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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 reactions of bis(trimethylsilylmethyl)yttrium complexessupported by bulky amidopyridinate (Ap) and amidinate (Amd) ligands(LY(CH2SiMe3)2(THF)n: L = Ap, n= 1 (1); L = Amd, n= 1 (2)) with 2,6-diisopropylaniline andphenylacetylene were performed. The reaction of 1withan equimolar amount of 2,6-diisopropylaniline occurs with TMS eliminationand affords an yttrium alkyl anilido species which was isolated asa DME adduct, ApY(CH2SiMe3)(NH-2,6-iPr2C6H3)(DME) (3).The protonolysis of 3with phenylacetylene results inthe alkynyl anilido derivative ApY(CCPh)(NH-2,6-iPr2C6H3)(DME) (6).The treatment of complexes 3and 6with2,2′-bipy leads to the formation of the bis(anilido) derivativeApY(NH-2,6-iPr2C6H3)2(bipy) (5). The formation of a dimericcomplex containing two ApY fragments linked by two μ2-alkynyl groups and a μ-η2:η2-butatrienediyl fragment, [{AmdY(μ2-CCPh)}2(μ2-η2:η2-PhCCCCPh)] (7), was observed in the reaction of 2with 2 equiv of phenylacetylene. [ABSTRACT FROM AUTHOR]

ansa-Bis(amidinate) ligands with a rigid o-phenylene linker, C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)H}2(R = Me (1), iPr (2)), were successfully employed for the synthesis of rare-earth chloroand alkyl species. The reaction of dilithium derivatives of 1and 2with LnCl3(Ln = Y, Lu) affordedthe monomeric bis(amidinate) chloro lanthanide complexes [C6H4-1,2-{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-Me2C6H3)}2]LuCl(THF)2(4). Bis(amidinate) ligandsin complexes 3and 4are coordinated tothe metal atoms in a tetradentate fashion, while the bulkier ligandin 5is tridentate. The alkane elimination reactionsof 1and 2with equimolar amounts of (Me3SiCH2)3Ln(THF)2(Ln = Y,Lu) allowed us to obtain the monoalkyl complexes [C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)}2]Ln(CH2SiMe3)(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 6–8were measured, and for 6the activation energy was obtained from the temperature dependenceof the rate constants (Ea= 67.0 ±1.3 kJ/mol). Complexes 6and 7turned outto be inert toward H2and PhSiH3. Surprisingly,complex 8was inert toward H2and PhSiH3but rapidly cleaved C–O bonds of DME. The reactionresulted in the formation of the methoxy complex {[C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Y(μ2-OMe)]}2(μ2-DME) (9) andmethyl vinyl ether. [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.

Addition of two Ln-H bonds of an Yb(II) hydrido complex supported by bulky amidinate ligand to a C≡C bond lead to the formation of 1,2-dianionic bibenzyl fragment. Both Yb(II) and hydrido centers are oxidized under the reaction conditions. The resulting Yb(II)-η(6) -arene interaction is surprisingly robust: the arene cannot be replaced from the metal coordination sphere when treated with Lewis bases., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S. The oxidation of 2 with oxygen and with sulfur proceeds through the derivative [Sn(isq)(2)Et(2)] (7), which undergoes alkyl elimination to give two new tin(IV) compounds, [Sn(ap)(isq)Et] (5) and [Sn(ap)(EtImQ)Et] (6) (EtImQ=2,4-di-tert-butyl-6-(2,6-diisopropylphenylimino)-3-ethylcyclohexa-1,4-dienolate ligand), respectively, along with the corresponding alkyltin(IV) oxide and sulfide. Complexes 3-5 and 7 were studied by EPR spectroscopy. The structures of 3, 4 and 6 were investigated by X-ray analysis.