Iris M. Müller

A platinum-catalyzed annulation reaction leading to medium-sized rings

A platinum-catalyzed domino process with intermediate benzopyrylium cations reaches its optimum utility in the formation of 7- and 8-membered rings. With iron(III) chloride, a tetracyclic product is isolated, derived from an oxidative transformation of a metal-carbene intermediate.

Complex Formation of NiII, CuII, PdII, and CoIII with 1,2,3,4‐Tetraaminobutane

Complex formation of the two tetraamine ligands (2S,3S)-1,2,3,4-tetraaminobutane (threo-tetraaminobutane, ttab) and (2R,3S)-1,2,3,4-tetraaminobutane (erythro-tetraaminobutane, etab) with Co(III), Ni(II), Cu(II), and Pd(II) was investigated in aqueous solution and in the solid state. For Ni(II) and Cu(II), the pH-dependent formation of a variety of species [Mn(II)xLyHz](2x+z)+ was established by potentiometric titrations and UV/Vis spectroscopy. In sufficiently acidic solutions the divalent cations formed a mononuclear complex with the doubly protonated ligand of composition [M(H2L)]4+. An example of such a complex was characterized in the crystal structure of [Pd(H2ttab)Cl2]Cl2.H2O. If the metal cation was present in excess, increase of pH resulted in the formation of dinuclear complexes [M2L]4+. Such a species was found in the crystal structure of [Cu2(ttab)Br4].H2O. Excess ligand, on the other hand, lead to the formation of a series of mononuclear bis-complexes [Mq(HxL)(HyL)](q+x+y)+. The crystal structure of [Co(Hetab)2][ZnCl4]2Cl. H2O with the inert, trivalent Co(III) center served as a model to illustrate the structural features of this class of complexes. By using an approximately equimolar ratio of the ligand and the metal cation, a variety of polymeric aggregates both in dilute aqueous solution and in the solid state were observed. The crystal structure of Cu2(ttab)3Br4, which exhibits a two-dimensional, infinite network, and that of [Ni8(ttab)12]Br16.17.5H2O, which contains discrete chiral [Ni8(ttab)12]16+ cubes with approximate T symmetry, are representative examples of such polymers. The energy of different diastereomeric forms of such complexes with the two tetraamine ligands were analyzed by means of molecular mechanics calculations, and the implications of these calculations for the different structures are discussed.

Alkylcycloarsoxanes and alkylcycloarsathianes—ambidentate macrocyclic ligands of variable metal-mediated ring size

Abstract A comprehensive account of the coordination chemistry of alkylcycloarsoxanes (RAsO) n and alkylcycloarsathianes (RAsS) n is presented. The former ambi- and multidentate ligands are characterised by their unique ability to undergo metal-mediated ring expansion to n =5,6 or 8. Cyclotetramers, -pentamers and hexamers of their sulphur analogues have also been stabilised as intact species in metal coordination spheres. At elevated temperatures As–S bond cleavage and metal-assisted reassembly afford novel linear and macrocyclic As–S ligands. Cyclotetramers (RAsO) 4 can be employed for the self-assembly of copper(I) halide based porous lamellar and framework coordination polymers capable of hosting alkali cations or polar molecules as guests.

The Coordination Chemistry ofcis-3,4-Diaminopyrrolidine and Related Polyamines

cis-3,4-Diaminopyrrolidine (cis-dap), trans-3,4-diaminopyrrolidine (trans-dap), cis-1,2-cyclopentanediamine (cis-cptn), and trans-1,2-cyclopentanediamine (trans-cptn) have been prepared in multigram quantities. The complexation of these ligands and of 3-aminopyrrolidine (ampy) with NiII, CuII, ZnII, and CdII has been studied in solution by means of potentiometric and spectrophotometric titrations. The complexes of the triamines cis-dap and trans-dap show a pronounced tendency to form protonated species such as [MII(HL)]3+, [MII(HL)2]4+, and [MII(HL)L]3+, indicative of a bidentate coordination mode of the ligand L. The UV/Vis spectra of the corresponding CuII complexes further confirmed bidentate coordination with trans-CuN4 geometry. The overall stabilities of the bis complexes [ML2]2+ decrease in the order cis-cptn > cis-dap > trans-cptn > ampy > trans-dap. The considerably lower stabilities of the ampy complexes as compared to the corresponding cis-dap complexes indicate metal binding to the two primary amino groups of the latter ligand. This was supported by molecular mechanics calculations (CuII and CoIII complexes) and confirmed by single-crystal X-ray diffraction studies of [Pt(Hcis-dap)Cl4]Cl·H2O, [Pd(Hcis-dap)2](ClO4)4·2H2O, and [Cu(Hcis-dap)2(OH2)2](SO4)2·3.5H2O − 2x H+ + x Cu2+ with 0.01 ⩽ x ⩽ 0.11. For the diamine ligands, coordination through the two exocyclic amino groups or through one exocyclic and one endocyclic amino group was established from the X-ray structure analyses of [Ni(cis-cptn)2](ClO4)2 and [Cu(3R-ampy)(3S-ampy)](ClO4)2, respectively. The crystal structure determination of [Co(cis-dap)(tach)][ZnCl4]Cl·C2H5OH (tach = cis-1,3,5-cyclohexanetriamine) revealed tridentate, facial coordination of cis-dap in this particular complex. However, the structural parameters of the [Co(cis-dap)(tach)]3+ moiety indicate significant strain for this coordination mode. The coordinating properties of the ligand cis-dap are compared with those of other aliphatic and alicyclic triamines.

Struktur und Koordinationsverhalten des sterisch anspruchsvollen Phenylcycloarsoxans

Phenylcycloarsoxan kristallisiert in tetramerer Form als [cyclo-(C6H5AsO)4] (1) in boat-chair Konformation aus. Bei Umsetzungen mit CuI in Benzonitril kommt es zur Ausbildung von Koordinationspolymeren. In [(CuI · C6H5CN){cyclo-(C6H5AsO)4}] (2) wird der strukturdirigierende sterische Einflus der Phenylringe deutlich. Durch Reaktionen mit Ubergangsmetallcarbonylen M(CO)6 (M = Cr, Mo) wird die Fahigkeit zur metallassistierten Ringerweiterung nachgewiesen. In den Komplexen [{M(CO)3}2{cyclo-(C6H5AsO)6}] mit M = Cr (3), M = Mo (4) liegen zwolfgliedrige As–O-Ringe vor, die alternierend an zwei M(CO)3-Einheiten gebunden sind. Structure and Coordination Chemistry of Sterically Demanding Phenylcycloarsoxane Tetrameric phenylcycloarsoxane (C6H5AsO)41 exhibits a boat-chair-conformation in the solid state. Its reaction with CuI in benzonitrile leads to the formation of coordination polymers. [(CuI · C6H5CN){cyclo-(C6H5AsO)4}] (2) underlines the structure-directing steric requirements of the phenyl side chains. Treatment of 1 with M(CO)6 (M = Cr, Mo) confirms its capability to undergo metal-mediated ring expansion. In [{M(CO)3}2{cyclo-(C6H5AsO)6}] with M = Cr (3) and M = Mo (4), twelve membered As–O-rings are stabilised by the participation of alternating As atoms in the coordination spheres of opposite facial transition metal carbonyl fragments M(CO)3.

Ligand Synthesis and Metal Complex Formation of 1,2,3-Triaminopropane

A series of linear primary polyamines H2N–CH2–(CH–NH2)n–CH2–NH2 (1 ≤ n ≤ 3) was prepared from the corresponding polyalcohols. The polyamines were isolated as HCl adducts and the acidity constants in aqueous solution were determined. The crystal structure of the fully protonated tetraamine (n = 2) was elucidated by an X-ray diffraction study. Complex formation of the triamine (n = 1) with Ni2+, Cu2+, Zn2+, Cd2+ was re-investigated in aqueous solution. The pH-dependent formation of a variety of species MxLyHz was established by potentiometric titrations and was compared with previous reports. The crystal structure of the Cu complex [CuL2]Cl2 exhibited a chain structure with a five-coordinate CuII centre in which two amino groups of the triamine ligands are coordinated to one Cu centre, while the third amino group of one of the ligands is bonded to a neighbouring Cu atom. The compound shows weak antiferromagnetic coupling interactions between the CuII centres within the chain.

T-symmetrical icosahedra: A new type of chirality in metal complexes

A homoleptic metal complex with four tripodal tridentate ligands can have chiral tetrahedral T symmetry. An example of such a complex has been prepared, and the proposed highly symmetric, but chiral structure (see schematic representation, MP=mirror plane, R=NHCH2 PH) has been confirmed.

Tetramethylcyclotetraarsoxane Bridging of Copper(I) Halide Units Cu6Br6, Cu2I2, [Cu6I8]2-, and∞1[Cu3I4-] in Porous Coordination Polymers

The polymeric compounds [{Cu2I2(C6H5CN)2[cyclo-(CH3AsO)4]} · C6H5CN] (1) and [Cu6Br6(C6H5CN)4{cyclo-(CH3AsO)4}] (2) may be prepared by reaction of the copper(I) halide with methylcycloarsoxane (CH3AsO)n in benzonitrile at 100 °C. 1 contains four-membered (CuI)2 rings, 2 tricyclic Cu6Br6 units, that are connected through bridging (CH3AsO)4 ligands into infinite chains. π–π Stacking of terminal C6H5CN ligands from parallel chains leads to the construction of porous frameworks, whose cavities are large enough in the case of 1 to accommodate guest C6H5CN molecules. In the presence of CsI, the self-assembly reaction of CuI with (CH3AsO)4 in H2O–CH3OH–CH3CN (at 20 °C) or CH3CN (at 130 °C) affords [Cs(H2O)2][Cu3I4{cyclo-(CH3AsO)4}2] · 0.5 CH3OH (3) and Cs[Cu3I4{cyclo-(CH3AsO)4}2] (4), whose 1- and 2-dimensional anionic coordination polymers are linked together through respectively [Cs{cyclo-(CH3AsO)4-κ4O}2]+ and [Cs{Cu3I4-κ4I}{cyclo-(CH3AsO)4-κ4O}] sandwiches. Tetramethylcyclotetraarsoxan – Verbruckung von Kupfer(I)-Halogenideinheiten Cu6Br6, Cu2I2, [Cu6I8]2– und [Cu3I4–] in porosen Koordinationspolymeren Die polymeren Verbindungen [{Cu2I2(C6H5CN)2[cyclo-(CH3AsO)4]} · C6H5CN] (1) und [Cu6Br6(C6H5CN)4{cyclo-(CH3AsO)4}] (2) konnen durch Reaktion von Kupfer(I) Halogeniden mit Methylcycloarsoxan (CH3AsO)n in Benzonitril bei 100 °C hergestellt werden. 1 enthalt viergliedrige (CuI)2-Ringe, 2 tricyclische Cu6Br6-Einheiten, welche durch verbruckende (CH3AsO)4-Liganden zu unendlichen Ketten verbunden werden. π–π-Wechselwirkungen der terminalen C6H5CN-Molekule der parallel zueinander angeordneten Ketten fuhren zu der Ausbildung poroser Netzwerke. Die Hohlraume in 1 sind ausreichend gros, um Benzonitrilmolekule als Gast aufzunehmen. In Anwesenheit von CsI fuhrt die Reaktion von CuI mit (CH3AsO)n in einer H2O/CH3OH/CH3CN-Mischung bei 20 °C bzw. in Acetonitril bei 130 °C zu den ein- bzw. zweidimensionalen anionischen Koordinationspolymeren [Cs(H2O)2][Cu3I4{cyclo-(CH3AsO)4}2] · 0.5 CH3OH (3) und Cs[Cu3I4{cyclo-(CH3AsO)4}2] (4), welche durch [Cs{cyclo-(CH3AsO)4-κ4O}2]+ bzw. [Cs{Cu3I4-κ4I}{cyclo-(CH3AsO)4-κ4O}]-Sandwichkomplexe miteinander verbunden werden.

Porous copper(I) coordination polymers containing both the cyclic ion ligating agent methylcycloarsoxane (MeAsO)4 and rigid aromatic heterocycles as spacers

Porous lamellar networks with flexible [CuxIy{cyclo-(MeAsO)4}] ribbons bridged by either π–π stacked terminal benzonitrile ligands (x = y = 2), rigid p-diaminobenzene spacers (x = y = 2) or ionic [Cs{cyclo-(MeAsO)4}2]+ sandwiches (x = 3, y = 4) may be constructed by self-assembly from CuI and (MeAsO)n in the presence of the respective structure-directing agents.

CuX (X = Br, I) Oligomers and Polymerie Chains in Tetramethylcyclotetra- arsoxane-Bridged Networks [CunXn{cyclo-(CH3AsO)4}2] (n = 4, 6, 8)

Open lamellar structures 2∞[Cu4I4{cyclo-(CH3AsO)4}2] (1) and 2∞[{CuX(CuX · CH3CN)2}{cyclo-(CH3AsO)4}] [X = Br (2), X =I (3)] may be prepared by self-assembly from CuX and methylcycloarsoxane (CH3AsO)n in acetonitrile solution at 100- 130 °C. Whereas 1 contains CU4I4 oligomers consisting of three fused (Cul)2 rings, 2 and 3 exhibit infinite 1∞[CuX] single chains. An acceleration in the rate of heating between 20 and 100 °C from 2 °C h-1 to 5 °C h-1 for CuBr:As = 2:1 allows the isolation of the chain structure 1∞[{(CuBr)2(CuBr · CH3CN)2{cyclo-(CH3AsO)4}] (4), as an intermediate product on the reaction pathway to 2. Compound 4 contains cage-like [Cu4Br3(AsO)4] units in which the Cu and Br atoms belong to a 1∞[Cu2Br2] double chain containing fused (CuBr)3 six-membered rings.