Photochemistry of some group 6A and 8 metal–metal bonded cyclopentadienylcarbonyl dimers in poly(vinyl chloride) films at 12–298 K

Cyclopentadienyl Complexes of Chromium, Molybdenum and Tungsten

“…5 1 5 5 2 By photolysing in a n i n e r t gas m a t r i x o r a PVC film a t 1 2 K , [M 2 (CO) 5 Cp 2 ] was shown to contain two t e r m i n a l C O ligands, two semibridging C O ligands, a n d one four-electron-donor bridging CO, whereas in the analogous complex with the linked C p ligand C 5 H 4 CH 2 C 5 H 4 , the pentacarbonyl species has t h r e e t e r m i n a l a n d two bridging CO ligands. 53 ' 54 Flash photolysis studies c o n f i r m e d these results a n d also detected t h e gauche r o t a m e r of [Mo 2 (CO) 6 Cp 2 ] . 5 6 Cp 2 ] to [M 2 (CO) 4 Cp 2 ], which was originally thought to proceed b y a r a d i c a l mechanism.…”

Terminal vs. bridging coordination of CO and NO ligands after decarbonylation of [W2Cp2(μ-PR2)(CO)3(NO)] complexes (R = Ph, Cy). An experimental and computational study

“…] was 1635 cm 1 (PVC film, 77 K), 22 and it was 1548 cm 1 for the structurally characterized diene complex 23 Previous work on  1 : 2 -CO-bridged dimanganese compounds has revealed that the 13 C NMR resonances for these ligands have chemical shifts comparable to those of terminal carbonyls. 10,24 This trend also seems to hold for tungsten compounds, because the carbonyl resonances for 3b were found at 226.1 and 207.6 ppm.…”

Excited States and Intermediates by Time-Resolved Infrared Spectroscopy

“…The compound has the structure: [3] CO Photolysis in the presence of 13CO (or PF3) leads to Cp*Cr(CO)( 13" CO)Cr(CO)2Cp* (or Cp*Cr(CO)(PF3)Cr(CO)2Cp*); probably for steric reasons there is no reaction with, e.g., PPh3 [4]. Photolysis of I in a low temperature matrix [5] shows loss of the terminal u(CO) bands and production of a single band in the bridging CO region, consistent with the formation of a triply bridged species Cp*Cr(#-CO)3CrCp*, with the CO groups possessing local D3h symmetry, hence leading to only one active u(CO) band, the e mode. Figure shows what happens in a room temperature TRIR experiment; it is clear that there is loss of terminal u(CO) bands assigned to parent and generation of an intermediate with two bands in the u(CO) bridging region.…”