Low co-ordination numbers in lanthanoid and actinoid compounds. Part 2. Syntheses, properties, and crystal and molecular structures of triphenylphosphine oxide and peroxo-derivatives of [bis(trimethylsilyl)-amido]lanthanoids

Abstract

The preparation, properties, and n.m.r. spectra of 1 : 1 triphenylphosphine oxide adducts of [M{N(SiMe,),),] ( M = La, Eu, or Lu) and dimeric peroxo-species [M2(N(SiMe,)2),( 02)(PPh,0)2] ( M = La, Pr. Sm. Eu. or Lu) are described. The crystal and molecular structures of [La{N(SiMe,),),( PPh,O)] (1 ) and [La,{N(SiMe,),),-(0,) (PPh,O),](2) have been determined bysingle-crystal X-ray diffraction methodsfrom data measured on a manual diffractometer and refined by least-squares to R 0.1 16 for 2 770 observed reflections for (1 ) and to R 0.1 1 3 for 2 153 data for (2). Both species crystallise in space group P i with cell parameters : ( 1) ; a = 19.92, b = 12.64, c = 12.48& a = 120.5, (3 = 87.3, y = 102.7O.Z = 2; (2) ; a = 13.55, b = 1 8 . 5 4 , ~ = 12.54A, a = 90.8, f3 = 121.7, y = 115.3", Z = 1. Complex ( 1) is monomeric and the lanthanum atom has slightly distorted LaN,O tetrahedral geometry. TheLa-O-P unit is almost linear, with La-0 2.39(2) A ; La-N distances are 2.38(2)-2.41(2) A.Complex ( 2) is a peroxo-bridged centrosymmetric dimer in which the peroxo-function acts as a symmetrical doubly bidentate bridge linking two La{N(SiMe,),}, (PPh,O) units. The metal atom can again be considered to have distorted tetrahedral co-ordination if the 0, function is assumed to occupy one co-ordination site. The La-O(0,) distances are both 2.33(3) 8. whilst La-O(PPh,O) is 2.42(2) and La-N 2.37(2) and 2.49(3) A. The 0-0 separation is 1.65(4) 8, but this may be artificially lengthened by the effects of crystal decomposition.

Synthesis and Structural Characterization of Several Ytterbium Bis(trimethylsilyl)amides Including Base-free [Yb{N(SiMe3)2}2(μ-Cl)]2 — A Coordinatively Unsaturated Complex with Additional Agostic Yb···(H3C—Si) Interactions

“…The O1ϪO1Ј distance of 154.3(4) pm is consistent with the peroxo formulation of the O 2 2Ϫ ligand [20]. It is the first accurately deter- (165(4) pm) [17]. As expected, shorter bonds, due to increased withdrawal of electron density from the π* orbitals on the O atoms, are found in the cerium(IV) anions [bis(µ-η 2 :η 2 -O 2 )Ce 2 (CO 3 ) 6 ] 8Ϫ (146-149pm) [18,19] and [bis(µ-η 2 :η 2 -O 2 )Ce 2 (ETDA) 2 ] 4Ϫ (147.5 pm) [19].…”

“…Compound 5 is a rare example of a µ-η 2 :η 2 -peroxo lanthanide complex. Despite the high oxophilicity of the rare earth elements, there is only one previously structurally characterized compound of this type, [(µ-η 2 :η 2 -O 2 )La 2 {N(SiMe 3 ) 2 } 4 (OPPh 3 ) 2 ] [17]. In addition three Ce IV complexes with carbonate or acetate ligands, which contain a bis(µ-η 2 :η 2 -peroxo) fragment, have been reported [18,19].…”

Donor and ate‐Coordination in Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes

“…All bis(thf)-coordinated tris[bis(dimethylsilyl)amido] complexes of the rare-earth elements are isostructural (monoclinic space group P2 1 /c) with the ligands adopting a distorted trigonal-bipyramidal coordination geometry. [1,2] A number of X-ray structure analyses were performed to examine the implications of donor ligand exchange for the molecular geometry in the solid-state [2] Other donor oxide bonded discrete rare-earth metal complexes include La[N(SiMe 3 ) 2 ] 3 (O=PPh 3 ), [8] Nd(TTA) 3 -(O=PPh 3 ) 2 [TTA = tris(theonyltrifluoroacetonate)], [18] and Tb[N(SiMe 3 ) 2 ] 3 (O=CPh 2 ). [19] Nd[N(SiHMe 2 ) 2 ] 3 (nhc) 2 (4b) crystallized from a saturated hexane solution at -35°C in the triclinic space group P1.…”

“…By nature, the strong chelating donor ligand enforces a different coordination geometry, which is best described as distorted square pyramidal (apical position occupied by N3). It is interesting that the phen donor accomplishes isostructural complexes for the large methyl-1,10-phenanthroline) [62.2(2)°, dmp = dipivaloylmethanato] [23] and (2,2Ј:6Ј,2ЈЈ-terpyridine)NdCl 3 (H 2 O) 8 [62.69(7)°]. [24] The Sc-N and Nd-N bond lengths in 7d and 7b range from 2.0840(7) to 2.1366(7) Å and 2.326(1) to 2.388(1) Å, respectively, and are significantly larger than the average Ln-N distances in the precursor compounds 1d (2.069 Å) and 1b (2.344 Å).…”

Lanthanoid-Peroxo-Komplexe mit μ3-η2:η2:η2-(O22—)-Koordination. Die Kristallstrukturen von [Ln4(O2)2Cl8(Py)10] · Py mit Ln = Sm, Eu, Gd

“…Wegen der sehr geringen Toxizität von Lanthanoid-Komplexen könnten Peroxo-Verbindungen dieser Elemente künftig an Bedeutung gewinnen. Es sind bisher aber nur vereinzelt Peroxo-Komplexe der Seltenerdelemente beschrieben und kristallographisch charakterisiert worden, nämlich ein Beispiel von Lanthan [6], drei von Cer(IV) [7,8] …”