Spirocyclic Sulfur and Selenium Ligands as Molecular Rigid Rods in Coordination of Transition Metal Centers

Abstract

A set of analogous chalcogen-containing spirocycles, 2,6-dithiaspiro[3.3]heptane, 2,6-diselenaspiro[3.3]heptane, and 2-thia-6-selenaspiro[3.3]heptane [E(2)C(5)H(8), E = S (1), Se (2), and S/Se (3)], has been prepared and fully characterized by spectroscopic methods and by X-ray diffraction. The structural characterization of 2 was presented by us earlier, while the crystal structures of 1 and 3 are reported here for the first time. Molecules 1-3 are built around the central tetrahedral carbon atom and therefore are nonplanar. The E...E separation ranges from 4.690(1) A in 1 to 4.906(1) A in 2. Molecule 3 has statistically mixed positions of sulfur and selenium atoms in the solid state with all geometric characteristics being intermediate between those of 1 and 2. Compounds 2 and 3 have been tested as molecular rigid rod ligands in coordination reactions with transition metal complexes such as Cu(hfac)(2) (4), cis-Co(hfac)(2).2H(2)O (5), and cis-Ni(hfac)(2).2H(2)O (6) (hfac = hexafluoroacetylacetonate). Several coordination products built of two building blocks, M(hfac)(2) (M = Cu, Co, and Ni) and Se(2)C(5)H(8) (2), have been prepared in crystalline form and structurally characterized. The copper-based product (7) is comprised of the oligomeric units {[Cu(hfac)(2)](3).2mu(2)-Se(2)C(5)H(8)-Se,Se'} built on the axial Cu...Se interactions averaged at 2.909 A. These units are further assembled into 1D polymeric chains via intermolecular Cu...F contacts at 2.829 A. The SSeC(5)H(8) (3) ligand was also used in the reaction with Cu(hfac)(2) to afford an analogue of 7, namely {[Cu(hfac)(2)](3).2mu(2)-SSeC(5)H(8)-S,Se} (8). Complex 8 exhibits statistically mixed positions of the donor sulfur and selenium atoms to give an average axial Cu...S/Se contact at 2.892 A. In contrast to the copper complexes of composition 3:2, the stoichiometries of the isolated cobalt and nickel products are 1:1, [M(hfac)(2).Se(2)C(5)H(8)] (M = Co (9) and Ni (10)). Complexes 9 and 10 exhibit 1D polymer structures having alternating metal units cis-M(hfac)(2) and ligands 2 with intermolecuar M...Se separations of 2.6046(8) and 2.5523(16) A, respectively. In all products 7-10 the initial cis or trans geometry of M(hfac)(2) complexes is preserved and the spiro[3.3]heptane ligands act as bidentate linkers bridging transition metal centers via both donor ends. The magnetic properties of this series of new Cu(II), Co(II), and Ni(II) complexes have been tested by variable-temperature magnetic susceptibility measurements.

Synthesis, structure, and chemistry of selenium-containing four-membered rings

“…Heterocycle 3 was synthesized from 1,3-dibromo-2,2-bis(bromomethyl)propane, 6, (Scheme 1) by replacement of one of the bromines with thioacetate, treatment with base to give 3,3-bis(bromomethyl)thietane, 7, and conversion of 7 to 3 by Li 2 Se (from Se and LiEt 3 BH) in THF [12,13]. Heterocycle 4 was prepared as described previously [11].…”

“…Selected data for 3, 4, and 5 (all colorless solids) are given: 3, m.p. 45 °C, 1 H NMR δ 3.16 (s, 4H), 3.18 (s, 4H), 13 C NMR δ 27.3, 41.1, 53.3; 4, m.p. 31 °C, 1 H NMR δ 3.26 (s), 13 C NMR δ 39.8, 52.2; 5, m.p.…”

“…45 °C, 1 H NMR δ 3.16 (s, 4H), 3.18 (s, 4H), 13 C NMR δ 27.3, 41.1, 53.3; 4, m.p. 31 °C, 1 H NMR δ 3.26 (s), 13 C NMR δ 39.8, 52.2; 5, m.p. 68 °C, 1 H NMR δ 3.14 (s), 13 C NMR δ 28.7, 54.4.…”

trans-Diaquabis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2 O,O′)cobalt(II) dihydrate

“…An isomer of the molecular entity cis-[Co(hfac) 2 (H 2 O) 2 ] (Petrukhina et al, 2005) was now obtained as a dihydrate with a trans-configuration about the Co II atom, representing the title compound [Co(hfac) 2 (H 2 O) 2 ]Á2H 2 O (Fig. 1).…”

“…A search of the Cambridge Structural Database (Groom et al, 2016) (Adams et al, 1986), Mn (Dickman et al, 1997), and Cu (Maverick et al, 2002)], of which the Zn and Mn compounds are isotypic with each other, the solvate water molecule forms hydrogen bonds with two of the four oxygen atoms of the hfac À ligands in the complex, whereas the other two oxygen atoms form hydrogen bonds with the aqua ligands of an adjacent complex. In contrast, cis-[M(hfac) 2 (H 2 O) 2 ] [M = Co (Petrukhina et al, 2005), Zn (Adams & Allen, 1986), Ni (Romero et al, 1992) and Mn (Troyanov et al, 1999) …”