Contrasting Binding Modes in Lanthanoid Pyrazolate and Pseudo-pyrazolates Prepared by Oxidation of Lanthanoid(II) Complexes and Lanthanoid Metals with Thallium(I) Reagents

Abstract

Oxidation of Yb(C 5 Me 5 ) 2 with [Tl(Ph 2 pz)] and [Tl(azin)] (Ph 2 pz ) 3,5-diphenylpyrazolate, azin ) 7-azaindolate) yields [Yb(C 5 Me 5 ) 2 (Ph 2 pz)] (1) and [Yb(C 5 Me 5 ) 2 (azin)] (2). X-ray crystal structures of 1 and 2 reveal monomeric eight-coordinate complexes with η 2 -Ph 2 pz or azin ligands. Treatment of neodymium metal with [Tl(Ph 2 pz)] yields [Nd(Ph 2 pz) 3 (dme) 2 ] (3), which is a nine-coordinate monomer with three η 2 -pyrazolate ligands and a chelating and a unidentate dme ligand. Oxidation of Sm(C 5 Me 5 ) 2 with [Tl(1,4,2-P 2 SbC 2 Bu t 2 )]/[Tl(1,2,4-P 3 C 2 -Bu t 2 )] (approximately 4:1) gave a mixture of [Sm(C 5 Me 5 ) 2 (1,2,4-P 3 C 2 Bu t 2 )] (4) and [Sm(C 5 -Me 5 ) 2 (1,4,2-P 2 SbC 2 Bu t 2 )]. The former was shown to be a nine-coordinate monomer with novel pseudo-pyrazolate η 2 -(P 2 )-[1,2,4-P 3 C 2 Bu t 2 ] coordination of the triphosphacyclopentadienide ligand. After metathesis routes to Ln(1,4,2-P 2 SbC 2 Bu t 2 ) n complexes failed, redox transmetalation between ytterbium metal and [Tl(1,4,2-P 2 EC 2 Bu t 2 )] (E ) Sb, P) containing a substantial impurity of [Li(tmeda) 2 ][1,4,2-P 2 EC 2 Bu t 2 ] yielded the first lanthanoid diphosphastibacyclopentadienide complex in a mixture with [1,2,4-P 3 C 2 Bu t 2 ] species. An X-ray investigation of single crystals containing an isomerically diverse mixture enabled the structure of [Li(thf) 4 ]-[Yb(1,4,2-P 2 SbC 2 Bu t 2 ) 3 ] (5) to be determined, and it was shown to contain a π-η 2 and two η 5 -[1,4,2-P 2 SbC 2 Bu t 2 ] ligands. In the series 1, 4, and 5, the η 2 -ring varies from edge-on to side-on, reflecting a progression from σ to π coordination. [Li(tmeda) 2 ][1,4,2-P 2 SbC 2 Bu t 2 ] (6) has been successfully crystallized from a [Li(tmeda) 2 ][P 2 EC 2 Bu t 2 ] mixture and structurally characterized.

Diverse Heteroleptic Ytterbium(III) Thiocyanate Complexes by Oxidation from Bis(thiocyanato)ytterbium(II)

“…[17] This yields a value of 1.34 , which is within the range (1.31 ± 1.38 ) calculated for [Ln(Ph 2 pz) 3 L 2 ] (L thf, OPPh 3 ) complexes, [31] although a considerably smaller value (1.26 ) is obtained for the heteroleptic complex [Yb (C 5 Me 5 ) 2 (Ph 2 Pz)]. [38] In 4 and 6 there is a pronounced lengthening of the YbÀO(thf) bond length for the THF ligand trans to the A ligand compared with those of the mutually trans THF ligands (Tables 3 and 4). The YbÀO(thf) bond lengths of [Yb(NCS) 3 (thf) 4 ] display analogous behaviour.…”

“…which represents a rare example of a functionalised pyrazolatolanthanoid complex (see also [Yb (C 5 Me 5 ) 2 (Ph 2 pz)] [38] ).…”

Synthesis and structural characterisation of lanthanide and actinide phosphaorganometallic complexes derived from the 3,5-di-tert-butyl-1,2,4-triphospholyl ring anion, P3C2But−2: Crystal and molecular structures of [M(η5-P3C2But2)2(η2-P3C2But2)] (M=Sc, Y, Tm, and U)

“…The unusual g 2 -(bent) bonding of one of the P 3 C 2 Bu t 2 rings observed in complexes 1-4 is of interest and is similar to that reported by Deacon et al [35] for both the triphospholyl compound [Sm(g 5 -C 5 Me 5 ) 2 (g 2 -P 3 C 2 Bu t 2 )THF] and the stibadiphospholyl salt [Li(THF) 4 ][Yb(g 5 -P 2 SbC 2 Bu t 2 ) 2 (g 2 -P 2 SbC 2 Bu t 2 )]. These authors attributed the structural differences between the triphospholyl and stibadiphospholyl complexes and the corresponding Ph 2 (pyrazolyl) compounds (which involves largely r-ring bonding) to the increasingly diffuse nature of the lone pairs of the heavier hetero-atoms in the sequence N, P, Sb which makes …”

Lewis‐Acid Stabilized Organoimide Complexes of Divalent Samarium, Europium, and Ytterbium

“…The feasibility of such thermally stable divalentl anthanide imides prompted us to further investigate into their redox chemistry.I np revious studies 1e À -oxidation agents, such as halogenating agents, [40] organothallium, [47] or organolead [48,49] compounds have been used for Ln II -to-Ln III conversions. As half-sandwich Ln III imide complexeso ft he type [Cp*Ln(NR)] (Cp* = C 5 Me 5 )p ose attractive targetc ompounds, we were par-ticularlyi nterested in reagents capable of oxidative Cp* ligand transfer.Similar to organothallium(I) compounds, organolead(II) compounds can act as such oxidation and ligand transfer reagents, [47] which is also demonstrated by their redox potentials of Tl I /Tl 0 À0.34 Va nd Pb II /Pb 0 À0.13 V( PbSO 4 /Pb 0 ,S O 4 2À at À0.36 V). [50] This redox protocol has already provenv iable for the efficient synthesis of homoleptic Cp* 3 Sm [48] and [C 5 H 3 (SiMe 3 ) 2 ] 3 Yb, [49] both prepared from the corresponding divalents andwich complexes and the respective plumbocene derivative.…”