Homoleptic anionic complexe ligands

Cyanide complexes of molybdenum(II) generally appear elsewhere under other classifications, where CN- is an andlliary ligand. The homoleptic anions [Mo(CN)6]4- and [Mo(CN)7]5- (pentagonal bipyramid) have been reviewed elsewhere.10... 

Routes to homoleptic isocyanide complexes have been defined in thf (Scheme 46). Ta L6 (L = xylyl isocyanide) was reduced by ACg (A = K, Cs) to [Ta 1L6]. This anion appears to be octahedral. Its 13C NMR resonance occured at 210 ppm, the most downfield shift observed for a diamagnetic homoleptic isocyanide complex. Reaction with the NO source N-methyl-N-nitroso-/ -to 1 uenes u 1 lbnam ide provided Ta I(NO)L5 whose essentially linear NbNO fragment is consistent with the formal presence of ligand NO+. Direct nitrosylation of [M (CO)6] with 2 eq [NO][PF6] in the presence of L in CH2C12 at — 60 °C provided r/,v-[M (NO)2L4]1,662 The reaction represents a rare example of non-oxidative displacement of all CO ligands from a homoleptic carbonylme-talate. 

Homoleptic anionic zirconium and hafnium phosphine complexes have recently been prepared using bisphosphinine ligands, which are phosphine analogs of the ubiquitous bipyridyl ligand. Structure determinations of the Li3(solv)Cl salts were performed (solv = DME for M = Zr and THF for M = Hf) show the overall geometry around the metal center to be trigonal prismatic. Disruption of the aromaticity is... 

The first X-ray evidence for a carbene-lithium adduct, 18, obtained by Arduengo and Tamm, was reported in a paper by Boche et al.. [51 ] Although full details of this structure have not appeared, the imidazol-2-ylidenes in 18 have N-C bond lengths and N-C-N angles which are very similar those in the free carbene. Other reported lithium complexes include 19, [22] and a homoleptic complex containing two of the anionic tripod ligands 20 wrapped around two lithium ions. [23]... 

A number of general features in Table 1-3 is apparent. Complexes may be cationic, neutral or anionic. Ligands may be simple monatomic ions, or larger molecules or ions. Many ligands are found as related neutral and anionic species (for example, water, hydroxide and oxide). Complexes may contain all of the same type of ligand, in which case they are termed homoleptic, or they may contain a variety of ligand types, whereby they are described as heteroleptic. Some ligands such as nitrite or thiocyanate can coordinate to a metal ion in more than one way. This is described as ambidentate behaviour. In such cases, we commonly indicate... 

This review deals with the chemistry and coordination complexes of isoelectronic analogues of common oxo-anions of phosphorus such as PO3, POl", RPOl" and R2POy. The article begins with a discussion of homoleptic systems in which all of the 0x0 ligands are replaced by imido (NR) groups. This is followed by an account of heteroleptic phosphorus-centered anions, including [RN(E)P(/<-NR )2P(E)NR]2-, [EP(NR)3]3-, [RP(E)(NR)2] and [R2P(E)(NR )] (E=0,S, Se, Te). The emphasis is on the wide variety of coordination modes exhibited by these poly-dentate ligands, which have both hard (NR) and soft (S, Se or Te) centers. Possible applications of their metal complexes include new catalytic systems, coordination polymers with unique properties, and novel porous materials. 

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