57 research outputs found
Substituted bisphosphanylamines as ligands in gold(I) chemistry â synthesis and structures
Dimethyl 5-aminoisophthalate, which is a building block of amino-substituted tetralactam macrocycles, was used as ligand in gold(I) chemistry to form model complexes for macrocyclic gold compounds. Reaction of dimethyl 5-aminoisophthalate with chlorodiphenylphosphine gave the diphosphine compound dimethyl 5-[N,N-bis(diphenylphosphanyl)amino]isophthalate (dmbpaip). This compound can further be reacted with [AuCl(tht)] (tht = tetrahydrothiophene) to give the dinuclear complex [Au(2),Cl(2)(dmbpaip)]. In contrast, treatment of dinbpaip with [Au(tht)(2)]ClO(4) resulted in the ionic compound [Au(2)(dmbpaip)(2)](ClO(4))(2) in which the cation forms an eight-membered Au(2)P(4)N(2) heterocycle. In both gold(I) compounds Au center dot center dot center dot Au interactions are observed. All new compounds were characterized by single-crystal X-ray diffraction
Stable bidentate silylene adducts of alkalineâearth amides
The coordination chemistry of silylenes is known for a vast number of elements of all blocks of the periodic table. However, only a handful of examples of silylene complexes have been reported for heavy alkaline-earth elements, which is mainly attributed to the âhard-softâ mismatch between the âhardâ metal center and the âsoftâ silicon donor. Herein, we report the synthesis and characterization of a series of alkaline-earth silylene complexes comprising a bidentate pyridyl-amido-silylene ligand. The isolated Ca, Sr and Ba complexes show considerably increased stability in comparison to other known alkaline-earth silylene complexes. The molecular structures of all three complexes are essentially similar. Interestingly, depending on the central metal, the 1Hâ
NMR chemical shifts of the ortho-H atom show unexpected large differences. DFT computations were conducted to elucidate this trend in the NMR resonances
Mono- and bimetallic amidinate samarium complexes â synthesis, structure, and hydroamination catalysis
Coinage Metal Bis(amidinate) Complexes as Building Blocks for SelfâAssembled OneâDimensional Coordination Polymers
The pyridyl functionalized amidinate [{PyCâĄCC(NDipp)}Li(thf)]n was used to synthesize a series of bis-amidinate complexes [{PyCâĄCC(NDipp)}M] (M=Cu, Ag, Au) with fully supported metallophilic interactions. These metalloligands were then used as building blocks for the synthesis of one-dimensional heterobimetallic coordination polymers using Zn(hfac) (hfac=hexaflouroacetylacetonate) for self-assembly. Interestingly, the three coordination polymers [{PyCâĄCC(NDipp)}M][Zn(hfac)] (M=Cu, Ag, Au), exhibit a zig zag shape in the solid state. To achieve linear coordination geometry other connectors such as Mâ(acac) (Mâ=Ni, Co) (acac=acetylacetonate) were investigated. The thus obtained compounds [{PyCâĄCC(NDipp)}Cu][Mâ(acac)] (Mâ=Ni, Co) are indeed linear heterobimetallic coordination polymers featuring a metalloligand backbone with fully supported metallophilic interactions
Stereoselective Activation of Small Molecules by a Stable Chiral Silene
The reaction of the dilithium salt of the enantiopure (S)-BINOL (1,1â-bi-2-naphthol) with two equivalents of the amidinate-stabilized chlorosilylene [LSiCl] (L=PhC(NtBu)) led to the formation of the first example of a chiral cyclic silene species comprising an (S)-BINOL ligand. The reactivity of the Si=C bond was investigated by reaction with elemental sulfur, CO and HCl. The reaction with S led to a Si=C bond cleavage and concomitantly to a ring-opened product with imine and silanethione functional groups. The reaction with CO2 resulted in the cleavage of the CO molecule into a carbonyl group and an isolated O atom, while a new stereocenter is formed in a highly selective manner. According to DFT calculations, the [2+2] cycloaddition product is the key intermediate. Further reactivity studies of the chiral cyclic silene with HCl resulted in a stereoselective addition to the Si=C bond, while the fully selective formation of two stereocenters was achieved. The quantitative stereoselective addition of CO and HCl to a Si=C bond is unprecedented
Systematic investigation of the influence of electronic substituents on dinuclear gold( i ) amidinates: synthesis, characterisation and photoluminescence studies
Dinuclear gold(I) compounds are of great interest due to their aurophilic interactions that influence their photophysical properties. Herein, we showcase that goldâgold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various para substituted (R) N,NâČ-bis(2,6-dimethylphenyl)formamidinate ligands (pRXylForm; Xyl = 2,6-dimethylphenyl and Form = formamidinate) were treated with Au(tht)Cl (tht = tetrahydrothiophene) to give via salt metathesis the corresponding gold(I) compounds [pRXylFormAu] (R = âOMe, âMe, âPh, âH, âSMe, and âCOMe). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter Ï revealed the trends in the H and C NMR spectra. These results showed the influence of the donorâacceptor abilities of different substituents on the ligand system which were confirmed with calculated orbital energies. Photophysical investigations showed their lifetimes in the millisecond range indicating phosphorescence processes and revealed a redshift with the decreasing donor ability of the substituents in the solid state
Rhenium is different: CO tetramerization induced by a divalent lanthanide complex in rhenium carbonyls
The reduction of M(CO) (M = Mn, Re) with different divalent lanthanide (Ln = Sm, Yb) compounds was investigated. Depending on the steric demand of the ligand, either unusual CO tetramerization or formation of a new Re carbonyl anion occurred in the case of Re. Theoretical calculations were performed for a better understanding of the nature of bonding in the newly formed species
Stimuli Responsive Silylene: Electromerism Induced Reversible Switching Between Monoâ and BisâSilylene
Electromerism is a very well-known phenomenon in transition metal chemistry. In main group chemistry, this concept has only started getting attention recently. We report stimuli responsive low-valent silicon compounds exhibiting electromerism. A mixed-valent silaiminyl-silylene 1, [LSiâSi(NDipp)L] (L=PhC(NBu)), was synthesized in a single step from amidinate-chlorosilylene. Compound 1 has two interconnected Si atoms in formally +I and +III oxidation states. Upon treatment with Lewis acidic CuX (X=mesityl, Cl, Br, I), electron redistribution occurs resulting in the formation of [{LSi(NDipp)Si(L)}âCuX], in which both silicon atoms are in the +II formal oxidation state. Removal of the copper center from [{LSi(NDipp)Si(L)}âCuX] by using a Lewis basic carbene led to reformation of the precursor [LSiâSi(NDipp)L]. Thus, the process is fully reversible. This showcases the first example of Lewis acid/base-induced reversible electromerism in silicon chemistry
Hetero-bimetallic Lanthanide-Coinage Metal Compounds Featuring Possible Metal-Metal Interactions in the Excited State
Heterometallic complexes, combining metals of the outer rims of the d-block, for example lanthanides(III) (Ln) and coinage metals(I) (M) are scarcely reported, synthetically challenging and highly interesting in terms of their interactions. In this context, we synthesized hetero-bimetallic LnâM compounds ligated by the phosphine functionalized amidinate system (N,Nâ-bis[(2-diphenylphosphino)phenyl]formamidinate, âdpfamâ). The resulting compounds [dpfam3LnM][OTf] (Ln = La, Nd and M = Ag, Au) feature a close proximity of the two metal centres and were investigated experimentally by photoluminescence spectroscopy and quantum chemical calculations. The latter showed rare LaâAu interactions for the first excited state
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