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 kappa 3-N,N,O-coordination mode. On the contrary, L coordinates Ph3SnCl and Ph2SnCl2 through only the phosphonate PO group, resulting in kappa 1-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.