Isocyanides ligands, transition metal

Cationic 1,2-silyl migration was proposed to be involved during the reactions of carbon monooxide and isocyanides with transition metal-carbon bonds (ligand distribution) (equation 18)55-65. Typically, the reaction of l-sila-3-zirconacyclobutane 29 with carbon monooxide afforded a dioxasilazirconacyclohexane derivative 30. The reaction was considered to proceed via a CO insertion into a Zr—C bond followed by a 1,2-silyl migration as shown in equation 1960. This type of reactions are well-documented in a review of Durfee and Roth well66. 

The field of transition metal complexes of isocyanides developed slowly over more than a century to a respectable subarea in coordination chemistry, and in the process seems to have attracted very little attention. Even the remarkable resurgence of transition metal organometallic chemistry in the last 20 years, and the realization that isocyanides and carbon monoxide should be quite similar as ligand groups in organometallic complexes, did not initiate an extensive development of this area of chemistry. Only in the last several years has this potentially important subject begun to receive the attention it would seem to deserve. 

The aqua ion is not easily reduced nor oxidized. It is the slowest reacting of the bivalent transition metal ions with e " k = 7.7 X 10 M s ) and the product Mn+q is very reactive. However Mn(CNR)5 (R = a variety of alkyl and aryl groups) is stable and the selfexchange in the Mn(l,ll) hexakis(isocyanide) system has been studied by Mn and H nmr line broadening. The effects of solvent, temperature, pressure and ligand have been thoroughly explored. 

Both 2-azido [184] and 2-nitrophenyl isocyanides [185] are suitable synthons for the generation of the freely unstable 2-aminophenyl isocyanide and they have been used (Fig. 23) in the template-controlled preparation of NH,NH-stabilized benzim-idazolin-2-ylidene hgands. Both phenyl isocyanides coordinate readily to transition metal centers. The isocyanide ligand in complex 65 reacts with PPhs and the... 

Organic isocyanides (C=N-R) are versatile ligands in transition metal complex chemistry. As compared with their pseudo-isoelectronic cousin, C=0, they are stronger o-donors [1], As a result, isocyanides form more stable complexes with metals in relatively high oxidation states (e.g., +2 and +3) than CO. In contrast, they have a lower ir-accepting ability than CO and therefore form less stable complexes with metals in low oxidation states (e.g., -1 and -2). Nevertheless, they form a broad range of metal complexes, and various aspects of their syntheses, structures and bonding have been reviewed [1-7]. 

The migratory insertion of alkyl and aryl isocyanides into metal alkyl bonds produces an iminoacyl function. The early transition metal iminoacyl, like its oxygen counterpart, has been shown to bond in a dihapto fashion.62 It has recently been shown that it is possible to couple either an acyl and art iminoacyl or two iminoacyls on the metals titanium or zirconium to produce enamidolate and enediamide ligands, respectively (equation 34).62,63... 

For copper the 3d orbitals can be expected to make less than their full contribution to metal-ligand bonding as in other main group transition metal compounds (57). This is suggested by the infrared spectra of cyclopentadienylcopper complexes with methyl isocyanide or carbon... 

The interests in homoleptic (see Homoleptic Compound) isocyanide ( isonitrile, see Isocyanide Ligands) complexes of transition metals have largely been associated with their similarities to metal carbonyls. The greater versatility of isocyanide ligands in comparison to CO makes isocyanide complexes potentially valuable reagents in synthetic chemistry and catalysis. The dication [V(CNBu )6] reported in 1980 remained the sole example of a homoleptic group 5 metal isocyanide until 1999, when the first binary... 

Carbon-transition metal bonds can also be formed by cocondensing transition-metal atoms with isonitriles. Thus, using Ni and Fe with t-butyl isocyanide, methyl isocyanide, cyclohexyl isocyanide and vinyl isocyanide the NiL4 and FeL, complexes are formed. Palladium cocondensed with isonitriles yields PdLj polymeric structures with terminal and bridged isonitrile ligands ... 

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