No abstract

Packing them in: Based on zinc and aromatic‐rich dicarboxylic acids these new coordination networks (see structure; green Cl, red O, yellow Zn, blue N, gray C) have hydrogen uptakes comparable to those of the best carbon nanotubes and metal–organic frameworks. The highly interpenetrating nature of these networks points to a new design strategy for hydrogen‐storage materials that employ an entrapment mechanism.

[Sn(9)Pt(2)(PPh(3))](2)(-) (2) was prepared from Pt(PPh(3))(4), K(4)Sn(9), and 2,2,2-cryptand in en/toluene solvent mixtures. The [K(2,2,2-cryptand)](+) salt is very air and moisture sensitive and has been characterized by ESI-MS, variable-temperature (119)Sn, (31)P, and (195)Pt NMR and single-crystal X-ray diffraction studies. The structure of 2 comprises an elongated tricapped Sn(9) trigonal prism with a capping PtPPh(3), an interstitial Pt atom, a hypercloso electron count (10 vertex, 20 electron) and C(3)(v)() point symmetry. Hydrogenation trapping experiments and deuterium labeling studies showed that the formation of 2 involves a double C-H activation of solvent molecules (en or DMSO) with the elimination of H(2) gas. The ESI-MS analysis of 2 showed the K[Sn(9)Pt(2)(PPh(3))](1)(-) parent ion, an oxidized [Sn(9)Pt(2)(PPh(3))](1)(-) ion, and the protonated binary cluster anion [HSn(9)Pt(2)](1)(-). 2 is highly fluxional in solution giving rise to a single time-averaged (119)Sn NMR signal for all nine Sn atoms but the Pt atoms remain distinct. The exchange is intramolecular and is consistent with a rigid, linear Pt-Pt-PPh(3) rod embedded in a liquidlike Sn(9) matrix. [Sn(9)Ni(2)(CO)](3)(-) (3) was prepared from Ni(CO)(2)(PPh(3))(2), K(4)Sn(9), and 2,2,2-cryptand in en/toluene solvent mixtures. The [K(2,2,2-cryptand)](+) salt is very air and moisture sensitive, is paramagnetic, and has been characterized by ESI-MS, EPR, and single-crystal X-ray diffraction. Complex 3 is a 10-vertex 21-electron polyhedron, a slightly distorted closo-Sn(9)Ni cluster with an additional interstitial Ni atom and overall C(4)(v)() point symmetry. The EPR spectrum showed a five-line pattern due to 4.8-G hyperfine interactions involving all nine tin atoms. The ESI-MS analysis showed weak signals for the potassium complex [K(2)Sn(9)Ni(2)(CO)](1-) and the ligand-free binary ions [K(2)Sn(9)Ni(2)](1)(-), [KSn(9)Ni(2)](1)(-), and [HSn(9)Ni(2)](1)(-).

Sn94- reacts with Pt(PPh3)4 in ethylenediamine/toluene solvent mixtures in the presence of 2,2,2-cryptand to give four different complexes: "Rudolph's complex" of proposed formula [Sn9Pt(PPh3)x]4- (2), the previously reported [Pt@Sn9Pt(PPh3)]2- ion (3), and the title complexes Pt2@Sn174- (4) and Pt@Sn9H3- (5). The use of Pt(norbornene)3 instead of Pt(PPh3)4 gives complex 4 exclusively. The structure of 4 contains two Pt atoms centered in a capsule-shaped Sn17 cage. The complex is highly dynamic in solution showing single, mutually coupled 119Sn and 195Pt NMR resonances indicative of an intramolecular liquidlike dynamic exchange process. Complex 5 has been characterized by selectively decoupled 1H, 119Sn, and 195Pt NMR experiments and shows similar liquidlike fluxionality. In addition, the H atom scrambles across the cage showing small couplings to both Sn and Pt atoms. Neither 3 nor 4 obeys Wades rules; they adopt structures more akin to the subunits in alloys such as PtSn4. The structural and chemical relevance to supported PtSn4 heterogeneous catalysts is discussed.

The closo-[Sn9M(CO)3]4-ions where M = Cr (1), Mo (2), W (3) were prepared from [LM(CO)3] precursors (L=mesitylene, cycloheptatriene), K4Sn9. and 2,2,2-cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2-cryptand)]+ salts are very air and moisture sensitive and have been characterized by IR, 119Sn, and 13C NMR spectroscopy and single-crystal X-ray diffraction studies. Complexes 1-3 form bicapped square-antiprismatic 10-vertex 22-electron closo structures in which the [M(CO)3] units occupy cluster vertices. For 1 and 2, the clusters have C4. symmetry in the solid state in which the [M(CO)A] fragments occupy capping positions with Sn9(4-) ions that are bound to the metal in an 4 fashion. For 3, the [M(CO)3] fragment occupies a position in the square plane with an eta/5-Sn9(4-) ion and C(s) point symmetry. For 1-3, a dynamic equilibrium exists between the eta4 and eta5 structures yielding three 119Sn NMR signals that reflect the three chemically distinct Sn environments of the higher symmetry C(4v) structure. The 119Sn NMR chemical shifts and coupling constants show solvent and temperature dependencies due to the equilibrium process. A triangular-face rotation mechanism is proposed to describe the dynamic behavior.

Ethylenediamine (en) solutions of E7 3- (E = P, As) react with Pt(PPh3)2(C2H4) in the presence of 4,7,13,16,21,24-hexaoxa-1,10-diazobicyclo[8.8.8]hexacosane (2,2,2-crypt) to give the transition-metal Zintl ion complexes [P7PtH(PPh3)]2- (1) and [As7PtH(PPh3)]2- (2) as isomorphic [K(2,2,2-crypt)]+ salts, respectively. The hydride ligand originates from the solvent, and deuterium labeling studies show that the order of hydrogen sources follows the sequence en > CH3CN > DMSO > DMF in the synthesis of 1. The [E7PtH(PPh3)]2- anions have C 1 point symmetry with unperturbed nortricyclane-like E7 3- ligands bound η2 to square planar PtIIH(PPh3)+ centers. Complex 1 is dynamic in solution whereby the PtH(PPh3)+ fragment shifts from the top to bottom of the P7 cluster (an η2 → η4 → η2 shift) and spins in the P4 face in a concerted process to give apparent C 2 v symmetry. We have shown that 31P EXSY NMR experiments at −78 °C permit the separation of the two processes and show that shifting is ∼20 times faster than spinning (k shift = 160 s-1, k spin = 8 s-1).

Eingepackt: Die hier vorgestellten Koordinationsnetzwerke auf der Basis von Zink und Aren‐reichen Dicarbonsäuren (siehe Struktur; grau C, rot O, blau N, grün Cl, gelb Zn) ähneln in ihrer Wasserstoffaufnahme den besten Kohlenstoffnanoröhren und metall‐organischen Gerüsten. Ihre ausgeprägten Durchdringungsstrukturen könnten Anregung für eine neue Strategie für das Design von Wasserstoffspeichermaterialien sein, die einen Fallenmechanismus nutzen.

Recyclable and reusable mesoporous silica anchored Ru catalysts based on 4,4'-substituted BINAPs were synthesized and used for the hydrogenation of beta-alkyl beta-ketoesters with up to 98.6% e.e. and beta-aryl beta-ketoesters with up to 95.2% e.e.