Carbonylation metallated ring systems

A corollary of this treatment is that doao species appear capable of preparation from these arachno-ring systems by coordination to two metal-carbonyl residues in apical positions, on each side of the CnHn... 

The chemistry of unsaturated azepines is dominated by their polyene character. The absence of ir-delocalization confers instability on the ring system as witnessed by the many and various ring transformations undergone in acid and base solution, and under thermal and photolytic conditions. Most of the major reactions of azepines involve the neutral molecule e.g. cycloadditions (Section 5.16.3.8.1), metal carbonyl complexation (Section 5.16.3.8.2), dimerizations (Section 5.16.3.2.3) and photo- and thermo-induced valence isomerizations (Section 5.16.3.2.1). 

Many organic compounds react with carboxylic acids, acyl halides, or anhydrides in the presence of certain metallic halides, metallic oxides, iodine, or inorganic acids to form carbonyl compounds. The reaction is generally applicable to aromatic hydrocarbons. Benzene, alkylbenzenes, biphenyl, fluorene, naphthalene, anthracene, acenaphthene, phenanthrene, higher aromatic ring systems, and many derivatives undergo the reaction. 

Attempts to prepare chromium and iron carbonyl rr-complexes from a series of mixed condensed ring systems were successful, although the metals were bonded not to the heterocyclic but to the carbocyclic ring systems (LI) 45, 201, 378). AT-Ethoxycarbonylazepine and diazepine react with iron carbonyls to form [Fe(C0)j(C6HjNC02Et)] (LII R = COOEt)... 

Chlorine and bromine azides (N3X) react with Fe(CO)5 in an inert solvent at —20°C to form [Fe(CO)2N3]2X2 (X = Cl, Br), which exhibit the highest paramagnetism (5.29 BM) known for metal carbonyl derivatives. A planar FcjNj ring system (CXXVIII) was postulated on the basis of IR studies. With [M(CO)6] (M = Mo, W), chlorine azide in solution at ambient temperatures gave [M(C0)2N3C1] , assigned polymeric structures (CXXIX)... 

As with tetrahydro-1,3-oxazines the tetrahydro-1,4-oxazine ring system is stable to reduction by complex metal hydrides, and, for example, LAH can be used to reduce the lactam carbonyl function of mor-... 

Novel photochemical (and thermal) reactions of macrocyclic oxa-sila-acetylenic ring systems (expected to show unusual optical properties because of electronic effects arising from orbital overlap of the acetylenic n system with the silicon a bonds and the oxygen lone-pair electrons) were described. While thermolysis in the presence of a transition metal carbonyl compound gave cyclization to both benzenoid and fulvene species, photolysis in the presence of the transition metal carbonyl compound (which catalyzes 1,2-silyl shifts across a carbon-carbon triple bond) gave fulvene and vinylidene products, the latter being readily photolyzed to the fulvene 159 (equation 101). 

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