I. A. Tikhonova

Crown compounds for anions. Unusual complex of trimetric perfluoro-o-phenylenemercury with the bromide anion having a polydecker sandwich structure

Abstract Here we show that cyclic trimetric perfluoro- o -phenylenemercury ( o -C 6 F 4 Hg) 3 is capable of forming complexes with [PPh 4 ] + Br − , [PPh 3 Me] + I − and [PPh 4 ] + Cl − of the composition [( o -C 6 F 4 Hg) 3 X] − [PR 3 R′] + (X = Br, R = R′ = Ph; X = I, R = Ph, R′ = Me) or {[( o -C 6 F 4 Hg) 3 X 2 } 2− [PR 3 R′] + 2 (X = Cl, R = R′ = Ph). An X-ray study of the complex with [PPh 4 ] + Br − revealed that it has the unusual structure of the polydecker bent sandwich wherein each Br − anion is coordinated with six mercury atoms of two neighbouring molecules of ( o -C 6 F 4 Hg) 3 .

Coordination chemistry of polymercuramacrocycles. Complexation of cyclic trimeric perfluoro-o-phenylenemercury with neutral oxygeneous Lewis bases

Cyclic trimeric perfluoro- o -phenylenemercury ( o -C 6 F 4 Hg) 3 ( I ) readily reacts with N , N -dimethylformamide and hexamethylphosphoramide to form complexes {[( o -C 6 F 4 Hg) 3 ](HCONMe 2 ) 2 } ( II ) and {[( o -C 6 F 4 Hg) 3 ][(Me 2 N) 3 PO] 2 } ( III ), respectively, which contain two amide ligands per one macrocycle molecule. An X-ray diffraction study of II and III has shown that they have bipyramidal structures wherein the molecules of an amide are located above and below the metallacycle plane and each of them is simultaneously bonded via the oxygen atom to all Hg atoms of the cycle. The reaction of I with dimethylsulfoxide affords complex {[( o -C 6 F 4 Hg) 3 ](Me 2 SO) 3 } ( VI ) containing three Lewis basic species per molecule of I . According to X-ray diffraction data, two of three dimethylsulfoxide ligands in VI are also coordinated through the oxygen atom with all mercury centres of the macrocycle, forming a bipyramidal structure, while the third sulfoxide ligand is bonded only to one Hg atom of the cycle. The complex of similar composition and structure, {[( o -C 6 F 4 Hg) 3 ](MeCOOEt) 3 } ( IV ), is produced in the interaction of I with ethyl acetate but this complex is much less stable than VI . The latter correlates with a considerably lower Lewis basicity of ethyl acetate as compared to that of dimethylsulfoxide.

Perfluorinated polymercuramacrocycles as anticrowns. Applications in catalysis

The catalytic and complexing properties of two perfluorinated polymercuramacrocycles, viz., cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 and cyclic pentameric perfluoroisopropylidenemercury [(CF3)2CHg]5, are analyzed. These macrocycles contain several Lewis acidic centers in the ring and can be considered as peculiar antipodes of crown ethers and their thia and aza analogs. Both macrocycles can efficiently bind various anions to form unique complexes, in which the anionic species is simultaneously coordinated to all Lewis acidic atoms of the ring. For the (o-C6F4Hg)3 macrocycle, unusual complexes with various neutral Lewis bases, such as nitriles, carbonyl compounds, aromatic hydrocarbons, etc., were also described. Data on the activity of polymercury-containing macrocycles in phase transfer catalysis of electrophilic reactions and proton transfer from an aqueous to an organic phase are surveyed and discussed.

Crown Compounds for Anions: Sandwich and Half-Sandwich Complexes of Cyclic Trimeric Perfluoro-o-phenylenemercury with Polyhedralcloso-[B10H10]2− andcloso-[B12H12]2− Anions

It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4-Hg)3 (1) is capable of binding closo-[B10H10]2- and closo-[B12H12]2- anions to form complexes [[(o-C6F4Hg)3](B10-H10)]2- (2), [[(o-C6F4Hg)3]2(B10H10)]2-(3), [[(o-C6F4Hg)3](B12H12)]2- (4), and [[(o-C6F4Hg)3]2(B12H12)]2- (5). According to IR data, the bonding of the [B10H10]2- and [B12H12]2- ions to the macrocycle in these complexes is accomplished through the formation of B-H-Hg bridges. Complexes 2, 3, and 5 have been isolated in analytically pure form and have been characterized by spectroscopic means. X-ray diffraction studies of 3 and 5 have revealed that these compounds have unusual sandwich structures, in which the polyhedral di-anion is located between the planes of two molecules of 1 and is bonded to each of them through two types of B-H-Hg bridges. One type is the simultaneous coordination of a B-H group to all three Hg atoms of the macrocycle. The other type is the coordination of a B-H group to a single Hg atom of the cycle. According to X-ray diffraction data, complex 2 has an analogous but half-sandwich structure. The obtained complexes 2-5 are quite stable; their stability constants in THF/acetone (1:1) at 20 degrees C have been determined as 1.0 x 10(2)Lmol(-1), 2.6 x 10(3)L(2)mol(2), 0.7 x 10(2)Lmol(-1), and 0.98 x 10(3)L(2)mol(-2), respectively.

Crown compounds for anions. A spinning top-shaped complex of cyclic pentameric perfluoroisopropylidenemercury with two chloride anions

Abstract It has been found that cyclic pentameric perfluoroisopropylidenemercury, [(CF 3 ) 2 CHg] 5 , is capable of forming complexes with [PPh 4 ] + Cl − and [PPh 4 ] + Br − of the type {[(CF 3 ) 2 CHg] 5 X 2 } 2− [PPh 4 ] 2 + (X = Cl or Br). According to an X-ray diffraction study, the chloride anions in the complex of [(CF 3 ) 2 CHg] 5 with [PPh 4 ] + Cl − are located above and below the mercury-containing metallacycle, each Cl − anion being coordinated with all the five mercury atoms of [(CF 3 ) 2 CHg] 5 .

Complexation of cyclic trimeric perfluoro-o-phenylenemercury with nitriles. A remarkable sensitivity of the composition and structure of the resulting complexes to the nature of a nitrile

Abstract Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (I) is capable of reacting with nitriles to form complexes whose composition and structure are dramatically dependent on the nature of the nitrile used. In the case of acrylonitrile, the complex, [(o-C6F4Hg)3(CH2CHCN)], containing one nitrile molecule per one molecule of I is produced. According to an X-ray structure analysis, the acrylonitrile ligand in this complex is bonded to all Hg atoms of the cycle through the nitrogen atom. The reaction of I with acetonitrile gives complex [(o-C6F4Hg)3(MeCN)2] which contains two nitrile ligand per one molecule of the macrocycle. This complex has a shape of a spinning top the equatorial girdle of which is the mercury-containing metallacycle, whilst the axis direction is fixed by the linear MeCN ligands located above and below the metallacycle plane. Finally, the isolated complex of I with benzonitrile, [(o-C6F4Hg)3(PhCN)3], contains three molecules of the coordinated nitrile per one macrocycle molecule. A remarkable structural feature of this complex is that here all the nitrile ligands are located on one side of the metallacycle plane and, in addition, differ from each other in the geometry of coordination with the Hg atoms.

Crown compounds for anions. A polymeric complex of cyclic trimeric perfluoro-o-phenylenemercury with thiocyanate anion containing an infinite helical chain of alternating molecules of mercury-containing macrocycle and SCN− ions

Abstract It has been shown by IR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 is capable of binding thiocyanate anions in acetone solution, forming complexes whose composition is dependent on the ratio of reagents. In the interaction of (o-C6F4Hg)3 with an equimolar amount of [nBu4N]+ SCN− in ethanol the complex formulated as [(o- C 6 F 4 Hg ) 3 ( SCN )] − [ n Bu 4 N ] + has been isolated. An X-ray diffraction study of the complex has revealed that in the solid state it is polymeric and contains an infinite helical chain of alternating (o-C6F4Hg)3 molecules and thiocyanate anions. Every SCN− ion in the complex is bonded to the mercury atoms of two neighbouring molecules of the macrocycle through the sulphur atom and forms with each of these molecules two relatively short Hg … S bonds and one considerably longer Hg … S bond.

Crown compounds for anions. A new approach to the description of chemical bonds in the complexes of halide anions with polymercury-containing macrocycles

The nature of chemical bonds between halide anions and polymercury-containing macrocycles has been investigated. For this purpose, calculations of the complexes of halide anions with cyclic trimeric o-phenylenemercury (o-C6H4Hg)3, cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3, cyclic pentameric perfluoroisopropylidenemercury [(CF3)2CHg]5 and some of their simpler hypothetical analogs have been carried out by the MNDO method. Complexes of the half-sandwich [L—X]−, bipyramidal [X—L—X]2− and sandwich [L—X—L]− (X = Hal, L = mercury-containing macrocycle) types have been calculated. It has been established that a uniform description of the bonding in such complexes, not depending on the number of Hg atoms in the macrocycle, can be reached within the framework of the concept of generalized chemical bonds.

Crown compounds for anions. Spectroscopic and theoretical studies of complexation of borohydride anions with cyclic trimeric perfluoro-o-phenylenemercury

It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 (1) is capable of binding borohydride anions in THF and 1,2-dichloroethane solutions to form complexes {[(o-C6F4Hg)3](BH4)2}2− (2) and {[(o-C6F4Hg)3]2(BH4)}− (3). According to the IR data, complex 2 contains both terminal and coordinated B–H bonds while all four B–H bonds of the BH4− ion are coordinated with the mercury atoms in complex 3. The use of NMR spectroscopy provided the identification of one more complex of 1 with BH4−, which can be formulated as {[(o-C6F4Hg)3](BH4)}− (4). The stability constants of complexes 2 and 3 have been determined by IR spectroscopy. Quantum-chemical calculations of 2–4 by the AM1 method suggest that the complexes have the unusual bipyramidal, sandwich and half-sandwich structures, respectively. In contrast to 1, the interaction of (C6F5)2Hg with BH4− anions in THF gives a single complex {[(C6F5)2Hg](BH4)}− (5) independently of the reagent ratio. This complex is much less stable than 2 and 3.

Coordination chemistry of macrocyclic multidentate Lewis acids. Synthesis and structures of complexes of cyclic trimeric perfluoro-o-phenylenemercury with N,N-dimethylacetamide and n-butyronitrile

Cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4Hg)3 readily reacts with N,N-dimethylacetamide and n-butyronitrile to form the complexes {[(o-C6F4Hg)3](MeCONMe2)2} and {[(o-C6F4Hg)3](PrnCN)}, respectively. According to X-ray diffraction data, the amide ligands are located above and below the plane of the macrocycle, each being coordinated to all Hg atoms of the macrocycle through the O atom. The nitrile ligand is bound to the macrocycle through the N atom, all Hg atoms being also involved in this bonding.