Zwei Dodekahydro‐closo‐Dodekaborate mit Lone‐Pair‐Kationen der 6. Periode im Vergleich: Tl₂[B₁₂H₁₂] und Pb(H₂O)₃[B₁₂H₁₂]·3H₂O

Abstract

Ioannis Tiritiris, [a] Nguyen-Duc Van [a] und Thomas Schleid* [a]Professor Peter Paetzold zum 75. Geburtstag gewidmet Abstract. During the reaction of an aqueous solution of (H 3 O) 2 [B 12 H 12 ] with Tl 2 CO 3 anhydrous thallium(I) dodecahydrocloso-dodecaborate Tl 2 [B 12 H 12 ] is obtained as colorless, spherical single crystals. It crystallizes in the cubic system with the centrosymmetric space group Fm3 (a = 1074.23 (8) pm, Z = 4) in an anti-CaF 2 type structure. Four quasi-icosahedral [B 12 H 12 ] 2anions (d(B-B) = 180-181 pm, d(B-H) = 111 pm) exhibit coordinative influence on each Tl + cation and provide a twelvefold coordination in the shape of a cuboctahedron (d(Tl-H) = 296 pm). There is no observable stereochemical activity of the non-bonding electron pairs (6s 2 lone pairs) at the Tl + cations. By neutralization of an aqueous solution of the acid (H 3 O) 2 [B 12 H 12 ] with PbCO 3 and after isothermic evaporation colorless, plate-like single crystals of lead(II) dodecahydro-closo-dodecaborate hexahydrate Pb(H 2 O) 3 [B 12 H 12 ]·3H 2 O can be isolated. This compound crystallizes orthorhombically with the non-centrosymmetric space EinleitungDie röntgenstrukturanalytisch mittlerweile gut untersuchten Dodekahydro-closo-Dodekaborate mit Erdalkalimetall-Dikationen (M = Mg-Ba), [1,2] aber auch mit verschiedenen zweiwertigen Übergangsmetallen (z. B. M = Cu, Zn, Cd, Co, Ni und Mn), [3][4][5][6] kristallisieren aus wässriger Lösung gewöhnlich als Hydrate, jedoch mit sehr unterschiedlichem Kristallwassergehalt. Dabei wurde festgestellt, dass sich die [B 12 H 12 ] 2--Anionen meist als "outer-sphere"-Liganden verhalten und somit nicht an die zweiwertigen Metallkationen M 2+ koordinieren. Einzig in der Kristallstruktur von Ba(H 2 O) 6 [B 12 H 12 ] (Raumgruppe: Cmcm) [2] wird den Ba 2+ -Kationen eine gemischte Koordinationssphäre aus sechs Sauerstoffatomen von Wassermolekülen und sechs Wasserstoffatomen von closo-Dodekaborat-

Bismuth Undecahydro‐closo‐dodecaborane: A Retainable Intermediate of B−H Bond Activation by Bismuth(III) Cations

“…[5] In the case of the thallium salt Tl 2 [B 12 H 12 ], which crystallizes isotypically to the alkali-metal salts A 2 [B 12 H 12 ] (A = K-Cs), [6] the bond between the Tl + cations and the negatively polarized hydrogen atoms was deduced to have significant covalent character based on the red shift of the thallium luminescence. [7] Thec rystal structures of other cations containing a6s 2 [8,9] If one assumes that the formation of these interactions (which can also be interpreted as the coordination of B À Hb onds by metal cations) is the first step in B À H bond activation, these salts represent precursors for the synthesis of metalated boron clusters. [10] Consistent with this hypothesis,w ed iscovered that the thermal dehydration of the basic salt [Bi 6 Figure 1), which can be isolated in the form of three different crystalline solvates (1·6 H 2 O, 1·3 H 2 O, and 1·4 CH 3 OH).…”

“…In the case of the thallium salt Tl 2 [B 12 H 12 ], which crystallizes isotypically to the alkali‐metal salts A 2 [B 12 H 12 ] (A=K–Cs), the bond between the Tl + cations and the negatively polarized hydrogen atoms was deduced to have significant covalent character based on the red shift of the thallium luminescence . The crystal structures of other cations containing a 6 s 2 lone pair, for example, [Pb(H 2 O) 3 ][B 12 H 12 ]⋅3 H 2 O and [Bi 6 O 4 (OH) 4 ][B 12 H 12 ] 3 ⋅10 H 2 O, also display close contacts between the hydrogen atoms and metal cations . If one assumes that the formation of these interactions (which can also be interpreted as the coordination of B−H bonds by metal cations) is the first step in B−H bond activation, these salts represent precursors for the synthesis of metalated boron clusters…”

Bismut‐Undekahydro‐closo‐Dodekaboran: ein abfangbares Zwischenprodukt der B‐H‐Bindungsaktivierung durch Bismut(III)‐Kationen

“…Für das isotyp zu den Alkalimetallsalzen A 2 [B 12 H 12 ] (A=K–Cs) kristallisierende Thalliumsalz Tl 2 [B 12 H 12 ] wurde ein signifikanter kovalenter Bindungsanteil zwischen den Tl + ‐Kationen und den negativ polarisierten Wasserstoffatomen durch die Rotverschiebung der metallzentrierten Thalliumlumineszenz nachgewiesen . Auch für andere Salze von Kationen mit einem freien 6 s 2 ‐Elektronenpaar wie [Pb(H 2 O) 3 ][B 12 H 12 ]⋅3 H 2 O und [Bi 6 O 4 (OH) 4 ][B 12 H 12 ] 3 ⋅10 H 2 O wurden enge Kontakte zwischen den Wasserstoffatomen und den Kationen gefunden …”

Synthesis and X‐ray Crystallography of Two Lead(II) Decahydro‐closo‐Decaborate Hydrates

“…In view of the fact that this reaction only seems to work with the [B 12 H 12 ] 2– and not with the lower homologous [B 10 H 10 ] 2– anion, presumably caused by the minor stability and higher reactivity of this closo ‐decaborate, we set focus on other cations of the 6 th row of the periodic table of the elements, which possess lone‐pair electrons. For these a connection between the [B 10 H 10 ] 2– anions and the metal cations is expected, according to the dodecahydro‐ closo ‐dodecaborates of monovalent thallium and divalent lead, maybe even resulting in a strong B–H bond activation as in the Bi 3+ /[B 12 H 11 ] 2– case. But even if not, these compounds provide other interesting properties.…”

“…Tl 2 [B 12 H 12 ], for example, shows a metal‐centered luminescence ( λ max = 530 nm) at room temperature, which indicates an interaction between the thallium and the cluster ions through the hydridic hydrogen atoms . In this thallium(I) salt, the lone‐pair electrons behave like a 6s 2 pair, since Tl 2 [B 12 H 12 ] (cubic, space group, Fm 3, a = 1074.23(8) pm) crystallizes isotypically with the heavy alkali‐metal salts A 2 [B 12 H 12 ] ( A = K – Cs) . The lead(II) compound Pb(H 2 O) 3 [B 12 H 12 ] · 3H 2 O, however, crystallizing orthorhombically in the space group Pna 2 1 ( a = 1839.08(9), b = 1166.52(6), c = 717.27(4) pm, Z = 4), exhibits lone‐pair electrons at the Pb 2+ cations that develop stereochemically active with an increased p‐character of the respective orbital .…”