Fluoroaryl-substituted ketiminate complexes of aluminum

The ketiminate complex AlCl[OC(Me)CHC(Me)N(p-C₆H₄F)]₂ (4) has been prepared from the β-aminoenone, OC(Me)CHC(Me)N(H)(p-C₆H₄F) (3) by lithiation of 3 with n-BuLi, followed by reaction with AlCl₃ and by the reaction of 3 with Me₂AlCl. A second compound, [AlCl₂{OC(Me)CHC(Me)N(H)(p-C₆H₄F)}₄][AlCl₄] (5), was also isolated from the AlCl₃ reaction. The structures of 4 and 5 were determined by X-ray diffraction analysis.     

Four- and five-coordinate magnesium compounds containing ketiminate ligands. Synthesis and characterization of L2Mg, L2Mg(LH), and L2Mg(Py), where L = MeC(O)CHC(NAr)Me

Magnesium complexes containing ketiminate ligands were synthesized and characterized. MgBu₂ reacted readily in toluene with two equiv. of [MeC(O)CHC(NHAr)Me], where Ar = 2,6-diisopropylphenyl, to generate [MeC(O)CHC(NAr)Me]₂Mg (1) in 43% yield. The four-coordinate magnesium compound 1 is very moisture sensitive and acts as a Lewis acid, accepting one equiv. of Lewis base to form five-coordinate magnesium compounds. Compound [MeC(O)CHC(NAr)Me]₂Mg[MeC(O)CHC(NHAr)Me] (2) was obtained in 57% yield from the reaction in toluene of MgBu₂ with three equiv. of [MeC(O)CHC(NHAr)Me]. Treatment of 1 with one equiv. of free ketimine ligands [MeC(O)CHC(NHAr)Me] also led to the formation of 2. The bulky η¹-ketimine of 2 can be replaced with a less bulky Lewis base such as pyridine. Treatment of 1 with excess pyridine in toluene at ambient temperature led to the formation of compound [MeC(O)CHC(NAr)Me]₂Mg[NC₅H₅] (3) as colorless crystalline solids in 51% yield. Compounds 1, 2, and 3 were characterized by NMR and X-ray crystallography. Compounds 2 and 3 showed no activity toward the polymerization of ε-caprolactone at 25 °C after 3 h. However, when the temperature was increased to 70 °C, compounds 2 and 3 efficiently catalyzed polymerization of ε-caprolactone to generate high molecular weight poly-ε-caprolactones. The polydispersity index (PDI) of these poly-ε-caprolactones is in the range 1.57-3.18.     

Lewis Base Assisted Magnesium Complexes Incorporating Pyrrolyl and Ketiminate Ligands: Synthesis,Structural Diversity and Characterization

A series of four, five and six‐coordinated magnesium derivatives integrating with substituted pyrrole and ketimine ligands are conveniently synthesized. Reaction of two equiv of 2‐dimethylaminomethyl pyrrole with Mg[N(SiMe₃)₂]₂ in THF affords the monomeric magnesium complex Mg[C₄H₃N(2‐CH₂NMe₂)]₂ (THF)₂ ( 1 ) in high yield along with elimination of two equiv of HN(SiMe₃)₂. Similarly, the reaction between two equiv of 2‐t‐butylaminomethyl pyrrole and Mg[N(SiMe₃)₂]₂ in THF renders the magnesium derivative, Mg[C₄H₃N(2‐CH₂NH^tBu)]₂(THF)2₂( 2 ) in good yield. Interestingly, reaction between two equiv of 2‐t‐butylaminomethyl pyrrole and Mg[N(SiMe₃)₂]₂ in toluene, instead of THF, generates Mg[C₄H₃N(2‐CH2NH^tBu)]₂ ( 3 ), also in high yield. Furthermore, the assembly of two equiv of ketimine ligand, HOCMeCHCMeNAr (Ar = C₆H₃‐2,6‐ⁱPr₂) and Mg[N(SiMe₃)₂]₂, yields five‐coordinated magnesium derivatives, Mg(OCMeCHCMeNAr)₂(THF) ( 4 ) and Mg(OCMeCHCMeNAr)₂(OEt₂) ( 5 ), using THF and diethyl ether, respectively. All the aforementioned derivatives are characterized by ¹H and ¹³C NMR spectroscopy as well as 1 , 3 , 4 and 5 are subjected to X‐ray diffraction analysis in solid state.     

Synthesis and characterization of Cu(I) and Cu(II) complexes containing ketiminate ligands

A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl₂ with 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]₂ (1). Similarly, Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}₂ (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of triphenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh₃) (3) can be isolated in high yield. Replacing the PPh₃ of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Complexes 2, 3, and 4 were characterized by ¹H and ¹³C NMR spectroscopies and all molecules were structurally characterized by X-ray diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coordinated terminal ketiminates and the other is lithium-copper-coordinated bridging ketiminates.     

Ketiminate supported aluminum(III) complexes: Synthesis, characterization and reactivity

The reaction of LLi, (L = [RNC(Me)CHC(Me) = O] (R = C₂H₄NEt₂)), with AlCl₃ at −78 °C forms the mono-ketiminate product, LAlCl₂, 1, while the same reaction at 0 °C affords the bis-ketiminate complex, [{(LH)₂AlCl}(Cl₂)], 2, Reduction of 1 with Li^o, K^o or Mg^o yielded an unusual dimeric aluminum(III) species, [L′AlCl]₂, 3, where C-C coupling of the ligand backbone is observed.