Carbene complexes spectroscopic properties

The isocyanide ligand, CNR, is formally isolobal with a carbene ligand. Several studies have investigated iron(Ill) porphyrin isocyanide complexes which have the general formula [FeCPorKCNR) ]. However, these studies have mostly been concerned with spin state and spectroscopic properties rather than chemical transformations and will not be discussed in detail here. Crystallographic details are given for two of the complexes. " ... 

A series of dinuclear gold(I)-carbene complexes of imidazolium-linked cydo-phanes and related acyclic bis(imidazolium) salts have been synthesized and their spectroscopic properties were examined by Baker and coworkers [31]. X-ray stmctural analysis of the cation in 1 and 2 (Scheme 5.1) revealed intramolecular Au - Au contacts of 3.5425(6) and 3.0485(3) A respectively. The electronic absorption... 

The mechanism of the ozonolysis reaction of alkenes has been investigated in the gas phase and solid state using matrix isolation spectroscopy. While alkene/ozone 7C-complexes and the primary ozonides are readily observed by IR und UV/vis spectroscopy, there is no direct spectroscopic evidence for the Criegee intermediate (carbonyl O oxide) in these reactions. However, these elusive species can be synthesized and characterized via the carbene/oxygen route. Comparison of experimental and calculated spectroscopic data allows for the prediction of the spectroscopic properties of carbonyl oxides which are not accessible by this method. 

The redox-active metalloligand [Ru(Cp) N=C-C(pz)3 ][PF6] reacts with [Ir(COD)Cl]2 giving a bimetaUic Ru -Ir complex [Ru(Cp) i-N=C-C(pz)3 Ir(COD)Cl2] [PFe] upon activation of the C=N moiety. This heterobimetaUic complex features an unprecedented metallacyclic alkyl-amido carbene core structure coordinated to an Ir center. A DFT study on structures, spin states, FMOs, and UV-VIS spectroscopic properties of [M(Tp)(CvH5N)(PPh3)(N3)] (M= Ru or Fe) has been carried out in order to understand whether Ru can be replaced by cheaper Fe in photosensitizers for DSSCs. ... 

Matsumoto K, Matsnmoto N, Ishii A, Tsukuda T, Hasegawa M, TsubomuraT. Sttnc-tural and spectroscopic properties of a copper(l)-bis(N-heterocyclic)carbene complex. Dalton Trans. 2009 6795-6801. 

In this article it has been shown, that the low temperature photopolymerization reaction of diacetylene crystals is a highly complex reaction with a manifold of different reaction intermediates. Moreover, the diacetylene crystals represent a class of material which play a unique role within the usual polymerization reactions conventionally performed in the fluid phase. The spectroscopic interest of this contribution has been focussed mainly on the electronic properties of the different intermediates, such as butatriene or acetylene chain structure, diradical or carbene electron spin distributions and spin multiplicities. The elementary chemical reactions within all the individual steps of the polymerization reaction have been successfully investigated by the methods of solid state spectroscopy. Moreover we have been able to analyze the physical and chemical primary and secondary processes of the photochemical and thermal polymerization reaction in diacetylene crystals. This success has been largely due to the stability of the intermediates at low temperatures and to the high informational yield of optical and ESR spectroscopy in crystalline systems. 

The increased donor properties of non-classical carbenes relative to their classical analogues were demonstrated both theoretically and experimentally. Complexes 14 and 15 were analysed by X-ray photoelectron spectroscopy. Both the palladium 3d and 3p electron binding energies in the abnormal complex 15 were lower by 0.5 eV than in the normal complex 14, which reflected the stronger donor capabilities of the abnormal carbene ligand. Furthermore, X-ray diffraction and infrared spectroscopic studies were used to demonstrate the larger trans influence of abnormal carbenes when compared to their normal analogues. ... 

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