SUBSTITUTED CYCLOPENTADIENYL COMPOUNDS .1. FORMYLATION OF METHYLCYCLOPENTADIENIDE AND THE SYNTHESIS AND NMR-STUDY OF SOME THALLIUM(I) AND RHODIUM(I) DERIVATIVES OF CYANOAMIDOCYCLOPENTADIENES, METHYLAMIDOCYCLOPENTADIENES, METHANOYLAMIDOCYCLOPENTADIENES AND DIMETHYLAMIDOCYCLOPENTADIENES

Reaction of potassium methylcyclopentadienide with methyl methanoate yields the salts of 1-methanoyl-2-methylcyclopentadiene and 1-methanoyl-3-methylcyclopentadiene in a molar ratio of 1.3:1.0. At ambient temperature each isomer comprises two conformers. The identity of and relation between the products were confirmed by 2-D H-1 NMR (COSY and NOESY). Thiele's acid (endo-tri-cyclo[5,2,1,0(2,6)]-4,8-dicarboxylic acid-deca-3,8-diene) was converted into the thallium(I) salts of the monomeric dimethylamide and nitrile. The bis(ethene)-rhodium(I) derivatives were prepared in high yield by reaction of the thallium salts with Cramer's compound {(C2H4)2RhCl}2. The alkene rotational barriers (DELTA-G#) are compared and NMR evidence for ring slippage is discussed. The mixed compound (CO)(C2H4)Rh(eta-5-C5H4CHO) shows the lowest reported alkene rotational barrier for any simple rhodium(I)-monocyclic Cp system.