Synthesis of the Novel [W3PdS4H3(dmpe)3(CO)]+ Cubane Cluster and Kinetic Studies on the Substitution of Coordinated Hydrides in Acidic Media

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• 作者：André ; s G. Algarra ; Manuel G. Basallote ; Marta Feliz ; M. Jesú ; s Fern&aacute ; ndez-Trujillo ; Eva Guillamó ; n ; Rosa Llusar ; and Cristian Vicent
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：July 10, 2006
• 年：2006
• 卷：45
• 期：14
• 页码：5576 - 5584
• 全文大小：140K
• 年卷期：v.45,no.14(July 10, 2006)
• ISSN：1520-510X

文摘

Reaction of the incomplete cuboidal [W<SUB>3S₄H₃(dmpe)₃]⁺ cluster with a Pd(0) complex under a CO atmosphere producesa rare example of a heterodimetallic hydrido cluster of formula [W₃PdS₄H₃(dmpe)₃(CO)]⁺ ([1]⁺). There are notsignificant changes in the W-W bond lengths on going from the trinuclear to the tetranuclear cluster. The averageW-W and W-Pd bond distances of 2.769[10] and 2.90[2] &Aring;, respectively, are consistent with the presence ofsingle bonds between metal atoms. The heterodimetallic [1]⁺ complex is easier to oxidize and more difficult toreduce than its trinuclear precursor, which reflects the electron-donating capability of the Pd(CO) fragment. However,mechanistic studies on the reaction of [1]⁺ with acids show a lower basicity for this complex in comparison withthat of its trinuclear precursor, so there is a major electron-density rearrangement within the cluster core uponPd(CO) coordination. This rearrangement is also reflected in an unusual expansion of the sulfur tetrahedron withinthe W₃PdS₄ core with the concomitant elongation of the W-S bond distances by 0.04 &Aring; with respect to the analogousbond lengths in the trinuclear precursor. For those thermodynamically favored proton-transfer processes, the reactionmechanism of [1]⁺ with acids is quite similar to that observed for the incomplete trinuclear cluster, with only smallchanges in the rate constants. The reaction of [1]⁺ with HCl in acetonitrile/water mixtures produces [W₃PdS₄Cl₃(dmpe)₃(CO)]⁺ ([2]⁺) in two kinetically distinguishable steps. Proton transfer occurs in the initial step, in which theW-H bonds are attacked by the acid to yield dihydrogen-bonded adducts that are further attacked by an acetonitrilemolecule to give [W₃PdS₄(CH₃CN)₃(dmpe)₃(CO)]⁴⁺ and dihydrogen. The nature of processes involved in the secondstep are not well-understood with the present data, although it is very likely that these correspond to some secondaryprocesses. In the third resolved step, the coordinated CH₃CN ligands in [W₃PdS₄(CH₃CN)₃(dmpe)₃(CO)]⁴⁺ aresubstituted by Cl^- to afford the final [2]⁺ product. No reaction is observed between [1]⁺ and HCl in neat acetonitrile,whereas the product of the reaction of [1]⁺ with HBF₄ or Hpts (pts^- = p-toluenesulfonate) in this solvent is[W₃PdS₄(CH₃CN)₃(dmpe)₃(CO)]⁴⁺. The reaction occurs in a single kinetic step with a first- (Hpts) or second-order(HBF₄) dependence with respect to the acid. The first- and second-order acid dependences can be interpretedthrough the initial formation of dihydrogen adducts with one or two acid molecules, respectively.