Issue 9, 2017

Triple bonds of niobium with silicon, germaniun and tin: the tetrylidyne complexes [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]E–R] (E = Si, Ge, Sn; tmps = MeSi(CH2PMe2)3; R = aryl)

Abstract

A systematic, efficient approach to first complexes containing a triple bond between niobium and the elements silicon, germanium or tin is reported. The approach involves a metathetical exchange of the niobium-centered nucleophile (NMe4)[Nb(CO)42-tmps)] (1) (tmps = MeSi(CH2PMe2)3) with a suitable organotetrel(II)halide. Compound 1 was obtained from (NMe4)[Nb(CO)6] and the triphosphane tmps by photodecarbonylation. Reaction of 1 with the disilene E-Tbb(Br)Si[double bond, length as m-dash]Si(Br)Tbb in the presence of 4-dimethylaminopyridine afforded selectively the red-brown silylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Si–Tbb] (2-Si, Tbb = 4-tert-butyl-2,6-bis(bis(trimethylsilyl)methyl)phenyl). Similarly, treatment of 1 with E(ArMes)Cl (E = Ge, Sn; ArMes = 2,6-mesitylphenyl) afforded after elimination of (NMe4)Cl and two CO ligands the deep magenta colored germylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Ge–ArMes] (3-Ge), and the deep violet, light-sensitive stannylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Sn–ArMes] (3-Sn), respectively. Formation of 3-Sn proceeds via the niobiastannylene [(κ3-tmps)(CO)3Nb–SnArMes] (4-Sn), which was detected by IR and NMR spectroscopy. The niobium tetrylidyne complexes 2-Si, 3-Ge and 3-Sn were fully characterized and their solid-state structures determined by single-crystal X-ray diffraction studies. All complexes feature an almost linear tetrel coordination and the shortest Nb–E bond lengths (d(Nb–Si) = 232.7(2) pm; d(Nb–Ge) = 235.79(4) pm; d(Nb–Sn) = 253.3(1) pm) reported to date. Reaction of 3-Ge with a large excess of H2O afforded upon cleavage of the Nb–Ge triple bond the hydridogermanediol Ge(ArMes)H(OH)2. Photodecarbonylation of [CpNb(CO)4] (Cp = η5-C5H5) in the presence of Ge(ArMes)Cl afforded the red-orange chlorogermylidene complex [Cp(CO)3Nb[double bond, length as m-dash]Ge(ArMes)Cl] (5-Ge). The molecular structure of 5-Ge features an upright conformation of the germylidene ligand, a trigonal–planar coordinated Ge atom, and a Nb–Ge double bond length of 251.78(6) pm, which lies in-between the Nb–Ge triple bond length of 3-Ge (235.79(4) pm) and a Nb–Ge single bond length (267.3 pm). Cyclic voltammetric studies of 2-Si, 3-Ge, and 3-Sn reveal several electron-transfer steps. One-electron oxidation and reduction of the germylidyne complex of 3-Ge in THF are electrochemically reversible suggesting that both the radical cation and radical anion of 3-Ge are accessible species in solution.

Graphical abstract: Triple bonds of niobium with silicon, germaniun and tin: the tetrylidyne complexes [(κ3-tmps)(CO)2Nb [[triple bond, length as m-dash]] E–R] (E = Si, Ge, Sn; tmps = MeSi(CH2PMe2)3; R = aryl)

Supplementary files

Article information

Article type
Edge Article
Submitted
18 Jun 2017
Accepted
02 Jul 2017
First published
14 Jul 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2017,8, 6290-6299

Triple bonds of niobium with silicon, germaniun and tin: the tetrylidyne complexes [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]E–R] (E = Si, Ge, Sn; tmps = MeSi(CH2PMe2)3; R = aryl)

A. C. Filippou, D. Hoffmann and G. Schnakenburg, Chem. Sci., 2017, 8, 6290 DOI: 10.1039/C7SC02708G

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