Structure of tetraaquacobalt(II) bromide dihydrate (cobalt bromide hexahydrate)

Abstract

Tetraaquacobalt(II) bromide dihydrate, [Co(H2O)4]Br2 x 2H2O, Mr = 326.83, monoclinic, C2/m, a = 11.0158(12), b = 7.1694(10), c = 6.9111(10) A, beta = 124.761(7)degrees, V = 448.4(1) A3, Z = 2, F(000) = 314, Dx = 2.420 g cm-3, lambda(Mo K alpha) = 0.71069 A, T = 296 K, mu = 107.13 cm-1, R = 0.022 for 532 unique reflections having I greater than 0. The single type of Co ion is octahedrally coordinated by four equivalent water-molecule O atoms at the observed distance 2.081(2) A and two equivalent Br ions at the observed distance 2.6048(5) A in an array which, with respect to its angles, departs only slightly from regular octahedral geometry. The cobalt-oxygen-bromine complex was found to manifest rigid-body behavior. The cobalt-oxygen distance corrected for rigid-body motion was found to be 2.088 A; the corrected cobalt-bromine distance, 2.6081 A. Associated with each complex are two water molecules of hydration. Assignment and refinement of the coordinates of the four non-equivalent H atoms permitted detailed analysis of the hydrogen bonding, which involves each of the four non-equivalent H atoms significantly. The structure as determined in this study differs markedly from that presented in the sole published single-crystal study [Stroganov, Andreev, Kozina & Solov'ev (1961). Vestn. Leningr. Univ. Ser. Mat. Fiz. Khim. 16, 114-119]. In particular, the space-group assignment differs and the pattern of bromine-oxygen distances is quite different. Contrary to Stroganov et al., this structure is isomorphic with that of cobalt chloride hexahydrate.

C–S Bond Cleavage, Redox Reactions, and Dioxygen Activation by Nonheme Dicobalt(II) Complexes

“…The Co II –SH distances of 2.318(3) ( 8a ) and 2.232 (3) Å ( 8b ) are comparable with Co–SH distance of 2.2398(13) Å reported for a mononuclear Co­(II) complex containing terminal SH, namely, [Co­(C 9 H 7 N) 2 (SH) 2 ], and Co–SH bond distances of 2.292–2.303 Å ([{Co­(μ-SH)­(cyclam)} 2 ]­[SH] 2 and 2.343(8)–2.383(8) Å ([Co 3 (μ 3 -S) 2 (μ-SH) 2 (μ-PEt 2 )­(PHEt 2 ) 6 ]) reported for complexes containing bridging HS – . The Co II –OH 2 distances of 2.029(5) and 2.024(5) Å in 8a and 8b are also comparable with previously reported Co II –OH 2 bond distances of 2.073(2), 2.072(1), 2.081(2), and 2.095 (2) Å . The terminal −SH and H 2 O are engaged in hydrogen bonding (Figure ) to make a H–S–H–O–H bridge similar to the few known H–O–H–O–H bridges in aquo-hydroxy bridged complexes, − and the corresponding HS···HOH distances are 1.953(3) ( 8a ) and 1.893(2) Å ( 8b ).…”

“…Co 3 (μ 3 -S) 2 (μ-SH) 2 (μ-PEt 2 )(PHEt 2 ) 6 ])84 reported for complexes containing bridging HS − . The Co II − OH 2 distances of 2.029(5) and 2.024(5) Å in 8a and 8b are also comparable with previously reported Co II −OH 2 bond distances of 2.073(2),85 2.072(1),86 2.081(2),87 and 2.095 (2) Å 88. The terminal −SH and H 2 O are engaged in hydrogen Figure2).…”

Speciation and thermodynamic properties for cobalt chloride complexes in hydrothermal fluids at 35–440°C and 600bar: An in-situ XAS study

“…The other models tested (CoO 6 , CoBr 2 O 4 and CoBr 3 O 3 ) resulted in significantly poorer fits. The octahedral Co-Br distance of 2.55(4) Å is similar to published values of octahedral Co-Br bond lengths (2.61 Å in CoBr 2 Á6H 2 O (s) , Blackburn et al, 1991;2.577 and 2.587 Å in 2.806 and 4.251 M solutions of CoBr 2(aq) , Ichihashi et al, 1984).…”

Hexacyano octahedral metallic clusters as versatile building blocks in the design of extended polymeric framework and clustomesogens

“…Note that, the splitting of the O 2 oxygen of the second water molecule coordinated to Cd 2+ on two close positions is easily explained by the weakness of the hydrogen bonding between this water molecules and Br3 that is larger by 0.2 Å than those reported in some related hydrated cadmium or cobalt bromide complexes. 33…”