[IrCl{N(CHCHPtBu2)2}]−: a versatile source of the IrI(PNP) pincer platform

The iridium(II) complex [IrCl{N(CHCHPtBu2)2}] is reduced by KC8 to give the anionic iridium(I) pincer complex [IrCl{N(CHCHPtBu2)2}]− which was isolated and fully characterized upon stabilization of the counter cation with crown ether as [K(15-cr-5)2][IrCl{N(CHCHPtBu2)2}]. This unprecedented anionic iridium(I) pincer complex completes the unusual, structurally characterized IrI/IrII/IrIII redox series [IrCl{N(CHCHPtBu2)2}]−/0/+, all in a square-planar coordination geometry, emphasizing the versatility of this PNP pincer ligand in stabilizing a broad range of oxidation states. The anionic chloro complex is a versatile source of the Ir(PNP) platform. Its reactivity was examined towards chloride ligand substitution against CO and N2, and oxidative addition of C-electrophiles, C–H bonds and dioxygen, allowing for the isolation of iridium(I) and iridium(III) (PNP) carbonyl, hydrocarbyl and peroxo complexes which were spectroscopically and crystallographically characterized

The role of salt and shear on the storage and assembly of spider silk proteins

Major ampullate silk fibers of orb web-weaving spiders have impressive mechanical properties due to the fact that the underlying proteins partially fold into helical/amorphous structures, yielding relatively elastic matrices that are toughened by anisotropic nanoparticulate inclusions (formed from stacks of beta-sheets of the same proteins). In vivo the transition from soluble protein to solid fibers involves a combination of chemical and mechanical stimuli (such as ion exchange, extraction of water and shear forces). Here we elucidate the effects of such stimuli on the in vitro aggregation of engineered and recombinantly produced major ampullate silk-like proteins (focusing on structure-function relationships with respect to their primary structures), and discuss their relevance to the storage and assembly of spider silk proteins in vivo. (C) 2009 Elsevier Inc. All rights reserved

Biomechanical comparison of two biplanar and one monoplanar reconstruction techniques of the acromioclavicular joint.

INTRODUCTION The purpose of this proof-of-concept study was to investigate the biomechanical performance of two surgical techniques, namely (1) the double Tight-Rope fixation with an additional acromioclavicular FiberTape fixation (DTRC) and (2) the fixation of the clavicle to the acromion and coracoid in a bipodal manner (Bipod) using a Poly-Tape and FiberTape. Both techniques intend to address vertical and horizontal instability after acromioclavicular dislocation. They were compared with the commonly used (3) double Tight-Rope (DTR) technique, which only stabilizes the clavicle to the coracoid. MATERIALS AND METHODS The acromioclavicular joint (ACJ) of 18 composite Sawbone shoulder specimens (6 per reconstruction group) were tested for posterosuperior elongation (70N cyclical load, 1500 cycles), load-to-failure and stiffness. RESULTS After 1500 cycles, the DTRC, Bipod and DTR group showed an elongation of 0.45 mm (SD 0.14 mm), 1.19 mm (SD 0.54 mm), and 0.46 mm (SD 0.15 mm), respectively. Although the elongation of the Bipod group was increased when compared to the other two groups (Bipod versus DTRC p = 0.008; Bipod versus DTR p = 0.006), the difference was less than 0.7 mm. The DTRC showed a higher load-to-failure of 656.1N (SD 58.1 N) compared to the Bipod [531.1 N (SD 108.2N) (p = 0.039)] and DTR group [522.8 N (SD 32.8 N) (p = 0.033)]. CONCLUSION The DTRC and the DTR group resulted in similar low elongation, while the elongation in the Bipod technique was slightly higher. Even though this difference of 0.7 mm shows statistical significance, it most likely has no clinical relevance. When testing in posterosuperior direction, which is the clinically relevant load vector, an additional fixation of the clavicle to the acromion did not reduce elongation in this study. It is, furthermore, questionable if the benefit of an increased load-to-failure in combination with no improvement in elongation and stiffness as seen in the DTRC group outweighs the possible risks and increased costs coming with the DTRC refixation

Synthesis and Reactivity of a Transient, Terminal Nitrido Complex of Rhodium

Irradiation of rhodium­(II) azido complex [Rh­(N₃)­{N­(CHCHP<i>t</i>Bu₂)₂}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium­(IV) nitride complex [Rh­(N)­{N­(CHCHP<i>t</i>Bu₂)₂}] is located in an antibonding Rh–N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen

Synthesis and Reactivity of a Transient, Terminal Nitrido Complex of Rhodium

Irradiation of rhodium­(II) azido complex [Rh­(N₃)­{N­(CHCHP<i>t</i>Bu₂)₂}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium­(IV) nitride complex [Rh­(N)­{N­(CHCHP<i>t</i>Bu₂)₂}] is located in an antibonding Rh–N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen

Synthesis and Reactivity of a Transient, Terminal Nitrido Complex of Rhodium

Irradiation of rhodium­(II) azido complex [Rh­(N₃)­{N­(CHCHP<i>t</i>Bu₂)₂}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium­(IV) nitride complex [Rh­(N)­{N­(CHCHP<i>t</i>Bu₂)₂}] is located in an antibonding Rh–N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen

Synthesis and Reactivity of a Transient, Terminal Nitrido Complex of Rhodium

Irradiation of rhodium(II) azido complex [Rh(N3){N(CHCHPtBu2)2}] allowed for the spectroscopic characterization of the first reported rhodium complex with a terminal nitrido ligand. DFT computations reveal that the unpaired electron of rhodium(IV) nitride complex [Rh(N){N(CHCHPtBu2)2}] is located in an antibonding Rh-N π* bond involving the nitrido moiety, thus resulting in predominant N-radical character, in turn providing a rationale for its transient nature and observed nitride coupling to dinitrogen