Structural diversity of polynuclear Mg _x O _y cores in magnesium phenoxide complexes

Abstract

The binuclear complex bis(2,6-di-tert-butyl-4-methylphenolato)-1κO,2κO-(1,2-dimethoxyethane-1κO,O')bis(μ-phenylmethanolato-1:2κO:O)(tetrahydrofuran-2κO)dimagnesium(II), [Mg(CHO)(CHO)(CHO)(CHO)] or [(BHT)(DME)Mg(μ-OBn)Mg(THF)(BHT)], (I), was obtained from the complex [(BHT)Mg(μ-OBn)(THF)] by substitution of one tetrahydrofuran (THF) molecule with 1,2-dimethoxyethane (DME) in toluene (BHT is O-2,6-Bu-4-MeCH and Bn is benzyl). The trinuclear complex bis(2,6-di-tert-butyl-4-methylphenolato)-1κO,3κO-tetrakis(μ-2-methylphenolato)-1:2κO:O;2:3κO:O-bis(tetrahydrofuran)-1κO,3κO-trimagnesium(II), [Mg(CHO)(CHO)(CHO)] or [(BHT)(μ-O-2-MeCH)(THF)Mg], (II), was formed from a mixture of BuMg, [(BHT)Mg(Bu)(THF)] and 2-methylphenol. An unusual tetranuclear complex, bis(μ-2-aminoethanolato-κO:O:O,N)tetrakis(μ-2-aminoethanolato-κO:O,N)bis(2,6-di-tert-butyl-4-methylphenolato-κO)tetramagnesium(II), [Mg(CHNO)(CHO)] or Mg(BHT)(OCHCHNH), (III), resulted from the reaction between (BHT)Mg(THF) and 2-aminoethanol. A polymerization test demonstrated the ability of (III) to catalyse the ring-opening polymerization of ℇ-caprolactone without activation by alcohol. In all three complexes (I)-(III), the BHT ligand demonstrates the terminal κO-coordination mode. Complexes (I), (II) and (III) have binuclear rhomboid MgO, trinuclear chain-like MgO and bicubic MgO cores, respectively. A survey of the literature on known polynuclear MgO core types for ArO-Mg complexes is also presented.

Coordination Ring-Opening Polymerization of Cyclic Esters: A Critical Overview of DFT Modeling and Visualization of the Reaction Mechanisms

“…As demonstrated in a number of publications, heteroleptic metal alkoxides form stable binuclear complexes [69,94,97,99,140,147,148,149] that are able to catalyze ROP of cyclic esters by both binuclear and mononuclear mechanisms. DFT modeling has been shown to be an effective instrument of choice of the preferable reaction pathway.…”

DFT Visualization and Experimental Evidence of BHT-Mg-Catalyzed Copolymerization of Lactides, Lactones and Ethylene Phosphates

“…In the absence of polymerization that maintains BHT-Mg species in active mononuclear form, these species can turn into inactive clusters. The formation of such polymetallic species by the reaction of BHT-Mg complexes with lactates in the absence of ROP monomers had been demonstrated in our recent publication [92].…”

Comparative Experimental and Theoretical Study of Mg, Al and Zn Aryloxy Complexes in Copolymerization of Cyclic Esters: The Role of the Metal Coordination in Formation of Random Copolymers

“…In the recent years, the promising catalytic properties in ROP of different cyclic esters were demonstrated for the complexes of ‘biometals’ (Na, Mg, Ca, Zn and Al) with bulky phenols such as 2,6-di- tert -butyl-4-methylphenol (BHT-H) [ 81 , 93 , 94 , 95 , 96 , 97 , 98 , 99 ]. These synthetically available complexes represent a suitable model for the understanding fundamentals of co-ROP [ 47 ].…”