Preparation and coordinating properties of {CH2(o-C6H4CH2SbMe2)}2, a novel wide-angle cis-chelating distibine

Abstract

The unique wide-angle distibine, {CH₂(o-C₆H₄CH₂SbMe₂)}₂, 1, has been prepared indirectly by reaction of Me₂SbCl with the di-Grignard formed unexpectedly by coupling of o-C₆H₄(CH₂MgCl)₂ in concentrated thf solution, and directly by treatment of the {CH₂(o-C₆H₄CH₂MgCl)}₂ with Me₂SbCl. The very oxygen-sensitive distibine 1 has been characterised by ¹H and ¹³C{¹H} NMR spectroscopy and high-resolution EIMS. Oxidation of 1 with Br₂ gives the air-stable tetrabromide {CH₂(o-C₆H₄CH₂SbMe₂Br₂)}₂. Surprisingly, 1 shows a very strong tendency to function as a cis-chelate, e.g. to Pt(IV) in the complex [PtMe₃I(1)], forming an 11-membered ring and providing a stable Pt(IV) stibine complex, the crystal structure of which shows the Sb–Pt–Sb angle to be 95.96(1)°. The yellow Pt(II) complex [PtCl₂(1)] is obtained from reaction of [PtCl₂(MeCN)₂] with 1 and IR spectroscopic data and a crystal structure determination confirm the Cl ligands are mutually cis in this species. Reaction of [W(CO)₄(piperidine)₂] with 1 in refluxing EtOH gives [W(CO)₄(1)], the IR spectrum of which shows four ν(CO) bands, also consistent with cis-Sb₂ coordination. The cis-chelation is also confirmed by single-crystal X-ray structure determinations of two polymorphs of [W(CO)₄(1)].