One-electron transfer processes in the reaction of tin(II) halides with substituted o-quinones; crystal structure of bis(3,5-di-t-butylcatecholato)tin–1,10-phenanthroline–dimethylformamide (1/1/2)

Abstract

The reaction of SnX₂(X = Cl, Br, or I) with 3,5-di-t-butl-1,2-benzoquinone or phenanthrene-9,10-quinone in the presence of 2,2′-bipyridine (bipy) or 1,10-phenanthroline gives the adducts of the appropriate SnX₂(diolate) formed by oxidative addition. Various spectroscopic results (i.r., ¹H, ¹³C n.m.r.) confirm the conversion of o-quinone into the corresponding catecholate. E.s.r. studies show that semiquinone derivatives are intermediates in these processes, and a mechanism is proposed to satisfy both preparative and e.s.r. results in terms of two successive one-electron-transfer processes. The crystal structure of bis(3,5-t-butylcatecholato)tin(IV)–1,10-phenanthroline–dimethylformamide (1/1/2) has been determined by X-ray crystallography using the heavy-atom method. Crystal parameters are triclinic, space group P, a= 10.761(2), b= 14.357(3), c= 15.361(4)Å, α= 93.5(3), β= 95.8(2), γ= 94.8(3)°, and Z= 2. The structure analysis, based on 3 005 observed reflections [I > 2σ(I)] gave R= 0.0699. The average Sn–O distance [2.008(8)Å] is typical of tin(IV) compounds and the average C–O distance [1.36(1)Å] again confirms that the ligand is an aromatic 1,2-diolate.