New Pyridine Dicarbene Pincer Ligands with Ring Expanded NHCs and their Nickel and Chromium Complexes.

The pincer complexes [NiBr(CNC)]Br (4), [CrBr(CNC)] (5 a) and [CrBrCl(CNC)] (5 b), where CNC=3,3'-(pyridine-2,6-diyl)bis(1-mesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene), were obtained from the novel ligand CNC, generated in situ from the precursor (CHNCH)Br and [NiBr(PPh)] or from [Cr{N(SiMe)}(THF)] and (CHNCH)Br by aminolysis, respectively. The tetrahedrally distorted square planar (τ≅0.30) geometry and the singlet ground state of Ni in 4 were attributed to steric constraints of the CNC backbone.

The Accuracy of Nonstandardized MELD/PELD Score Exceptions in the Pediatric Liver Allocation System.

Background: In the United States, over half of pediatric candidates receive exceptions and status upgrades that increase their allocation model of end-stage liver disease/pediatric end-stage liver disease (MELD/PELD) score above their laboratory MELD/PELD score. We determined whether these "nonstandardized" MELD/PELD exceptions accurately depict true pretransplant mortality risk.

Methods: Using data from the Scientific Registry of Transplant Recipients, we identified pediatric candidates (<18 y of age) with chronic liver failure added to the waitlist between June 2016 and September 2021 and estimated all-cause pretransplant mortality with mixed-effects Cox proportional hazards models that treated allocation MELD/PELD and exception status as time-dependent covariates.

The Accuracy of Initial U.S. Heart Transplant Candidate Rankings.

Background: The U.S. heart allocation system ranks candidates with only 6 treatment-based categorical "statuses" and ignores many objective patient characteristics.

A cavity-shaped -chelating P,N ligand for highly selective nickel-catalysed ethylene dimerisation.

The presence of a permethylated α-cyclodextrin (α-CD) cavity in a chelating P,N ligand promotes exclusive formation of 1 : 1 ligand/metal complexes. In MX complexes, one of the two halido ligands is forced to reside inside the CD hollow while the second one is pointing outside. Unlike its cavity-free analogue, a Ni(II) complex of the CD ligand is a highly selective precatalyst for ethylene dimerisation (96% C selectivity with up to 95% of 1-butene within the C fraction).