Mesityl Ring Research Articles

Synthesis and characterization of carbonyl functionalized organotellurium(iv) derivatives.

The current study focuses on synthesis and characterization of carbonyl functionalized unsymmetrical diorganotellurium(iv) dichlorides (1-5), dibromide (6), and their characterization by elemental analysis, 1H, 13C{1H}, and 125Te NMR spectroscopy. In addition to this, compounds 1, 4 and 5 were further confirmed via single-crystal X-ray studies. Reduction of all the dichlorides with Na2S2O5 affords labile tellurides, which decompose quickly even at room temperature into the more stable symmetric ditellurides, Ar2Te2. Mesityl fragments bearing organotellurium(iv) derivatives show separate 1H and 13C{1H} NMR signals for the ortho methyls and meta protons of the mesityl ring. Among the Te(iv) dichlorides, the observed O-H⋯O, C-H⋯O, C-H⋯Cl, Te⋯O and Te⋯Cl hydrogen and secondary bonding interactions are longer than Σr cov (sum of the covalent bond radii) and significantly shorter than Σr vdw (sum of the van der Waal radii) respectively. The linearity of the C-Te⋯O, C-H⋯O and C-H⋯Cl makes n → σ* orbital interaction possible.

Dehydrogenative Double C-H Bond Activation in a Germylene-Rhodium Complex*.

Transition metal tetrylene complexes offer great opportunities for molecular cooperation due to the ambiphilic character of the group 14 element. Here we focus on the coordination of germylene [(ArMes2)2Ge :] (ArMes=C6H3‐2,6‐(C6H2‐2,4,6‐Me3)2) to [RhCl(COD)]2 (COD=1,5‐cyclooctadiene), which yields a neutral germyl complex in which the rhodium center exhibits both η 6‐ and η 2‐coordination to two mesityl rings in an unusual pincer‐type structure. Chloride abstraction from this species triggers a singular dehydrogenative double C−H bond activation across the Ge/Rh motif. We have isolated and fully characterized three rhodium‐germyl species associated to three C−H cleavage events along this process. The reaction mechanism has been further investigated by computational means, supporting the key cooperative action of rhodium and germanium centers.

Cooperative Bond Activation and Facile Intramolecular Aryl Transfer of Nickel–Aluminum Pincer‐type Complexes

AbstractPincer‐type nickel–aluminum complexes were synthesized using two equivalents of the phosphinoamide, [PhNCH2PiPr2]−. The Ni0–AlIII complexes, {(MesPAlP)Ni}2(μ‐N2) and {(MesPAlP)Ni}2(μ‐COD), where MesPAlP is (Mes)Al(NPhCH2PiPr2)2, were structurally characterized. The (PAlP)Ni system exhibited cooperative bond cleavage mediated by the two‐site Ni–Al unit, including oxidative addition of aryl halides, H2 activation, and ortho‐directed C−H bond activation of pyridine N‐oxide. One intriguing reaction is the reversible intramolecular transfer of the mesityl ring from the Al to the Ni site, which is evocative of the transmetalation step during cross‐coupling catalysis. The aryl‐transfer product,(THF)Al(NPhCH2PiPr2)2Ni(Mes), is the first example of a first‐row transition metal–aluminyl pincer complex. The addition of a judicious donor enables the Al metalloligand to convert reversibly between the alane and aluminyl forms via aryl group transfer to and from Ni, respectively. Theoretical calculations support a zwitterionic Niδ−–Alδ+ electronic structure in the nickel–aluminyl complex.

Cooperative Bond Activation and Facile Intramolecular Aryl Transfer of Nickel-Aluminum Pincer-type Complexes.

Pincer-type nickel-aluminum complexes were synthesized using two equivalents of the phosphinoamide, [PhNCH2 Pi Pr2 ]- . The Ni0 -AlIII complexes, {(Mes PAlP)Ni}2 (μ-N2 ) and {(Mes PAlP)Ni}2 (μ-COD), where Mes PAlP is (Mes)Al(NPhCH2 Pi Pr2 )2 , were structurally characterized. The (PAlP)Ni system exhibited cooperative bond cleavage mediated by the two-site Ni-Al unit, including oxidative addition of aryl halides, H2 activation, and ortho-directed C-H bond activation of pyridine N-oxide. One intriguing reaction is the reversible intramolecular transfer of the mesityl ring from the Al to the Ni site, which is evocative of the transmetalation step during cross-coupling catalysis. The aryl-transfer product,(THF)Al(NPhCH2 Pi Pr2 )2 Ni(Mes), is the first example of a first-row transition metal-aluminyl pincer complex. The addition of a judicious donor enables the Al metalloligand to convert reversibly between the alane and aluminyl forms via aryl group transfer to and from Ni, respectively. Theoretical calculations support a zwitterionic Niδ- -Alδ+ electronic structure in the nickel-aluminyl complex.

Dearomatizing and Derivatizing a Mesityl Group on Boron by One‐Pot Photoisomerization and [4+2] Diels–Alder Addition

Boron compounds having a conjugated chelate backbone (N,C-chelate or C,C-chelate) and two mesityl substituents on boron have been found to undergo a facile one-pot transformation/reaction with dienophiles, which leads to the dearomatization of one mesityl ring and its [4+2] Diels-Alder addition with the dienophile. Photochemical activation is the key in this transformation of the aryl ring.

Di-μ-acetato-bis{[3-benzyl-1-(2,4,6-trimethylphenyl)imidazol-2-ylidene]silver(I)}.

The title compound, [Ag2(C2H3O2)2(C19H20N2)2] (2), was readily synthesized by treatment of 3-benzyl-1-(2,4,6-trimethylphenyl)imidazolium chloride with silver acetate. The solution structure of the complex was analyzed by NMR spectroscopy, while the solid-state structure was confirmed by single-crystal X-ray diffraction studies. Compound 2 crystallizes in the triclinic space group , with a silver-to-carbene bond length (Ag-CNHC) of 2.084 (3) Å. The molecule resides on an inversion center, so that only half of the molecule is crystallographically unique. The planes defined by the two imidazole rings are parallel to each other, but not coplanar [interplanar distance is 0.662 (19) Å]. The dihedral angles between the imidazole ring and the benzyl and mesityl rings are 77.87 (12) and 72.86 (11)°, respectively. The crystal structure features π-π stacking interactions between the benzylic groups of inversion-related (-x + 1, -y + 1, -z + 1) molecules and C-H ⋯ π interactions.

Recyclable synthesis of mesityl iodonium(III) salts

An efficient protocol for C–H condensation of hypervalent iodine compounds toward arenes in fluoroalcohols has been applied to the recyclable preparation of mesityl iodonium(III) salts. The electrophilicities of [hydroxy(tosyloxy)iodo]mesitylene (MesI(OH)OTs) and iodomesitylene diacetate (MesI(OAc)2) are suitably enhanced in 2,2,2-trifluoroethanol. A series of nucleophilic aromatic compounds react smoothly with MesI(OH)OTs and MesI(OAc)2 or in situ hypervalent iodine(III) species, generated from iodomesitylene, to provide the target mesityl iodonium(III) salts in good yields at room temperature with broad functional group tolerance. This C–H condensation strategy merits high para-regioselectivities during the diaryliodonium(III) salt formation, but the major limitation in the case of low-reactive aromatic substrates is byproduct formation resulting from the self-condensation of the nucleophilic mesitylene ring in MesI(OH)OTs and MesI(OAc)2.

Electron transport and nonlinear optical properties of substituted aryldimesityl boranes: a DFT study.

A comprehensive theoretical study was carried out on a series of aryldimesityl borane (DMB) derivatives using Density Functional theory. Optimized geometries and electronic parameters like electron affinity, reorganization energy, frontiers molecular contours, polarizability and hyperpolarizability have been calculated by employing B3PW91/6-311++G (d, p) level of theory. Our results show that the Hammett function and geometrical parameters correlates well with the reorganization energies and hyperpolarizability for the series of DMB derivatives studied in this work. The orbital energy study reveals that the electron releasing substituents increase the LUMO energies and electron withdrawing substituents decrease the LUMO energies, reflecting the electron transport character of aryldimesityl borane derivatives. From frontier molecular orbitals diagram it is evident that mesityl rings act as the donor, while the phenylene and Boron atom appear as acceptors in these systems. The calculated hyperpolarizability of secondary amine derivative of DMB is 40 times higher than DMB (1). The electronic excitation contributions to the hyperpolarizability studied by using TDDFT calculation shows that hyperpolarizability correlates well with dipole moment in ground and excited state and excitation energy in terms of the two-level model. Thus the results of these calculations can be helpful in designing the DMB derivatives for efficient electron transport and nonlinear optical material by appropriate substitution with electron releasing or withdrawing substituents on phenyl ring of DMB system.

Terpyridine–Triarylborane Conjugates for the Dual Complexation of Zinc(II) Cation and Fluoride Anion

A series of ditopic terpyridine–triarylborane conjugates (1–3) in which 4′-ethynylterpyridine is linked to the para, meta, and ortho positions of the phenyl ring of dimesitylphenylborane (Mes2PhB), respectively, were prepared to investigate the dual complexation behavior of the conjugates toward Zn(II) cation and fluoride anion. The crystal structures of the corresponding Zn(II) complexes (L·ZnCl2, L = 1–3) reveal the formation of a 1:1 adduct between ZnCl2 and a conjugate, with a five-coordinate Zn(II) center bound to three nitrogen atoms and two chlorine atoms. In particular, the structure of ortho-substituted 3·ZnCl2 in comparison with that of 3 indicates the presence of π–π interactions between the mesityl ring and ethynylene–pyridine fragment in 3·ZnCl2. UV/vis absorption and fluorescence spectra of 1–3 display low-energy bands mainly assignable to a π(Ar) → pπ(B) (Ar = Mes and/or phenylene–ethynylene) charge transfer (CT) transition. The transition in Zn(II) complexes has a π(Mes) → π*(Ar) (Ar = ter...

Heteroleptic Cu(I) Bis-diimine Complexes of 6,6′-Dimesityl-2,2′-bipyridine: A Structural, Theoretical and Spectroscopic Study

A series of heteroleptic Cu(I) complexes containing 6,6'-dimesityl-2,2'-bipyridine and phenanthroline-, bipyridine-, and biquinoline-based ligands is studied. The HETPHEN strategy is utilized to synthesize the heteroleptic complexes, which are stable in solution. The X-ray crystal structures of the complexes are presented; the solid-state four-coordinate Cu(I) geometries are quantified by using the τ4 parameter. A feature of the crystal structures is the intramolecular π-stacking between the mesityl ring(s) and the diimine ligand; the phen-based complexes exhibit stacking between the phen ligand and one of the mesityl rings, creating a "Pac-Man" motif. On the other hand, the bpy-based complexes show different types of packing interaction, with both mesityl rings "clamping down" on the bpy based ligand to give π-stacking. Cyclic voltammetry is used to examine the redox chemistry of the complexes. The most positive potentials for the oxidation process are observed for the complexes with bulky substituents ortho to the coordination nitrogens atoms, i.e., 2,9-dimethyl-1,10-phenanthroline and 6,6'-dibromo-2,2'-bipyridine. The Cu(I) MLCT transitions of the complexes are investigated by resonance Raman spectroscopy in concert with TD-DFT calculations. The resonance Raman spectra of complexes containing substituted biquinolines are straightforward, in that vibrational bands of the biquinoline-based ligand are selectively enhanced over bpy(Mes)2 bands. This is consistent with the purple color of the complexes, due to the lower energy of the biquinoline-based LUMO compared to the bpy(Mes)2 LUMO. All the phen- and bpy-based complexes show enhancement of bpy(Mes)2 bands.

Guest encapsulation and coronene–C60 exchange in supramolecular zinc porphyrin tweezers, grids and prisms

Using a variant of the HETPHEN concept, heteroleptic 2D and 3D metallosupramolecular structures, such as tweezer T, grid G and tetragonal prism P, were fabricated quantitatively and characterised by (1)H NMR, (13)C NMR, (1)H-(1)H COSY, DOSY as well as ESI-MS. All structures encapsulate C60, with P showing the highest binding affinity (Kassoc = 3.3 × 10(6) M(-1)). The association constant increases along the series T < G < P, most likely due to the enhanced structural rigidity and better coplanarity of the two zinc porphyrin units. In contrast to T and G, the tetragonal prism P shows notable encapsulation of coronene (Kassoc = 1.1 × 10(4) M(-1)). In T and G, on the other hand, complexation of coronene is kinetically inhibited by the bulky mesityl rings at the porphyrin periphery. As illustrated in the facile displacement of coronene by C60 in coronene@P to furnish C60@P, P behaves as a flexible and guest-adaptive host.

Structure of new tridentate 2,6-bis(imino)-pyridyl ruthenium(II) complexes with 2,3,6-trimethyl benzenamine ligand

New tridentate 2,6-bis(imino)pyridyl ruthenium(II) complexes, [N3]Ru(H)(Cl)(2,4,6-(CH3)3C6H2NH2) (4) and [N3]Ru(Cl)2(2,4,6-(CH3)3C6H2NH2) (5) ([N3] = 2,6-(2,4,6-(CH3)3C6H2N=CCH3)2C5H3N) have been synthesized and characterized. The crystal of complex 4, which has been grown in benzene/cyclohexane by evaporation at room temperature, was studied by X-ray diffraction. Complex 4 crystallizes in the monoclinic space group C2/c with cell parameters of a = 42.243(4) A, b = 8.1480(5) A, c = 23.662(2) A, β = 117.998(1)°, V = 7191.1(10)A3, and Z = 8. The molecular structure of 4 shows a six coordinate, pseudo-octahedral geometry with a trans arrangement of hydrogen and chloride ligands. The mesityl ligands are oriented approximately perpendicular to the 2,6-bis(imino)pyridyl ligand plane, and form a pocket surrounding the 2,4,6-trimethyl benzenamine ligand. The coordinated 2,4,6-trimethyl benzenamine (2,4,6-(CH3)3C6H2NH2) is in the cis to chloride and hydride, trans to pyridine ligand, and lies parallel to one of the mesityl rings.

N,N′-Bis[(E)-2,4,6-trimethylbenzylidene]ethane-1,2-diamine

The title compound, C22H28N2, which is a double imine derived from ethane-1,2-diamine and mesityl aldehyde, has crystallographic inversion symmetry, with both C=N bonds E configured. The dihedral angle between the mesityl ring system and the imide functional group is 23.89 (17)°.

Photoisomerization of 1-Phenyl-2-(pyridin-2-yl)indole BMes2: The Dark Isomer

A new member of photochromic N,C-chelate organoboron compounds, BMes2(Py-N-Ph-In) (1), where Mes = mesityl, Py-N-Ph-In = 1-Ph-2-(2-Py)-indolyl, has been synthesized, and its photo-thermal isomerization properties have been investigated. Upon irradiation by UV light (365 nm), compound 1 isomerizes to compound 1a, changing color from light yellow to dark turquoise-green with the disappearance of the green fluorescence of 1. This process involves the breaking/formation of a B−C bond and a C−C bond and is thermally reversible. Compound 1a finally allowed us to obtain suitable crystals. The crystals of the dark isomer 1a were isolated, and its structure was determined by a single-crystal X-ray diffraction analysis, which confirms the formation of a C−C bond between the indolyl ring and a mesityl ring, the dearomatization of the mesityl ring, and the presence of a BC2 triangle in 1a. NMR and DFT computational data further support that 1a is an analogue of the dark isomers generated from previously reported N,C-chelate BMes2 compounds.

3-(2,4,6-Trimethyl-benzo-yl)-2-naphthoic acid.

The asymmetric unit of the title compound, C21H18O3, contains two crystallographically independent mol­ecules. The two mol­ecules are linked into cyclic centrosymmetric dimers R 2 2(8) by O—H⋯O hydrogen bonds. The dihedral angles between the naphthalene ring system and the benzene ring are 87.0 (8) and 84.4 (2)° in the two mol­ecules. The crystal packing is stabilized by O—H⋯O, C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.664 (11) Å]. In one mol­ecule, the mesityl ring is disordered over two positions [occupancy ratio 0.690 (3):0.690 (3)].

Structural Characterization of a Copper Nitrosyl Complex with a {CuNO}10 Configuration

The synthesis and characterization of a {CuNO}(10) complex, namely, [Cu(CH(3)NO(2))(5)(NO)][PF(6)](2), has been achieved by the addition of [NO][PF(6)] to copper metal powder in the presence of nitromethane. In the solid state, this complex exhibits a bent Cu-N-O moiety [Cu-N-O = 121.0(3)°] and a long Cu-N bond. This complex readily reacts with mesitylene to form [mesitylene, NO][PF(6)] and [Cu(η(2)-1,3,5-Me(3)C(6)H(3))(2)][PF(6)] by transfer of NO(+) to the mesitylene ring.

Mesityl(2,4,6-trimethoxyphenyl)borinic acid

In the title mol­ecule, C18H23BO4, the dihedral angle between the least-squares planes of the aromatic rings is 84.88 (3)°. The B atom deviates by 0.202 (1) Å from the least-squares plane of the mesityl ring. All of the meth­oxy groups are approximately coplanar with the 2,4,6-trimeth­oxy­phenyl ring, whereas the BOH group is twisted with respect to it by 19.5°. The borinic OH group is engaged in an intra­molecular O—H⋯O hydrogen bond with one of ortho-meth­oxy groups. The mol­ecular structure is stabilized by weak C—H⋯O contacts. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯π inter­actions, generating a three-dimensional network.

One, two, and three methylene phosphonic acid groups (–CH2PO3H2) on a mesitylene ring: synthesis, characterization and aspects of supramolecular aggregation

The ease of substitution of –CH2Br group on the mesitylene ring in a stepwise manner has been exploited to prepare mesitylene mono-, bis-, and tris-methylene phosphonic acids C6H2Me3(CH2PO3H2) (1), C6HMe3(CH2PO3H2)2 (2), and C6Me3(CH2PO3H2)3 (3) in 80–90% yield, through a Michaelis–Arbuzov reaction followed by acid hydrolysis. Compounds 1–4 have been characterized by analytical and spectroscopic (IR, NMR, and MS) techniques. The X-ray structural investigations on all the three compounds reveal that the central mesitylene ring is a robust platform for hosting multiple methylene phosphonic acid groups. Mesitylene mono-methylene phosphonic acid 1, which can be considered as the sterically encumbered modification of benzyl phosphonic acid, interestingly associates as a one-dimensional tubular structure through extensive O–H⋯O hydrogen bonding between adjacent –PO3H2 groups, albeit with no such interactions between the tubes due to the highly hydrophobic nature of the surface. The X-ray structure of mesitylene-1,3-diphosphonic acid 2 reveals that the molecules exhibit a syn-orientation of the –CH2PO3H2, which are involved in extensive P–OH⋯O hydrogen bonding to result in a two-dimensional layered structure. The presence of three –PO3H2 units on the same side of the mesitylene ring in 3 results in a three-dimensional framework solid. The present studies clearly reveal a linear relationship between the dimensionality of the supramolecular structure and the number of phosphonic acid moieties on the mesitylene ring.

Solvent-free mesityllithium: solid-state structure and its reactivity towards white phosphorus

The donor-free mesityllithium was prepared from the reaction of MesBr with n-BuLi in diethyl ether at -78 degrees C. The solid-state structure of unsupported mesityllithium consists of C(2)Li(2)-rings composed of two LiMes units, which interact with adjacent dimers [LiMes](2), forming a polymeric infinite chain along the crystallographic c-axis (monoclinic space group, P2(1)/n). The structure of donor-free mesityllithium reveals short contacts between the C atoms of the mesityl rings and the lithium atoms of neighbouring [LiMes](2) units. The structure determination of LiMes was performed by X-ray powder diffraction. In addition we have investigated the reaction of LiMes with Me(3)SnCl and P(4) for our understanding of the reactivity of donor-free mesityllithium. The heterogeneous reaction of donor-free mesityllithium with Me(3)SnCl produces conveniently the stannylated mesitylene Me(3)SnMes (triclinic, space group P1). White phosphorus reacts with three equivalents of unsupported mesityllithium in benzene to give Li(3)P(4)Mes(3). In this context it should be noted that a tetraphosphide with an identical LiP-core as in Li(3)P(4)Mes(3) had been formed in the 1:3 reaction of P(4) with the silanide Li[SitBu(3)]. The tetraphosphide Li(3)P(4)Mes(3) was analyzed using X-ray crystallography (monoclinic, space group C2/c).

Synthesis and Crystal Structure of a Silyl‐Stabilized Allyl Cation Formed by Disruption of an Arene by a Protonation–Hydrosilylation Sequence

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH(3)C(6)H(6)]- [CHB(11)Me(5)Br(6)] initiates a cascade reaction that results in a stable beta-silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate.