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Reaction of the trivalent uranium complex [((Ad,MeArO)3N)U(DME)] with [Na(OCP)(dioxane)2.5] and 2.2.2-crypt yields the μ-oxo-bridged, diuranium complex [Na(2.2.2-crypt)][{((Ad,MeArO)3N)U(DME)}(μ-O){((Ad,MeArO)3N)U(CP)}] (1). Complex 1 features an asymmetric, dinuclear UIV–O–UIV core structure with a cyaphide (CP–) anion η1-CP bound to one of the U ions, and a κ2-O DME coordinated to the other. The CP– ligand is unprecedented in uranium chemistry and is formed through reductive C–O bond cleavage of the phosphaethynolate anion (OCP–). An analogous reaction was performed starting from the tetravalent uranium halide complex [((Ad,MeArO)3N)U(DME)(Cl)]. This salt metathesis approach with [Na(OCP)(dioxane)2.5] results in formation of the mononuclear complex [((Ad,MeArO)3N)U(DME)(OCP)] (2) with an OCP– anion bound to the uranium(IV) center via the oxygen atom in an η1-OCP fashion.

The efficient multi-step, large-scale synthesis, spectroscopic characterization and solid-state molecular structure of a new type of three-fold functionalized, sterically demanding triazine is reported. The aromatic heterocycle 6,6′,6′'-((1,3,5-triazine-2,4,6-triyl)tris(methylene))tris(2,4-di- tert -butylphenol) possesses three 2,4-di- tert -butylphenol synthons bound to the 1,3,5-triazine ring via synthetically challenging methylene linkages in the 2,4,6 positions. The key to success was found in the generation of a highly reactive imidate hydrochloride salt, namely ethyl 2-(3,5-di- tert -butyl-2-methoxyphenyl)acetimidate hydrochloride, that readily undergoes cyclotrimerization. The reported preparation opens new perspectives in the design and synthesis of novel triazine molecules bearing flexible and sterically demanding functionalized groups for various applications.

Tetra-tert-butyl-P5-deltacyclene 5 represents one of only two asymmetric P-C cage compounds, which are available in highly enantiomerically enriched versions. This paper reports about stereoselective substitution reactions of 5 to develop the chemistry of optically active P-C cages further. Electrophilic substitution of the only secondary phosphorus atom P1 of the cage with methyl and benzyl groups was achieved with 92 % and >99 % de, but the yields of the reactions are limited due to competing processes. The uncatalyzed hydrophosphination reaction of a monosubstituted allene and two α,β-unsaturated carbonyl compounds with 5 proved to be the method of choice. cis-Butanone-P5-deltacyclene 12 is formed in 92 % yield and with >99 % de and cis-pentanone-P5-deltacyclene 13a is accessible with >99 % de for P1 and 92 % de for the attached carbon atom at the same time. Besides stereoselectivity, the hydrophosphination reaction of 5 performs with a good regioselectivity. The chiral cage 5 controls the stereoselectivity of its reactions for the cage elements as well as for the α position of a substituent.

We thank Prof. Anthony Linden (University of Zurich) for solving the crystal structure of 8 and Ms. Christina Wronna for carrying out the elemental analyses. Financial support by Friedrich–Alexander University and King Abdullah University of Science and Technology (KAUST) is acknowledged. For computer time, this research used the resources of the Supercomputing Laboratory (KSL) at KAUST.

10-Phenyl-5H-dibenz[b,f]azepine (5) is synthesized by Suzuki cross coupling of the protected bromo alkene 4 with PhB(OH)2. 5 reacts with PCl3 to afford the dichlorophosphanyl-azepine 6 in >90% yield. Alkylation of 6 with 1 equiv of t-BuMgBr leads, after recrystallization in Et2O, to the diastereomerically enriched (dr > 98:2) chloride rac-7, which the crystal structure reveals to be the (pS,RP)/(pR,SP) pair. The fact that rac-7 crystallizes in the Sohncke space group P212121 opens up the possibility of a mechanical separation of the enantiomers. Methylation of rac-7 is perfectly stereoselective with inversion of configuration at the P atom to yield the new ligand rac-8 as the (R,R)/(S,S) pair. The corresponding BH3-protected diastereomer rac-9 (i.e., the (R,S)/(S,R) pair), is isolated after flash column chromatography in 73% yield. Compounds 5–9 are accessible in multigram quantities. X-ray crystal structures of Ru(II) complexes demonstrate the ambidentate nature of ligand rac-8: Complex 10 is exclusively...

Starting from nickel(II) cubane [NiII4(HL)4(OAc)4] (2a), five different tetranuclear cubic complexes [NiII4(HL)4(O2CR)4] (3) were generated simply by applying a post-synthetic cubane modification strategy via a complete acetate-to-carboxylate co-ligand exchange. This was achieved by stirring the parent complex 2a with a large excess of the corresponding sodium carboxylate salt 4 for three days in THF. Single-crystal X-ray structure analyses of NiII cubanes 3a·2 Et2O and 3b·0.5 CH2Cl2·0.5 Et2O reveal unequivocally that both are isostructural in terms of the [Ni4(μ3-O4]4+ core and crystallize in the triclinic space group P-1 with two molecules in the unit cell. In the solid state, the cubic centers of 3a,b differ only slightly in bond lengths and angles mainly due to the different substituents in the carboxylate co-ligand and packing in the unit cell. The orientation of 3a,b and the formation of supramolecular aggregates in the crystal packing were controlled by π–π interactions as well as intra- an...

Chiral P C cage compound tetra-tert-butyl-P5-deltacyclene 7 and the coinage metal salts CuCl, CH3COOAg, and (PPh3)AuCl form binuclear complexes with the metal atoms in the bridging position. In the case of copper, a Cu2Cl2 ring connects two intact ligands 7, with tertiary P2 as the active donor center. For silver and gold, P5 of the cage becomes deprotonated and acts as a second ligand function. Two parallel and linear P-M-P bridges result with a moderate M …. .M d10-d10 metallophilic interaction. In contrast to that, the Rh(I) ion of dimeric [(1,5-COD)RhCl]2 adds to 7 in an oxidative addition to the P P bond of the smallest ring structure of 7, a diphosphirane. A partially opened cage structure results and three of the five P-atoms coordinate to Rh(III) to form a central Rh2P2 ring which links the cages. All four complexes are Ci symmetric in the solid state and form meso-diastereomers. Because of symmetry reasons, rac-diastereomers of the complexes should exist as well. Two sets of NMR spectra A and B are indeed observable for all of them which agree well with a pair of diastereomers, but no unambiguous relation between A and B on the one side and rac- and meso-diastereomers at the other side has been found.

The ‘privileged’ P-alkene ligand (S)-2 is synthesized on a > 40 gram scale in 96% yield starting from dibenz[b,f]azepine-PCl2 (1; accessible on > 80 g scale) and (S)-BINOL. Similarly, the P-alkenes (R)-3 and the ‘chiral-at-P’ (SP ,SC )-4 are obtained from (R)-Taddol [(R,R)-α,α,α',α'-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol] and (S)-α,α-diphenylprolinol, respectively, in multigram quantities and high purity. The crystal structures of (SP ,SC )-4, its diastereomer (RP ,SC )-4, and of the (R)-SPINOL-derived ligand (R)-5 are reported. A slightly revised synthesis of SPINOL is also disclosed.

Cage-chiral P5-deltacyclene 1 is available as a pair of highly enriched P–C cage enantiomers 1′ and 1″, which exist as pairs of epimers a and b. Deprotonation of cage atom P1 initiates a rearrangement reaction, in which P1 and the neighboring carbon atom C4, together with its substituent, change places to form optically active iso-P5-deltacyclene enantiomers 6″ and 6′, again as pairs of epimers. The CD spectra of related pairs of optically active cages 1 and 6 consist of almost mirror-symmetric curves, an indicator of mirror-symmetric cage structures. This surprising result was verified by an absolute structure determination of the W(CO)5 complex 9a″. With the exception of the two cage nuclei that had changed places in relation to starting material 1′, all other cage nuclei of rearrangement product 6a″ occupy mirror-symmetric positions. To the best of our knowledge, this represents the first cage-inversion reaction of an optically active compound. P1 is the only active donor center of 6 involved in the bonding of M(CO)5 fragments (M = Cr, Mo, W). The chiroptical properties of Cr(CO)5 complex 7a′ and W(CO)5 complex 9a″ are almost mirror-symmetric and resemble those of the free cages 6′ and 6″, respectively. The coordinated transition-metal complex fragments do not contribute significantly to the Cotton effects of the P–C cage. A DFT analysis of the deprotonated cage anions [1 – H]– and [6 – H]– predicts a driving force of –20.3 kcal mol–1 for the rearrangement reaction.

This work illustrates that manganese(V) nitrido complexes are able to undergo a coordination-induced spin-state change by altering the ligand field from trigonal to tetragonal symmetry. For the reversible coordination of acetonitrile to trigonal [(TIMEN(xyl))Mn(N)](2+) (1; high-spin S = 1; with TIMEN(xyl) = tris[2-(3-xylylimidazol-2-ylidene)ethyl]-amine), a temperature-dependent coordination-induced spin-state switch is established. Starting from the manganese(V) nitrido complex 1, the synthesis and characterization of a series of octahedral, low-spin (S = 0) manganese(V) nitrido complexes of the type [(TIMEN(xyl))Mn(N)(L)](n+) (L = MeCN (2), (t)BuNC (3), CN(-) (4), NCS(-) (5), F(-) (6), μ-{Ag(CN)2}(-) (7), with n = 1, 2) is described. These represent the first examples of d(2) transition metal complexes showing a coordination-induced spin-state change. Spectroscopic, as well as ligand-field theory and density functional theory studies suggest a transition from a 2 + 2 + 1 orbital splitting in the trigonal case to a 1 + 2 + 1 + 1 splitting in tetragonal symmetry as the origin of the coordination-induced spin-state change.

Starting from dimethyl 2,6-pyridinedicarboxylate (3), four pyridine-bridged bispyrazole ligands 1a–1d were generated in a two- or three-step synthesis sequence and further treated with UCl4 to yield the corresponding novel mononuclear uranium(IV) complexes [UIV(R′′′2L)(Cl)4] (2a–2d). Compounds 2a–2d were characterized by a variety of spectroscopic and physical methods (e.g. UV/Vis, SQUID, CV, etc.), corroborating the +4 oxidation state in 2a–2d. Single-crystal X-ray structure analyses revealed that 2a·2THF crystallizes in the orthorhombic space group Pbca, 2b·0.8THF·0.2Et2O in the monoclinic Sohncke space group P21, 2c·0.25Et2O in the monoclinic one P21/c, and finally 2d·0.5THF in the orthorhombic Sohncke space group P21212. In the solid state, complexes 2a–2d possess a distorted pentagonal–bipyramidal coordination sphere at the UIV centers and an out-of-plane shift (doop) of up to 1.12 A, which can be explained by an increased steric pressure on the metal ions at the binding sites of the chelating ligands 1c and 1d. Finally, by combination of different 1D and 2D NMR experiments, the 1H and 13C resonances can be unequivocally assigned in the corresponding paramagnetic NMR spectra of 2a–2d.

Reaction of the quintuply bonded chromium(I) dimer [ApCrCrAp] (Ap = sterically demanding 2-aminopyridinate) with pyrazine yields a chromium(II) complex with a η(4):η(4) face-on coordinated pyrazine dianion. Reaction with 4,4'-bipyridine, on the other hand, completely cleaves the metal-metal bond, leading to a chromium(II)-based molecular square. XRD and magnetic measurements show ligand radical anions and a ferrimagnetic alignment of alternating metal and ligand magnetic moments. Controlled polymerization of the molecular square with pyrazine yields a porous coordination polymer featuring both reduced and nonreduced linkers.

The chemokine receptor CXCR3 is a G protein-coupled receptor, which conveys extracellular signals into cells by changing its conformation upon agonist binding. To facilitate the mechanistic understanding of allosteric modulation of CXCR3, we combined computational modeling with the synthesis of novel chemical tools containing boronic acid moiety, site-directed mutagenesis, and detailed functional characterization. The design of boronic acid derivatives was based on the predictions from homology modeling and docking. The choice of the boronic acid moiety was dictated by its unique ability to interact with proteins in a reversible covalent way, thereby influencing conformational dynamics of target biomolecules. During the synthesis of the library we have developed a novel approach for the purification of drug-like boronic acids. To validate the predicted binding mode and to identify amino acid residues responsible for the transduction of signal through CXCR3, we conducted a site-directed mutagenesis study. With the use of allosteric radioligand RAMX3 we were able to establish the existence of a second allosteric binding pocket in CXCR3, which enables different binding modes of structurally closely related allosteric modulators of CXCR3. We have also identified residues Trp109(2.60) and Lys300(7.35) inside the transmembrane bundle of the receptor as crucial for the regulation of the G protein activation. Furthermore, we report the boronic acid 14 as the first biased negative allosteric modulator of the receptor. Overall, our data demonstrate that boronic acid derivatives represent an outstanding tool for determination of key receptor-ligand interactions and induction of ligand-biased signaling.

In a multiple-bond metathesis reaction, the triazacyclononane (tacn)-anchored methyl- and neopentyl (nP)-substituted tris(aryloxide) U(III) complex [(((nP,Me)ArO)3tacn)U(III)] (1) reacts with mesityl azide and CO2 to form mesityl isocyanate and the dinuclear bis(μ-oxo)-bridged U(V)/U(V) complex [{(((nP,Me)ArO)3tacn)U(V)}2(μ-O)2] (3). This reaction proceeds via the mononuclear U(V) imido intermediate [(((nP,Me)ArO)3tacn)U(V)(NMes)] (2), which has been synthesized and fully characterized independently. The dimeric U(V) oxo species shows rich redox behavior: complex 3 can be reduced by one and two electrons, respectively, yielding the mixed-valent U(IV)/U(V) bis(μ-oxo) complex [K(crypt)][{(((nP,Me)ArO)3tacn)U(IV/V)}2(μ-O)2] (7) and the U(IV)/U(IV) bis(μ-oxo) complex K2[{(((nP,Me)ArO)3tacn)U(IV)}2(μ-O)2] (6). In addition, complex 3 can be oxidized to provide the mononuclear uranium(VI) oxo complexes [(((nP,Me)ArO)3tacn)U(VI)(O)eq(OTf)ax] (8) and [(((nP,Me)ArO)3tacn)U(VI)(O)eq]SbF6 (9). The unique series of bis(μ-oxo) complexes also shows notable magnetic behavior, which was investigated in detail by UV/vis/NIR and EPR spectroscopy as well as SQUID magnetization studies. In order to understand possible magnetic exchange phenomena, the mononuclear terminal oxo complexes [(((nP,Me)ArO)3tacn)U(V)(O)(O-pyridine)] (4) and [(((nP,Me)ArO)3tacn)U(V)(O)(O-NMe3)] (5) were synthesized and fully characterized. The magnetic study revealed an unusually strong antiferromagnetic exchange coupling between the two U(V) ions in 3. Examination of the (18)O-labeled bis(μ-oxo)-bridged dinuclear complexes 3, 6, and 7 allowed for the first time the unambiguous assignment of the vibrational signature of the [U(μ-O)2U] diamond core structural motif.

Reaction of cyclometalated platinum(II) precursor [Pt(C^N)Cl(dmso)], 1, C^N = N(1), C(2′)-chelated deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, with 1 equivalent of triphenyl phosphine, PPh3, or 1,3,5-triaza-7-phosphaadamantane, PTA, gave the complex [Pt(C^N)Cl(PPh3)], 2, or [Pt(C^N)Cl(PTA)], 3, respectively. On the basis of careful multinuclear NMR spectroscopy, supported by a number of 2D NMR experiments, structures of the complexes 2 and 3 in solution were determined to be neutral four coordinate. The X-ray crystallography indicated that the solid-state structure of complex 3 comprised a common square-planar geometry around platinum(II). Cytotoxicity of the complexes 2 and 3 was studied in three human cancer cell lines derived from ovarian carcinoma (CH1), lung carcinoma (A549), and colon carcinoma (SW480).

Dibenzazepinyl dichlorophosphine 2 reacts with (R,R)-2,3-O-isopropylidene-threitol (3) in Et2O solution to afford gram-quantities of the enantiopure macrocylic phosphoramidite (all-R)-6, which may be seen as a formal dimer of classic phosphoramidite P-alkene hybrid ligands. Complexation experiments with PdCl2 reveal highly selective formation of the trans-dinuclear complex (all-R)-11. The corresponding bulkier and rigidly trans-eclipsed 1,4-diol (S,S)-bis-hydroximethyl-9,10-dihydro-9,10-ethaneanthracene (4), does not favor macrocycle formation and exclusively leads to the new dibenzazepinyl phsophormaidite P-alkene ligand 7, which in Pd-catalyzed asymmetric allylic amination comes the well-known ‘privileged’ binol-derived P-alkene analogue 1 close in terms of enantioselection.

Diastereomeric Pd and Pt complexes with a highly rigid chelate cage ligand core have been designed on the basis of alkylated C2-symmetric tetra-tert-butylhexaphosphapentaprismanes R2P6C4tBu4. The ligands are accessible by substitution of the diiodo derivative I2P6C4tBu4 with Grignard and organyllithium reagents. Depending on the optical properties of the organyl group, racemic or diastereomeric dialkylhexaphosphapentaprismanes R2P6C4tBu4 can be treated with suitable PdII or PtII precursor complexes to form neutral square-planar cis-[(R2P6C4tBu4)PdCl2] and cis-[(R2P6C4tBu4)PtCl2] complexes, respectively. Monoalkylation products RIP6C4tBu4 were also observed in the reaction mixtures, but in most cases were inactive as chelate ligands towards PdII and PtII. For R = (S)-2-methylbutyl, the diastereomers of the PdCl2 complex were efficiently separated by column chromatography and crystallization to give the two diastereomers in up to >99 % de and they were fully characterized by NMR and CD spectroscopy as well as by X-ray diffraction analysis. The two diastereomers of cis-[{(S)-2-methylbutyl}2(P6C4tBu4)PdCl2] represent the first example of a pair of isolated optically active, C2-symmetric, square-planar PdII complexes with chelate P–C cage ligands. A square-planar Pd complex with two monoanionic RP6C4tBu4 cage ligands can be obtained from the monoallylation product (allyl)IP6C4tBu4. This reaction failed for the other monoalkylation products RIP6C4tBu4 and PtII.

Starting from phenols R1,R2ArOH (5) and the anisole derivative 3,5-di-tert-butyl-2-methoxybenzyl bromide (13), a series of new tacn-based ligands (R1,R2ArOR3)3tacn (2) have been synthesized with substituents of varying bulkiness and electronic nature at the ortho and para positions with respect to the oxygen coordination site. It was observed that these groups not only determine the steric shielding and solubility properties of 2, but also deactivate the reactivity of the phenols in the modified Mannich reaction when electron-withdrawing groups are introduced at the para position in 5. Treatment of the ligands with UCl4 in thf led to the isolation of four uranium(IV) chloro complexes [{(R1,R2ArO)3tacn}UIVCl] (14), which were characterized by different spectroscopic and physical methods (e.g., 1H NMR, UV/Vis, SQUID), corroborating the +4 oxidation state in 14. Single-crystal X-ray structure analyses revealed that 14a·CH2Cl2·CH3CN and 14b·1.25CH2Cl2 crystallize in the chiral, orthorhombic space group P212121 [a = 24.934(3), b = 27.941(3), c = 9.045(1) A, V = 6302(2) A3, Z = 4] and the chiral, hexagonal space group P63 [a = 22.097(3), c = 17.941(2) A, V = 7587(2) A3, Z = 4], respectively. Interestingly, complexes 14a,b self-organize in the solid state into homochiral 1D polymeric superstructures as a result of weak intermolecular C–H···Cl contacts.

An inverse trans influence has been observed in a high-valent U(V) imide complex, [(((Ad)ArO)(3)N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(((Ad)ArO)(3)N)U(NMes)], and the model complexes [(((Me)ArO)(3)N)U(NMes)] and [(NMe(3))(OMe(2))(OMe)(3)U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(((Ad)ArO)(3)N)U(NTMS)] and U(IV) azide complex [(((Ad)ArO)(3)N)U(N(3))] are also presented for comparison.

The syntheses of the two dicarbonyl complexes [Ru(bdmpza)Cl(CO)2] (3) and [Ru(2,2-bdmpzp)Cl(CO)2] (4), bearing a bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) or a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionato (2,2-bdmpzp) scorpionate ligand, are described. Both complexes are obtained by reacting the polymer [RuCl2(CO)2]n with either K[bdmpza] or K[2,2-bdmpzp]. Reaction of the acid Hbdmpza with [Ru3(CO)12] results in the formation of two structural isomers of a hydrido complex, [Ru(bdmpza)H(CO)2] (5a,b). Under aerobic conditions conversion of [Ru(bdmpza)H(CO)2] (5a,b) to form the Ru(I) dimer [Ru(bdmpza)(CO)(μ-CO)]2 (6) seems to be hindered in comparison to the case for the η5-C5H5 (Cp) analogues. Dimer 6 is obtained via a reaction of Hbdmpza with catena-[Ru(OAc)(CO)2]n instead. The molecular structures of 3, 4, and 6 have been obtained by single-crystal X-ray structure determinations. The precatalytic properties of the two dicarbonyl complexes 3 and 4 toward the catalytic oxidation of cyclohexene with diffe...

The copper(II) complexes [Cu4(1,3-tpbd)2(H2O)4(NO3)4]n(NO3)4n·13nH2O (1), [Cu4(1,3-tpbd)2(AsO4)(ClO4)3(H2O)](ClO4)2·2H2O·0.5CH3OH (2), [Cu4(1,3-tpbd)2(PO4)(ClO4)3(H2O)](ClO4)2·2H2O·0.5CH3OH (3), [C...

Cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, in which C^N = N(1),C(2′)-chelated deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was reacted with 1 equiv of 1,1′-bis(diphenylphosphino)ferrocene, dppf, to give the cyclometalated diplatinum(II) complex [Pt2(C^N)2Cl2(μ-dppf)], 2, along with 0.5 equiv of unreacted dppf. However, the related reaction with 0.5 equiv of dppf produced complex 2 in pure form. Complex 2 in solution was fully characterized by using multinuclear NMR spectroscopy (1H, 13C, 31P, and 195Pt) and a number of 2D NMR experiments. The structure of complex 2 in solid state was determined by X-ray crystallography showing that the bridging dppf ligand is arranged close to “antiperiplanar staggered” conformation. Cytotoxicity of the complex 2 was studied in three human cancer cell lines derived from ovarian carcinoma(CH1), lung carcinoma(A549), and colon carcinoma (SW480) by means of the MTT assay (MTT = 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide).

The syntheses and solid-state structures of a series of imidazolium (IM) salt-based, double C12 alkyl chain functionalized ionic liquids, namely, [C12C12IM][A], where the anion A is I−, I3−, I5−, N...

The reaction of K2[PdCl4] with [(S,S)-H2(Et)2eddv]Cl2 diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl2{(S,S)-(Et)eddv-κ2 N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (1H and 13C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.

The coordination chemistry of copper complexes with theligand L1 [L1 = {7E}-N1-benzylidene-N2-{(E)-2-(benzylideneamino)ethyl}ethane-1,2-diamine] has been investigated. For copper(I) complexes of L1, the counterion determines the molecular structure in the solid state. The reaction of [Cu(CH3CN)4]PF6 with L1 yielded the mononuclear complex [Cu(L1)(CH3CN)]PF6 (1), whereas dinuclear helical [Cu2(L1)2](ClO4)2 (2) resulted from a similar reaction with [Cu(CH3CN)4]ClO4. Both compounds have been structurally characterized, and their solution behaviour investigated. Structurally characterized [Cu(L1)(PPh3)]ClO4 (3) has been synthesized by reacting 2 with PPh3. Exposure of a solution of 1 towards dioxygen in CH3OH and CH2Cl2 yielded the dinuclear complexes [Cu2(L1)2(OCH3)2](PF6)2 (4) and [Cu2(L1)2(OH)2](PF6)2 (5), respectively. Both compounds have been fully characterized. During the oxidation reaction, no hydroxylation of L1 occurred. The oxidation reaction of 1 has been studied by a chemical approach and by UV/Vis spectroscopy, indicating the formation of a peroxido-bridged species during the reaction. Furthermore, by reduction of the imine groups in L1 the ligand L2 [L2 = N1-benzyl-N2-{2-(benzylamino)ethyl}ethane-1,2-diamine] was obtained and the dinuclear copper(II) complex [Cu2(L2)2Cl3]PF6·2MeOH (6) has been structurally characterized.

To further improve the maximal serotonergic efficacy and better understand the configurational requirements for 5-HT(1A) binding and activation, we generated and biologically investigated structural variants of the lead structure befiradol. For a bioisosteric replacement of the 3-chloro-4-fluoro moiety, a focused library of 63 compounds by solution phase parallel synthesis was developed. Target binding of our compound collection was investigated, and their affinities for 5-HT(2), α(1), and α(2)-adrenergic as well as D(1)-D(4) dopamine receptors were compared. For particularly interesting test compounds, intrinsic activities at 5-HT(1A) were examined in vitro employing a GTPγS assay. The investigation guided us to highly selective 5HT(1A) superagonists. The benzothiophene-3-carboxamide 8bt revealed almost exclusive 5HT(1A) recognition with a K(i) value of 2.7 nM and a maximal efficacy of 124%. To get insights into the bioactive conformation of our compound collection, we synthesized conformationally constrained bicyclic scaffolds when SAR data indicated a chair-type geometry and an equatorially dispositioned aminomethyl substituent for the 4,4-disubstituted piperidine moiety.

The ligand L1 (N1,N3-di[2-di(2-pyridylmethyl)aminoethyl]N1,N3-dimethyl-1,3-propandiamine) bridges two tripodal units of the amine ligand Me2uns-penp (N1,N1-dimethyl-N2,N2-di(2-pyridylmethyl)-1,2-ethandiamine) with a propyl group. The ligand L1, the dinuclear copper(I) complex [Cu2(L1)](BPh4)2 and the dinuclear copper(II) complexes [Cu2Cl2(L1)](ClO4)2, and Cu2Cl2(L1)]Cl2 have been synthesized and structurally characterized. The copper(I) complex reacts reversibly with dioxygen at low temperatures and forms a peroxido complex that is thermally more stable than the related peroxido complex formed from two mononuclear copper(I) complexes of the ligand Me2uns-penp.

The diamantane functionalized triazacyclononane ligand ( Dia ArOH) 3 tacn (L 3 ) has been synthesized and the reactivity of its U(III) metallated product [(( Dia ArO) 3 tacn)U] (1) has been explored. Complex 1 promotes dichloromethane and azidotrimethylsilane activation to generate U(IV) complex [(( Dia ArO) 3 tacn)U(Cl)] (2) and U(V) complex [(( Dia ArO) 3 tacn)U(NTMS)] (3), respectively. Spectroscopic investigations of complexes 1, 2, and 3 will be discussed, along with molecular structures where possible.

Synthesis and characterization of a manganese complex of a new redox-active diaminocyclohexane derivative of a thiourea-based ligand with SNNNS donor atom set is reported. The molecular structure of the complex exhibits a pentadentate SNNNS ligand coordinated in the neutral form to the Mn(II) center. The coordination around the central metal is best described as distorted trigonal bipyramidal with the pyridine nitrogen and the two sulfur atoms being in the equatorial plane and the remaining two nitrogen donors occupying the apical positions of the bipyramid. Cyclic voltammetry in DMSO shows the MnII/MnIII redox couple with the oxidation peak at −0.199 V and the reduction peak at −0.587 V vs. Fc/Fc+ (scan rate 0.5 V s−1). The ligand itself possesses redox activity and exhibits prominent oxidation and reduction peaks at −1.194 and −1.481 V vs. Fc/Fc+, respectively. The results of electrochemical experiments under oxygen atmosphere suggest that upon reaction with electrochemically generated superoxide the redox-active ligand is modified causing decomposition of the complex.

The synthesis of a potentially redox active tripodal ligand containing a tris(aryloxide) functionalized mesitylene anchor, (((tBu)ArOH)(3)mes) (1), and its metalation with low-valent uranium to form [(((tBu)ArO)(3)mes)U] (1-U) is reported. The results from characterization by X-ray crystallography, spectroscopic studies, and computational analysis, as well as initial reactivity studies, support a +3 uranium oxidation state. Comparison to the previously synthesized complex, [(((tBu)ArO)(3)tacn)U] (2-U), featuring the redox-innocent triazacyclononane anchor reveals that changing the anchor from the flexible triazacyclononane to a rigid mesityl fragment increases the structural flexibility of the aryloxide substituents in complexes of 1. The synthesis and crystal structures of uranium(IV) amide complexes of 1-U and 2-U are discussed.

A new tetramethylplatinum(IV) complex [PtMe4(dppf)] [2; dppf = 1,1′-bis(diphenylphosphanyl)ferrocene], as the first platinum(IV) complex to contain a chelating dppf ligand, was prepared by the reaction of the known dimeric tetramethylplatinum(IV) complex cis,cis-[Me4Pt(μ-SMe2)2PtMe4] (1) with the biphosphane ligand dppf (2 equiv.) at room temperature by replacement of the SMe2 ligands with the P ligating atoms of dppf. The single-crystal X-ray structure of complex 2 revealed that the dppf chelating ligand is arranged close to the “synperiplanar–eclipsed” conformation, with a Cp(centroid)···Fe···Cp(centroid) twist angle of 17.6° and a dppf bite angle, P1–Pt1–P2, of 95.77(3)°. This is in contrast to the usually preferred “synclinal–staggered” conformation, in which the Cp(centroid)···Fe···Cp(centroid) twist angle is close to 36° as found in PtII complexes with chelating dppf ligands, like for example [PtMe2(dppf)] exhibiting a dppf bite angle close to 100°. When complex 2 was treated with the strong acid CF3COOH (1 equiv.) first evolution of methane was observed, followed by a C–C coupling reaction to give ethane and the methylplatinum(II) complex [PtMe(OCOCF3)(dppf)] (3). The reaction of complex 2 with the nucleophile HgCl2 (1 equiv.) similarly gave MeHgCl, ethane, and the methylplatinum(II) complex [PtMeCl(dppf)] (11). The structure of complex 3 was also determined by X-ray crystallography. The geometry around the platinum center is best described as distorted square-planar and the dppf is arranged in the usually preferred “synclinal–staggered” conformation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide–alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence.

The synthesis, structure and ligand substitution mechanism of a new five-coordinate copper(II) complex with a sterically constrained pytBuN3 chelate ligand [pytBuN3 = 2,6-bis(3,5-di-tert-butylphenyliminomethyl)pyridine] are reported. In the crystal structure of the complex the [Cu(pytBuN3)Cl2] chromophore possesses a distorted trigonal-bipyramidal coordination geometry. The kinetics and mechanism of chloride substitution by thiourea (TU) and N,N,N′,N′-tetramethylthiourea (TMTU) were studied in detail as a function of nucleophile concentration, temperature and pressure in methanol as solvent. The kinetics showed that the substitution reaction of [Cu(pytBuN3)Cl2] is a biphasic process that involves the subsequent displacement of both chloride ligands. The substitution of the first chloride by TU, k1296 = 918 ± 30 M–1 s–1, is 570 times faster than the substitution of the second chloride, k2296 = 1.62 ± 0.06 M–1 s–1. Substitution of chloride by TU is characterized by the activation parameters: ΔH# = 42 ± 2 and 58 ± 2 kJ mol–1, ΔS# = –46 ± 7 and –47 ± 6 J K–1 mol–1, and ΔV# = –6.5 ± 0.2 and –5.3 ± 0.7 cm3 mol–1, for the first and second substitution reactions, respectively. It is concluded from the activation parameters that both reactions follow an associative interchange (Ia) mechanism. When the substitution reaction was carried out with the sterically hindered nucleophile TMTU, the rate constant for the displacement of the first chloride, k2296 = 6.9 ± 0.5 M–1 s–1, was more than 133 times slower than for the reaction with TU, which further supports the Ia nature of the substitution mechanism.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The tripodal N,N,O ligands 3,3-bis(3,5-dimethylpyrazol-1-yl)propionic acid (Hbdmpzp) (1) and 3,3-bis(pyrazol-1-yl)propionic acid (Hbpzp) (2) form the “missing link” between the well-known bis(pyrazol-1-yl)acetic acids and related ligands with a longer “carboxylate arm”. To illustrate the reactivity of this ligand, manganese and rhenium complexes bearing the ligand bdmpzp are reported. The complexes are compared to related compounds bearing other tripod ligands such as bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza) and 3,3-bis(1-methylimidazol-2-yl)propionate (bmip). Spectroscopic and structural data are used as a basis for comparison, as well as DFT calculations. Both ligands 1 and 2 and the complexes fac-[Mn(bdmpzp)(CO)3] (3) and fac-[Re(bdmpzp)(CO)3] (4) were characterised by X-ray crystallography.

An effective cyclic addition reaction of diastereomeric (R*)diphenyltin-3,5-di(tert-butyl)-1,2,4-triphosphole derivatives 6 a-c (R* = (-)-cis-myrtanyl (a), (-)-trans-myrtanyl (b), m-(2-bornyl-2-ene)phenyl (c) with two equivalents of tert-butylphosphaalkyne 1 leads to 1:1 mixtures of diastereomeric stannylated pentaphosphadeltacyclene derivatives 7 a-c with seven stereogenic centers in the cage unit. The (-)-cis-myrtanyl derivative 7 a could be separated into its diastereomers; destannylation of diastereomer 7 a(RR) led to the P-H cage 8 as a pure enantiomer. Circular dichroism (CD) spectroscopy of the pure diastereomer 7 a(RR) and the enantiomer 8 give evidence for identical stereoisomers of the P(5)-deltacyclene cage units and prove a strong dominance of the chiral cages over the chiral auxiliary groups with respect to their chiroptical properties. Absolute X-ray structure investigations of the majority of the compounds presented in the paper reveal the details of the stereochemistry of the asymmetric P-C cage units. In this paper we demonstrated for the first time a general preparative route to stereochemically fully defined asymmetric P-C cage compounds by separation of diastereomers and replacement of the chiral auxiliary group.

2,4,5-Tri(t-butyl)-1,3-diphospholyl sodium salt (2a) and 3,5-di(t-butyl)-1,2,4-triphospholyl sodium salt (3a) react with ZrCl4 and CpZrCl3 to form (η5-2,4,5-tri(t-butyl)-1,3-diphospholyl)ZrCl3 (4), Cp(η5-2,4,5-tri(t-butyl)-1,3-diphospholyl)ZrCl2 (5), and Cp(η5-3,5-di(t-butyl)-1,2,4-triphospholyl)ZrCl2 (6) in the complete absence of water, respectively. Surprisingly, bent sandwich complex 6 exhibits the NMR spectroscopic characteristics of a hindered ring ligand rotation but the cyclopentadienyl ligand of 5 rotates freely in the NMR time scale in spite of the superior space demand of its 2,4,5-tri(t-butyl)-1,3-diphospholyl ligand. This contradiction is discussed on the basis of an attractive interligand P–C interaction between homo- and heterocyclic π-ligands, which is stronger for 6. Water even in trace amounts present in the reaction mixture changes the course of the reactions completely. No zirconium π-complexes are accessible this way, but only oligo- or polycyclic organophosphorus compounds. Compound 3a and ZrCl4 form the asymmetric tricyclic P6(t-BuC)4H2 isomer 8 with two P C double bonds as a dimer of 1,2,4-triphosphol. It is accompanied by small amounts of HCl addition product 9, where one of the P C double bonds is eliminated. Compound 8 contains six, and 9 eight stereogenic centers, but both form one pair of enantiomers each only. A single stereoisomer of P6(t-BuC)4H2 cage 10 is formed if (1-trimethylstannyl)-3,5-di(t-butyl)-1,2,4-triphosphol 3b is used as the P3(t-BuC)2 source in combination with Cp∗ZrCl3 in the presence of trace amounts of water. Compound 10 is a meso-compound, which is composed by dimerization of either two homochiral units of (R)-3,5-di(t-butyl)-1,2,4-triphosphol 3cR or by two units of its S-enantiomer 3cS. No trace of cyclic addition products has been identified, which would represent the heterochiral combination of enantiomers 3cR + 3cS. P2- and P3-zirconocene dichloride derivatives 5 and 6 have been tested as Ziegler–Natta alkene oligomerization catalysts. Both are catalytically active with 1-hexene as the substrate, but cannot compete with the activity of the phosphorus-free original catalyst Cp2ZrCl2.

Octahedral iron(II) complexes of a unique pyridine-derived tetrapodal pentadentate polyamine ligand, 2,6-C5H3N(CMe[CH2NH2]2)2, show temperature-dependent spin crossover (SCO) depending on the nature of a sixth monodentate ligand L (imidazol or pyridine derivative). For L = 1-methylimidazol, the redox behaviour of the complex, as determined by cyclic voltammetry, suggests an accompanying ligand exchange. Pyridine-4-thiol and the disulphides: 4-(2-methyldisulphanyl)pyridine, 4-(2-hexadecyldisulphanyl)pyridine and 1,2-bis([pyridine-4-yl]methyl)disulphane, were studied as mono-dentate ligands L, with a view to enable chemisorption of iron(II) complexes on a gold surface. In the case of pyridine-4-thiol, the participation of the thiolate functional group in iron coordination is difficult to suppress, whereas the disulphides enter into yet unrecorded redox chemistry with iron(II), yielding a di-iron(III) complex containing a persulphide bridge (S 2 2− ).

The reaction of diphenyltin dichloride with enantiopure Grignard reagents prepared in situ leads to diphenyltin chlorides 7a–e, which contain chiral organyl substituents. The 2-bornyl derivative 7a forms a mixture of exo and endo isomers and the (–)-menthyl derivative 7b yields a mixture of epimers, whereas the cis- and trans-myrtanyl complexes 7c and 7d and the m-(2-bornyl-2-ene)phenyl species 7e form only one enantiomer as the tin atom is separated from the next stereogenic centre by a methylene or m-phenylene group. The target chirally modified 1-(triorganylstannyl)-1,2,4-triphospholes 2a–e are accessible from 7a–e by treatment of the latter with the salt (3,5-di-tert-butyl-1,2,4-triphospholyl)sodium (Na5) in good yield. As for 7c–e, complexes 2c–e exhibit enantiopure organyl tin substituents that combine with the planar chiral 1,2,4-triphosphole moiety to form diastereomers. X-ray diffraction studies on crystalline phases of 2a,b,d and 7b,c confirm the stereochemical interpretations of their spectroscopic data with the help of absolute structure parameter determinations. Dynamic NMR spectroscopy experiments with these compounds demonstrate for the first time a facile stannyl group shift between the two adjacent P atoms (P1 and P2) of the heterocycles that includes ring inversion through a planar transition state (Ti). In line with the NMR spectroscopic results for 2a–e, density functional calculations with the simplified model compound (trimethylstannyl)-1,2,4-triphosphole (9) point to 1-(trimethylstannyl)-1,2,4-triphosphole (9a) as the global energetic minimum for 9 and an almost isoenergetic 1,2-shift and ring inversion as the main epimerisation processes of the two enantiomers of 9a.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Saponification of the bis(carbamic acid ester) 1,3-C6H4(CMe2NHCO2Me)2 (1), made by the addition of methanol to commercial 1,3-C6H4(CMe2NCO)2, yielded the meta-phenylene-based bis(tertiary carbinamine) 1,3-C6H4(CMe2NH2)2 (2). Dinuclear [{(η4-1,5-C8H12)RhCl}2{μ-1,3-C6H4(CMe2NH2)2}] (3) resulted from the action of 2 on [{(η4-1,5-C8H12)Rh(μ-Cl)}2] in toluene. Combination of 2 with PdCl2 or K2[PdCl4] gave the dipalladium macrocycle trans,trans-[{μ-1,3-C6H4(CMe2NH2)2}2(PdCl2)2] (4) along with cyclometalated [{2,6-C6H3(CMe2NH2)2-κN,κC1,κN′}PdCl] (5). Substitution of PEt3 for the labile chlorido ligand of 5 afforded [{2,6-C6H3(CMe2NH2)2-κN,κC1, κN′}Pd(PEt3)]Cl (6). The crystal structures of the following compounds were determined: bis(carbamic acid ester) 1, ligand 2 as its bis(trifluoroacetate) salt [1,3-C6H4(CMe2NH3)2](O2CCF3)2, 2 · (HAcf)2, complexes 3 and 6, as well as 1,3-C6H4(CMe2OH)2 (the diol analogue of 2).

Insertion of an electron-deficient alkyne A-C[triple bond]C-A (A = CO2Me) into the C-L+ bond of an acyl-onio salt R-C(O)-L+ (R = Ar, OAlk; L = 4-dimethylaminopyridine, PPh3) has for the first time been achieved in the presence of catalytic amounts of the nucleophile L. For R = OMe, a second insertion of the alkyne was observed. X-ray structures were obtained for a number of such beta-oniovinylation products. Depending on reaction conditions, preferentially E- or Z-stereochemistry was observed, the Z-isomer being the thermodynamically more stable. A mechanism for this novel insertion reaction is presented which accounts for the topology of the products and rationalizes the observed stereochemistry. The beta-onio-activated Michael systems thus generated represent a virtually unexplored class of compounds. The onio substituent in such compounds can be selectively replaced by a number of nucleophiles. Thus a series of Michael systems with donor functions in the beta-position is easily synthesized. These compounds represent a source for useful further transformations, for example, cyclizations to quinolones, thiochromones, and pyrazoles.

The reaction of diphenyldiazomethane with [((t-BuArO)3tacn)UIII] (1) results in an eta(2)-bound diphenyldiazomethane uranium complex. This complex exhibits unusual electronic properties as a charge-separated species with a radical anionic open-shell ligand, [((t-BuArO)3tacn)UIV(eta2-NNCPh2)] (2). Treating Ph2CN2 with a uranium complex that contains a sterically more demanding adamantane functionalized ligand, [((AdArO)3tacn)UIII] (3) results in an unprecedented C-H activation and nitrogen insertion to produce a five-membered heterocyclic indazole complex, [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] (5). X-ray crystallography and spectroscopic characterization of these two compounds show that the [((t-BuArO)3tacn)UIV(eta(2)-NNCPh2)] compound is a U(IV) complex with a radical anionic ligand, whereas [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] is a U(IV) f (2) species with a closed-shell ligand.

Iron(II) complexes of the type [Fe(L)(NCS)2] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)2] [tmpa = tris(2-pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)2], [Fe(pmap)(NCS)2], and [Fe(tepa)(NCS)2] [pmea = N,N-bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine, pmap = N,N-bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine, and tepa = tris[2-(2-pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Möβbauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl-alkylamine ligands is clearly demonstrated.

Reaction of bis(1,3-diketone) H 2 L 1 in the presence of cesium acetate with magnesium acetate yielded crystalline one-dimensional coordination polymer rac-(2) n . The {2}-metallacryptand core [Mg 2 (L 1 ) 3 ] 2- is composed of two magnesium centres linked through three bis(1,3-diketo) dianions (L 1 ) 2 -. These {2}-metallacryptands are homochiral with either (A,A)-iac or (Λ,Λ)-fac stereochemistry at the magnesium centres, and they are capable to host a cesium ion in the cavity. Charge compensation of the thus formed {2}-metallacryptates (Cs⊂(Mg 2 (L 1 ) 3 ]) - is achieved through extra external cesium ions to give the neutral self-complementary building blocks [{Cs⊂[(Δ,Δ)/(Λ, Λ ) -Mg 2 (L 1 ) 3 ]}Cs], which aggregate end-on across the external cesium ions to give the homochiral one-dimensional strings [{Cs⊂[(Δ,Δ )-Mg 2 (L 1 ) 3 ]}Cs] n [Δ-(2) n ] and [{Cs⊂[(Λ,Λ)-Mg 2 (L 1 ) 3 ]}Cs) n [A-(2) n ], which are packed in the crystal in alternating homochiral layers. However, reaction of bulkier phenyl-substituted bis(1,3-diketone) H 2 L 2 instead of methyl-substituted H 2 L 1 with cesium or rubidium acetate and magnesium, cobalt or zinc acetate yielded the meandering polymer meso-{[({M 1 ⊂[(Δ,Δ)-M 2 2 -(L 2 ) 3 ]}M 1 end) ({M 1 ⊂[Λ,Λ]-M 2 2 (L 2 ) 3 ]}M 1 side )][({M 1 ⊂[(Λ,Λ)-M 2 2 (L 2 ) 3 ]}M 1 end )({M 1 end )([(Δ,Δ)-M 2 2 (L 2 ) 3 ]}M 1 side )]} n [meso-(3) n ] (M 1 = Cs + , Rb+; M 2 = Mg 2+ , Co 2+ , Zn 2+ ). In this case, the (2)-metallacryptates (M 1 ⊂ [(Δ,Δ/Λ,Λ)-M 2 2 (L 2 ) 3 ]}- are linked by only one cesium ion end-on to give the fragments meso-[({M 1 ⊂[(A,A)-M22(L2)3]}M 1 end )((MlC[(A,A)-M 2 2 (L 2 )3]}M 1 side )], which are connected by the second cesium ions side-on. The one-dimensional meander strands of isostructural mesa-(3) n are packed in the crystal in parallel. Reaction of 4 equiv. of zinc acetate and 1 equiv. of cesium or rubidium acetate with 2 equiv. of H 2 L 2 afforded the {M 1 ⊂[Zn 2 (L 2 ) 2 OAc)) cryptates 4a,b (M 1 = Cs + , Rb + ).

The P 2 /N 2 -coordinated cis-dihydridoiridium(III) chelate complexes (OC-6-13)-[IrH2(H2NnNH2)(PR3) 2 ]BF 4 [PR 3 = PPh 3 , H 2 N∩NH 2 = 1,2-(H 2 N) 2 C 6 H 4 (la); (1R,2R)-(H 2 N) 2 C 6 H 10 {{R,R)-dach} (1b); (R)-2,2'-diamino-1,1'-binaphthyl {(R)-dabin) (1c); PR 3 = PiPr 3 , H 2 NnNH 2 = (R,R)-dach (2a), (R)-dabin (2b); PR 3 = PCy 3 , H 2 N∩NH 2 = (R)-dabin (3)] were obtained by treating the respective diamine ligands with labile precursors such as [IrH2(OCMe2)2(PPh3)2]BF4, [{η 4 -1,5-C 8 H 12 )Ir(PPh 3 ) 2 ]BF 4 , or [IrH 5 (PR 3 ) 2 ]/HBF 4 (R = iPr, Cy). While oxidative addition of HCl to [(η 4 -1,5-C 8 H 12 )Ir(S,S)-bdpcp}]BF 4 [(S,S)-bdpcp = (1S,2S)-(Ph 2 P) 2 C 5 H 8 ] yields the usual mononuclear adduct [(η 4 -1,5-C 8 H 12 )Ir(H)(Cl){(S,S)-bdpcp}]BF 4 (4), similar treatment of [(η 4 -1,5-C 8 H 12 )Ir{(R)-binap)]BF 4 furnishes the triply chlorido-bridged diiridium complex [((R)-binap} 2 Ir 2 H 2 (μ-Cl)3]BF4 (5). Opening of the μ-Cl bridges of 5 by N,N nucleophiles was used to synthesise the three diamine/(R)-binap complexes [Ir(H)(Cl)-(H2NnNH2){(R)-binap}]BF4 [H 2 NNH 2 = (1R,2R)-H 2 NCH(Ph)CH(Ph)NH 2 {(R,R)-dpen} (6a), (R,R)-dach (6b), and H 2 NCMe 2 CMe 2 NH 2 {tmen} (6c). Whereas the dihydrides [IrH 2 ((R,R)-dach}(PR3) 2 ]BF 4 and [IrH 2 {(R)-dabin}-(PR 3 ) 2 ]BF 4 (R = iPr, Ph) are only poor (pre)catalysts for the enantioselective hydrogenation of acetophenone, complexes 6a-c catalyze the formation of 1-phenylethanol in good enantiomeric excess [ee max = 82-84 % (S)] in the presence of base. The crystal structures of la, 4, and 5 have been determined.

The bridge-opening reaction of [(η 4 -C 8 H 12 ) 2 Rh 2 (μ-Cl) 2 ] with chiral and achiral β-amino alcohol nucleophiles gave mononuclear complexes [(η 4 -C 8 H 12 )RhCl{HN(R)∩OH-κN}] containing the amino alcohol ligands in N-monodentate coordination; HN(R)nOH = ethanolamine (4), 2-amino-2-methyl-1-propanol (5), and either enantiomer of (R)-, (S)-2-amino-3-methyl-1-butanol (D-, L-valinol) [(R)-6, (S)-6], (R)-, (S)-2-pyrrolidinemethanol (D-, L-prolinol) [(R)-7, (S)-7], (1S,2R)-, (1R,2S)-2-amino-1-phenyl-1-propanol (D-, L-norephedrine) [(1S,2R)-8, (1R,2S)-8], and (1S,2R)-, (1R,2S)-cis-1-amino-2-indanol [(1S,2R)-9, (1R,2S)-9]. Coordination of the free hydroxy function of the N,O ligands was brought about by both dehydrochlorination, which furnished the neutral valinolato chelate complex [(η 4 -C 8 H 12 )Rh{(S)-H 2 NCH(CHMe 2 )CH 2 O-κN,κO}], (S)-10, and by precipitation of the metal-bound chloride with TlO 3 SCF 3 to produce ionic chelate complexes [(η 4 -C 8 H 12 )Rh{HN(R)∩OH-KN,κO}]O 3 SCF 3 ; HN(R)∩OH = 2-amino-2-methyl-1-propanol (11), (S)-2-amino-3-methyl-1-butanol [(S)-12], (S)-2-pyrrolidinemethanol [(S)-13], (1R,2S)-2-amino-1-phenyl-1-propanol [(1R,2S)-14), and (1R,2S)-cis-1-amino-2-indanol [(1R,2S)-15]. Except for only two in situ characterized [{(R)-binap}Rh(H 2 N∩OH-κN,κO)] + cations, where H 2 N∩OH = L-valinol or L-norephedrine, no compound containing the various N,O ligands in addition to mono- or bidentate phosphanes could be prepared. In contrast, the P 2 /N 2 -coordinated chelate complexes [{(R)-binap}Rh-(H 2 N∩NH 2 )]BF 4 with H 2 N∩NH 2 = H 2 NCMe 2 CMe 2 NH 2 [(R)-(16)], (R,R)-H2NCH(Ph)CH(Ph)NH2 [(R),(R,R)-17], and (R,R)-1,2-(H 2 N) 2 C 6 H 10 [(R),(R,R)-18] were easily obtained from [(η 4 -C 8 H 12 )Rh{(R) -binap}]BF 4 and 1,2-diamines. Oxidative addition of HCl to (R),(R,R)-17 produced trans-[{(R)-binap}-Rh(H)(Cl){(R,R)-H2NCH(Ph)CH(Ph)NH 2 }]BF 4 [(R),(R,R)-19]. If activated by strong base (KOH), (R),(R,R)-17 and (R),(R,R)-19 acted as moderately active and enantioselective catalysts for the reduction of acetophenone by both direct and transfer hydrogenation: ee max : 71% (S). The crystal structures of 4, (S)-6, (R)-7, (1R,2S)-8, (S)-10, (1R,2S)-14, (1R,2S)-15, (R)-16, (R),(R,R)-17, and two alcohol/alcoholato addition compounds, [(η 4 -C 8 H 12 )Rh(H 2 NCMe 2 CH 2 O-κN,κO)][(η 4 -C 8 H 12 )Rh(H 2 -NCMe 2 CH 2 OH-KN,KO)][(η 4 -C 8 H 12 )RhCl 2 ] [1·2], and [(η 4 -C 8 H 12 )Rh(H 2 NCMe 2 CH 2 O-κN,κO)][(η 4 -C 8 H 12 )Rh(H 2 - NCMe 2 CH 2 OH-κN,κO)]Cl [1·3], were determined.

The new pyridine-based N∩N∩N tridentate ligand 2,6-C5H3N(CMe2NH2)2 (1) was synthesized by the treatment of 2,6-pyridinedicarbonitrile with an excess of the organocerium reagent in situ generated from CeCl3 and methyllithium in THF. The reaction of 1 with [RuCl2(PPh3)3] in THF at ambient conditions afforded (OC-6-23)-[RuCl{2,6-C5H3N(CMe2NH2)2}(PPh3)2]Cl (2). The corresponding dimethyl sulfoxide complex [RuCl{2,6-C5H3N(CMe2NH2)2}{S(O)Me2}2]Cl (3) was isolated as a mixture of the (OC-6-23) and (OC-6-32) stereoisomers 3a and 3b from the reaction between 1 and (OC-6-22)-[RuCl2{S(O)Me2}3(OSMe2)] in toluene at 80 °C. A prolonged interaction in toluene at reflux temperature gave isomerically pure 3a. The metal trichloride hydrates MCl3 · xH2O (M = Ru, Rh, Ir; x ≅ 2–4) produced mer-[RuCl3{2,6-C5H3N(CMe2NH2)2}] (M = Ru: 4; Rh: 5; Ir: 6), when combined with 1 in refluxing ethanol. The crystal structures of the following compounds were determined: ligand 1 and complexes 2–5 as addition compounds 2 · CH2Cl2, 3a · C7H8, 4 · EtOH and 5 · 2 1 2 DMF .

Usually, ortho lithiation of Kagan's template 1 and quenching with electrophiles leads highly diastereoselectively to planar-chiral 1,2-disubstituted ferrocenes. Surprisingly, lithiation of 1 with lithium diisopropylamide (LDA) followed by addition of paraformaldehyde afforded regioisomer (+)-{[S(S)]-[4-(2-hydroxyethyl)phenyl]sulfinyl}ferrocene (2), which was converted to (+)-{[S(S)]-{4-{2-[(methylsulfonyl)oxy]ethyl}phenyl}sulfinyl}ferrocene (3) (Scheme 1). The desired diastereoisomer (l)-1-(hydroxymethyl)-2-(p-tolylsulfinyl)ferrocene (5) in turn could also be obtained by ortho lithiation of 1 with LDA but by quenching with DMF to yield aldehyde 4 first, which then was reduced with NaBH4 to 5. Finally, target compound (l)-1-[(dimethylamino)methyl]-2-(p-tolylsulfinyl)ferrocene (6) was obtained by substitution of the OH group of 5 under mild conditions or directly by ortho lithiation of 1 with lithio-2,4,6-triisopropylbenzene (=2,4,6-triisopropylphenyl)lithium; LTP) followed by quenching with N,N-dimethylmethyleneiminium chloride. At low temperatures, reaction of 1 with LDA leads, via the preferred diastereoisomeric transition state ‘exo’-7 and under extrusion of a (diisopropylamine)lithium complex of type 8, in a highly selective manner, to diastereoisomeric ortho-lithiated chelate (l)-9 (Scheme 2). The reaction of 1 to 2 is explained by a rearrangement of (l)-9 to {[S(S)] [4-(lithiomethyl)phenyl]sulfinyl}ferrocene 10, which is acid-catalyzed by coordinated diisopropylamine in complexes of type 8. This rearrangement is not observed if LTP is used as base or, in case LDA is applied, if the electrophile is sufficiently reactive at low temperatures.

Seven-coordinate manganese(II) complexes [Mn(L)(H2O)2]2+, where L represents an equatorial pentadentate macrocyclic ligand with five nitrogen donor atoms, were studied with regard to their acid-base properties, water-exchange rate constants, and corresponding activation parameters (DeltaH, DeltaS, and DeltaV). Three of the studied complexes without imine bonds in the macrocyclic ligand are proven superoxide dismutase (SOD) mimetics. Their water-exchange parameters were compared with those of the imino groups containing complex [Mn(L1)(Cl)2] (dichloro-2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]-octadeca-1(18),2,12,14,16-pentaenemanganese(II)), which does not show SOD activity. In addition the X-ray crystal structure of a new complex, dichloro-2,6-bis[1-(2-(N-methylamino)ethylimino)ethyl]pyridine-manganese(II) [Mn(L2)(Cl)2], which is the acyclic analog of [Mn(L1)(Cl)2], is reported. Stability constants of the complexes and the pKa values of the ligands were measured by potentiometric titration. The titrations of [Mn(L1)(H2O)2]2+ and [Mn(L2)(H2O)2]2+ led to complicated species distribution curves because of their ligands containing imine bonds. Water exchange was measured by temperature- and pressure-dependent 17O NMR techniques. In addition to the measurements on [Mn(EDTA)(H2O)]2- and its derivatives, this is the only study of water exchange on seven-coordinate manganese complexes. The water exchange rate constants vary between 1.6 x 107 s-1 and 5.8 x 107 s-1 at 25 degrees C and are mainly controlled by the pi-acceptor abilities of the ligands. The exchange rate constant of the diaqua-1,4,7,10,13-pentaazacyclopentadecanemanganese(II) [Mn([15]aneN5)(H2O)2]2+ complex seems to be even higher but could not be exactly determined. On the basis of the obtained activation parameters, the exchange mechanism of the studied seven-coordinate manganese(II) complexes follows a dissociative pathway (Id mechanism). DFT calculations (UB3LYP/LANL2DZp) were performed to obtain the energy required for the dissociation of the coordinated water molecule, that is, the energy difference between the starting seven-coordinate complex and a six-coordinate intermediate. The results have been discussed in terms of the catalytic mechanism of the proven SOD mimetics.

N,N,N',N'-Tetrakis(2-pyridylmethyl)benzene-1,3-diamine (1,3-tpbd), a bis(tridentate) ligand, its protonated derivative, [1,3-tpbdH 2 ] 2+ , and a series of new dinuclear complexes (Fe 2 (1,3-tpbd)(CH 3 CN) 6 ](ClO 4 ) 4 ·(CH 3 CN) 2 ·(H 2 O) 0.5 (1), [Fe 2 (1,3-tpbd)(DMF) 6 )(ClO 4 ) 4 (2), [Ni2(1,3-tpbd)(DMF) 6 ](ClO 4 )4 (3), [Zn 2 (1,3-tpbd)(CH3CN)2(SO 3 CF 3 ) 2 (H 2 O)](SO 3 CF 3 )2 (4), [Zn 2 (1,3-tpbd)-Cl 4 ]·H 2 O (5), [CuZn(1,3-tpbd)Cl 4 ] (7) and the tetranuclear copper(II) complex [Cu2(1,3-tpbd)2(H20)2](ClO 4 ) 4 ·2H 2 O (8) have been prepared and structurally characterized. Complex 8, a so called "dimetallocyclophane", interestingly only formed in the presence of zinc ions and not when copper(II) ions were mixed stoichiometrically (1:1 mixtures) under aerobic conditions. Theoretical calculations provide evidence for the formation of a side-on dinuclear peroxido copper complex during the oxidation of the (1,3-tpbd)copper(I) complex. A possible reaction product, the dinuclear copper complex [Cu 2 (2,6-tpcd)(H 2 O)-(Cl)](ClO 4 ) 2 .2H 2 O (9) of a phenolate derivative of 1,3-tpbd was synthesized and structurally characterized independently from oxidation reactions from copper(II) perchlorate and the ligand 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol.

A combinatorial library of 180 tetracycline analogs was generated by solution phase parallel synthesis applying a consecutive Diels–Alder strategy. Chemical methodology suitable for three-dimensional solution phase parallel synthesis was developed that enabled us to generate a collection of potential TetR inducers. The synthesis was built on cross-conjugated trienes as central building blocks facilitating two consecutive cycloaddition processes with different dienophiles. Upon sequential exposure to naphthoquinone and maleimide derivatives, the generation of a carbocyclic skeleton of type 2 incorporating the diversity elements R1–R5 was envisaged.