Tetra-, Penta-, and Hexanuclear Yttrium Hydride Clusters from Half-Sandwich Bis(aminobenzyl) Complexes Containing Various Cyclopentadienyl Ligands

The novel series of half-sandwich tetrahydrofuran (THF)-free yttrium bis(aminobenzyl) complexes [(C5Me4R)Y(CH2C6H4NMe2-o)2] (R = SiMe3 (1a), Me (1b), Et (1c), H (1d)) was prepared by treatment of [Y(CH2C6H4NMe2-o)3] with C5Me4RH, and their reactions with H2 and with PhSiH3 in aromatic solvents or in THF were examined. The reaction of 1a with H2 in benzene gave the pentanuclear yttrium decahydride complex [{Cp′Y(μ-H)2}5] (Cp′ = η5-C5Me4SiMe3) (3), which could not be obtained by the reaction of the corresponding THF-coordinated dialkyl complex [Cp′Y(CH2SiMe3)2(THF)] with H2. The reaction of 1b with H2 in toluene gave the partially hydrogenated tetranuclear mixed aminobenzyl/hydride complex [(Cp*Y)2(CH2C6H4NMe2-o)(μ-H)3]2 (4; Cp* = η5-C5Me5), and no further hydrogenation reaction occurred, whereas the corresponding reaction of 1b with H2 in THF gave the pentanuclear yttrium polyhydride complex [{Cp*Y(μ-H)2}5(THF)2] (5). Hydrogenolysis of the sterically less demanding C5Me4H-ligated complex 1d with H2 in THF gave the tetranuclear octahydride complex [{CpHY(μ-H)2}4(THF)4] (6; CpH = η5-C5Me4H), which has one coordinating THF ligand on each metal atom. The hexanuclear yttrium dodecahydride complex {[Cp*Y(μ-H)2]6} (7) was obtained by treatment of 1b with PhSiH3 in benzene. The structures of 1a,b,d, 3, 4, [{(C5Me4Et)Y(μ-H)2}5(THF)2] (5′), 6, and 7 were determined by X-ray single-crystal diffraction studies

Isolation and Structural Characterization of a Polyhydrido Lanthanide Cluster Complex Consisting of “(C₅Me₄SiMe₃)LuH₂” Units

Reaction of the mixed alkyl/hydride complex [Cp‘Lu(CH2SiMe3)(μ-H)(THF)]2 (2; Cp‘ = C3Me4SiMe3) with 1 equiv of PhSiH3 (per Lu) in benzene or OEt2 afforded the polyhydrido cluster [Cp‘LuH2]4 (3), while hydrogenolysis of 2 with H2 (1 atm) in THF yielded the THF-coordinated complex [Cp‘Lu(μ-H)2]4(THF) (4). Complexes 3 and 4 are interconvertible, without decomposition or ligand redistribution

A Novel Binuclear Samarium(II) Complex Bearing Mixed Cyclopentadienide/Siloxide Ligands: [(C₅Me₅)Sm{<i>μ</i>-OSi(O<i>^t</i>Bu)₃}₃Sm]. Synthesis, Structure, Electron-Transfer, and Unusual Metal-Coordination Reactions

The reaction of (C5Me5)2Sm(thf)2 with 1.5 equiv of (tBuO)3SiOH in toluene gave the unsymmetrical binuclear Sm(II) complex [(C5Me5)Sm{μ-OSi(OtBu)3}3Sm] (1) in 93% isolated yield. The use of 1 equiv of (tBuO)3SiOH in this reaction also afforded 1 albeit in low yield. Addition of 4 equiv of hexamethylphosphoric triamide (hmpa) to a toluene solution of 1 gave (C5Me5)Sm{OSi(OtBu)3}(hmpa)2 (2) as the only isolable product. The reaction of 1 with 1 equiv of azobenzene in toluene gave the corresponding binuclear Sm(III) azobenzene-dianion complex [(C5Me5)Sm{μ-OSi(OtBu)3}2(μ,η1:η2-N2Ph2)SmOSi(OtBu)3] (3) in 64% isolated yield. When 1 was treated with ArOH (Ar = C6H2tBu2-2,6-Me-4) or phenylacetylene in toluene, a novel trinuclear Sm(II)/Sm(III) mixed valence “inverse sandwich” complex, [{(tBuO)3SiO}3SmIII(μ,η5:η5-C5Me5)SmII{μ-OSi(OtBu)3}3SmII] (4), was isolated (ca. 20%). Complex 4 could alternatively be obtained in high yields (80−85%) by reaction of 1 with 1 equiv of the Sm(III) tris(siloxide) complex Sm{OSi(OtBu)3}3(thf)2 (5) or [Sm{μ-OSi(OtBu)3}{OSi(OtBu)3}2]2 (8), through coordination of the C5Me5 unit to the Sm(III) center. Similarly, the reactions of 1 with Gd{OSi(OtBu)3}3(thf)2 (6) and Sm(OSiPh3)3(thf)3·(thf) (7) yielded the corresponding Sm(II)/Gd(III) heterometallic complex [{(tBuO)3SiO}3GdIII(μ,η5:η5-C5Me5)SmII{μ-OSi(OtBu)3}3SmII] (9) (88%) and the Sm(II)/Sm(III) mixed valence complex [{Ph3SiO}3SmIII (μ,η5:η5-C5Me5)SmII{μ-OSi(OtBu)3}3SmII] (10) (78%), respectively. The reaction of 1 with the Sm(II) silylamido complex Sm{N(SiMe3)2}2(thf)2 in toluene yielded a linear pentanuclear Sm(II) ion-pair complex, [SmII{μ-OSi(OtBu)3}3SmII(μ,η5:η5-C5Me5)SmII{μ-OSi(OtBu)3}3SmII][SmII{N(SiMe3)2}3] (11). Complexes 1, 3, 4, and 8−11 have all been structurally characterized by X-ray crystallographic studies

Tetra-, Penta-, and Hexanuclear Yttrium Hydride Clusters from Half-Sandwich Bis(aminobenzyl) Complexes Containing Various Cyclopentadienyl Ligands

The novel series of half-sandwich tetrahydrofuran (THF)-free yttrium bis(aminobenzyl) complexes [(C5Me4R)Y(CH2C6H4NMe2-o)2] (R = SiMe3 (1a), Me (1b), Et (1c), H (1d)) was prepared by treatment of [Y(CH2C6H4NMe2-o)3] with C5Me4RH, and their reactions with H2 and with PhSiH3 in aromatic solvents or in THF were examined. The reaction of 1a with H2 in benzene gave the pentanuclear yttrium decahydride complex [{Cp′Y(μ-H)2}5] (Cp′ = η5-C5Me4SiMe3) (3), which could not be obtained by the reaction of the corresponding THF-coordinated dialkyl complex [Cp′Y(CH2SiMe3)2(THF)] with H2. The reaction of 1b with H2 in toluene gave the partially hydrogenated tetranuclear mixed aminobenzyl/hydride complex [(Cp*Y)2(CH2C6H4NMe2-o)(μ-H)3]2 (4; Cp* = η5-C5Me5), and no further hydrogenation reaction occurred, whereas the corresponding reaction of 1b with H2 in THF gave the pentanuclear yttrium polyhydride complex [{Cp*Y(μ-H)2}5(THF)2] (5). Hydrogenolysis of the sterically less demanding C5Me4H-ligated complex 1d with H2 in THF gave the tetranuclear octahydride complex [{CpHY(μ-H)2}4(THF)4] (6; CpH = η5-C5Me4H), which has one coordinating THF ligand on each metal atom. The hexanuclear yttrium dodecahydride complex {[Cp*Y(μ-H)2]6} (7) was obtained by treatment of 1b with PhSiH3 in benzene. The structures of 1a,b,d, 3, 4, [{(C5Me4Et)Y(μ-H)2}5(THF)2] (5′), 6, and 7 were determined by X-ray single-crystal diffraction studies

Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide Catalyzed by Organo Rare Earth Metal Complexes

The mono(cyclopentadienyl)-ligated rare earth metal bis(alkyl) complexes (C5Me4SiMe3)Ln(CH2SiMe3)2(THF) (Ln = Y (1a), Dy (1b), Lu (1c), Sc (1d)) and polyhydride complexes [(C5Me4SiMe3)Ln(μ-H)2]4(THF)x (2a:  Ln = Y, x = 1; 2b:  Ln = Dy, x = 2; 2c:  Ln = Lu, x = 1) are active as single-component catalysts, not only for the ring-opening homopolymerization of cyclohexene oxide (CHO), but also for the alternating copolymerization of CHO and CO2. The homopolymerization of CHO in bulk took place much more rapidly than that in solution and afforded in high yields the corresponding polyether with Mn = (50−80) × 103 and Mw/Mn ≅ 2 in most cases. The copolymerization of CHO and CO2 by 1a−c and 2a−c at 70−110 °C under 12 atm of CO2 yielded the corresponding polycarbonate with Mn = (14−40) × 103, Mw/Mn = 4−6, and carbonate linkages = 90−99% with TOF ranging from 1000 to 2000 g polymer/(mol-Ln h). In contrast, the Sc alkyl complex 1d gave a polymer containing high ether linkages (carbonate linkages = 23%) under the similar conditions because of its higher activity for CHO homopolymerization. The stoichiometric reaction of the bis(alkyl) complexes 1a, c, and d with CO2 afforded quantitatively the corresponding bis(carboxylate) complexes [(C5Me4SiMe3)Ln(μ-η:η1-O2CCH2SiMe3)2]2 (Ln = Y (3a), Lu (3b), Sc (3c)), which adopt a dimeric structure through the carboxylate bridges. The isolated carboxylate complexes 3a, b also showed moderate activity for the alternating copolymerization of CHO and CO2, which thus constituted a rare example of a well-defined, catalytically active carboxylate intermediate that was isolated directly from the reaction of a true catalyst system

Tetra-, Penta-, and Hexanuclear Yttrium Hydride Clusters from Half-Sandwich Bis(aminobenzyl) Complexes Containing Various Cyclopentadienyl Ligands

The novel series of half-sandwich tetrahydrofuran (THF)-free yttrium bis(aminobenzyl) complexes [(C5Me4R)Y(CH2C6H4NMe2-o)2] (R = SiMe3 (1a), Me (1b), Et (1c), H (1d)) was prepared by treatment of [Y(CH2C6H4NMe2-o)3] with C5Me4RH, and their reactions with H2 and with PhSiH3 in aromatic solvents or in THF were examined. The reaction of 1a with H2 in benzene gave the pentanuclear yttrium decahydride complex [{Cp′Y(μ-H)2}5] (Cp′ = η5-C5Me4SiMe3) (3), which could not be obtained by the reaction of the corresponding THF-coordinated dialkyl complex [Cp′Y(CH2SiMe3)2(THF)] with H2. The reaction of 1b with H2 in toluene gave the partially hydrogenated tetranuclear mixed aminobenzyl/hydride complex [(Cp*Y)2(CH2C6H4NMe2-o)(μ-H)3]2 (4; Cp* = η5-C5Me5), and no further hydrogenation reaction occurred, whereas the corresponding reaction of 1b with H2 in THF gave the pentanuclear yttrium polyhydride complex [{Cp*Y(μ-H)2}5(THF)2] (5). Hydrogenolysis of the sterically less demanding C5Me4H-ligated complex 1d with H2 in THF gave the tetranuclear octahydride complex [{CpHY(μ-H)2}4(THF)4] (6; CpH = η5-C5Me4H), which has one coordinating THF ligand on each metal atom. The hexanuclear yttrium dodecahydride complex {[Cp*Y(μ-H)2]6} (7) was obtained by treatment of 1b with PhSiH3 in benzene. The structures of 1a,b,d, 3, 4, [{(C5Me4Et)Y(μ-H)2}5(THF)2] (5′), 6, and 7 were determined by X-ray single-crystal diffraction studies

C–H Polyaddition of Dimethoxyarenes to Unconjugated Dienes by Rare Earth Catalysts

The C–H polyaddition of dimethoxyarenes such as 1,4-dimethoxybenzene and 4,4′-dimethoxybiphenyl to unconjugated dienes such as norbornadiene and 1,4-divinylbenzene has been achieved for the first time by using cationic half-sandwich rare earth alkyl catalysts. This protocol afforded novel polymer materials consisting of dimethoxyarene moieties and nonpolar hydrocarbon structure motifs (cyclic, linear, and aromatic) in perfectly alternating sequences that are otherwise difficult to make. The reaction proceeded via CC double bond insertion into a C–H bond ortho to each of the two methoxy groups in a step-growth polymerization fashion

Catalytic Addition of Terminal Alkynes to Carbodiimides by Half-Sandwich Rare Earth Metal Complexes

The catalytic addition of terminal alkynes to carbodiimides has been achieved for the first time by use of half-sandwich rare earth metal complexes, such as {Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2, which offers a straightforward, atom-economic route to the N,N‘-disubstituted propiolamidines which contain a conjugated C−C triple bond, a new family of amidines which were difficult to prepare by other means. A rare earth metal amidinate species was confirmed to be a true catalytic species in this process, thus demonstrating for the first time that an amidinate unit, though being often used as an ancillary ligand for various organometallic complexes, can itself participate in a catalytic reaction under appropriate conditions

Catalytic Addition of Terminal Alkynes to Carbodiimides by Half-Sandwich Rare Earth Metal Complexes

The catalytic addition of terminal alkynes to carbodiimides has been achieved for the first time by use of half-sandwich rare earth metal complexes, such as {Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2, which offers a straightforward, atom-economic route to the N,N‘-disubstituted propiolamidines which contain a conjugated C−C triple bond, a new family of amidines which were difficult to prepare by other means. A rare earth metal amidinate species was confirmed to be a true catalytic species in this process, thus demonstrating for the first time that an amidinate unit, though being often used as an ancillary ligand for various organometallic complexes, can itself participate in a catalytic reaction under appropriate conditions

Catalytic Addition of Terminal Alkynes to Carbodiimides by Half-Sandwich Rare Earth Metal Complexes

The catalytic addition of terminal alkynes to carbodiimides has been achieved for the first time by use of half-sandwich rare earth metal complexes, such as {Me2Si(C5Me4)(NPh)}Y(CH2SiMe3)(THF)2, which offers a straightforward, atom-economic route to the N,N‘-disubstituted propiolamidines which contain a conjugated C−C triple bond, a new family of amidines which were difficult to prepare by other means. A rare earth metal amidinate species was confirmed to be a true catalytic species in this process, thus demonstrating for the first time that an amidinate unit, though being often used as an ancillary ligand for various organometallic complexes, can itself participate in a catalytic reaction under appropriate conditions