0000000000451528
AUTHOR
Stefan Ulrich
Synthesis, X-ray crystal structure, NMR characterization and theoretical calculations on [Cp2Ta(η2-H2)(CO)]+, the first thermally stable group 5 dihydrogen complex
Protonation of Cp2TaH(CO) (Cp = C5H5, 1a; C5H4But, 1b) by HBF4·Et2O at −78 °C in CH2Cl2 affords [Cp2TaH2(CO)]BF4 (2, 3) as mixtures of 2 isomers. The minor ones (2a, 2b) contain the known trans-dihydride [Cp2TaH2(CO)]+ cations whereas the major ones (3a, 3b) are [Cp2Ta(η2-H2)(CO)]BF4, the first group 5 dihydrogen complexes. The crystal structure of the analogous complex 3a·BArf4 recorded at 120 K confirms the presence of the coordinated dihydrogen ligand, which displays an H–H separation of 1.09(2) A in agreement with distances calculated from NMR data. Protonation of Cp2TaH2(SiMe2Ph) by (Et2O)2 ·HBArf4 does not lead to an analogous silane derivative but to the new dinuclear complex [(Cp2…
Blood flow velocity waveforms of the middle cerebral artery and abnormal neurological evaluations in live-born fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries.
Abstract We studied 37 fetuses with absent or reverse end-diastolic flow velocities (AREDFV) of the umbilical arteries with respect to the mode of delivery, fetal acidosis, resistance index of the middle cerebral arteries, and abnormal neurological evaluation at the time of discharge from the department of pediatrics. A control group with normal umbilical artery flow velocity waveforms was matched for gestational age. Fetuses with AREDFV were delivered almost exclusively by cesarean section, in most cases due to fetal distress. Metabolic changes with decreased base excess values were found more often in fetuses with AREDFV, but no difference could be detected with respect to severe fetal ac…
CK-BB as indicator of prenatal brain-cell injury in fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries
The purpose of this study is to determine the levels of brain type isoenzyme of creatine kinase (CK-BB) as a possible indicator of a pre-existing intrauterine brain-cell damage in cord blood sera of fetuses with preceding absent or reverse end-diastolic flow velocities of the umbilical arteries (AREDFV). CK-BB isoenzyme activities were determined in umbilical cord sera of 13 newborn infants with preceding AREDFV and in 14 fetuses with low end-diastolic flow velocities (LEDFV) of the umbilical arteries. 50 newborn infants with elective cesarean section and normal umbilical artery blood flow velocity waveforms were used as controls. Two-tailed Student's t-test and Fischer's exact test were us…