DACH-Bridged (DACH = trans-1,2-Diaminocyclohexane) Bis(iminophosphonamide) Derivatives of Groups 3 and 13 and Their Use in the Enantiomorphic Polymerization of Methyl Methacrylate

A straightforward and flexible one-pot synthesis of a series of racemic trans-1,2-diaminocyclohexyl (DACH)-linked N-aryl bis(iminophosphonamines) is reported. These compounds were readily metalated with either nBuLi or Et3Al. The five-coordinate asymmetric environments provided by the ligands in the monometallic species were readily apparent from the useful and diagnostic 31P{1H} NMR spectra and correlated with the observed solid-state configurations. Similar reactions with the sterically encumbered yttrium amide [Y{N(SiMe3)2}3] were only observed to produce the analogous N5-coordinated amide under forcing conditions, while reactions with the less sterically encumbered [M{N(SiHMe2)2}3(THF)n] (M = Sc (n = 2), Y (n = 3)) gave smooth conversion to the desired monometallic chelate complexes. All of the monometallic and bimetallic group 3 and group 13 compounds were assessed for the stereoselective polymerization of methyl methacrylate. Although the aluminum compounds were inactive as single-component initiato...