Lutetium Alkyl Research Articles

Copolymerization of Lactide and Cyclic Carbonate via Highly Stereoselective Catalysts To Modulate Copolymer Sequences

The controlled ring-opening polymerizations of enantiopure (L-LA or D-LA) or racemic lactide (rac-LA) with achiral functionalized cyclic carbonates (TMCR) have been performed by using the aminobisphenolate yttrium and lutetium alkyl complexes or an organo-base catalyst DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), in combination with various alcohols as chain transfer agents. When using the highly heteroselective precatalyst 1Y, the copolymerization of rac-LA and TMCR afforded tapered copolymer poly(rac-LA-t-TMCR), while the copolymerization of enantiopure L-LA or D-LA, respectively, with TMCR gave pseudo-random product poly(L-LA-r-TMCR). When the low heteroselective rare-earth metal precatalysts or organic DBU were applied, the difference in the monomer distributions for the above two systems disappeared gradually. On the contrary, the monomer sequence distribution was not influenced by the types of chain transfer agents and TMCR. The kinetics study revealed that the competitive reaction ratios were rL-LA = ...

Renewable β-myrcene polymerization initiated by lutetium alkyl complexes ligated by imidophosphonamido ligand

β-imidophosphonamido ligated lutetium alkyl complex (NPNDipp)Lu(CH2SiMe3)2(THF) (NPNDipp = Ph2P(NC6H3 i Pr2-2,6)2) with the activation of Al i Bu3 and [Ph3C][B(C6F5)4] exhibited high catalytic activity, medium syndio-(rr = 66%) but remarkably high 3,4-regioselectivity for the polymerization of β-myrcene (MY). In sharp contrast, high isotactic 3,4-polymyrcene (PMY) (mm = 95%) was obtained by the precursor (NPNEt)Lu(CH2SiMe3)2(THF) (NPNEt = PPh2(NC6H3 i Pr2-2,6)(NC6H4-Et-2)) with less bulky substituents on the N-aryl ring.

Bis(pyrazolyl)carbazole as a Versatile Ligand for Supporting Lutetium Alkyl and Hydride Complexes

Two derivatives of a new bis(pyrazolyl)carbazole pincer ligand H(CzPzR), R = iPr and Me, and their syntheses are reported. Lutetium dialkyl complexes of the ligand (CzPzR)Lu(CH2SiMe3)2, R = iPr and Me, have been prepared and found to exhibit high thermal stability in solution. These organolutetium compounds are Lewis base free, and the solid-state structure of (CzPziPr)Lu(CH2SiMe3)2 revealed that the complex is monomeric with a trigonal-bipyramidal geometry. Hydrogenolysis of (CzPziPr)Lu(CH2SiMe3)2 afforded a trimetallic lutetium hydride complex that possesses five bridging hydride ligands. Notably, intramolecular C–H bond activation of the CzPziPr ligand was found to occur during the formation of this latter hydride complex, with metalation of a pyrazole carbon atom.

Cationic Tropidinyl Scandium Catalyst: A Perfectly Acceptable Substitute for Cationic Half-Sandwich Scandium Catalysts in cis-1,4-Polymerization of Isoprene and Copolymerization with Norbornene

Different nonmetallocene rare earth metal alkyl complexes such as monotropidinyl (Trop) scandium dialkyl complex (Trop)Sc(CH2SiMe3)2(THF) (1), ditropidinyl yttrium alkyl complex (Trop)2Y(CH2SiMe3)(THF) (3) as well as binuclear lutetium alkyl complex bearing one tetradentate dianionic 6-N-methyl-1,4-cycloheptadienyl (NMCH) ligand [(NMCH)Lu(CH2SiMe3)(THF)]2 (2) have been synthesized in high yields via one-pot acid–base reaction by using of the tris(trimethylsilylmethyl) rare earth metal complexes with the readily available natural product tropidine. The polymerization experiments indicate that the monotropidinyl scandium dialkyl complex 1 displays reactivity akin to that of the analogous monocyclopentadienyl scandium dialkyl complexes. In the presence of activator and a small amount of AlMe3, complex 1 exhibits similar activities (up to 1.6 × 106 g molSc–1 h–1) but higher cis-1,4-selectivities (up to 100%) than (C5H5)Sc(CH2SiMe3)2(THF) (cis-1,4-selectivity as 95%) in the isoprene polymerization, yielding the pure cis-1,4-PIPs with moderate molecular weights (Mn = 0.5–11.2 × 104 g/mol) and bimodal molecular weight distributions (Mw/Mn = 1.48–6.07). Moreover, the complex 1/[Ph3C][B(C6F5)4/AliBu3 ternary system also shows good comonomer incorporation ability in the copolymerization of isoprene and norbornene similar to the [C5Me4(SiMe3)]Sc(η3-CH2CHCH2)2/activator binary system, affording the random isoprene/norbornene copolymers with a wide range of isoprene contents around 57–91 mol % containing cis-1,4 configuration up to 88%.

A cascade reaction: ring-opening insertion of dioxaphospholane into lutetium alkyl bonds

Geometrically constrained dioxaphospholane rings were incorporated into a bis(phosphinimine)carbazole ligand (HL) in an effort to generate an ancillary ligand system that is capable of supporting reactive lutetium alkyl functionalities and resistant to cyclometalation reactivity. This new ligand was used to prepare a lutetium dialkyl species, LLu(CH2SiMe3)2; however, the complex exhibited low thermal stability at ambient temperature. This dialkyl compound was found to be highly susceptible to a cascading inter- and intramolecular reaction that resulted in the sole formation of an asymmetric bimetallic tetraalkoxide complex. The product of this reaction, generated by the ring-opening insertion of dioxaphospholane moieties into lutetium-carbon bonds, was characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction.

Synthesis and Structural Features of Boratabenzene Rare-Earth Metal Alkyl Complexes

A series of solvent-free boratabenzene rare-earth metal alkyl complexes (C5H5BR)(2)LnCH (SiMe3)(2) (9: R = NEt2, Ln = Y; 10: R = NPh2, Ln = Y; 11: R = CH3, Ln = Y; 12: R = NPh2, Ln = Sm; 13: R = NPh2, Ln = Dy; 14: R = NEt2, Ln = Lu; 15: R = NPh2, Ln = Lu; 16: R = Me, Ln = Lu) were synthesized. The solid-state structures of 10, 13, and 15 were determined by single-crystal X-ray diffraction. The crystal structures of 10,13, and 15 feature highly unsymmetrical coordination of the alkyl ligands and short Ln-C(alkyl) distances. The diamagnetic yttrium and lutetium alkyl complexes, 9-11 and 14-16, were characterized by (H-1, C-13, B-11) NMR spectroscopy. The Ln-C alpha H alpha, (H-1 NMR: delta 0.68-0.99 ppm) and Ln-C alpha H alpha (C-13 NMR: delta 33.9-39.1 ppm) resonances of these boratabenzene rare-earth metal alkyl complexes are rather downfield in comparison with those of the bis-Cp rare-earth metal alkyl complexes. Y-89 NMR spectra of the boratabenzene yttrium alkyl complexes 9-11 and the Cp complex (C5H4Me)(2)YCH(SiMe3)(2) were recorded. The Y-89 NMR chemical shifts for 9, 10, and 11 are 176.1, 170.0, and 162.2 ppm, respectively, which are significantly downfield in comparison with that of (C5H4Me)(2)YCH(SiMe3)(2) (44.0 ppm).

Trimethylsilylmethyl complexes of the rare-earth metals with sterically hindered N-heterocyclic carbene ligands: adduct formation and C–H bond activation

Tris(trimethylsilylmethyl) complexes of yttrium and lutetium [LnR(3)(THF)(2)] (R = CH(2)SiMe(3)) were treated with sterically bulky N-heterocyclic carbenes (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) and 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes). IPr gave labile mono-adducts [LnR(3)(NHC)], isolated as thermally robust crystals and fully characterized by NMR spectroscopy and X-ray diffraction. IMes gave a similar lutetium mono-adduct [LuR(3)(IMes)] with the lutetium alkyl [LuR(3)(THF)(2)], whereas the yttrium alkyl [YR(3)(THF)(2)] resulted in the formation of an ortho-metalated product. This compound, isolated as a crystalline bis(THF) adduct, contains a strained six-membered chelate ring that has been formed by the C-H bond activation of one of the ortho-methyl groups of the mesityl group. In contrast [LuR(3)(IMes)] only slowly underwent a similar C-H bond activation.

Polymerization of 2,2′‐dimethyltrimethylene carbonate by lutetium complexes bearing amino‐phosphine ligands

AbstractA series of lutetium alkyl, amino, and guanidinato complexes based upon an amino‐phosphine ligand framework had been prepared. These complexes were applied to initiate ring‐opening polymerization of 2,2′‐dimethyltrimethylene carbonate (DTC). The type of the initiator significantly influenced the catalytic activity of these complexes in a trend as follows: alkyl ≈ guanidinate > amide, whereas the complexes with flexible backbone between P and N atoms within the ligand exhibited higher activity than those with rigid backbone. The isolated PDTC had bimodal‐mode molecular weight distribution. The molecular weights of each fraction increased linearly with the conversion, indicating that there might be two active species. This had been confirmed by analyses of oligomeric DTC living species and oligomer with NMR technique as the metal‐alkoxide and the four‐membered metallocyclic lactate. Kinetic investigation displayed that the polymerization rate was the first order with the monomer concentration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Lutetium Alkyls Supported by a Dearomatized and Functionalized Terpyridine Ligand: Preparation of Fluorinated Anilide Complexes

Lutetium alkyl complexes supported by a monoanionic, tridentate ligand system formed by the dearomatization and functionalization of a 2,2′:6′,2′′-terpyridine have been reacted with 2,4,6-triphenylaniline or the fluorinated anilines 4-F-C6H4NH2 and C6F5NH2 to give both terminal mono(amide) and bis(amide) lutetium(III) complexes, which have been fully characterized. Both [tBu3(2′-Me3SiCH2)tpy]Lu[NH(2,4,6-Ph3-C6H2)]2 (3) and [tBu3(2′-Me3SiCH2)tpy](C5Me5)Lu(NHC6F5) (7) have been structurally characterized. The fluorinated anilide complexes [tBu3(2′-Me3SiCH2)tpy](C5Me5)Lu(NHArF) (ArF = 4-F-C6H4 (6), C6F5 (7)) provide rare examples of lutetium organofluorine complexes, with 7 featuring an intramolecular F···H−C interaction that is present in both solid state and solution.

Lutetium alkyl and hydride complexes in a non-cyclopentadienyl coordination environment

Lutetium alkyl complexes [Lu(L)(CH(2)SiMe(3))(THF)(n)], which contain a sulfur-linked bis(phenolato) ligand such as 2,2'-thiobis(6-tert-butyl-4-methylphenolate) (L=tbmp, 1) or 1,4-dithiabutanediyl-bis(6-tert-butyl-4-methylphenolate) (L=etbmp, 2), were isolated from the reaction of the lutetium tris(alkyl) complex [Lu(CH(2)SiMe(3))(3)(THF)(2)] with H(2)L. The monomeric structures of these complexes were confirmed by X-ray diffraction studies, showing distorted octahedral geometry around the metal centre. The reaction of [Lu(tbmp)(CH(2)SiMe(3))(THF)(2)] (1) with alcohols ROH (R=iPr, CHPh(2), CPh(3)) results in the formation of the corresponding alkoxide complexes [Lu(tbmp)(OR)(THF)(n)] (4-6). With PhSiH(3) hydride complexes [Lu(L)(mu-H)(THF)(n)](2) (L=tbmp, 7; etbmp, 8) have been prepared in moderate to good yields. They adopt a dimeric form in the solid state as revealed by the X-ray crystal structure of 7. The reactivity of the hydride complexes and their catalytic activity in the ring-opening polymerisation of L-lactide and the hydrosilylation of alkenes are also discussed.

A Chiral-Bridged Aminotroponiminate Complex of Lutetium as Catalyst for the Asymmetric Hydroamination

The enantiomerically pure bridged aminotroponiminate S,S-H2{(iPrATI)2diph}, in which two amino-isopropyl-troponimine moieties are linked by 1,2-(S,S)-diamino-1,2-diphenylethane, has been prepared. The chiral lutetium alkyl complex of composition [(R,R)-{(iPrATI)2diphLuCH2SiMe3(THF)] (3) was obtained via two synthetic approaches. In the first approach the dipotassium salt [(S,S)-K2{(iPrATI)2diph}] (1) of the ligand was reacted via a salt metathesis with lutetium trichloride to give [(S,S)-{(iPrATI)2diph}LuCl(THF)] (2). Reaction of 2 with LiCH2SiMe3 resulted in 3. Compound 3 can also be obtained by the reaction of [Lu(CH2SiMe3)3(THF)2] with (S,S)-H2{(iPrATI)2diph} under elimination of Me4Si. The alkyl complex 3 was used as catalyst in the intramolecular hydroamination reaction of nonactivated terminal aminoolefins. Good catalytic activities and moderate enantioselectivties were observed.

“Constrained geometry” catalysts of the rare-earth metals for the hydrosilylation of olefins

A series of yttrium and lutetium alkyl complexes [Ln(η 5-C 5Me 4ZNR′-κN)(CH 2SiMe 3)(THF) n ] (Ln = Y, Lu) was prepared by reacting the tris(trimethylsilylmethyl) precursor [Ln(CH 2SiMe 3) 3(THF) 2] with different linked amino-cyclopentadienes of the type (C 5Me 4H)ZNHR′ (Z = SiMe 2, CH 2SiMe 2; R′ = tBu, Ph, C 6H 4- tBu-4, C 6H 4- nBu-4). The catalytic activity of these alkyl complexes in the hydrosilylation of 1-decene and styrene using PhSiH 3 as reagent was examined under standard conditions. A significant influence of the ligand structure on the catalytic property (turnover frequency, regioselectivity) was observed with the yttrium complex [Y(η 5-C 5Me 4CH 2SiMe 2N tBu-κN)(CH 2SiMe 3)(THF)] being the most active for 1-decene hydrosilylation.

Novel Z-selective head-to-head dimerization of terminal alkynes catalyzed by lanthanide half-metallocene complexes.

Various terminal alkynes have been cleanly dimerized into the corresponding head-to-head (Z)-enynes by use of the half-metallocene lutetium alkyl complexes Me2Si(C5Me4)(NAr)Lu(CH2SiMe3)(THF) (Ar = Ph, C6H3Me2-2,6, C6H2Me3-2,4,6) as catalysts. Aromatic C-Cl, C-Br, and C-I bonds, which are known to be extremely susceptible to reductive cleavage by transition metals, survived in the present reactions. The corresponding dimeric alkynide species [Me2Si(C5Me4)(NAr)Lu(mu-CCR)]2 are thought to be the true catalysts, some of which have been isolated and structurally characterized. These alkynide species were thermally stable and soluble at the reaction temperatures (80-110 degrees C), but they precipitated upon cooling to room temperature after completion of the reaction. Therefore, this catalyst system works homogeneously but can be separated and reused, thus constituting the first example of a recyclable catalyst system for the dimerization of terminal alkynes and also the first example of (Z)-selective head-to-head dimerization of aromatic terminal alkynes.

Metallorganische verbindungen der lanthanoide: LXX. Bis(cyclopentadienyl)seltenerdkomplexe: Synthese und röntgen-strukturanalyse von dem intramolekular stabilisierten lutetiumalkyl Cp 2[formula omitted]Me 2 und dem monomeren basenfreien yttriumcarboxylat Cp 2Y[η 2-O 2C(CH 2) 3NMe 2

Metathesis of LuCl 3, NaCp and Li(CH 2) 3NMe 2 in the molar ratio 1:2:1 affords the lutetium alkyl species Cp 2 Lu(CH 2) 3N Me 2 ( 1); analogous reaction of LuCl 3, NaMeC 5H 4 and LiCH 2CH(Me)-CH 2NMe 2 generates the corresponding complex (MeC 5H 4) 2 Lu[CH 2CH(Me)CH 2N Me 2] ( 2). Treatment of YCl 3 with two equivalents of NaCp and one equivalent of Li(CH) 3NMe 2 yields, in the presence of CO 2, the yttrium carboxylate Cp 2Y[η 2-O 2C(CH 2) 3NMe 2 ( 3). Mass spectrometrical studies of the solvent-free rare earth triflates [Cp 2Ln(OSO 2CF 3)] 2 (Ln = Sc ( 4), Lu ( 5)) have shown them to be dimeric. The crystal structures of 1 and 3 were determined by X-ray diffraction methods. 1 crystallizes in the monoclinic space group P2 1 (No. 4) with the unit-cell parameters a 657.0(4), b 1386.7(8), c 803.5(3) pm, β 106.64(5)°, V 704(1) × 10 −30 m 3 and Z = 2. The structure was solved on the basis of 1094 observed reflections with F 0 ≥ 3σ( F 0) and refined to a final R value of 0.0483. With the short LuN bond length of 237(1) pm the molecular structure of 1 exhibits an intramolecular N → Lu coordination. The crystals of 3 are triclinic, space group P 1 (No. 2), with a 1078.2(6), b 1533.0(9), c 1020.3(8) pm, α 109.47(6), β 82.75(6), γ 88.99(5)°, V 1574(2)×10 −30 m 3 and Z = 4. Least-squares refinement of the model based on 1659 observed reflections converged to R = 0.093 (F 0 ≥ 5σ( F 0)). The structural data of 3 feature a monomer with a chelating carboxylate group. The long YN distance (499 pm) excludes any intramolecular NY interactions.