Allyl complexes of the heavy alkaline-earth metals: molecular structure and catalytic behavior

An η3‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex

“…Metal (trimethylsilyl)allyl complexes have been previously evaluated as initiators for the polymerization of MMA. [16,27] Consequently,t he MMA polymerization activity of 1 was evaluated and compared to the activities of the [{MgA' 2 } 2 ] complex and the previously reported K[A']. [27b] All polymerizations were conducted under an inert atmosphere in which the initiator,MMA (0.5 g), and toluene (2 m)were combined and allowed to react at the designated temperature and time, as detailed in Table 1.…”

“…These results are consistent with the hypothesis that the polymerization inactivity of previously reported [MgA' 2 (thf) 2 ]species is due in part to solvent coordination, thereby hindering monomer coordination to the metal center. [16] When comparing the polymers produced using K[A'], 1, and [{MgA' 2 } 2 ], we found that initiators K[A']a nd 1 both produce atactic poly(methylmethacrylate) (PMMA) with similar molecular weights (M n )a nd dispersities (). In contrast, [{MgA' 2 } 2 ]p roduced isotactically enriched PMMA having asignificantly higher M n and abroader dispersity ( = 3.83;T able 1, entry 3).…”

“…[15] Similarly,t he solvated species [MgA' 2 (thf) 2 ]i si nactive as an initiator for methyl methacrylate (MMA) polymerization, which is plausibly the result of the thf ligands hindering access to the metal center. [16] In contrast, preliminary tests (confirmed below) indicated that the unsolvated [{MgA' 2 } 2 ]d imer displays modest activity for MMA polymerization, ar esult that prompted us to explore the properties of the compound more completely.…”

An η3‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex

“…The potentially depressant effect of such bases in Group 2 compounds was demonstrated by the ability of [{BDI Dipp }CaH] 2 to insert non‐activated α‐olefins, generating [{BDI Dipp }CaR] 2 calcium alkyl species, whereas the related [{BDI Dipp }CaH(thf)] 2 is essentially inert . Similarly, the solvated species [MgA′ 2 (thf) 2 ] is inactive as an initiator for methyl methacrylate (MMA) polymerization, which is plausibly the result of the thf ligands hindering access to the metal center . In contrast, preliminary tests (confirmed below) indicated that the unsolvated [{MgA′ 2 } 2 ] dimer displays modest activity for MMA polymerization, a result that prompted us to explore the properties of the compound more completely.…”

Bis(1,3‐trimethylsilylallyl)beryllium

“…A series of DFT experiments suggest that a beryllium complex that contains p-bound allyl groups is not only possible but energetically favorable in the absence of coordinated bases; p-bonded allyl groups are thus reasonable for the entire set of Group 2 elements, from beryllium to barium. [29]…”