A Lead(II) Substituted Triplet Carbene.

Reaction of the pincer-type ligand L supported complex [LPbBr][BArF] () with Li[(C(═N)TMS)] furnishes [LPb(C(═N)TMS)][BArF] (). Diazo-compound eliminates dinitrogen upon irradiation affording formal plumba-alkyne , which persists in cold fluoroarene solutions. Variable temperature UV/Vis and NMR spectroscopies in combination with quantum-chemical calculations identify as a metal-substituted triplet carbene.

Synthesis and Modular Reactivity of Low Valent Al/Zn Heterobimetallics Supported by Common Monodentate Amides.

Recent advances on low valent main group metal chemistry have shown the excellent potential of heterobimetallic complexes derived from Al(I) to promote cooperative small molecule activation processes. A signature feature of these complexes is the use of bulky chelating ligands which act as spectators providing kinetic stabilization to their highly reactive Al-M bonds. Here we report the synthesis of novel Al/Zn bimetallics prepared by the selective formal insertion of AlCp* into the Zn-N bond of the utility zinc amides ZnR (R=HMDS, hexamethyldisilazide; or TMP, 2,2,6,6-tetramethylpiperidide).

Triphosphiranes as phosphinidene-transfer agents - synthesis of regular and chelating NHC phosphinidene adducts.

In this contribution we describe the general use of aryl-substituted triphosphiranes (ArP; Ar = Mes, Dip, Tip) as phosphinidene transfer reagents towards N-heterocyclic carbenes (NHCs) to give a library of twelve N-heterocyclic carbene phosphinidene adducts of the type ArPNHC (NHCPs), in which the NHCs have varying steric profiles, allowing a systematic evaluation of their structural and NMR-spectroscopic properties. In the next series of experiments we utilized 1,3- and 1,4-phenylene bridged bis-NHCs to access a new class of chelating bis(NHCP)s, of which three derivatives could be structurally characterized. The 1,4-phenylene derivatives were shown to be susceptible to P-C bond cleavage when irradiated with an LED (396 nm), providing a rare example of phosphinidene release from NHCPs.

Swift C-C bond insertion by a 12-electron palladium(0) surrogate.

The selective activation of C-C bonds holds vast promise for catalysis. So far, research has been primarily directed at rhodium and nickel under harsh reaction conditions. Herein, we report C-C insertion reactions of a 12-electron palladium(0) surrogate stabilized by a cyclic(alkyl)(amino) carbene (CAAC) ligand.

Beryllium-Mediated Halide and Aryl Transfer onto Silicon.

The reactivity of hexamethylcyclotrisiloxane (D ) towards BeCl , BeBr , BeI and [Be Ph ] was investigated. While BeCl only showed unselective reactivity, BeBr , BeI and [Be Ph ] cleanly react to the trinuclear complexes [Be Br (OSiMe Br) ], [Be I (OSiMe I) ] and [Be Ph (OSiMe Ph) ]. These unprecedented bromide, iodide and phenyl transfer reactions from a group II metal onto silicon offer a versatile access to previously unknown diorgano bromo and iodo silanolates.

Evidence for Carbene Intermediates in Isocyanide Homologation by Aluminium(I).

The C-C bond formation between C1 molecules plays an important role in chemistry as manifested by the Fischer-Tropsch (FT) process. Serving as models for the FT process, we report here the reactions between a neutral Al complex ( NacNac)Al (1, NacNac=HC[(CMe)(NDipp)] , Dipp=2,6-diisopropylphenyl) and various isocyanides. The step-by-step coupling mechanism was studied in detail by low-temperature NMR monitoring, isotopic labeling, as well as quantum chemical calculations.

On the Reactivity of Phosphaalumenes towards C-C Multiple Bonds.

Heterocycles containing group 13 and 15 elements such as borazines are an integral part of organic, biomedical and materials chemistry. Surprisingly, heterocycles containing P and Al are rare. We have now utilized phosphaalumenes in reactions with alkynes, alkenes and conjugated double bond systems.

Deoxygenation of chalcogen oxides EO (E = S, Se) with phospha-Wittig reagents.

In here we present the deoxygenation of the chalcogen oxides EO (E = S, Se) with R-P(PMe), so-called phospha-Wittig reagents. The reaction of DABSO (DABCO·2SO) with R-P(PMe) (R = Mes*, 2,4,6-Bu-CH; Ter, 2,6-(2,4,6-Me-CH)-CH) resulted in the formation of thiadiphosphiranes (RP)S (1:R), while selenadiphosphiranes (RP)Se (2:R) were afforded with SeO, both accompanied by the formation of OPMe. Utilizing the sterically more encumbered Ter-P(PMe) (Ter = 2,6-(2,6-iPr-CH)-CH) a different selectivity was observed and (TerP)Se (2:DipTer) along with [Se(μ-PTer)] (3:DipTer) were isolated as the Se-containing species in the reaction with SeO.

A diarsene radical anion.

The isolation of the first diarsene radical anion by reduction of a neutral diarsene is presented. Comprehensive characterisation in conjunction with DFT calculations reveals unpaired spin density residing in the antibonding π*-orbital with involvement of the terphenyl ligands. First reactivity studies reveal no pronounced radical, but rather reducing properties.

Modulating the reactivity of phosphanylidenephosphoranes towards water with Lewis acids.

Phosphanylidenephosphoranes of the type R-P(PR'), also known as phospha-Wittig reagents, can be utilized in a variety of bond activation reactions exploiting their phosphinidenoid reactivity. Herein, we thoroughly show that a facile PMe for HO exchange gives access to various primary phosphine oxides of the general formula RP(H)O (R = Mes*, Ter, Ter) and the molecular structure of TerP(O)H was determined. However, phosphanylidenephosphoranes are described to be highly nucleophilic as well.

Metal-Free N-H Bond Activation by Phospha-Wittig Reagents.

N-containing molecules are mostly derived from ammonia (NH ). Ammonia activation has been demonstrated for single transition metal centers as well as for low-valent main group species. Phosphinidenes, mono-valent phosphorus species, can be stabilized by phosphines, giving so-called phosphanylidenephosphoranes of the type RP(PR' ).

Construction of Inorganic Crown Ethers by s-Block-Metal-Templated Si-O Bond Activation.

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of D (I) ( D ,=(Me Si O) ) was achieved by the reaction with GaI and MI (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I /[GaI ] ) are required as nucleophiles.

A Second Modification of Beryllium Bromide: β-BeBr.

The synthesis of a second beryllium bromide modification, β-BeBr, was accomplished through recrystallization of α-BeBr from benzene in the presence of -decamethylpentasiloxane. This phase was analyzed via single-crystal X-ray diffraction and IR and Raman spectroscopy as well as density functional theory calculations. This enabled a comparison to α-BeBr and the α and β phases of beryllium chloride and iodide.

Coordination polymers of alkali metal cyclosiloxazanides with one- and two-dimensional structures.

The reaction of O(SiMeCl) with ammonia yielded the cyclic siloxazane O(SiMe)NH (1), which was used as a precursor for the synthesis of siloxazanide-type alkali metal salts. The metalation of 1 with the strong bases BzA (A = Na, K, Rb, Cs and Bz = benzyl) results in different dimensional structures depending on the alkali metal ion used. These results give new insights into framework design with inorganic building blocks and the coordination ability of siloxanes.

Not Non-Coordinating at All: Coordination Compounds of the Cyclodimethylsiloxanes D (D = MeSiO; = 6, 7) and Group 2 Metal Cations.

We present the coordination chemistry of the cyclodimethylsiloxanes D and D toward alkaline earth metal salts. The coordination chemistry of these macrocycles toward alkaline earth metals has been unprecedented to date, and we could show that these ligands coordinate better than previously thought. Direct reaction of alkaline earth metal salts with these ligands yields stable complexes even with a relatively strongly coordinating iodide anion.

Alkaline Earth Metal Template (Cross-)Coupling Reactions with Hybrid Disila-Crown Ether Analogues.

Alkaline earth metal iodides were used as templates for the synthesis of novel silicon-based ligands. Siloxane moieties were (cross-)coupled and ion-specific, silicon-rich crown ether analogues were obtained. The reaction of 1,2,7,8-tetrasila[12]crown-4 (I) and 1,2-disila[9]crown-3 (II) with MgI yielded exclusively [Mg(1,2,7,8-tetrasila[12]crown-4)I ] (1).

Synthesis and crystal structures of novel tertiary butyl substituted (pseudo-)halogen bismuthanes.

Herein we present the synthesis and characterization of di-tertiary butyl substituted (pseudo-)halogen bismuthanes tBu2BiX (X = Cl (1), Br (2), I (3), CN (4), N3 (5), SCN (6)). These compounds were obtained via different reaction paths. Compound 1 was obtained by a Grignard reaction of BiCl3 with two equivalents of tBuMgCl, whereas compounds 2, 3, 4 and 6 were synthesised by a oxidative addition/reductive elimination pathway starting from tBu3Bi and X2 (X = Br, I, CN, SCN).

Insights into the Coordination Ability of Siloxanes Employing Partially Silicon Based Crown Ethers: A Comparative Analysis of s-Block Metal Complexes.

Herein we present the synthesis and coordination chemistry of the partially silicon based crown ether analogues 1,2,4,5-tetrasila-benzo[15]crown-5 (1) and 1,2,4,5-tetrasila[18]crown-6 (7). Stable complexes of alkali and alkaline earth metal iodides could be obtained showing the good coordination ability of these ligands. The complexes [M (1,2,4,5-tetrasila-benzo[15]crown-5)I] (M = Li (2), Na (4)) and [M (1,2,4,5-tetrasila-benzo[15]crown-5)I] (M = Mg (3), Ca (5), Sr (6)) were obtained by equimolar reaction of 1 with the respective alkali or alkaline earth metal iodide.

The coordination behaviour and reactivity of partially silicon based crown ethers towards beryllium chloride.

Through reactions of 1,2-disila[12]crown-4 or 1,2-disila-benzo[12]crown-4 ethers with BeCl2 eight-membered Be-O-heterocycles, which are annulated by two six-membered Be-O-cycles were obtained and characterised. The reactions leading to these unusual ring systems have been investigated by NMR and IR spectroscopy as well as reactions with further ligand derivatives.

Alkali and Alkaline Earth Metal Derivatives of Disila-Bridged Podands: Coordination Chemistry and Structural Diversity.

Within this study, the synthesis and coordination chemistry of open-chain ligands bearing disila-units is presented. Instead of basic 1:1 complexes, structural diversity was discovered in the variety of ligand and salt. Stable complexes of alkali and alkaline earth metal complexes were obtained by equimolar reactions of different salts with the disila-bridged podands 8,9-disila-EO5 (1) and 11,12-disila-EO7 (2) (EO5 = pentaethylene glycol; EO7 = heptaethylene glycol).

A structural study of alkaline earth metal complexes with hybrid disila-crown ethers.

Compounds consisting of [M(1,2-disila-[3n]crown-n)] (M = Mg, Ca, Sr, Ba; n = 5, 6) and [Ba(1,2-disila-benzo[18]crown-6)] cations and different anions were obtained by equimolar reaction of the hybrid disila-crown ethers 1,2-disila[15]crown-5 (1), 1,2-disila[18]crown-6 (2) and 1,2-disila-benzo[18]crown-6 (7) with alkaline earth metal salts. Even with strongly coordinating anions such as Br or I stable complexes could be obtained, showing the good coordination ability of these ligands. The structures of all coordination compounds were determined via single crystal X-ray diffraction (XRD).