Lanthanoid Biphenolates as a Rich Source of Lanthanoid-Main Group Heterobimetallic Complexes.

Several new trivalent dinuclear rare earth 2,2'-methylenebis(6-tert-butyl-4-methylphenolate) (mbmp2- ) complexes with the general form [Ln2 (mbmp)3 (thf)n ] (Ln=Sm 1, Tb 2 (n=3), and Ho 3, Yb 4 (n=2), and a tetravalent cerium complex [Ce(mbmp)2 (thf)2 ] (5) have been synthesised by RTP (redox transmetallation/protolysis) reactions from lanthanoid metals, Hg(C6 F5 )2 and the biphenol mbmpH2 . These new complexes and some previously reported partially protonated rare earth biphenolate complexes [Ln(mbmp)(mbmpH)(thf)n ] react with lithium, aluminium, potassium and zinc organometallic reagents to form lanthanoid-main group heterobimetallic species. When reaction mixtures containing the Ln biphenolate complexes were treated with n-butyllithium, both molecular ([Li(thf)2 Ln(mbmp)2 (thf)n ] (Ln=La 6, Pr 7 (n=2) and Er 8, Yb 9, and Lu 10 (n=1)) and charge separated ([Li(thf)4 ][Ln(mbmp)2 (thf)2 ] (Ln=Y 11, Sm 12, Dy 13, and Ho 14) complexes were isolated. Treatment with trimethylaluminium also led to isolation of molecular ([AlMe2 Ln(mbmp)2 (thf)2 ] (Ln=Pr 15, Sm 16, and Tb 17)) and ionic [La(mbmp)(thf)5 ][AlMe2 (mbmp)] (18) complexes. One gadolinium-potassium ([K(thf)3 Gd(mbmp)2 (thf)2 ] (19)), and one ytterbium-zinc species ([ZnEtYb(mbmp)2 (thf)] (20)) were isolated from treatment of reaction mixtures with potassium bis(trimethylsilyl)amide and diethylzinc respectively.

New lanthanoid biphenolate complexes, their further reactivity with trimethylaluminium and catalytic activity for the polymerisation of rac-lactide.

A series of rare earth biphenolate complexes of the general form [Ln(mbmp)(mbmpH)(thf)3] (Ln = Y (1), Nd (2), Gd (3), Dy (4), Er (5), Tm (6) and Lu (7)) have been synthesised by redox transmetallation/protolysis (RTP) from the free rare earth metal, Hg(C6F5)2 and 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (mbmpH2). The rare earth metal is six coordinate with one chelating biphenolate mbmp2- ligand and one unidentate monophenolate mbmpH- ligand. The yttrium complex, when crystallised from hot toluene or deuterated benzene, loses a coordinated thf and exhibits coordination through all three phenolate oxygen atoms, as well as the oxygen of the phenol, yielding two solvates [Y(mbmp)(mbmpH)(thf)2]·nsolv (solv = PhMe, n = 1 (8a) or C6D6, n = 2 (8b)). Of these rare earth complexes, the yttrium derivative (1) yielded the heterobimetallic complex [AlMe2Y(mbmp)2(thf)2] (9) when treated with trimethylaluminium, whereas all other complexes produced the transmetallation product [AlMe(mbmp)(thf)] (11). The dinuclear dysprosium complex [Dy2(mbmp)3(thf)3] (10) was isolated alongside 11 from the reaction of 4 with trimethylaluminium, suggesting trimethylaluminium instigates a redistribution reaction. The ROP activity of the mononuclear neodymium, dysprosium, lutetium, and aluminium complexes towards rac-lactide in toluene at 70 °C was found to be poor compared to rare earth complexes of monodentate aryloxides, but increased with increased rare earth ion size.

Short-term outcomes of transcatheter closure of secundum atrial septal defect in children and adolescents: An experience of two centers in Upper Egypt.

BACKGROUND: The aim of this study was to evaluate the acute and short-term outcomes of transcatheter closure of secundum atrial septal defect (ASD) in children and adolescents in the first 4-year experience in two institutional centers in Upper Egypt. METHODS: This was a retrospective cohort study including 135 children and adolescents who underwent ASD closure between April 2012 and May 2016. A review of the acute and short-term outcomes and adverse events was performed. RESULTS: The patients had a median age of 5 years (interquartile range: 3-9 years), 71% of patients were ≤5 years, and median weight was 17 kg (interquartile range: 13-30 kg). Single defects were observed in 113 patients (84%). The remainder had multiple or multifenestrated defects that were closed by a single device. The mean defect size of single defects and the mean interatrial septum length were 15.24 ± 5.16 mm and 38.13 ± 6.3 mm, respectively. The ratio of device to TEE (Transoesophageal echocardiography) size of ASD was 1.19 ± 0.12. The devices were implanted successfully in 98.5% of patients. Six cases had concordant PS (Pulmonary stenosis), patent ductus arteriosus or perimembranous ventricular septal defect and were treated with balloon dilation, or closure. No residual flow was seen after device placement except in one patient with multiple fenestrations. There were five high-severity adverse events (3.7%) with no mortality. Device erosion was confirmed in one of two patients with massive haemopericardium; embolization of the device with retrieval in one patient; and heart block was detected in two cases. No cardiac perforation, device erosion, embolization, thrombus formation, or clinical evidence of bacterial endocarditis was observed during follow-up. CONCLUSIONS: Transcatheter closure of ASDs in children and adolescents was feasible and safe in the first 4 years experience in our centers, with good short-term outcome. Balloon sizing is not necessary for transcatheter closure of secundum ASD. Multiple defects can be safety closed by a single device.

Lanthanoid Pseudo-Grignard Reagents: A Major Untapped Resource.

Pseudo-Grignard reagents PhLnI (Ln=Yb, Eu), readily prepared by the oxidative addition of iodobenzene to ytterbium or europium metal at -78 °C in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME), react with a range of bulky N,N'-bis(aryl)formamidines to generate an extensive series of LnII or more rarely LnIII complexes, namely [Eu(DippForm)I(thf)4 ]⋅thf (1), [{EuI2 (dme)2 }2 ] (2), [Eu(XylForm)I(dme)2 ]⋅0.5 dme (3 a), [Eu(XylForm)I(dme)(µ-dme)]n (3 b), [{Eu(XylForm)I(µ-OH)(thf)2 }2 ] (4), [Yb(DippForm)I(thf)3 ]⋅thf (5 a), [Yb(DippForm)I2 (thf)3 ]⋅2 thf (5 b), [{Yb(MesForm)I(thf)2 }2 ] (6), [{Yb(XylForm)I(thf)2 }2 ] (7 a), and [Yb(XylForm)2 I(dme)]⋅dme (7 b) {(Form=ArNCHNAr; XylForm (Ar=2,6-Me2 C6 H3 ), MesForm (Ar=2,4,6-Me3 C6 H2 ), DippForm (Ar=2,6-iPr2 C6 H3 )}. Reaction of PhEuI and MesFormH in DME consistently gave 2, and reaction with XylFormH in THF gave 4. Europium complexes 1 and 3 a are seven-coordinate divalent monomers, whilst 3 b is a seven-coordinate dme-bridged polymer. Complex 5 a of the smaller YbII is a six-coordinate monomer, but the related 6 and 7 a are six-coordinate iodide-bridged dimers. 4 is a trivalent seven-coordinate hydroxide-bridged dimer, whereas complexes 5 b and 7 b are seven-coordinate monomeric YbIII derivatives. A characteristic structural feature is that iodide ligands are cisoid to the formamidinate ligand. To illustrate the synthetic scope of the pseudo-Grignard reagents, [Yb(Ph2 pz)I(thf)4 ] (Ph2 pz=3,5-diphenylpyrazolate) was oxidised with 1,2-diiodoethane to afford seven-coordinate monomeric pyrazolato-ytterbium(III) iodide [Yb(Ph2 Pz)I2 (thf)3 ] (8) in high yield, whilst metathesis between [Yb(Ph2 pz)I(thf)4 ] and NaCp (Cp=C5 H5 ) gave [Yb(C5 H5 )(Ph2 pz)(thf)]n (9), a nine-coordinate η5 :η5 -Cp-bridged coordination polymer. Reaction of the pseudo-Grignard reagent MeYbI with KN(SiMe3 )2 gave [K(dme)4 ][Yb{N(SiMe3 )2 }3 ] (10) with a charge-separated three-coordinate homoleptic [Yb{N(SiMe3 )2 }3 ]- anion, a complex that could be obtained in high yield by deliberate synthesis from YbI2 and KN(SiMe3 )2 in DME.