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Erbium(iii) complexes based on halogenated ligands.

The review presents data on the synthesis, structure, reactivity, and catalytic activity of alkyl derivatives of rare earth metals in the oxidation state +2 (Sm, Eu, Yb) and their analogues containing heavy alkaline earth metals (Ca, Sr, Ba). The synthetic aspects and structural features of this unique class of organometallic compounds, which contain highly reactive M–C bonds, including alkyl, α-silylmethyl, and also benzyl, diphenylmethyl, and triphenylmethyl derivatives are considered. The bibliography includes 157 references.

2,2-Bis[2-(dimethylamino)-5-methylphenyl]acetic acid, Ar2CHCOOH (1) (Ar = 5-Me-2-Me2NC6H3), was synthesized by the carboxylation of s[2-(dimethylamino)-5-methylphenyl]-methyllithium, [Ar2CH]Li(TMEDA), with gaseous CO2. The reaction of 1 with the cationic bis(alkyl) complex [(Me3SiCH2)2Dy(THF)n][BPh4] (2: 1 molar ratio) unexpectedly afforded the tetracarboxylate complex [Dy(O2CCHAr2)4(Et2NH2)2][BPh4] (3), whereas the trinuclear oxo cluster [Dy3O(O2CHAr2)6(THF)4][BPh4] (4) was prepared from [(o-Me2NC6H4CH2)2-Dy(THF)n][BPh4]. In complex 4, three Dy3+ cations are linked by the μ3-oxo oxygen atom and six bridging μ2-κ1-O:κ1-O’-carboxylate ligands. According to the X-ray diffraction data, NMe2 groups of the diphenylmethanide moiety are not coordinated to Dy3+ cations in complexes 3 and 4.

The synthesis, structures and reactivity of isolable LnII (Ln = Sm, Eu, Yb) alkyl complexes are discussed. The application of LnII alkyl derivatives in a variety of catalytic reactions is considered as well.

We report the synthesis and structures of three luminescent dysprosium(iii) complexes based on fluorinated alkoxide ligands of formulas [Dy(L1)2(THF)4][BPh4]·0.5THF (1), [Dy(L2)2(THF)5][BPh4]·2.5THF (2) and [Dy(L3)2(THF)5][BPh4]·2THF (3) (L1 = (CF3)3CO-, L2 = C6F5C6F4O-, L3 = C6F5C(CH3)O-). Despite the different dysprosium ion geometries (octahedral vs. distorted pentagonal bipyramidal), these systems exhibit a single-molecule magnet (SMM) behavior, but with distinct relaxation dynamics. Moreover, a typical dysprosium-based luminescence is observed for the three complexes, which make them bifunctional magneto-luminescent SMMs. Remarkably, complex 3 exhibits a high anisotropy barrier of 1469 cm-1 and a blocking temperature of 22 K, making it one of the most performant alkoxide-based SMMs with the highest blocking temperature for a luminescent SMM.

The outcome of salt metathesis reactions between the equimolar amounts of LnCl3 and dimeric potassium diphenylmethanide {[2,2′-(4-MeC6H3NMe2)2CH]K(THF)}2 depends on the rare-earth metal ion. In the case of ScIII and YIII, the reactions afford chlorido-bis(diphenylmethanido) complexes {[2,2′-(4-MeC6H3NMe2)2CH]2LnIII(μ-Cl)}2, in which the diphenylmethanido ligands perform bidentate κ2-CN coordination according to the X-ray data. For YbIII and SmIII, these reactions result in the spontaneous reduction of LnIII to LnII and the formation of known bis(diphenylmethanido) complexes [2,2′-(4-MeC6H3NMe2)2CH]2LnII and the product of oxidative coupling of diphenylmethanido anions.

The exchange reactions of equimolar amounts of potassium penta(benzyl)cyclopentadienide CpBn5K (CpBn5 = C5(CH2Ph)5) and SmI2(THF)2 or YCl3 afforded the corresponding half-sandwich derivatives [CpBn5Sm(DME)(μ-I)]2 (1) and [CpBn5YCl2(THF)]2[KCl(THF)2] (2). According to the X-ray diffraction data, the metal ions in complexes 1 and 2 are coordinated by CpBn5 ligands in a η5-fashion. The difference is that there is a short contact between the SmII cation and one benzyl group of the cyclopentadienyl ligand in structure 1, whereas such interaction is absent in structure 2.

We report the synthesis, structures, and magnetic investigations of two new octahedral dysprosium complexes, based on the original N-heterocyclic carbene (NHC) tridentate bis(phenoxide) ligand, of the respective formulas

We report the synthesis, structures, magnetic and luminescence properties of a series of three-blade propeller homoleptic lanthanide complexes [LnL3](ClO4)3·H2O·2MeCN (Ln = Eu (1), Tb (2), Dy (3), Er (4), Yb (5), Gd (6); L = 2,6-bis(1-methyl-imidazol-2-yl)pyridine). The Eu, Tb, and Dy analogues exhibit the characteristic lanthanide-based luminescence. Remarkably, the mixed Eu/Tb complex with a metal ratio of 1 : 10 can be used as a ratiometric thermometer in the solid-state between 130 and 220 K with the maximum value of Sr = 6.6% K−1 within the range of 150-170 K. Theoretical calculations allow not only modelling of the luminescence properties of pure complexes but also rationalization of the performances of the mixed Eu/Tb thermometers published

New neutral bis(alkyl) Sc and Y complexes [N,Npy,N-]Ln(CH2SiMe3)2(THF)n [n = 0, Ln = Sc (1Sc), Y (1Y); n = 1, Ln = Y (1YTHF)] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,Npy,N-]H and metal precursor Ln(CH2SiMe3)3(THF)2 in toluene at 0 °C. Depending on the work-up conditions, yttrium bis(alkyl)s were isolated as either a pentacoordinate Lewis base free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Y) or as a hexacoordinate THF adduct [N,Npy,N-]Y(CH2SiMe3)2THF (1YTHF). For the smaller Sc ion the only solvent-free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Sc) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes 1Ln (Ln = Y, Sc) and 1YTHF were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/AliBu3 (borate = [HNMe2Ph][B(C6F5)4] or [Ph3C][B(C6F5)4]), applied to isoprene (IP) polymerization, providing moderate activity albeit high selectivity with predominant formation of 1,4-cis polyisoprene (up to 99%). The same complexes proved to be effcient catalysts also for the intermolecular hydrolelementation of styrene with various EH sustrates (pyrrolidine, morpholine, Ph2PH, PhPH2, PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(C6F5)3, selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO2 hydrosylilation to CH4 in the presence of organosilanes as reducing agents (PhMe2SiH, PhSiH3, Et2MeSiH).

Ln(II) (Ln = Yb, Sm) and Ca(II) [NCsp3N] pincer type diarylmethanido complexes [2,2′-(4-MeC6H3NMe2)2CH]2M (M = Yb (2), Sm (3), Ca (4)) coordinated by a tridentate diarylmethanido ligand were synthesized through salt metathesis reactions of {[2,2′-(4-MeC6H3NMe2)2CH]K(THF)}2 and MI2(THF)2. X-ray analysis revealed that both diarylmethanido ligands in 2–4 are tridentate and coordinate to the metal centers via central carbon and two nitrogen atoms of NMe2 groups resulting in [NCsp3N] pincer coordination. In one of the five-membered MCCCN metallacycles in each tridentate diarylmethanido ligand, metal–arene interactions were detected and the coordination mode of [NCsp3N] ligands in 2–4 can be classified as κ1-N:η4-CCCN. A dynamic behavior involving the exchange between NMe2 groups and THF molecules in the coordination sphere of the M(II) ion was detected in solution. Complexes 2–4 proved to be catalytically active in a variety of reactions of C–C and C–E (E = Si, P, N, S) bond formation. Yb(II) 2 and Ca(II) 4 complexes catalyze intermolecular hydrobenzylation of styrene with 2-methyl and 2,6-dimethyl pyridines. Complex 2 demonstrates high chemo- and regioselectivities and is the first Ln(II) catalyst for intermolecular C–C bond formation. Complexes 2–4 were found to be efficient and selective precatalysts for intermolecular hydroelementation of olefins and acetylenes with various EH substrates (E = Si, P, N, S). Complexes 2–4 have demonstrated their versatility for intermolecular C–E bond formation and allow the realization of hydroamination, hydrophosphination, hydrosilylation and hydrothiolation of styrene and phenylacetylene. Moreover, 2–4 were found to be active in the catalysis of challenging transformations such as hydrosilylation and hydrophosphination of internal double CC and triple CC bonds.

The reaction of the amidinatehydride complex of divalent ytterbium [(Amd)YbII(μ2-H)]2 (Amd is {tert-BuC(NC6H3-iso-Pr2-2,6)2}) with BPh3 proceeds with the cleavage of the B−C bonds and affords the Yb(II)[(Amd)YbII(μ2-H3BPh)]2 complex containing the phenyltrihydroborate anion [PhBH3]−. The X-ray diffraction analysis (СIF file CCDC no. 1902290) shows that the [PhBH3]− anions in the complex are bridging. The “nonclassical” κ1-amido-η6-arene coordination mode to the Yb2+ ion is retained for the amidinate ligand.

This review is focused on recent advances in the ring-opening polymerization of lactide and lactones (mainly caprolactone and β-butyrolactone) which were achieved due to the application of the initiating systems based on rare-earth complexes.

On treatment of the yttrium bis(alkyl) complex [ArNC(=CH2)C(Me)=NAr]Y(CH2SiMe3)2(THF) (I, Ar = C6H3-iso-Pr2-2.6) containing an amide-imine ligand, with molecular hydrogen, hydrogenation of the C=N and C=C bonds takes place along with hydrogenolysis of Y−C bonds. The reaction is also accompanied by redistribution of nitrogen ligands and results in the formation of the yttrium complexes [ArNCH(Me)CH(Me)NAr]Y[ArN(=CH2)CH(Me)N(H)Ar](THF) (IIMeMe) and [ArNCH(Me)-C(=CH2)NAr]Y[ArN(=CH2)CH(Me)N(H)Ar](THF) containing, the monoanionic ene-amide-amine moiety [ArNC(=CH2)CH(Me)N(H)Ar]−, together with the dianionic diamide ligands [ArNCH(Me)CH(Me)NAr]2− or [ArNCH(Me)C(=CH2)NAr]2− (CIF file CCDC no. 1873206).

International audience; We report the synthesis, structures, magnetic and luminescent properties of a series of heteroleptic lanthanide complexes based on a tripodal tetradentate ligand [Ln(Tpma)(NO 3) 3 ]•nMeCN (Ln = Eu (1), Tb (2), Dy (3), Er (4), n = 0.5; Yb (5), n = 0; Tpma = tris((1H-pyrazol-1-yl)methyl)amine). The europium, terbium and dysprosium analogues exhibit a lanthanide-based luminescence, while dysprosium, erbium and ytterbium compounds show a field-induced slow relaxation of their magnetization involving Raman and direct processes.

A series of alkali-metal alkyl complexes containing a tridentate benzhydryl ligand, [2,2′-(4-MeC6H4NMe2)2CH]Li(TMEDA) (1TMEDA), [2,2′-(4-MeC6H4NMe2)2CH]Na(THF)3 (2THF), {[2,2′-(4-MeC6H4NMe2)2CH]K(THF}2 (3THF), and [2,2′-(4-MeC6H4NMe2)2C(SiMe3)]K (5), were synthesized and structurally characterized. Smaller Li and Na ions form the monomeric complexes 1TMEDA and 2THF featuring η4-CCCN coordination of the [2,2′-(4-MeC6H4NMe2)2CH]− ligand, while the larger K affords the dimeric complex 3THF, in which two different types of metal–ligand bonding, μ-η5-pentadienyl-κ2-NN and μ-κ3-CNN:η6-arene are realized. Application of the Me3Si-substituited analogue [2,2′-(4-MeC6H4NMe2)2C(SiMe3)]− leads to the formation of the 1D coordination polymer {[2,2′-(4-MeC6H4NMe2)2C(SiMe3)]K}∞ (5) with μ-η3:η6 bridging coordination of the ligands to potassium ions.

New bis(amidinate) complexes of calcium, [2,6-Pri2C6H3NC(But)NC6H4OMe-2]2Ca(DME) (2), and divalent ytterbium, [2,6-Pri2C6H3NC(But)NC6H4OMe-2]2Yb (4), were synthesized by the transamination of the bis(amide) derivatives [(Me3Si)2N]2M(THF)2 (M = Ca, Yb) with two equivalents of amidine 2,6-Pri2C6H3N=C(But)N(H)C6H4OMe-2, in which one nitrogen atom bears an o-methoxyphenylene moiety capable of coordinating a metalion. An X-ray diffraction study showed that, despite very similar ionic radii of Ca2+ and Yb2+, the amidinate ligands in complexes 2 and 4 bind to these ions in different coordination modes. In the calcium complex, both ligands adopt a κ2-N, O-chelating coordination mode. In the divalent ytterbium compound, one ligand is chelating and binds to the metalion in a κ2-N, O-coordination mode, while the second ligand is coordinated via both the N and O (κ2) atoms and the arene ring of the 2,6-Pri2C6H3 moiety (η6-coordination mode).

Oxidation of 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino) benzene] by H2O2 or S8 in toluene affords two new PCP-type pincer ligands. The methylene group deprotonation in the new ligands as well as in their precursor by n-BuLi or LiCH2SiMe3 failed, while the methylene group in the precursor 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino)benzene] was readily metallated by Lochmann–Schlosser superbase to form the unstable potassium complex which in turn was readily transformed into new {5-But-2-[4-But-2-(Ph2P)C6H3(Ph)CH]C6H3P(Ph)K(OEt2)}2 complex due to phenyl group migration.

Lithium silylamides 1,8-C10H6[N(SiMe3)Li(L)]2 (L = Et2O (); L = TMEDA (1TMEDA)), when treated with PhC[triple bond, length as m-dash]N, formed the adducts 1,8-C10H6[N(SiMe3)Li(N[triple bond, length as m-dash]CPh)(OEt2)][N(SiMe3)Li(OEt2)] () and 1,8-C10H6[N(SiMe3)Li(N[triple bond, length as m-dash]CPh)][N(SiMe3)Li(TMEDA)] (2TMEDA) containing one benzonitrile molecule coordinated to Li ion while the second molecule retains a coordinated L ligand. The salt metathesis reactions of LnCl3 (Ln = Y, Sm) with equimolar amounts of and 2TMEDA (THF, 4 h, 40 °C) resulted in benzonitrile insertion and formation of new dianionic amido-amidinate ligands. The reactions of with LnCl3 afforded ionic chloro complexes [{1,8-C10H6[NSiMe3][NC(Ph)NSiMe3]}{1,8-C10H6[N(H)SiMe3][NC(Ph)NSiMe3]}LnCl][Li(L)n] (Ln = Y, L = THF, n = 4 (3Y), Ln = Sm, L = DME, n = 3 (3Sm)), while the reaction of 2TMEDA and YCl3 leds to the formation of the neutral salt-free yttrium chloro complex {1,8-C10H6[NSiMe3][NC(Ph)NSiMe3]}YCl(TMEDA) (4). The treatment of 3Y and 4 with tBuOK enabled the synthesis of tert-butoxides [{1,8-C10H6[NSiMe3][NC(Ph)NSiMe3]}{1,8-C10H6[N(H)SiMe3][NC(Ph)NSiMe3]}YOtBu][Li(THF)4] (7) and {1,8-C10H6[NSiMe3][NC(Ph)NSiMe3]}YOtBu(TMEDA) (8). Complexes 7 and 8 were evaluated as initiators for the ring opening polymerization of rac-lactide. Neutral tert-butoxide complex 8 demonstrated significantly higher activity compared to that of ionic 7.

The reaction of equimolar amounts of ytterbocene (C5Me4H)2Yb(THF)2 and iminopyridine 2,6-Pri2C6H3N=CH(C5H4N) accompanied by the one-electron oxidation of the ytterbium ion produced the unique lanthanide complex (C5Me4H)2YbIII[2,6-Pri2-C6H3NCH(C5H4N)]–• with the iminopyridine radical-anionic ligand. The structure of the complex in the crystalline state was established by X-ray diffraction and its magnetic properties were studied in the temperature range of 1.8—300 K.

Reactions of equimolar amounts of RN=C=NR (R = Pri, Cy) and 6-Me-C5H3N-2-CH2Li prepared in situ by metallation of 2,6-dimethylpyridine with n-butyllithium afforded corresponding lithium amidinates [Li{6-Me-C5H3N-2-CH2C(NPri)2}]•1/3THF (1) and [Li{6-MeC5H3N-2-CH2C(NCy)2}]4 (2) containing new tridentate amidinate ligands. The salt metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with 1 (1: 1 molar ratio, THF) result in neutral amidinate bisborohydride complexes [Ln{6-Me-C5H3N-2-CH2C(NPri)2}(BH4)2(THF)2} (Ln = Y (3), Nd (4)). According to X-ray data, both compounds are monomeric, terminal borohydride ligands being coordinated to the rare earth metal atom in η3-fashion. Nitrogen atoms of the pyridine fragments of amidinate ligands are not involved in complexation with metal cations. Complexes 3 and 4 in combination with [Ph3C][B(C6F5)4] and AlBu 3 i (1: 1: 10 molar ratio) exhibit catalytic activity in isoprene polymerization.

A reaction of Sc, Y, and Yb amidopyridinate dichlorides with the corresponding amount of LiCH2SiMe3 was used to synthesize bis(trimethylsilylmethyl) complexes (Ap)Ln(CH2SiMe3)2-(THF) (Ap is N-mesityl-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap9Me), Ln = Y (2); Ap is N-(2,6-diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap*), Ln = Sc (3), Yb (4)). An exchange reaction of yttrium amidopyridinate dichloride derivative 1 with 4 equiv. of ButLi in hexane gave the corresponding di-tert-butyl derivative Ap9MeY(But)2(THF) (5). Molecular structures of complexes 3 and 4 were established by X-ray diffraction. A method of the ligand solid angles was used to calculate the completion degree of the metal atom coordination sphere for the series of isomorphic derivatives (Ap*)Ln(CH2SiMe3)2(THF) containing the central metal ions with different ionic radii (Sc, Y, Yb, Lu). According to this method, the amidopyridinate ligand solid angle in these complexes virtually does not vary, while the solid angles of coordinated THF molecule and alkyl ligands vary within a wide range.

The reactions of bis(pyrazolyl)methanes CH2(C3HN2R2-3,5)2 (R = Me, tBu) with Y(CH2SiMe3)3(THF)2 and LY(CH2SiMe3)2(THF)n (L = amidopyridinate (Ap′), amidinate (Amd), tridentate amidinate bearing 2-methoxyphenyl pendant in a side arm (AmdOMe) and pentamethylcyclopentadienyl (Cp*); n = 0, 1) were investigated. CH2(C3HN2tBu2-3,5)2 turned out to be inert in these reactions, while less bulky CH2(C3HN2Me2-3,5)2 easily undergoes metalation by yttrium alkyls. The reaction of Y(CH2SiMe3)3(THF)2 with CH2(C3HN2Me2-3,5)2 regardless of the molar ratio of the reagents affords a homoleptic tris(alkyl) species, Y[CH(C3HN2Me2-3,5)2]3 (1). However, the reactions of equimolar amounts of LY(CH2SiMe3)2(THF)n and CH2(C3HN2Me2-3,5)2 occur selectively with replacement of a sole CH2SiMe3 fragment and afford the related heteroalkyl complexes LY(CH2SiMe3)[CH(C3HN2Me2-3,5)2](THF)n (L = Ap′, n = 1 (6); Amd, n = 0 (7); AmdOMe, n = 1 (8); Cp*, n = 1 (9)) in good yields. The second equivalent of CH2(C3HN2Me2-3,5)2 does not react with het...

New amidopyridinate chloride complexes {[Ap´Y(THF)](μ2-Cl)2(μ3-Cl)Li(THF)}2, {[Ap9MeLn(THF)](μ2-Cl)3Li(THF)2}2 (Ln = Y, Nd, Sm), and {[Ap*Ln(THF)](μ2-Cl)3Li(THF)2}2 (Ln = Nd, Sm) were synthesized by the exchange reactions of lithium amidopyridinates ApLi(OEt2) (Ap´ is N-(2,6-diisopropylphenyl)-6-(2,6-dimethylphenyl)pyridine-2-amine; Ap9Me is N-mesityl-6-(2,4,6-triisopropylphenyl)pyridine-2-amine; Ap* is N-(2,6-diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridine-2-amine) with anhydrous rare earth chlorides. The X-ray diffraction study showed that the amidopyridinate chloride derivatives are heterobimetallic ate-complexes, in which two rare earth metal atoms are linked by bridging chloride ligands and bridging Cl—Li—Cl groups. The three-component system {[Ap*Nd(THF)](μ2-Cl)3Li(THF)2}2—AlBui 3—[Ph3C][B(C6F5)4] (1: 10: 1 molar ratio) catalyzes the isoprene polymerization.

International audience; A systematic study of reactions between Cp*Yb-2(THF) (Cp* = eta(5)-C5Me5, 1) and iminopyridine ligands (IPy = 2,6-(Pr2C6H3N)-Pr-i=CH(C5H3N-R), R = H (2a), 6-C4H3O (2b), 6-C4H3S (2c), 6-C6H5 (2d)) featuring similar electron accepting properties but variable denticity and steric demand, has provided a new example of steric control on the redox chemistry of ytterbocenes. The reaction of the unsubstituted IPy 2a with 1, either in THF or toluene, gives rise to the paramagnetic species Cp*Yb-2(III)(IPy)(center dot-) (3a) as a result of a formal one-electron oxidation of the Yb-II ion along with IPy reduction to a radical-anionic state. The reactions of 1 with substituted iminopyridines 2b-d, bearing aryl or hetero-aryl dangling arms on the 6 position of the pyridine ring occur in a non-coordinating solvent (toluene) only and afford coordination compounds of a formally divalent ytterbium ion, coordinated by neutral IPy ligands Cp*Yb-2(II)(IPy)(0) (3b-d). The X-ray diffraction studies revealed that 2a-c act as bidentate ligands; while the radical-anionic IPy in 3a chelates the Yb-III ion with both nitrogens, neutral IPy ligands in 3b and 3c participate in the metal coordination sphere through the pyridine nitrogen and O or S atoms from the furan or thiophene moieties, respectively. Finally, in complex 3d the neutral IPy ligand formally adopts a monodentate coordination mode. However, an agostic interaction between the Yb-II ion and an ortho C-H bond of the phenyl ring has been detected. Imino-nitrogens in 3b-d are not involved in the metal coordination. Variable temperature magnetic measurements on 3a are consistent with a multiconfigurational ground state of the Yb ion and suggest that the largest contribution arises from the 4f(13)-radical configuration. For complexes 3b and 3c the data of magnetic measurements are indicative of a Yb-II-closed shell ligand electronic distribution. Complex 3d is characterized by a complex magnetic behavior which does not allow for an unambiguous estimation of its electronic structure. The results are rationalized using DFT and CSSCF calculations. Unlike diazabutadiene analogues, 3a does not undergo a solvent mediated metalligand electron transfer and remains paramagnetic in THF solution. On the other hand, complexes 3b-d readily react with THF to afford 1 and free IPy 2b-d.

Metallacyclic neutral and ionic yttrium alkyl complexes coordinated by a dianionic ene-diamido ligand ([2,6-iPr2C6H3NC(Me)=C(Me)NC6H3iPr2-2,6] = L(1)) [L(1)]Y(CH2SiMe3)(THF)2 (2), {[L(1)]Y(CH2SiMe3)2}(-){Li(THF)4}(+) (3), [L(1)]Y(OEt2)(μ-Me)2Li(TMEDA) (4) were synthesized using a salt-metathesis approach starting from the related chloro complex [L(1)]Y(THF)2(μ-Cl)2Li(THF)2 (1) in 70, 85 and 72% yields respectively. The reactions of 2 with H2 or PhSiH3 afford the dimeric hydride {[L(1)]Y(THF)(μ-H)}2(μ-THF) (5) containing two μ-bridging hydrido and one μ-bridging THF ligands (91 and 85% yields). The X-ray studies of complexes 2, 3 and 5 revealed η(2)-coordination of the C=C fragment of an ene-diamido ligand to a Y cation. DFT calculations were carried out to give an insight into the metal-ligand bonding and especially the interaction between the metal and the ene-diamido ligand. The observed bonding of the ene-diamido fragment is found to reflect the acidity of the metal center in the complex that is partially overcome by a better donation from the double bond (better overlap with an empty d orbital at the yttrium center). The treatment of complex 4 with DME resulted in the C-O bond cleavage of DME and afforded a three nuclear methoxide oxide complex [{[L(1)]Y}3(μ(2)-OMe)3(μ(3)-O)](2-)[Li(DME)3](+)2 (6). Complexes 2, 3, 5 and 7 proved to be efficient precatalysts for the intermolecular hydrophosphination of styrene, 4-vinylpyridine, and 1-nonene with PhPH2 and Ph2PH as well as hydroamination of styrene and pyrrolidine.

Lithium silylamides 1,8-C

New heteroleptic Yb(II)-amide species supported by amidinate and 1,3,6,8-tetra-tert-butylcarbazol-9-yl ligands [2-MeOC6H4NC(tBu)N(C6H3-iPr2-2,6)]YbN(SiMe3)2(THF) (6) and [1,3,6,8-tBu4C12H4N]Yb[N(SiMe3)2](THF)n (n = 1 (7), 2 (8)) were synthesized using the amine elimination approach. Complex 6 features an unusual κ(1)-N,κ(2)-O,η(6)-arene coordination mode of the amidinate ligand onto Yb(II). Complexes 7 and 8 represent the first examples of lanthanide complexes with π-coordination of carbazol-9-yl ligands. Complexes 6 and 7, as well as the amidinate-Yb(II)-amide [tBuC(NC6H3-iPr2-2,6)2]YbN(SiMe3)2(THF) (5), are efficient precatalysts for the intermolecular hydrophosphination and hydroamination of styrene with diphenylphosphine, phenylphosphine, and pyrrolidine to give exclusively the anti-Markovnikov monoaddition product. For both types of reaction, the best performances were observed with carbazol-9-yl complex 7 (TONs up to 92 and 48 mol/mol at 60 °C, respectively).

Oxidation reactions of the Yb(II) hydride [{tBuC(NC6H3-2,6-iPr2)2}Yb(μ-H)]2 (1) with CuCl (1:2 molar ratio) and (PhCH2S)2 (1:1 molar ratio) revealed that the hydrido anion in 1 is a stronger reductant than the Yb(II) cation. Both reactions occur with evolution of H2 and afford the dimeric Yb(II) species [{tBuC(NC6H3-2,6-iPr2)2}Yb(μ-X)]2 (X = Cl (2), SCH2Ph (3)) in which a κ1-amido,η6-arene type of coordination of amidinate ligand is retained. Reaction of 1 with 2 equiv of (PhCH2S)2 results in oxidation of both Yb(II) and hydrido centers and leads to the formation of the Yb(III) complex [{tBuC(NC6H3-2,6-iPr2)2}Yb(μ-SCH2Ph)2]2 (4). Complex 4 can be also synthesized by oxidation of 3 with an equimolar amount of (PhCH2S)2. It was demonstrated that oxidation of the ytterbium center to the trivalent state leads to switching of the coordination mode of amidinate ligand from κ1-amido, η6-arene to “classical” κ1,κ1-N,N-chelating. Unlike Yb(III) bis(alkyl) species supported by bulky amidopyridinate ligands, the rea...

Two new amidines that contain a pendant Lewis base in the side arm, 2-MeOC6H4NC(tBu)NH(2,6-R2C6H3) (R = Me, iPr), were synthesized and successfully employed as tridentate ligands for the preparation of the dialkyl rare earth complexes [2-MeOC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2SiMe3)2(L)n {Ln = Y, Lu; R = Me, iPr; L = thf (n = 2), dme (n = 1)}. These ligands provided enhanced stability for the complexes. The X-ray structure determinations revealed that intramolecular coordination of the 2-MeOC6H4 group is realized if a thf molecule is coordinated to the metal center (Ln = Y, Lu), which results in the coordination number of six. The treatment of complex [2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(thf) with dme afforded a six-coordinate dme adduct in which the methoxy group of the amidinate ligand has drifted out from the metal coordination sphere. The reaction of [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) with 2,6-diisopropylaniline in hexane at 70 degrees C, regardless of the ratio of the reagent, afforded the six-coordinate diamido compound [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NHC6H3-2,6-iPr2)2(thf), for which intramolecular coordination of the oxygen atom of the side chain was detected by an X-ray study. Complex [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) was evaluated as a precatalyst for isoprene polymerization. The ternary system [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf)/[Ph3C][B(C6F5)4]/AliBu3provided isoprene polymerization with moderate activity but without control of the regioselectivity (3,4-regularity was slightly predominant at 52?%). Nevertheless, high 1,4-trans-selectivity was found (96%) for the 1,4-polyisoprenes. The obtained polyisoprene has a Mn of 13.0 x 10(4) and moderate polydispersity (2.12).

Some regularities of hydrosilylation of non-1-ene with phenylsilane catalyzed by yttrium and lutetium bisguanidinate hydride complexes {[(Me3Si)2NC(NR)2]2Ln(μ-H)}2 (Ln = Y, Lu; R = Pri, Cy (Cy is cyclohexyl)) have been studied. The addition of PhSiH3 to the double bond of non-1-ene in the presence of a {[(Me3Si)2NC(NPri)2]2Y(μ-H)}2 complex has the first order in olefin and zero order in phenylsilane. This indicates that the insertion of non-1-ene into the Ln-H bond is a rate determining stage of the process, whereas the metathesis of the Ln-C σ-bond upon the action of phenylsilane proceeds rapidly. The first example of successive double alkylation of phenylsilane with an olefin catalyzed by a rare-earth metal complex with the formation of tertiary silane has been discovered.

The reactions of anhydrous LnCl3 (Ln = Nd or Lu) with three equivalents of {(Me3Si)2NC(NR)2}Li (R = Pri or Cy; Cy is cyclohexyl) in THF afforded the corresponding tris(guanidinate) derivatives of lanthanides {(Me3Si)2NC(NR)2}3Ln (Ln = Nd, R = Pri, (1); Ln = Lu, R = Cy (2)), which were isolated after the recrystallization from hexane in 82 and 88% yields, respectively. The complex {(Me3Si)2NC(NCy)2}2{HC(NCy)2}Nd (3) containing two guanidinate ligands and one formamidinate ligand was isolated in attempting to synthesize the bis(guanidinate) borohydride derivative by the reaction of {(Me3Si)2NC(N-Cy)2}Na with Nd(BH4)3(THF)2 (in a molar ratio of 2: 1) in THF. This complex is apparently formed as a result of the fragmentation and redistribution of the guanidinate ligands. The X-ray diffraction study showed that in the crystalline state compounds 1–3 are mononuclear complexes containing no coordinated Lewis bases.

The reaction of equimolar amounts of YC13 and [1,8-C10H6(NSiMe3)2]Li2 in THF produced the complex {[1,8-C10H6(NSiMe3)2YCl(DME)]2(μ-Cl)}[Li(DME)3] (1), which was isolated by recrystallization from a DME—hexane mixture as yellow crystals in 82% yield. The reaction of complex 1 with (Me3Si)2NLi(Et20) (in a molar ratio of 1:2) in toluene gave the corresponding amide derivative [1,8-C10H6(NSiMe3)2YN(SiMe3)2(μ-Cl)]2[Li(DME)3]2 (2). The recrystallization of the reaction product from toluene afforded complex 2 in 73% yield. The X-ray diffraction study showed that in the crystalline state, compounds 1 and 2 consist of the isolated cationic and anionic moieties. The complex anions are dinuclear moieties with the bridging chlorine ligands.

The insertion of N,N′-dicyclohexylcarbodiimide at one of the Y-N bonds of the [(Me3Si)2N]3Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative { (Me3Si)2NC(N-cyclo-Hex)2}Y[N(SiMe)3]2 (1) (cyclo-Hex is cyclohexyl) in 72% yield. The reaction of equimolar amounts of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate, which was prepared in situ from {(Me3Si)2N}Na and N,N′-dicyclohexylcarbodiimide, and YbI2(THF)2 in THF gave the [{(Me3Si)2NC(N-cyclo-Hex)2}YbI(THF)2]2 complex (2). An attempt to use this procedure for the synthesis of the yttrium compound { (Me3Si)2NC(NSiMe3)2}2YCl containing the sterically more hindered guanidinate ligand unexpectedly led to the formation of the diamide chloride complex [{(Me3Si)2N}2Y(THF)(µ-Cl)]2 (3). The structures of complexes 1–3 were established by X-ray diffraction. Compound 1 is mononuclear. Complexes 2 and 3 are dinuclear and contain two µ2-bridging halide ligands.

The reaction of anhydrous SmCl3 with two equivalents of lithium N,N′-diisopropyl-N″-bis(trimethylsilyl)guanidinate in THF afforded the [{(Me3Si)2NC(NPri)2}2SmCl]2 complex (1) in 82% yield. Analogous reactions with YCl3 and GdCl3 produced the ate-complexes { (Me3Si)2NC(NPri)2}2Ln(µ-Cl)2Li(THF)2 (Ln = Y (2) and Gd (3)). The structures of complexes 1 and 2 were established by X-ray diffraction. The reaction of complex 1 with NaBH4 in hexane (20 °C) followed by treatment with dimethoxyethane yielded the unexpected product, { (Me3Si)2NC(NPri)2}Sm(µ3-BH4)2(DME) (5). X-ray diffraction study showed that both borohydride ligands in complex 5 are tridentate.

Addition of two Ln-H bonds of an Yb(II) hydrido complex supported by bulky amidinate ligand to a C≡C bond lead to the formation of 1,2-dianionic bibenzyl fragment. Both Yb(II) and hydrido centers are oxidized under the reaction conditions. The resulting Yb(II)-η(6) -arene interaction is surprisingly robust: the arene cannot be replaced from the metal coordination sphere when treated with Lewis bases.

Yttrium dialkyl complexes coordinated by 6-aryl-substituted amidopyridinate ligands undergo selective intramolecular sp2 or sp3 C−H bond activation. Upon treatment with PhSiH3 of the resulting Y−C(alkyl, aryl) or Y−C(alkyl,benzyl) systems, a σ-bond metathesis reaction takes place selectively at the Y−C(alkyl) bond, generating rare dimeric aryl−hydrido or benzyl−hydrido yttrium complexes, respectively.

A monoanionic amido-imino ligand system [(2,6-iPr2C6H3)N=C(Me)C(=CH2)N(C6H3-2,6-iPr2)](-) was successfully employed for the synthesis of monomeric dichloro [(2,6-iPr2C6H3)N=C(Me)C(=CH2)N(C6H3-2,6-iPr2)]LnCl2(THF)2 (Ln = Y, 2Y; Lu, 2Lu) and bis(alkyl) [(2,6-iPr2C6H3)N=C(Me)C(=CH2)N(C6H3-2,6-iPr2)]Ln(CH2SiMe3)2(THF) (Ln = Y, 4Y; Lu, 4Lu) species of yttrium and lutetium. Dichloro complexes 2Y and 2Lu turned out to be unstable in aromatic solvents. The ligand symmetrization reaction in the case of 2Y affords the yttrium complex coordinated by dianionic [(2,6-iPr2C6H3)NC(=CH2)C(=CH2)N(C6H3-2,6-iPr2)](2-) ligand, (2,6-iPr2C6H3)N=C(Me)C(Me)=N(C6H3-2,6-iPr2) and YCl3. On the contrary, bis(alkyl) species 4Y and 4Lu are rather stable and do not undergo such a transformation or thermal decomposition. The treatment of complex 4Y with DME resulted in C-O bond cleavage and the formation of a dimeric methoxy-alkyl species {[(2,6-iPr2C6H3)N=C(Me)C(=CH2)N(C6H3-2,6-iPr2)]Y(CH2SiMe3)(μ-OMe)}2 (5). The ternary systems 4Ln/AliBu3/borate (borate = [HNMe2Ph][B(C6F5)4] and [CPh3][B(C6F5)4]; molar ratio 1 : 10 : 1) performed high catalytic activity in isoprene polymerization and ability to convert into polymer 1000-5000 equivalents of isoprene in 20-120 min with quantitative conversion. The obtained polyisoprenes possessed high molecular weights (2.9 × 10(4)-4.1 × 10(4)) and moderate polydispersities (2.14-3.52). Predominant 3,4-regioselectivity (up to 78%) was observed.