172918-17-1Relevant articles and documents
Alkali Metal Induced Structural Changes in Complexes Containing Anionic Lanthanum Aryloxide Moieties. X-ray Crystal Structures of (THF)La(OAr)2(μ-OAr)2Li(THF), (THF)La(OAr)2(μ-OAr)2Na(THF)2, and CsLa(OAr)4 (Ar = 2,6-i-Pr2C6H3)
Clark, David L.,Hollis, Rebecca V.,Scott, Brian L.,Watkin, John G.
, p. 667 - 674 (2008/10/09)
Reaction of La2(OAr)6 (1, Ar = 2,6-i-Pr2C6H3) with 2 equiv of LiOAr in THF produces the lanthanum tetrakis(aryloxide) salt (THF)La(OAr)2(μ-OAr)2Li(THF) (2). A similar reaction employing NaOAr leads to isolation of the analogous sodium salt (THF)La(OAr)2(μ-OAr)2Na(THF)2 (3), 1 reacts with 2 equiv of cesium aryloxide in THF to yield the base-free cesium salt CsLa(OAr)4 (4). Compounds 2, 3, and 4 have been characterized by 1H NMR and IR spectroscopy, microanalysis, and single-crystal X-ray diffraction studies. The overall molecular geometry of 2 comprises a five-coordinate La metal center coordinated by four aryloxide ligands and one THF ligand in a somewhat distorted trigonal bipyramidal geometry and a three-coordinate Li cation which is coordinated to the oxygen atoms of two aryloxide ligands as well as a single THF ligand. La - O bond lengths average 2.208(3) and 2.384(3) A? for terminal and bridging aryloxide ligands, respectively, while the average Li-O(aryloxide) bond distance is 1.866(10) A?. The molecular geometry of 3 is similar to that observed in 2, with a five-coordinate La metal center displaying a distorted trigonal bipyramidal geometry in which a THF ligand and an aryloxide ligand occupy axial positions. Two of the aryloxide ligands on the La metal center bridge to a sodium cation, which completes its coordination sphere by coordination of two additional molecules of THF. La - O bond lengths average 2.227(6) and 2.333(5) A? for terminal and bridging aryloxide ligands, respectively, while the average Na - OAr bond distance is 2.350(6) A?. The ipso carbon atom of one of the bridging aryloxide ligands is directed toward the fifth coordination site of the sodium cation at a distance of 3.085(9) A?. The solid state structure of CsLa(OAr)4 (4) features alternating tetrahedral [La(OAr)4]- anions (La-O = 2.241(6) A? (ave.)) and Cs+ cations held in an extended structure by means of cesium - μ-arene interactions, resulting in the formation of a quasi one-dimensional infinite chain structure. The cesium environment in 4 consists exclusively of multihapto Cs - C interactions (Cs - C range 3.696(7)-3.847(7) A?), with no Cs - O contacts of less than 4.649 A?. Crystal data for 2 (at -100 °C): orthorhombic space group Pbca, a = 20.091(3) A?, b = 19.983(2) A?, c = 27.288(2) A?, V = 10956 A?3, Z = 8, Dcalc = 1.202 g cm-3. Crystal data for 3 (at -100 °C): orthorhombic space group Pbca, a = 26.035(3) A?, b = 20.771(4) A?, c = 26.441(3) A?, V = 14299 A?3, Z = 8, Dcalc = 1.174 g cm-3. Crystal data for 4 (at -100 °C): monoclinic space group C2/c, a = 21.261(2) A?, b = 22.616(3) A?, c = 20.740(2) A?, β= 108.126(7)°, V = 9478 A?3, Z = 8, Dcalc = 1.465 g cm-3.
