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‘1,3-Dimetallabenzene’ Derivatives of Niobium and Tantalum by Patrick N. Riley; Robert D. Profilet; Michelle M. Salberg; Phillip E. Fanwick; Ian P. Rothwell is a Chemistry article available to read on EtoBox.

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The alkylidyne bridged compounds [(cb)2M(kt-CSiMe3)2M(cb)2] (la, M = Nb; lb, M =Ta: cb = carbazole) react thermally with one equivalent of alkynes EtC~CEt and Me3SiC~CH to produce new organometallic derivatives 2 and 3, respectively. The molecular structures of 2 and 3 are shown to consist of non-planar six-membered di-metallacycles originating from insertion of an alkyne unit into one of the alkylidyne bridges of 1. Treatment of lb with leads to the monophenoxide [(ArO)(cb)Ta(/~-CSiMe02Ta(cb)2] 4. Treatment of 4 with Me3SiC~CH leads to the corresponding metallacycle [(ArO)(cb)Ta(/~-CSiMe~){/~-C(SiMe3)CHC(SiMe3)~Ta(cb)2] 5. Structural parameters for 2b, 3a, 3b and 5 obtained by X-ray diffraction show delocalization is present with four equivalent M--C and two equivalent C--C distances. The non-planar structure is best described as a twist of the planar [M(/~-C)--M] and [C- ] units within the ring. The non-planar structure of 2a and 2b is maintained in solution as evidenced by diastereotopic methylene protons for the CH\_,CH3 substituents. At elevated temperatures coalescence to a simple A,B3 pattern is observed. From the coalescence temperatures of 328 K for 2b an activation barri

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Author

Patrick N. Riley; Robert D. Profilet; Michelle M. Salberg; Phillip E. Fanwick; Ian P. Rothwell

Publisher

Elsevier Science; Elsevier ; Elsevier Ltd.; Elsevier BV (ISSN 0277-5387)

Published

1998

Language

EN

Field

Chemistry (Physical Sciences)