The first example of an intermolecular weak (agostic)γ-methyl-metal interaction: the low temperature single crystal X-ray and neutron diffraction structure of (MgR2)∞[R = CH(SiMe3)2]
Abstract
The crystalline homoleptic magnesium alkyl (MgR2)∞[R = CH(SiMe3)2], derived from Mg(OC6H2But2-2,6-Me-4)2 and 2LiR, is shown by low temperature X-ray (190 K) and neutron (15 K) diffraction to have the structure [Mg{CH(SiMe3)[SiMe2(µ-Me)]}R]∞, with the MgC2C′ unit coplanar (C′ refers to µ-C′H3 of a neighbouring Mg′R2 moiety), Mg-C 2.117(4) and 2.105(4)Å, short Mg ⋯ C [2.535(4)Å] and Mg′⋯ H [2.333(4), 2.414(5), and 2.516(4)Å] contacts, and the bridging methyl group adopting a pseudo trigonal bipyramidal arrangement [Mg ⋯ C(H)3-Si: Mg′⋯ C-Si 172.3(2)°, <H-C-H> 110.4°, and a longer {1.915(8)Å} C-Si bond than those {av.1.877(6)Å} not involved in a Mg contact].