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131.
Beşli S Coles SJ Davies DB Hursthouse MB Kiliç A Shaw RA 《Dalton transactions (Cambridge, England : 2003)》2007,(26):2792-2801
Nucleophilic substitution reactions of cyclotriphosphazene derivatives having five-membered spiro rings, N(3)P(3)Cl(4)[O(CH(2))(2)X] (X = NH or O) with alkoxides (of tetraethylene glycol and some mono-functional alcohols) give unexpected rearrangements to form stable seven-membered ring ansa compounds, even though crystallographic evidence shows ring distortion and compression of the cyclophosphazene ring. With weaker nucleophiles such as sodium phenoxide and pyrrolidine substitution at a PCl2 group is preferred and no rearrangement takes place. In contrast, reactions of the analogous phosphazenes containing six-membered spiro rings, N(3)P(3)Cl(4)[O(CH(2))(3)X], with all of the above reagents give only normal substitution reactions at the PCl2 moieties and no rearrangement products. The spiro to ansa rearrangements in cyclophosphazenes are remarkable as the reported primary reaction products with the same difunctional reagents HO(CH(2))(2)XH are predominantly spiro, with some dangling and bridging derivatives, but no ansa compounds. 相似文献
132.
Ryan J. Schwamm Jeffrey R. Harmer Matthias Lein Christopher M. Fitchett Simon Granville Martyn P. Coles 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(36):10776-10779
More than 80 years after Paneth’s report of dimethyl bismuth, the first monomeric BiII radical that is stable in the solid state has been isolated and characterized. Reduction of the diamidobismuth(III) chloride Bi(NONAr)Cl (NONAr=[O(SiMe2NAr)2]2−; Ar=2,6‐iPr2C6H3) with magnesium affords the BiII radical .Bi(NONAr). X‐ray crystallographic measurements are consistent with a two‐coordinate bismuth in the +2 oxidation state with no short intermolecular contacts, and solid‐state SQUID magnetic measurements indicate a paramagnetic compound with a single unpaired electron. EPR and density functional calculations show a metal‐centered radical with >90 % spin density in a p‐type orbital on bismuth. 相似文献
133.
Dr. Riccardo Bonsignore Sophie R. Thomas Dr. Wim T. Klooster Dr. Simon J. Coles Dr. Robert L. Jenkins Dr. Didier Bourissou Prof. Giampaolo Barone Prof. Angela Casini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4226-4231
With the aim of exploiting new organometallic species for cross-coupling reactions, we report here on the AuIII-mediated Caryl−P bond formation occurring upon reaction of C^N cyclometalated AuIII complexes with phosphines. The [Au(C^N)Cl2] complex 1 featuring the bidentate 2-benzoylpyridine (CCON) scaffold was found to react with PTA (1,3,5-triaza-7-phosphaadamantane) under mild conditions, including in water, to afford the corresponding phosphonium 5 through C−P reductive elimination. A mechanism is proposed for the title reaction based on in situ 31P{1H} NMR and HR-ESI-MS analyses combined with DFT calculations. The C−P coupling has been generalized to other C^N cyclometalated AuIII complexes and other tertiary phosphines. Overall, this work provides new insights into the reactivity of cyclometalated AuIII compounds and establishes initial structure–activity relationships to develop AuIII-mediated C−P cross-coupling reactions. 相似文献
134.
Max S. Coles Gina Quach Dr. Jonathon E. Beves Dr. Evan G. Moore 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9609-9613
The development of photocatalytic reactions has provided many novel opportunities to expand the scope of synthetic organic chemistry. In parallel with progress towards uncovering new reactivity, there is consensus that efforts focused on providing detailed mechanistic insight in order to uncover underlying excited-state reactions are essential to maximise formation of desired products. With this in mind, we have investigated the recently reported sensitization-initiated electron transfer (SenI-ET) reaction for the C−H arylation of activated aryl halides. Using a variety of techniques, and in particular nanosecond transient absorption spectroscopy, we are able to distinguish several characteristic signals from the excited-state species involved in the reaction, and subsequent kinetic analysis under various conditions has facilitated a detailed insight into the likely reaction mechanism. 相似文献
135.
Albers T Baker J Coles SJ Edwards PG Kariuki B Newman PD 《Dalton transactions (Cambridge, England : 2003)》2011,40(37):9525-9532
Nine-membered 1,4,7-triphospha- and triarsamacrocycles with unsaturated benzo-backbones have been prepared using the [Cp(R)Fe](+) unit as a template. The cyclisation involves the attack of a coordinated phosphide (or arsenide) nucleophile at an activated, electrophilic ortho-fluorophenyl substituent on a neighbouring pnictide donor. The macrocycle assembly is of the 2 + 1 type where two new chelate rings are formed from appropriately derivatised bidentate and monodentate phosphines/arsines. Both [(η(5)-C(5)H(5))Fe](+) and [(η(5)-C(5)Me(5))Fe](+) may be employed for the cyclisation with higher yields generally being observed with the unsubstituted Cp. All new compounds have been characterised by spectroscopic and analytical methods including the single-crystal X-ray structure determination of [(η(5)-C(5)H(5))Fe(tribenzo-9aneP(3)-Ph,Ph(F)(2))](+), 3a, and [(η(5)-C(5)H(5))Fe(tribenzo-9aneAs(3)-Ph,Ph(F)(2))](+), 5, as the tetraphenylborate salts. The crystal structures are isomorphous and show the unique conformation of these new macrocycles with a 'cup shaped' cavity formed by the rigid benzo-backbones. The 9aneAs(3) derivative is the first example of a nine-membered triarsamacrocycle. 相似文献
136.
Beşli S Coles SJ Davies DB Kılıç A Shaw RA 《Dalton transactions (Cambridge, England : 2003)》2011,40(19):5307-5315
Cyclotriphosphazene derivatives containing a P-NHR group in the side-chain react in the presence of a strong base to form stable intermolecular bridged products. Reaction of sodium hydride with mono-spiro cyclophosphazene derivatives having a P-NH group, N(3)P(3)Cl(4)[O(CH(2))(3)NH], (1a) or N(3)P(3)Cl(4)[CH(3)N(CH(2))(3)NH], (1b) leads to formation of bis-cyclophosphazenes bridged with an eight-membered cyclophosphazene ring in an ansa arrangement (2a, 2b) whereas reaction of sodium hydride with mono-amino cyclophosphazene derivatives [N(3)P(3)Cl(5)(NHR), R = n-hexyl, 3a; i-Pr, 3b; Ph, 3c] give bis-cyclophosphazenes bridged with a four-membered cyclophosphazane ring in a spiro arrangement (4a-c). In the latter reaction P-O-P bridged compounds (5a-c) were also obtained as a result of hydrolysis reactions associated with the amount of moisture in the solvent tetrahydrofuran. In addition, it was found that reaction of a mixture of cyclotriphosphazene with either mono spiro compound, (1a) or (1b), in the presence of sodium hydride lead to formation of the first examples of asymmetrically-bridged cyclophosphazenes (6a-b). 相似文献
137.
Coles MP Hitchcock PB Khvostov AV Lappert MF Maron L 《Dalton transactions (Cambridge, England : 2003)》2011,40(12):3047-3052
Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis. 相似文献
138.
Nakanishi W Hayashi S Pitak MB Hursthouse MB Coles SJ 《The journal of physical chemistry. A》2011,115(42):11775-11787
The structure of 2-(2-pyridylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyridine (NSN) indicates that the molecule has a planar geometry with a linear N···S···N linkage, creating a tetracyclic structure of the formal C(2v) symmetry. To clarify the nature of the NSN σ(3c-4e) bonding, together with the related NSeN and NTeN, the dynamic and static behaviors are investigated by applying atoms-in-molecules (AIM) dual functional analysis to both the fully optimized and perturbed structures. The structures were optimized computationally, retaining C(2v) symmetry. All bond critical points are detected as expected and exhibited on both sides of the N···Z···N moiety which supports the formation of NZN σ(3c-4e). It is confirmed that N···S···N is of the covalent nature close to Me(2)S(+)-?-Cl or Me(2)Se(+)-?-Br, whereas N···Se···N and N···Te···N have the (regular) CS nature close to the CT adducts of Me(2)S(-?-Cl)(2) (TBP) and Me(2)Se-?-Br(2) (MC), respectively. An experimental high-resolution charge density determination has been performed on NSN, which thoroughly supports the theoretical results. Very similar results are obtained in the analogous pyrimidyl derivatives for N···S···N, N···Se···N, and N···Te···N. AIM dual functional analysis, as validated by experimental high-resolution charge densities, is thus confirmed to be an excellent method to elucidate the nature of these interactions. 相似文献
139.
Day BM Mansfield NE Coles MP Hitchcock PB 《Chemical communications (Cambridge, England)》2011,47(17):4995-4997
A synthetic route to magnesium guanidinate compounds that avoids ligand redistribution is reported; selected derivatives are active pre-catalysts in the dimerization of aldehydes. 相似文献
140.
Elizabeth A. Jacobs Anna Fuller Simon J. Coles Graham J. Tizzard Joseph A. Wright Simon J. Lancaster 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8647-8658
Treatment of Me2S ? B(C6F5)nH3?n (n=1 or 2) with ammonia yields the corresponding adducts. H3N ? B(C6F5)H2 dimerises in the solid state through N? H???H? B dihydrogen interactions. The adducts can be deprotonated to give lithium amidoboranes Li[NH2B(C6F5)nH3?n]. Reaction of the n=2 reagent with [Cp2ZrCl2] leads to disubstitution, but [Cp2Zr{NH2B(C6F5)2H}2] is in equilibrium with the product of β‐hydride elimination [Cp2Zr(H){NH2B(C6F5)2H}], which proves to be the major isolated solid. The analogous reaction with [Cp2HfCl2] gives a mixture of [Cp2Hf{NH2B(C6F5)2H}2] and the N? H activation product [Cp2Hf{NHB(C6F5)2H}]. [Cp2Zr{NH2B(C6F5)2H}2] ? PhMe and [Cp2Hf{NH2B(C6F5)2H}2] ? 4(thf) exhibit β‐B‐agostic chelate bonding of one of the two amidoborane ligands in the solid state. The agostic hydride is invariably coordinated to the outside of the metallocene wedge. Exceptionally, [Cp2Hf{NH2B(C6F5)2H}2] ? PhMe has a structure in which the two amidoborane ligands adopt an intermediate coordination mode, in which neither is definitively agostic. [Cp2Hf{NHB(C6F5)2H}] has a formally dianionic imidoborane ligand chelating through an agostic interaction, but the bond‐length distribution suggests a contribution from a zwitterionic amidoborane resonance structure. Treatment of the zwitterions [Cp2MMe(μ‐Me)B(C6F5)3] (M=Zr, Hf) with Li[NH2B(C6F5)nH3?n] (n=2) results in [Cp2MMe{NH2B(C6F5)2H}] complexes, for which the spectroscopic data, particularly 1J(B,H), again suggest β‐B‐agostic interactions. The reactions proceed similarly for the structurally encumbered [Cp′′2ZrMe(μ‐Me)B(C6F5)3] precursor (Cp′′=1,3‐C5H3(SiMe3)2, n=1 or 2) to give [Cp′′2ZrMe{NH2B(C6F5)nH3?n}], both of which have been structurally characterised and show chelating, agostic amidoborane coordination. In contrast, the analogous hafnium chemistry leads to the recovery of [Cp′′2HfMe2] and the formation of Li[HB(C6F5)3] through hydride abstraction. 相似文献