Manganese compounds carbene

Compounds Containing Metal-Carbon cr-Bonds of the Groups Titanium and Manganese, Including Carbenes and Carbynes... 

This facile approach to the carbene chemistry of rhenium has not yet been investigated with technetium. Further reactions with the technetium cluster 44a have been performed in C6H6/HC1 to yield the compound [( 6H6)Tc(CO)3]+ (66) which previously had only been described for manganese and rhenium [81]. "Tc-NMR of the latter compound exhibits a resonance at -1983 ppm (relative to [Tc04]- ), and it therefore fits very well into the range proposed for Tc(I) complexes. 

Carbonylation of the manganese carbene complex (tj5-C5Hs) (CO)2Mn=CPh2 to an analogous ketene complex has been reported (107). Compound 76 is also formed directly in the reaction of ketene with 45 (39). 

All Fischer carbene complexes presented in this work are air- and moisture-sensitive. The derivatives of 2 bearing electron-donating 7t-substituents and compound 5 do not decompose in substance and in dry solvents after a few weeks. The fact that corresponding Fischer carbenes of Mo and W prepared by the same method decompose even at low temperatures underlines once more the particular stability of manganese carbene complexes. 

For example, in attempts to realize benzannelation reactions, alkyloxy aryl carbene complexes of manganese failed to react with alkynes even in refluxing toluene, and the starting compounds could be recovered [4]. The documented low reactivity of the Mn as opposed to Cr and Mo carbene complexes may in part explain why the electrophilic carbene C-atom and the nucleophilic diazo C-atom tolerate each other in the same molecule. Besides, the bulky substituents at the silicon atom protect it fi"om being attacked by nucleophiles leading to desilylation as reported for trimethylsilyl substituted Cr carbene complexes [5]. 

Diazo compounds, precursors to carbenes, were prepared by the oxidation with active manganese(IV) oxide (or mercury(II) oxide) of the corresponding hydrazones which in turn were obtained from the corresponding ketones by the reaction with anhydrous hydrazine (or hydrazine monohydrate). This method was employed for the introduction of the diazo groups in most of our compounds... 

The reaction of the iron-carbene complex [[Bu C CC(OEt)=)Fe(CO)4] with 1,3-cyclohexadiene afforded223 (32), which was characterised by X-ray diffraction. The addition of the anionic derivatives of i-(diphenylmethane)-il-fluorene- and ii-(9,10-dihydroanthracene)-bis tricarbonylchromium to the hydrocarbon moiety (alkene, benzene, cyclohexadienyl, cycloheptadienyl and cycloheptatrienyl) in various cationic compounds of manganese, rhenium, iron, chromium, molybdenum, tungsten and cobalt was reported224 to provide a new route to hydrocarbon-bridged heteronuclear species such as (33). 

Reactions with Carbonyl Compounds Followed by Insertion Reactions. IV-Substituted -aminoketones react with TMSC(Li)N2 to give 2-pyrroUne derivatives via the alkylidene carbene intermediates by intramolecular N-H insertion, analogously to the reaction of -acyl-A(-tosylanilines with TMSC(Li)N2 (eq 21). Dehydrogenation of the 2-pyrrolines with active Mn02 (CMD, chemical manganese dioxide, produced for battery manufacture) affords the corresponding pyrroles (eq 24). ... 

Compound (30) was the first reported carbene complex with an optical centre in the a-position to a carbene carbon atom. A full paper has now given preparative details, and reports the absolute configuration determined by X-ray crystallography (the menthyl group is in the chair conformation). Other novel manganese carbenes were prepared from diazacyclopentadiene [equation (18)]. ... 

---