Wednesday, March 22, 2006

Chemistry - A European JournalVolume 12, Issue 8, Pages 2139-2146

Comment: Similar to my silver project

Title: Orientational Control of Guest Molecules in an Organic Intercalation System by Host Polymer Tacticity
Shinya Oshita, Akikazu Matsumoto, Prof.


Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n-alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals.

Chemistry - A European JournalVolume 12, Issue 4, Pages 1036-1045

Comment: Sn-119 NMR

Ruthenium Complexes with the Stanna-closo-dodecaborate Ligand: Coexistence of 1(Sn) and 3(BH) Coordination
Torben G├Ądt , Beatrice Grau , Klaus Eichele , Ingo Pantenburg , Lars Wesemann, Prof. Dr.

Four stanna-closo-dodecaborate complexes of ruthenium have been prepared and characterized by multinuclear NMR studies in solution and in the solid state. The solid-state structures of the dimeric zwitterions [{Ru(dppb)(SnB11H11)}2] (2) (dppb=bis(diphenylphosphino)butane), [{Ru(PPh3)2(SnB11H11)}2] (3), and the dianionic ruthenium complex [Bu3MeN]2[Ru(dppb){2,7,8-(-H)3-exo-SnB11H11}(SnB11H11)] (4) were determined by X-ray crystal structure analysis; they establish an unprecedented structural motif in the chemistry of heteroboranes and transition-metal fragments with the stanna-closo-dodecaborate moiety as a two-faced ligand that exhibits 1(Sn) as well as 3(BH) coordination. The 3-coordinated stannaborate in 4 and in the isostructural compound [Bu3MeN]2[Ru(PPh3)2{2,7,8-(-H)3-exo-SnB11H11}(SnB11H11)] (5) shows fluxional behavior, which was studied in detail by using 31P{1H} EXSY and DNMR experiments. The activation parameters for the dynamic process of 5 are given.

Chemistry - A European JournalVolume 12, Issue 7, Pages 1997-2008
Comment: p-31 NMR

Title: Silver Complexes of Cyclic Hexachlorotriphosphazene Marcin Gonsior, Dr., Sasa Antonijevic, Dr., Ingo Krossing, Prof.


The first solid-state structures of complexed P3N3X6 (X=halogen) are reported for X=Cl. The compounds were obtained from P3N3Cl6 and Ag[Al(OR)4] salts in CH2Cl2/CS2 solution. The very weakly coordinating anion with R=C(CF3)3 led to the salt Ag(P3N3Cl6)2+[Al(OR)4]- (1), but the more strongly coordinating anion with R=C(CH3)(CF3)2 gave the molecular adduct (P3N3Cl6)AgAl(OR)4 (3). Crystals of [Ag(CH2Cl2)(P3N3Cl6)2]+[Al(OR)4]- (2), in which Ag+ is coordinated by two phosphazene and one CH2Cl2 ligands, were isolated from CH2Cl2 solution. The three compounds were characterized by their X-ray structures, and 1 and 3 also by NMR and vibrational spectroscopy. Solution and solid-state 31P NMR investigations in combination with quantum chemically calculated chemical shifts show that the 31P NMR shifts of free and silver-coordinated P3N3Cl6 differ by less than 3 ppm and indicate a very weakly bound P3N3Cl6 ligand in 1. The experimental silver ion affinity (SIA) of the phosphazene ligand was derived from the solid-state structure of 3. The SIA shows that (PNCl2)3 is only a slightly stronger Lewis base than P4 and CH2Cl2, while other ligands such as S8, P4S3, toluene, and 1,2-Cl2C2H4 are far stronger ligands towards the silver cation. The energetics of the complexes were assessed with inclusion of entropic, thermal, and solvation contributions (MP2/TZVPP, COSMO). The formation of the cations in 1, 2, and 3 was calculated to be exergonic by rG°(CH2Cl2)=-97, -107, and -27 kJ mol-1, respectively. All prepared complexes are thermally stable; formation of P3N3Cl5+ and AgCl was not observed, even at 60 °C in an ultrasonic bath. Therefore, the formation of P3N3Cl5+ was investigated by quantum chemical calculations. Other possible reaction pathways that could lead to the successful preparation of P3N3X5+ salts were defined.

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