Nature of the bonding in metal-silane σ-complexes

The nature of metal silane σ-bond interaction has been investigated in several key systems by a range of experimental and computational techniques. The structure of [Cp′Mn(CO)2(η2-HSiHPh2)] 1 has been determined by single crystal neutron diffraction, and the geometry at the Si atom is shown to approximate a trigonal bipyramid; salient bond distances and angles are Mn−H(1) 1.575(14), Si−H(1) 1.806(14), Si−H(2) 1.501(13) Å, and H(1)−Si−H(2) 148.5(8)°. This complex is similar to [Cp′Mn(CO)2(η2-HSiFPh2)] 2, whose structure and bonding characteristics have recently been determined by charge density studies based on high-resolution X-ray and neutron diffraction data. The geometry at the Si atom in these σ-bond complexes is compared with that in other systems containing hypercoordinate silicon. The Mn−H distances for 1 and 2 in solution have been estimated using NMR T1 relaxation measurements, giving a value of 1.56(3) Å in each case, in excellent agreement with the distances deduced from neutron diffraction. Density functional theory calculations have been employed to explore the bonding in the Mn−H−Si unit in 1 and 2 and in the related system [Cp′Mn(CO)2(η2-HSiCl3)] 3. These studies support the idea that the oxidative addition of a silane ligand to a transition metal center may be described as an asymmetric process in which the Mn−H bond is formed at an early stage, while both the establishment of the Mn−Si bond and also the activation of the η2-coordinated Si−H moiety are controlled by the extent of Mn → σ*(X−Si−H) back-donation, which increases with increasing electron-withdrawing character of the X substituent trans to the metal-coordinated Si−H bond. This delocalized molecular orbital (MO) approach is complemented and supported by combined experimental and theoretical charge density studies: the source function S(r,Ω), which provides a measure of the relative importance of each atom’s contribution to the density at a specific reference point r, clearly shows that all three atoms of the Mn(η2-SiH) moiety contribute to a very similar extent to the density at the Mn−Si bond critical point, in pleasing agreement with the MO model. Hence, we advance a consistent and unifying concept which accounts for the degree of Si−H activation in these silane σ-bond complexes

Communication and cross-examination in court for children and adults with intellectual disabilities: A systematic review

Courts in England, Wales and Northern Ireland have identified children and adults with intellectual disabilities (ID) as vulnerable witnesses. The call from the English Court of Appeal is for advocates to adjust questioning during cross-examination according to individual needs. This review systematically examined previous empirical studies with the aim of delineating the particular communication needs of children and adults with ID during cross-examination. Studies utilising experimental methodology similar to examination/cross-examination processes, or which assessed the communication of actual cross-examinations in court were included. A range of communication challenges were highlighted including: suggestibility to leading questions and negative feedback; acquiescence; accuracy; and understanding of court language. In addition, a number of influencing factors were identified, including: age; IQ level; question styles used; recall memory; and delays. This review highlights the need for further research using cross-examination methodology and live practice, that take into consideration the impact on communication of the unique environment and situation of the cross-examination process

Stakeholders’ perceptions of the benefit of introducing an Australian Intermediary System for vulnerable witnesses

Vulnerable witnesses (e.g. children and adults with communication impairment) face many barriers to testifying and achieving justice when participating in the criminal justice system. To date, reforms have been implemented in Australia to address these, yet the barriers remain. Several other countries have implemented an intermediary scheme, whereby an independent third party assists vulnerable witnesses to understand the questions and processes encountered during interviews and trials, and helps witnesses to be understood. This study provides a qualitative analysis of stakeholders’ (N¼25 professionals) perceptions regarding the potential benefits of implementing an intermediary scheme in Australia. While all participants demonstrated an open-minded attitude to new reform in this area, their perspectives did not support the introduction of an intermediary scheme at this time. Stakeholders highlighted the need for improved use and effectiveness of current measures, and expressed concern about adding further complication to the system

A study of the impact of the revised code for crown prosecutors

The revised Code for Crown Prosecutors became effective in June 1994. The authors were commissioned by the CPS in August 1995 to conduct a study of the impact of the revised Code upon case decisions, and specifically to discover whether the evidential and the public interest tests were being implemented in line with the guidance contained in the Code. It was found that prosecutors generally adopt a common approach, but this is attributable not so much to the clarifications contained in the Code as to the detailed guidance contained in the Explanatory Memorandum for CPS staff and in policy directives geared to specific offences. Prosecutors believe that the revised version of the Code is more easily understood by the police and public, but it would seem that the Code has been less successful in meeting its other avowed objectives of clarifying the evidential and the public interest tests so that these are interpreted consistently. The impact upon actual case decisions has been very limited

Rationing defence intermediaries under the April 2016 Criminal Practice Direction

Equality of arms for child and other vulnerable defendants, in particular access to the special measures routinely provided to prosecution witnesses with the same vulnerabilities, has been contentious since 1999. Much progress has been forced through rulings by courts concerned about such defendants’ capacity to cope with the demands of the adversarial trial. This progress appears to have been reversed by the April 2016 Criminal Practice Direction stating that the appointment of defendant intermediaries should be “rare” for the defendant’s testimony, and “extremely rare” for the entire trial. This article considers the legal options for challenging this retrograde step