Lanthanide complexes, homoleptic

Homoleptic lanthanide(III) tris(amidinates) and guanidinates are among the longest known lanthanide complexes containing these chelating ligands. In this area the carbodiimide insertion route is usually not applicable, as simple, well-defined lanthanide tris(alkyls) and tris(dialkylamides) are not readily available. A notable exception is the formation of homoleptic lanthanide guanidinates from... 

Scheme 8.1 Three key methods of the synthesis of lanthanide(lll) bis(phthalocyanine) complexes. Homoleptic complexes symmetrical (A, B) and unsymmetrical (C1 and C2, D1). Thereby, the thermal fusion group A can be subdivided into (A1) solvent free fusion (A2) refluxing in the mixture of protic solvents in the presence of organic base - DBU and (A3) MW assisted fusion.

Hydrocarbonyl compounds, lanthanide complexes, 4, 4 ( -Hydrocarbyl)bis(zirconocene), preparation, 4, 906 Hydrocarbyl-bridged cyclopentadienyl-amido complexes, with Zr(IV), 4, 864 Hydrocarbyl complexes bis-Cp Ti hydrocarbyls reactions, 4, 551 structure and properties, 4, 551 synthesis, 4, 542 cobalt with rf-ligands, 7, 51 cobalt with rf-ligands, 7, 56 cobalt with ]4-ligands, 7, 59 cobalt with rf-ligands, 7, 71 heteroleptic types, 4, 192 homoleptic types, 4, 192 into magnetic metal nanoparticles via ligand stabilization, 12, 87 via polymer stabilization, 12, 87 into noble metal nanoparticles... 

The introduction of the btsa ligand into lanthanide chemistry by Bradley led to the isolation of the homoleptic compounds Ln(btsa)3 [7], interpreted as the first 3-coordinate lanthanide complexes. This result was indeed spectacular and exploration of the chemical and physical properties of this simple system is continuing [104-106]. 

The homoleptic lanthanide(III) benzamidinates 20-23 can be regarded as analogues of the well known tris(cyclopentadienyl)lanthanide complexes (C5H5)3Ln [7, 8]. One of the most characteristic reactions of the homoleptic cyclopentadienyls is the formation of 1 1 adducts with Lewis bases such as ethers, nitriles, esters etc. [7, 8], Recently it was discovered that the homoleptic lanthanide benzamidinates [PhC(NSiMe3)2]3Ln (20) form similar adducts with THF and nitrile ligands such as acetonitrile or benzonitrile [59]. The molecular and crystal structures of two benzonitrile adducts (26g, h) have been determined by X-ray diffraction. Figure 8 depicts the molecular structure of the europium... 

Homoleptic lanthanide complexes containing the [PhS(NSiMe3)2] ligand were prepared in a straightforward manner by treatment of anhydrous lanthanide trichlorides with three equivalents of Li[PhS(NSiMe3)2]0.5 Et20 (10) [72] ... 

An interesting class of homoleptic lanthanide complexes has become available through the use of heteroallylic diphosphinomethanide ligands. The first member of the series was the lanthanum derivative, [CH(PPh2)2]3La (59c), which was characterized by X-ray crystallography (Fig. 19) [74]. The preparation of 59c involved treatment of anhydrous lanthanum trichloride with the potassium salt of the ligand ... 

Although pyridine and other amine-type ligands form adducts with lanthanide diketonates, few other lanthanide complexes have been made. However, the first homoleptic lanthanide ammine complexes, [Yb(NH3)g] [Cu(S4)2] NH3, [Yb(NH3)s] [Ag(S4)2]-2NH3,and[La(NH3)9] [ 0(84)2],have been synthesised by reactions in aqueous ammonia. ... 

The synthesis, structure, and physical and chemical properties of organo-lanthanide complexes containing only polyhaptocyclopentadienyl and cyclooctatetraenyl metal-carbon bonds are fully covered in other reviews (5-7). This section will focus on lanthanide-carbon single bonded species only. Ln—C single bonds are found almost exclusively in only two types of complexes homoleptic complexes, and heteroleptic... 

With the exception of the metallation reaction in Eq. (4), little chemistry has been reported for homoleptic lanthanide complexes. With four to six reactive alkyl sites per metal center, these compounds are potentially much more reactive than the bis(cyclopentadienyl)alkyl compounds described in Section IV,B. This is an area of future growth in the organolanthanide held. 

Harder, S. (2005) Syntheses and structures of homoleptic lanthanide complexes with chelating o-dimethylaminobenzyl ligands key precursors in lanthanide chemistry. Organometallics, 24, 373. 

Using this synthetic route, eight novel homoleptic tris(guanidinato) lanthanide complexes [R2NC(NPr )2]3Ln [Ln = Y, Gd, Dy R = Me, Et, PE] have recently... 

Recently, it was shown that the polymerization of s-caprolactone can be also performed using a homoleptic amidinate uranium (HI) complex (17 and 18) however, the activity of the complex was found to be more sluggish as compared to that of other actinide complexes or similar homoleptic lanthanide complexes [108]. 

Reactions of UCI4 with [Li RC(NCy)2 (THF)]2 (R = Me, Bu ) in THF gave the tris(amidinate) compounds [RC(NCy)2]3UCl that could be reduced with lithium powder in THF to the dark-green homoleptic uranium(lll) complexes [RC(NCy)2]3U. Comparison of the crystal structure of [MeC(NCy)2]3U with those of the lanthanide analog showed that the average U-N distance is shorter than expected from a purely ionic bonding model. ... 

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-... 

Scheme 12.8 (a) Introduction of bulky ligands (L ) by direct grafting of heteroleptic lanthanide silylamide complexes on mesoporous MCM-41 (22-25) (cf route A in Scheme 12.3) (b) grafting of (homoleptic) lanthanide silylamide complexes on a mesoporous material (cf route A in Scheme 12.3) followed by a subsequent ligand exchange (cf route C in Scheme 12.3) via protonolysis of the Ln-N bond with HL (A-L). 

Lanthanide-based catalysts, despite finding a lot of application in homogeneous catalysis, can be rather problematic due to the lability of some ligand types and the versatility of their coordination chemistry in the -1-3 oxidation state this makes the controlled synthesis of single-site Ln complexes a quite ambitious goal [92]. McLain and coworkers first demonstrated the high potential of a homoleptic yttrium complex Y(OCH2CH2NMe2)3 as ROP catalyst for the preparation of PLA from rac-lactide and that it promotes a rapid and controlled polymerization... 

As discussed above, lanthanides and group 3 homoleptic complexes are attractive initiators because of their moderate Lewis acidities, good activities of polymerization, and low toxicity [94, 111, 112, 115-118]. A list of lanthanide initiators and their polymerization activity is listed in Table 5. 

The addition of a base, typically ammonia, to mixtures of transition metal halides and alcohols allows the synthesis of homoleptic alkoxides and phenoxides for a wide range of metals. Anhydrous ammonia was first used in the preparation of titanium alkoxides where the reaction is forced to completion by the precipitation of ammonium chloride.41 Although useful for the synthesis of simple alkoxides and phenoxides of Si, Ge, Ti, Zr, Hf, V, Nb, Ta and Fe, as well as a number of lanthanides,42-47 the method fails to produce pure /-butoxides of a number of metals.58 Presumably, secondary reactions between HC1 and Bu OH take place. However, mixing MC14(M = Ti, Zr) with the Bu OH in the presence of pyridine followed by addition of ammonia proves successful, giving excellent yields of the M(OBul)4 complexes.59... 

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