Self-assembly of a metal-organic cage-like structure bearing cofacial redox-active bis-(o-semiquinone) copper(II) units.

Ditopic di-o-quinone with a resorcinol bridge exhibits the ability to self-assemble in a reaction with copper, giving a cage-like binuclear complex that, due to the cofacially placed metal ions, is capable of encapsulation of different solvent molecules as guest ligands. Notably, the geometry of the internal cavity of this complex adjusts depending on the coordinating properties of the encapsulated molecule (mono- or bidentate). A feature of this species is that the cage-forming units are copper(II) bis-semiquinonate moieties, capable of undergoing ligand-centered redox transformations. Electrochemical and EPR spectroscopy studies showed that there is a channel for intramolecular electronic exchange interactions between the redox centres of the molecule.

2-Imino-2,3-dihydrobenzoxazole-a useful platform for designing rare- and alkaline earth complexes with variable di- and trianionic O,N,N, ligands.

The reactions of 2-imino-2,3-dihydrobenzoxazole LH with M[N(SiMe3)2]2(THF)2 (M = Yb and Ca) and Y(CH2SiMe3)3(THF)2 proceed with the opening of the dihydrobenzoxazole ring and the elimination of HN(SiMe3)2 or SiMe4. Besides, in the case of Yb[N(SiMe3)2]2(THF)2, an electron transfer from Yb(II) to L takes place and Yb(III) complex 1 is coordinated by a dianionic phenolate ligand containing a pendant radical-anionic diazabutadiene fragment form. When LH is reacted with Ca[N(SiMe3)2]2(THF)2, C-H bond activation of a methyl fragment by imino nitrogen occurs and affords a dimeric calcium complex 2. In 2, the phenolate ligand is dianionic due to the presence of the amido-imino fragment [R-NC(CH3)-C(CH2)-NR']- (R = 2,4-tBu2-C6H2O; R' = 2,6-iPr2C6H3). In situ generated ate-complex {Na(Et2O)n}{Ca[N(SiMe3)2]3} also enables C-H bond activation, however the dianionic phenolate ligand in the resulting complex 3 contains an amido-imino fragment [R-N-C(CH2)-C(CH3)NR']- featuring the sequence of N-C and NC bonds opposite to that in 2. The reaction of Y(CH2SiMe3)3(THF)2 with LH affords mono(alkyl) yttrium complex 4. 4 contains a dianionic amido-imino phenolate ligand resulting from the migration of one alkyl group to the CN bond [R-N-C(Me)(CH2SiMe3)-C(Me)NR']. 4 undergoes slow intramolecular C-H bond activation of the residual CH3 group to afford a yttrium complex coordinated by a trianionic diamido-phenolate ligand [R-N-C(Me)(CH2SiMe3)-C(CH2)NR'].

Amine-boranes reactions promoted by lanthanide(II) ions.

The catalytic activity in amine-borane dehydrogenation is shown for the first time for Ln(II) species using complexes [{(p-tBu-C6H4)2CH}2M·L] (M = Yb, Sm, L = (DME)2, TMEDA). The protonation of M(II)-C bonds with HNR1R2BH3 affords amidoborane complexes [M(NR1R2BH3)2L], which under excess HNMe2BH3 transform to [NMe2BH2NMe2BH3]- derivatives, both serving as the dehydrocoupling intermediates.

Metallacyclic yttrium alkyl and hydrido complexes: synthesis, structures and catalytic activity in intermolecular olefin hydrophosphination and hydroamination.

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.

Rare-earth dichloro and bis(alkyl) complexes supported by bulky amido-imino ligand. Synthesis, structure, reactivity and catalytic activity in isoprene polymerization.

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.