Exchanging conformations of a hydroformylation catalyst structurally characterized using two-dimensional vibrational spectroscopy.

Catalytic transition-metal complexes often occur in several conformations that exchange rapidly (

Ultrafast dynamics in iron tetracarbonyl olefin complexes investigated with two-dimensional vibrational spectroscopy.

The dynamics of iron tetracarbonyl olefin complexes has been investigated using two-dimensional infrared (2D-IR) spectroscopy. Cross peaks between all CO-stretching bands show that the CO-stretch modes are coupled, and from the cross-peak anisotropies we can confirm previous assignments of the absorption bands. From the pump-probe delay dependence of the diagonal peaks in the 2D-IR spectrum we obtain a correlation time of ∼3 ps for the spectral fluctuations of the CO-stretch modes. We observe a multi-exponential pump-probe delay dependence of the cross-peak intensities, with rate constants ranging from 0.1 ps(-1) to 0.6 ps(-1). To determine whether this delay dependence originates from fluxionality of the complex or from intramolecular vibrational relaxation (IVR), we modulate the free-energy barrier of fluxional rearrangement by varying the pi-backbonding capacities of the olefin ligand in two iron tetracarbonyl olefin complexes: Fe(CO)(4)(cinnamic acid) and Fe(CO)(4)(dimethyl fumarate). Since the pi-backbonding strongly influences the rate of fluxionality, comparing the dynamics in the two complexes allows us to determine to what extent the observed dynamics is caused by fluxionality. We conclude that on the time scale of our experiments (up to 100 ps) the cross-peak dynamics in the iron complexes is determined by intramolecular vibrational energy relaxation. Hence, in contrast to previously investigated irontricarbonyl and ironpentacarbonyl complexes, iron tetracarbonyl olefin complexes exhibit no fluxionality on the picosecond time scale.

Ventricular reservoir punctures performed by nurses: an improvement in quality of care.

Management strategies in the treatment of infants with posthemorrhagic ventricular dilation include the placement of a ventricular reservoir. Traditionally, ventricular punctures of these reservoirs have been performed only by physicians. In the pilot project described in this article, we taught nursing staff to perform punctures of a cerebral ventricular reservoir in neonates with hydrocephalus to give nurses more control in their daily care of these infants.All consecutive punctures performed between August 2006 and March 2007 (n = 302) were studied. The chart was reviewed for the infant's state during the puncture, the caregiver who performed the puncture, and the timeliness of the puncture with respect to schedule and to infant state. During the day shift, there was no significant difference in timeliness, whether the puncture was performed by a physician, a nurse, a physician assistant (PA), or a nurse under the supervision of a physician. On the night shift, punctures were performed on schedule significantly more often when they were carried out by nurses (p>.001). This pilot project demonstrated that nurses can learn to perform cerebrospinal fluid removal from a ventricular reservoir. Because it increased the timeliness with which punctures were performed and gave nurses more control in planning rest periods for these infants, this policy change was judged a success.