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1.
Inorg Chem ; 57(23): 14983-15000, 2018 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-30444604

RESUMO

Eight M(H2O) n(Z) salt hydrates were characterized by single-crystal X-ray diffraction (Z2- = B12F122-): M = Ca, Sr, n = 7; M = Mg, Co, Ni, Zn, n = 6; M = Ba, n = 4, 5. Weak O-H···F hydrogen bonding between the M(H2O) n2+ cations and Z2- resulted in room-temperature Fourier transform infrared (FTIR) spectra having sharp ν(OH) bands, with full widths at half max of 10-30 cm-1, which are much more narrow than ν(OH) bands in room temperature FTIR spectra of most salt hydrates. Clearly resolved νasym(OH/OD) and νsym(OH/OD) bands with Δν(OH) as small as 17 cm-1 and Δν(OD) as small as 11 cm-1 were observed (Δν(OX) = νasym(OX) - νsym(OX)). The isomorphic hexahydrates ( R3̅) have two fac-(H2O)3 sets of H2O ligands and nearly octahedral coordination spheres. They exhibited four resolvable ν(OH) bands, one νasym(OH)/νsym(OH) pair for H2O ligands with longer O(H)···F distances and one νasym(OH)/νsym(OH) pair for H2O ligands with shorter O(H)···F distances. The ν(OH) bands for the three H2O molecules with shorter, slightly stronger O(H)···F hydrogen bonds were broader, more intense, and red-shifted by ca. 25 cm-1 relative to the bands for the three other H2O molecules, the first time that such small differences in relatively weak O(H)···F hydrogen bonds in the same crystalline hexahydrate have resulted in observable IR spectroscopic differences at room temperature. For the first time room temperature ν(OH) values for salt hexahydrates showed the monotonic progression Mg2+ > Co2+ > Ni2+ > Zn2+, essentially the same progression as the p Ka values for these metal ions in aqueous solution. A further manifestation of the weak O-H···F hydrogen bonding in these hydrates is the latent porosity exhibited by Ba(H2O)5,8(Z), Sr(H2O) n,m(Z), and Ca(H2O)4,6(Z). Finally, the H2O/D2O exchange reaction Co(D2O)6(Z) → Co(H2O)6(Z) was ca. 50% complete in 1 h at 50 °C in N2/17 Torr H2O( g).

2.
Chem Sci ; 9(9): 2601-2608, 2018 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-29675252

RESUMO

In this work, we introduce a novel approach for the selective assembly of heterometallic complexes by unprecedented coordination of coinage metal cations to strained single ruthenium-boron bonds on a surface of icosahedral boron clusters. M(i) cations (M = Cu, Ag, and Au) insert into B-Ru bonds of the (BB)-carboryne complex of ruthenium with the formation of four-membered B-M-Ru-B metalacycles. Results of theoretical calculations suggest that bonding within these metalacycles can be best described as unusual three-center-two-electron B-M···Ru interactions that are isolobal to B-H···Ru borane coordination for M = Cu and Ag, or the pairs of two-center-two electron B-Au and Au-Ru interactions for M = Au. These transformations comprise the first synthetic route to exohedral coinage metal boryl complexes of icosahedral closo-{C2B10} clusters, which feature short Cu-B (2.029(2) Å) and Ag-B (2.182(3) Å) bonds and the shortest Au-B bond (2.027(2) Å) reported to date. The reported heterometallic complexes contain Cu(i) and Au(i) centers in uncharacteristic square-planar coordination environments. These findings pave the way to rational construction of a broader class of multimetallic architectures featuring M-B bonds.

3.
Chem Sci ; 8(8): 5399-5407, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28970919

RESUMO

In this work, we introduce a novel concept of a borane group vicinal to a metal boryl bond acting as a supporting hemilabile ligand in exohedrally metalated three-dimensional carborane clusters. The (POBOP)Ru(Cl)(PPh3) pincer complex (POBOP = 1,7-OP(i-Pr)2-m-2-carboranyl) features extreme distortion of the two-center-two-electron Ru-B bond due to the presence of a strong three-center-two-electron B-H···Ru vicinal interaction. Replacement of the chloride ligand with a hydride afforded the (POBOP)Ru(H)(PPh3) pincer complex, which possesses B-Ru, B-H···Ru, and Ru-H bonds. This complex was found to exhibit a rapid exchange between hydrogen atoms of the borane and the terminal hydride through metal center shuttling between two boron atoms of the carborane cage. This exchange process, which involves sequential cleavage and formation of strong covalent metal-boron and metal-hydrogen bonds, is unexpectedly facile at temperatures above -50 °C corresponding to an activation barrier of 12.2 kcal mol-1. Theoretical calculations suggested two equally probable pathways for the exchange process through formally Ru(0) or Ru(iv) intermediates, respectively. The presence of this hemilabile vicinal B-H···Ru interaction in (POBOP)Ru(H)(PPh3) was found to stabilize a latent coordination site at the metal center promoting efficient catalytic transfer dehydrogenation of cyclooctane under nitrogen and air at 170 °C.

4.
Inorg Chem ; 56(19): 12023-12041, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-28933828

RESUMO

Structures of the alkali-metal hydrates Li2(H2O)4Z, LiK(H2O)4Z, Na2(H2O)3Z, and Rb2(H2O)2Z, unit cell parameters for Rb2Z and Rb2(H2O)2Z, and the density functional theory (DFT)-optimized structures of K2Z, K2(H2O)2Z, Rb2Z, Rb2(H2O)2Z, Cs2Z, and Cs2(H2O)Z are reported (Z2- = B12F122-) and compared with previously reported X-ray structures of Na2(H2O)0,4Z, K2(H2O)0,2,4Z, and Cs2(H2O)Z. Unusually rapid room-temperature hydration/dehydration cycles of several M2Z/M2(H2O)nZ salt hydrate pairs, which were studied by isothermal gravimetry, are also reported. Finely ground samples of K2Z, Rb2Z, and Cs2Z, which are not microporous, exhibited latent porosity by undergoing hydration at 24-25 °C in the presence of 18 Torr of H2O(g) to K2(H2O)2Z, Rb2(H2O)2Z, and Cs2(H2O)Z in 18, 40, and 16 min, respectively. These hydrates were dehydrated at 24-25 °C in dry N2 to the original anhydrous M2Z compounds in 61, 25, and 76 min, respectively (the exact times varied from sample to sample depending on the particle size). The hydrate Na2(H2O)2Z also exhibited latent porosity by undergoing multiple 90 min cycles of hydration to Na2(H2O)3Z and dehydration back to Na2(H2O)2Z at 23 °C. For the K2Z, Rb2Z, and Cs2Z transformations, the maximum rate of hydration (rhmax) decreased, and the absolute value of the maximum rate of dehydration (rdmax) increased, as T increased. For K2Z ↔ K2(H2O)2Z hydration/dehydration cycles with the same sample, the ratio rhmax/rdmax decreased 26 times over 8.6 °C, from 3.7 at 23.4 °C to 0.14 at 32.0 °C. For Rb2Z ↔ Rb2(H2O)2Z cycles, rhmax/rdmax decreased from 0.88 at 23 °C to 0.23 at 27 °C. For Cs2Z ↔ Cs2(H2O)Z cycles, rhmax/rdmax decreased 20 times over 8 °C, from 6.7 at 24 °C to 0.34 at 32 °C. In addition, the reversible substitution of D2O for H2O in fully hydrated Rb2(H2O)2Z in the presence of N2/16 Torr of D2O(g) was complete in only 60 min at 23 °C.

5.
Inorg Chem ; 56(19): 11798-11803, 2017 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-28902998

RESUMO

A new pathway of activation of C-H bonds of alkyl- and arylnitriles by a cooperative action of TaCl5 and PPh3 under mild conditions is reported. Coordination of nitriles to the highly Lewis acidic Ta(V) center resulted in an activation of their aliphatic and aromatic C-H bonds, allowing nucleophilic attack and deprotonation by the relatively weak base PPh3. The propensity of Ta(V) to form multiple bonds to nitrogen-containing ligands is an important driving force of the reaction as it led to a sequence of bond rearrangements and the emergence of, in the case of benzonitrile, a zwitterionic enediimido complex of Ta(V) through C═C double bond formation between two activated nitrile fragments. These transformations highlight the special role of the high-valent transition metal halide in substrate activation and distinguish the reactivity of the TaCl5-PPh3 system from both non-metal- and late transition metal-based frustrated Lewis pairs.

6.
Inorg Chem ; 56(8): 4369-4379, 2017 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-28383911

RESUMO

The synthesis of high-purity Na2B12F12 and the crystal structures of Na2(B12F12) (5 K neutron powder diffraction (NPD)), Na2(H2O)4(B12F12) (120 K single-crystal X-ray diffraction (SC-XRD)), Na2(B12Cl12) (5 and 295 K NPD), and Na2(H2O)6(B12Cl12) (100 K SC-XRD) are reported. The compound Na2(H2O)4(B12F12) contains {[(Na(µ-H2O)2Na(µ-H2O)2)]2+}∞ infinite chains; the compound Na2(H2O)6(B12Cl12) contains discrete [(H2O)2Na(µ-H2O)2Na(H2O)2]2+ cations with OH···O hydrogen bonds linking the terminal H2O ligands. The structures of the two hydrates and the previously published structure of Na2(H2O)4(B12H12) are analyzed with respect to the relative coordinating ability of B12F122-, B12H122-, and B12Cl122- toward Na+ ions in the solid state (i.e., the relative ability of these anions to satisfy the valence of Na+). All three hydrated structures have distorted octahedral NaX2(H2O)4 coordination spheres (X = F, H, Cl). The sums of the four Na-O bond valence contributions are 71, 75, and 89% of the total bond valences for the X = F, H, and Cl hydrated compounds, respectively, demonstrating that the relative coordinating ability by this criterion is B12Cl122- ≪ B12H122- < B12F122-. Differential scanning calorimetry experiments demonstrate that Na2(B12F12) undergoes a reversible, presumably order-disorder, phase transition at ca. 560 K (287 °C), between the 529 and 730 K transition temperatures previously reported for Na2(B12H12) and Na2(B12Cl12), respectively. Thermogravimetric analysis demonstrates that Na2(H2O)4(B12F12) and Na2(H2O)6(B12Cl12) undergo partial dehydration at 25 °C to Na2(H2O)2(B12F12) and Na2(H2O)2(B12Cl12) in ca. 30 min and 2 h, respectively, and essentially complete dehydration to Na2(B12F12) and Na2(B12Cl12) within minutes at 150 and 75 °C, respectively (the remaining trace amounts of H2O, if any, were not quantified). The changes in structure upon dehydration and the different vapor pressures of H2O needed to fully hydrate the respective Na2(B12X12) compounds provide additional evidence that B12Cl122- is more weakly coordinating than B12F122- to Na+ in the solid state. Taken together, the results suggest that the anhydrous, halogenated closo-borane compounds Na2(B12F12) and Na2(B12Cl12), in appropriately modified forms, may be viable component materials for fast-ion-conducting solid electrolytes in future energy-storage devices.

7.
Inorg Chem ; 56(7): 4072-4083, 2017 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-28333460

RESUMO

The single-crystal X-ray structures, thermogravimetric analyses, and/or FTIR spectra of a series of salts of the B12F122- anion and homoleptic Ag(L)n+ cations are reported (L = CH2Cl2, n = 2; L = PhCH3, n = 3; L = CH3CN; n = 2-4; L = CO, n = 1, 2). The superweak-anion nature of B12F122- (Y2-) was demonstrated by the rapid reaction of microcrystalline Ag2(Y) with 1 atm of CO to form a nonclassical silver(I) carbonyl compound with an FTIR ν(CO) band at 2198 cm-1 (and with the proposed formula [Ag(CO)n]2[Y]). In contrast, microcrystalline Ag2(B12Cl12) did not exhibit ν(CO) bands and therefore did not form Ag(CO)+ species, even after 32 h under 24 atm of CO. When Ag2(Y) was treated with carbon monoxide pressures higher than 1 atm, a new ν(CO) band at 2190 cm-1 appeared, which is characteristic of a Ag(CO)2+ dicarbonyl cation. Both Ag2(CH3CN)8(Y) and Ag2(CH3CN)5(Y) rapidly lost coordinated CH3CN at 25 °C to form Ag2(CH3CN)4(Y), which formed solvent-free Ag2(Y) only after heating above 100 °C. Similarly, Ag2(PhCH3)6(Y) rapidly lost coordinated PhCH3 at 25 °C to form Ag2(PhCH3)2(Y), which formed Ag2(Y) after heating above 150 °C, and Ag2(CH2Cl2)4(Y) rapidly lost three of the four coordinated CH2Cl2 ligands between 25 and 100 °C and formed Ag2(Y) when it was heated above 200 °C. Solvent-free Ag2(Y) was stable until it was heated above 380 °C. The rapid evaporative loss of coordinated ligands at 25 °C from nonporous crystalline solids requires equally rapid structural reorganization of the lattice and is one of three manifestations of the structural compliance of the Y2- anion reported in this work. The second, more quantitative, manifestation is that Ag+ bond-valence sums for Ag2(CH3CN)n(Y) are virtually constant, 1.20 ± 0.03, for n = 8, 5, 4, because the Y2- anion precisely compensated for the lost CH3CN ligands by readily forming the necessary number of weak Ag-F(B) bonds. The third, and most exceptional, manifestation is that the idealized structural reorganization accompanying the conceptual transformations Ag2(CH3CN)8(Y) → Ag2(CH3CN)5(Y) → Ag2(CH3CN)4(Y) involve close-packed layers of Y2- anions that sandwich the Ag(CH3CN)4+ complexes splitting into staggered flat ribbons of interconnected (Y2-)3 triangles that surround the Ag2(CH3CN)52+ complexes on four sides, conceptually re-forming close-packed layers of anions that sandwich the Ag(CH3CN)2+ complexes. The interconnected (Y2-)3 triangle lattice of anions in Ag2(CH3CN)5(Y) may be the first example of this structure type.

8.
Inorg Chem ; 55(23): 12254-12262, 2016 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-27934406

RESUMO

The structures of three solvated monovalent cation salts of the superweak anion B12F122- (Y2-), K2(SO2)6Y, Ag2(SO2)6Y, and Ag2(H2O)4Y, are reported and discussed with respect to previously reported structures of Ag+ and K+ with other weakly coordinating anions. The structures of K2(SO2)6Y and Ag2(SO2)6Y are isomorphous and are based on expanded cubic close-packed arrays of Y2- anions with M(OSO)6+ complexes centered in the trigonal holes of one expanded close-packed layer of B12 centroids (⊙). The K+ and Ag+ ions have virtually identical bicapped trigonal prism MO6F2 coordination spheres, with M-O distances of 2.735(1)-3.032(2) Å for the potassium salt and 2.526(5)-2.790(5) Å for the silver salt. Each M(OSO)6+ complex is connected to three other cationic complexes through their six µ-SO2-κ1O,κ2O' ligands. The structure of Ag2(H2O)4Y is unique [different from that of K2(H2O)4Y]. Planes of close-packed arrays of anions are offset from neighboring planes along only one of the linear ⊙···âŠ™···âŠ™ directions of the close-packed arrays, with [Ag(µ-H2O)2Ag(µ-H2O)2)]∞ infinite chains between the planes of anions. There are two nearly identical AgO4F2 coordination spheres, with Ag-O distances of 2.371(5)-2.524(5) Å and Ag-F distances of 2.734(4)-2.751(4) Å. This is only the second structurally characterized compound with four H2O molecules coordinated to a Ag+ ion in the solid state. Comparisons with crystalline H2O and SO2 solvates of other Ag+ and K+ salts of weakly coordinating anions show that (i) N[(SO2)2(1,2-C6H4)]-, BF4-, SbF6-, and Al(OC(CF3)3)4- coordinate much more strongly to Ag+ than does Y2-, (ii) SnF62- coordinates somewhat more strongly to K+ than does Y2-, and (iii) B12Cl122- coordinates to K+ about the same as, if not slightly weaker than, Y2-.

9.
Chem Commun (Camb) ; 52(86): 12710-12713, 2016 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-27722276

RESUMO

The activation of O-H bonds of water at room temperature driven by the cage-opening rearrangement of a biscarborane-based cluster is reported. The reaction of the 12-vertex-closo-12-vertex-nido biscarborane cluster with water led to the quantitative and selective two-vertex decapitation of a carborane cluster and formation of the pendent boronic acid hydride B(H)(OH) group. Remarkably, this transformation can be quantitatively reversed with the release of water and re-formation of the starting biscarborane cage. The flexibility of cage decapitation/expansion and its influence on the reactivity of an exohedral substituent represent a new approach to cluster-induced organic transformations.

10.
J Am Chem Soc ; 138(33): 10531-8, 2016 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-27526855

RESUMO

The first example of a transition metal (BB)-carboryne complex containing two boron atoms of the icosahedral cage connected to a single exohedral metal center (POBBOP)Ru(CO)2 (POBBOP = 1,7-OP(i-Pr)2-2,6-dehydro-m-carborane) was synthesized by double B-H activation within the strained m-carboranyl pincer framework. Theoretical calculations revealed that the unique three-membered (BB)>Ru metalacycle is formed by two bent B-Ru σ-bonds with the concomitant increase of the bond order between the two metalated boron atoms. The reactivity of the highly strained electron-rich (BB)-carboryne fragment with small molecules was probed by reactions with electrophiles. The carboryne-carboranyl transformations reported herein represent a new mode of cooperative metal-ligand reactivity of boron-based complexes.

11.
Inorg Chem ; 55(16): 8207-13, 2016 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-27487332

RESUMO

The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)9[µ3-η(3)-C2B10H9(SCH3)](µ-H)2, 1, by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster and the coordination of the sulfur atom and the activation of two B-H bonds with transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(µ-H)[(µ3-η(3)-1,4,5-µ3-η(3)-6,10,11-C2B10H8S(CH3)]Os3(CO)9(µ-H)2, 2, that contains two triosmium triangles attached to the same carborane cage. The carborane cage was opened by cleavage of two B-C bonds and one B-B bond. The B-H group that was pulled out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B-B bonds. When heated to 150 °C, 2 was transformed into the complex Os3(CO)9(µ-H)[(µ3-η(3)-µ3-η(3)-C2B10H7S(CH3)]Os3(CO)9(µ-H), 3, by the loss of two hydrogen atoms and a rearrangement that led to further opening of the carborane cage. Reaction of 1 with a second equivalent of closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)6)(µ3-η(3)-C2B10H9-R-SCH3) (µ3-η(3)-C2B10H10-S-SCH3)(µ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound Os3(CO)6(µ3-η(3)-C2B10H9-R-SCH3)(µ3-η(3)-C2B10H10-R-SCH3)(µ-H)3, 4b, by an inversion of stereochemistry at one of the sulfur atoms by heating to 174 °C.

12.
Inorg Chem ; 55(11): 5101-3, 2016 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-27172115

RESUMO

We report a new CH3CN activation mode where an imido group is directly formed by deprotonation of the nitrile coordinated to the highly Lewis acidic Ta(V) center. The unexpected deprotonation of TaCl5(CH3CN) by NEt3 resulted in isolation of the triethylammonium vinylimido complex [HNEt3][Ta(NC(CH2)NEt3)Cl5]. The reaction is proposed to proceed through rearrangement of the initial nucleophilic carbanion to the electrophilic azaallene/carbocation intermediate. The use of more sterically hindered (i-Pr)CN and weakly nucleophilic N(i-Pr)2Et resulted in the isolation of a vinylimido group formed upon dimerization of deprotonated nitriles, suggesting deprotonation as the first step of the transformation.

13.
Chemistry ; 22(20): 6764-7, 2016 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-26990216

RESUMO

An unusual 12-vertex-closo-C2 B10 /12-vertex-nido-C2 B10 biscarborane cluster was synthesized through an unprecedented regioselective metal-free B-H activation by a sterically hindered P(III) center under mild conditions accompanied by cage-opening rearrangement. A combination of the electron-accepting properties of a carborane cage and steric enforcement of close interatomic contacts represent a new synthetic strategy for the activation of strong B-H bonds in carboranes.

14.
Chemistry ; 22(19): 6501-4, 2016 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-26971388

RESUMO

The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers Os3 (CO)9 (µ3 -4,5,9-C2 B10 H8 )(µ-H)2 (1 a) and Os3 (CO)9 (µ3 -3,4,8-C2 B10 H8 )(µ-H)2 (1 b) formed by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster. Two BH bonds of the o-C2 B10 H10 were activated in its addition to the osmium cluster. A second triosmium cluster was added to the 1 a/1 b mixture to yield the complex Os3 (CO)9 (µ-H)2 (µ3 -4,5,9-µ3 -7,11,12-C2 B10 H7 )Os3 (CO)9 (µ-H)3 (2) that contains two triosmium triangles attached to the same carborane cage. When heated, 2 was transformed to the complex Os3 (CO)9 (µ-H)(µ3 -3,4,8-µ3 -7,11,12-C2 B10 H8 )Os3 (CO)9 (µ-H) (3) by a novel opening of the carborane cage with loss of H2 .

15.
J Am Chem Soc ; 135(51): 19068-70, 2013 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-24304004

RESUMO

Grafting (ArO)2W(═O)(═CHtBu) (ArO = 2,6-mesitylphenoxide) on partially dehydroxylated silica forms mostly [(≡SiO)W(═O)(═CHtBu)(OAr)] along with minor amounts of [(≡SiO)W(═O)(CH2tBu)(OAr)2] (20%), both fully characterized by elemental analysis and IR and NMR spectroscopies. The well-defined oxo alkylidene surface complex [(≡SiO)W(═O)(═CHtBu)OAr] is among the most active heterogeneous metathesis catalysts reported to date in the self-metathesis of cis-4-nonene and ethyl oleate, in sharp contrast to the classical heterogeneous catalysts based on WO3/SiO2.

16.
J Am Chem Soc ; 135(41): 15338-41, 2013 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-24074292

RESUMO

A substituted TREN has been prepared in which the aryl groups in (ArylNHCH2CH2)3N are substituted at the 3- and 5-positions with a total of six OCH2(CH2)nCH═CH2 groups (n = 1, 2, 3). Molybdenum nitride complexes, [(ArylNCH2CH2)3N]Mo(N), have been isolated as adducts that contain B(C6F5)3 bound to the nitride. Two of these [(ArylNCH2CH2)3N]Mo(NB(C6F5)3) complexes (n = 1 and 3) were crystallographically characterized. After removal of the borane from [(ArylNCH2CH2)3N]Mo(NB(C6F5)3) with PMe3, ring-closing olefin metathesis (RCM) was employed to join the aryl rings with OCH2(CH2)nCH═CH(CH2)nCH2O links (n = 1-3) between them. RCM worked best with a W(O)(CHCMe3)(Me2Pyr)(OHMT)(PMe2Ph) catalyst (OHMT = hexamethylterphenoxide, Me2Pyr = 2,5-dimethylpyrrolide) and n = 3. The macrocyclic ligand was removed from the metal through hydrolysis and isolated in 70-75% yields relative to the borane adducts. Crystallographic characterization showed that the macrocyclic TREN ligand in which n = 3 contains three cis double bonds. Hydrogenation produced a TREN in which the three links are saturated, i.e., O(CH2)10O.

17.
J Am Chem Soc ; 133(51): 20754-7, 2011 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-22107254

RESUMO

Addition of LiOHMT (OHMT = O-2,6-dimesitylphenoxide) to W(O)(CH-t-Bu)(PMe(2)Ph)(2)Cl(2) led to WO(CH-t-Bu)Cl(OHMT)(PMe(2)Ph) (4). Subsequent addition of Li(2,5-Me(2)C(4)H(2)N) to 4 yielded yellow W(O)(CH-t-Bu)(OHMT)(Me(2)Pyr)(PMe(2)Ph) (5). Compound 5 is a highly effective catalyst for the Z-selective coupling of selected terminal olefins (at 0.2% loading) to give product in >75% yield with >99% Z configuration. Addition of 2 equiv of B(C(6)F(5))(3) to 5 afforded a catalyst activated at the oxo ligand by B(C(6)F(5))(3). 5·B(C(6)F(5))(3) is a highly active catalyst that produces thermodynamic products (~20% Z).


Assuntos
Alcenos/química , Complexos de Coordenação/química , Tungstênio/química , Catálise , Conformação Molecular
18.
J Am Chem Soc ; 133(8): 2672-90, 2011 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-21294511

RESUMO

A family of highly stable (poly)perfluoroalkylated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, (19)F NMR, UV-vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc(3)N@C(80)(CF(3))(10) and Sc(3)N@C(80)(CF(3))(12,) single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ((19)F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc(3)N@C(80)(CF(3))(n) (n = 2-16). Electrochemical studies revealed that Sc(3)N@C(80)(CF(3))(n) derivatives are easier to reduce than Sc(3)N@C(80), the shift of E(1/2) potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc(3)N@C(80)(CF(3))(n) were generated in solution and characterized by ESR spectroscopy, revealing their (45)Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc(3)N@C(80) making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance.


Assuntos
Fluorcarbonetos/química , Fulerenos/química , Nitrilos/química , Polímeros/química , Escândio/química , Alquilação , Ânions/química , Cristalografia por Raios X , Radicais Livres/química , Modelos Moleculares
19.
Chem Commun (Camb) ; 47(3): 875-7, 2011 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-21063613

RESUMO

High-temperature syntheses of the new C(60)(i-C(3)F(7))(2,4,6) and C(70)(i-C(3)F(7))(2,4) isomers and their characterization by spectroscopic methods, X-ray crystallography, cyclic voltammetry and density functional theory provide compelling evidence that they are superior electron acceptors than trifluoromethylfullerenes.

20.
J Am Chem Soc ; 132(39): 13902-13, 2010 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-20831168

RESUMO

Structures of K(2)(H(2)O)(2)B(12)F(12) and K(2)(H(2)O)(4)B(12)F(12) were determined by X-ray diffraction. They contain [K(µ-H(2)O)(2)K](2+) and [(H(2)O)K(µ-H(2)O)(2)K(H(2)O)](2+) dimers, respectively, which interact with superweak B(12)F(12)(2-) anions via multiple K···F(B) interactions and (O)H···F(B) hydrogen bonds (the dimers in K(2)(H(2)O)(4)B(12)F(12) are also linked by (O)H···O hydrogen bonds). DFT calculations show that both dimers are thermodynamically stabilized by the lattice of anions: the predicted ΔE values for the gas-phase dimerization of two K(H(2)O)(+) or K(H(2)O)(2)(+) cations into [K(µ-H(2)O)(2)K](2+) or [(H(2)O)K(µ-H(2)O)(2)K(H(2)O)](2+) are +232 and +205 kJ mol(-1), respectively. The calculations also predict that ΔE for the gas-phase reaction 2 K(+) + 2 H(2)O → [K(µ-H(2)O)(2)K](2+) is +81.0 kJ mol, whereas ΔH for the reversible reaction K(2)B(12)F(12 (s)) + 2 H(2)O((g)) → K(2)(H(2)O)(2)B(12)F(12 (s)) was found to be -111 kJ mol(-1) by differential scanning calorimetry. The K(2)(H(2)O)(0,2,4)B(12)F(12) system is unusual in how rapidly the three crystalline phases (the K(2)B(12)F(12) structure was reported recently) are interconverted, two of them reversibly. Isothermal gravimetric and DSC measurements showed that the reaction K(2)B(12)F(12 (s)) + 2 H(2)O((g)) → K(2)(H(2)O)(2)B(12)F(12 (s)) was complete in as little as 4 min at 25 °C when the sample was exposed to a stream of He or N(2) containing 21 Torr H(2)O((g)). The endothermic reverse reaction required as little as 18 min when K(2)(H(2)O)(2)B(12)F(12) at 25 °C was exposed to a stream of dry He. The products of hydration and dehydration were shown to be crystalline K(2)(H(2)O)(2)B(12)F(12) and K(2)B(12)F(12), respectively, by PXRD, and therefore these reactions are reconstructive solid-state reactions (there is also evidence that they may be single-crystal-to-single-crystal transformations when carried out very slowly). The hydration and dehydration reaction times were both particle-size dependent and carrier-gas flow rate dependent and continued to decrease up to the maximum carrier-gas flow rate of the TGA instrument that was used, demonstrating that the hydration and dehydration reactions were limited by the rate at which H(2)O((g)) was delivered to or swept away from the microcrystal surfaces. Therefore, the rates of absorption and desorption of H(2)O from unit cells at the surface of the microcrystals, and the rate of diffusion of H(2)O across the moving K(2)(H(2)O)(2)B(12)F(12 (s))/K(2)B(12)F(12 (s)) phase boundary, are even faster than the fastest rates of change in sample mass due to hydration and dehydration that were measured. The exchange of 21 Torr H(2)O((g)) with either D(2)O or H(2)(18)O in microcrystalline K(2)(D(2)O)(2)B(12)F(12) or K(2)(H(2)(18)O)(2)B(12)F(12) at 25 °C was also facile and required as little as 45 min to go to completion (H(2)O((g)) replaced both types of isotopically labeled water at the same rate for a given starting sample of K(2)B(12)F(12), demonstrating that water molecules were exchanging, not protons. Significant portions of mass (m) vs time (t) plots for the (1,2)H(2)O((g))/K(2)((2,1)H(2)O)(2)B(12)F(12 (s)) exchange reactions fit the equation m ∝ e(-kt), with 10(3)k = 1.9 s(-1) for one particle size distribution and 10(3)k = 0.50 s(-1) for another. Finally, K(2)(H(2)O)(2)B(12)F(12) was not transformed into K(2)(H(2)O)(4)B(12)F(12) after prolonged exposure to 21 Torr H(2)O((g)) at 25 °C, 37 Torr H(2)O((g)) at 35 °C, or 55 Torr H(2)O((g)) at 45 °C.

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