Steric and Electronic Properties of the Bulky Terphenyl Ligand ArtBu6 (ArtBu6 = C6H3-2,6-(C6H2-2,4,6-tBu3)2) and Synthesis of Its Tin Derivatives ArtBu6SnCl, ArtBu6SnSn(H)2ArtBu6, and ArtBu6SnSnArtBu6: A New Route to a Distannyne via Thermolysis of the Asymmetric Hydride ArtBu6SnSn(H)2ArtBu6

A larger scale, modified synthesis of the bulky terphenyl ligand iodo precursor (ArI)-I-tB-I-u6 (1; Ar-tB(u6) = C6H3-2,6-(C6H2-2,4,6-Bu-t(3))(2)), featuring six tert-butyl groups on the flanking aryl rings, and the synthesis of its tin derivatives (ArSnCl)-Sn-tB-Sn-u6 (2), (ArSnSn)-Sn-tB-Sn-u6(H )(2)Ar-tB(u6) (3), and (ArSnSnArtBu6)-Sn-tB-Sn-u6 (4) are described. For the key reagent (ArI)-I-tB-I-u6 (1), recently reported by Schrock, Hoyveda, and co-workers, modifications to the synthesis using the easily prepared Grignard reagent EtMgBr to obtain (ArMgX)-Mg-tB-Mg-u6, as well as use of their published trituration and iodination protocols in hexane, allowed isolation of ca. 80 g quantities of (ArI)-I-tB-I-u6 (1). The tin(II) halide derivative 2 and the unsymmetrical hydride 3 were synthesized by salt metathesis and reduction with DIBAL ((Bu2AlH)-Bu-t), respectively. The distannyne 4 was obtained by a new synthetic route by the dehydrogenation of 3 at 100 degrees C in toluene. It was also synthesized by reduction of 2 with KC8. All compounds were characterized using single-crystal X-ray diffraction, multinuclear NMR, UV-vis, and IR spectroscopy. The Sn-119 NMR and UV-vis spectra of 2-4 reveal absorptions considerably shifted from those of other terphenyl-substituted analogues and along with their structural and reactive behavior show that the steric demands of Ar-tB(u6) are the highest among terphenyl ligands and are sufficiently great to prevent formation of the stannylene Sn (Ar-tB(u6))(2).