Structural and Spectroscopic Characterization of Tin–Tin Double Bonds in Cyclic Distannenes

Abstract

Three cyclic distannenes, 1, 3, and 4, and one spacer-bridged bis(stannylene), 2, were prepared and thoroughly investigated by single-crystal X-ray diffraction in the solid state, by variable-temperature (VT) 119 Sn NMR, VT 1 H NMR, 13 C NMR, and UV−vis spectroscopy in solution, and by quantum chemical calculations. The tin(II) compounds feature rigid 9,9-dimethylxanthene or naphthalene backbones and very bulky m-terphenyl substituents Ar R [=C 6 H 3 -2,6-{C 6 H 2 -2,4,6-R 3 } 2 ; R = Me (1, 3), i-Pr (2, 4)]. For distannenes 3 and 4, the strain of the naphthalene backbone results in rather short tin−tin distances of 2.7299(3) and 2.7688(2) Å, respectively, whereas the xanthene backbone produces long tin−tin distances of 3.0009(7) Å for distannene 1 and 4.2779(7) Å for the spacer-bridged bis(stannylene) 2. In comparison to the Ar iPr substituents, the less bulky Ar Me substituents give rise to stronger trans-bending of the distannenes; moreover, DFT calculations indicate that, in contrast to Ar iPr , the Ar Me substituents allow for asymmetric distortion of the trans-bending in dynamic processes. The oxidation products of distannene 1 and bis(stannylene) 2 reveal rare structural motifs: dihydroxydistannoxane 5 and bis(dihydroxystannane) 6, respectively, which feature terminal Sn−OH functionalities. The reaction of distannene 1 with 1 equiv of potassium chloride in the presence of the cryptating agent 222 results in the formation of the unusual stannyl stannide 7. A modified synthesis protocol for the preparation of distannene 1 yields in one step the stannyl stannylene 8 with a center of chirality at the stannyl tin atom. The series 1, 7, and 8 represents a variation of electronic tin−tin interactions.

Monoanionic Tin Oligomers Featuring Sn–Sn or Sn–Pb Bonds: Synthesis and Characterization of a Tris(Triheteroarylstannyl)Stannate and -Plumbate

“…870 ppm compared to the three-coordinate tin(II) atom in 1 (δ = −191 ppm). The 207 Pb NMR spectrum of 3 is Sn ( The 119 Sn-119/117 Sn coupling constant in compound 2 is 7050 Hz, and may be compared with scalar coupling constants found for stannylstannylene species (6240-9400 Hz) [20,[27][28][29][30][31]. The chemical shift of the bridging tin atom in 2 appears at´1064 ppm.…”

“…The Pb-Sn bond lengths amount to 2.8743(3) and 2.8919(4) Å, and may be compared with 2.7844(4) Å in Pb(Ar)SnAr3 (Ar = C6H3-2,6-(O i Pr)2) and 2.9283(4) Å in Pb(SnAr3)2 [26]. [20,[27][28][29][30][31]. The chemical shift of the bridging tin atom in 2 appears at −1064 ppm.…”

Nickel‐Triad Complexes of a Side‐on Coordinating Distannene

“…Whilst Pt complex 2 and 3 reveal comparable constants for nickel complex 4 , an unexpectedly large coupling constant of J Sn–Sn =8050 Hz was found. Such large constants are known for rather different species such as (R 3 Sn) 2 Sn or strained cyclic distannenes 5e. 15…”

Synthesis of HeavyN‐Heterocyclic Tetrylenes: Influence of Ligand Sterics on Structure

“…The UV‐Vis spectra of 1 t Bu ‐Sn , 2 Ph ‐Sn , 3 Dmp ‐Sn and 4 Dipp ‐Sn exhibits absorptions between 351–319 nm (Table 3), slightly higher in energy to other reported diamido stannylene complexes [3b] . Distannenes typically absorb at significantly longer wavelengths than monomeric stannylenes [18] . Together, these data imply that all of the tin complexes reported here are monomeric in solution.…”