Remarkable stability of tetrabenzo[a,c,g,i]fluorenyl ammonium salts in water: syntheses, reactions, and crystal structures.

Deprotonation of 8bH-tetrabenzo[a,c,g,i]fluorene (8bH-Tbf), an extremely large benzannulated cyclopentadienyl derivative, by [NR3R'][OH] (R = (n)Bu, Et; R' = (n)Bu, Et, Bn) leads to a series of Tbf ammonium salts of the type [NR3R'][Tbf]. These cyclopentadienide analogs were smoothly isolated from a hydrous medium and structurally characterized by single X-ray diffraction. Subsequent reactions demonstrate the high potential of derivatization by converting the presented [Tbf] anions into functionalized Tbf compounds.

Molecular and Electronic Structures of Mononuclear and Dinuclear Titanium Complexes Containing π-Radical Anions of 2,2'-Bipyridine and 1,10-Phenanthroline: An Experimental and DFT Computational Study.

Whereas reaction of [(η(5)-Cp*)Ti(IV)Cl3](0) (1) with 2 equiv of neutral 2,2'-bipyridine (bpy) and 1.5 equiv of magnesium in tetrahydrofuran affords the mononuclear complex [(η(5)-Cp*)Ti(III)(bpy(•))2](0) (2), performing the same reaction with only 1 equiv each of magnesium and bpy provides the dinuclear complex [{(η(5)-Cp*)Ti(μ-Cl)(bpy(•))}2](0) (3). Conducting the latter reaction using 1,10-phenanthroline (phen) in place of bpy resulted in formation of dinuclear [{(η(5)-Cp*)Ti(μ-Cl)(phen(•))}2](0) (4).

Efficient access to titanaaziridines by C-H activation of N-methylanilines at ambient temperature.

Titanaaziridines or η(2)-imine titanium complexes are considered key intermediates of the titanium-catalyzed hydroaminoalkylation of alkenes. Herein, we present an efficient synthetic route to this class of compounds, starting from N-methylanilines and a bis(η(5):η(1)-pentafulvene)titanium complex. Consecutive reactions on the η(2)-methyleneaniline complexes, characterized for the first time, prove a high chemical versatility.

Structure-property relationship of anilino-squaraines in organic solar cells.

Soluble molecular semiconductors are a promising alternative to semiconducting polymers in the field of organic photovoltaics. Here, three custom-made symmetric 1,3-bis(N,N-alkylated-2,6-dihydroxy-anilino)squaraines containing systematic variations in their molecular structures are compared regarding their applicability as donor materials in bulk-heterojunction solar cells. The terminal substitution pattern of the squaraines is varied from cyclic over linear to branched including a stereogenic center.

Dibenzosilanorbornadienyl cations and their fragmentation into silyliumylidenes.

The terphenyl-substituted dibenzosilanorbornadienyl cation 11 was synthesized and isolated in the form of its [B(C6F5)4](-) salt. The salt was characterized by NMR spectroscopy supported by quantum mechanical computations and by an XRD analysis of a corresponding acetonitrilium salt. The thermal fragmentation of 11[B(C6F5)4] in benzene results in the high-yield formation of diphenylterphenylsilylium borate 17[B(C6F5)4].

Titanium-catalyzed intermolecular hydroaminoalkylation of conjugated dienes.

Ti me kangaroo down: Conjugated dienes undergo intermolecular hydroaminoalkylation in the presence of Ti catalyst [Ind2 TiMe2 ] (Ind=η(5) -indenyl). This new reaction offers a highly atom-efficient approach to homoallylic amines from 1,3-butadienes.

A new synthesis of triarylsilylium ions and their application in dihydrogen activation.

Well-shuffled: An unexpected substituent distribution reaction via alkyldiarylsilylium ions leads to a distribution of substituents. Starting from alkyldiaryl silanes, this reaction provides a facile synthetic approach to sterically highly hindered triarylsilylium ions. These silylium ions can be applied in dihydrogen activation reactions.

Stannylium ions, a tin(II) arene complex, and a tin dication stabilized by weakly coordinating anions.

The reactivity of aryl-substituted stannylenes, Ar(2)Sn (4), towards silylarenium borates, [R(3)SiArH][B(C(6)F(5))(4)] (3), was investigated. The reaction with 2,3,4-trimethyl-6-tert-butylphenyl (mebp)-substituted stannylene gave silyl-substituted stannylium ions 2a,b, which were characterized by NMR spectroscopy supported by the results of quantum-mechanical computations of molecular structures and magnetic properties. The tri-iso-propylphenyl-substituted stannylium ions 2c,d undergo a decomposition reaction in toluene to give the dicationic tin-arene complex [Sn(C(7)H(8))(3)](2+) (5) in the form of the [B(C(6)F(5))(4)] salt in high yields.

Persistent dialkyl(silyl)stannylium ions.

The synthesis of dialkyl(silyl)stannylium borates 2[B(C(6)F(5))(4)] by reaction of a stable β-silyl-substituted stannylene 3 with silylarenium borates 4[B(C(6)F(5))(4)] is reported. The stannylium borates 2[B(C(6)F(5))(4)] are characterized by NMR spectroscopy and single-crystal X-ray diffraction, supported by the results of quantum mechanical calculations. The accumulated experimental and theoretical data indicate that the stannylium ions 2 are not stabilized by β-silyl hyperconjugation and that intramolecular C-H/Sn(+) interactions are not important.

A germanium(II) cation with [1+1] coordination.

Breaking the molecular symmetry by protonation of germylene 1 is the key step in the synthesis of the germyliumylidene 2, which is stabilized by an intramolecular interaction with a distant imido group.

Molecular structure of a cyclopropyl substituted vinyl cation.

The experimentally determined molecular structure of vinyl cation 1 provides clear evidence for the occurrence of extended sigma-conjugation involving the cyclopropyl ring and the beta-C-Si bonds.

Selective oxidation and reduction of trinuclear titanium(II) hexaazatrinaphthylene complexes-synthesis, structure, and electrochemical investigations.

Titanocene complexes with chelating N-heterocyclic ligand bridges react with ferrocenium salts as selective oxidants to afford air-stable cationic complexes and allow the preparation of exceptional mixed valence hexaazatrinaphthylene complexes [(Cp2Ti)3(mu3-HATNMe6)]n+ (1n+) (n=1, 2, 3, 4). Cyclic voltammograms (CV) and differential pulse voltammograms (DPV) show that nine oxidation states of 1 are generated without decomposition. Comproportionation constants Kc have been calculated in order to determine the extent of electronic communication between the titanium centers.

Dehydroaromatization of quinoxalines: one-step syntheses of trinuclear 1,6,7,12,13,18-hexaazatrinaphthylene titanium complexes.

We report the spontaneous coupling of N-heterocycles, initiated by C-H bond activation reactions. The reaction of quinoxalines and the titanocene acetylene complex Cp2Ti{eta2-C2(SiMe3)2}, as an excellent titanocene source, results in the formation of trinuclear 1,6,7,12,13,18-hexaazatrinaphthylene (HATN) titanium complexes. These HATN titanium complexes are thermally stable but sensitive to air and moisture.

Controlling the rate of shuttling motions in [2]rotaxanes by electrostatic interactions: a cation as solvent-tunable brake.

A series of rotaxanes, with phenolic axle centerpieces and tetralactam macrocycles as the wheels, has been prepared in good yields. The threaded rotaxane structure is confirmed in the gas phase by tandem mass spectrometric experiments through a detailed fragmentation pattern analysis, in solution by NMR spectroscopy, and in the solid state through X-ray crystallography. A close inspection of the 1H,1H NOESY and 1H,1H ROESY NMR data reveals the wheel to travel along the axle between two degenerate diamide "stations" close to the two stoppers.

Titanium-based molecular squares and rectangles: syntheses by self-assembly reactions of titanocene fragments and aromatic N-heterocycles.

This paper reports on the potential of titanium compounds as building blocks for supramolecular polygons. Self-assembly reactions of low-valent titanocene units and N-heterocyclic bridging ligands lead to novel titanium-based supramolecular squares. Pyrazine (3), 4,4'-bipyridine (4), and tetrazine (5) were used as bridging ligands, and the acetylene complexes [Cp2Ti{eta2-C2(SiMe3)2}] (1) and [(tBuCp)2Ti{eta2-C2(SiMe3)2}] (2) as sources of titanocene fragments.

Tris(triphenylplumbyl)plumbate: an anion with three stretched lead-lead bonds.

Treatment of lead(II) bromide with phenylmagnesium bromide at low temperature furnishes yellow crystals of the ionic compound [BrMg(THF)5]+ [:Pb(PbPh3)3]- which, upon X-ray crystallographic analysis, reveals three stretched Pb-Pb bonds and Pb-Pb-Pb angles of about 93 degrees.

Hexaarylcyclotriplumbane: a molecule with a homonuclear ring system of lead.

The reaction of lead(II) bromide with RMgBr, R = 2,4,6-Et3C6H2, furnishes black crystals of hexakis(2,4,6-triethylphenyl)cyclotriplumbane (1) as the first molecule with a homonuclear lead ring. 1 adopts a skewed structure with highly stretched Pb-Pb bond lengths of 3.185 A (average), which indicate that the three-membered ring is formed by weak interactions of 3 singlet plumbylene molecules.

Synthesis and Characterization of Neutral Hexanuclear Iron Sulfur Clusters Containing Stair-like [Fe(6)(&mgr;(3)-S)(4)(&mgr;(2)-SR)(4)] and Nest-like [Fe(6)(&mgr;(3)-S)(2)(&mgr;(2)-S)(2)(&mgr;(4)-S)(&mgr;(2)-SR)(4)] Core Structures.

The binuclear iron complex [{Fe("EtN(2)S(2)")}(2)] (1b, "EtN(2)S(2)" = N,N'-diethyl-3,7-diazanonane-1,9-dithiolate) was prepared from the free ligand and ferrous bis[bis(trimethylsilyl)amide] in toluene. In dichloromethane 1b reacts with the [Fe(4)S(4)I(4)](2-) cubane cluster to displace two iodo ligands and to form the neutral hexanuclear cluster [{Fe("EtN(2)S(2)")}(2)Fe(4)S(4)I(2)] (2), which is isolated as black crystals in 87% yield. As elucidated by an X-ray structure analysis, 2 contains the novel hexanuclear stair-like [Fe(6)(&mgr;(3)-S)(4)(&mgr;(2)-SR)(4)] core, which exhibits crystallographic inversion symmetry.

A Novel Route to Fulvene Complexes of Titanium-Diastereoselective Complexation of Pentafulvenes to Cyclopentadienyltitanium Fragments.

An alternative to the known thermally induced syntheses of fulvene complexes of early transition metals is now provided by the direct reductive complexation of pentafulvenes to [CpTiCl] fragments. These generally highly diastereoselective reactions enable a broad variation of substitution patterns and establish an extensive subsequent chemistry.

Syntheses and properties of zinc and calcium complexes of valinate and isovalinate: metal alpha-amino acidates as possible constituents of the early Earth's chemical inventory.

We have studied the ligand behavior of racemic isovalinate (iva) and valinate (val) towards zinc(II) and calcium(II). The following solid metal amino acidates were obtained from aqueous solutions: Zn3Cl2(iva)4 (1), Zn3Cl2(val)4 (2). Zn(val)2 (3), Zn(iva)2 x 2H2O (4), Zn(iva)2 x 3.

Complete defluorination of 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene by titanium tetrakis(dimethylamide)--selective formation of a cyclic hexanuclear titanium fluoroamide and 6,6-dimethylaminotetramethylfulvene.

1,2,3,4-Tetramethyl-5-(trifluoromethyl)cyclopentadiene (Cp*CF3-H, 1) reacts with [Ti(NMe2)4] (2) under mild conditions to give [Ti(mu-NMe2)(NMe2)(mu-F)(F)]6 (3) in nearly quantitative yield. The molecular structure of 3 consists of a ring of six [TiF2(NMe2)2] edge-bridged octahedra. Titanium complexes containing the Cp*CF3 ligand, which was the primary intention of these investigations, were not observed.