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Complexes [(2-MeOC6H4N)C(tBu)N(2,6-Me2C6H3)]2LnN(SiMe3)2 (Ln = Y (2), Sm (3)) and [(2-MeOC6H4N)C(tBu)N(2,6-Me2C6H3)]CaN(SiMe3)2(THF) (4) were obtained by reacting Ln[N(SiMe3)2]3 (Ln = Y, Sm) or Ca[N(SiMe3)2]2 with [2-MeOC6H4N]C(tBu)NH(2,6-Me2C6H3) (1) in 1 : 2 or 1 : 1 molar ratios, respectively, and were isolated in 76 (2), 68 (3) and 63% (4) yields. In complexes 2 and 3, the amidinate ligands are tridentate due to the intramolecular coordination of the 2-MeO-group to the metal center. Complex 4 exhibits an unusual κ2-N,O:η3-arene coordination mode of the amidinate ligand. Complexes 2–4 initiate ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL) at room temperature and allow for conversion of 1000 equivalents of monomer into polymer within 180–230 min for rac-LA and 1–7 min for ε-CL. Complexes 2 and 3 enable the formation of atactic polymers (Pr = 0.52–0.58) featuring moderate polydispersities (PDI = 1.30–3.06 for polylactide; PDI = 1.48–2.84 for polycaprolactone). When 4 was applied, PDIs were somewhat narrower (1.28–2.43 for PLA; 1.24–2.48 for PCL). Application of the initiating systems 2–4/iPrOH (1 : 1) leads to the formation of the polymers having close values of the experimental and calculated molecular weights however does not affect strongly the molecular weight distribution. In the presence of 5 equivalents of iPrOH, complexes 2–4 initiate immortal polymerization for both rac-LA and ε-CL. The polymers feature a good match with the experimental and calculated Mn but have moderate polydispersities (PDI = 1.28–1.90 for polylactide; PDI = 1.24–1.96 for polycaprolactone). [ABSTRACT FROM AUTHOR]

The amine elimination reaction of equimolar amounts of ansa-bis(amidine) C6H4-1,2-{NC(tBu)NH(2,6-iPr2C6H3)}2 (L1H) and [(Me3Si)2N]2Yb(THF)2 affords a bis(amidinate) YbII complex [C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Yb(THF) (1) in 68% yield. Complex 1 features a rather rare η1-amido:η6-arene coordination of both amidinate fragments to the YbII ion, resulting in the formation of a bent bis(arene) structure. Oxidation of 1 by I2 regardless of the molar ratio of reagents (2 : 1 or 1 : 1) leads to the formation of the YbIII species [{(2,6-iPr2C6H3)=NC(tBu)NH}-C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}]YbI2(THF)2 (2) in which only one amidinate fragment is coordinated to the ytterbium ion in κ2-N,N′-chelating coordination mode, while the second NCN fragment is protonated in the course of the reaction and is not bound to the metal ion. The outcome of the salt metathesis reaction of LaCl3 with lithium amidinates [C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)}2Li2] (R = Me, iPr) is proven to be strongly affected by the substituent 2,6-R2C6H3 on the amidinate nitrogens. When R = iPr, the salt metathesis reaction occurs smoothly and results in the formation of an ate-chloro-amidinate complex [C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]La(μ2-Cl)Li(THF)(μ2-Cl)2Li(THF)2 (3) in which the LaIII ion is coordinated by both amidinate fragments in a “classic”κ2-N,N′-chelating fashion. In the case of R = Me, the reaction requires prolonged heating for completion. Moreover, the salt metathesis reaction is accompanied by the fragmentation of the ligand and affords a trinuclear chloro-amidinate complex [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]La{[(tBu)C(N-2,6-Me2C6H3)2]La(THF)}2(μ2-Cl)4(μ3-Cl)2 (4) containing one dianionic ansa-bis(amidinate) and two monoanionic [(tBu)C(N-2,6-Me2C6H3)2] amidinate fragments. DFT calculations are conducted to determine the factor that governs this change in coordination mode and, in particular, the effect of the metal oxidation state. [ABSTRACT FROM AUTHOR]

The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(iii) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C–C bonds. The interaction proceeds at mild conditions and gives new indium(iii) derivatives containing iminocyclohexa-1,4-dienolate type ligands. [ABSTRACT FROM AUTHOR]

The amine elimination reaction of equimolar amounts of ansa-bis(amidine) C 6 H 4 -1,2-{NC(tBu)NH(2,6-iPr 2 C 6 H 3 )} 2 (L 1 H) and [(Me 3 Si) 2 N] 2 Yb(THF) 2 affords a bis(amidinate) Yb II complex [C 6 H 4 -1,2-{NC(tBu)N(2,6-iPr 2 C 6 H 3 )} 2 ]Yb(THF) (1) in 68% yield. Complex 1 features a rather rare η 1 -amido:η 6 -arene coordination of both amidinate fragments to the Yb II ion, resulting in the formation of a bent bis(arene) structure. Oxidation of 1 by I 2 regardless of the molar ratio of reagents (2 : 1 or 1 : 1) leads to the formation of the Yb III species [{(2,6-iPr 2 C 6 H 3 )[double bond, length as m-dash]NC(tBu)NH}-C 6 H 4 -1,2-{NC(tBu)N(2,6-iPr 2 C 6 H 3 )}]YbI 2 (THF) 2 (2) in which only one amidinate fragment is coordinated to the ytterbium ion in κ 2 -N,N'-chelating coordination mode, while the second NCN fragment is protonated in the course of the reaction and is not bound to the metal ion. The outcome of the salt metathesis reaction of LaCl 3 with lithium amidinates [C 6 H 4 -1,2-{NC(tBu)N(2,6-R 2 C 6 H 3 )} 2 Li 2 ] (R = Me, iPr) is proven to be strongly affected by the substituent 2,6-R 2 C 6 H 3 on the amidinate nitrogens. When R = iPr, the salt metathesis reaction occurs smoothly and results in the formation of an ate-chloro-amidinate complex [C 6 H 4 -1,2-{NC(tBu)N(2,6-iPr 2 C 6 H 3 )} 2 ]La(μ 2 -Cl)Li(THF)(μ 2 -Cl) 2 Li(THF) 2 (3) in which the La III ion is coordinated by both amidinate fragments in a "classic"κ 2 -N,N'-chelating fashion. In the case of R = Me, the reaction requires prolonged heating for completion. Moreover, the salt metathesis reaction is accompanied by the fragmentation of the ligand and affords a trinuclear chloro-amidinate complex [C 6 H 4 -1,2-{NC(tBu)N(2,6-Me 2 C 6 H 3 )} 2 ]La{[(tBu)C(N-2,6-Me 2 C 6 H 3 ) 2 ]La(THF)} 2 (μ 2 -Cl) 4 (μ 3 -Cl) 2 (4) containing one dianionic ansa-bis(amidinate) and two monoanionic [(tBu)C(N-2,6-Me 2 C 6 H 3 ) 2 ] amidinate fragments. DFT calculations are conducted to determine the factor that governs this change in coordination mode and, in particular, the effect of the metal oxidation state.

The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(III) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C-C bonds. The interaction proceeds at mild conditions and gives new indium(III) derivatives containing iminocyclohexa-1,4-dienolate type ligands.