DETERMINATION OF STRUCTURAL PARAMETERS FOR THE HALF-SANDWICH COMPOUNDS CYCLOPENTADIENYL THALLIUM AND CYCLOPENTADIENYL INDIUM AND INDIUM QUADRUPOLE COUPLING FOR CYCLOPENTADIENYL INDIUM USING MICROWAVE SPECTROSCOPY

Microwave rotational transitions for J'<--J=2<--1 and 3<--2 were measu red in the 7-11 GHz range for three isotopomers of (C5H5)In. Similar t ransitions (up to J'<--J=5<--4) for eight isotopomers of (C5H5)Tl were measured in the 5-15 GHz range. The rotational constants of the most abundant isotopomers are B(Cp Tl-203)=1467.9730(11) MHz, B((CpTl)-Tl-2 05)=1465.0723(14) MHz, B((CpIn)-In-113)=1809,9785(30) MHz, and B((CpIn )-In-115)=1800.8199(18) MHz (Cp=C5H5). The quadrupole coupling strengt hs for the indium compounds are eQq((CpIn)-In-113)=118.397(69) MHz and eQq((CpIn)-In-115)=-119.981(31) MHz. Spectra for single-substitution C-13 isotopomers were seen in natural abundance. Deuterated samples of CpTl were prepared to obtain spectra for deuterium-substituted isotop omers. Analysis of the spectra allowed the determination of the follow ing structural parameters; for (C5H5)Tl, r(Tl-C-5,)=2.413(3) Angstrom, r(C-C)=1.421(10) Angstrom, r(C-H)=1.082(9) Angstrom and angle C-5-H=0 .9(2)degrees (C-5, represents the planar, 5-carbon ring of C5H5) and f or (C5H5,)In, r(In-C-5)=2.314(4) Angstrom and r(C-C)=1.426(6) Angstrom . A Kraitchman analysis was performed on the available isotopomers for comparison of r(0) and r(s), values. Both structural analyses indicat e that the hydrogen atoms in (C5H5)Tl are bent slightly out of the car bon plane away from the coordinated metal atom. (C) 1997 American Inst itute of Physics.