Halide donor ligands

Ruthenium(ii).—Group VII Donors. Halide donor ligands. A study has shown that the blue complexes obtained by electrolytic reduction of H2[RuCl5H20] in acidic solution are further examples of mixed Ru -Ru complexes. They were previously assumed to contain only Ru . Dimers of the type Ru2Ch3Vi, (n = 0,1, or 2) were separated and isolated using ion-exchange chromatography. 

McMillan, and E. Ochiai, Inorg. Nuclear Chem. Letters, 1972, 8, 239. 

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Oxidative addition occurs readily with allylic halides. Donor ligands (tertiary phosphines, bipyridyl, halide ions) and anionic complexes are required for activation of aromatic and vinyl halides (4, 70). Certain aliphatic halides are also reactive. The intermediate species R—Ni—X... 

Most V(II) complexes have predominantly N-, 0-, S-, P-, and halide donor ligands. They are presented below in terms of the predominant ligand in the coordination sphere. 

There is also clear evidence of a change from predominantly class-a to class-b metal charactristics (p. 909) in passing down this group. Whereas cobalt(III) forms few complexes with the heavier donor atoms of Groups 15 and 16, rhodium(III), and more especially iridium (III), coordinate readily with P-, As- and S-donor ligands. Compounds with Se- and even Te- are also known. Thus infrared. X-ray and nmr studies show that, in complexes such as [Co(NH3)4(NCS)2]" ", the NCS acts as an A -donor ligand, whereas in [M(SCN)6] (M = Rh, Ir) it is an 5-donor. Likewise in the hexahalogeno complex anions, [MX ] ", cobalt forms only that with fluoride, whereas rhodium forms them with all the halides except iodide, and iridium forms them with all except fluoride. 

M(N03)4] anions containing the unusual unidentate niirato ion are also known. Fluoro complexes are even less prevalent, the preference of these cations being for the other halides, cyanide, N- and heavy atom-donor ligands. 

Iron hydride complexes can be synthesized by many routes. Some typical methods are listed in Scheme 2. Protonation of an anionic iron complex or substitution of hydride for one electron donor ligands, such as halides, affords hydride complexes. NaBH4 and L1A1H4 are generally used as the hydride source for the latter transformation. Oxidative addition of H2 and E-H to a low valent and unsaturated iron complex gives a hydride complex. Furthermore, p-hydride abstraction from an alkyl iron complex affords a hydride complex with olefin coordination. The last two reactions are frequently involved in catalytic cycles. 

Complexes with halide and hydride donor ligands 979... 

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