Conformational and electronic variability of N,N’,O-ligand documented on its coordination to main group halides

Abstract

The coordination chemistry of non-symmetric ligand L (L = 2-(C(Me)N(C₆H₃-2,6-iPr₂))-6-((iPrO)₂PO)C₅H₃N) is with a focus on its ability to adapt its denticity to accommodate different main-group elements within a potentially tridentate ‘pocket’ defined by its phosphonate PO and imine CN groups together with the pyridine-nitrogen atom. For this purpose, chlorides of groups 13, 14, and 16 were selected, namely InCl₃, GeCl₂, Ph₃SnCl, Ph₂SnCl₂, SeCl₄ and TeCl₄. The reaction of L with GeCl₂ and InCl₃ produced [GeCl(L)][GeCl₃] (2) and [InCl₃(L)] (5), respectively. In both compounds, L coordinates to the central metal through all its donor atoms with a κ³-N,N,O-coordination mode. On the contrary, L coordinates Ph₃SnCl and Ph₂SnCl₂ through only the phosphonate PO group, resulting in κ¹-O-coordinated [Ph₃SnCl(L)] (3) and [Ph₂SnCl₂(L)] (4). The diverse chelating ability of L was found in the reaction with TeCl₄ and SeCl₄ yielding 2-(C(CHSeCl₂)N(Dipp))-6-((iPrO)₂PO)C₅H₃N (6) and 2-(C(CH₂TeCl₃)N(Dipp))-6-((iPrO)₂PO)C₅H₃N (7) as a result of a C–H bond activation in the Me group of the C(Me)N fragment. Due to the presence of the M–Cl bond, all compounds 2–7 were subjected to reduction reactions with the aim of synthesising low-valent derivatives. However, only the reduction of 2 with K or KC₈ led to the successful isolation of a product, [Ge(L)] (8). Finally, theoretical studies were carried out to better understand the formation of 6 and 7 as well as the electronic properties of 8.