1,4-Diaza-1,3-butadienes complexes

Finally, ligands containing the system — RC=NR appear to be able to complex to metals either by forming N-M azabuta-diene derivative, 3.37 [94]. 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

An Ru—Mn bond is present in the complexes [(CO)5MnRu(Me)(CO)2L] where L is N,N -diisopropyl-1,4-diaza-1,3-butadiene, or pyridine-2-carbaldehyde-A-isopropylimine crystallographic... 

Diaza-l3-butadiene Metal Complexes Synthesis, Occurrence and Properties 208... 

DIAZA-l,3-BUTADIENE (a-DIIMINE) METAL COMPLEXES 13.5.3.1 Introduction... 

Metal complexes of the 1,4-diaza-1,3-butadiene ligands [RN=C(R )C(R")=NR = R-DAB R, R" ] have recently been surveyed by van Koten and Vrieze.111,112 Therefore we will refer extensively to these reviews and to some key references and we will discuss here the main points and new results. The discussion will be restricted to the above ligands, with passing mention of complexes of 2-pyridinecarbaldehyde-JV-imines, which are discussed in Chapter 13.2. 

Diaza-l,3-butadiene Metal Complexes Synthesis, Occurrence and Properties 13.5.3.4.1 Monodentate bonded 1,4-diaza-l,3-butadiene ligands (a-N two electron)... 

Valinomycin metal complexes, 969 Vanadium complexes acetylacetone exchange reactions, 380 1,4-diaza-l,3-butadiene, 209 dioxygen mononuclear, 321 hydrazido(2-), 148 hydroxamic adds, 506 phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 824 dioxygen adducts, 325... 

Diaza-1,3-butadiene (a-Diimine) Ligands Their Coordination Modes and the Reactivity of Their Metal Complexes, 21, 152 Diene-Iron Carbonyl Complexes, 1, 1... 

Diaza-l,3-butadienes niobium complexes, 5, 89 with platinum(II), 8, 463... 

Low-valence transition metal complexes of a-diimine ligands are highly colored because of the presence of low-energy metal to a-diimine charge transfer (MLCT) transitions. For a series of d6-M(CO)., (a-diimine) (M=Cr,Mo,W) and d8- M (CO)3 (a-diimine) (M =Fe, Ru) complexes, we have studied the spectroscopic and photochemical properties (1-10). The a-diimine ligands used are 1,4-diaza-1,3-butadiene (R-DAB), pyridine-2-car-baldehyde-imine (PyCa), 2,2 -bipyridine (bipy) or 1,10-phenanthroline (phen) molecules. A close relationship was deduced between the photochemical behavior of these complexes and their resonance Raman (rR) spectra, obtained by excitation into the low-energy MLCT band. 

In addition to the complexes listed above, the following chelates belonging to the class containing an MN4 unit have been obtained on the basis of l,4-diaza-l,3-butadiene [1, vol.2 470], tetra-aza-1,3-butadiene [1, vol.2], penta-azadienes [471], azomethines of 2,5-diformylpyrrole [472,473], cyclic hydrazones and thiosemi-carbazones [262], dibenzotetra-aza[14]annulene [474], hetarylaminoazocompounds [8,404,475], azoazine radicals [476], Schiff bases of heterocyclic series [132,133,477], and azoleazines [132,133,478,479]. 

Transition metal-carbonyl-diimine complexes [Ru(E)(E ) (CO)2(a-diimine)] (E, E = halide, alkyl, benzyl, metal fragment a-diimine = 1, 4-diazabutadiene or 2,2 -bipyridine) are widely studied for their unconventional photochemical, photophysical, and electrochemical properties. These molecules have a great potential as luminophores, photosensitizers, and photoinitiators of radical reactions and represent a challenge to the understanding of excited-state dynamics. The near-UV/visible electronic spectroscopy of [Rn(X)(Me)(CO)2(/Pr-DAB)] (X = Cl or I iPr-DAB = A,A -di-isopropyl-l,4-diaza-l,3-butadiene) has been investigated throngh CASSCF/C ASPT2 and TD-DFT calculations on the model complexes [Ru(X)(Me)(CO)2(Me-DAB)] (X = Cl or I) (Table 2). 

Enantioselective cyclooligomerizations of butadiene can also be achieved when a chiral diaza-diene-iron(II) chloride complex and a fourfold excess of ethylmagnesium iodide are used. Optical yields of 9 to 16% are obtained with two chiral diazadienes of the type R N = CRCR = NR, prepared by formic acid catalyzed condensation of aqueous glyoxal (R1 = H) or 2,3-butadione (R1 = CH3) with (R)-l-phenylethylaminc or (1S,2S,3S,5R)-3-(aminomethyl)pinane. The (di-azadienc)iron(0)-catalyzed dimerization of butadiene also gives 4-vinylcyclohexene with up to 16% ee60. 

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