THE MICROWAVE-SPECTRUM AND MOLECULAR-STRUCTURE FOR FE(NO)2(CO)2

Microwave spectra for five isotopomers of iron dinitrosyl dicarbonyl were measured in the 4-16-GHz range using a Flygare-Balle type spectrometer. Numerous b-dipole transitions were observed for Fe(NO)2(CO)2, (FeNONO(CO)2)-Fe-15,(Fe(NO)2(CO)2-Fe-15,(Fe(NO)2COCO)-Fe-15-C-13, and (Fe(NO)2(CO)2)-Fe-54-N-15. Measured rotational constants were analyzed to obtain an accurate gas-phase structure. Some of the structural parameters obtained are angleN-Fe-N = 121(2)-degrees, angleC-Fe-C = 101(2)-degrees, r(Fe-N) = 1.69(2) angstrom, r(Fe-C) = 1.85(2) angstrom, angleFe-N-O = 176(2)-degrees, and angleFe-C-O = 177(2)-degrees. NMR and IR data are also given. Nitrogen quadrupole coupling tensors were obtained from hyperfine structure on transitions for (Fe(NO)2(CO)2)-N-14 and (Fe(NO)(NO)(CO)2)-N-14-N-15. The z principal axis for the quadrupole tensor is rotated 62-degrees away from the Fe-N bond direction and principal axis components are eQq(zz) = -1.5 MHz, eQq(xx) = 1.0 MHz and eQq(yy) = 0.53 MHz.