ABSTRACT
The cyclic tetraimidazolium salt (H4-)(PF6)4 with flexible linkers between the imidazolium groups has been synthesized following a stepwise synthetic approach. In situ deprotonation of (H4-)(PF6)4 in the presence of different metal ions leads to complexes where the tetracarbene ligand shows differing coordination modes depending on the metal center. Due to its high flexibility the tetracarbene ligand folds around d(8) transition metal ions such as Ni(II), Pd(II) and Pt(II) to yield mononuclear tetracarbene complexes of type [M()](PF6)2 featuring a square-planar coordinated metal center. Reaction of with metal centers that prefer a linear coordination mode such as Ag(I) yields the tetranuclear silver(i) octacarbene complex [Ag4()2](PF6)4 featuring four silver(i) ions sandwiched in between two tetra-NHC ligands.
ABSTRACT
Purine nucleobases are excellent ligands for metal ions, forming normally coordinative Werner-type bonds by utilizing the N donor atoms of the nucleobase skeleton. Here we show that purines such as 8-chlorocaffeine and 8-bromo-9-methyladenine react with [Pt(PPh3)4] under oxidative addition of the C(8)-halogen bond to the metal center. The resulting Pt(II) complexes feature a C(8)-bound ylidene ligand. Protonation of the ylidene at the N(7/9)-atom yields complexes bearing a protic N-heterocyclic carbene ligand derived from the purine base with an NMe,NH-substitution pattern.
Subject(s)
Metals/chemistry , Purines/chemical synthesis , Heterocyclic Compounds/chemistry , Magnetic Resonance Spectroscopy , Models, Molecular , Platinum Compounds/chemical synthesis , Platinum Compounds/chemistry , Purine Nucleosides/chemistry , Purine Nucleotides/chemistry , Purines/chemistry , X-Ray DiffractionABSTRACT
Reaction of the benzene-1,3,5-trisimidazolium salt H3-1(Br)3 with [Rh(Cp*)(Cl)2]2 results in the formation of the dinuclear, doubly orthometalated complex [2]Br, which yields, depending on the metal source provided, either a triply orthometalated heterotrimetallic Rh2/Ir complex [3] or trinuclear heterotrimetallic Rh2/Au complexes of types [4a] or [4b].
ABSTRACT
The synthesis of the macrocyclic tetraimidazolium salt (H4-1)(Br)4 and the anion exchange to (H4-1)(PF6)4 have been explored. Deprotonation of (H4-1)(PF6)4 with Ag2O yields the mono- and dinuclear silver(I) complexes [Ag(H2-1)](PF6)3 and [Ag2(1)](PF6)2. Transmetallation of the dicarbene and tetracarbene ligands to gold(I) yields the mono- and dinuclear gold(I) complexes [Au(H2-1)](PF6)3 and [Au2(1)](PF6)2. The monosilver complex [Ag(H2-1)](PF6)3, featuring two imidazolium moieties, has been deprotonated and used for the synthesis of the tetranuclear silver(I) octacarbene complex [{Ag(1)}2Ag2](PF6)4.
ABSTRACT
The reaction of the benzene derived trisimidazolium salt [1](PF(6))(3) with [PdCl(allyl)](2) gave complex [2](PF(6))(3) featuring three Pd(allyl) moieties sandwiched between two tricarbene ligands, whereas the reaction of [1](PF(6))(3) with [M(Cp*)(Cl)(2)](2) (M = Ir, Rh) resulted in the formation of dinuclear M(III) complexes [3]PF(6) (M = Ir) and [4]PF(6) (M = Rh) where each metal center is coordinated by an NHC donor and orthometallates the central phenyl ring. The remaining imidazolium group in [4]PF(6) can be metallated with [Rh(Cp*)(Cl)(2)](2) to give the trinuclear triply orthometallated complex [5].
Subject(s)
Coordination Complexes/chemistry , Methane/analogs & derivatives , Palladium/chemistry , Coordination Complexes/chemical synthesis , Crystallography, X-Ray , Ligands , Methane/chemistry , Models, Molecular , Molecular StructureABSTRACT
Oxidative addition: complexes containing an anionic NHC ligand with an unsubstituted nitrogen atom within the heterocycle have been prepared by oxidative addition of 2-chloro-N-methylbenzimidazole to Ni(0) and Pt(0). The "naked" nitrogen atom of the NHC ligand reacts as a strong nucleophile.
ABSTRACT
The ß,ß'-bis(triisopropylsiloxy)phenyl-1,4-diisocyanide 3 and [Ir(Cp*)Cl(2)](2) were used for the stepwise assembly of the [Ir(Cp*)Cl] cornered molecular square [6](Cl)(4). Synthesis of the tetrakis(diisocyanide) bridged molecular square [Ir(Cp*)Cl(3)](4)(BF(4))(4) [5](BF(4))(4) followed by cleavage of the O-Si(i-Pr)(3) bonds of the diisocyanide bridges with HCl/i-PrOH led to an intramolecular attack of the liberated hydroxyl groups at the isocyanide carbon atoms with formation of molecular square [6](Cl)(4) featuring four dicarbene linkers.
