Contrasting binding modes in lanthanoid pyrazolate and pseudo-pyrazolates prepared by oxidation of lanthanoid(II) complexes and lanthanoid metals with thallium(I) reagents

Citation
Gb. Deacon et al., Contrasting binding modes in lanthanoid pyrazolate and pseudo-pyrazolates prepared by oxidation of lanthanoid(II) complexes and lanthanoid metals with thallium(I) reagents, ORGANOMETAL, 19(9), 2000, pp. 1713-1721
Citations number
56
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
ORGANOMETALLICS
ISSN journal
0276-7333 → ACNP
Volume
19
Issue
9
Year of publication
2000
Pages
1713 - 1721
Database
ISI
SICI code
0276-7333(20000501)19:9<1713:CBMILP>2.0.ZU;2-2
Abstract
Oxidation of Yb(C5Me5)(2) with [Tl(Ph(2)pz)] and [Tl(azin)] (Ph(2)pz = 3,5- diphenylpyrazolate, azin = 7-azaindolate) yields [Yb(C5Me5)(2)(Ph(2)pz)] (1 ) and [Yb(C5Me5)(2)(azin)] (2). X-ray crystal structures of 1 and 2 reveal monomeric eight-coordinate complexes with eta(2)-Ph(2)pz or azin ligands. T reatment 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 y2-pyrazolate ligand s and a chelating and a unidentate dme ligand. Oxidation of Sm(C5Me5)(2) wi th [Tl( 1,4,2-P2SbC2Bu2t)/[Tl(1,2,4-P3C2-Bu-2(t))] (approximately 4:1) gave a mixture of [Sm(C5Me5)(2)(1,2,4-P3C2Bu2t)] (4) and [Sm(C-5-Me-5)(2)(1,4,2 -P2SbC2Bu2t)]. The former was shown to be a nine-coordinate monomer with no vel pseudo-pyrazolate eta(2)-(P-2)-[1,2,4-P3C2Bu2t] coordination of the tri phosphacyclopentadienide ligand. After metathesis routes to Ln(1,4,2-P2SbC2 Bu2t)(n) complexes failed, redox transmetalation between ytterbium metal an d [Tl( 1,4,2-P2EC2Bu2t) (E = Sb, P) containing a substantial impurity of [L i(tmeda)(2)][1,4,2-P2EC2Bu2t] yielded the first lanthanoid diphosphastibacy clopentadienide complex in a mixture with [1,2,4-P3C2Bu2t] species. An X-ra y investigation of single crystals containing an isomerically diverse mixtu re enabled the structure of[li(thf)(4)]-[Yb(1,4,2-P2SbC2Bu2t)(3)] (5) to be determined, and it was shown to contain a pi-eta(2) and two eta(5)-[1,4,2- P2SbC2Bu2t] ligands. In the series 1, 4, and 5, the eta(2)-ring varies from edge-on to side-on, reflecting a progression from sigma to pi coordination . [Li(tmeda)(2)][1,4,2-P(2)SbC(2)But(2)(t)] (6) has been successfully cryst allized from a [Li(tmeda)(2)][P2EC2Bu2t] mixture and structurally character ized.