INSERTION OF NH INTO THE RHENIUM CARBON BONDS OF A FISCHER-TYPE RHENACYCLOBUTADIENE - PREPARATION AND CHARACTERIZATION OF AZARHENACYCLIC COMPLEXES

The rhenacyclobutadiene complex (CO)4ReC(CH3)C(CO2CH3)C(OEt) (1) react s with 2,4-dinitrophenylhydrazine, tosylhydrazine or hydrazine hydroch loride to afford a new five-membered azarhenacyclic complex, (CO)4ReNH C(CH3)C(CO2CH3)C(OEt) (4), as a stable yellow solid. 4 was characteriz ed by elemental analysis, EI mass spectrometry and IR and H-1 and C-13 NMR spectroscopy, and its structure was elucidated by X-ray diffracti on techniques. The complex crystallizes in the triclinic system, space group P1BAR, with a = 8.721(1), b = 12.172(2), c = 15.013(2) angstrom , alpha = 86.42(1), beta = 88.83(1), gamma 79.48(1)-degrees, and four molecules per unit cell. The five-membered azarhenacycle is essentiall y planar, and the bond distances in the ring indicate strong electron delocalization, similar to that of the reported [1] analogous oxarhena cyclic complex (CO)4ReOC(CH3)C(CO2CH3)C(OEt) (2). Reaction between 1 a nd hydrazine monohydrate yields a mixture of 4 (minor product) and iso meric (CO)4ReC(CH3)C(CO2CH3)C(OEt)NH (major product, 5). The structure of 5 was assigned from spectroscopic evidence. 4 and 5 may be conside red as organometallic analogues of pyrrole, i.e. rhenapyrrole complexe s. Reaction of 4 with LDA followed by quenching with DCl in D2O at c. -78-degrees-C results in hydrogen-deuterium exchange at the nitrogen a tom.