Linearly Two-Coordinated Silicon: Transition Metal Complexes with the Functional Groups M≡Si - M and M=Si=M

Priyabrata Ghana, Marius I. Arz, Uttam Chakraborty, Gregor Schnakenburg, Alexander C. Filippou*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

26 Citations (Scopus)


A detailed experimental and theoretical analysis is presented of unprecedented molybdenum complexes featuring a linearly coordinated, multiply bonded silicon atom. Reaction of SiBr2(SIdipp) (SIdipp = C[N(C6H3-2,6-iPr2)CH2]2) with Na[Tp′Mo(CO)2(PMe3)] (Na-1) in the ratio 1:2 afforded the reddish-brown metallasilylidyne complex [Tp′(CO)2Mo≡Si - Mo(CO)2(PMe3)Tp′] (Tp′ = κ3-N,N′,N″-hydridotris(3,5-dimethylpyrazolyl)borate) (2), in which an almost linearly coordinated silicon atom (<(Mo1-Si-Mo2) = 162.93(7)°) is bridging the 15VE metal fragment Tp′Mo(CO)2 with the 17VE metal fragment Tp′Mo(CO)2(PMe3) via a short Mo1-Si bond (2.287(2) Å) and a considerably longer Mo2-Si bond (2.438(2) Å), respectively. The reddish-orange silylidyne complex [Tp′(CO)2Mo≡Si - Tbb] (3) was also prepared from Na-1 and the 1,2-dibromodisilene (E)-Tbb(Br)Si=Si(Br)Tbb (Tbb = C6H2-2,6-[CH(SiMe3)2]2-4-tBu) and contains as 2 a short Mo-Si bond (2.2614(9) Å) to an almost linearly coordinated Si atom (< (Mo-Si-CTbb) = 160.8(1)°). Cyclic voltammetric studies of 2 in diglyme revealed an irreversible reduction of 2 at -1.907 V vs the [Fe(η5-C5Me5)2]+/0 redox couple. Two-electron reduction of 2 with potassium graphite yielded selectively the 1,3-dimetalla-2-silaallene dianion [Tp′(CO)2Mo=Si=Mo(CO)2Tp′]2- (42-), which was isolated as the bright yellow dipotassium salt [K(diglyme)]2-4. Single crystal X-ray diffraction analysis revealed a centrosymmetric structure of 42-. The Mo-Si bond length of 42- (2.3494(2) Å) compares well with those of Mo-Si double bonds and lies in-between the Mo1-Si triple bond and Mo2-Si single bond length of 2. Compounds 2, 3 and [K(diglyme)2]-4 were characterized by elemental analyses, IR and multinuclear NMR spectroscopy. Comparative ELF (electron localization function), NBO (natural bond orbital) and NRT (natural resonance theory) analyses of 2, 3 and 42- shed light into the electronic structures of these compounds.

Original languageEnglish
Pages (from-to)7187-7198
Number of pages12
JournalJournal of the American Chemical Society
Issue number23
Publication statusPublished - 13 Jun 2018


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