Selective Preparation of Sterically Encumbered Diaryltin Dihalides from Grignard Reagents via Salt Metathesis and Halide Exchange

Hypercoordination by Multiple Dangling Benzylmethoxy Ligands in Highly Crowded Triaryltin Bromide [(2-MeOCH2 C6 H4 )]3 SnBr and Diaryltin Mixed Halides [(2-MeOCH2 C6 H4 )]2 SnBrCl, and a related Distannane and Distannoxane

The reaction between the Grignard reagent formed from Mg and 2-bromobenzylmethyl ether and SnCl4 produced four products: [2-(MeOCH2 )C6 H4 ]3 SnBr (1), [2-(MeOCH2 )C6 H4 ]2 SnX2 (2, X2 =Br2 (a) and BrCl (b)), [{2-(MeOCH2 )C6 H4 }3 Sn]2 (3), and [{2-(MeOCH2 )C6 H4 }2 SnBr]2 O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O-Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2a the resulting hexacoordinate structure exhibits two very short O-Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O-Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn-O-Sn bond angle of 148.1(2)° which is larger compared to other distannoxane structures. The intermolecular interactions between Sn-O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms. The various 119 Sn, 13 C and 1 H NMR spectra are in accord with their structural analysis for 1 and 2, and in the solid state 13 C NMR spectrum of 1 the dangling methylene group is observable whereas is solution there is a rapid dynamic equilibrium resulting in a single resonance for all methylene groups.

Diaryltin Dihydrides and Aryltin Trihydrides with Intriguing Stability

In the last few decades, organotin hydrides have proven their potential as building blocks for a great variety of organometallic compounds. In this context, organotin hydrides with sterically shielding aryl substituents have attracted special interest, as these ligands can kinetically stabilize metastable products. The selective synthesis of aryltin halide compounds Ar*₂SnCl₂ and Ar*SnI₃ featuring the highly sterically encumbered aryl ligand Ar* (^iPrAr* = 2,6-(Ph₂CH)₂-4-iPrC₆H₂; ^MeAr* = 2,6-(Ph₂CH)₂-4-MeC₆H₂) is presented. These aryltin halides were converted into corresponding aryltin hydrides Ar*₂SnH₂ and Ar*SnH₃, which exhibit a surprisingly high thermal stability and oxygen tolerance.