Treatment Of Trans Research Articles

Allenylidenes: their multifaceted chemistry at rhodium

Rhodium allenylidenes, which represent a class of ‘flat’ metallabutatrienes, are useful tools for the generation of metal-bound species that are hardly accessible (sometimes not accessible at all) by other synthetic routes. In contrast to various octahedral allenylidene metal complexes, e.g. of Cr 0 , Mn I or Ru II , the square-planar rhodium compounds trans- [RhX(CCCRR′)(PPr i 3 ) 2 ] are attacked by both nucleophiles and electrophiles. Moreover, non-polar substrates such as H 2 or Cl 2 react cleanly with the title complexes to give products in which the allenylidene unit is preserved as part of a newly formed ligand. Attempts to prepare a square-planar cationic metallaheptahexaene, trans-[Rh(CCCRR′) 2 (PP r i 3 ) 2 ] + , unexpectedly led to the formation of two isomeric hexapentaenerhodium(I) complexes of which the isomer having the polyene coordinated in an unsymmetrical fashion is the thermodynamically more stable. C–C coupling reactions also occur on treatment of trans-[RhCl(CCCPh 2 )(PPr i 3 ) 2 ] with vinyl Grignard reagents or phenylacetylene leading to highly unsaturated RhC 5 and RhC 5 P frameworks from which vinylallenes and phosphacumuleneylides are obtained.

Reactions oftrans-[Mo(CNMe)2(PMe2Ph)4] andmer-[W(CNMe)3(PMe2Ph)3] complexes with methanol and with mineral acids to give amines, ammonia and hydrocarbons

Treatment oftrans-[Mo(CNMe)2(PMe2Ph)4] andme-[W(CNMe)3(PMe2Ph)3] with sulphuric or hydrochloric acids in methanol or ethanol, or in methanol alone, under irradiation, gives methylamine, ammonia and hydrocarbons (mainly methane). The complex [W2(CNMe)4(μ-CNHMe)2(PMe2Ph)4]2+ cation has been obtained by the treatment ofmer-[W(CNMe)3(PMe2Ph3] with H2SO4 or [Et2OH][BF4] and gives methylamine, ammonia and methane on further acid treatment.