Eric Siebel

Unprecedented N–E Bond Cleavage (E=Sn, Pb) by R4N+ Ions (R=nBu, nPr): Formation, Architecture, and Multinuclear Magnetic Resonance Spectroscopy of Novel Supramolecular [(R4N)(Me3E)2M(CN)6⋅H2O] Assemblies (M=Fe, Co)

Hydrogen bonds of the two types O−H⋅⋅⋅N and C−H⋅⋅⋅N (shortest C⋅⋅⋅N contact: 317.3 pm) seem to dictate the supramolecular architecture of novel host–guest systems involving nBu4N+, Me3Sn+, [M(CN)6]3− and H2O as primary building blocks (1:2:1:1). The multinuclear (13C, 15N, 59Co, 119Sn) solid-state NMR spectrum of M = Co corroborates very well with the X-ray structure for M = Fe (right: host without guest cations).

The organometallic double metal cyanide [(Me2Sn)3{Co(CN)6}2·6H2O]. A three-dimensional framework of infinite, stapled ribbons

Abstract The admixture of aqueous Me2SnCl2–Me3SnCl solutions to solutions of K3[Co(CN)6] in the molar ratios 3:0:2 and 1:1:1, respectively, affords precipitates of [(Me2Sn)3{Co(CN)6}2·6H2O] (1) and [(Me2Sn)(Me3Sn)Co(CN)6] (2). Another synthesis of 2 is based upon the bromination of [(Me3Sn)3Co(CN)6] in MeOH. The crystal structure analysis of 1 reveals stacks of infinite planar ribbons built up of trans-Me2Sn(μ-NC)4 and trans-Me2Sn(μ-NC)2(OH2)2 units as well as of trans-Co(CN)2 fragments with terminal CN-ligands. Sn←OH2⋯(NC)2 hydrogen bonds interlink adjacent ribbons. Multinuclear (13C, 15N, 59Co, 119Sn) CPMAS solid-state NMR studies of 1 suggest some intra-ribbon dynamics, and help in proposing both a plausible architecture for anhydrous 2 and a better understanding of the nature of another precipitate 5 resulting from the admixture of a Me2SnCl2/Me3SnCl solution to a solution of K4[Fe(CN)6] (1:2:1).

Bis(cyclopentadienyl)lanthanoid(III) alkoxides derived from chiral alcohols with a nitrogen donor functionality: Solution NMR studies of paramagnetic complexes

Abstract The first crystallographically elucidated example of a chiral organolanthanoid alkoxide complex [LnCp′ 2 ( μ -OCHRCHR 1 NR 2 R 3 )] 2 with Ln=Sm, R=Ph, R 1 =H, R 2 =Me and R 3 =CH 2 Ph ( 11 ; prepared from the pure (1R)-(+)-aminoalcohol) is presented. While crystalline 11 involves distinct N–Sm bonds (283.3 pm) in enantiomorphic {(-CHPhCH 2 )(CH 2 Ph)MeN–Sm} fragments, its solution NMR spectra ( 1 H, 13 C) suggest a complete or partial rupture of the N–Sm bonds. More systematic solution 1 H-NMR studies of likewise chiral representatives of the series with R=H, R 1 =Et, R 2 , R 3 =Me and Ln=Pr, Nd, Sm, Yb and Lu, respectively, indicate that at room temperature (r.t.) only the dissolved complexes with Ln=Pr, Nd and Sm involve N–Ln bonds that are stable on the NMR time scale. The homologues with Ln=Yb and Lu are fluxional. The paramagnetic nature of the complexes with Ln=Pr, Nd and Yb turns out to be particularly helpful for the structural deductions in magnifying significantly e.g. the diastereotopic splitting of the ring proton resonances of various CH 3 C 5 H 4 ligands.

Isomeric zirconocenophane dichlorides involving two disiloxane-bridged indenyl ligands

Abstract The title complex 2 = [{O(Me2SiC9H6)2}ZrCl2](SiC9H6 = 2 silylated indenyl group) has been prepared in a way slightly different from that published recently by Rausch and coworkers (J. Organomet. Chem., 501 (1995) 375). In contrast to the earlier report, the 1H NMR spectra of 2 in C6D6 and CD2Cl2 reflect clearly the presence of both rac-2 and meso-2 (ca. 4:1). From toluene, 2 crystallizes as a racemic mixture; rac-2: monoclinic; space group P2√c, a = 1278.2(4), b = 1196.2(4), c = 1567.8(6) pm; β = 100.8(3)°; R1 = 0.0314 (wR2 = 0.0771). The high-resolution 1H NMR spectrum of rac-2 does not match with the crystal structure: most probably, rapid (on the NMR time scale) racemization takes place down to at least −80°C.

[Ni(CN)2 · 2Me3SnCN · (nBu4N)OH]: a layered, supramolecular assembly containing the earlier described, macrocyclic building block [{(Me3Sn)2OH}2{μ-(NC)2Ni(CN)2}2]2−

Abstract The crystal structure of [(nBu4N){(Me3Sn)2OH}{Ni(CN)4}][Ni(CN)2 · 2Me3SnCN · (nBu4N)OH] (1), the formal 1:1-addition product of polymeric [(Me3Sn)2Ni(CN)4][Ni(CN)2 · 2Me3SnCN] and (nBu4N)OH, has been revisited at 153 K. Owing to the presence of distinct (Me3Sn)2OH · · ·NC hydrogen bonds, infinite, negatively charged layers containing cyclic [{(Me3Sn)2OH}2{μ(NC)2Ni(CN)2}2]2− units alternate with layers of nBu4N+ ions. CPMAS solid-state NMR spectra (13C, 15N, 119Sn) strongly support nonsymmetric building blocks with exceedingly weak SnN bonds.

Chiroptische effekte von lanthanoidorganylen mit optisch aktiven liganden III. Erschließung wohldefinierter chiraler organosamarium(III)-verbindungen durch umsetzung von tris(cyclopentadienyl)samarium mit (1S,2R,5R)-Isomenthol, (R)-(+)-Isobutyllactat und (R)-(+)-Methyl-p-tolylsulfoxid☆

Abstract While each of the three organosamarium(III) title complexes: [Cp 2 Sm{μ-OC 10 H 19 }] 2 ( 5 ; Cp = C 5 H 5 , OC 10 H 19 = isomenthoxide), [Cp 2 Sm{μ-OCH(Me)COO i BU}] 2 ( 6 ) and [Cp 3 SmOS(Me)- p -C 6 H 4 Me] ( 7 ) contains a chiral ligand atom (i.e. C or S) next to the metal-bonded oxygen atoms, only the dinuclear compounds 5 and, even better, 6 display (below ca. 600 nm) significant circular dichroism of discrete ff-crystal field transitions. According to a successful single-crystal X-ray study of 5 , the cyclohexyl ring of its (1S,2R,5R)-isomenthoxide ligand adopts a conformation with axial OSm- and i Pr-substituents, which is energetically less favourable at least for neat (1S,2R,5R)-isomenthol.

[Y{2,6-(C5H4CH2)2C5H3N}(µ-OH)]2: a Dinuclear 5-ansa-Yttrocene Hydroxide containing the 2,6-dimethylenepyridyl Bridge

Abstract The novel yttrium(III) complex [YL(μ-OH)]2 (1) with L = {2,6-(C5H4CH2)2C5H3N}2− wherein C5H3N represents a 2,6-pyridine-diyl unit has been obtained by partial hydrolysis of the new homoleptic complex [(YL)2(μ-L)], some lanthanoid homologues of which have so far been characterized only spectroscopically. The crystal structure of 1 resembles that reported earlier for the corresponding (CH2)2O(CH2)2-tethered complex [YL′(M-OH)]2 (3) with L′ = {(C5H4CH2CH2)2O}2− and suggests significant N-Y bonding, although the N-Y distance is relatively long (2.621 (3) A).

The tetrabutylammonium ion: A promising building block for the design of supramolecular assemblies?

Although the C-H...O hydrogen bond is practically ubiquitous in supramolecular assemblies, findings of corresponding C-H … N bridges have so far been comparatively rare. The crystal structures of four related. novel co-ordination polymers involving R 3 Sn + , [M(CN) n ] m and nBu 4 N + ions as essential building blocks have been examined in view of the involvement of C-H… N bridges between any of the α-CH 2 groups of the nBu 4 N + ions and N atoms of the CN ligands. Distinct C-H… N bridges with (in part) unprecedentedly short C… N contacts (down to 317 pm) have in fact been found. primarily with cyanide N atoms not engaged in simultaneous N → Sn bonding. Another cation that turns out to be capable of forming significant C-H… N bridges even with metal-bridging CN-ligands is the complex [Co III (C 5 H 5 ) 2 ] + .