Highly efficient hydrophosphonylation of aldehydes and unactivated ketones catalyzed by methylene-linked pyrrolyl rare earth metal amido complexes

A series of rare earth metal amido complexes bearing methylene-linked pyrrolyl-amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent-free conditions for liquid substrates. Treatment of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) with 2-(2,6-Me(2)C(6)H(3)NHCH(2))C(4)H(3)NH (1, 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ-η(5):η(1)):η(1)-2-[(2,6-Me(2)C(6)H(3))NCH(2)](C(4)H(3)N)LnN(SiMe(3))(2)}(2) [Ln=Y (2), Nd (3), Sm (4), Dy (5), Yb (6)] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by (1)H NMR spectroscopic analyses. The structures of complexes 2, 3, 4, and 6 were determined by single-crystal X-ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol%) afforded the products in high yields (up to 99%) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99% with employment of low loadings (0.1 to 0.5 mol%) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α-hydroxy diaryl phosphonates in moderate to high yields.     

Super‐Bulky Penta‐arylcyclopentadienyl Ligands: Isolation of the Full Range of Half‐Sandwich Heavy Alkaline‐Earth Metal Hydrides

Hydrogenolysis of the half‐sandwich penta‐arylcyclopentadienyl‐supported heavy alkaline‐earth‐metal alkyl complexes (Cp^Ar)Ae[CH(SiMe₃)₂](S) (Cp^Ar=C₅Ar₅, Ar=3,5‐ⁱPr₂‐C₆H_3; S=THF or DABCO) in hexane afforded the calcium, strontium, and barium metal–hydride complexes as the same dimers [(Cp^Ar)Ae(μ‐H)(S)]₂ (Ae=Ca, S=THF, 2‐Ca ; Ae=Sr, Ba, S=DABCO, 4‐Ae ), which were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. 2‐Ca , 4‐Sr , and 4‐Ba catalyzed alkene hydrogenation under mild conditions (30 °C, 6 atm, 5 mol % cat.), with the activity increasing with the metal size. A variety of activated alkenes including tri‐ and tetra‐substituted olefins, semi‐activated alkene (Me₃SiCH=CH₂), and unactivated terminal alkene (1‐hexene) were evaluated.     

Molecular Thorium Trihydrido Clusters Stabilized by Cyclopentadienyl Ligands

Hydrogenolysis of alkyl‐substituted cyclopentadienyl (Cp^R) ligated thorium tribenzyl complexes [(Cp^R)Th(p‐CH₂‐C₆H₄‐Me)₃] ( 1 – 6 ) afforded the first examples of molecular thorium trihydrido complexes [(Cp^R)Th(μ‐H)₃]_n (Cp^R=C₅H₂(^tBu)₃ or C₅H₂(SiMe₃)₃, n=5; C₅Me₄SiMe₃, n=6; C₅Me₅, n=7; C₅Me₄H, n=8; 7 – 10 and 12 ) and [(Cp^#)₁₂Th₁₃H₄₀] (Cp^#=C₅H₄SiMe₃; 13 ). The nuclearity of the metal hydride clusters depends on the steric profile of the cyclopentadienyl ligands. The hydrogenolysis intermediate, tetra‐nuclear octahydrido thorium dibenzylidene complex [(Cp^ttt)Th(μ‐H)₂]₄(μ‐p‐CH‐C₆H₄‐Me)₂ (Cp^ttt=C₅H₂(^tBu)₃) ( 11 ) was also isolated. All of the complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. Hydride positions in [(Cp^Me4)Th(μ‐H)₃]₈ (Cp^Me4=C₅Me₄H) were further precisely confirmed by single‐crystal neutron diffraction. DFT calculations strengthen the experimental assignment of the hydride positions in the complexes 7 to 12 .     

Reactions of Rare‐Earth Metal Based Lewis Pairs with Azides†

The reactivity of homoleptic rare‐earth metal aryloxide based Lewis pairs toward organic azide substrates has been investigated herein. Treatment of RE(OAr)₃ (RE = La, Sm, Y, and Sc, Ar = 2,6‐^tBu₂‐C₆H₃), PEt₃ and Me₃SiN₃ in 2 : 1 : 1 molar ratio resulted in formation of separated ion pair complexes [Me₃Si‐PEt₃]⁺[(ArO)₃RE‐N=N=N‐RE(OAr)₃]^– under mild conditions. Replacement of phosphine with the nitrogen‐containing Lewis base 1,4‐diazabicyclo[2.2.2]octane (DABCO) produced analogous rare‐earth azide complexes with [Me₃Si‐DABCO]⁺ counterions. In contrast, reaction of the La(OAr)₃/PEt₃ Lewis pair with 1‐adamantyl azide (AdN₃) afforded the typical frustrated Lewis pair‐type 1,1‐addition product. A tetrahydrofuran ring‐opening reaction was also observed for the resulting rare‐earth azide complex with the [Me₃Si‐PEt₃]⁺ cation, with cleavage of the C—O bond by Si/P cooperation.     

Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Y,Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis,Characterization, and Catalysis in the cis‐1,4‐Selective Polymerization of Isoprene

A series of NCO/NCS pincer precursors, 3‐(Ar²OCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCO^Ar2)Br, 3a , 3b , 3c , 3d ) and 3‐(2,6‐Me₂C₆H₃SCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCS^Me)Br, 4a and 4b ) were synthesized and characterized. The reactions of [^Ar1NCO^Ar2]Br/ [^Ar1NCS^Me]Br with nBuLi and the subsequent addition of the rare‐earth‐metal chlorides afforded their corresponding rare‐earth‐metal–pincer complexes, that is, [(^Ar1NCO^Ar2)YCl₂(thf)₂] ( 5a , 5b , 5c , 5d ), [(^Ar1NCO^Ar2)LuCl₂(thf)₂] ( 6a , 6d ), [(^Ar1NCO^Ar2)GdCl₂(thf)₂] ( 7 ), [{(^Ar1NCS^Me)Y(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 8 , 9 ), and [{(^Ar1NCS^Me)Gd(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 10 , 11 ). These diamagnetic complexes were characterized by ¹H and ¹³C NMR spectroscopy and the molecular structures of compounds 5a , 6a , 7 , and 10 were well‐established by X‐ray diffraction analysis. In compounds 5a , 6a , and 7 , all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two Cl? Li? Cl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis‐1,4‐selective polyisoprene, whilst the NCO? lutetium complexes were inert under the same conditions.     

Rare‐Earth‐Metal–Hydrocarbyl Complexes Bearing Linked Cyclopentadienyl or Fluorenyl Ligands: Synthesis,Catalyzed Styrene Polymerization,and Structure–Reactivity Relationship

A series of rare‐earth‐metal–hydrocarbyl complexes bearing N‐type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized. Treatment of [Y(CH₂SiMe₃)₃(thf)₂] with equimolar amount of the electron‐donating aminophenyl‐Cp ligand C₅Me₄H‐C₆H₄‐o‐NMe₂ afforded the corresponding binuclear monoalkyl complex [({C₅Me₄‐C₆H₄‐o‐NMe(μ‐CH₂)}Y{CH₂SiMe₃})₂] ( 1 a ) via alkyl abstraction and C? H activation of the NMe₂ group. The lutetium bis(allyl) complex [(C₅Me₄‐C₆H₄‐o‐NMe₂)Lu(η³‐C₃H₅)₂] ( 2 b ), which contained an electron‐donating aminophenyl‐Cp ligand, was isolated from the sequential metathesis reactions of LuCl₃ with (C₅Me₄‐C₆H₄‐o‐NMe₂)Li (1 equiv) and C₃H₅MgCl (2 equiv). Following a similar procedure, the yttrium‐ and scandium–bis(allyl) complexes, [(C₅Me₄‐C₅H₄N)Ln(η³‐C₃H₅)₂] (Ln=Y ( 3 a ), Sc ( 3 b )), which also contained electron‐withdrawing pyridyl‐Cp ligands, were also obtained selectively. Deprotonation of the bulky pyridyl‐Flu ligand (C₁₃H₉‐C₅H₄N) by [Ln(CH₂SiMe₃)₃(thf)₂] generated the rare‐earth‐metal–dialkyl complexes, [(η³‐C₁₃H₈‐C₅H₄N)Ln(CH₂SiMe₃)₂(thf)] (Ln=Y ( 4 a ), Sc ( 4 b ), Lu ( 4 c )), in which an unusual asymmetric η³‐allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium–trisalkyl complex [Y(CH₂C₆H₄‐o‐NMe₂)₃], the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η³‐C₁₃H₈‐C₅H₄N)Y(CH₂C₆H₄‐o‐NMe₂)₂] ( 5 ). Complexes 1 – 5 were fully characterized by ¹H and ¹³C NMR and X‐ray spectroscopy, and by elemental analysis. In the presence of both [Ph₃C][B(C₆F₅)₄] and AliBu₃, the electron‐donating aminophenyl‐Cp‐based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph₃C][B(C₆F₅)₄] only, the electron‐withdrawing pyridyl‐Cp‐based complexes 3 , in particular scandium complex 3 b , exhibited outstanding activitiy to give perfectly syndiotactic (rrrr >99 %) polystyrene, whereas their bulky pyridyl‐Flu analogues ( 4 and 5 ) in combination with [Ph₃C][B(C₆F₅)₄] and AliBu₃ displayed much‐lower activity to afford syndiotactic‐enriched polystyrene.     

2H‐Azirines as Ligands: Structural Characterization of the First Neutral and Cationic (η5‐C5Me5)Rh(III) 2H‐Azirine Complexes

The synthesis and structural characterization of two azirine rhodium(III ) complexes are described. The stabilization, N‐coordination and phenylgroup π‐stacking of the highly reactive and strained 3‐phenyl‐2H‐azirine by transition metal coordination is observed. The reaction of the dimeric complex [(η⁵‐C₅Me₅)RhCl₂]₂ with 3‐phenyl‐2H‐azirine (az) in CH₂Cl₂ at room temperature in a 1:2 molar ratio afforded the neutral mono‐azirine complex [(η⁵‐C₅Me₅)RhCl₂(az)]. The subsequent reaction of [(η⁵‐C₅Me₅)RhCl₂]₂ with six equivalents of az and 4 equivalents of AgOTf yielded the cationic tris‐azirine complex [(η⁵‐C₅Me₅)Rh(az)₃](OTf)₂. After purification, all complexes have been fully characterized. The molecular structures of the novel rhodium(III ) complexes exhibit slightly distorted octahedral coordination geometries around the metal atoms.     

Unique dual function of La(C5Me5)[CH(SiMe3)2]2(THF) for polymerizations of both nonpolar and polar monomers

A half‐metallocene‐type complex, La(C₅Me₅)[CH(SiMe₃)₂]₂tetrahydrofuran (THF) 1 , showed the dual function of performing the controlled polymerizations of nonpolar monomers such as ethylene and styrene as well as polar monomers like methyl methacrylate, hexyl isocyanate, and acrylonitrile in high yields. On the other hand, the metallocene‐type rare‐earth metal complexes, [(C₅H₄SiMe₃)₂Y(μ‐Me)]₂ 2 and (C₅Me₅)₂YMe(THF) 3 , showed relatively low catalytic activity. The structure of complex 2 was characterized by X‐ray analysis. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1382–1390, 2001     

Electrophilic Organobismuth Dication Catalyzes Carbonyl Hydrosilylation

Bismuth compounds are gaining importance as potential alternatives to transition-metal complexes and electron deficient lighter p-block compounds in homogeneous catalysis. Computational analysis on the two-coordinate [(Me₂NC₆H₄)Bi]²⁺ possessing three electrophilic sites is experimentally evidenced by the isolation of [{Me₂NC₆H₄}Bi{OP(NMe₂)₃}₃][B(3,5-C₆H₃Cl₂)₄]₂. These observations led us to generate dicationic organobismuth catalyst, [(Me₂NC₆H₄)Bi(L)₃]²⁺ (L=aldehyde/ketone), evidenced by NMR spectroscopy in solution and by single-crystal X-ray diffraction in the solid state. It efficiently catalyzes hydrosilylation of aldehydes and ketones resulting in silyl ethers as the only products in high yields. Our investigations support a carbonyl activation mechanism at the bismuth center followed by Si−H addition.     

Bis(β‐diketiminato) lanthanide amides: synthesis,structure and catalysis for the polymerization of l‐lactide and ε‐caprolactone

Treatment of the chlorides (L^2,6‐iPr2_Ph)₂LnCl (L^2,6‐iPr2_Ph = [(2,6‐ⁱPr₂C₆H₃)NC(Me)CHC(Me)N(C₆H₅)]^?) with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃) afforded the monoamides (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Y ( 1 ), Yb ( 2 )) in good yields. Anhydrous LnCl₃ reacted with 2 equiv. of NaL^2,6‐iPr2_Ph in THF, followed by treatment with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃), giving the analogues (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Sm ( 3 ), Nd ( 4 )). Two monoamido complexes stabilized by two L^2‐Me ligands, (L^2‐Me)₂LnNH(2,6‐ⁱPr₂C₆H₃) (L^2‐Me = [N(2‐MeC₆H₄)C(Me)]₂CH)^?; Ln = Y ( 5 ), Yb ( 6 )), were also synthesized by the latter route. Complexes 1 , 2 , 3 , 4 , 5 , 6 were fully characterized, including X‐ray crystal structure analyses. Complexes 1 , 2 , 3 , 4 , 5 , 6 are isostructural. The central metal in each complex is ligated by two β‐diketiminato ligands and one amido group in a distorted trigonal bipyramid. All the complexes were found to be highly active in the ring‐opening polymerization of L‐lactide (L‐LA) and ε‐caprolactone (ε‐CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Yb < Y < Sm ≈ Nd and L^2‐Me < L^2,6‐iPr2_Ph). Remarkably, the binary 3/benzyl alcohol (BnOH) system exhibited a striking ‘immortal’ nature and proved able to quantitatively convert 5000 equiv. of L‐LA with up to 100 equiv. of BnOH per metal initiator. All the resulting PLAs showed monomodal, narrow distributions (M_w/M_n = 1.06 ? 1.08), with molar mass (M_n) decreasing proportionally with an increasing amount of BnOH. The binary 4/BnOH system also exhibited an ‘immortal’ nature in the polymerization of ε‐CL in toluene. Copyright © 2014 John Wiley & Sons, Ltd.     

Bimetallic Rare Earth Alkyl Complexes Bearing Bridged Amidinate Ligands: Synthesis and Activity for L-Lactide Polymerization

Four novel bridged‐amidines H₂L {1,4‐R¹[C(=NR²)(NHR²)]₂ [R¹=C₆H₄, R²=2,6‐ⁱPr₂C₆H₃ (H₂L¹); R¹=C₆H₄, R²=2,6‐Me₂C₆H₃ (H₂L²); R¹=C₆H₁₀, R²=2,6‐ⁱPr₂C₆H₃ (H₂L³); R¹=C₆H₁₀, R²=2,6‐Me₂C₆H₃ (H₂L⁴)]} were synthesized in 65%–78% isolated yields by the condensation reaction of dicarboxylic acid with four equimolar amounts of amines in the presence of PPSE at 180°C. Alkane elimination reaction of Ln(CH₂SiMe₃)₃(THF)₂ (Ln=Y, Lu) with 0.5 equiv. of amidine in THF at room temperature afforded the corresponding bimetallic rare earth alkyl complexes (THF)(Me₃SiCH₂)₂LnL¹Ln(CH₂SiMe₃)₂(THF) [Ln=Y ( 1 ), Lu ( 2 )], (THF)(Me₃SiCH₂)₂LnL²Ln‐ (CH₂SiMe₃)₂(THF) [Ln=Y ( 3 ), Lu ( 4 )], (THF)(Me₃SiCH₂)₂YL³Y(CH₂SiMe₃)₂(THF) ( 5 ), (THF)(Me₃SiCH₂)₂YL⁴‐ Y(CH₂SiMe₃)₂(THF) ( 6 ) in 72% –80% isolated yields. These neutral complexes showed activity towards L‐lactide polymerization in toluene at 70°C to give high molecular weight (M>10⁴) and narrow molecular weight distribution (M_w/M_n≦1.40) polymers     

Synthesis and Crystal Structure of Rare Earth Metal Chlorides Bearing Bridged-Indenyl Ancillary Ligand

Two new rare earth metal chloride complexes supported by a bridged‐indenyl ancillary ligand, [C₉H₆SiMe₂‐ (CH₂)₂SiMe₂C₉H₆]Ln(µ‐Cl)₂Li(TMEDA) [Ln=Y ( 1 ), Lu ( 2 )], were synthesized via salt metathesis reaction. Reaction of C₉H₇SiMe₂(CH₂)₂SiMe₂C₉H₇ with 2 equiv. of n‐butyllithium in hexane at room temperature afforded [C₉H₆SiMe₂‐ (CH₂)₂SiMe₂C₉H₆]Li₂ as white powder in 95% isolated yield. Further treatment of [C₉H₆SiMe₂(CH₂)₂SiMe₂‐ C₉H₆]Li₂ with anhydrous LnCl₃ in 1:1 molar ratio in THF/TMEDA at room temperature provided the bridged‐indenyl rare earth metal chlorides 1 and 2 in 86%–89% isolated yields. Both complexes were characterized by FT‐IR spectroscopy, NMR spectroscopy, elemental analysis, and X‐ray single crystal structure analysis. The central metals in both complexes are eight‐coordinated by two indenyl ligands in η⁵‐fashion, and two chlorine atoms to adopt a distorted tetrahedral geometry.     

Dehydrogenation of Amine?Borane Me2NH⋅BH3 Catalyzed by a Lanthanum?Hydride Complex

The rare‐earth‐metal? hydride complexes [{(1,7‐Me₂TACD)LnH}₄] (Ln=La 1 a , Y 1 b ; (1,7‐Me₂TACD)H₂=1,7‐dimethyl‐1,4,7,10‐tetraazacyclododecane, 1,7‐Me₂[12]aneN₄) were synthesized by hydrogenolysis of [{(1,7‐Me₂TACD)Ln(η³‐C₃H₅)}₂] with 1 bar H₂. The tetrameric structures were confirmed by ¹H NMR spectroscopy and single‐crystal X‐ray diffraction of compound 1 a . Both complexes catalyze the dehydrogenation of secondary amine? borane Me₂NH ? BH₃ to afford the cyclic dimer (Me₂NBH₂)₂ and (Me₂N)₂BH under mild conditions. Whilst the complete conversion of Me₂NH ? BH₃ was observed within 2 h with lanthanum? hydride 1 a , the yttrium homologue 1 b required 48 h to reach 95 % conversion. Further reactions of compound 1 a with Me₂NH ? BH₃ in various stoichiometric ratios gave a series of intermediate products, [{(1,7‐Me₂TACD)LaH}₄](Me₂NBH₂)₂ ( 2 a ), [(1,7‐Me₂TACDH)La(Me₂NBH₃)₂] ( 3 a ), [(1,7‐Me₂TACD)(Me₂NBH₂)La(Me₂NBH₃)] ( 4 a ), and [(1,7‐Me₂TACD)(Me₂NBH₂)₂La(Me₂NBH₃)] ( 5 a ). Complexes 2 a , 3 a , and 5 a were isolated and characterized by multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction studies. These intermediates revealed the activation and coordination modes of “Me₂NH ? BH₃” fragments that were trapped within the coordination sphere of a rare‐earth‐metal center.     

Synthesis,structure, and catalytic activity of rare-earth metal amides with a neutral pyrrolyl-functionalized indolyl ligand

<正>1 Representation of complexes and selected bond distances and bond angles Figure S1 Structure of complex 4. Hydrogen atoms were omitted for clarity, ellipsoids set at the 30% probability level. Selected bond distances() and angles(°): Er(1)–Cl(1) 2.6180(18), Er(1)–N(1) 2.301(6), Er(1)–N(4) 2.232(6), Er(1)–N(5) 2.229(6), N(1)–Er(1)–Cl(1) 87.41(14), N(4)–Er(1)–Cl(1) 101.16(14), N(5)–Er(1)–Cl(1) 118.60(16), N(4)–Er(1)–N(1) 114.1(2), N(5)–Er(1)–N(1) 108.7(2), N(5)–Er(1)–N(4) 121.9(2).Figure S2 Structure of complex 5. Hydrogen atoms were omitted for clarity, ellipsoids set at the 30% probability level. Selected bond distances(o) and angles(°): Y(1)–Cl(1) 2.6212(12), Y(1)–N(1) 2.280(3), Y(1)–N(4) 2.214(3), Y(1)–N(5) 2.228(3), N(1)–Y(1)–Cl(1) 87.67(8), N(4)–Y(1)–Cl(1) 121.32(8), N(5)–Y(1)–Cl(1) 102.88(8), N(4)–Y(1)–N(1) 107.75(11), N(5)–Y(1)–N(1) 111.64(11), N(4)–Y(1)–N(5) 120.78(10).     

Rare‐Earth‐Metal Alkylaluminates Supported by N‐Donor‐Functionalized Cyclopentadienyl Ligands: C?H Bond Activation and Performance in Isoprene Polymerization

Homoleptic tetramethylaluminate complexes [Ln(AlMe₄)₃] (Ln=La, Nd, Y) reacted with HCp^NMe2 (Cp^NMe2=1‐[2‐(N,N‐dimethylamino)‐ethyl]‐2,3,4,5‐tetramethyl‐cyclopentadienyl) in pentane at ?35 °C to yield half‐sandwich rare‐earth‐metal complexes, [{C₅Me₄CH₂CH₂NMe₂(AlMe₃)}Ln(AlMe₄)₂]. Removal of the N‐donor‐coordinated trimethylaluminum group through donor displacement by using an equimolar amount of Et₂O at ambient temperature only generated the methylene‐bridged complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] with the larger rare‐earth‐metal ions lanthanum and neodymium. X‐ray diffraction analysis revealed the formation of isostructural complexes and the C? H bond activation of one aminomethyl group. The formation of Ln(μ‐CH₂)Al moieties was further corroborated by ¹³C and ¹H‐¹³C HSQC NMR spectroscopy. In the case of the largest metal center, lanthanum, this C? H bond activation could be suppressed at ?35 °C, thereby leading to the isolation of [(Cp^NMe2)La(AlMe₄)₂], which contains an intramolecularly coordinated amino group. The protonolysis reaction of [Ln(AlMe₄)₃] (Ln=La, Nd) with the anilinyl‐substituted cyclopentadiene HCp^AMe2 (Cp^AMe2=1‐[1‐(N,N‐dimethylanilinyl)]‐2,3,4,5‐tetramethylcyclopentadienyl) at ?35 °C generated the half‐sandwich complexes [(Cp^AMe2)Ln(AlMe₄)₂]. Heating these complexes at 75 °C resulted in the C? H bond activation of one of the anilinium methyl groups and the formation of [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] through the elimination of methane. In contrast, the smaller yttrium metal center already gave the aminomethyl‐activated complex at ?35 °C, which is isostructural to those of lanthanum and neodymium. The performance of complexes [{C₅Me₄CH₂CH₂NMe(μ‐CH₂)AlMe₃}‐ Ln(AlMe₄)], [(Cp^AMe2)Ln(AlMe₄)₂], and [{C₅Me₄C₆H₄NMe(μ‐CH₂)AlMe₃}Ln(AlMe₄)] in the polymerization of isoprene was investigated upon activation with [Ph₃C][B(C₆F₅)₄], [PhNMe₂H][B(C₆F₅)₄], and B(C₆F₅)₃. The highest stereoselectivities were observed with the lanthanum‐based pre‐catalysts, thereby producing polyisoprene with trans‐1,4 contents of up to 95.6 %. Narrow molecular‐weight distributions (M_w/M_n<1.1) and complete consumption of the monomer suggested a living‐polymerization mechanism.     

Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐cis‐Polymerization

Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η²:η¹:η¹ hapticities are synthesized and characterized. Treatment of [RE(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of 3‐(tBuN?CH)C₈H₅NH ( L₁ ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH(CH₂SiMe₃)}Ind)RE(thf)(CH₂SiMe₃)]₂ (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L₁ is deprotonated by the metal alkyl species and the imino C?N group is transferred to the amido group by alkyl CH₂SiMe₃ insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ‐η²:η¹:η¹ bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L₁ is reduced to 3‐(tBuNHCH₂)C₈H₅NH ( L₂ ), the reaction of [Yb(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of L₂ in THF, interestingly, generated the trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (major) and cis‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐cis‐polymerization.     

Synthesis of homo- and heterodinuclear metal complexes with dimethylsilylene bridged unsymmetrical bis(cyclopentadienyl) ligand

The reaction of the dilithium salt Li₂[Me₂Si(C₅H₄)(C₅Me₄)] (2) of Me₂Si(C₅H₅)(C₅HMe₄) (1) with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) and [RhCl(CO)₂]₂ afforded homodinuclear metal complexes [{Me₂Si(η⁵-C₅H₄)(η⁵-C₅Me₄)}{M(C₈H₁₂)}₂] (M=Rh: 3; M=Ir: 4) and [{Me₂Si(η⁵-C₅H₄)(η⁵-C₅Me₄)}Rh₂(CO)₂(μ-CO)] (5), respectively. The reaction of 2 with RhCl(CO)(PPh₃)₂ afforded a mononuclear metal complex [{Me₂Si(C₅HMe₄)(η⁵-C₅H₄)}Rh(CO)PPh₃] (6) leaving the C₅HMe₄ moiety intact. Taking advantage of the difference in reactivity of the two cyclopentadienyl moieties of 2, heterodinuclear complexes were prepared in one pot. Thus, the reaction of 2 with RhCl(CO)(PPh₃)₂, followed by the treatment with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) afforded a homodinuclear metal complex [Rh(CO)PPh₃{(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Rh(C₈H₁₂)] (7) consisting of two rhodium centers with different ligands and a heterodinuclear metal complex [Rh(CO)(PPh₃){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Ir(C₈H₁₂)] (8). The successive treatment of 2 with [IrCl(C₈H₁₂)]₂ and [RhCl(C₈H₁₂)]₂ provided heterodinuclear metal complex [Ir(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Rh(C₈H₁₂)] (9). The reaction of 2 with CoCl(PPh₃)₃ and then with PhCCPh gave a mononuclear cobaltacyclopentadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(CPhCPhCPhCPh)(PPh₃)] (10). However, successive treatment of 2 with CoCl(PPh₃)₃, PhCCPh and [MCl(C₈H₁₂)]₂ in this order afforded heterodinuclear metal complexes [M(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Co(η⁴-C₄Ph₄)] (M=Rh: 11; M=Ir: 12) in which the cobalt center was connected to the C₅Me₄ moiety. Although the heating of 10 afforded a tetraphenylcyclobutadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(η⁴-C₄Ph₄)] (13), in which the cobalt center was connected to the C₅H₄ moiety, simple heating of the reaction mixture of 2, CoCl(PPh₃)₃ and PhCCPh resulted in the formation of a tetraphenylcyclobutadiene complex [{Me₂Si(C₅H₅)(η⁵-C₅Me₄)}Co(η⁴-C₄Ph₄)] (14), in which the cobalt center was connected to the C₅Me₄ moiety. The mechanism of the cobalt transfer was suggested based on the electrophilicity of the formal trivalent cobaltacyclopentadiene moiety. In the presence of 1,5-cyclooctadiene, the reaction of 2 with CoCl(PPh₃)₃ provided a mononuclear cobalt cyclooctadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(C₈H₁₂)] (15). The reaction of 15 with n-BuLi followed by the treatment with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) afforded the heterodinuclear metal complexes of [Co(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}M(C₈H₁₂)] (M=Rh: 16; M=Ir: 17). Treatment of 6 with Fe₂(CO)₉ at room temperature afforded a heterodinuclear metal complex [{Me₂Si(C₅HMe₄)(η⁵-C₅H₄)}{Rh(PPh₃)(μ-CO)₂Fe(CO)₃}] (18) in which the C₅HMe₄ moiety was kept intact. Treatment of dinuclear metal complex 5 with Fe₂(CO)₉ afforded a heterotrinuclear metal complex [{(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}{Rh(CO)Rh(μ-CO)₂Fe(CO)₃}] (19) having a triangular metal framework. The crystal and molecular structures of 3, 11, 12, 18 and 19 have been determined by single-crystal X-ray diffraction analysis.     

Synthesis of Guanidines from Amines and Carbodiimides Catalyzed by Mono‐Indenyl‐Ligated Rare Earth Metal Bis(silylamide) Complexes

Nucleophilic addition of primary aromatic amines to carbodiimides in the presence of catalytic amount of the mono‐indenyl‐ligated rare earth metal bis(silylamide) complexes (C₉H₆CMe₂CH₂C₅H₄N‐α)Ln[N(SiHMe₂)₂]₂ at room temperature afforded efficiently a series of guanidines with a wide spectrum of substituents on the nitrogen atoms.     

Molecular Nitrides with Titanium and Group 13–15 Elements

Several heterometallic nitrido complexes were prepared by reaction of the imido–nitrido titanium complex [{Ti(η⁵‐C₅Me₅)(μ‐NH)}₃(μ₃‐N)] ( 1 ) with amido derivatives of Group 13–15 elements. Treatment of 1 with bis(trimethylsilyl)amido [M{N(SiMe₃)₂}₃] derivatives of aluminum, gallium, or indium in toluene at 150–190 °C affords the single‐cube amidoaluminum complex [{(Me₃Si)₂N}Al{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] ( 2 ) or the corner‐shared double‐cube compounds [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Ga ( 3 ), In ( 4 )]. Complexes 3 and 4 were also obtained by treatment of 1 with the trialkyl derivatives [M(CH₂SiMe₃)₃] (M=Ga, In) at high temperatures. The analogous reaction of 1 with [{Ga(NMe₂)₃}₂] at 110 °C leads to [{Ga(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 5 ), in which two [GaTi₃N₄] cube‐type moieties are linked through a gallium–gallium bond. Complex 1 reacts with one equivalent of germanium, tin, or lead bis(trimethylsilyl)amido derivatives [M{N(SiMe₃)₂}₂] in toluene at room temperature to give cube‐type complexes [M{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [M=Ge ( 6 ), Sn ( 7 ), Pb ( 8 )]. Monitoring the reaction of 1 with [Sn{N(SiMe₃)₂}₂] and [Sn(C₅H₅)₂] by NMR spectroscopy allows the identification of intermediates [RSn{(μ₃‐N)(μ₃‐NH)₂Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [R=N(SiMe₃)₂ ( 9 ), C₅H₅ ( 10 )] in the formation of 7 . Addition of one equivalent of the metalloligand 1 to a solution of lead derivative 8 or the treatment of 1 with a half equivalent of [Pb{N(SiMe₃)₂}₂] afford the corner‐shared double‐cube compound [Pb(μ₃‐N)₂(μ₃‐NH)₄{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 11 ). Analogous antimony and bismuth derivatives [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Sb ( 12 ), Bi ( 13 )] were obtained through the reaction of 1 with the tris(dimethylamido) reagents [M(NMe₂)₃]. Treatment of 1 with [AlCl₂{N(SiMe₃)₂}(OEt₂)] affords the precipitation of the singular aluminum–titanium square‐pyramidal aggregate [{{(Me₃Si)₂N}Cl₃Al₂}(μ₃‐N)(μ₃‐NH)₂{Ti₃(η⁵‐C₅Me₅)₃(μ‐Cl)(μ₃‐N)}] ( 14 ). The X‐ray crystal structures of 5 , 11 , 13 , 14 , and [AlCl{N(SiMe₃)₂}₂] were determined.