Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The reaction of niobocene trihydride [Cp2NbH3] with one equivalent of an alkyl- or aryltin halide XnSnR4-n (n = 1, 2) leads to products of the displacement of hydride by tin, i.e. [Cp2NbH2(SnX3-nRn)] [R = Me, n = 3 (1); R = Me, × = Cl, n = 2 (3); R = Ph, n = 3 (4); R = Ph, × = Cl, n = 2 (5); R = Et, × = Br, n = 2 (6)]. Use of an excess of the tin reagent results in a halodealkylation exchange reaction at the tin atom bound to the metal center. Reaction of the mono(silyl) complexes [Cp2NbH2(SiXMe2)] (X = Cl, Ph) with organotin halides XnSnR4-n gives products of the displacement of silicon by tin, whereas the bis(silyl) complex [Cp2NbH(SiPhMe2)2] does not undergo this reaction. The bis(tin)-substituted niobocene [Cp2NbH(SnMe3)2] has been prepared by the reaction of [Cp2NbH2(SnMe3)] with the tin amide Me3SnNMe2 under thermal conditions, as well as by the literature method of thermolysis of [Cp2NbH(η2-C2H3Ph)] in the presence of Me3SnH. Reaction of [Cp2NbH(SnMe3)2] with two equivalents of Cl2SnMe2 affords the bis(tin)-substituted complex [Cp2NbH(SnClMe2)2] (9). The possible presence of non-classical hypervalent H···Sn-Cl interactions in this compound has been assessed by means of X-ray structure analysis. The structural data for 9 are in accord with an essentially classical description as a tin-substituted dihydride complex without significant Sn···H interactions.
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