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

Abstract

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 (NC5 H3 ) (Ar=C6 H3 -2,6-iPr2 )) with Sn[N(SiMe3 )2 ]2 produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH]2 (NC5 H3 )) 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 [DIMPYSn(II) Cl](+) [SnCl3 ](-) ion pair, a bisstannylene DAMPY{Sn(II) [N(SiMe3 )2 ]2 }2 , and the enamine complex MeDIMPYSn(II) , were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and (119) Sn Mössbauer spectroscopy.

N-Coordinated Tin(II) Trifluoromethanesulfonates and Their Reactions with Transition Metal Carbonyls

“…8 A fascinating result was achieved by Fischer applying the DIMPY-type ligand for the stabilization of tin in oxidation state zero (D in Chart 1) and demonstrating the MeDIMPY ligand to give an Sn II enamine complex (E in Chart 1). 9 The synthesis of threecoordinated tin and germanium monocations using neutral chelating ligand {2-[(CH 3 )CN(C 6 H 3 -2,6-i Pr 2 )]-6-(CH 3 O)}-C 5 H 3 N (F in Chart 1) was also reported. 10 As Following the synthesis of compound 3, we further studied the reactivity of both 1 and 3 with AgOTf.…”

Reactivity of low-oxidation state tin compounds: an overview of the benefits of combining DFT Theory and experimental NMR spectroscopy

“…It is interesting to compare this proposed bonding mode with the one put forward for the 2,6-diaminopyridine Sn compound containing a zero valence tin atom, which basically contains a tridentate ligand coordinating the tin atom. 2 Bonding in this compound consists of the two ligand amino groups on one hand and the pyridine nitrogen of the ligand on the other hand, coordinating into the inplane formal empty p orbitals of the Sn atom. The s-type lone pair remains relatively inert, whereas the p-type lone pair is involved in a back-bonding interaction with the p-type LUMO of the ligand.…”

“…f (2) (r) is positive at the locations in a molecule where a nucleophilic attack is preferred and negative where an electrophilic attack is more likely, and gives a one shot picture of a molecule's reactivity towards electrophiles and nucleophiles. It proved to be a key quantity in rationalizing the Woodward Hoffmann rules using conceptual DFT.…”

“…For Sn(0) chemistry, an overview will be provided on the stability and reactivity of these dicoordinate zero-valent compounds to shed some light on the prerequisites to be fulfilled for the synthesis of such reasonably stable Sn(0) derivatives, which only became known experimentally very recently. 2 Stannylenes can simply be considered as tin analogues of the well-known divalent compounds of carbon, the carbenes; the vast majority of these Sn(II) compounds have a singlet ground state. References 3 to 6 provide reviews on the properties and reactivity of stannylenes.…”

The role of the bis-trimethylsilylamido ligand, [N{SiMe3}2]−, in main group chemistry. Part 2: Structural chemistry of the metallic p-block elements

“…The monomeric 3-coordinate benzamidinate compound Sn(PhC{Nt-Bu} 2 )(N{SiMe 3 } 2 ) (115) was Examples of new stannylene compounds with chelating N,N'-ligands continue to be developed. The diamino-and diiminopyridine ligand precursors, 2,6-{ArN(H)CH 2 } 2 (C 5 H 3 N) and 2,6-{ArN = C(Me)} 2 (C 5 H 3 N) react with stannylene 105 to afford products 122 and 123, respectively [103]. N-(diphenylphosphanyl)(2-pyridylmethyl)amine undergoes a trans-amination with stannylene 105 to give the heteroleptic compound containing the corresponding amide 124 [104].…”