Synthesis and characterization of redox-active C4-bridged rigid-rod complexes with acetylide-substituted manganese end groups

Koushik Venkatesan, Thomas Fox, Helmut W. Schmalle, Heinz Berke*

*Corresponding author for this work

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

The symmetric d5 trans-bis(alkynyl) complexes [Mn(R′2PCH2CH2PR′2) 2(C≡CR)2] (R′ = Me, R = SiEt3, 3a; R′ = Me, R = SiiPr3, 3b; R′ = Me, R = Si( tBu)Me2, 3c; R′ = Et, R = SiEt3, 4a; R′ = Et, R = SiiPr3, 4b; R′ = Et, R = Si( tBu)Me2, 4c) can be prepared by the reaction of [Mn(R′2PCH2CH2PR′2) 2Br2] (R′ = Me, 1; R′ = Et, 2) with 2 equiv of LiC≡CR (R = SiEt3, SiiPr3, Si( tBu)Me2). The reactions of species 3 and 4 with [Cp 2Fe] [PF6] yield the corresponding d4 complexes [Mn(dmpe)2(C≡CR)2][PF6] (R′ = Me, R = SiEt3, 5a; R′ = Me, R = SiiPr3, 5b; R′ = Me, R = Si(tBu)Me2, 5c; R′ = Et, R = SiEt3, 6a; R′ = Et, R = SiiPr3, 6b; R′ = Et, R = Si(tBu)Me2, 6c). The asymmetrically substituted trans-bis(alkynyl) complexes [Mn(dmpe)2-(C≡CR)(C≡CH)] [PF6] (R′ = Me, R = SiEt3, 10a; R′ = Me, R = SiiPr3, 10b; R′ = Me, R = Si(tBu)Me 2, 10c) are prepared by the reaction of the vinylidene compounds Mn(dmpe)2(C≡CR)(C=CH2) (R′ = Me, R = SiEt 3, 9a; R′ = Me, R = SiiPr3, 9b; R′ = Me, R = Si(tBu)Me2, 9c) with 2 equiv of [Cp 2Fe] [PF6] and 1 equiv of quinuclidine. The mixed-valent complexes [{Mn-(dmpe)2(C≡CR)}2(μ-C 4)][PF6] [11]+ are obtained by the reaction of 10 with 1 equiv of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The neutral dinuclear Mn(II)/Mn(II) compounds [{Mn-(dmpe)2(C≡CR)} 2(μ-C4)] (R = SiEt3, 11a; R = Si iPr3, 11b; R = Si(tBu)Me2, 11c) are synthesized by the reduction of [11]+ with Co(C5Me 5)2. Complexes [11]+ can also be oxidized with [Cp2-Fe] [PF6] to produce the dicationic Mn(III)/Mn(III) species [{Mn(dmpe)2(C≡CR3)}2(μ-C 4)] [PF6]2 (R = SiEt3, [11a] 2+; R = SiiPr3, [11b]2+; R = Si(tBu)Me2, [11c]2+). Both redox processes are fully reversible. The dinuclear compounds have been characterized by NMR, IR, and Raman spectroscopy, cyclic voltammetry, and elemental analyses. X-ray diffraction studies have also been performed on several complexes.

Original languageEnglish
Pages (from-to)2834-2847
Number of pages14
JournalOrganometallics
Volume24
Issue number12
DOIs
Publication statusPublished - 6 Jun 2005
Externally publishedYes

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