2-Adamantanone

Non-heme mu-Oxo- and bis(mu-carboxylato)-bridged diiron(iii) complexes of a 3N ligand as catalysts for alkane hydroxylation: stereoelectronic factors of carboxylate bridges determine the catalytic efficiency.[Pubmed:27336757]

Dalton Trans. 2016 Jul 28;45(28):11422-36.

A series of non-heme (mu-oxo)bis(mu-dicarboxylato)-bridged diiron(iii) complexes, [Fe2(O)(OOCH)2(L)2](2+)1, [Fe2(O)(OAc)2(L)2](2+)2, [Fe2(O)(Me3AcO)2(L)2](2+)3, [Fe2(O)(OBz)2(L)2](2+)4, [Fe2(O)(Ph2AcO)2(L)2](2+)5 and [Fe2(O)(Ph3AcO)3(L)2](2+)6, where L = N,N-dimethyl-N'-(pyrid-2-ylmethyl)ethylenediamine, OAc(-) = acetate, Me3AcO(-) = trimethylacetate, OBz(-) = benzoate, Ph2AcO(-) = diphenylacetate and Ph3AcO(-) = triphenylacetate, have been isolated and characterized using elemental analysis and spectral and electrochemical techniques. They have been studied as catalysts for the selective oxidation of alkanes using m-chloroperbenzoic acid (m-CPBA) as the oxidant. Complexes 2, 3, and 4 possess a distorted bioctahedral geometry in which each iron atom is coordinated to an oxygen atom of the mu-oxo bridge, two oxygen atoms of the mu-carboxylate bridge and three nitrogen atoms of the 3N ligand. In an acetonitrile/dichloromethane solvent mixture all the complexes display a d-d band characteristic of the triply bridged diiron(iii) core, revealing that they retain their identity in solution. Upon replacing electron-donating substituents on the bridging carboxylates by electron-withdrawing ones the E1/2 value of the one-electron Fe(III)Fe(III)--> Fe(III)Fe(II) reduction becomes less negative. On adding one equivalent of Et3N to a mixture of one equivalent of the complex and an excess of m-CPBA in the acetonitrile/dichloromethane solvent mixture an intense absorption band (lambdamax, 680-720 nm) appears, which corresponds to the formation of a mixture of complex species. All the complexes act as efficient catalysts for the hydroxylation of cyclohexane with 380-500 total turnover numbers and good alcohol selectivity (A/K, 6.0-10.1). Adamantane is selectively oxidized to 1-adamantanol and 2-adamantanol (3 degrees /2 degrees , 12.9-17.1) along with a small amount of 2-Adamantanone (total TON, 381-476), and interestingly, the sterically demanding trimethylacetate bridge around the diiron(iii) centre leads to high 3 degrees /2 degrees bond selectivity; on the other hand, the sterically demanding triphenylacetate bridge gives a lower 3 degrees /2 degrees bond selectivity. A remarkable linear correlation between the pKa of the bridging carboxylate and TON for both cyclohexane and adamantane oxidation is observed, illustrating the highest catalytic activity for 3 with strongly electron-releasing trimethylacetate bridges.

Synthesis of mesoporous Beta and Sn-Beta zeolites and their catalytic performances.[Pubmed:24777171]

Dalton Trans. 2014 Jun 14;43(22):8196-204.

Mesoporous Beta zeolite has been successfully prepared through hydrothermal synthesis in the presence of cationic ammonium-modified chitosan as the meso-template. Through a subsequent solid-gas reaction between highly dealuminated mesoporous Beta zeolite and SnCl4 steam at an elevated temperature, mesoporous Sn-Beta has been facilely obtained. It was revealed that the addition of cationic chitosan induced the nanocrystal aggregation to particle sizes of approximately 300 nm, giving rise to the intercrystalline/interparticle mesoporosity. In the Sn-implanting procedure, Sn species were demonstrated to be doped into the framework of the resulting mesoporous Beta zeolite in a tetrahedral environment without structural collapse. Due to the micro/mesoporous structures, both mesoporous Beta and Sn-Beta exhibited superior performances in alpha-pinene isomerization, Baeyer-Villiger oxidation of 2-Adamantanone by hydrogen peroxide and the isomerization of glucose in water, respectively.

Novel nickel(ii) complexes of sterically modified linear N4 ligands: effect of ligand stereoelectronic factors and solvent of coordination on nickel(ii) spin-state and catalytic alkane hydroxylation.[Pubmed:28418046]

Dalton Trans. 2017 Jun 6;46(22):7181-7193.

A series of Ni(ii) complexes of the types [Ni(L)(CH3CN)2](BPh4)21-3, 5 and [Ni(L4)](BPh4)24, where L = N,N'-bis(2-pyrid-2-ylmethyl)-1,4-diazepane (L1), N-(6-methylpyrid-2-ylmethyl)-N'-(pyrid-2-ylmethyl)-1,4-diazepane (L2), N,N'-bis(6-methyl-2-pyridylmethyl)-1,4-diazepane (L3), N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethylenediamine (L5) and L4 = N,N'-bis((1-methyl-1H-imidazole-2-yl)methyl)-1,4-diazepane, have been isolated and characterized. The complex cations of 1 and 4 possess, respectively, distorted octahedral and low-spin square planar coordination geometries in which nickel(ii) is meridionally coordinated to all four nitrogen atoms of L1 and L4. DFT studies reveal that L5 with the ethylenediamine backbone coordinates in the cis-beta mode in [Ni(L5)(CH3CN)2](2+)5, but in the cis-alpha mode in [Ni(L5)(H2O)2](2+). Also, they illustrate the role of ligand donor atom type, diazacyclo backbone and steric hindrance to coordination of pyridyl nitrogen in conferring novel coordination geometries on Ni(ii). All these complexes catalyse the oxidation of cyclohexane in the presence of m-CPBA as the oxidant up to 600 turnover numbers (TON) with relatively good alcohol selectivity (A/K, 5.6-7.2). Adamantane is oxidized to 1-adamantanol, 2-adamantanol and 2-Adamantanone with high bond selectivity (3 degrees /2 degrees , 8.7-11.7). The incorporation of methyl substituent(s) on one (2) or both (3) of the pyridyl rings and the replacement of both the pyridylmethyl arms in 1 by imidazolylmethyl arms to give 4 decrease the catalytic efficiency. Interestingly, 5 with the cis-beta mode of coordination provides two labile cis coordination sites for oxidant binding, leading to higher total TON and product/bond selectivity.

Glassy Dynamics versus Thermodynamics: The Case of 2-Adamantanone.[Pubmed:26073682]

J Phys Chem B. 2015 Jul 2;119(26):8468-74.

The heat capacity and thermal conductivity of the monoclinic and the fully ordered orthorhombic phases of 2-Adamantanone (C10H14O) have been measured for temperatures between 2 and 150 K. The heat capacities for both phases are shown to be strikingly close regardless of the site disorder present in the monoclinic crystal which arises from the occupancy of three nonequivalent sites for the oxygen atom. The heat capacity curves are also well accounted for by an evaluation carried out within the harmonic approximation in terms of the g(omega) vibrational frequency distributions measured by means of inelastic neutron scattering. Such spectral functions show however a significant excess of low frequency modes for the crystal showing statistical disorder. In contrast, large differences are found for the thermal conductivity which contrary to what could be expected, shows the substitutionally disordered crystal to exhibit better heat transport properties than the fully ordered orthorhombic phase. Such an anomalous behavior is understood from examination of the crystalline structure of the orthorhombic phase which leads to very strong scattering of heat-carrying phonons due to grain boundary effects able to yield a largely reduced value of the conductivity as well as to a plateau-like feature at intermediate temperatures which contrasts with a bell-shaped maximum shown by data pertaining the disordered crystal. The relevance of the present findings within the context of glassy dynamics of the orientational glass state is finally discussed.

Reliable determination of amidicity in acyclic amides and lactams.[Pubmed:22646836]

J Org Chem. 2012 Jul 6;77(13):5492-502.

Two independent computational methods have been used for determination of amide resonance stabilization and amidicities relative to N,N-dimethylacetamide for a wide range of acyclic and cyclic amides. The first method utilizes carbonyl substitution nitrogen atom replacement (COSNAR). The second, new approach involves determination of the difference in amide resonance between N,N-dimethylacetamide and the target amide using an isodesmic trans-amidation process and is calibrated relative to 1-aza-2-Adamantanone with zero amidicity and N,N-dimethylacetamide with 100% amidicity. Results indicate excellent coherence between the methods, which must be regarded as more reliable than a recently reported approach to amidicities based upon enthalpies of hydrogenation. Data for acyclic planar and twisted amides are predictable on the basis of the degrees of pyramidalization at nitrogen and twisting about the C-N bonds. Monocyclic lactams are predicted to have amidicities at least as high as N,N-dimethylacetamide, and the beta-lactam system is planar with greater amide resonance than that of N,N-dimethylacetamide. Bicyclic penam/em and cepham/em scaffolds lose some amidicity in line with the degree of strain-induced pyramidalization at the bridgehead nitrogen and twist about the amide bond, but the most puckered penem system still retains substantial amidicity equivalent to 73% that of N,N-dimethylacetamide.

Metathesis reactions of a manganese borylene complex with polar heteroatom-carbon double bonds: a pathway to previously inaccessible carbene complexes.[Pubmed:23692498]

J Am Chem Soc. 2013 Jun 12;135(23):8726-34.

A comprehensive study has been carried out to investigate the metathesis reactivity of the terminal alkylborylene complex [(eta(5)-C5H5)(OC)2Mn horizontal lineB(tBu)] (1). Its reactions with 3,3',5,5'-tetrakis(trifluoromethyl)benzophenone, 4,4'-dimethylbenzophenone, 2-Adamantanone, 4,4'-bis(diethylamino)benzophenone, and 1,2-diphenylcyclopropen-3-one afforded the metathesis products [(eta(5)-C5H5)(OC)2Mn horizontal lineCR2] (R = C6H3-3,5-(CF3)23a, C6H4-4-Me 3b, C6H4-4-NEt23d; CR2 = adamantylidene 3c, cyclo-C3Ph23e). The cycloaddition intermediates were detected by NMR spectroscopy from reactions involving ketones with more electron-withdrawing substituents. The reaction of 1 with dicyclohexylcarbodiimide (DCC) only proceeds to form the cycloaddition product [(eta(5)-C5H5)(OC)2Mn{kappa(2)-C,B-C( horizontal lineNCy)N(Cy)B(tBu)}] (4), which upon warming, rearranges to afford complex [(eta(5)-C5H5)(OC)2Mn{CN(Cy)B(tBu)CN(Cy)}] (5). The reaction of 1 with triphenylphosphine sulfide SPPh3 also yields the metathesis product [(eta(5)-C5H5)(OC)2Mn(PPh3)] via an intermediate which is likely to be a eta(2)-thioboryl complex [(eta(5)-C5H5)(OC)2Mn{(eta(2)-SB(tBu)}] (6). Similar reactions have been studied using an iron borylene complex [(Me3P)(OC)3Fe horizontal lineB(Dur)] (Dur = 2,3,5,6-tetramethylphenyl, 9). Extensive computational studies have been also carried out to gain mechanistic insights in these reactions, which provided reaction pathways that fit well with the experimental data.

Nickel(II) complexes of pentadentate N5 ligands as catalysts for alkane hydroxylation by using m-CPBA as oxidant: a combined experimental and computational study.[Pubmed:25100547]

Chemistry. 2014 Sep 1;20(36):11346-61.

A new family of nickel(II) complexes of the type [Ni(L)(CH(3)CN)](BPh(4))(2), where L=N-methyl-N,N',N'-tris(pyrid-2-ylmethyl)-ethylenediamine (L1, 1), N-benzyl-N,N',N'-tris(pyrid-2-yl-methyl)-ethylenediamine (L2, 2), N-methyl-N,N'-bis(pyrid-2-ylmethyl)-N'-(6-methyl-pyrid-2-yl-methyl)-ethylenediami ne (L3, 3), N-methyl-N,N'-bis(pyrid-2-ylmethyl)-N'-(quinolin-2-ylmethyl)-ethylenediamine (L4, 4), and N-methyl-N,N'-bis(pyrid-2-ylmethyl)-N'-imidazole-2-ylmethyl)-ethylenediamine (L5, 5), has been isolated and characterized by means of elemental analysis, mass spectrometry, UV/Vis spectroscopy, and electrochemistry. The single-crystal X-ray structure of [Ni(L(3))(CH(3)CN)](BPh(4))(2) reveals that the nickel(II) center is located in a distorted octahedral coordination geometry constituted by all the five nitrogen atoms of the pentadentate ligand and an acetonitrile molecule. In a dichloromethane/acetonitrile solvent mixture, all the complexes show ligand field bands in the visible region characteristic of an octahedral coordination geometry. They exhibit a one-electron oxidation corresponding to the Ni(II) /Ni(III) redox couple the potential of which depends upon the ligand donor functionalities. The new complexes catalyze the oxidation of cyclohexane in the presence of m-CPBA as oxidant up to a turnover number of 530 with good alcohol selectivity (A/K, 7.1-10.6, A=alcohol, K=ketone). Upon replacing the pyridylmethyl arm in [Ni(L1)(CH(3)CN)](BPh(4))(2) by the strongly sigma-bonding but weakly pi-bonding imidazolylmethyl arm as in [Ni(L5)(CH(3)CN)](BPh(4))(2) or the sterically demanding 6-methylpyridylmethyl ([Ni(L3)(CH(3)CN)](BPh(4))(2) and the quinolylmethyl arms ([Ni(L4)(CH(3)CN)](BPh(4))(2), both the catalytic activity and the selectivity decrease. DFT studies performed on cyclohexane oxidation by complexes 1 and 5 demonstrate the two spin-state reactivity for the high-spin [(N5)Ni(II)-O(.)] intermediate (ts1(hs), ts2(doublet)), which has a low-spin state located closely in energy to the high-spin state. The lower catalytic activity of complex 5 is mainly due to the formation of thermodynamically less accessible m-CPBA-coordinated precursor of [Ni(II) (L5)(OOCOC(6)H(4)Cl)](+) (5 a). Adamantane is oxidized to 1-adamantanol, 2-adamantanol, and 2-Adamantanone (3 degrees /2 degrees , 10.6-11.5), and cumene is selectively oxidized to 2-phenyl-2-propanol. The incorporation of sterically hindering pyridylmethyl and quinolylmethyl donor ligands around the Ni(II) leads to a high 3 degrees /2 degrees bond selectivity for adamantane oxidation, which is in contrast to the lower cyclohexane oxidation activities of the complexes.

Isolable 2,3-disila-1,3-butadiene from a double sila-Peterson reaction.[Pubmed:24986491]

Chemistry. 2014 Jul 21;20(30):9424-30.

A new 2,3-disila-1,3-butadiene (3) was synthesized as pale yellow crystals by a double sila-Peterson reaction of 1,1,2,2-tetrasilyl-1,2-dilithiodisilane with two equivalents of 2-Adamantanone at 0 degrees C. In the solid state, the two Si=C bonds adopt a synclinal conformation with a dihedral angle of 76.8(1) degrees . UV/Vis spectra show two distinct absorption bands, assignable to the pi(Si=C)-->pi*(Si=C) transition, at 371 and 322 nm and the former is considerably redshifted compared with that of structurally similar silenes. The 2,3-disilabutadiene isomerizes to the corresponding 1,3-disilabicyclo[1.1.0]butane with the activation parameters of DeltaH( not equal) = 74.5+/-5.4 kJ mol(-1) and DeltaS( not equal) = -71.1+/-17.1 J mol(-1) K(-1). DFT studies suggest that the isomerization proceeds through a conrotatory route rather than a disrotatory route. H2O and 9,10-phenanthrenequinone added across each Si=C bond in the 2,3-disila-1,3-butadiene. The UV/Vis spectrum and reactivity of 3 suggest that the interaction between the two Si=C bonds in 3 would be significant but rather small compared with that between Si=Si bonds in a synclinal tetrasilabutadiene.