Transition-metal silyl complexes

TMC Literature Highlight-25 Transition Met. Chem.15, 000-000 (1990)     

Heteroleptic zinc dipyrromethene complexes

¹H NMR spectroscopy has been used to study the complexation of a per‐alkyl dipyrromethene with zinc acetate. An intermediate, assigned to be the heteroleptic Zn(dipyrromethene)(acetate) complex, is observed under titration conditions although only zinc(dipyrromethene)₂ is obtained after simple work‐up. This indicates that disproportionation occurs during work‐up and that dipyrromethene complexation does not occur under self‐assembled control.     

Theoretical study of hydrogen-bonded formaldehyde complexes

The hydrogen-bonded complexes involving formaldehyde and a series of proton donors of varying strengths, have been investigated at different levels of ab initio MO theory. The structures of the studied complexes were SCF optimized at the 6-31G basis set level. The binding energy was estimated employing basis set superposition correction, zero-point vibrations and MP2 correlation contribution at the different basis set: STO-3G; 6-31G; MP2/6-31G; 6-31G**; MP2/6-31G**; 6-311G(2d, 2p) and MP2/6-311G(2d, 2p). Linear relationships were found of the calculated binding energy with: the calculated shift in the carbonyl stretching frequency, the changes in carbonyl bond length and the optimum value of hydrogen-bond distance; furthermore the calculations confirm a parallel trend between the proton-donor ability and the strength of the hydrogen bond.     

Lanthanide complexes of alkylsulfamoyl-substituted phthalocyanines

The extra-ligand complexes obtained in the reaction of tetra-4-[6′,8′-di(N,N-diethylsulfamoyl)-2′-naphtyloxy]phthalocyanine with erbium or ytterbium acetylacetonates were characterized by elemental analysis, IR and electronic spectroscopy.     

Polarography of lead itaconate complexes

The complexation of lead ions with itaconic acid (H(2) A) has been studied polarographically at 30 degrees . At pH < pK(1), the complex species Pb(HA)(+) was identified. At pK(1) < pH < pK(2) and pH > pK(2) the formation of Pb(A) and Pb(A)(2)(2-) respectively, was confirmed. The dissociation constant of Pb(A)(2)(2-) was found to be 8.3 x 10(-5). The electrode reactions were established.     

Thermal decomposition of complexes

The iron(II) complex of the Schiff bases trans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn), manganese(II) and vanadyl complexes of the Schiff bases cis- andtrans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn) were prepared and characterized by IR spectroscopy, and elemental analysis. These new complexes were submitted to thermal analysis (TG and DSC) under dynamic air atmosphere. The differences in the decomposition profiles were related to the structure of isomers and decomposition intermediates were characterized according to their X-ray diffraction pattern and by their infrared spectrum. This revised version was published online in August 2006 with corrections to the Cover Date.     

Metal complexes of 1-methyltetrabenzooctadehydrocorrin

In reaction of 2,3-dihydro-3-[(1-hydroxy-1-methyl-1H-isoindol-3-yl)methylene]-1H-isoindol-1-one with hydrazine hydrate in the presence of a template agent (metal acetates) in butanol environment metal complexes formed of 1-methyltetrabenzooctadehydrocorrin. A scheme of formation of these compounds was suggested and their spectral characteristics were investigated.     

Linear homobimetallic palladium complexes

The oxidative addition of C₆H₄-1,4-I₂ (1) to Pd(PPh₃)₄ (2) gives mononuclear trans-(Ph₃P)₂Pd(C₆H₄-4-I)(I) (3), which can be converted to trans-(Ph₃P)₂Pd(C₆H₄-4-I)(OTf) (5) by its reaction with [AgOTf] (4). Complex 5 can be used in the high-yield preparation of a series of unique cationic mono- and dinuclear palladium complexes of structural type [trans-(Ph₃P)₂Pd(C₆H₄-4-I)(L)]⁺ (7, L = C₄H₄N₂; 9a, L = C₅H₄N-4-CN; 9b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-I)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-I)]²⁺ (14a, N^∩N = C₆H₄-1,4-(CN)₂; 14b, N^∩N = (C₆H₄-4-CN)₂; 14c, N^∩N = 4,4′-bipyridine (=bipy)). Complexes 7, 9 and 14 rearrange in solution to give [trans-(Ph₃P)₂Pd(C₆H₄-4-PPh₃)(L)]²⁺ (10, L = C₄H₄N₂; 12a, L = C₅H₄N-4-CN; 12b, L = NC-4-C₅H₄N) and [trans-(C₆H₄-4-PPh₃)(Ph₃P)₂Pd ← N^∩N → Pd(PPh₃)₂(C₆H₄-4-PPh₃)]⁴⁺ (15a, N^∩N = C₆H₄-1,4-(CN)₂; 15b, N^∩N = (C₆H₄-4-CN)₂) along with {[(Ph₃P)₂(Ph₃P-4-C₆H₄)Pd(μ-I)]₂}²⁺ (11).The solid state structures of 3, 9a, 10, 11 and 15b are reported. Most characteristic for all complexes is the square-planar coordination geometry of palladium with trans-positioned PPh₃ ligands. In 3 the iodide and the 4-iodo-benzene are linear oriented laying with the palladium atom on a crystallographic C₂ axes. In 9a this symmetry is broken by steric interactions of the PPh₃ ligands with the 4-cyanopyridine and 4-iodobenzene groups. Compound 11 contains two μ-bridging iodides with different Pd-I separations showing that the ligand induces a stronger trans-influence than PPh₃. In 15b, the Ph₃PC₆H₄Pd ← NCC₆H₄C₆H₄CN → PdC₆H₄PPh₃ building block is rigid-rod structured with the C₆H₄ units perpendicular oriented to the Pd coordination plane, while the biphenylene connecting moiety is in-plane bound.     

η2-Phosphasilene transition metal complexes – a novel building block for hetero-multimetallic complexes

Compound η²-((R₃Si)₂Si=PH)–Pt(dmpe) was synthesized by trapping the transient phosphasilene, (R₃Si)₂Si=PH. Novel hetero-bi- and tri-metallic complexes derived from η²-((R₃Si)₂Si=PH)–Pt(dmpe) containing Pt with Li, Zn, Hg and Ag metals were synthesized and characterized by multi- nuclear NMR spectroscopy and X-ray crystallography. The synthesis of η²-((R₃Si)₂Si=PH)–Pt(dmpe), and its bonding character are discussed; a 1,2-silyl shift from silicon to phosphorus (a ‘Brook-type’ rearrangement) within the coordination sphere of a Pt complex is also reported.     

Non-oral drug preparations containing cyclodextrin complexes

The application of cyclodextrin complexed drugs in non-oral dosage forms results in the following advantages:

- The stability of volatile, chemically unstable drugs is significantly improved by transforming them into cyclodextrin complexes.

- The transformation of oils, liquids into crystalline, solid state provides better physical, mechanical properties, easy to handle products.

- Complex formation/encapsulation on molecular scale/remarkably enhances the dissolution and absorption of lipophylic drugs.

- The formation of water soluble inclusion complexes makes possible the preparation of parenteral dosage forms without using organic solvents or detergents.

     

Ethynylgold(I) complexes

Reactions between R₃PAuCl, NaOEt, and HCCR′ under mild conditions produce R₃PAuCCR′ in excellent yield. When R′ = H, a second step leading to the formation of R₃PAuCCAuPR₃ can take place. Exchange reactions of ethynyl for chloride between the ethynylgold complexes and HgCl₂, cis-[PtCl₂L₂cis-[PtCl₂(CO)L], and R₂″PAuCl have been monitored, revealing R₃PAuCCR′ to be useful alkynylating agents. In the reaction with cis-[PtCl₂(CO)L], the first substitution step is non-specific.     

Manganese cationic pyrazolylamidino complexes

The reactions of fac-[MnBr(CO)₃(NHC(CH₃)pz^∗-κ²N,N)] (pz^∗ = pz, dmpz; pzH = pyrazole; dmpzH = 3,5-dimethylpyrazole) with wet AgBF₄ in a 1:1 ratio lead to the cationic pyrazolylamidino complexes fac-[Mn(OH₂)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄. The aquo ligand is readily substituted by 2,6-xylylisocyanide (CNXyl) to give fac-[Mn(CNXyl)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄. The pyrazole complexes fac-[Mn(pz^∗H)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄ are obtained by treating fac-[MnBr(CO)₃(NCMe)₂] with AgBF₄ and then with pyrazole (pzH or dmpzH), in a 1:1:2 ratio. A similar reaction using 1:1:1 ratio and AgClO₄ leads to the acetonitrile complexes fac-[Mn(NCMe)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]ClO₄. The X-ray structures of the complexes show moderate hydrogen bonds interactions between the N-bond hydrogen of the pyrazolylamidino ligand and the anion. In the aquo complex, one of the hydrogens of the coordinated water molecule is also involved in a hydrogen bond.     

Ruthenium complexes containing aromatic thioamides

Summary Reaction of aromatic thioamides, LH, withcis-[Ru(CO)₂Cl₂] yieldscis-[Ru(CO₂)Cl₂LH]. The complexes have been characterised by analytical, i.r., electronic and n.m.r. spectral and magnetic measurements. All the Ru^II diamagnetic complexes have been assigned distorted octahedral geometry.     

Tetraoxotetraamide macrocyclic complexes

A new class of 16- and 17-membered tetraamide macrocyclic complexes, [ML¹X₂] and [ML²X₂] [M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; X = NO₃ or Cl], have been prepared by the template reaction of anthranilic acid, 1,2-diaminoethane or 1,3-diaminopropane and succinic acid in 2:1:1 molar ratio. The stoichiometries and coordination modes of the complexes have been deduced from physicochemical and spectroscopic measurements. This revised version was published online in June 2006 with corrections to the Cover Date.     

Xylyl isocyanide platinum and palladium complexes

Bis(cycloocta-1,5-diene)platinum reacts with isopropyl isocyanide to give the trinuclear complex [Pt₃(CNPrⁱ)₆]. A related palladium compound was prepared by treating either [Pd(dba)₂] or [Pd₂(dba)₂CHCl₃] with 2,6-dimethylphenyl isocyanide. Reactions of the cluster [Pt₃(CNC₆H₃-2,6-Me₂)₆] and its presumed palladium analogue with the olefins (NC)₂C:C(CN)₂, F₂C:CFCl and (CN)₂C:C(CF₃)₂, give the compounds [M(olefin)(CNC₆H₃-2,6-Me₂)₂] (M  Pt, Pd) in which the metals are η²-bonded to the coordinated olefins. The compound [Pd₃(CNC₆H₃-2,6-Me₂)₆] reacts with F₂C:CFBr and with F₂C:CFCl to give the trans complexes [Pd(X)(C₂F₃)(CNC₆H₃-2,6-Me₂)₂] (X  Br, Cl). Similar compounds [M(L)-(CNC₆H₃-2,6-Me₂)₂] (M  Pt, Pd), (L  MeO₂CHC:CHCO₂Me, OOCH: CHCOO) have also been prepared, and characterised. Two platinum complexes [Pt(CH:NC₆H₃-2,6-Me₂)(SiMePh₂)(CNC₆H₃-2,6-Me₂)₂] and [Pt₂(μ-(PhC)₂CO)(CNC₆H₃-2,6-Me₂) ₄] hav been synthesized by treating the complex [Pt₃(CNC₆H₃-2,6-Me₂)₆] with HSiMePh₂ and cyclopropenone, respectively. NMR and IR data for the new species are reported and discussed.     

The preparation of α-methoxyalkyliron complexes: precursors of secondary carbeneiron complexes

The addition of methyl-, n-butyl-, phenyl-, and p-tolyl-lithium reagents to (C₅H₅)(CO)₂FeCHOCH₃⁺ PF₆⁺ gives the respective α-methoxyalkyliron complexes in good yield. The addition of vinyllithium or vinylmagnesium bromide to (C₅H₅)(CO)₂FeCHOCH₃⁺ PF₆^? yields rearranged product cis-(C₅H₅)(CO)₂- FeCH₂CHCHOCH₃.     

Palladium and platinum guanine complexes

Summary Reaction of [MCl₂(H₄Y)] or (H₆Y)[MCl₄] compounds (M = Pd or Pt; Y = EDTA, PDTA or CDTA) with guanine (Gu-H) in 0.5 M HCl yields new complexes MCl₂(Gu-H)(H₂O which have been characterized by elemental analyses in conjunction with electronic, i.r. and n.m.r. spectra. A dimeric structure with two bridging chloride ligands, including coordination of guanine through atom N(9), is proposed for both compounds.Abbreviations used in the paper EDTA 1,2-diaminoethane-N,N,N,N-tetraacetate - PDTA 1,2-diaminopropane-N,N,N,N-tetraacetate - CDTA trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetate - Gu-H guanine - 9-EtGu-H 9-ethylguanine     

Crystallographic and structural characterization of heterometallic platinum complexes Part VI. Heterohexanuclear complexes

This review classifies and analyzes heterohexanuclear platinum clusters into seven types of metal combinations:Pt₅M, Pt₄M₂, Pt₃M₃, Pt₂M₄, PtM₅, Pt₂M₃M′, and Pt₂M₂M₂′. The crystals of these clusters generally belong to six crystal classes: monoclinic, triclinic, orthorhombic, tetragonal, trigonal and cubic. Among the wide range of stereochemistry adopted by these clusters, octahedral and capped square-pyramidal are the most common. Although platinum is classified as a soft metal atom, it bonds to a variety of soft, borderline and hard metals. Nineteen different heterometal ions are involved in hexanuclear platinum clusters. The shortest Pt-M bond distance in the case of M being a non-transition element is 2.395(4) Å for germanium and for M being a transition metal ion it is 2.402(2) Å for Cobalt. The shortest Pt-Pt bond distance observed in these clusters is 2.532 Å. Several relationships between the structural parameters are identified and discussed. Some clusters exist in two isomeric forms and some show crystallographically independent molecules within the same crystal. Such isomers and independent molecules are examples of distortion isomerism.      

Thermal decomposition of metal complexes. X. uranyl nitrate—phenylurea complexes

The kinetics and mechanism of the thermal association process (solid—solid interaction) and the reverse dissociative process

(where n-2–5;=m1–4; n+ m= 3–6) is discussed. The “ activation energy” and the reaction order have been evaluated. It was found that the associative reaction is chemically controlled whereas the dissociative process is physical in nature; therefore no mutual agreement was found between theE^*_a values relative to the two associative and dissociative processes.     

Syntheses of thiopyrylium-tungsten complexes

Hexacarbonyltungsten reacts with 2,4,6-triphenylthiopyrylium perchlorate and 2,6-dianisyl-4-phenylthiopyrylium perchlorate in diglyme to afford cationic thiopyrylium salts, 2,4,6-[H₂(C₆H₅)₃C₅SW(CO)₃]⁺ClO₄ ⁻ and 2,6,4-[H₂(C₆H₅)(C₆H₄OCH₃)₂C₅SW(CO)₃]⁺ClO₄ ⁻. Both compounds were characterized by physico-chemical and spectroscopic methods. The HMQC, DEPT-45, and COSY experiments were used to assign carbon and proton signals in the ¹H and ¹³C NMR spectra.