrazolate coordination. The considerably smaller Sc3+ ion forms monomeric [Sc(tBu2pz)3] of putative D3h molecular symmetry, with pyrazolate ligands solely η2-bonded. [Eu4(tBu2pz)8] is a structurally remarkable tetranuclear EuII 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-η5:η2 pyrazolate ligation is observed, with each outer Eu2+ sandwiched between two η5-bonded pyrazolate groups, which are also η2-linked to an inner Eu2+. The two inner Eu2+ ions are linked together by two equally occupied components of each of two symmetry related, disordered pyrazolate groups with one component η4:η2 bridging and one η3:η2 bridging. [La2-(tBu2pz)6] has also been shown to be a Tishchenko reaction catalyst with several organic substrates.
KW - Catalysts
KW - Lanthanides
KW - N ligands
KW - Pyrazolates
KW - Rare-earth metals
KW - Structure elucidation
UR - http://www.scopus.com/inward/record.url?scp=0035808350&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0035808350
SN - 0947-6539
VL - 7
SP - 127
EP - 138
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 1
ER -