Paediatric brain MRI findings following congenital heart surgery: a systematic review.

OBJECTIVE: This systematic review aimed to establish the relative incidence of new postoperative brain MRI findings following paediatric congenital cardiac surgery. DESIGN: To distinguish perioperative changes from pre-existing MR findings, our systematic search strategy focused on identifying original research studies reporting both presurgery and postsurgery brain MRI scans. Patient demographics, study methods and brain MR findings were extracted. RESULTS: Twenty-one eligible publications, including two case-control and one randomised controlled trial, were identified. Pre-existing brain MRI findings were noted in 43% (513/1205) of neonates prior to surgery, mainly white matter injuries (WMI). Surgery was performed at a median age of 8 days with comparison of preoperative and postoperative MR scans revealing additional new postoperative findings in 51% (550/1075) of patients, mainly WMI. Four studies adopted a brain injury scoring system, but the majority did not indicate the severity or time course of findings. In a subgroup analysis, approximately 32% of patients with pre-existing lesions went on to develop additional new lesions postsurgery. Pre-existing findings were not found to confer a higher risk of acquiring brain lesions postoperatively. No evidence was identified linking new MR findings with later neurodevelopmental delay. CONCLUSION: This systematic review suggests that surgery approximately doubles the number of patients with new brain lesions.

Changes in pediatric seizure-related emergency department attendances during COVID-19 - A territory-wide observational study.

A territory-wide retrospective observational study was conducted in Hong Kong between January 23 to April 22, 2020 to demonstrate changes in pediatric seizure-related accident and emergency department (A&E) visits during the COVID-19 pandemic. Parallel periods from 2015 to 2019 were used as control. All-cause A&E attendances in all paediatric age groups decreased significantly during the study period. Seizure-related attendances decreased across all pediatric age-groups in 2020 (RR 0.379, 95% CI 0.245-0.588), with a disproportionately large decrease in the 0-6 years age group (RR 0.303, 95% CI 0.174-0.526) compared with the 7-18 years age group (RR 0.534, 95% CI 0.393-0.719). Decrease in RTI-related A&E attendances was also more drastic in the 0-6 age group. The two time trends are congruent in the 0-6 years but not the 7-18 years age group. Such a trend is suggestive of the usefulness of infection control measures in seizure prevention, especially amongst young children.

Palladium-Catalyzed N-Arylation of Sulfoximines with Aryl Sulfonates.

Palladium-catalyzed C-N bond coupling reaction between NH-sulfoximines and aryl halides (e.g., -Br, -I, and -Cl and pseudohalides -OTf and -ONf) was successfully achieved. Nevertheless, aryl tosylates/mesylates left much to be achieved. In this report, a general N-arylation of sulfoximines with aryl sulfonates is described. Using Pd(OAc)2/MeO-CM-phos complex, the N-aryl sulfoximine products can be obtained in good-to-excellent yields (up to 99%) with good common functional group compatibility. In addition to arene moieties, alkenyl tosylates are shown to be successful coupling partners.

Divalent europium and ytterbium complexes supported by a bulky 2-pyridyl amido ligand: synthesis, structure and reactivity studies.

Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pr(i)2-2,6)(2-C5H3N-6-Me)] (1) with potassium hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pr(i)2-2,6)(2-C5H3N-6-Me)] (2) and KL(THF)2 (3), respectively. Treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 afforded the corresponding Ln(II) amido complexes [EuL(µ-L)2K(THF)] (4) and [YbL2(THF)2] (5). In contrast, an analogous reaction of SmI2(THF)2 with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL3] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine yielded the trivalent [EuL3] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the bis(amido) Yb(III) iodide complex [YbL2(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(I) iodide. A subsequent reaction of 8 with KOBut gave, unexpectedly, the Yb(III) triamide [YbL3] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL3] (9) as the only isolable product. The solid-state structures of complexes 2 and 4­9 were elucidated by X-ray diffraction analysis.

Selective cage boron/carbon extrusion reaction of 13-vertex carborane µ-1,2-(CH2)3-1,2-C2B11H11: formation of nido-CB10, closo-CB10, and closo-C2B10 species.

The nature of nucleophiles greatly influences the reactivity patterns of 13-vertex carboranes. µ-1,2-(CH(2))(3)-1,2-C(2)B(11)H(11) reacts with Et(3)N/MeOH, pyridine or bipyridine to give cage-boron and -carbon extrusion products nido-CB(10) or closo-CB(10), or a cage-boron extrusion compound closo-C(2)B(10) while the cage-carbon extrusion species closo-CB(11) monoanions are produced by treatment with MeOH or Ph(3)P.

Reaction of a 14-vertex carborane with nucleophiles: formation of nido-C(2)B(12), nido-C(2)B(11,) and closo-CB(11) carborane anions.

Nucleophilic reactions of a 14-vertex closo-carborane are reported. 2,3-(CH(2))(3)-2,3-C(2)B(12)H(12) (1) reacts with MeOH at 70 degrees C to give closo-CB(11) anions [1,2-(CH(2))(3)CH(OMe)-1-CB(11)H(10)](-) ([2a](-)), [1,2-(CH(2))(2)CH(OMe)CH(2)-1-CB(11)H(10)](-) ([2b](-)), and [1,2-(CH(2))(2)CH horizontal lineCH-1-CB(11)H(10)](-) ([2c](-)). It is suggested that [2c](-) is an intermediate for the isomerization from [2a](-) to [2b](-). Treatment of 1 with MeOH/Me(3)N, (t)BuOK or LiNMe(2) affords nido-C(2)B(12) species [8,9-(CH(2))(3)-mu-11,12-(Nu)BH-8,9-C(2)B(11)H(11)](-) (Nu = MeO ([3a](-)), (t)BuO ([3b](-)), and Me(2)N ([3c](-))). In the presence of acid such as HCl, anions [3](-) are converted to 1. However, [3](-) undergo deboration reaction, in the presence of bases, to generate a nido-C(2)B(11) anion [8,9-(CH(2))(3)-8,9-C(2)B(11)H(12)](-) ([4](-)) that can also be formed directly from the reaction of 1 with excess CsF or piperidine. Mechanistic studies show that [3a](-) is the first intermediate in the reaction of 1 with MeOH and [4](-) is unlikely an intermediate.

Synthesis, structure, and reaction chemistry of samarium(II), europium(II), and ytterbium(II) complexes of the unsymmetrical benzamidinate ligand [PhC(NSiMe(3))(NC(6)H(3)Pr(i)(2)-2,6)](-).

Neutral mononuclear lanthanide(II) bis(amidinate) complexes [LnL(2)(THF)(x)] [L = PhC(NSiMe(3))(NC(6)H(3)Pr(i)(2)-2,6)(-); Ln = Sm, x = 2 (3); Ln = Eu, x = 2, (4); Ln = Yb, x = 1 (5)] were synthesized by the reaction of the appropriate LnI(2)(THF)(2) with potassium amidinate [KL](n) (2). The reduction chemistry of 3-5 was also examined. The reaction of the Sm(II) and Eu(II) amidinates 3 and 4 with diphenyl dichalcogenides PhEEPh (E = Se, Te) led to the binuclear lanthanide(III) amidinate-chalcogenolate complexes [LnL(2)(mu-EPh)](2) [Ln = Sm, E = Se (6); Ln = Eu, E = Se (7); Ln = Sm, E = Te (9)], whereas reacting the Yb(II) bis(amidinate) 5 with PhSeSePh yielded the mononuclear [YbL(2)(SePh)(THF)] (8). The reaction of 5 with iodine led to the Yb(III) bis(amidinate) iodide complex [YbL(2)(I)(THF)] (10). Treatment of 3 with N,N'-dicyclohexylcarbodiimide afforded the mixed-ligand Sm(III) tris(amidinate) [SmL(2){CyNC(H)NCy}] (11) (Cy = cyclohexyl). The molecular structures of complexes 2-5 and 7-11 were elucidated by X-ray diffraction analyses.

Benzenoid and quinonoid nitrogen-containing heteropentacenes.

Benzenoid or quinonoid-that is the question? In connection with the debate on the structure of dihydro-5,7,12,14-tetraazapentacene, both benzenoid and quinonoid nitrogen-containing heteropentacenes were successfully isolated and investigated (see picture). This report presents an exploratory study of the molecular and electronic structures, molecular packing, and semiconductor properties of the two compounds. These findings may lead to useful implications for the interesting ladder polymers.

Synthesis, structure, and reactivity of zirconacyclopentene incorporating a carboranyl unit.

A zirconacyclopentene incorporating a carboranyl unit 1,2-[Cp2ZrC(Et)=C(Et)]-1,2-C2B10H10 (1), an analogue of well-known zirconacyclopentadienes, was prepared and fully characterized from the reaction of Cp2Zr(mu-Cl)(mu-C2B10H10)Li(OEt2)2 with EtC OCEt in reflux toluene. Complex 1 resembles zirconacyclopentadienes in some reactions, and on the other hand, it has unique properties of its own. Many carborane derivatives with interesting structural features such as 1-[CI(Et)=C(Et)]-1,2-C2B10H11, naphthalocarborane, and 1,2-[C(Et)=C(Et)]-1,2-C2B10H10 can be conveniently prepared from 1. This work shows that 1 provides a very valuable entry point to the synthesis of various kinds of carborane derivatives that can not be prepared by conventional methods.

Hydrogen-mediated metal-carbon to metal-boron bond conversion in metal-carboranyl complexes.

A hydrogen-mediated Ru-C to Ru-B bond conversion was observed experimentally and supported by the theoretical calculations. Treatment of [eta(5):sigma(C)-Me(2)C(C(5)H(4))(C(2)B(10)H(10))]Ru(COD) (1) bearing a Ru-C(cage) sigma bond with PR(3) in the presence of H(2) gave Ru-B(cage) bonded complexes [eta(5):sigma(B)-Me(2)C(C(5)H(4))(C(2)B(10)H(10))]RuH(2)(PR(3)) (R = Cy (2), Ph (3)) (sigma(C): Ru-C(cage) sigma bond; sigma(B): Ru-B(cage) sigma bond). Complex 3 was converted to [eta(5):sigma(B)-Me(2)C(C(5)H(4))(C(2)B(10)H(10))]Ru(L(2)) in the presence of L(2) (L(2) = dppe (4), PPh(3)/P(OEt)(3) (5), PPh(3)/pyridine (6)) via liberation of H(2) upon heating. These complexes were fully characterized by various spectroscopic techniques, elemental analyses, and single-crystal X-ray diffraction studies. DFT calculations show that this conversion process is both kinetically and thermodynamically favorable and requires involvement of a hydride ligand.

Transistors from a conjugated macrocycle molecule: field and photo effects.

This study explores a conjugated macrocycle molecule and details its synthesis, molecular structure, assemblies in the solid state and application in phototransistors.

Synthesis, structure, and reactivity of Group 4 metallacycles incorporating a Me2C-linked cyclopentadienyl-carboranyl ligand.

Group 4 metallacycles [eta5:sigma-Me2C(C5H4)(C2B10H10)]Ti[eta2-N(Me)CH2CH2N(Me)] (1a), [eta5:sigma-Me2C(C5H4)(C2B10H10)]Zr[eta2-N(Me)CH2CH2N(Me)](HNMe2) (1b) and [eta5:sigma-Me2C(C5H4)(C2B10H10)]M[eta2-N(Me)CH2CH2CH2N(Me)] (M = Ti (2a), Zr (2b), Hf (2c)) were synthesized by reaction of [eta5:sigma-Me2C(C5H4)(C2B10H10)]M(NMe2)(2) (M = Ti, Zr, Hf) with MeNH(CH2)(n)NHMe (n = 2, 3). These metal complexes reacted with unsaturated molecules such as 2,6-Me2C6H3NC, PhNCO and PhCN to give exclusively M-N bond insertion products. The M-C(cage) bond remained intact. Such a preference of M-N over M-C(cage) insertion is suggested to most likely be governed by steric factors, and the mobility of the migratory groups plays no obvious role in the reactions. This work also shows that the insertion of unsaturated molecules into the metallacycles is a useful and effective method for the construction of very large ring systems.

Synthesis, structure, reactivity, and thermal isomerization of boron-substituted 13-vertex cobaltacarboranes (eta5-Cp)Co(eta6-R2C2B10Me8H2) (R = H, Et).

Reduction of boron-substituted carboranes o-R2C2B10Me8H2 (R = H, Et), thermal isomerization, and nucleophilic reaction of the resultant 13-vertex cobaltacarboranes were studied. Reaction of o-C2B10Me8H4 (1) with excess potassium metal in tetrahydrofuran (THF) gave, after recrystallization from a THF solution of 18-crown-6 ether, [[K(18-crown-6)(THF)2][K(18-crown-6)]][[4-(18-crown-6)-2,3,5,8,9,11,12,13-Me8-4,1,6-KC2B10H4]2] (2) in 78% yield. Interaction of 1 with excess sodium or potassium metal in THF, followed by treatment with CoCl2/CpNa and then aerobatic oxidation, afforded two boron-substituted 13-vertex cobaltacarboranes, 4-Cp-2,3,5,8,9,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (3) and 4-Cp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (4), in 15% and 8% yield, respectively. Subsequently, thermal isomerization of 3 and 4 yielded another two new isomers, 4-Cp-2,3,5,6,8,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (5) and 4-Cp-2,3,5,6,7,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (6). Treatment of 3 or 4 with strong bases such as nBuLi and MeLi generated unexpected nucleophilic substitution products 4-nBuCp-2,3,5,8,9,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (7), 4-nBuCp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (8a), and 4-MeCp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (8b) in good yields. Under the same reaction conditions, however, only one 13-vertex cobaltacarborane, 4-Cp-1,9-Et2-2,5,6,7,8,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (10), was isolated when o-Et2C2B10Me8H2 (9) was used as the starting material. Complex 10 is a thermodynamically stable product and has a substitution pattern different from that of 3-6. These results show that the substituents on either the cage carbon or boron atoms have an important effect on the formation and thermal stability of the 13-vertex metallacarboranes. The formation of these complexes can be rationalized by the diamond-square-diamond mechanism.

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2).

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.

Nickel-mediated regioselective [2 + 2 + 2] cycloaddition of carboryne with alkynes.

Transition metal-benzyne complexes have found many applications in organic synthesis, mechanistic studies, and the synthesis of functional materials. In sharp contrast, the chemistry of transition metal-carboryne complexes, especially late transition metal complexes, is virtually unknown. This communication reports a novel nickel-mediated regioselective [2 + 2 + 2] cycloaddition reaction of carboryne with alkynes via the Ni-carboryne intermediate (eta2-C2B10H10)Ni(PPh3)2. Because of the bulkiness of the carborane moiety, a high regioselectivity was achieved in the reactions involving unsymmetrical alkynes. This work furnishes a novel method for the preparation of highly substituted benzocarboranes which are difficult to obtain by other methods.