Ligands n-acceptor

Cis Effects in Osmium Porphyrins with n-Acceptor Ligands... 

The results obtained allowed one to establish the sequence of electroreduction potentials for Au complexes with n-acceptor ligands. 

The high basicity of the cation [Cp2V]+, generated from Cp2VCl in aqueous solution, has been shown by the rapid formation of [Cp2VL2]+ (L2 = (CO)2, (CNC6Hm)2, dpe) with n-acceptor ligands (201, 202). 

The addition of a n-acceptor ligand type NO can increase the stability of dimers, decreasing at the same time the multiplicity of the metal-metal bond ... 

Other geometries than octahedral will also obey the rule - given n acceptor ligands - if nine bonding MOs can be constructed, although VB theory is often adequate. For example, in a tetrahedral complex we... 

Like most rules in bonding theory and structural chemistry, the 18-electron rule is often violated, even among the nonclassical complexes containing n acceptor ligands where, we have suggested, it should apply. Square planar complexes follow a 16-electron rule examples include Wilkinson s catalyst Rh(PPh3)3Cl (see also Section 9.8) and the vast number of square Pt(II) complexes. 

Most compounds with triple and quadruple bonds are formed by Re, Cr, Mo, and W. The ligands in such compounds are in general relatively hard Lewis bases such as halides, carboxylic acids, and amines. Nevertheless, in some cases n-acceptor ligands such as carbonyl, phosphines and nitrile are also present. 

With n-acceptor ligands, the M=M bonds are usually cleaved to give mononuclear products, which are sometimes inaccessible by any other synthetic route. 

Whereas the d-n overlap is modest in the Ni2+ CO surface complexes, this is not necessarily true when a stronger n-acceptor ligand such as NO is used to probe the surface Ni2+ ions located on (001) faces of NiO or... 

Note In the present case, the excellent n-acceptor ligand carbonyl is replaced by the good... 

Note The better n-acceptor PPh gives a higher N-benzylaniline to Schiff base ratio than the weaker n-acceptor ligand PCy ... 

Though largely unstudied, it has recently been shown that Ir-catalyzed allylic substitution reactions where a strong n-acceptor ligand, for example, triphenylphosphite, is present... 

Complexes of Pt can be tetrahedral, planar three-coordinate, or hnear two-coordinate. Soft ligands and n-acceptor ligands are required to stabilize this low oxidation state. Acetylenes ([Pt(/ -PhC=CPh)2]), olefines (([Pt() -PhCH=CH2)3)]), and especially phosphines are the most common ligands found in zerovalent complexes of platinum. Compounds with mixed ligands, including p-block elements donor ligands, are also known. 

Figure 6.17 MO energy level diagrams which include nonbonding ligand n orbitals for an octahedral complex, [MLg] (a) n donor ligands (b) n acceptor ligands. The terms LMCT and MLCT are discussed in Section 7.2.2...

Octahedral transition metal complexes containing strong n acceptor ligands obey the 18-electron rule much more often than complexes containing n donor ligands. Why ... 

One other binary carbonyl does not obey the rule the 17-electron V(CO)6. This complex, which is pyrophoric and much less thermally stable than the 18-electron Cr(CO)6, is one of a few cases in which strong n acceptor ligands do not succeed in requiring an 18-electron configuration. In V(CO)6 the vanadium is apparently too small to permit a seventh coordination site hence, no metal-metal bonded dimer [which might potentially yield 18-electron (CO)6V-V(CO)6] is ordinarily possible.10 However, V(CO)6 is easily reduced to [V(CO)6] , a well-studied 18-electron complex. 

In recent years, several dozen compounds containing the isoelectronic NS (thionitrosyl) ligand have been synthesized. Infrared data have indicated that, like NO, NS can function in linear, bent, and bridging modes. In general, NS is stronger than NO in its ability to act as a n acceptor ligand the relative abilities of NO and NS to accept n electrons depend on the electronic environment of... 

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