The synthesis and X-ray crystal structures of Y[N(SiHMe2)2]3(carbene) x (carbene = 1,3-dimethylimidazolin-2-ylidene, x = 1, 2) are described. The donor capability of the strongly nucleophilic carbene ligand is expressed in both the displacement of two THF ligands by one carbene ligand in precursor compound Y[N(SiHMe2)2]3(THF)2 and by the addition of a second carbene ligand to yield the preferred (3 + 2) trigonal bipyramidal coordination geometry. In particular, the structural data reveal that the carbene ligands affect the coordination mode of the bis(dimethylsilyl)amide counterligands by forcing them to form close β-Si−H(silylamide)−yttrium agostic contacts. According to Pearson's terminology such carbene ligands have to be classified as hard donor ligands.
Reaction of beta-functionalized alcohols of type HOCR(2)CH(2)do (1a, do = OMe, R = Me; 1b, do = OMe, R = Et; 1c, do = NMe(2), R = Me) with Ln[N(SiMe(3))(3)](3) yields highly volatile (sublimation < 100 degrees C/10(-)(3) Torr) and n-hexane-soluble homoleptic alkoxide complexes [Ln(OCR(2)CH(2)do)(3)] (2a-d, Ln = Y, Lu). A single-crystal X-ray diffraction study of Lu(OCMe(2)CH(2)OMe)(3) (2a) revealed a dinuclear complex with significantly polarized metal centers originating from asymmetrical ligand association (triple-bridging). Unintentional employment of "water-contaminated" alcohol 1a resulted in the formation of n-hexane-soluble 3 exhibiting a substantially increased sublimation temperature (>220 degrees C/10(-)(3) Torr). Crystallization of 3 affords single crystals 3a featuring the tetranuclear constitution Lu(4)(O)(OH)(OCMe(2)CH(2)OMe)(9). 3a represents an unprecedented lanthanide alkoxide comprising both oxo and hydroxo units in addition to alkoxide ligands. The Lu(4)O(15)-core structure of 3a adopts a "butterfly" rather than a tetrahedral geometry. Potentially tridentate alcohols HOCtBu(CH(2)OiPr)(2) (4) and HOCiPr(2)CH(2)OCH(2)OMe (5) afford alkoxide complexes "Nd(OR)(3)" (6, 7) of reduced volatility. 2a crystallizes from n-hexane at ambient temperature in space group P2(1)/n with a = 13.510(1) Å, b = 15.130(1) Å, c = 38.953(4) Å, beta = 93.11(1) degrees, V = 7950 Å(3), and Z = 8. Least-squares refinement of the model based on 11 747 reflections (I > 2.0 sigma(I)) converged to a final R = 3.5%. 3a crystallizes from n-hexane at -35 degrees C in space group Cc with a = 21.63(1) Å, b = 14.49(3) Å, c = 21.04(2) Å, beta = 109.70(3) degrees, V = 6209 Å(3), and Z = 4. Least-squares refinement of the model based on 6057 reflections (I > 3.0 sigma(I)) converged to a final R = 6.7%.
Complexes of the Lanthanides, IV[1]. — Alkyl‐and Donor‐substituted Cyclopentadienyl Complexes of Neodymium Neodymium trichloride reacts with the potassium salt K(DoCH2CH2Cp) (2c, DoOMe; 2d, DoNMe2) of the functionalized cyclopentadienyls in THF to yield the sublimable homoleptic complexes Nd(DoCH2CH2Cp)3 (3c, d). Under the same conditions, K(iBuCp) (2a) yields the adduct Nd(i1‐BuCp)3(THF) (3a′), which is obtained free of THF by thermal treatment. The silylamide route is applied to synthesize the homoleptic neopentylcyclopentadienyl derivative Nd‐(NeopCp)3 (3b). The alkyl‐substituted complexes, particularly the isobutyl derivative, show a remarkable volatility. The first solvent‐free, monomeric complex of the type „LnCp2Cl”︁, namely Nd(Me2NCH2CH2Cp)2Cl (4), is obtained from NdCl3 and two equivalents of 2d.
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