The Role of 2,6-Diaminopyridine Ligands in the Isolation of an Unprecedented, Low-Valent Tin Complex

Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition-metal chemistry. However, the stabilization of main-group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6-[ArNH-CH2](2)(NC5H3) (Ar=C6H3-2,6-iPr(2))) with Sn[N(SiMe3)(2)](2) produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH](2)(NC5H3)) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low-valent Sn-II complexes, including a [(DIMPYSnCl)-Cl-II](+)[SnCl3](-) ion pair, a bisstannylene DAMPY{Sn-II[N(SiMe3)(2)](2)}(2), and the enamine complex MeDIMPYSnII, were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and Sn-119 Mossbauer spectroscopy.