Isocyanide, ligand chemistry

Small-molecule isocyanides possess a ligand chemistry which is only slightly less well-developed (5). 

Some interesting chemistry has appeared relating to the ability of the isocyanide ligand to stabilize unusual oxidation states. A series of palladium metal - metal bonded complexes has been synthesized by redox reactions involving two metal complexes in different formal oxidation states (33 -35). Similar ruthenium(I) and osmium(I) dimers have been prepared by an unusual homolytic fission of a ruthenium-carbon bond (36) or by singleelectron oxidation of Os(CNXylyl)5 (18). 

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... 

Examples in organocopper chemistry are the synthesis of h -cyclopentadienyl-copper complexes with phosphite, phosphine or isocyanide ligands via the reaction of h -CjHjTl with Cu(I) halide-ligand complexes in pentane or THE at 25°C . 

Complexes of Crlv with alkyl,216 alkylidene,217 or r/-carborane218 ligands are extensively studied as model compounds for Cr-based alkene polymerization catalysts (Section 4.6.5.1.2). These complexes are described in detail in the Comprehensive Organometallic Chemistry series. A CrIV complex with isocyanide ligands is described in Section 4.6.4.2.I. 

Most metals are electron-attracting with respect to isocyanide ligands and the coordinated ligand is sensitive to nucleophilic attack. This reversal in behaviour is called Umpolung , a term introduced by Seebach . Umpolung is an important feature in organometallic chemistry. An example of such a nucleophilic attack is the initiation step in the polymerization of isocyanides by nickel(II) complexes ... 

The first synthesis of a complex containing a metal-carbon triple bond was reported in 1973 [1]. Since then, numerous carbyne complexes have been prepared. In recent years, the study of the reactivity of these complexes has attracted considerable interest [2]. E.g. carbyne complexes have extensively been used as building blocks in the synthesis of transition metal clusters [3]. The coupling of carbyne ligands with CO or isocyanide ligands has also been studied in detail [4]. However, the number of reports on the use of carbyne complexes in synthetic organic chemistry is rather limit in contrast to carbene complexes which have found many applications in the synthesis of carbo- and heterocycles [5]. 

Iron carbonyl complexes with cyanide or organic isocyanide ligands have been presented in Section 6.01.4.1. The chemistry of those compounds is related to the preparation of compounds which contain both cyanide and S-donor ligands. Reaction of FeCl2 with [Et4N]CN or organic isocyanides in the presence of CO and thiolate ligands is a convenient entryway into this class of compounds (Scheme 75). ... 

Other cyanide complexes arc discussed under the appropriate metals. In organic chemistry, both nitriles R-CK and isonitriles (isocyanidcs) R-NC are known. Isocyanides have been extensively studied as ligands (p. 926). More... 

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. 

Cavell KJ, McGuinness DS (2007) Palladium complexes with carbonyl, isocyanide and carbene ligands. In Crabtree RH, Mingos DMP, Canty AJ (eds) Comprehensive organometallic chemistry 111. Elsevier, Amsterdam... 

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