Metal-nitrogen triple bond

An excellent review of transition metal imido complexes appeared in 1980 (260). Transition metal imido complexes (NR R = H, alkyl, or aryl) are most common for Second and Third Row metals, but relatively rare for First Row metals. Three classes of imido complex are known. The majority of imido complexes are monomeric containing a terminal imido group which may adopt either a linear configuration (M=N—R) containing a formal metal-nitrogen triple bond as in [Os(N-fBu)03] and rans-[M(NH)X(dppe)2]+ (M = Mo or W X = CH30,... 

The cyanide ion is isoelectronic see Isoelectronic) with CO, N2 and NO+, with an electronic configuration of (la) (2a)2(3a) (4cr) (l7r)" (5a) this corresponds to a triple bond (one a-bond see a-Bond) and two tt-bonds see n-Bond)) between the carbon and nitrogen atoms. A lone pair see Lone Pair) of electrons is present on both atoms in CN. Calculations have indicated that the negative charge of the cyanide ion is shared approximately equally between the two atoms. The carbon-nitrogen triple bond distance is 1.16 A in the free cyanide ion the fundamental vibrational frequency of the C N bond (aqueous solution) is 2080 cm. The effective Crystallographic Radius of CN, as determined in cubic alkali metal cyanides, is 1.92 A this value is intermediate between those of chloride and bromide. 

Reactions with other carbon triple bonded functional groups. The substitution of nitrile for alkynes does not lead to pyridines or quinolines in the benzannulation reaction.Instead noncyclic products are obtained that are the result of insertion of the carbon-nitrogen triple bond into the metal-carbene bond. On the other hand, in a very recent report it was found that X -phosphaalkynes will undergo the benzannulation reaction to produce phosphaarene chromium tricafbonyl complexes. 

Freudenberger and Schrock reported the metathesis of the metal-carbon triple bond in 285 with the carbon-nitrogen triple bond in acetonitrile [Eq. (210)] (207). Metathesis-like reactions of 285 also occur with organic carbonyl groups to generate 0x0 vinyl metal complexes [Eq. (211)]... 

Reactions of N2 Complexes Only the most basic N2 complexes, notably the bis-dinitrogen Mo and W complexes, can be protonated. According to the exact conditions, various N2H complexes are obtained, and even, in some cases, free NH3 and N2H4. As strongly reduced Mo(0) and W(0) complexes, the metal can apparently supply the six electrons required by Eq. 16.21, and so the metals are oxidized during the process. Note, too, that in Eq. 16.28, the loss of the very strong N—N triple bond is compensated by the formation of two N—H bonds and a metal nitrogen multiple bond. 

Reaction (2) is a catalytic reduction of the carbon-nitrogen triple bond to a 1 ° amine. Just as a carbon-carbon triple bond can be reduced to a carbon-carbon single bond by hydrogen in the presence of a transition metal catalyst, a carbon-nitrogen triple bond can be similarly reduced. 

Burck S, Gudat D, Nieger M (2007) Metal-assisted, reversible phosphinyl phosphination of the carbon-nitrogen triple bond in a nitrile. Angew Chem Int Ed 46 2919... 

Very cold. Immersing a clean iron surface into liquid nitrogen at 77 K (—196 °C) yields a weak physisorptive bond. The N=N molecule is probably aligned parallel to the metal surface, with electron density donating from the centroid of the triple bond directly to iron atoms on the surface of the metal via a van der Waals type of interaction. The experimental value of A //fadsj is small at about 1.5 kJ mol-1. 

Figure 10.7 During the adsorption of molecular nitrogen onto iron metal, the two nitrogen atoms donate an increment of charge to adjacent atoms of iron on the metal surface, as depicted by the vertical arrows. The N=N triple bond cleaves partially, with a resultant bond order of about 1.5...

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