MEASUREMENTS OF STRUCTURAL AND QUADRUPOLE COUPLING PARAMETERS FOR BROMOFERROCENE USING MICROWAVE SPECTROSCOPY

Rotational spectra for two isotopomers of bromoferrocene were measured using pulsed-beam Fourier transform microwave spectroscopy. Transitio ns were observed for the Br-79 and Br-81 isotopomers in the 5-9 GHz ra nge. Rotational constants and the quadrupole coupling tensors were obt ained from the data. The rotational constants and quadrupole coupling parameters for Br-79 are A=1272.110(1), B=516.1125(2), C=441.3775(2), eQq(aa)=267.16(3), eQq(ab)=-409.81(4), and eQq(bb)=21.49(4), and those for Br-81 are A=1271.045(4), B=510.0079(2), C=436.7687(2), eQq(aa)=22 5.40(6), eQq(ab)=-341.62(4), and eQq(bb)=15.65(4). The measured rotati onal constants were used to determine the following structural paramet ers of bromoferrocene: r(Fe-(C5H5))=1.63(2), r(Fe-(C5H4Br))=1.67(3), r (C-Br)=1.875(11), and r(C-C)=1.433(1) Angstrom. The values of the quad rupole coupling parameters in the principal quadrupole axis systems an d the C-Br bond axis systems are compared with similarly derived param eters for chloroferrocene, chlorobenzene, and bromobenzene. Previous d ata for chloroferrocene has been reanalyzed to obtain refined quadrupo le parameters. (C) 1997 American Institute of Physics. [S0021-9606(97) 03241-8].