N-donor complexes

Table 14. Standard enthalpies of sublimation, formation and disruption and bond enthalpy contributions, iT(W-N) kJ mol-1, for N-donor complexes of tungsten W(CO)6 nLn]...

The next section concerns oxoruthenates with 0-donor hgands (oxo, hydroxo, carboxylato) first, followed by halo donors and finally a substantial section on the rapidly growing area of N-donor complexes. 

Pyridine and pyrazine can also replace up to three of the carbonyl groups in Group VI metal carbonyls to form compounds of type Cr(CO)3py3. The reaction of 4,5,6-triphenyl-l,2,3-triazine with nonacarbonyldiiron afforded 3,4,5-triphenylpyrazole in 80% yield, probably through the initial n-donor complexation of the triazine to iron carbonyl (87BCJ3062). 

Due to the low solubility of cobalt(II) fluoride in most solvents, formation of cobalt fluoro N-donor complexes (which are the only low-valent cobalt fluorides which are reliably reported) features a variety of starting materials. A common theme that runs throughout this work has been the use of [Co(BF4)2] as the fluoride source, and the subsequent controlled decomposition to obtain a metal-bound fluoride. This has been done, for example, with tris- (3,5-dimethyl-pyrazol-l-yl)methyl amine (amtd) to give [M2(amtd)2F(BF4)3(EtOH)Y(H20)] (M = Co, Cu, Zn x = 0-1.5, y = 1-2). The cobalt complex has been structurally characterised by X-ray diffraction [Fig. 3] [57]. Similarly, the combination of [M(BF4)2] (M = Mn, Co, Ni), [M(N03)2], NH4(NCS) and 3,5-diethyl-1,2,4-triazole (detrH) produces... 

The addition of the 0s04— N donor complex 3 to alkenes is a much faster process and accounts for the rate acceleration of alkene stoichiometric osmylations in the presence of this and other amines10. 

It seems well established that aluminium bromide is monomeric in methyl bromide, according to some fairly old work on flie ebullioscopy of this system More recent Raman studies have confirmed that the amount of dimerisation of AlBrs is indeed minimal, but that between —90 and 0 °C this Lewis acid is present in these solutions as a 1 1 n-donor complex witii the solvent. Interestin y, AlBts was also found to be monomeric in methylene chloride but the authors emphasised that this situation did not exclude the homoconjugation of the anion following selfionisation ... 

An extensive and a systematic photochemical studies had been done on 2-isoxazoline. Photolysis of 2-isoxazolines always result in a mixture of products, depending upon the nature of the substituents. Three possible different pathways of photolytic cleavage are reviewed <9iHC(49)l>. Ultraviolet irradiation of 5-unsubstituted 2-isoxazoline (127) in the presence of iron pentacarbonyl, resulted in ring fragmentation products (a ketone (128) and aldehyde (129)) as well as N—O bond fission products ((130) and (131)) (Scheme 21). The plausible mechanism involves N-donor complexation with photochemically generated pentacarbonyl, prior to N—O and C(3)—C(4) bond fissions <83CL51>. 

A comparative study has appeared of the X-ray photoelectron spectra of a range of Ag and Ag N-donor complexes. The Ag 3 3/2 and 3 5/2 binding energies show little dependence on the formal oxidation state, but peak widths are usually considerably broader ca. 0.8 eV) for the paramagnetic Ag species. This increased width may be caused partly by the presence of multiplet splittings . In the course of these studies the new orange-brown isoquinoline-1-carboxylato-complex [AgL2] was also isolated ... 

Also poorly studied is the electrocatalytic behavior of complexes 5 and 8, which both contain a proximal imidazole (pyridine) ligand and a distal chelate comprising aliphatic N donors. Complexes 5a-bFeCu and SFeCu were reported to catalyze mainly 4e reduction of O3 (although at unspecified and probably abiologi-cally reducing potentials) . In contrast, a structurally related complex ScFeCu... 

L. Toniolo, A. Immirzi, U. Croatto, and G. Bombieri, Inorg. Chim. Acta, 1976,19,209. Fluxional N-donor complexes of Pd and Pt . 

Many years later, two heterogeneous systems based on polymer supported LAs emerged. One class (Chart 9) is based on crosslinked polystyrene (PS) supports where the LA components can be bound as pi complexes (PS-7i LA), n-donor complexes (PS-n- LA), or by covalent bonds (PS-LA) depending on the functional groups present on the support [187, 188]. The first two variants are capable of producing medium MW PIBs at ambient temperatures in nonpolar media. This system is also unique in that the supported LA can be reused multiple times. The other system is based on... 

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