Lanthanide-tetrapyrrole complexes: synthesis, redox chemistry, photophysical properties, and photonic applications

Tetrapyrrole derivatives such as porphyrins, phthalocyanines, naphthalocyanines, and porpholactones, are highly stable macrocyclic compounds that play important roles in many phenomena linked to the development of life. Their complexes with lanthanides are known for more than 60 years and present breath-taking properties such as a range of easily accessible redox states leading to photo- and electro-chromism, paramagnetism, large non-linear optical parameters, and remarkable light emission in the visible and near-infrared (NIR) ranges. They are at the centre of many applications with an increasing focus on their ability to generate singlet oxygen for photodynamic therapy coupled with bioimaging and biosensing properties. This review first describes the synthetic paths leading to lanthanide-tetrapyrrole complexes together with their structures. The initial synthetic protocols were plagued by low yields and long reaction times; they have now been replaced with much more efficient and faster routes, thanks to the stunning advances in synthetic organic chemistry, so that quite complex multinuclear edifices are presently routinely obtained. Aspects such as redox properties, sensitization of NIR-emitting lanthanide ions, and non-linear optical properties are then presented. The spectacular improvements in the quantum yield and brightness of Yb^III-containing tetrapyrrole complexes achieved in the past five years are representative of the vitality of the field and open welcome opportunities for the bio-applications described in the last section. Perspectives for the field are vast and exciting as new derivatizations of the macrocycles may lead to sensitization of other Ln^III NIR-emitting ions with luminescence in the NIR-II and NIR-III biological windows, while conjugation with peptides and aptamers opens the way for lanthanide-tetrapyrrole theranostics.

Single hydroxo-bridged group 13 metalloporphyrin dimers: Solution studies and solid-state structures

The syntheses of indium, gallium and aluminum porphyrin dimers with a single hydroxo-bridge, [Formula: see text][M(Porph)]2(OH)[Formula: see text], are described. Emphasis is given to indium and gallium derivatives. The X-ray structures for [Formula: see text] [Ga(OEP)]2(OH)[Formula: see text] ClO4 and [Formula: see text] [In(OEP)]2(OH)[Formula: see text] ClO4 (two forms) are presented. The dimeric molecules can be synthesized by the acid-treatment of the corresponding hydroxo-ligated monomeric complexes [M(OEP)(OH)] and [M(TPP)(OH)]. The nature of the starting material (the hydroxo-ligated monomer) was first suggested by IR spectroscopy and further proved by proton-deuterium exchange followed by 1H NMR spectroscopy. The structure of a monomeric indium hydroxide complex, [In(OEP)(OH)], is also presented. The synthesis of the dimer for all metals can be monitored by UV-vis spectroscopy, which clearly demonstrates that a blue-shift of the Soret band accompanies formation of the dimer from the monomer. A strong [Formula: see text]–[Formula: see text]interaction between the two porphyrin rings of these [Formula: see text]-hydroxo-bridged dimers is confirmed both by solution state studies (1H NMR and UV-vis spectroscopy) and the X-ray structures of [Formula: see text] [M(OEP)]2(OH)[Formula: see text] ClO4 (M = In, Ga). In addition, exposure of methylene chloride solutions of these bridged complexes to white light afforded the corresponding chloro derivatives, [M(Porph)Cl]. The stereochemistry of a range of [Formula: see text]-hydroxo dimers is discussed and DFT simulations at the HSEH1PBE/SDD level of theory provide suitable structural models and further electronic structure insights on selected [Ga(Porph)(OH)] and [Formula: see text] [Ga(Porph)]2(OH)[Formula: see text][Formula: see text] derivatives.

Density Functional Theory as a Predictive Tool for Cerium Redox Properties in Nonaqueous Solvents

Two methods to correlate and predict experimental redox potentials for cerium complexes were evaluated. Seventeen previously reported cerium complexes were computed using DFT methods in both the Ce^III and Ce^IV oxidation states with a dichloromethane solvent continuum. In the first computational approach, the ΔG^o(Ce^IV/Ce^III) was determined for each of the compounds and these values were correlated with the experimental E_1/2 values measured in dichloromethane, referenced to the ferrocene/ferrocenium couple. The second method involved correlating the energies of the Ce^IV LUMOs (lowest unoccupied molecular orbitals) with the experimental redox potentials, E_1/2. The predictive capabilities of these two correlative methods were tested using a new cerium hydroxylamine complex, Ce(ODiNOx)₂ (ODiNOx = bis(2-tert-butylhydroxylaminatobenzyl) ether). All 18 complexes studied in this paper were combined with the 15 complexes determined in acetonitrile from a previously published correlation by our group. These sets of data allowed us to develop two methods for predicting the redox potential of cerium complexes regardless of the solvent for the experimental measurement.

Control of clustering behavior in anionic cerium(iii) corrole complexes: from oligomers to monomers

The first synthesis of anion capped cerium corrole complexes is reported. Unusual clustering of the lanthanide corrole units has been found and the degree of aggregation can be controlled by the choice of the capping ligand. A polymeric structure 1a, with the general formula [Cor-Ce(THF)-Cp-Na]n (Cor = 5,15-bis(2,4,6-trimethylphenyl)-10-(4 methoxyphenyl)-corrole, THF = tetrahydrofuran), is formed using sodium cyclopentadienide (NaCp) and a dimeric structure 2a, with the general formula [Cor-Ce-Tp]2, is formed when potassium tris(pyrazolyl)borate (KTp) is used. Encapsulation of the counter-cation leads to the isolation of the monomeric structures 1b and 2b, with the general formulas [AM(2.2.2-cryptand)][Cor-Cp-X] (AM = Na or K, X = Cp or Tp). The structural and spectroscopic properties of the complexes have been investigated.

Infra-red spectroscopic characteristics of naphthalocyanine in bis(naphthalocyaninato) rare earth complexes peripherally substituted with thiophenyl derivatives

The infra-red (IR) spectroscopic data for a series of eleven rare earth double-deckers MIII[Nc(SPh)8]2 (M=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er) have been collected and systematically investigated. For MIII[Nc(SPh)8]2, typical IR marker bands for the naphthalocyanine anion radical [Nc(SPh)8].- were observed at 1317-1325 cm(-1) as the most intense absorption bands, which can be attributed to the pyrrole stretching. As for Ce[Nc(SPh)8]2, the typical IR marker band was also observed at 1317 cm(-1), which shows that the cerium complex exists as the form of CeIII[Nc(SPh)8]2-[Nc(SPh)8].-. In addition, both the Q-bands of electronic absorption spectra and the typical IR absorption bands of naphthalocyanine radical anion [Nc(SPh)8].- move to the high energy as the decrease of rare earth metal ionic radius. These facts suggest that the π-π electron interaction in these double-deckers becomes stronger along with the lanthanide contraction.

Endohedral metal or a fullerene cage based oxidation? Redox duality of nitride clusterfullerenes Ce(x)M(3-x)N@C(78-88) (x = 1, 2; M = Sc and Y) dictated by the encaged metals and the carbon cage size

Redox behavior of endohedral metallofullerenes, in particular their oxidation process, can be classified as a fullerene-based or endohedral species-based process according to the mechanism of the electron transfer. Here we report on the phenomenon of the strain-driven electrochemical behavior achieved by encapsulating the cerium-containing clusters into a series of carbon cages ranging from C78 to C88. The Ce-based mixed metal nitride clusterfullerenes CexM3-xN@C2n (x = 1, 2; M = Sc or Y; 2n = 78-88) were synthesized and characterized. The magnitude of the inherent strain caused by the limited inner space of the carbon cage for the relatively large nitride clusters can be varied by choosing different scaffold metals (Sc, Lu, or Y) to tailor the size of the encaged CexM3-xN cluster and by matching the nitride cluster with different fullerene cages in the size range from C78 to C88. The redox properties of CexM3-xN@C2n were investigated by cyclic and square wave voltammetry. The mechanism of the electrochemical oxidation of Ce-based mixed metal nitride clusterfullerenes, in particular whether the fullerene-based oxidation or the Ce(III) → Ce(IV) process is observed, is found to be dependent on the scaffold metal and the size of the fullerene cage. The endohedral oxidation of Ce(III) to Ce(IV) was observed for a number of compounds as revealed by the negative shift of their oxidation potentials with respect to the values measured for the non-Ce analogues. Experimental studies are supported by DFT calculations. We conclude that the prerequisites for the Ce-based endohedral oxidation process are suitable inherent cluster-cage strain and sufficiently high oxidation potential of the fullerene cage.

Double-decker lutetium(III) diphthalocyanine with eight crown ether substituents

Neutral double-decker radical lutetium(III) diphthalocyanine with eight crown ether substituents bound through oxymethyl bridges has been synthesized from 1-[(benzo-15-crown-5)-4′-yl]oxymethyl-3,4-dicyanobenzene and lutetium(III) acetate. The ESR spectrum confirmed the radical nature of the complex.

Mixed-Valence Porphyrin π-Cation Radical Derivatives: Electrochemical Investigations

The electrochemistry of [Cu(OEP)] and [Ni(OEP)] are compared with the mixed-valence π-cations [Cu(OEP•/2)]2+and[Ni(OEP•/2)]2+. These electrochemical studies, carried out with cyclic voltametry and hydrodynamic voltametry, show that the mixed valence π-cations have distinct electrochemical properties, although the differences between the [M(OEP)](+/0) and [M(OEP•/2)]2+/0 processes are subtle.

Gadolinium Acetylacetonate Tetraphenyl Monoporphyrinate Complex and Some of Its Derivatives: EXAFS Study and Molecular Dynamics Simulation

Many attempts to obtain single crystals appropriate for X-ray diffraction analysis of the Ln(tpp)(acac) derivatives (where Ln = Gd or Sm, tpp = tetraphenylporphyrin and acac = acetylacetonate) have failed so far. A suitable way to get structural parameters for these monoporphyrinates is to use extended X-ray absorption fine structure (EXAFS) spectroscopy. We recorded spectra of the monoporphyrins, Ln(tpp)(acac) and Gd(tpyp)(acac) (where tpyp = tetrapyridylporphyrin), and the bisporphyrin GdH(tpyp)2 in the solid state. We particularly focused our structural analysis on Gd(tpp)(acac), applying both molecular modeling and EXAFS, which allowed us to get accurate results about the local environment of the central atom. The Gd3+ ion of the complex at room temperature was found to be bonded to four monoporphyrin nitrogen atoms at an average distance R(Gd-N(av)) = 2.48 A and to three or four oxygen atoms at R(Gd-O(ac,w)) = 2.38 A from an acetylacetonato anion and a water molecule. The presence of the second water molecule in the coordination sphere was barely discernible by EXAFS analysis. Molecular modeling has provided further information about the coordination core geometry of the Gd(tpp)(acac) monoporphyrinate, including a bishydrated coordination sphere. Also, it has enabled the construction of a 3D structural model on which multiple scattering analyses were attempted. Monte Carlo simulation was used to validate the adjustments. EXAFS spectra analysis was carried out on the derivatives, displaying slight distortions in the lanthanide central-atom coordination geometry.

Synthesis and characterization of a new asymmetric bis-porphyrinato lanthanide complex presenting mixed hydrophilic-hydrophobic properties and its precursor form

The synthesis and spectroscopic characterization of a new family of heteroleptic porphyrinate double-deckers are reported. The investigated compounds are represented by the formulae La(III)H(TPyP)(TPP) and [La(III)(TMePyP)(TPP)]I(3). UV-vis spectroscopy of the title complexes confirms the presence of a strong pi-pi interaction between the macrocycles in each derivative. With (1)H and 2-D NMR data, we were able to distinguish two major NMR regions: the endo, between the bonded macrocycles, and the exo, outside the macrocycles, which are characteristic features of porphyrinic double-deckers. Finally, the electrochemical study confirms the strong pi-pi interaction for La(III)H(TPyP)(TPP) and completes this first approach for the investigation of this new family of derivatives.

Allosteric Binding of an Ag+ Ion to Cerium(IV) Bis-porphyrinates Enhances the Rotational Activity of Porphyrin Ligands

A series of cerium(IV) bis-porphyrinate double-deckers [Ce(bbpp)(2)] (BBPP=5,15-bis(4-butoxyphenyl)porphyrin dianion), [Ce(tmpp)(2)] (TMPP=5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin dianion), [Ce(tfpp)(2)] (TFPP=5,10,15,20-tetrakis(4-fluorophenyl)porphyrin dianion), [Ce(tmcpp)(2)] (TMCPP=5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin dianion), and [Ce(tmpp)(tmcpp)] was prepared. They bind three Ag(+) ions to their concave porphyrin pi subunits (pi-clefts) according to a positive homotropic allosteric mechanism with Hill coefficients (n(H)) of 1.7-2.7. The rotation rates of the porphyrin ligands in [Ce(bbpp)(2)] were evaluated to be 200 s(-1) at 20 degrees C (DeltaG$\rm{^{\ne }_{293}}$=14.1 kcal mol(-1)) and 220 s(-1) at -40 degrees C (DeltaG$\rm{^{\ne }_{233}}$=11.0 kcal mol(-1)) without and with Ag(+) ions, respectively. These results consistently support our unexpected finding that Ag(+) binding can accelerate rotation of the porphyrin ligand. On the basis of UV-visible, (1)H NMR, and resonance Raman spectral measurements, the rate enhancement of the rotational speed of the porphyrin ligands is attributed to conformational changes of the porphyrin in cerium(IV) bis-porphyrinate induced by binding of Ag(+) guest ions in the clefts. This novel concept of positive homotropic allosterism is applicable to the molecular design of various supramolecular and switch-functionalized systems.

Electronic structure, chemical bond, and optical spectra of metal bis(porphyrin) complexes: a DFT/TDDFT study of the bis(porphyrin)M(IV) (M = Zr, Ce, Th) series

The electronic absorption spectra of the bis(porphyrin) sandwich complexes of the metals Zr, Ce, and Th are studied with time-dependent density functional theory (TDDFT). A ground-state electronic structure analysis reveals that the highest occupied one-electron levels are, as expected, composed of the porphyrin a(1u) and a(2u) highest occupied orbitals (the Gouterman orbitals), but the level pattern is not simply a pair of low-lying nearly degenerate in-phase combinations and a pair of high-lying approximately degenerate antibonding combinations. Instead, the a(1u) split strongly and the a(2u) do not. Since the calculated spectrum agrees very well with experiment, the assignment leaves little doubt that although the experimental spectrum has porphyrin-like features, such as the well-known Q and B bands, the actual composition of the states is rather different from that in porphyrin. In particular the strong mixing of a(1u) --> e(g) and a(2u) --> e(g) is absent, there is mixing with excitations of non-Gouterman type, and, in Ce, ring to metal charge-transfer transitions play an important role. The composition of the states as calculated in this work does not lead to a classification of the excitations as purely "excitonic" or "charge-resonance".

Comparative study of structure-properties relationship for novel beta-halogenated lanthanide porphyrins and their nickel and free bases precursors, as a function of number and nature of halogens atoms

The synthetic route of partially beta-halogenated via a "metal-assisted" reaction and perhalogenated terbium complexes is described. This protocol allows the facile insertion of the halogens (bromines or chlorides) to the porphyrin peripheral positions. The electronic absorption spectra and the redox potentials of the free porphyrins as well as the terbium complexes are dramatically affected as the number of halogen atoms increase. In fact, two antagonistic effects are responsible for that, the inductive and the distortion effects on the porphyrin ring. They result in a red shift for the Soret band and a stabilization/destabilization of the HOMOs/LUMOs which in turn is manifested by variations on the redox potentials. The novel crystal structure of the Ni(Cl(8)TPP) is discussed in great detail and compared with the previously reported structures of Tb(Cl(8)TPP) (OAc)(DMSO)(2) x 3PhCH(3) x MeOH and H(2)(Br(8)TPP), as well as with other perhalogenated nickel porphyrins available in the literature.

Synthesis, structure, spectroscopic properties, and electrochemistry of rare earth sandwich compounds with mixed 2,3-naphthalocyaninato and octaethylporphyrinato ligands

A series of 14 heteroleptic rare earth sandwich complexes [M(III)-(nc)(oep)] (M=Y, La-Lu except Ce and Pm; nc=2,3-naphthalocyaninate; oep = octaethylporphyrinate) have been prepared by a one-pot procedure from corresponding [M(acac)3] . nH2O (acac = acetylacetonate), metal-free porphyrin H2(oep), and naphthalonitrile the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in n-octanol. The molecular structures of four of these complexes (M = Sm, Gd, Y, Lu) are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The interplanar distance decreases from 2.823 to 2.646 A along the series as a result of lanthanide contraction. The whole series of complexes have also been characterized spectroscopically. All the electronic absorptions, except the two B-bands due to nc and the oep rings, are metal-dependent, indicating that there are substantial pi-pi interactions. The hole or the unpaired electron in these double-deckers is delocalized over both macrocyclic ligands, as evidenced by the co-appearance of the IR marker bands for the nc*- (1315-1325 cm(-1)) and oep*- (1510-1531 cm(-1)) T radical ions. Three one-electron oxidation couples and up to three one-electron reduction couples have been revealed by electrochemical methods. All the potentials are linearly dependent on the size of the metal center. The changes in absorption spectra during the first electro-oxidation and reduction of the La(III), Eu(III), and Y(III) double-deckers have also been studied spectroelectrochemically. The spectral data recorded for [M(III)(nc)(oep)]-(M = Y, La-Lu except Ce and Pm) reduced chemically with hydrazine hydrate are in accord with those obtained by spectroelectrochemical methods. The first heteroleptic naphthalocyaninate-containing triple-deckers [M(III)2(nc)-(oep)2] (M = Nd, Eu) have also been prepared by a raise-by-one-story method by using [M(III)(nc)(oep)] (M = Nd, Eu), [M(acac)3] . nH2O (M = Nd, Eu), and H2(oep) as starting materials. The compounds adopt a symmetrical triple-decker structure with two outer oep rings and one inner nc ring, which has been confirmed by 'H NMR spectroscopy and X-ray structural determination of the Nd complex. Both compounds give a near-IR absorption at 1021 nm (for M=Nd) or 1101 nm (for M = Eu), which has rarely been observed for neutral (or hole-free) triple-decker complexes and can be ascribed to the lowest-energy Q'(0, 0) transition. Similarly to the double-decker analogues. these triple-decker complexes undergo a series of one-electron transfer processes with a relatively small potential gap (1.1 -1.2 V) between the first oxidation and the first reduction.

XAFS study of gadolinium and samarium bisporphyrinate complexes

The comparative X-ray absorption spectroscopy study of gadolinium and samarium bisporphyrinate complexes represented by the formulas Gd(III)H(oep)(tpp), Gd(III)(oep)(2), Gd(III)H(tpp)(2) and Sm(III)H(oep)(tpp), Sm(III)(oep)(2), Sm(III)H(tpp)(2) is reported. The XAFS spectra are recorded on the LURE-DCI storage ring (Orsay, France) in transmission mode on the microcrystalline samples at the Gd and Sm L(3) edges. The local environment for Ln(3+) ions has been reconstructed applying one-shell and two-shell XAFS analysis procedures. The protonated and nonprotonated bisporphyrinate complexes present different XAFS features. After our analysis on the title derivatives, the gadolinium ion (at 80 K) is found to be bonded: (i) to eight nitrogen atoms at R(Gd-N) 2.50 A, for Gd(III)(oep)(2) [Debye-Waller (DW) factor 0.004 A(2)]; (ii) to seven nitrogen atoms at R(Gd-N) 2.49 A, for Gd(III)H(oep)(tpp) [DW factor 0.005 A(2)] and one nitrogen at long distance; and (iii) to six nitrogen atoms at R(Gd-N) 2.50 A [DW factor 0.006 A(2)] and two nitrogen atoms at long distance for Gd(III)H(tpp)(2). A similar coordination sphere has been detected for the corresponding Sm derivatives. So, the samarium ion (at room temperature) is bonded: (i) to eight nitrogen atoms at R(Sm-N) 2.53 A, for Sm(III)(oep)(2) [DW factor 0.006 A(2)]; (ii) to seven nitrogen atoms at R(Sm-N) 2.53 A, for Sm(III)H(oep)(tpp) [DW factor 0.006 A(2)] and one nitrogen at long distance; and (iii) to six nitrogen atoms at R(Sm-N) 2.50 A, for Sm(III)H(tpp)(2) [DW factor 0.006 A(2)] and two nitrogen atoms at long distance. As far as concerns Ln(III)(oep)(2) complexes, the increase of Ln-N distance in the series Gd(3+) < Eu(3+) < Sm(3+) reflects an increase in the ionic radii, which are in good agreement with previously published XRD data on Eu(III)(oep)(2). Moreover, the protonated Ln(III)H(oep)(tpp) and Ln(III)H(tpp)(2) complexes possess systematically shorter distances of about 0.02 A between the XAFS and XRD data. This difference is attributed to the asymmetry of the distribution concerning Ln-N distances.

Formation of charge-transfer complexes from neutral bis(porphyrin) sandwiches

Lanthanide(III) bis(porphyrin) sandwich complexes of octaethyltetraazaporphyrin (OETAP) were synthesized and characterized by UV-vis, IR, and NMR spectroscopies. Cyclic voltammetry results indicate that these neutral sandwich complexes are very easily reduced. Charge-transfer reactions were performed in solution with Ln-(OETAP)2 sandwiches and zirconium(IV) bis(porphyrin) sandwiches. The lanthanide sandwiches partially oxidize the zirconium sandwiches in solution, and a solvent dependence of the charge-transfer reaction was observed. The solid-state properties of these charge-transfer materials were also studied. Magnetic susceptibility results suggest weak intermolecular interactions between the sandwiches. The conductivities of the charge-transfer species are greatly improved relative to those of the insulating undoped sandwiches, but the conductivities are in the lower semiconducting region. The low conductivity values are thought to be due to poor intermolecular overlap.

Synthesis and Physicochemical Characterization of Protonated and Deprotonated Forms in Heteroleptic Lanthanide(III) Porphyrinate Double-Deckers. X-ray Structure of Gd(III)H(oep)(tpp) at 298 and 21 K

The synthesis, spectroscopic characterization, and electrochemical study of eleven heteroleptic and their corresponding homoleptic lanthanide sandwiches are reported. Studies in solution have been carried out in solvents of different basicity, in order to elucidate the equilibrium between the protonated and deprotonated form of these complexes. The investigated compounds are represented by the formulas Ln(III)H(oep)(tpp) and [Ln(III)(oep)(tpp)](-) corresponding to the protonated and deprotonated forms, respectively (in the case of heteroleptic), and the formulas Ln(III)H(tpp)(2) and [Ln(III)(tpp)(2)](-) (in the case of the homoleptic porphyrin double-deckers), where Ln Nd,., Lu (except Pm), oep = 2,3,7,8,12,13,17,18-octaethylporphyrinate, and tpp = 5,10,15,20-tetraphenylporphyrinate). Various spectroscopic methods are used for the physicochemical characterization of the title complexes. The electronic spectra of the complexes above present different features in CH(2)Cl(2) and in DMF. In the latter solvent they reveal features similar to those of the analogous actinide(IV) porphyrin double-decker. The electrochemical studies carried out in CH(2)Cl(2) and THF demonstrate clearly that the redox behavior of the double-deckers, heteroleptic or homoleptic, is strongly dependent on the proton on the porphyrinic core. In CH(2)Cl(2), four reversible oxidation processes and two quasi-reversible waves are observed for the protonated species in both homo- and heteroleptic double-deckers. In contrast, two oxidations and two reductions are observed in THF for the homoleptic derivatives, while the corresponding heteroleptic ones undergo three oxidations and one reduction process. The structure of the new heteroleptic double-decker Gd(III)H(oep)(tpp) was determined by X-ray diffraction at 298 and 21 K. Both structures are compared with the first analogous structure of Sm(III)H(oep)(tpp). According to the spectroscopic and structural data reported for the heteroleptic protonated derivatives, the oep macrocycle is the favored binding site of the proton in solutions as well as in the solid state.

Bridged Aminotroponiminate Complexes of Lanthanum

The reaction of the new ligand 1,3-di(2-(N-isopropylamino)troponimine)propane, H(2)[(iPr)TP], with KH affords K(2)[(iPr)TP]. The salt of this new ligand is a useful starting material for the preparation of the lanthanum compounds [[(iPr)TP](3)La(2)(THF)](2) and [[(iPr)TP]LaCl(THF)](2), respectively. These metal complexes were characterized by NMR and X-ray crystallography. In contrast to macrocyclic ligands the [(iPr)TP](2)(-) anion shows a higher flexibility upon coordination and features two different coordination modes. Further reaction of [[(iPr)TP]LaCl(THF)](2) with 2 equiv of LiCH(SiMe(3))(2) or KN(SiMe(3))(2) in toluene affords the alkyl or amide derivatives [[(iPr)TP](2)LaE(SiMe(3))(2)] (E = CH, N) in high yield. Crystal data: [[(iPr)TP](3)La(2)(THF)](2), space group P2(1)/c, a = 19.860(2) Å, b = 17.691(3) Å, c = 21.333(3) Å, beta = 102.211(8) degrees, Z = 4, V = 7325.8 Å(3); [[(iPr)TP]LaCl(THF)](2), space group P2(1)/n, a = 12.848(3) Å, b = 32.902(7) Å, c = 16.215(3) Å, beta = 110.38(3) degrees, Z = 4, V = 6425(2) Å(3).