Lutetium compounds/complexes, coordination

Eanthanide triflates reacts with PhsPO in ethanol forming [En(OTf)2(Ph3PO)4] OTf (Ln = La, Nd, Er, Lu). The erbium and lutetium compounds have octahedral coordination, with monodentate triflates, but the complexes of the larger La and Nd have seven-coordination with one triflate being bidentate. 

The first structure of a [Ln(phen)2(N03)3] complex was reported in 1992 for the lanthanum compound.It closely resembled the established bipy analogue in that the three nitrate groups were bidentate and the lanthanum was 10-coordinate. The structural information was complemented by a multinuclear solution ( H-, C-, O-, and La) NMR study. The structure of the other extreme member of the series, the lutetium complex, was reported in 1996. Unlike the La complex, but like [Lu(bipy)2(N03)3], the study was not complicated by disorder. The complexes appear to form an isomorpohous and isostructural series. On moving from the lanthanum to the lutetium compound, the Ln—N distances decrease from 2.646(3)-2.701(3) A (La) to 2.462(8)-2.479(8) A (Lu), and the range of Ln—O distances decreases from 2.580(3)-2.611(3) A for the lanthanum compound to 2.364(8)-2.525(6) A for the lutetium complex. Several structures have subsequently been reported of other [Ln(phen)2(N03)3] systems. [Ln(phen)2(N03)3] (Ln = Pr, Lu, Dy, are isostructural the individual complex... 

The reactions of LnCls with only one equivalent of K2C8H8, carried out in THF, afford complexes of the type [C8H8LnCl(THF)2]2 (105,111, 112). The investigation of the structure of the cerium complex proves the dimeric nature and shows the two cerium atoms bridged asymmetrically by the two chlorine atoms,and, in each case, coordinated by one cyclooctatetraenyl ring and two THF molecules (113). The complexes loose THF upon heating to 60 C in vacuo. The lutetium compound reacts with alkyl-lithium compounds with formation of the first cyclooctatetraenyl(organ-yl)lutetium compounds (11 ) ... 

The NTA complexes of praseodymium and dysprosium serve as examples of the former problem. These two compounds which have the formulae PrNTA-3H20 and DyNTA-4H 0 contain nine-coordinate praseodymium with one water of hydration (Martin and Jacobson, 1972a) and eight-coordinate dysprosium with two water molecules of hydration (Martin and Jacobson, 1972b). It is clear that neither of these is predicted by the stoichiometry of the complexes. The second problem is illustrated by the complexes R(N03)3-mDMSO ( = 3 or 4). The complex Nd(N03)3 4DMSO (Aslanov et al., 1972b) has all the nitrate ions coordinated in a bidentate fashion which results in overall ten-coordination. The complex Lu(N03)3-3DMSO (Aslanov et al., 1973) also has all three nitrate ions coordinated and the lutetium is nine-coordinate. 

Coordination compounds composed of tetrapyrrole macrocyclic ligands encompassing a large metal ion in a sandwich-like fashion have been known since 1936 when Linstead and co-workers (67) reported the first synthesis of Sn(IV) bis(phthalocyanine). Numerous homoleptic and heteroleptic sandwich-type or double-decker metal complexes with phthalocyanines (68-70) and porphyrins (71-75) have been studied and structurally characterized. The electrochromic properties of the lanthanide pc sandwich complexes (76) have been investigated and the stable radical bis(phthalocyaninato)lutetium has been found to be the first example of an intrinsic molecular semiconductor (77). In contrast to the wealth of literature describing porphyrin and pc sandwich complexes, re-... 

The Lu—C cr-bonding distances range from 2.425(15) to 2.501(17) A. These distances are approximately 0.2 A shorter than the corresponding distance for a pentahapto cyclopentadienide lutetium bond as predicted from ionic radii. Coordination about the lutetium atom is a slightly distorted tetrahedron. The formal coordination number of four is extremely low for the lanthanides. The only other lanthanide complex with such a low coordination number is the 3-coordinate compound [Lu N(SiMes)2 3] 131). In both cases, the low coordination number is stabilized by the use of bulky hgands. 

Watson demonstrated alkane activation among /-block metals. Lutetium and ytterbium metals form complexes that are capable of inserting into C-H a bonds. The coordinatively unsaturated complexes (Cp )2M-CH3 (M = Yb, Lu) show a variety of interesting reactions (mainly of the Ziegler-Natta type). For example, the lutetium complex under solvent-free conditions exists as a dimer [Eq. (6.95) see Chapter 2, Section 2.10]. The crystal structure of the dimer indicates it to be unsymmetrical, in which a methyl group from one molecule coordinates to vacant metal orbitals of the second molecule. In cyclohexane solution, about 15% of this compound exists as a monomer and equilibration is rapid on the NMR timescale. For the dissociation of the dimer to monomers. A//= 12.6 kcal mol and A5 = 32.8eu in cyclohexane were reported. ... 

Yb atoms, bidentate bridges are proposed (Marks and Grynkevich, 1976). The lutetium complex shows a 1 1 1 1 quartet in the H NMR spectrum at 6 = 1.07 ppm for BH4 with 7(BH) = 84 Hz (Schumann et al., 1982). The compound loses the coordinated THF reversibly upon heating in vacuo or toluene. 

The NMR spectra of compounds of this class have been studied in general on the diamagnetic lutetium complexes (Table 1.12). The H NMR spectra indicate a monomeric form of complexes, the existence of tj -Cp-Lu bond, the existence of terminal a-bonded alkyl groups and the presence of coordinated THF molecules. The similar results have been obtained with C NMR spectra [150]. 

The lutetium complex free of coordinative solvents is formed in the interaction of dimethylphosphinomethyllithium with CpjLuClCTHF) [242]. The NMR spectroscopy data, particularly the resolution of Cp groups signals in C NMR spectrum, in the author s opinion indicates the existence of intramolecular coordination P — Lu. Thus, the stabilization of the compound is achieved due to the formation of a three-membered metallocycle ... 

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