Thermodynamics of addition of H-2, CO, N-2, and C-H bonds to M((PPr3)-Pr-i)(2)Cl (M = Ir, Rh) : an unprecedented metal-carbonyl bond strength

The thermodynamics of interconversion of various complexes containing the unit IrL*Cl-2 (L* = P(Pr-i)(3)) have been investigated by calorimetry and equilibrium measurements. These complexes span a wide range of configurations including four- and five-coordinate d(8) (IrL*2ClL', IrL*Cl-2(CO)(2)) and five- and six-coordinate d(6) (IrL*2ClRH and IrL*2ClRH(CO)). On the basis of kinetic experiments, a lower limit to the Ir-Nz bond dissociation enthalpy (BDE) of IrL*Cl-2(N-2) has been determined (36 kcal/mol). Using this value as an "anchor", in conjunction with the relative addition enthalpies obtained calorimetrically, it is possible to derive lower limits for the absolute exothermicities of H-2 (48 kcal/mol) and CO (72 kcal/mol) addition to IrL*Cl-2; estimates can also be made for the addition of benzene and acetylene C-H bonds. These values are unusually high; indeed, the magnitude of the Ir-CO BDE is unprecedented. In addition, kinetic methods have been used to determine a lower limit of 29 kcal/mol to the Rh-N-2 BDE of RhL*Cl-2(N-2). Combined with previous calorimetric measurements on rhodium complexes, this value permits the calculation of lower limits to the absolute exothermicities of addition to RhL*Cl-2 for numerous small molecules including H-2, CO, N-2, C2H4, and aldehydic C-H bonds. The results of electronic structure calculations (approximate DFT; PMe3 used to model (PPr3)-Pr-i) are in excellent agreement with the relative experimental enthalpies, while the absolute values calculated for addition to IrL2Cl are significantly greater than the experimentally determined lower limits. Addition of a methane C-H bond is calculated to be significantly less favorable than addition of benzene or acetylene C-H bonds, in accord with the fact that IrL*Cl-2(alkyl)H complexes have not been reported. The significant differences in the enthalpies of addition for these three types of C-H bonds are briefly analyzed

Understanding Factors Associated With Psychomotor Subtypes of Delirium in Older Inpatients With Dementia

Objectives: Few studies have analyzed factors associated with delirium subtypes. In this study, we investigate factors associated with subtypes of delirium only in patients with dementia to provide insights on the possible prevention and treatments. Design: This is a cross-sectional study nested in the “Delirium Day” study, a nationwide Italian point-prevalence study. Setting and Participants: Older patients admitted to 205 acute and 92 rehabilitation hospital wards. Measures: Delirium was evaluated with the 4-AT and the motor subtypes with the Delirium Motor Subtype Scale. Dementia was defined by the presence of a documented diagnosis in the medical records and/or prescription of acetylcholinesterase inhibitors or memantine prior to admission. Results: Of the 1057 patients with dementia, 35% had delirium, with 25.6% hyperactive, 33.1% hypoactive, 34.5% mixed, and 6.7% nonmotor subtype. There were higher odds of having venous catheters in the hypoactive (OR 1.82, 95% CI 1.18-2.81) and mixed type of delirium (OR 2.23, CI 1.43-3.46), whereas higher odds of urinary catheters in the hypoactive (OR 2.91, CI 1.92-4.39), hyperactive (OR 1.99, CI 1.23-3.21), and mixed types of delirium (OR 2.05, CI 1.36-3.07). We found higher odds of antipsychotics both in the hyperactive (OR 2.87, CI 1.81-4.54) and mixed subtype (OR 1.84, CI 1.24-2.75), whereas higher odds of antibiotics was present only in the mixed subtype (OR 1.91, CI 1.26-2.87). Conclusions and Implications: In patients with dementia, the mixed delirium subtype is the most prevalent followed by the hypoactive, hyperactive, and nonmotor subtype. Motor subtypes of delirium may be triggered by clinical factors, including the use of venous and urinary catheters, and the use of antipsychotics. Future studies are necessary to provide further insights on the possible pathophysiology of delirium in patients with dementia and to address the optimization of the management of potential risk factors