9003-09-2Relevant articles and documents
Phosphine-Catalyzed Vinylation at Low Acetylene Pressure
Bienewald, Frank,Comba, Peter,Hashmi, A. Stephen K.,Menche, Maximilian,Rominger, Frank,Schafer, Ansgar,Schaub, Thomas,Sitte, Nikolai A.,Tuzina, Pavel
, p. 13041 - 13055 (2021/09/18)
The vinylation of various nucleophiles with acetylene at a maximum pressure of 1.5 bar is achieved by organocatalysis with easily accessible phosphines like tri-n-butylphosphine. A detailed mechanistic investigation by quantum-chemical and experimental methods supports a nucleophilic activation of acetylene by the phosphine catalyst. At 140 °C and typically 5 mol % catalyst loading, cyclic amides, oxazolidinones, ureas, unsaturated cyclic amines, and alcohols were successfully vinylated. Furthermore, the in situ generation of a vinyl phosphonium species can also be utilized in Wittig-type functionalization of aldehydes.
Thermally Stable Half-Sandwich Benzhydryl Ln(II) (Ln = Sm, Yb) Complexes Supported by Sterically Demanding Carbazolyl and Fluorenyl Ligands
Selikhov, Alexander N.,Shavyrin, Andrey S.,Cherkasov, Anton V.,Fukin, Georgy K.,Trifonov, Alexander A.
, p. 4615 - 4624 (2019/12/24)
A series of new isolable and thermally stable half-sandwich Ln(II) benzhydryl complexes coordinated by the sterically demanding ligands tert-butylcarbazol-9-yl [tBu4Carb]Ln[(p-tBu-C6H4)2CH](L) (Ln = Sm, L = DME (4); Ln = Yb, L = DME (5); Ln = Yb, L = TMEDA (6)) and 2,7-di-tert-butyl-fluoren-9-trimethylsilylyl [2,7-tBu2-9-Me3Si-C13H6]Yb[(p-tBu-C6H4)2CH](DME) (7) were synthesized by the alkane elimination reaction of [(p-tBu-C6H4)2CH]2Ln(Ln) (Ln = Sm, Yb) with tBu4CarbH and 2,7-tBu2-9-Me3Si-C13H7. X-ray analysis revealed that in 4, 5, and 7 the benzhydryl ligand is coordinated to the metal ion in an ν3 coordination mode, while in 6 it is ν1-bound. The type of coordination of the benzhydryl ligands in diamagnetic 5-7 is retained in their C6D6 solutions. Complexes 4-7 demonstrated unprecedented thermal stability and do not undergo decomposition after heating their solutions in C6D6 or toluene at 100 °C for 72 h. The reactions of [tBu4Carb]Ln[(p-tBu-C6H4)2CH](DME) (Ln = Sm (4), Ln = Yb (5)) with an excess of DME led to the formation of the symmetrical bis(carbazolyl) complex products [tBu4Carb]2Ln(DME)4 (Ln = Sm (8), Yb (9)) isolated in the form of separated ion pairs.
Chloro and alkyl rare-earth complexes supported by ansa-Bis(amidinate) ligands with a rigid o-phenylene linker. Ligand steric bulk: A means of stabilization or destabilization?
Tolpygin, Aleksei O.,Shavyrin, Andrei S.,Cherkasov, Anton V.,Fukin, Georgy K.,Trifonov, Alexander A.
, p. 5405 - 5413 (2012/11/13)
ansa-Bis(amidinate) ligands with a rigid o-phenylene linker, C 6H4-1,2-{NC(tBu)N(2,6-R2C6H 3)H}2 (R = Me (1), iPr (2)), were successfully employed for the synthesis of rare-earth chloro and alkyl species. The reaction of dilithium derivatives of 1 and 2 with LnCl3 (Ln = Y, Lu) afforded the monomeric bis(amidinate) chloro lanthanide complexes [C6H 4-1,2-{NC(tBu)N(2,6-R2C6H3)} 2]Y(THF)(μ-Cl)2Li(THF)2 (R = Me (3), iPr (5)) and [C6H4-1,2-{NC(tBu)N(2,6-Me2C 6H3)}2]LuCl(THF)2 (4). Bis(amidinate) ligands in complexes 3 and 4 are coordinated to the metal atoms in a tetradentate fashion, while the bulkier ligand in 5 is tridentate. The alkane elimination reactions of 1 and 2 with equimolar amounts of (Me 3SiCH2)3Ln(THF)2 (Ln = Y, Lu) allowed us to obtain the monoalkyl complexes [C6H4-1,2- {NC(tBu)N(2,6-R2C6H3)}2]Ln(CH 2SiMe3)(THF)n (Ln = Y, R = Me, n = 1 (6); Ln = Lu, R = Me, n = 1 (7); Ln = Y, R = iPr, n = 2 (8)). The kinetics of thermal decomposition of complexes 6-8 were measured, and for 6 the activation energy was obtained from the temperature dependence of the rate constants (E a = 67.0 ± 1.3 kJ/mol). Complexes 6 and 7 turned out to be inert toward H2 and PhSiH3. Surprisingly, complex 8 was inert toward H2 and PhSiH3 but rapidly cleaved C-O bonds of DME. The reaction resulted in the formation of the methoxy complex {[C 6H4-1,2-{NC(tBu)N(2,6-iPr2C6H 3)}2]Y(μ2-OMe)]}2(μ 2-DME) (9) and methyl vinyl ether.