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1.
Artigo em Inglês | MEDLINE | ID: mdl-32369235

RESUMO

Attempted preparation of a chelated CoII ß-silylamide resulted in the unprecedented disproportionation to Co0 and a spirocyclic cobalt(IV) bis(ß-silyldiamide): [Co[(Nt Bu)2 SiMe2 ]2 ] (1). Compound 1 exhibited a room-temperature magnetic moment of 1.8 B.M. and a solid-state axial EPR spectrum diagnostic of a rare S= 1 / 2 configuration for tetrahedral CoIV . Ab initio semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (-27 kcal mol-1 ) over higher spin configurations only for the bulky tert-butyl-substituted analogue. Unlike other CoIV complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in preliminary atomic layer deposition (ALD) surface saturation experiments. The ease of synthesis and high stability make 1 an attractive starting point to investigate otherwise inaccessible CoIV intermediates and for synthesizing new materials.

2.
Inorg Chem ; 59(2): 996-1005, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31916436

RESUMO

Tin trifluoroacetates are effective vapor phase single-source precursors for F-doped SnO2, but their structures have been poorly understood for decades. Here we undertook a comprehensive structural analysis of these compounds in both the solid and gas phases through a combined single-crystal X-ray crystallography, gas phase electron diffraction, and density functional theory investigation. Tin(II) bis(trifluoroacetate) (1) thermally decomposes into a 1:1 mixture of 1 and ditin(II) µ-oxybis(µ-trifluoroacetate) (2) during sublimation, which then polymerize into hexatin(II)-di-µ3-oxyoctakis(µ-trifluoroacetate) (3) upon solidification. Reversible depolymerization occurred readily upon heating, making 3 a useful vapor phase precursor itself. Tin(IV) tetrakis(trifluoroacetate) (5) was also found to be polymeric in the solid state, but it evaporated as a monomer over 130 °C lower than 3. This counterintuitive improvement in volatility by polymerization was possibly due to the large entropy change during sublimation, which offers a strategic new design feature for vapor phase deposition precursors.

3.
Angew Chem Int Ed Engl ; 57(3): 749-754, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-29152832

RESUMO

An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs.

4.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 11): 1726-1731, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29152360

RESUMO

The syntheses and crystal structures of two isomers of phenyl iso-thia-zolyl oxa-thia-zolone, C11H6N2O2S2, are described [systematic names: 5-(3-phenyl-iso-thia-zol-5-yl)-1,3,4-oxa-thia-zol-2-one, (I), and 5-(3-phenyl-iso-thia-zol-4-yl)-1,3,4-oxa-thia-zol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) mol-ecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetra-mers linked by strong S⋯N [3.072 (2) Å] and S⋯O contacts [3.089 (1) Å]. The tetra-mers are π-stacked parallel to the a-axis direction. The single mol-ecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central iso-thia-zolyl ring and the pendant oxa-thia-zolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic iso-thia-zoloyl ring and the non-aromatic oxa-thia-zolone heterocycle. In the crystal of isomer (II), the strong S⋯O [3.020 (1) Å] and S⋯C contacts [3.299 (2) Å] and the non-planar structure of the mol-ecule lead to a form of π-stacking not observed in isomer (I) or other oxa-thia-zolone derivatives.

5.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 9): 1298-1301, 2017 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-28932459

RESUMO

The title compound, C10H7NO2S, provides the first structure of an α-alkenyl oxa-thia-zolone ring. The phenyl ring and the oxa-thia-zolone groups make dihedral angles of 0.3 (3) and -2.8 (3)°, respectively, with the plane of the central alkene group; the dihedral angle between the rings is 2.68 (8)°. A careful consideration of bond lengths provides insight into the electronic structure and reactivity of the title compound. In the crystal, extended π-stacking is observed parallel to the a-axis direction, consisting of cofacial head-to-tail dimeric units [centroid-centroid distance of 3.6191 (11) Å]. These dimeric units are separated by a slightly longer centroid-centroid distance of 3.8383 (12) Å, generating infinite stacks of mol-ecules.

6.
Angew Chem Int Ed Engl ; 56(38): 11615-11619, 2017 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-28703870

RESUMO

The synthesis of the new m-terphenyl-substituted cyclopentadienyl ligand precursor 1-cyclopentadiene-2,6-bis(2,4,6-trimethylphenyl)benzene (TerMes CpH) is described. The synthesis proceeds through the reaction of TerMes Li with cobaltocenium iodide, followed by oxidation of the intermediate cobalt(I) species to give the corresponding cyclopentadiene as a mixture of isomers. The preparation and spectroscopic properties of the alkali-metal salts (Li-Cs) is described, as well as structural information obtained by X-ray diffraction studies for the lithium, potassium, and cesium analogues. Crystallographic data demonstrate the ability of these new ligands to act as monoanionic chelates by forming metal complexes with Cp-M-Ar bonding environments.

7.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 6): 905-907, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28638656

RESUMO

The title compound, C26H38N5P, was synthesized by reacting 2-chloro-1,3-bis-(2,6-diiso-propyl-phen-yl)-1,3,2-di-aza-phospho-lidine with sodium azide and a catalytic amount of lithium chloride in tetra-hydro-furan. The title compound is the first structurally characterized 2-azido-1,3,2-di-aza-phospho-lidine and exhibits a P atom in a trigonal pyramidal geometry. The azide P-N bond length of 1.8547 (16) Šis significantly longer than the P-N separations for the chelating di-amine [P-N = 1.6680 (15) and 1.6684 (14) Å]. The sterically hindered 2,6-diiso-propyl-phenyl groups twist away from the central heterocycle, with dihedral angles between the central heteocyclic ring and benzene rings of 76.17 (10) and 79.74 (9)°. In the crystal, a weak C-H⋯N link to the terminal N atom of the azide group leads to [100] chains.

8.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 5): 735-737, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28529787

RESUMO

The title compound, C26H38ClN2OP, was synthesized by reacting phosphoryl chloride with N,N'-bis-(2,6-diiso-propyl-phen-yl)ethane-1,2-di-amine in the presence of N-methyl-morpholine which acted as an auxilliary base to quench the HCl released as a by-product. The resultant N-heterocyclic phosphine five-membered ring adopts a half-chair conformation and features a tetra-coordinate P atom ligated by the chelating di-amine [P-N = 1.6348 (14) and 1.6192 (14) Å], one double-bonded O atom [P1-O1 = 1.4652 (12) Å] and one Cl atom [P1-Cl1 = 2.0592 (7) Å]. The sterically hindered 2,6-diiso-propyl-phenyl (Dipp) groups twist away from the central heterocycle, with torsion angles of -75.66 (19) and 83.39 (19)° for the P-N-Car-Car links. A number of intra-molecular C-H⋯N, C-H⋯O and C-H⋯Cl close contacts occur. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds to generate [010] chains. C-H⋯π inter-actions are also observed.

9.
Acta Crystallogr E Crystallogr Commun ; 72(Pt 10): 1471-1474, 2016 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-27746944

RESUMO

The title compound, C27H38ClN2+·C32H12BF24-, was synthesized by reacting the product formed from a previous reaction between 1,3-bis-(2,6-diiso-propyl-phen-yl)imidazolinium-2-carboxyl-ate (SIPrCO2), and SOCl2, with sodium tetra-kis-[3,5-bis-(tri-fluoro-meth-yl)phen-yl]borate (NaBARF). In the cation, the imidazole ring is in a half-chair conformation and the formerly carbene carbon atom is bonded in a distorted trigonal-planar geometry with N-C-Cl angles of 122.96 (16) and 122.21 (16)° and an N-C-N angle of 114.83 (18)°. In the crystal, weak C-H⋯F hydrogen bonds link the cations and anions, forming a three-dimensional network. In addition, a short Cl⋯F contact of 3.213 Šand several short F⋯F contacts less than the sum of the van der Waals radii [1.47 Š+ 1.47 Š= 2.94 Å] are observed. The F atoms of two of the CF3 groups were refined as disordered over four sets of sites.

10.
Dalton Trans ; 45(32): 12636-8, 2016 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-27443569

RESUMO

The persistent phosphinyl radical, (H2C)2(NDipp)2P˙, formed upon dissolution from the homolytic cleavage of the P-P bond in the diphosphane [(H2C)2(NDipp)2P]2, was reacted with carbon disulfide, phenyl isocyanate, and phenyl isothiocyanate. The phosphinyl fragments add across the C[double bond, length as m-dash]S or C[double bond, length as m-dash]O double bond to give neutral, diamagnetic species.

11.
Dalton Trans ; 45(5): 2102-15, 2016 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-26485276

RESUMO

Metal(0) complexes L(Cr,Mo,W)(CO)5 have been prepared from 1,3-bis(2,6-diisopropylphenyl)-2-(4-methylphenyl)-3-aza-1(λ(3),σ(2))-phosphapropene and 1,3-bis(2,6-diisopropylphenyl)-2-(4-methoxyphenyl)-3-aza-1(λ(3),σ(2))-phosphapropene using standard methods. Full characterization of four products and crystal structures of these complexes as well as the methoxyphenyl-phosphapropene are reported. The ligands coordinate κP, common for simple phosphaalkenes, despite the strongly-perturbing amino substitution at the double bond C atoms. Analyses of the NMR and vibrational spectroscopic data reveal that the complexes have very similar character to similarly-coordinated phosphaalkenes, with strong σ-donor character. The presence of some net π-interactions (acceptor or donor) is indicated by structures in which the ligands coordinate fully eclipsed with the M-CO groups. The synthetic and structural results have been augmented by B3PW91/LANL2DZ calculations that reproduce the structures of the Cr complexes accurately. The calculated vibrational spectra are used to confirm the assignment of the ν(C ≡ O) vibrational data. Detailed orbital interaction diagrams based on DFT calculations are reported for the title complexes as well as for the Cr(CO)5 complex of Mes-P=CPh2. The electronic absorption spectra of the title complexes have intense low-energy absorptions ranging from 24,500 to 25,300 cm(-1), which can be interpreted qualitatively using the DFT results.

12.
J Am Chem Soc ; 135(30): 11205-15, 2013 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-23808375

RESUMO

Activation barriers to the electrochemical oxidation for the series PPh3-n(dipp)n (dipp = 2,6-diisopropylphenyl) in CH2Cl2/Bu4NPF6 were measured using large amplitude FT ac voltammetry. Increasing substitution across this series, which offers the widest range of steric requirements across any analogous series of triarylphosphines reported to date, increases the energetic barrier to electron transfer; values of 18, 24, and 25 kJ mol(-1) were found for compounds with n = 1, 2, and 3, respectively. These values are significantly greater than those calculated for outer sphere activation barriers, with deviations between observed and calculated values increasing with the number of dipp ligands. This suggests that the steric congestion afforded by these bulky substituents imposes significant reorganizational energy on the electron transfer processes. This is the first investigation of the effect of sterics on the kinetics of heterogeneous electron transfer across a structurally homologous series. Increased alkyl substitution across the series also increases the chemical reversibility of the oxidations and decreases the oxidation peak potentials. As the compounds for which n = 1 and 2 are novel, the synthetic strategies employed in their preparation are described, along with their full spectroscopic, physical, and crystallographic characterization. Optimal synthesis when n = 1 is via a Grignard reagent, whereas when n = 2 an aryl copper reagent must be employed, as use of a Grignard results in reductive coupling. Chemical oxidation studies were performed to augment the electrochemical work; the O, S, and Se oxidation products for the parent triarylphosphines for which n = 1 and 2 were isolated and characterized.

14.
Inorg Chem ; 51(21): 11837-50, 2012 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-23098074

RESUMO

A new, easily synthesized diphosphine based on a heterocyclic 1,3,2-diazaphospholidine framework has been prepared. Due to the large, sterically encumbering Dipp groups (Dipp = 2,6-diisopropylphenyl) on the heterocyclic ring, the diphosphine undergoes homolytic cleavage of the P-P bond in solution to form two phosphinyl radicals. The diphosphine has been reacted with O(2), S(8), Se, Te, and P(4), giving products that involve insertion of elements between the P-P bond to yield the related phosphinic acid anhydride, sulfide/disulfide, selenide, telluride, and a butterfly-type perphospha-bicyclobutadiene structure with a trans,trans-geometry. All molecules have been characterized by multinuclear NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Variable-temperature EPR spectroscopy was utilized to study the nature of the phosphinyl radical in solution. Electronic structure calculations were performed on a number of systems from the parent diphosphine [H(2)P](2) to amino-substituted [(H(2)N)(2)P](2) and cyclic amino-substituted [(H(2)C)(2)(NH)(2)P](2); then, bulky substituents (Ph or Dipp) were attached to the cyclic amino systems. Calculations on the isolated diphosphine at the B3LYP/6-31+G* level show that the homolytic cleavage of the P-P bond to form two phosphinyl radicals is favored over the diphosphine by ~11 kJ/mol. Furthermore, there is a significant amount of relaxation energy stored in the ligands (52.3 kJ/mol), providing a major driving force behind the homolytic cleavage of the central P-P bond.

15.
Acta Crystallogr C ; 67(Pt 12): m391-4, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22138916

RESUMO

In the complex salt [η(6)-1-chloro-2-(pyrrolidin-1-yl)benzene](η(5)-cyclopentadienyl)iron(II) hexafluoridophosphate, [Fe(C(5)H(5))(C(10)H(12)ClN)]PF(6), (I), the complexed cyclopentadienyl and benzene rings are almost parallel, with a dihedral angle between their planes of 2.3 (3)°. In a related complex salt, (η(5)-cyclopentadienyl){2-[η(6)-2-(pyrrolidin-1-yl)phenyl]phenol}iron(II) hexafluoridophosphate, [Fe(C(5)H(5))(C(16)H(17)NO)]PF(6), (II), the analogous angle is 5.4 (1)°. In both complexes, the aromatic C atom bound to the pyrrolidine N atom is located out of the plane defined by the remaining five ring C atoms. The dihedral angles between the plane of these five ring atoms and a plane defined by the N-bound aromatic C atom and two neighboring C atoms are 9.7 (8) and 5.6 (2)° for (I) and (II), respectively.

16.
Acta Crystallogr C ; 67(Pt 11): m351-4, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22051951

RESUMO

In the structure of the title complex salt, [Fe(C(5)H(5))(C(12)H(8)O(3)S)]PF(6), the coordinated cyclopentadienyl (Cp) and benzene ring planes are almost parallel, with a hinge angle between the planes of 0.8 (2)°. The hinge angle between the planes of the peripheral (coordinated and uncoordinated) benzene rings in the coordinated phenoxathiin 10,10-dioxide molecule is 169.9 (2)°, and the FeCp moiety is located inside the shallow fold of the heterocycle. The hinge angle between the benzene ring planes in the free heterocycle, C(12)H(8)O(3)S, is 171.49 (6)°.

17.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 10): o2731, 2011 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22064822

RESUMO

The title compound, C(17)H(26)O, is a di-ortho-alkyl substituted phenyl ethanone that exhibits a significant twisting of the ketone fragment relative to the aromatic ring [O-C-C-C torsion angle = 89.32 (17)°] due to steric pressure from the ortho-isopropyl groups. One ortho- and the para-isopropyl group exhibit orientational disorder with a refined site occupancy factor of 0.562 (3):0.438 (3).

18.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m895-6, 2011 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-21836885

RESUMO

In the title compound, [Mo(C(37)H(53)N(3))(CO)(3)], the Mo atom to ring-centroid distance in the η(6)-coordinated tricarbonyl-molybdenum group is 1.958 (1) Å. The three C O groups are pseudo-octa-hedrally disposed with C-Mo-C angles ranging from 80.7 (1) to 87.4 (1)°. The two uncoordinated 2,6-diisopropyl-phenyl-substituted benzene rings form dihedral angles of 75.96 (8) and 78.01 (9)° with the mean plane of the guanidine group. The coordinated benzene ring is in a slight sofa conformation with the N-substituted C atom and the bonded N atom dispaced by 0.090 (3) and 0.458 (4) Å, respectively, from the mean plane of the remaining ring atoms. In the crystal, despite there being two N-H donor groups, no conventional hydrogen bonds are present. This may be because of the steric effects of the bulky diisopropyl-phenyl groups.

19.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 5): o1054, 2011 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-21754381

RESUMO

The asymmetric unit of a second polymorph of the title compound, C(9)H(4)F(6)O(2), contains five independent mol-ecules, which form hydrogen-bonded O-H⋯O dimers about inversion centers. The most significant structural difference between this structure and that of the first polymorph [Tobin & Masuda (2009 ▶). Acta Cryst. E65, o1217] is the hydrogen-bonded, dimeric orientation of the carb-oxy-lic acid functionalities.

20.
Org Biomol Chem ; 9(10): 3672-80, 2011 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-21472176

RESUMO

In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC(6)H(2)(CH(3))(3)](2)C···HO(NC(5)H(6)(CH(3))(4)), IMes···TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH(2)Ni-Pr(2)C(6)H(3)](2)CH···O(NC(5)H(6)(CH(3))(4)). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N-[2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph(3)PC(H)C(=O)O(NC(5)H(6)(CH(3))(4)). A full characterization of the product, including an X-ray crystal structure, is described.

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