Tandem manganese catalysis for the chemo-, regio-, and stereoselective hydroboration of terminal alkynes: in situ precatalyst activation as a key to enhanced chemoselectivity.

The manganese(ii) complex [Mn(iPrPNP)Cl2] (iPrPNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) was found to catalyze the stereo- and regioselective hydroboration of terminal alkynes employing HBPin (pinacolborane). In the absence of in situ activators, mixtures of alkynylboronate and E-alkenylboronate esters were formed, whereas when NaHBEt3 was employed as the in situ activator, E-alkenylboronate esters were exclusively accessed. Mechanistic studies revealed a tandem C-H borylation/semihydrogenation pathway accounting for the formation of the products. Stoichiometric reactions hint toward reaction of a Mn-H active species with the terminal alkyne as the catalyst entry pathway to the cycle, whereas reaction with HBPin led to catalyst deactivation.

Efficacy of a mindfulness-based programme with and without virtual reality support to reduce stress in university students: A randomized controlled trial.

OBJECTIVES: To evaluate the efficacy of a mindfulness-based programme (MBP) for reducing stress in university students and its action mechanisms and to explore the capacity of virtual reality (VR) exposure to enhance adherence to the intervention. METHODS: This randomized controlled trial (RCT) involved assessment time points of baseline, posttreatment, and 6-month follow-up. A total of 280 students from two Spanish universities were randomly assigned to 'MBP', 'MBP + VR', or 'Relaxation' (active controls). Perceived stress posttreatment was the primary outcome; wellbeing and academic functional outcomes were assessed as well. Multilevel mixed-effects models were performed to estimate the efficacy of the programme. RESULTS: Both 'MBP' (B = -2.77, d = -0.72, p = .006) and 'MBP + VR' (B = -2.44, d = -0.59, p = .014) were superior to 'Relaxation' in improving stress, as well as most of the secondary outcomes, with medium-to-large effects posttreatment and at follow-up. The long-term effects of MBPs on stress were mediated by mindfulness and self-compassion in parallel. Treatment adherence was improved in the 'MBP + VR' group, with higher retention rates and session attendance (p < .001). CONCLUSIONS: This RCT supports the efficacy of an MBP compared to relaxation for reducing stress in university students through mindfulness and self-compassion as mechanisms of change. VR exposure may enhance treatment adherence. TRIAL REGISTRATION: ClinicalTrials.gov NCT03771300.

Building C(sp3 ) Molecular Complexity on 2,2'-Bipyridine and 1,10-Phenanthroline in Rhenium Tricarbonyl Complexes.

The reactions of [Re(N-N)(CO)3 (PMe3 )]OTf (N-N=2,2'-bipyridine, bipy; 1,10-phenanthroline, phen) compounds with tBuLi and with LiHBEt3 have been explored. Addition to the N-N chelate took place with different site-selectivity depending on both chelate and nucleophile. Thus, with tBuLi, an unprecedented addition to C5 of bipy, a regiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably, when LiHBEt3 reacted with [Re(bipy)(CO)3 (PMe3 )]OTf, hydride addition to the 4 and 6 positions of bipy triggered an intermolecular cyclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resulted in partial reduction of one pyridine ring. The resulting neutral ReI products showed a varied reactivity with HOTf and with MeOTf to yield cationic complexes. These strategies rendered access to ReI complexes containing bipy- and phen-derived chelates with several C(sp3 ) centers.

C(sp2)-H Borylation of Heterocycles by Well-Defined Bis(silylene)pyridine Cobalt(III) Precatalysts: Pincer Modification, C(sp2)-H Activation and Catalytically Relevant Intermediates.

Well-defined bis(silylene)pyridine cobalt(III) precatalysts for C(sp2)-H borylation have been synthesized and applied to the investigation of the mechanism of the catalytic borylation of furans and pyridines. Specifically, [( Ar SiNSi)CoH3]·NaHBEt3 ( Ar SiNSi = 2,6-[EtNSi(NtBu)2CAr]2C5H3N, Ar = C6H5 (1-H 3 ·NaHBEt 3 ), 4-MeC6H4 (2-H 3 ·NaHBEt 3 )) and trans-[( Ar SiNSi)Co(H)2BPin] (Ar = C6H5 (1-(H) 2 BPin), 4-MeC6H4 (2-(H) 2 BPin), Pin = pinacolato) were prepared and employed as single component precatalysts for the C(sp2)-H borylation of 2-methylfuran, benzofuran and 2,6-lutidine. The cobalt(III) precursors, 2-H 3 ·NaHBEt 3 and 2-(H) 2 BPin also promoted C(sp2)-H activation of benzofuran, yielding [(ArSiNSi)CoH(Bf)2] (Ar = 4-MeC6H4, 2-H(Bf) 2 , Bf = 2-benzofuranyl). Monitoring the catalytic borylation of 2-methylfuran and 2,6-lutidine by 1H NMR spectroscopy established the trans-dihydride cobalt(III) boryl as the catalyst resting state at low substrate conversion. At higher conversion two distinct pincer modification pathways were identified, depending on the substrate and the boron source.

Subgrouping a Large U.S. Sample of Patients with Fibromyalgia Using the Fibromyalgia Impact Questionnaire-Revised.

Fibromyalgia (FM) is a heterogeneous and complex syndrome; different studies have tried to describe subgroups of FM patients, and a 4-cluster classification based on the Fibromyalgia Impact Questionnaire-Revised (FIQR) has been recently validated. This study aims to cross-validate this classification in a large US sample of FM patients. A pooled sample of 6280 patients was used. First, we computed a hierarchical cluster analysis (HCA) using FIQR scores at item level. Then, a latent profile analysis (LPA) served to confirm the accuracy of the taxonomy. Additionally, a cluster calculator was developed to estimate the predicted subgroup using an ordinal regression analysis. Self-reported clinical measures were used to examine the external validity of the subgroups in part of the sample. The HCA yielded a 4-subgroup distribution, which was confirmed by the LPA. Each cluster represented a different level of severity: "Mild-moderate", "moderate", "moderate-severe", and "severe". Significant differences between clusters were observed in most of the clinical measures (e.g., fatigue, sleep problems, anxiety). Interestingly, lower levels of education were associated with higher FM severity. This study corroborates a 4-cluster distribution based on FIQR scores to classify US adults with FM. The classification may have relevant clinical implications for diagnosis and treatment response.

Enabling Two-Electron Pathways with Iron and Cobalt: From Ligand Design to Catalytic Applications.

Homogeneous catalysis with Earth-abundant, first-row transition metals, including iron and cobalt, has gained considerable recent attention as a potentially cost-effective and sustainable alternative to more commonly and historically used precious metals. Because fundamental organometallic transformations, such as oxidative addition and reductive elimination, are two-electron processes and essential steps in many important catalytic cycles, controlling redox chemistry-in particular overcoming one-electron chemistry-has been as a central challenge with Earth-abundant metals. This Perspective focuses on approaches to impart sufficiently strong ligand fields to generate electron-rich metal complexes able to promote oxidative addition reactions where the redox changes are exclusively metal-based. Emphasis is placed on how ligand design and exploration of fundamental organometallic chemistry coupled with mechanistic understanding have been used to discover iron catalysts for the hydrogen isotope exchange in pharmaceuticals and cobalt catalysts for C(sp2)-H borylation reactions. A pervasive theme is that first-row metal complexes often promote unique chemistry from their precious-metal counterparts, demonstrating that these elements offer a host of new opportunities for reaction discovery and for more sustainable catalysis.

Rhenium-catalysed hydroboration of aldehydes and aldimines.

The first examples for the rhenium-catalysed hydroboration of aldehydes, ketones and aldimines, including heteroaromatic quinoline, are reported herein. Reactions are remarkably chemoselective and tolerant of several functional groups. A wide array of rhenium complexes were efficient pre-catalysts for these hydroborations, including new low-valent complexes of the formula [Re(N-N)(CO)3(L)]X (N-N = bipy derivative, L = labile ligand/solvent, and X = [BArF4]- and [B(3,5-di-tBu-cat)2]-), which have been characterized fully including an X-ray diffraction study for [Re(bipy)(CO)3(quin)][BArF4] (2). A new silver spiroboronate ester Ag[B(3,5-di-tBu-cat)2](NCCH3)3 (3) was prepared and characterized fully, including an X-ray diffraction study, and used to make one of the new rhenium complexes.

Interligand C-C Coupling between α-Methyl N-Heterocycles and bipy or phen at Rhenium Tricarbonyl Complexes.

Intramolecular C-C coupling between N-bonded 1,2-dimethylimidazole, 2-methyloxazoline, or 2-methylpyridine and either 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen) ligands results from α-methyl group deprotonation in the coordination sphere of Re(CO)3 fragments. The nucleophilic CH2 group generated by the deprotonation attacks the 6 (bipy) or 2 (phen) positions of the diimines, dearomatizing the involved pyridine ring and generating new asymmetric, fac-capping tridentate ligands.

Nucleophilic Additions to Coordinated 1,10-Phenanthroline: Intramolecular, Intermolecular, Reversible, and Irreversible.

KN(SiMe3 )2 reacts with [Re(CO)3 (phen)(PMe3 )]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe3 ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines.

Deprotonation of coordinated phosphanes in a rhenium complex: C-C coupling with diimine coligands.

The reaction of fac-[Re(bipy)(CO)3(PMe3)][OTf] (bipy = 2,2'-bipyridine) with KN(SiMe3)2 affords two neutral products: cis,trans-[Re(bipy)(CO)2(CN)(PMe3)], and a thermally unstable compound, which features a new C-C bond between a P-bonded methylene group (from methyl group deprotonation) and the C6 position of bipy. The solid-state structures of more stable 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene analogs, resulting from the deprotonation of PMe3, PPhMe2, and PPh2Me ligands, are determined by X-ray diffraction.

Intramolecular nucleophilic addition to the 2 position of coordinated 2,2'-bipyridine by a deprotonated dimethyl sulfide ligand.

Deprotonation of the dimethyl sulfide ligand in [Re(bipy)(CO)3(SMe2)][OTf] (1) by KN(SiMe3)2 afforded a mixture of two diastereomers (2M and 2m) in which a C-C bond has been formed between the S-bonded CH2 group and the 2 position of 2,2'-bipyridine. The solid-state structure of the more stable 2,6-(i)Pr-BIAN analogue could be determined by X-ray diffraction.