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Journal ArticleDOI

Phosphine complexes of the early metals and the lanthanoids

01 Jan 1991-Pure and Applied Chemistry (International Union of Pure and Applied Chemistry)-Vol. 63, Iss: 6, pp 845-850

AbstractThe coordination chemistry of the mixed-donor tridentate ligand -N(SiMezCH2PR2)2 with the early transition metals of groups 3 and 4 and the lanthanide elements will be presented. This ancillary ligand has allowed for the formation of phosphine complexes of these hard elements which has in turn induced new reactivity patterns for hydrocarbyl ligands. The stability and reactivity of metal complexes are a function of both the position of the metal in the periodic table and the nature of the ligands. While the former provides for diverse chemical reactivity, it is

Topics: Non-innocent ligand (60%), Coordination complex (57%), Ligand (56%), Reactivity (chemistry) (55%), Lanthanide (54%) more

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Abstract: This contribution describes the synthesis, structures, bonding, and reactivity of neutral (Ox)2MR2 and cationic (Ox)2MR+ zirconium and hafnium alkyl complexes which contain substituted 8-quinolinolato ligands (Ox- = 2-Me-8-quinolinolato, MeOx-, 2; 2-Me-5,7-Br2-8-quinolinolato, MeBr2Ox-, 3). Alkane elimination and halide displacement reactions provide routes to (MeOx)2ZrR2 (9a, R = CH2Ph; 9b, R = CH2CMe3; 9c, R = CH2SiMe3), (MeOx)2Hf(CH2Ph)2 (10a), (MeBr2Ox)2ZrR2 (11a, R = CH2Ph; 11b, R = CH2CMe3), (MeBr2Ox)2Hf(CH2Ph)2 (14a), (MeOx)2ZrCl2 (15), (MeBr2Ox)2ZrCl2 (16), and (MeBr2Ox)2Zr(NMe2)2 (17). The reaction of 16, 17, or (MeBr2Ox)4Zr with AlMe3 yields (MeBr2Ox)AlMe2 (18). An X-ray crystallographic analysis shows that in the solid state 9a adopts a distorted octahedral structure with a trans-O, cis-N, cis-R ligand arrangement and that one of the benzyl ligands is bonded in an η2-fashion. Solution NMR data are consistent with this structure and establish that exchange of the distorted and normal benzyl liga...

159 citations

Journal ArticleDOI
Abstract: Ligand design in early transition metal chemistry has focussed recently on amide chemistry. The availability of two substituent positions at the amido N-donor atom allows its integration into ligand systems of both podand and macrocyclic topology. Amido functions may be combined with other donor functionalities which possess a different formal charge and chemical hardness and, more generally, a different thermodynamic and kinetic stability of their interaction with the metal centre. Early transition metal complexes containing polydentate amido-donor ligands not only display unprecedented patterns of reactivity but are the focus of recent developments in olefin polymerization catalysis.

156 citations

Journal ArticleDOI
Abstract: Organometallic derivatives of scandium and yttrium supported by a bulky salicylaldiminato ligand were prepared from the tris(alkyl) precursors [M(CH2SiMe2R)3(THF)2] (M = Sc, 1-ScR; M = Y, 1-YR; R = CH3, Ph) via alkane elimination. The new precursors 1-MPh are convenient alternatives to the 1-MMe derivatives, due to their higher thermal stability and crystallinity; 1-ScPh has been characterized crystallographically. Reaction of these compounds with 1 equiv of protio ligand gives isolable mono(ligand) bis(alkyl) derivatives only for 1-Y; for other derivatives 1-Sc, mixtures were obtained. The products of the former reaction retain either two (2-YPh) or one (3-YPh) THF ligands; both of these compounds have been characterized crystallographically. In solution, both exhibit fluxional exchange between two geometric isomers which were characterized by variable-temperature NMR spectroscopy. Heating solutions of either compound leads to facile ligand redistribution. Reactions of tris(alkyls) 1 with 2 equiv of prot...

126 citations

Journal ArticleDOI
Abstract: The preparation of new scandium phosphine complexes that contain two hydrocarbyl groups is reported Thus, reaction of the amido diphosphine ligand precursor LiN(SiMe2CH2PPri2)2 with ScCl3(THF)3 in toluene at 100 °C leads to the formation of ScCl2(THF)[N(SiMe2CH2PPri2)2] for which the THF molecule can be removed by pumping in the solid state The X-ray crystal structure of this molecule shows it to be monomeric with a distorted octahedral geometry having trans-disposed chloride ligands and the tridentate ligand meridionally bound The solution NMR spectra are also consistent with this geometry Addition of the alkyllithium reagents RLi (where R = Me, Et, and CH2SiMe3) leads to the formation of bis(hydrocarbyl) derivatives of the formula ScR2[N(SiMe2CH2PPri2)2] These are the first dialkyl-substituted scandium complexes that have been characterized The solid-state X-ray structures of ScEt2[N(SiMe2CH2PPri2)2] and Sc(CH2SiMe3)2[N(SiMe2CH2PPri2)2] show that these molecules are mononuclear in the solid state

80 citations

Journal ArticleDOI

66 citations