Alkaline Earth Complexes of a Sterically Demanding Guanidinate Ligand: Alkaline Earth Guanidinate Complexes

Moxey, Graeme J.; Blake, Alexander J.; Lewis, William; Kays, Deborah L.

Abstract

The synthesis of the guanidine MesN{C(NCy2)}N(H)Mes (LH; Mes = 2,4,6-Me3C6H2, Cy = cyclohexyl), and its use as a proligand for the synthesis of alkaline earth metal complexes are reported. Described herein are (i) an unusual Hauser base cubane, (ii) a homoleptic and a base-stabilized magnesium complex featuring the same guanidinate ligands, and (iii) the comparison of a series of alkaline earth (Mg, Ca, Sr, Ba) bis(guanidinate) complexes, which allows the opportunity to compare the changing trends in bonding as the Group is descended. The reaction between LH and MeMgI(OEt2)2 yields the Hauser base as a mixture of the tetramer [Mg4L4(?3-I)4] (1a) and dimer [Mg2L2(?-I)2(OEt2)2] (1b), and the reaction with two equivalents of MgnBu2 leads to the formation of four-coordinate [MgL2] (2), which features a square-planar geometry for the magnesium cation, or five-coordinate [MgL2(THF)] (3), depending on the solvent used. 1a is the first crystallographically-characterized cubane structure to consist of four LAeX (L = ligand, X = halide) units. The complexes [AeL2(THF)2] (Ae = Ca, 4; Ae = Sr, 5) and [BaL2] (6) were synthesized via redox transmetallation/ligand exchange reactions. Complex 6 is the first example of a homoleptic, monomeric barium complex of the NCN ligand family, with the structure stabilized by a number of barium-arene interactions in the solid state.

• Journal Article Type: Article
• Acceptance Date: Oct 28, 2015
• Online Publication Date: Dec 2, 2015
• Publication Date: Dec 2, 2015
• Deposit Date: Jan 13, 2016
• Publicly Available Date: Jan 13, 2016
• Journal: European Journal of Inorganic Chemistry
• Print ISSN: 1434-1948
• Electronic ISSN: 1434-1948
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 2015
• Issue: 36
• Pages: 5892-5902
• DOI: https://doi.org/10.1002/ejic.201501239
• Keywords: alkaline, earth metals, N ligands, bidentate ligands, ligand effects, coordiination modes
• Public URL: https://nottingham-repository.worktribe.com/output/770416
• Publisher URL: http://onlinelibrary.wiley.com/doi/10.1002/ejic.201501239/abstract