Probing the presence of multiple metal-metal bonds in technetium chlorides by X-ray absorption spectroscopy: implications for synthetic chemistry.
The cesium salts of [Tc(2)X(8)](3-) (X = Cl, Br), the reduction product of (n-Bu(4)N)[TcOCl(4)] with (n-Bu(4)N)BH(4) in THF, and the product obtained from  reaction of Tc(2)(O(2)CCH(3))(4)Cl(2) with HCl(g) at 300 °C have been characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. For the [Tc(2)X(8)](3-) anions, the Tc-Tc separations found by EXAFS spectroscopy (2.12(2) Å for both X = Cl and Br) are in excellent agreement with those found by single-crystal X-ray diffraction (SCXRD) measurements (2.117[4] Å for X = Cl and 2.1265(1) Å for X = Br). The Tc-Tc separation found by EXAFS in these anions is slightly shorter than those found in the [Tc(2)X(8)](2-) anions (2.16(2) Å for X = Cl and Br). Spectroscopic and SCXRD characterization of the reduction product of (n-Bu(4)N)[TcOCl(4)] with (n-Bu(4)N)BH(4) are consistent with the presence of dinuclear species that are related to the [Tc(2)Cl(8)](n-) (n = 2, 3) anions. From these results, a new preparation of (n-Bu(4)N)(2)[Tc(2)Cl(8)] was developed. Finally,  EXAFS characterization of the product obtained from  reaction of Tc(2)(O(2)CCH(3))(4)Cl(2) with HCl(g) at 300 °C indicates the presence of amorphous α-TcCl(3). The Tc-Tc separation (i.e., 2.46(2) Å) measured in this compound is consistent with the presence of Tc═Tc double bonds in the [Tc(3)](9+) core.
Department of Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154, United States. poineauf@unlv.nevada.edu
Frederic
F
Poineau
Erik V
EV
Johnstone
Paul M
PM
Forster
Longzou
L
Ma
Alfred P
AP
Sattelberger
Kenneth R
KR
Czerwinski
D002586:Cesium / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic; D002712:Chlorides / Q000138:chemical synthesis* / Q000737:chemistry*; D005663:Furans / Q000737:chemistry; D006851:Hydrochloric Acid / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D013667:Technetium / Q000737:chemistry*; D013696:Temperature; D056928:X-Ray Absorption Spectroscopy
D002712:Chlorides; D005663:Furans; D002586:Cesium; C018674:tetrahydrofuran; D013667:Technetium; D006851:Hydrochloric Acid