Jose M. Martín-Alvarez

Luminescent Gold(I) Carbenes from 2-Pyridylisocyanide Complexes: Structural Consequences of Intramolecular versus Intermolecular Hydrogen-Bonding Interactions

Isocyanide [AuX(CNPy-2)] (X = Cl, C6F5, fluoromesityl, 1/2 octafluorobiphenyl) and carbene [AuX{C(NR1R2)(NHPy-2)}] (R1R2NH = primary or secondary amines or 1/2 primary diamine) gold(I) complexes have been synthesized and characterized. For X = Cl, the carbene complexes show aurophilic interactions. The fragment NHPy-2, formed in the carbenes, can give rise to intra- (for primary amines) or intermolecular (for secondary amines) hydrogen bonds, depending on the amine used. These bonds and contacts have been studied in the solid state and in solution. The intermolecular hydrogen bonds are split in an acetone solution, but the intramolecular ones, which close a six-membered ring, survive in solution. Except for the fluoromesityl derivatives, the carbene complexes display luminescent properties.

Liquid crystals based on halogold(I) complexes with 4-isocyano-4′alkoxybiphenyl derivatives

Rod-like complexes [AuCl(CNC6H4C6H4OCnH2n+1-p)](n= 4, 6, 8, 10, 12) have been prepared by reaction of [AuCl(tht)](tht= tetrahydrothiophene) with the isonitriles CNC6H4C6H4OCnH2n+1-p. Metathetical reactions with KBr or KI afford the corresponding [AuX(CNC6H4C6H4OCnH2n+1-p)](X = Br, I). While the free isonitriles are liquid crystals displaying nematic and (some of them) smectic A phases with a short range of existence at moderate temperatures (40–85 °C), their coordination to AuX (X = Cl, Br, I) produces a marked increase in the melting points of the materials, and also an enormous expansion of the range of existence of the mesophase. The order in the mesophase also increases and only the smectic A phase is formed in most of the complexes (for X = Cl, Br and n= 4 a nematic phase is also formed). All the biphenyl halogold(I) derivatives are mesogenic (except for X = I and n= 4) and their melting points decrease in the order I > Br > Cl. Ranges of mesophase of nearly 140 °C are attained. Most of the complexes decompose to the isotropic state (above 220 °C), but seem thermally stable below 200 °C.

Effects of isocyanide substituents on the mesogenic properties of halogeno(isocyanide)gold complexes : Calamitic and discotic liquid crystals

The liquid crystal behaviour of linear [AuX(CNC 6 H 4 OC n H 2n +1 )] (X=halogen) complexes is tuned by systematically changing the structure of the isocyanide ligand. The changes studied are lateral fluorination at the 2- and 3-positions of the phenyl ring and modification of the rod-like structure of the complexes by addition of two alkoxy chains at themeta positions. None of the free isocyanides used here are liquid crystals, but all the gold complexes prepared display mesomorphic properties, except iodo(2-fluoro-4-butoxyphenyl isocyanide)gold(i). The (2- and (3-fluorophenyl isocyanide)gold(i) complexes show smectic A mesophases, except the 2-fluoro derivative with n=6, which shows a nematic phase, while the (3,4,5-trialkoxyphenyl isocyanide)gold compounds display columnar hexagonal phases at room temperature.

Self‐Assembly of Pyramidal Tetrapalladium Complexes with a Halide at the Apex

Halide ions act as the template for the self-assembly of tetrapalladium macrocyclic pyramidal structures. These undergo easy inversion in which the halide ion apparently jumps across the macrocycle.

[Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N, I}], a palladium(II) complex with I- and organic iodide as trans ligands

The treatment of [Pd(dmba)(Fmes)(OH2)] with I2 leads to the formation of [Pd(Fmes)I{NMe2(CH2-o-C6H4-I)-N,I}]. The X-ray structure shows that a new halocarbon ligand, (2-iodobenzyl)dimethylamine has been formed and is acting as N–I chelate. The two different types of iodine, one iodide ligand and one organic iodide coordinated to Pd, are mutually trans and display essentially identical Pd–I distances.

Structural and dynamic studies in solution of anionic dinuclear azolato-bridged palladium(II) complexes

Abstract Detailed analysis of the 19F-NMR spectra of the boat-shaped complexes (NBu4)2[Pd2(μ-LL)2R4] (R=3,5-C6Cl2F3) (LL=pyrazolate (pz), 1; dimethylpyrazolate (dmpz), 2), HH- (head-to-head) and HT- (head-to-tail) (NBu4)2[Pd2(μ-LL)2R4] (LL=3-methylpyrazolate (mpz), 3; indazolate (indz), 4), (NBu4)2[Pd2(μ-dmpz)(μ-LL)R4] (LL=mpz, 6; indz, 7), and (NBu4)2[R2Pd(μ-LL)2Pd(C6F5)2] (LL=pz, 8; dmpz, 9) affords valuable structural information in solution. The substituents of the azolate ligands, which reduce the dihedral angle between the coordination planes of the two metals, place the endo Fortho of different PdR2 fragments at short distances. A single-crystal X-ray structure has been obtained for compound HT-4 and the distances between Fortho compared with that calculated from the NMR spectra. The study of the dynamic processes for these complexes reveals the involvement of different mechanisms such as: (a) rotation of the R groups, (b) boat–boat inversion of the six-membered Pd(μ-LL)2Pd ring, (c) σ-1,2-metallotropic shift, and (d) associative exchange of PdR2 fragments between 1 and mononuclear complexes.

η6-Hexahelicene complexes of iridium and ruthenium: running along the helix.

The first η(6)-complexes of iridium and ruthenium coordinated to helicenes have been obtained. Hexahelicene (1), 2,15-dimethylhexahelicene (2), and 2,15-dibromohexahelicene (3) react with [Cp*IrCl(2)](2) and AgBF(4) in CD(3)NO(2) to afford quantitatively the complexes [Cp*Ir(η(6)-1)][BF(4)](2) (4A), [Cp*Ir(η(6)-2)][BF(4)](2) (5A), and [Cp*Ir(η(6)-3)][BF(4)](2) (6A), respectively. In all cases, the final thermodynamic products are similar, and they exhibit coordination between the 12 e(-) metal fragment [IrCp*](2+) and the terminal ring of the helicene. Monitoring the reaction by NMR shows formation of intermediates, some of which have been fully characterized in solution. These intermediates exhibit the metal fragment coordinated to the internal rings. We have also synthesized the bimetallic complex [(Cp*Ir)(2)(μ(2)-η(6):η(6)-2)][BF(4)](4) (7), achieving coordination between two units [IrCp*](2+) and the helicene 2. Following an analogous methodology, we have prepared the complex [(η(6)-cymene)Ru(η(6)-2)][BF(4)](2) (8), which has been studied by X-ray diffraction, confirming the preferential binding to the terminal aromatic ring.

Liquid crystals based on pseudohalogold(I) isocyanide complexes

Rod-like complexes [AuX(CNR)] (X = CN, SCN; R = C 6 H 4 OC n H 2n + 1 -p, C 6 H 4 C 6 H 4 OC n H 2n + 1 -p (n = 4, 6, 8, 10, 12); 2-F-4-OC 12 H 25 C 6 H 3 ; 3-F-4-OC 12 H 25 C 6 H 3 ; and 3,4,5-(OC 10 H 21 ) 3 C 6 H 2 ) have been prepared by reaction of [AuCl(CNR)] with KSCN or AgCN. The free phenyl isocyanides are not liquid crystals, but all the gold complexes display wide ranges of smectic A (S A ) mesophases, except the compound [Au(SCN)(CNC 6 H 4 OC 4 H 9 )] which is not liquid crystalline, and the trialkoxyphenyl derivatives which show columnar hexagonal phases at room temperature. The determining influence of the electronic and structural characteristics of both the pseudohalo and isocyanide ligands on the stabilization and type of mesophase is discussed.

Coordination versus coupling of dicyanamide in molybdenum and manganese pyrazole complexes.

The reactions of cis-[MoCl(η(3)-methallyl)(CO)(2)(NCMe)(2)] (methallyl = CH(2)C(CH(3))CH(2)) with Na(NCNCN) and pz*H (pzH, pyrazole, or dmpzH, 3,5-dimethylpyrazole) lead to cis-[Mo(η(3)-methallyl)(CO)(2)(pz*H)(μ-NCNCN-κ(2)N,N)](2) (pzH, 1a; dmpzH, 1b), where dicyanamide is coordinated as bridging ligand. Similar reactions with fac-[MnBr(CO)(3)(NCMe)(2)] lead to the pyrazolylamidino complexes fac-[Mn(pz*H)(CO)(3)(NH═C(pz*)NCN-κ(2)N,N)] (pzH, 2a; dmpzH, 2b), resulting from the coupling of pyrazol with one of the CN bonds of dicyanamide. The second CN bond of dicyanamide in 2a undergoes a second coupling with pyrazole after addition of 1 equiv of fac-[MnBr(CO)(3)(pzH)(2)], yielding the dinuclear doubly coupled complex [{fac-Mn(pzH)(CO)(3)}(2)(μ-NH═C(pz)NC(pz)=NH-κ(4)N,N,N,N)]Br (3). The crystal structure of 3 reveals the presence of two isomers, cis or trans, depending on whether the terminal pyrazoles are coordinated at the same or at different sides of the approximate plane defined by the bridging bis-amidine ligand. Only the cis isomer is detected in the crystal structure of the perchlorate salt of the same bimetallic cation (4), obtained by metathesis with AgClO(4). All the N-bound hydrogen atoms of the cations in 3 or 4 are involved in hydrogen bonds. Some of the C-N bonds of the pyrazolylamidino ligand have a character intermediate between single and double, and theoretical studies were carried out on 2a and 3 to confirm its electronic origin and discard packing effects. Calculations also show the essential role of bromide in the planarity of the tetradentate ligand in the bimetallic complex 3.

Macrocycle formation by proton-template-induced dimerization of complexes with (alkoxoimino)pyridine.

The existence of a strong hydrogen bond between two molecules of an (alkoxoimino)pyridinemanganese(I) complex induces their dimerization and the formation of a metallamacrocycle. The expected intramolecular attack of the alkoxo moiety is disfavored.