Alkali metal derivatives of an ortho-phenylene diamine

Treatment of the ortho-phenylene diamine C6H4-1,2-{N(H)Tripp}2 (1, PDAH2, Tripp = 2,4,6-triisopropylphenyl) with two equivalents of MR (M = Li, R = Bun; M = Na or K, R = CH2C6H5) afforded the dimetallated alkali metal ortho-phenylene diamide dianion complexes [(PDALi2)(THF)3] (2), [{(PDANa2)(THF)2}2] (3), and [{(PDAK2)(THF)3}2] (4). In contrast, treatment of 2 with two equivalents of rubidium or cesium 2-ethylhexoxide, or treatment of 1 with two equivalents of MR (M = Rb or Cs, R = CH2C6H5) did not afford the anticipated dialkali metal ortho-phenylene diamide dianion derivatives and instead formally afforded the monometallic ortho-diiminosemiquinonate radical anion species [PDAM] (M = Rb, 5; M = Cs, 6). The structure of 2 is monomeric with one lithium coordinated to the two nitrogen centres and the other lithium η4-coordinated to the diazabutadiene portion of the PDA scaffold. Similar structural cores are observed for 3 and 4, except that the larger sodium and potassium ions give dimeric structures linked by multi-hapto interactions from the PDA backbone phenyl ring to an alkali metal centre. Complex 5 was not characterised in the solid state, but the structure of 6 reveals coordination of cesium ions to both PDA amide centres and multi-hapto interactions to a PDA backbone phenyl ring in the next unit to generate a one-dimensional polymer. Complexes 2–6 have been variously characterised by X-ray crystallography, multi-nuclear NMR, FTIR, and EPR spectroscopies, and CHN microanalyses

Isolation of elusive HAsAsH in a crystalline diuranium(IV) complex

The HAsAsH molecule has hitherto only been proposed tentatively as a short-lived species generated in electrochemical or microwave-plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(TrenTIPS)}2(μ-η2:η2-As2H2)] (3, TrenTIPS=N(CH2CH2NSiPri3)3; Pri=CH(CH3)2). Complex 3 was prepared by deprotonation and oxidative homocoupling of an arsenide precursor. Characterization and computational data are consistent with back-bonding-type interactions from uranium to the HAsAsH π*-orbital. This experimentally confirms the theoretically predicted excellent π-acceptor character of HAsAsH, and is tantamount to full reduction to the diarsane-1,2-diide form

A new family of high nuclearity CoII/DyIII coordination clusters possessing robust and unseen topologies

Mixing Co(NO3)2·6H2O/Dy(NO3)3·6H2O/(E)-4-(2-hydroxy-3-methoxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one (HL)/pivalic acid/Et3N in various solvents results in the synthesis of seven compounds formulated as [CoII2DyIII2(μ3-MeO)2(L)2(piv)4(NO3)2] (3), [CoIIDyIII3(μ3-MeO)2(μ2-MeO)2(L)2(piv)2(NO3)3]·2(CH3OH) (4·2CH3OH), 2[CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8][CoII2DyIII5(μ3-OH)6(L)2(piv)8(NO3)4] (5), [CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8]·2(CH3CN) (6·2CH3CN), [CoII2DyIII5(μ3-OH)6(L)2(piv)8(NO3)4]·4(CH3CN) (7·4CH3CN), [CoII2DyIII2(μ3-OH)2(L)2(piv)2(NO3)2(EtOH)2(H2O)2](NO3)2·(EtOH) (8·EtOH) and [CoII4DyIII4(μ2-O)2(μ3-OH)4(L)4(piv)8] (9) with robust and unseen topologies. These show that the temperature and reaction time influence the formation of the final product. Preliminary magnetic studies, performed for 6 and 7 in the temperature range 2-300 K, are indicative of Single Molecule Magnet (SMM) behaviour. Moreover, analysis of the catalytic properties of compound 3 as an efficient catalyst for the synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary amines has been carried out

Variability in Laboratory vs. Field Testing of Peak Power, Torque, and Time of Peak Power Production Among Elite Bicycle Motocross Cyclists

The aim of this study was to ascertain the variation in elite male bicycle motocross (BMX) cyclists' peak power, torque, and time of power production during laboratory and field-based testing. Eight elite male BMX riders volunteered for the study, and each rider completed 3 maximal sprints using both a Schoberer Rad Messtechnik (SRM) ergometer in the laboratory and a portable SRM power meter on an Olympic standard indoor BMX track. The results revealed a significantly higher peak power (p <= 0.001, 34 ± 9%) and reduced time of power production (p <= 0.001, 105 ± 24%) in the field tests when compared with laboratory-derived values. Torque was also reported to be lower in the laboratory tests but not to an accepted level of significance (p = 0.182, 6 ± 8%). These results suggest that field-based testing may be a more effective and accurate measure of a BMX rider's peak power, torque, and time of power production

Actinide Triamidoamine (Tren^R) Chemistry:Uranium and Thorium Derivatives Supported by a Diphenyl‐tert‐Butyl‐Silyl‐Tren Ligand

We report the synthesis and characterisation of thorium(IV), uranium(III), and uranium(IV) complexes supported by a sterically demanding triamidoamine ligand with N-diphenyl-tert-butyl-silyl substituents. Treatment of ThCl4(THF)3.5 or UCl4 with [Li3(TrenDPBS)] (TrenDPBS = {N(CH2CH2NSiPh2But)3}3-) afforded [An(TrenDPBS)Cl] (An = Th, 1Th; U, 1U). Complexes 1An react with benzyl potassium to afford the cyclometallates (TrenDPBScyclomet) [An{N(CH2CH2NSiPh2But)2(CH2CH2NSiPhButC6H4)}] (An = Th, 2Th; U, 2U). Treatment of 1An with sodium azide affords [An(TrenDPBS)N3] (An = Th, 3Th; U, 3U). Reaction of 3Th with potassium graphite affords 2Th. In contrast, 3Th reacts with cesium graphite to afford the doubly-cyclometallated (TrenDPBSd-cyclomet) ate complex [Th{N(CH2CH2NSiPh2But) CH2CH2NSiPhButC6H4)}2Cs(THF)3] (4). In contrast to 3Th, reaction of 3U with potassium graphite produces the uranium(III) complex [U(TrenDPBS)] (5), and 5 can also be prepared by reaction of potassium graphite with 1U. The loss of azide instead of conversion to nitrides contrasts to prior work when the silyl group is iso-propyl silyl, underscoring how ligand substituents profoundly drive the reaction chemistry. Several complexes exhibit T-shaped meta-C-H···phenyl and staggered parallel p-p-stacking interactions, demonstrating subtle weak interactions that drive ancillary ligand geometries. Compounds 1An-3An, 4, and 5 have been variously characterised by single crystal X-ray diffraction, multi-nuclear NMR spectroscopy, infrared spectroscopy, UV/Vis/NIR spectroscopy, and elemental analyses

Nature of the Arsonium‐Ylide Ph3As=CH2 and a Uranium(IV) Arsonium‐Carbene Complex

Treatment of [Ph3EMe][I] with [Na{N(SiMe3)2}] affords the ylides [Ph3E=CH2] (E = As, 1As; P, 1P). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium‐ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P, confirming the long‐proposed hypothesis of increasing pyramidalisation of the ylide‐carbon, highlighting the increasing dominance of E+‐C‐ dipolar resonance form (sp3‐C) over the E=C ene p‐bonded form (sp2‐C), as group 15 is descended. The uranium(IV)‐cyclometallate complex [U{N(CH2CH2NSiPri3)2(CH2CH2SiPri2CH(Me)CH2)}] reacts with 1As and 1P by a‐proton abstraction to give [U(TrenTIPS)(CHEPh3)] (TrenTIPS = N(CH2CH2NSiPri3)3; E = As, 2As; P, 2P), where 2As is an unprecedented structurally characterised arsonium‐carbene complex. The short U‐C distances and obtuse U‐C‐E angles suggest significant U=C double bond character. A shorter U‐C distance is found for 2As than 2P, consistent with increased uranium‐ and reduced pnictonium‐stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations

Yttrium Methanide and Methanediide Bis(silyl)amide Complexes

The yttrium methanediide complex [Y(BIPM)(I)(THF)2] (BIPM = {C(PPh2NSiMe3)2}) was reacted with a series of potassium bis(silyl)amides to produce heteroleptic complexes by salt metathesis protocols. The methanediide complexes [Y(BIPM)(N″)(THF)] (1; N″ = {N(SiMe3)2}) and [Y(BIPM)(N**)(THF)] (2; N** = {N(SiMe2tBu)2}) were obtained for those relatively small bis(silyl)amides. Complex 2 undergoes thermal decomposition under vacuum to yield the methanide cyclometalate complex [Y(H-BIPM){N(SitBuMe2)(SitBuMeCH2)-κ2-N,C}] (3) as part of an otherwise intractable mixture of products. Complex 3 was also observed in trace amounts in mixtures of [Y(BIPM)(I)(THF)2] and KN**. In contrast, [Y(BIPM)(I)(THF)2] reacted with the more sterically demanding potassium bis(silyl)amides KN*† (N*† = {N(SiMe2tBu)(SiiPr3)}) and KN†† (N†† = {N(SiiPr3)2}) to afford the methanide cyclometalate complexes [Y(H-BIPM){N(SiiPr3)(SitBuMeCH2)-κ2-N,C)}] (4) and [Y(H-BIPM){N(SiiPr3)[SiiPr2(CHMeCH2)]-κ2-N,C}] (5), respectively. Complexes 1–5 were characterized as appropriate by multinuclear NMR and FTIR spectroscopy, elemental analyses, and single-crystal X-ray diffraction

Covalent Uranium Carbene Chemistry

After seminal reports of covalent uranium carbene U˭C complexes in the 1980s by Gilje, the area fell dormant for around 30 years. However, in the past five years, there has been a resurgence of interest in the area. Despite recent advances, the classification of these U˭C complexes as either methanediides, carbenes, or alkylidenes has remained a contentious issue. Herein, we review U˭C complexes reported to date, along with reactivity and computational studies, and conclude that although U˭C complexes sit midway on the continuum between rare-earth methanediides and Schrock-type alkylidenes, they can be justifiably described as carbenes

f-Element Zintl Chemistry: Actinide-Mediated Dehydrocoupling of H₂Sb^1- Affords the Tri-Thorium and -Uranium Undeca-Antimontriide Zintl Clusters [{An(Tren^TIPS)}₃(µ₃- Sb₁₁)] (An = Th, U; Tren^TIPS = {N(CH₂CH₂NSiⁱ Pr₃)₃}^3-)

Reaction of the cesium antimonide complex [Cs(18C6)2][SbH2] (1, 18C6 = 18-crown-6 ether) with the triamidoamine actinide separated ion pairs [An(TrenTIPS)(L)][BPh4] (TrenTIPS = {N(CH2CH2NSiiPr3)3}3-; An/L = Th/DME (2Th); U/THF (2U)) affords the triactinide undeca-antimontriide Zintl clusters [{An(TrenTIPS)}3(µ3-Sb11)] (An = Th (3Th), U (3U)) by dehydrocoupling. Clusters 3Th and 3U provide two new examples of the Sb113- Zintl trianion, and unprecedented examples of molecular Sb113- being coordinated to anything since all previous reports featured isolated Sb113- Zintl trianions in separated ion quadruple formulations with non-coordinating cations. Quantum chemical calculations describe dominant ionic An-Sb interactions in 3Th and 3U, though the data suggest that the latter exhibits slightly more covalent An-Sb linkages than the former. Complexes 3Th and 3U have been characterized by single crystal X-ray diffraction, NMR, IR, and UV/Vis/NIR spectroscopies, elemental analysis, and quantum chemical calculations

Thorium(IV) alkyl synthesis from a thorium(III) cyclopentadienyl complex and an Nheterocyclic olefin

Treatment of the tris(cyclopentadienyl) thorium(III) complex [Th(η5-Cp′′)3] [1, Cp′′ = C5H3-1,3- (SiMe3)2] with the N-heterocyclic olefin H2C=C(NMeCH)2 (2) reproducibly produces the thorium(IV)-methyl derivative [Th(η5-Cp′′)3(Me)] (3) along with MeImCH2CH2ImMe (Im = imidazole). The reaction mechanism, which is consistent with 1H NMR spectroscopic observations, is proposed to proceed via: (i) coordination of 2 to 1; (ii) one-electron transfer from thorium to 2; (iii) N-methyl cleavage and transfer to thorium to give 3; (iv) coupling of the resulting imidazolium radical by-product to give MeImCH2CH2ImMe. Complex 3 has been characterised by single crystal X-ray diffraction, multi-nuclear NMR and IR spectroscopies, and elemental analyses, and MeImCH2CH2ImMe by 1H NMR spectroscopy and mass spectrometry