Substituted bisphosphanylamines as ligands in gold(I) chemistry – 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 alkaline‐earth 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 “hard-soft” mismatch between the “hard” metal center and the “soft” 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 1H 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-cyclononatetraenyl lanthanide complexes

The synthesis of the first half-sandwich complexes based on the cyclononatetraenyl (Cnt = C$_9$H$_9^−$) ligand ([Ln$^{III}$(η$^9$-Cnt)(η$^3$-BH$_4$)$_2$(thf)] (Ln = La, Ce)) is reported. The title compounds were obtained from the reaction of [Ln(BH$_4$)$_3$(thf)$_3$] and [K(Cnt)]. Further solvation of [LnIII(η$^9$-Cnt)(η$^3$-BH$_4$)$_2$(thf)] with tetrahydrofuran (THF) resulted in a reversible decoordination of the Cnt ring and the formation of the ionic species [Ln$^{III}$(η$^3$-BH$_4$)$_2$(thf)$_5$][Cnt]. Removal of THF from [La$^{III}$(η$^9$-Cnt)(η$^3$-BH$_4$)$_2$(thf)] gave the polymeric compound [La$^{III}$(μ-η$^2$:η$^2$-BH$_4$)$_2$(η$^3$-BH$_4$)(η$^9$-Cnt)]$_n$

Coinage Metal Bis(amidinate) Complexes as Building Blocks for Self‐Assembled One‐Dimensional Coordination Polymers

The pyridyl functionalized amidinate [{PyC≡CC(NDipp)$_{2}$}Li(thf)$_{2}$]n was used to synthesize a series of bis-amidinate complexes [{PyC≡CC(NDipp)$_{2}$}$_{2}$M$_{2}$] (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)$_{2}$ (hfac=hexaflouroacetylacetonate) for self-assembly. Interestingly, the three coordination polymers [{PyC≡CC(NDipp)$_{2}$}$_{2}$M$_{2}$][Zn(hfac)$_{2}$] (M=Cu, Ag, Au), exhibit a zig zag shape in the solid state. To achieve linear coordination geometry other connectors such as M’(acac) (M’=Ni, Co) (acac=acetylacetonate) were investigated. The thus obtained compounds [{PyC≡CC(NDipp)$_{2}$}$_{2}$Cu$_{2}$][M’(acac)$_{2}$] (M’=Ni, Co) are indeed linear heterobimetallic coordination polymers featuring a metalloligand backbone with fully supported metallophilic interactions

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 gold–gold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various para substituted (R) N,N′-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 [pRXylForm$_2$Au$_2$] (R = –OMe, –Me, –Ph, –H, –SMe, and –CO$_2$Me). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter σ$_p$ revealed the trends in the $^1$H and $^{13}$C NMR spectra. These results showed the influence of the donor–acceptor 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

Stereoselective Activation of Small Molecules by a Stable Chiral Silene

The reaction of the dilithium salt of the enantiopure (S)-BINOL (1,1’-bi-2-naphthol) with two equivalents of the amidinate-stabilized chlorosilylene [L$^{Ph}$SiCl] (L$^{Ph}$=PhC(NtBu)$_2$) 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$_2$ and HCl. The reaction with S$_8$ 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$_2$ 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$_2$ and HCl to a Si=C bond is unprecedented

Rhenium is different: CO tetramerization induced by a divalent lanthanide complex in rhenium carbonyls

The reduction of M$_{2}$(CO)$_{10}$ (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 Mono‐ and Bis‐Silylene

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, [LSi−Si(NDipp)L] (L=PhC(N$^t$Bu)$_2$), 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 Cu$^I$X (X=mesityl, Cl, Br, I), electron redistribution occurs resulting in the formation of [{LSi(NDipp)Si(L)}−CuX], in which both silicon atoms are in the +II formal oxidation state. Removal of the copper center from [{LSi(NDipp)Si(L)}−CuX] by using a Lewis basic carbene led to reformation of the precursor [LSi−Si(NDipp)L]. Thus, the process is fully reversible. This showcases the first example of Lewis acid/base-induced reversible electromerism in silicon chemistry