Complexes mononuclear

Dehydration of propargyl alcohols occurs commonly on mononuclear ruthenium complexes.[ l Water is formed from the terminal alkynic hydrogen and by the alcoholic OH this is the more common dehydration process (it is denoted Route A). These reactions afford organic intermediates leading to cumulene complexes useful for the synthesis of doped polyacetylenes or of non-linear optic materials. Dehydration of rhodium-coordinated propargyl alcohols leads to free or coordinated cumulenes and can be catalyzed by alumina and chloride ions, Fig. 16. 

Surface-catalyzed isomerization of mononuclear alkynyl tungsten complexes to allyl derivatives has also been reported it occurs on silica gel.  

The literature contains several examples of deprotonation of dipropargyl alcohols on mononuclear ruthenium complexes leading to dimeric derivatives linked by five 

Reverse processes, that is reactions of propargyl or allenylidene ligands coordinated to mononuclear centers with water, methanol, amines, and other ligands are known. Tungsten l and platinum complexes give a series of reactions (some of which are mediated by surfaces) comparable with those discussed for clusters. 

Finally, insertion of alkynes into dihydrogen mononuclear cationic rhenium complexes, stabilized by the triphos (= l,l,l-tris(diphenylphosphinomethyl)ethane) ligand, leads to vinylidene derivatives which react with water or ethanol eliminating silanols or methane, Fig. 18. Solvents were acetone or THF no chromatography was used. 

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Pt(PPh3)4] reaction also occurs with elimination of PPh3 but the product is the yellow, planar, mononuclear complex lPi( j -02)(PPh3)2] (Fig. 14.6b).t >... 

Other mononuclear complexes include the tetrahedral [Mo(NMe2)r] and the octahedral Li2[Mo(N Me2)6].2thfi hut recent interest in the chemistry of the M" ion has eentred on the trinuclear 0x0 and thio complexes of Mo and W, particularly the former. They are of three main types. The first may be conceptually based on the [M3O11I unit found in the aquo ions [.M304(H209] (M = Mo. W). It contains a... 

Reactions of the metallocene derivatives of molybdenum with pyrazole lead to the mononuclear complexes of the type 22. Structure 22 shows that it cannot be used as a ligand for the preparation of dinuclear complexes owing to geometric constraints [80JOM( 197)291 83JOM(253)53]. In acetone, an unusual complex 23 is formed [83JOM(253)53]. The bidentate ligand is the product of the reaction of pyrazole and acetone. 

Sodium pyrazolate and 3,5-dimethylpyrazolate, [( " -cod)Rh(/A-Cl)]2, carbon monoxide, 3-(diphenylphosphino)benzoic acid, or (2-formylphenyl)diphenyl-phosphine give rise to complexes 120 (R = H, Me) and 121 (R = H, Me) [94JOM(469)213]. However, 2-(diphenylphosphino)benzoic acid (the carboxyl group in the ortho position) leads to formation of the mononuclear complexes 122. The products appear to be catalysts for hydroformylation reactions [93MI2]. 

Diphenylimidazole with palladium acetate forms the cyclometallated complex 80 (X = OAc) (97AOC491). The acetate group is replaced by chloride or bromide when 80 (X = OAc) reacts with sodium chloride or lithium bromide, respectively, to give 80 (X = C1, Br). Bromide with diethyl sulfide forms the mononuclear complex 81. Similar reactions are known for 1 -acetyl-2-phenylimidazole (96JOM(522)97). 1,5-Bis(A -methylimidazol-2-yl)pen-tane with palladium(II) acetate gives the cyclometallated complex 82 (OOJOM (607)194). 

Dimethyl-1,2,4-triazolium iodide with palladium acetate yields the carbene adduct 182 (97JOM(530)259). Under water it undergoes cis-trans isomerization to 183. Some other derivatives were reported in 1981 (81BCSJ800). 1,1 -Methylenebis(4-alkyl-l,2,4-triazolium)diiodides (alkyl = /-Pr, n-Bu, octyl) with palladium(II) acetate give the mononuclear complexes [L Pdl ] (99EJIC1965), where L2= l,l -methylenebis(4-R-l,2,4-triazol-2-ylidene) (R = /-Pr, n-Bu, octyl). Thermolysis of the products in THF gives the rran -dinuclear complexes 184... 

Hie stabilizing effect of additional donor molecules is nicely illustrated by the increase in decomposition temperatures seen on going from MeCii t< -15 C) to CiiMefPPb )- , wbicli decomposes at about 75 C [49]. Hie structure of tlie latter compound in tlie solid state fsee Fig. 1.5) comprises a mononuclear complex witli... 

Some important mononuclear complexes exist such as mer-RuH(OAc)-(PPh3)3, a very efficient catalyst for the selective hydrogenation of alk-l-enes (Figure 1.36). 

They resemble the oxygen-bridged [M2OC1io]4- (section 1.3.6) (Figure 1.75) with M-N stretching frequencies similar to those in the mononuclear complexes (1108 cm-1 in [Os2N(NH3)gCl2]Cl3). 

Mononuclear complexes of palladium and platinum in the +3 oxidation state have only recently been unequivocally characterized [157]. The major advance has come in complexes with macrocyclic ligands such as 1,4,7-trithiacyclononane (ttcn) and 1,4,7-triazacyclononane (tacn) (Figure 3.96). 

The interaction of small, well defined, rhodium clusters, Rh and Rhs, with O2 has been investigated (220) by matrix infrared, and UV-visible, spectroscopy, coupled with metal/02 concentration studies, warm-up experiments, and isotopic oxygen studies. A number of binuclear O2 complexes were identified, with stoichiometries Rh2(02)n, n = 1-4. In addition, a trinuclear species Rhs(02)m, m = 2 or 6, was identified. The infrared data for these complexes, as well as for the mononuclear complexes Rh(02)x, = 1-2 (229), are summarized in Table XI. Metal-concentration plots that led to the determination of... 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

Further examples of emissive cyclometallated gold(III) complexes are [Au(L)Cl] (L = tridentate carbanion of 4 -(4-methoxyphenyl)-6 -phenyl-2,2 -bipyridine) [53], as well as mono- and binuclear bis-cyclometallated gold(III) complexes, namely [Au (C N C )L ]" (C N C = tridentate dicarbanion of 2,6-diphenylpyridine L = depro-tonated 2-mercaptopyridine (2-pyS ), n = 0 L = PPh3 or 1-methylimidazole, n = 1) and [Au2(C N C )2(P P)](C104)2 (P P = dppm, dppe) respectively [54]. The crystal structures of the binuclear derivatives show intramolecular interplanar separations of 3.4 A between the [Au(C N C)] moieties, implying the presence of weak n-n interactions. The mononuclear complexes show absorption with vibronic structure at 380-405 nm (e > 10 cm ), attributed to metal-perturbed intraligand transition. 

The gold(III) complexes, ]Au(C N C)L ]" and [Au2(C N C)2(P P)[(C104)2 are emissive in acetonitrile at low temperature. The frozen-state (77 K) emission spectra of the mononuclear complexes [Au(C N C )L [" show well-resolved vibronic structures with spacings in the 1100-1300 cm range, which correlate with the skeletal vibrational frequency of the tridentate C N C ligand. By comparing the emission... 

There have been few reports of purine derivatives1 that contain metal-carbon nucleobase binding (75), and those that have been described are often polymetalated (84). Quite recently mononuclear complexes of adenine and guanine have been prepared that contain... 

Blinc R (2007) Order and Disorder in Perovskites and Relaxor Ferroelectrics. 124 51-67 Boca R (2005) Magnetic Parameters and Magnetic Functions in Mononuclear Complexes Beyond the Spin-Hamiltonian Formalism 117 1-268 Bohrer D, see Schetinger MRC (2003) 104 99-138 Bonnet S, see Baranoff E (2007) 123 41-78... 

Mononuclear Complexes with Open-chain Ligands Containing Mixed Donor Atoms 346... 

The cyanato ligand generally tends to bind through its N atom to Ni11 and acts as an N-bound terminal ligand in mononuclear complexes. Complexes of the type [Ni(NCO)2L4] (L = py, H20)... 

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