Complexes of lanthanides

Di-rerr-butylsodium pyrrolate serves as a source of the complexes of lanthanides [93CB2657 95JOM(495)C12]. Thus, with cyclooctadienyl chlorides of samarium, thulium, and lutetium, it affords species 89 [96JOM(507)287]. The N-coordinated samarium(II) calix-pyrrole complex is known [99AG(E)1432]. 

Complexes of lanthanide ions with N-donor ligands. J. H. Forsberg, Coord. Chem. Rev., 1973,10, 195-226 (129). 

Fig. 1.2 Standard enthalpy changes of (a) the complexing of lanthanide ions in aqueous solution by EDTA" ( left-hand axis) (b) the standard enthalpy change of reaction 2, the dichloride being a di-f...

In 2003, Livinghouse et al. also reported that chelating bis(thiophosphonic amidates) complexes of lanthanide metals, such as yttrium or neodymium, were able to catalyse intramolecular alkene hydroaminations. These complexes were prepared by attachment of the appropriate ligands to the metals by direct metalation with Ln[N(TMS)2]3- When applied to the cyclisation of 2-amino-5-hexene, these catalysts led to the formation of the corresponding pyrrolidine as a mixture of two diastereomers in almost quantitative yields and diastereos-electivities of up to 88% de (Scheme 10.81). 

Metal complexes of lanthanides beyond lanthanocenes were used to catalyze the reductive coupling reaction of dienes. La[N(TMS)2h was found to effect the cyclization of 1,5-hexadiene in the presence of PhSiH3 (Eq. 13) [50]. Cyclized products 88 and 89 were isolated in a combined yield of 95% (88 89 = 4 1). It was suggested that the silacycloheptane 89 resulted from competitive alkene hydrosilylation followed by intramolecular hydrosilylation. 

Marks et al. reported the co-polymerization of ethylene and 1-hexene by using ansa-type complexes of lanthanide metals [127]. Recently, bulky alkyl substituted ansa-type metallocene complexes of yttrium have been reported to exhibit high activity for the polymerization of 1-hexane. [114, 119, 128]... 

Some non-metallocene complexes of lanthanide metals such as Sml2... 

We start our description of the electronic structure of complexes of lanthanides by the analysis of the free ion energy structure. The relevant Hamiltonian is written as... 

Some examples of borohydride complexes of lanthanide and actinide metals are given in Table 2. 

The controlled synthesis of carbons adjacent nido- and arachno-carborane anions can be achieved by the reduction of C (cage)-C (cage)-linked o-carboranes with group 1 metals.234-237 Typical examples are illustrated in Scheme 22. These have been found to undergo metallation reactions similar to their carbons apart analogs, forming full- and half-sandwich complexes of lanthanide metals.238... 

As mentioned in the introduction, early transition metal complexes are also able to catalyze hydroboration reactions. Reported examples include mainly metallocene complexes of lanthanide, titanium and niobium metals [8, 15, 29]. Unlike the Wilkinson catalysts, these early transition metal catalysts have been reported to give exclusively anti-Markonikov products. The unique feature in giving exclusively anti-Markonikov products has been attributed to the different reaction mechanism associated with these catalysts. The hydroboration reactions catalyzed by these early transition metal complexes are believed to proceed with a o-bond metathesis mechanism (Figure 2). In contrast to the associative and dissociative mechanisms discussed for the Wilkinson catalysts in which HBR2 is oxidatively added to the metal center, the reaction mechanism associated with the early transition metal complexes involves a a-bond metathesis step between the coordinated olefin ligand and the incoming borane (Figure 2). The preference for a o-bond metathesis instead of an oxidative addition can be traced to the difficulty of further oxidation at the metal center because early transition metals have fewer d electrons. 

Moeller and Vicentini (48) have reported the complexes of DMA with lanthanide perchlorates in which the number of DMA molecules per metal ion decreases from eight for La(III)—Nd(III) to six for Tm(III)—Lu(III).apparently due to the decrease in the cationic size. The complexes of the intermediate metal ions have seven molecules of DMA in their composition. Complexes of lanthanide chlorides with DMA (49, 50) exhibit a decrease in L M from 4 1 to 3 1 through 3.5 1. These complexes probably have bridging DMA molecules. The corresponding complexes with lanthanide iodides (51), isothiocyanates (52), hexafluorophosphates (57), nitrates (54, 55), and perrhenates (49, 56) also show decreasing L M with decreasing size of the lanthanide ion. However, complexes of DMA with lanthanide bromides (55) do not show such a trend. Krishnamurthy and Soundararajan (41) have reported the complexes of DPF with lanthanide perchlorates of the composition [Ln(DPF)6]... 

Complexes of the lanthanides with a few cyclic amides are known. Miller and Madan have reported the complexes of 7-butyrolactam with lanthanide nitrates (60) and perchlorates (61). Complexes of lanthanide perchlorates and lighter lanthanide nitrates with BuL have a L M of 8 1. However, complexes of heavier lanthanide nitrates have a L M of only 3 1. By changing the solvent used for the crystallization of the abovementioned complexes, complexes of the formula [La(BuL)4(N03)3] and [Gd(BuL)3(N03)3] could be prepared (60). Complexes of NMBuL (61, 62) and CLM (63-66) have also been reported. 

A number of complexes of urea and substituted ureas with various lanthanide salts have been isolated. The lanthanide acetates give both anhydrous and hydrated complexes with urea (67, 68). The hydrated complexes could be dehydrated by drying the complexes over CaCl2 or P4Oi0 (68). It is interesting to note that in the complexes of substituted ureas like EU (70) and CPU (71), the L M is independent of the anion. The anions in these complexes with a L M of 8 1 are apparently nonco-ordinated. Seminara et al. (72) have reported complexes of lanthanide chlorides with DMU and DEU which contain five and three molecules of the ligand respectively per... 

Probably, the first series of lanthanide complexes with neutral oxygen donor ligands is that of AP with the lanthanide nitrates. In 1913, Kolb (79) reported tris-AP complexes with lighter lanthanide nitrates and tetrakis-AP complexes with heavier lanthanide nitrates. Subsequently, complexes of lanthanide nitrates with AP which have a L M of 6 1 and 3 1 have also been prepared (80-82). Bhandary et al. (83) have recently shown through an X-ray crystal and molecular structure study of Nd(AP)3(N03)3 that all the nitrates are bidentate and hence the coordination number for Nd(III) is nine in this complex. Complexes of AP with lanthanide perchlorates (81, 84), iodides (81, 85), and isothiocyanates (66, 86, 87) are known. While the perchlorates and iodides in the respective complexes remain ionic, two of the isothiocyanates are coordinated in the corresponding complexes of AP with lanthanide isothiocyanates. 

Castellani Bisi (98) has synthesized complexes of lanthanide perchlorates with DMP which have a L M of 8 1 for the lighter lanthanide and 7 1 for the heavier lanthanide complexes. These complexes were prepared by reacting the respective metal salts with an excess of the ligand. When the complexes were prepared under conditions of lower concentrations of the ligand, complexes of DMP with a L M of 6 1 were obtained. The perchlorate groups in all three groups of complexes are ionic. 

Complexes of lanthanide chlorides 156,173), bromides (256), and iodides 174) with 2,6-DMePyO have also been prepared and characterized. The presence of bridging 2,6- DMePyO molecules has been suggested in the complexes of lanthanide iodides. Vicentini and De Oliveira (2 73) have reported tetrakis-2,6-DMePyO complexes with lanthanide nitrates. However, by changing the method of synthesis, tris-2,6-DMePyO complexes with the lanthanide nitrates could be prepared in this laboratory (252). All the nitrate groups in the tris-2,6-DMePyO complexes are bidentate. In the 2,4,6-TMePyO complexes (252) also the nitrate groups are coordinated to the lanthanide ion in a bidentate fashion. 

Vicentini and Dunstan (227) have obtained tetrakis-DDPA complexes with lanthanide perchlorates in which the perchlorate groups are shown to be coordinated to the metal ion. DDPA also yields complexes with lanthanide isothiocyanates (228) and nitrates (229). All the anions in these complexes are coordinated. DPPM behaves more or less like DDPA which is reflected in the stoichiometry of the complexes of DPPM with lanthanide perchlorates (230), nitrates, and isothiocyanates (231). Hexakis-DMMP complexes of lanthanide perchlorates were recently reported by Mikulski et al. (210). One of the perchlorate groups is coordinated to the metal ion in the lighter lanthanide complexes, and in the heavier ones all the perchlorate groups are ionic. 

Since 1972, complexes of lanthanides with cyclic sulfoxides have received considerable attention. Zinner and Vicentini (261) have reported the complexes of lanthanide perchlorates with TMSO. The L M in these complexes decreases along the lanthanide series. But in the case of complexes of lanthanide chlorides with TMSO, the L M increases from 2 1 for the lighter lanthanides to 3 1 for the heavier lanthanides (262). It has been suggested that these complexes, especially the bis-TMSO complexes, contain bridging chloride ions. Tetrakis-TMSO complexes with lanthanide isothiocyanates have also been reported (263). 

The L M in the complexes of lanthanide nitrates with TMSO decreases along the lanthanide series (264, 265). All these complexes contain both bidentate and mono-dentate nitrate groups (264), the monodentate nitrates giving way to bidentate nitrates as the cationic radius decreases. 

Complexes of the lanthanides with only one ligand of this type have been reported so far. Paetzold and Bochmann (276) have reported the complexes of lanthanide perchlorates with DMSeO which have the composition Ln(DMSe0)8(C104)3. A distorted square antiprismatic structure with a point group symmetry )4 has been proposed for these complexes. 

In the case of complexes of lanthanide nitrates with CP (239), the infrared spectra exhibit two uCz=Q vibrations apart from a single pP=0- The J>p=o and one of the c=o vibrations occur at frequencies lower than the corresponding ligand frequencies But the second r>c=0 1S not much shifted from the free ligand value. These observations have been interpreted in terms of Structure VIII containing both coordinated... 

In all other complexes of lanthanide nitrates, the mode of coordination has been identified, with some ambiguity, from IR data alone. In most of the cases, either the criterion suggested by Addison et al. (287), Curtis and Curtis (288) or Lever et al. (289) has been used for this purpose. Ionic nitrate groups have been identified in the complexes of BuL (60), HMPA (223), and O-PhenNO (178) with lanthanide nitrates. Both unidentate and bidentate nitrate groups are present in the complexes of lanthanide nitrates with MP (232), OMPA (234), CMP (240), TMSO (264), DMF (42), and BuL (60). Complexes of PyO, 2-MePyO, 2,6-DMePyO, and 2,4,6-TMePyO which have the general formula Ln(L)3(N03)3 -x H20 contain only bidentate nitrate groups (152,170). 

In the complexes of lanthanide perrhenates with TMU (78), DMA (56), and DMF (46), it has been observed that the i>3(Re04) vibration splits into three bands in the region 900 cm-1. This indicates the presence of coordinated perrhenate group (either C3v or C2v symmetry). The ionic perrhenate group exhibits only one band in this region. 

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