Divalent tin and lead compounds EX2 acting as bridging ligands in [{(CO)5M}2EX2]2- (E = Sn, Pb; M = Cr, Mo, W): Preparation and properties

Article abstract of DOI:10.1002/cber.19971300604

The reaction of Na₂[M₂(CO)₁₀] (M = Cr, Mo, W) with SnHal₂ (Hal = CI, Br) is a well established procedure for the synthesis of anions of type A, [{(CO)sMJSnHal3]~. Conditions are described which, for the same type of procedure, result in the additional formation of dianions of type B, [((CO)₅M)₂SnHal₂]^2-. Procedures for separating these two types of anions in the form of their stable [Ph₄P]⁺ or [nBu₄NJ⁺ salts by appropriate salt metathesis are presented. The structures of these species have been characterized by X-ray analysis of three salts containing type A anions and two salts containing type B anions. The reactivity of the type B salts containing the bulky cations [Ph₄P]⁺ or [nBu₄N]⁺, respectively, is remarkably low; the salts are, however, transformed into highly reactive sodium salts by further metathesis with Na[BPh₄]. In such salts the halide substituents are easily exchanged as shown by the synthesis of [((CO)₅Cr}₂Sn(oxinato)]^- (4)^-, from [Na-(THF)_x]₂[{(CO)₅CrJ}SnCl₂] and sodium 8-oxoquinolate, Na[C₉H₆NOJ. The structure of the anion, 4, is compared to the structure of [|(CO)₅Cr]Sn(oxinato)₂] (5), which is obtained from [((CO)₅Cr)SnCl₂ ·THF] and sodium 8-oxochinolate. The preparation of the dinuclear anions [((CO)₅CrJ₂E(OOCCH₃)₂]^2- (E = Sn, 2g; E = Pb, 3) is accomplished by the reaction of [Ph₄P]₂[Cr₂(CO)₁₀] with the corresponding acetates E(OOCCH₃)₂. While 2g and 3 are formal analogues of the type-B anions, their structures reveal an asymmetrical η²-coordination of the two acetato ligands, in each case ending up in a 4 + 2 coordination for the main group centres, instead of the four-coordination observed for [{(CO)₅M)₂SnHal₂]^2-. All compounds have been characterized by usual spectroscopic and analytical techniques. X-ray analyses have been performed for selected examples. ¹¹⁹Sn-NMR data are presented for all of the compounds which contain tin-centred ligands. VCH Verlagsgesellschaft mbH,.