This review covers recent achievements in the intermolecular hydrophosphination and hydroamination of alkenes, dienes and alkynes catalyzed by organolanthanides.
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.
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.
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