New reactivity of Cp2′NbH3,Cp′=η5-C5H4SiMe3. Synthesis, electrosynthesis and reactivity of new carboxylato niobocene complexes

A new family of niobium bidentate carboxylato-containing niobocene complexes, mononuclear Cp2′Nb(κ2-O,O′OOC(C6H5))(3), binuclear [(Cp2′Nb)2(1,4-(κ2-O,O′OOC)2(C6H4))](4)and[(Cp2′Nb)2(1,3-(κ2-O,O′OOC)2(C6H4))](5) and trinuclear [(Cp2′Nb)3(1,3,5-(κ2-O,O′OOC)3(C6H3))](6), have been prepared by the reaction of Cp2′NbH3(1) and the corresponding carboxylic acid, namely (C6H5)COOH, (1,4-COOH)2(C6H4), (1,3-COOH)2(C6H4) and (1,3,5-COOH)3(C6H3). Complexes 3, 4, 5 and 6 have been prepared by an alternative route involving a two-electron reduction of Cp2′NbCl2(2) in the presence of the appropriate molar ratios of the corresponding carboxylic acids. Furthermore, the reaction of complexes 3, 4 and 6 with 2,6-Me2C6H3NC (xylylNC) in the molar ratios 1:1, 1:2 and 1:3, respectively, resulted in opening of the bidentate carboxylato ligand to give the monodentate carboxylato-containing complexes [Cp2′Nb(κ1-OOOC(C6H5))(xylylNC)](7),[(Cp2′Nb(xylylNC))2(1,4-(κ1-OOOC)2(C6H4))](8)and[(Cp2′Nb(xylylNC))3(1,3,5-(κ1-OOOC)3(C6H3))](9). Similarly, complex [(Cp2′Nb(η1-C,κ1-SCS2))3(1,3,5-(κ1-OOOC)3(C6H3))](10) was prepared by reaction of 6 with the appropriate amount of CS2. Complexes 7, 8 and 9 can be prepared in an alternative way by reaction of [Cp2′Nb(H)(xylylNC)] with the corresponding carboxylic acids. The structures of all complexes have been established by spectroscopic techniques. In addition, the X-ray molecular structure of 4 was determined by a single-crystal X-ray diffraction study.

A new family of carboxylato-containing niobocene complexes has been prepared by means of both chemical and electrochemical procedures.Figure optionsDownload as PowerPoint slide