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-iPr2)) with Sn[N(SiMe3)2]2 produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH]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 SnII complexes, including a [DIMPYSnIICl]+[SnCl3]− ion pair, a bisstannylene DAMPY{SnII[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 119Sn Mössbauer spectroscopy