Introducing the North American Association of Practicum Sites in Neuropsychology (NAPSN): development of a new organization devoted to facilitating high quality practicum training.

Introduction: In February 2023, a work group began to develop a new North American organization in neuropsychology to represent and support practicum-training sites. While other training-focused organizations such as the Association of Postdoctoral Programs in Clinical Neuropsychology (APPCN) and the Association of Internship Training in Clinical Neuropsychology (AITCN) have existed for many years, no organization exists to promote and support practicum level training outside of doctoral degree programs. The work group developed such an organization, subsequently named the North American Association of Practicum Sites in Neuropsychology (NAPSN), beginning with a mission statement and general purpose of the organization. Methods: The work group divided members into five task forces focused on various tasks needed to start the organization, including Mission/Vision, Administrative Structure, Membership, Financials, and Bylaws. The entire work group met monthly with additional meetings and work via email for the various task forces, which resulted in the development of a mission statement and bylaws, as well as a framework for program administration, membership requirements and financial needs. Conclusions: The group developed NAPSN primarily as a resource to support diverse practicum programs in urban, suburban, and rural areas in the US and Canada to provide optimal graduate level clinical training in neuropsychology. Didactics aimed specifically at practicum students was one need identified early in the process. NAPSN is developing a website-based resource in collaboration with other training organizations to increase the didactic offerings to practicum students. Other initiatives and collaborative efforts will be undertaken over time as circumstances warrant.

Allosteric modulation of GluN1/GluN3 NMDA receptors by GluN1-selective competitive antagonists.

NMDA-type ionotropic glutamate receptors are critical for normal brain function and are implicated in central nervous system disorders. Structure and function of NMDA receptors composed of GluN1 and GluN3 subunits are less understood compared to those composed of GluN1 and GluN2 subunits. GluN1/3 receptors display unusual activation properties in which binding of glycine to GluN1 elicits strong desensitization, while glycine binding to GluN3 alone is sufficient for activation. Here, we explore mechanisms by which GluN1-selective competitive antagonists, CGP-78608 and L-689,560, potentiate GluN1/3A and GluN1/3B receptors by preventing glycine binding to GluN1. We show that both CGP-78608 and L-689,560 prevent desensitization of GluN1/3 receptors, but CGP-78608-bound receptors display higher glycine potency and efficacy at GluN3 subunits compared to L-689,560-bound receptors. Furthermore, we demonstrate that L-689,560 is a potent antagonist of GluN1FA+TL/3A receptors, which are mutated to abolish glycine binding to GluN1, and that this inhibition is mediated by a non-competitive mechanism involving binding to the mutated GluN1 agonist binding domain (ABD) to negatively modulate glycine potency at GluN3A. Molecular dynamics simulations reveal that CGP-78608 and L-689,560 binding or mutations in the GluN1 glycine binding site promote distinct conformations of the GluN1 ABD, suggesting that the GluN1 ABD conformation influences agonist potency and efficacy at GluN3 subunits. These results uncover the mechanism that enables activation of native GluN1/3A receptors by application of glycine in the presence of CGP-78608, but not L-689,560, and demonstrate strong intra-subunit allosteric interactions in GluN1/3 receptors that may be relevant to neuronal signaling in brain function and disease.

Cortical imbalance following delayed restoration of bilateral hearing in deaf adolescents.

Unilateral auditory deprivation in early childhood can lead to cortical strengthening of inputs from the stimulated side, yet the impact of this on bilateral processing when inputs are later restored beyond an early sensitive period is unknown. To address this, we conducted a longitudinal study with 13 bilaterally profoundly deaf adolescents who received unilateral access to sound via a cochlear implant (CI) in their right ear in early childhood before receiving bilateral access to sound a decade later via a second CI in their left ear. Auditory-evoked cortical responses to unilateral and bilateral stimulation were measured repeatedly using electroencephalogram from 1 week to 14 months after activation of their second CI. Early cortical responses from the newly implanted ear and bilateral stimulation were atypically lateralized to the left ipsilateral auditory cortex. Duration of unilateral deafness predicted an unexpectedly stronger representation of inputs from the newly implanted, compared to the first implanted ear, in left auditory cortex. Significant initial reductions in responses were observed, yet a left-hemisphere bias and unequal weighting of inputs favoring the long-term deaf ear did not converge to a balanced state observed in the binaurally developed system. Bilateral response enhancement was significantly reduced in left auditory cortex suggesting deficits in ipsilateral response inhibition of new, dominant, inputs during bilateral processing. These findings paradoxically demonstrate the adaptive capacity of the adolescent auditory system beyond an early sensitive period for bilateral input, as well as restrictions on its potential to fully reverse cortical imbalances driven by long-term unilateral deafness.

Investigating Cortical Responses to Noise-Vocoded Speech in Children with Normal Hearing Using Functional Near-Infrared Spectroscopy (fNIRS).

Whilst functional neuroimaging has been used to investigate cortical processing of degraded speech in adults, much less is known about how these signals are processed in children. An enhanced understanding of cortical correlates of poor speech perception in children would be highly valuable to oral communication applications, including hearing devices. We utilised vocoded speech stimuli to investigate brain responses to degraded speech in 29 normally hearing children aged 6-12 years. Intelligibility of the speech stimuli was altered in two ways by (i) reducing the number of spectral channels and (ii) reducing the amplitude modulation depth of the signal. A total of five different noise-vocoded conditions (with zero, partial or high intelligibility) were presented in an event-related format whilst participants underwent functional near-infrared spectroscopy (fNIRS) neuroimaging. Participants completed a word recognition task during imaging, as well as a separate behavioural speech perception assessment. fNIRS recordings revealed statistically significant sensitivity to stimulus intelligibility across several brain regions. More intelligible stimuli elicited stronger responses in temporal regions, predominantly within the left hemisphere, while right inferior parietal regions showed an opposite, negative relationship. Although there was some evidence that partially intelligible stimuli elicited the strongest responses in the left inferior frontal cortex, a region previous studies have suggested is associated with effortful listening in adults, this effect did not reach statistical significance. These results further our understanding of cortical mechanisms underlying successful speech perception in children. Furthermore, fNIRS holds promise as a clinical technique to help assess speech intelligibility in paediatric populations.

Gasification biochar from horticultural waste: An exemplar of the circular economy in Singapore.

Organic waste, the predominant component of global solid waste, has never been higher, resulting in increased landfilling, incineration, and open dumping that releases greenhouse gases and toxins that contribute to global warming and environmental pollution. The need to create and adopt sustainable closed-loop systems for waste reduction and valorization is critical. Using organic waste as a feedstock, gasification and pyrolysis systems can produce biooil, syngas, and thermal energy, while reducing waste mass by as much as 85-95% through conversion into biochar, a valuable byproduct with myriad uses from soil conditioning to bioremediation and carbon sequestration. Here, we present a novel case study detailing the circular economy of gasification biochar in Singapore's Gardens by the Bay. Biochar produced from horticultural waste within the Gardens was tested as a partial peat moss substitute in growing lettuce, pak choi, and pansy, and found to be a viable substitute for peat moss. At low percentages of 20-30% gasification biochar, fresh weight yields for lettuce and pak choi were comparable to or exceeded those of plants grown in pure peat moss. The biochar was also analyzed as a potential additive to concrete, with a 2% biochar mortar compound found to be of suitable strength for non-structural functions, such as sidewalks, ditches, and other civil applications. These results demonstrate the global potential of circular economies based on local biochar creation and on-site use through the valorization of horticultural waste via gasification, generating clean, renewable heat or electricity, and producing a carbon-neutral to -negative byproduct in the form of biochar. They also indicate the potential of scaled-up pyrolysis or gasification systems for a circular economy in waste management.

How to One Up a Pandemic: University of Minnesota's Physical Medicine and Rehabilitation Virtual Clerkship-A Model for Alternative Clinical Training and Preliminary Validation Study.

ABSTRACT: Drastic and rapid changes to medical education are uncommon because of regulations and restrictions designed to ensure consistency among medical school curriculums and to safeguard student well-being. As a consequence of the COVID-19 pandemic, medical education had to break away from its conventions and transition from time-honored teaching methods to innovative solutions. This article explores the anticipated and actual efficacy of the swift conversion of a specialty elective from a traditional in-person format to a fully virtual clerkship. In addition, it includes a noninferiority study to determine where a virtual classroom may excel or fall short in comparison with conventional clinical rotations.

The Benefit of Cross-Modal Reorganization on Speech Perception in Pediatric Cochlear Implant Recipients Revealed Using Functional Near-Infrared Spectroscopy.

Cochlear implants (CIs) are the most successful treatment for severe-to-profound deafness in children. However, speech outcomes with a CI often lag behind those of normally-hearing children. Some authors have attributed these deficits to the takeover of the auditory temporal cortex by vision following deafness, which has prompted some clinicians to discourage the rehabilitation of pediatric CI recipients using visual speech. We studied this cross-modal activity in the temporal cortex, along with responses to auditory speech and non-speech stimuli, in experienced CI users and normally-hearing controls of school-age, using functional near-infrared spectroscopy. Strikingly, CI users displayed significantly greater cortical responses to visual speech, compared with controls. Importantly, in the same regions, the processing of auditory speech, compared with non-speech stimuli, did not significantly differ between the groups. This suggests that visual and auditory speech are processed synergistically in the temporal cortex of children with CIs, and they should be encouraged, rather than discouraged, to use visual speech.

Evaluating time-reversed speech and signal-correlated noise as auditory baselines for isolating speech-specific processing using fNIRS.

Evidence using well-established imaging techniques, such as functional magnetic resonance imaging and electrocorticography, suggest that speech-specific cortical responses can be functionally localised by contrasting speech responses with an auditory baseline stimulus, such as time-reversed (TR) speech or signal-correlated noise (SCN). Furthermore, these studies suggest that SCN is a more effective baseline than TR speech. Functional near-infrared spectroscopy (fNIRS) is a relatively novel, optically-based imaging technique with features that make it ideal for investigating speech and language function in paediatric populations. However, it is not known which baseline is best at isolating speech activation when imaging using fNIRS. We presented normal speech, TR speech and SCN in an event-related format to 25 normally-hearing children aged 6-12 years. Brain activity was measured across frontal and temporal brain areas in both cerebral hemispheres whilst children passively listened to the auditory stimuli. In all three conditions, significant activation was observed bilaterally in channels targeting superior temporal regions when stimuli were contrasted against silence. Unlike previous findings in infants, we found no significant activation in the region of interest over superior temporal cortex in school-age children when normal speech was contrasted against either TR speech or SCN. Although no statistically significant lateralisation effects were observed in the region of interest, a left-sided channel targeting posterior temporal regions showed significant activity in response to normal speech only, and was investigated further. Significantly greater activation was observed in this left posterior channel compared to the corresponding channel on the right side under the normal speech vs SCN contrast only. Our findings suggest that neither TR speech nor SCN are suitable auditory baselines for functionally isolating speech-specific processing in an experimental set up involving fNIRS with 6-12 year old children.

Pre-operative Brain Imaging Using Functional Near-Infrared Spectroscopy Helps Predict Cochlear Implant Outcome in Deaf Adults.

Currently, it is not possible to accurately predict how well a deaf individual will be able to understand speech when hearing is (re)introduced via a cochlear implant. Differences in brain organisation following deafness are thought to contribute to variability in speech understanding with a cochlear implant and may offer unique insights that could help to more reliably predict outcomes. An emerging optical neuroimaging technique, functional near-infrared spectroscopy (fNIRS), was used to determine whether a pre-operative measure of brain activation could explain variability in cochlear implant (CI) outcomes and offer additional prognostic value above that provided by known clinical characteristics. Cross-modal activation to visual speech was measured in bilateral superior temporal cortex of pre- and post-lingually deaf adults before cochlear implantation. Behavioural measures of auditory speech understanding were obtained in the same individuals following 6 months of cochlear implant use. The results showed that stronger pre-operative cross-modal activation of auditory brain regions by visual speech was predictive of poorer auditory speech understanding after implantation. Further investigation suggested that this relationship may have been driven primarily by the inclusion of, and group differences between, pre- and post-lingually deaf individuals. Nonetheless, pre-operative cortical imaging provided additional prognostic value above that of influential clinical characteristics, including the age-at-onset and duration of auditory deprivation, suggesting that objectively assessing the physiological status of the brain using fNIRS imaging pre-operatively may support more accurate prediction of individual CI outcomes. Whilst activation of auditory brain regions by visual speech prior to implantation was related to the CI user's clinical history of deafness, activation to visual speech did not relate to the future ability of these brain regions to respond to auditory speech stimulation with a CI. Greater pre-operative activation of left superior temporal cortex by visual speech was associated with enhanced speechreading abilities, suggesting that visual speech processing may help to maintain left temporal lobe specialisation for language processing during periods of profound deafness.

Distribution of FMRFamide-related peptides and co-localization with glutamate in Cupiennius salei, an invertebrate model system.

FMRFamide-related proteins have been described in both vertebrate and invertebrate nervous systems and have been suggested to play important roles in a variety of physiological processes. One proposed function is the modulation of signal transduction in mechanosensory neurons and their associated behavioral pathways in the Central American wandering spider Cupiennius salei; however, little is known about the distribution and abundance of FMRFamide-related proteins (FaRPs) within this invertebrate system. We employ immunohistochemistry, Hoechst nuclear stain and confocal microscopy of serial sections to detect, characterize and quantify FMRFamide-like immunoreactive neurons throughout all ganglia of the spider brain and along leg muscle. Within the different ganglia, between 3.4 and 12.6% of neurons showed immunolabeling. Among the immunoreactive cells, weakly and strongly labeled neurons could be distinguished. Between 71.4 and 81.7% of labeled neurons showed weak labeling, with 18.3 to 28.6% displaying strong labeling intensity. Among the weakly labeled neurons were characteristic motor neurons that have previously been shown to express ɣ-aminobutyric acid or glutamate. Ultrastructural investigations of neuromuscular junctions revealed mixed presynaptic vesicle populations including large electron-dense vesicles characteristic of neuropeptides. Double labeling for glutamate and FaRPs indicated that a subpopulation of neurons may co-express both neuroactive compounds. Our findings suggest that FaRPs are expressed throughout all ganglia and that different neurons have different expression levels. We conclude that FaRPs are likely utilized as neuromodulators in roughly 8% of neurons in the spider nervous system and that the main transmitter in a subpopulation of these neurons is likely glutamate.

Cortical correlates of speech intelligibility measured using functional near-infrared spectroscopy (fNIRS).

Functional neuroimaging has identified that the temporal, frontal and parietal cortex support core aspects of speech processing. An objective measure of speech intelligibility based on cortical activation in these brain regions would be extremely useful to speech communication and hearing device applications. In the current study, we used noise-vocoded speech to examine cortical correlates of speech intelligibility in normally-hearing listeners using functional near-infrared spectroscopy (fNIRS), a non-invasive, neuroimaging technique that is fully-compatible with hearing devices, including cochlear implants. In twenty-three normally-hearing adults we measured (1) activation in superior temporal, inferior frontal and inferior parietal cortex bilaterally and (2) behavioural speech intelligibility. Listeners heard noise-vocoded sentences targeting five equally spaced levels of intelligibility between 0 and 100% correct. Activation in superior temporal regions increased linearly with intelligibility. This relationship appears to have been driven in part by changing acoustic properties across stimulation conditions, rather than solely by intelligibility per se. Superior temporal activation was also predictive of individual differences in intelligibility in a challenging listening condition. Beyond superior temporal cortex, we identified regions in which activation varied non-linearly with intelligibility. For example, in left inferior frontal cortex, activation peaked in response to heavily degraded, yet still somewhat intelligible, speech. Activation in this region was linearly related to response time on a simultaneous behavioural task, suggesting it may contribute to decision making. Our results indicate that fNIRS has the potential to provide an objective measure of speech intelligibility in normally-hearing listeners. Should these results be found to apply similarly in the case of individuals listening through a cochlear implant, fNIRS would demonstrate potential for a clinically useful measure not only of speech intelligibility, but also of listening effort.

Adaptive benefit of cross-modal plasticity following cochlear implantation in deaf adults.

It has been suggested that visual language is maladaptive for hearing restoration with a cochlear implant (CI) due to cross-modal recruitment of auditory brain regions. Rehabilitative guidelines therefore discourage the use of visual language. However, neuroscientific understanding of cross-modal plasticity following cochlear implantation has been restricted due to incompatibility between established neuroimaging techniques and the surgically implanted electronic and magnetic components of the CI. As a solution to this problem, here we used functional near-infrared spectroscopy (fNIRS), a noninvasive optical neuroimaging method that is fully compatible with a CI and safe for repeated testing. The aim of this study was to examine cross-modal activation of auditory brain regions by visual speech from before to after implantation and its relation to CI success. Using fNIRS, we examined activation of superior temporal cortex to visual speech in the same profoundly deaf adults both before and 6 mo after implantation. Patients' ability to understand auditory speech with their CI was also measured following 6 mo of CI use. Contrary to existing theory, the results demonstrate that increased cross-modal activation of auditory brain regions by visual speech from before to after implantation is associated with better speech understanding with a CI. Furthermore, activation of auditory cortex by visual and auditory speech developed in synchrony after implantation. Together these findings suggest that cross-modal plasticity by visual speech does not exert previously assumed maladaptive effects on CI success, but instead provides adaptive benefits to the restoration of hearing after implantation through an audiovisual mechanism.

The distribution of cholinergic neurons and their co-localization with FMRFamide, in central and peripheral neurons of the spider Cupiennius salei.

The spider Cupiennius salei is a well-established model for investigating information processing in arthropod sensory systems. Immunohistochemistry has shown that several neurotransmitters exist in the C. salei nervous system, including GABA, glutamate, histamine, octopamine and FMRFamide, while electrophysiology has found functional roles for some of these transmitters. There is also evidence that acetylcholine (ACh) is present in some C. salei neurons but information about the distribution of cholinergic neurons in spider nervous systems is limited. Here, we identify C. salei genes that encode enzymes essential for cholinergic transmission: choline ACh transferase (ChAT) and vesicular ACh transporter (VAChT). We used in-situ hybridization with an mRNA probe for C. salei ChAT gene to locate somata of cholinergic neurons in the central nervous system and immunohistochemistry with antisera against ChAT and VAChT to locate these proteins in cholinergic neurons. All three markers labeled similar, mostly small neurons, plus a few mid-sized neurons, in most ganglia. In the subesophageal ganglia, labeled neurons are putative efferent, motor or interneurons but the largest motor and interneurons were unlabeled. Groups of anti-ChAT labeled small neurons also connect the optic neuropils in the spider protocerebrum. Differences in individual cell labeling intensities were common, suggesting a range of ACh expression levels. Double-labeling found a subpopulation of anti-VAChT-labeled central and mechanosensory neurons that were also immunoreactive to antiserum against FMRFamide-like peptides. Our findings suggest that ACh is an important neurotransmitter in the C. salei central and peripheral nervous systems.

Plasticity in bilateral superior temporal cortex: Effects of deafness and cochlear implantation on auditory and visual speech processing.

While many individuals can benefit substantially from cochlear implantation, the ability to perceive and understand auditory speech with a cochlear implant (CI) remains highly variable amongst adult recipients. Importantly, auditory performance with a CI cannot be reliably predicted based solely on routinely obtained information regarding clinical characteristics of the CI candidate. This review argues that central factors, notably cortical function and plasticity, should also be considered as important contributors to the observed individual variability in CI outcome. Superior temporal cortex (STC), including auditory association areas, plays a crucial role in the processing of auditory and visual speech information. The current review considers evidence of cortical plasticity within bilateral STC, and how these effects may explain variability in CI outcome. Furthermore, evidence of audio-visual interactions in temporal and occipital cortices is examined, and relation to CI outcome is discussed. To date, longitudinal examination of changes in cortical function and plasticity over the period of rehabilitation with a CI has been restricted by methodological challenges. The application of functional near-infrared spectroscopy (fNIRS) in studying cortical function in CI users is becoming increasingly recognised as a potential solution to these problems. Here we suggest that fNIRS offers a powerful neuroimaging tool to elucidate the relationship between audio-visual interactions, cortical plasticity during deafness and following cochlear implantation, and individual variability in auditory performance with a CI.

Speech-evoked activation in adult temporal cortex measured using functional near-infrared spectroscopy (fNIRS): Are the measurements reliable?

Functional near-infrared spectroscopy (fNIRS) is a silent, non-invasive neuroimaging technique that is potentially well suited to auditory research. However, the reliability of auditory-evoked activation measured using fNIRS is largely unknown. The present study investigated the test-retest reliability of speech-evoked fNIRS responses in normally-hearing adults. Seventeen participants underwent fNIRS imaging in two sessions separated by three months. In a block design, participants were presented with auditory speech, visual speech (silent speechreading), and audiovisual speech conditions. Optode arrays were placed bilaterally over the temporal lobes, targeting auditory brain regions. A range of established metrics was used to quantify the reproducibility of cortical activation patterns, as well as the amplitude and time course of the haemodynamic response within predefined regions of interest. The use of a signal processing algorithm designed to reduce the influence of systemic physiological signals was found to be crucial to achieving reliable detection of significant activation at the group level. For auditory speech (with or without visual cues), reliability was good to excellent at the group level, but highly variable among individuals. Temporal-lobe activation in response to visual speech was less reliable, especially in the right hemisphere. Consistent with previous reports, fNIRS reliability was improved by averaging across a small number of channels overlying a cortical region of interest. Overall, the present results confirm that fNIRS can measure speech-evoked auditory responses in adults that are highly reliable at the group level, and indicate that signal processing to reduce physiological noise may substantially improve the reliability of fNIRS measurements.

Synthesis of non-symmetrically sulphonated phosphine sulphonate based Pd(II) catalyst salts for olefin polymerisation reactions.

Direct sulphonation of 2-(diphenylphosphino)benzenesulphonic acid was extensively studied. The non-symmetrically functionalised reaction products obtained, related to the widely applied water soluble phosphine ligands m,m,m-TPPTS and m,m-TPPDS, display chelating κ(2)-(P,O)-coordination to Pd(II) metal centres. Phase transfer reaction of rac-o,m-TPPDS as the potassium salt with 18-crown-6 and complexation to Pd(II) gives the novel anionic catalyst precursor [K(18-crown-6)](2)[κ(2)(P,O){rac-o,m-TPPDS}PdMeCl] suitable for olefin polymerisation reactions. Ethene homo- and co-polymerisation reactions with polar functionalised olefins were investigated with this anionic phosphine sulphonate Pd(II)-based pre-catalyst salt.

The calcium-modulated structures of calmodulin and S100b proteins are useful to monitor hydrogen/deuterium exchange efficiency using matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Hydrogen/deuterium exchange (HDX) using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) is a sensitive, salt-tolerant and high-throughput method useful to probe protein conformation and molecular interactions. However, a drawback of the MALDI HDX technique is that sample preparation methods can typically result in higher levels of artificial deuterium in-exchange and/or hydrogen back- exchange just prior to or during mass analysis; this may impair data reproducibility and impede structural and kinetic data interpretation. While methods to minimize effects of back-exchange during protein analyte deposition on MALDI plates have been reported, this study presents a readily available, highly sensitive protein control set to facilitate rapid MALDI HDX protocol workup. The Ca(2+)-induced solvent accessible surface area (ASA) changes of calmodulin (CaM) and S100 proteins were employed to monitor and optimize HDX protocol efficiency. Under non- stringent room temperature conditions, the Ca(2+)-induced deuterium exchange of CaM, DeltaD(ca2+ -apo), MH(+) shifts -17 to -24 Da, while S100 DeltaD(ca2+ -apo) MH(+) shifts +8 to +12 Da. By comparing the divergent CaM and S100 Ca(2+)-induced deuterium mass shift differences, HDX sample workup and MALDI plate spotting conditions can easily be monitored.

Chelating N-pyrrolylphosphino-N'-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis.

Two families of variously-substituted N-pyrrolylphosphino-N'-arylaldimine ligands, 2-(aryl-N=CH)C4H3N-PR2 {R=Ph; R=Pri2N}, have been prepared from the corresponding pyrrolylaldimines . The donor characteristics/basicity of P-N-chelating and have been assessed using a combination of 31P{1H} NMR and IR spectroscopies through study of the magnitudes of 1JSeP for the phosphorus(V) selenides and , and measurement of nu(CO) for the complexes [RhCl(CO)(-kappa2-P,N)], respectively. The synthesis of the palladium(II) complexes [PdCl2(-kappa2-P,N)] was readily achieved from reaction of or with [PdCl2(MeCN)2] in CH2Cl2. X-Ray crystallographic studies of and confirm the chelating nature of the P-N ligands, which adopt a distorted 'envelope' conformation, and highlight the potentially significant steric demands of these metal scaffolds. Reaction of equimolar quantities of with [NiBr2(DME)] in MeCN afforded [NiBr2(-kappa2-P,N)], while the same reaction undertaken in CH2Cl2 with gave rise to the homoleptic bis(pyrrolatoimine) derivative [Ni{2-(mes-N=CH)C4H3N}2] in 45% yield, following P-N bond cleavage. Complex was characterised in the solid-state by X-ray crystallography. No identifiable metal-containing complexes could be obtained on reaction of with a variety of sources of Ni(II). The palladium dichloride complexes and proved inactive in combination with MAO or EtAlCl2 for ethylene polymerisation, and with methanesulfonic acid for CO/ethylene co-polymerisation. Contrastingly, the nickel complexes in combination with 4.5 eq. EtAlCl2 catalysed the formation of butenes and hexenes with moderate activity from ethylene at 1 bar.

Concise syntheses of tridentate PNE ligands and their coordination chemistry with palladium(II) : a solution- and solid-state study.

A straightforward methodology for the high-yielding synthesis of the di-functionalised phosphines {Ph2P(CH2)2NC4H8E, E = NMe (1), O (2), S (3)}via base-catalysed Michael addition is described. Reaction of the functionalised tertiary phosphines 1-3 with PdCl2(MeCN)2 affords complexes in which the ligands are bound in a tridentate fashion, namely [PdCl(kappa3-PNE)]Cl (6a, 8) as the predominant products. A kappa2-PN coordination mode was also identified crystallographically for ligand following its reaction with PdCl2(MeCN)2, which afforded [PdCl2(-kappa2-PN)] (6b) in ca. 5% yield. Conductivity studies of solutions of 6a are consistent with an ionic formulation, however the poor solubility of and precluded their study in a similar fashion. Analysis of bulk samples of [PdCl2(1)] (6) and [PdCl2(3)] (8) by 15N and 31P NMR spectroscopy in the solid state as consistent with exclusive tridentate binding of the PNE ligands. An X-ray crystallographic study has probed the coordination of in the unusual salt [PdCl(-kappa3-PNN)]2[Mg(SO4)2(OH2)4] (10) prepared by treating a methanolic solution of with excess MgSO4. No data could be obtained to support the transformation of 6a into 6b on addition of excess chloride. In contrast, 6a reacts regioselectively with the water-soluble phosphine Cy2PCH2CH2NMe3Cl to afford the cis-diphosphine complex cis-[PdCl(Cy2PCH2CH2NMe3Cl)(1-kappa2-PN)]Cl2 (9). Reaction of 1 with PdCl(Me)(COD) results in the formation of the kappa2-PN dichloride complex [PdCl(Me)(1-kappa(2)-PN)] (11). Attempts to prepare [Pd(Me)(MeCN)(-kappa2-PN)][PF6] (12) through reaction of 11 with NaPF6 in MeCN led to decomposition. Treatment of PdMe2(TMEDA) with 1 at low temperature initially affords [PdMe2(1-kappa2-NN)], which isomerises to afford [PdMe(2)(1-kappa(2)-PN)] (13); at temperatures greater than 10 degrees C complex 13 decomposes rapidly.