Irina V. Pisareva

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.

Unexpected formation of clusters with a nortricyclene-containing carborane ligand, 1-(η6-arene)-3-(C7H9CH2O)-isonido-1,2,4-RuC2B8H9, in the reaction of 1,1,3-(PPh3)3-1-H-1,2,4-RuC2B8H9 with 2-(hydroxymethyl)norbornadiene in arene solvents

Heating of 1,1,3-(PPh3)3-1-H-1,2,4-RuC2B8H9 with 2-(hydroxymethyl)bicyclo[2.2.1]hepta-2,5-diene in arene solvents (benzene, toluene, or mesitylene) unexpectedly afforded the ruthenium arene complexes 1-(η6-arene)-3-(C7H9CH2O)-isonido-1,2,4-RuC2B8H9 containing the nortricyclene fragment in the carborane ligand.

Synthesis, structure and reactivity of a novel monocarbon hydridorhodacarborane closo-2,2-(Ph3P)2-2-H-1-(Me3N)-2,1-RhCB10H10 molecular structure of 16-electron closo-2-(Ph3P)-2-Cl-1-(Me3N)-2,1-RhCB10H10 and closely related 18-electron closo-3,3-(Ph3P)2-3-Cl-3,1,2-RhC2B9H11

Abstract A novel 12-vertex monocarbon hydridorhodacarborane closo -2,2-(Ph 3 P) 2 -2- H -1-(Me 3 N)-2,1-RhCB 10 H 10 1 has been synthesized by the reaction of Rh(PPh 3 ) 3 Cl ( 2 ) with nido -B 10 H 12 CNMe 3 ( 3 ) under alkaline conditions. At low temperature 1 exists as a mixture of two preferred conformers in solution, both having C S symmetry, in accord with the hindered rotation of the (Ph 3 P) 2 RhH vertex with respect to the CB 4 face of the monocarbon carborane cage. Complex 1 readily reacts with chlorine-containing reagents to form mononuclear 16-electron closo -2-(Ph 3 P)-2-Cl-1-(Me 3 N)-2,1-RhCB 10 H 10 ( 5 ), whose structure was unambiguously confirmed by an X-ray diffraction study. The results of an X-ray diffraction study of the closely related dicarbon carborane derivative closo -3,3-(Ph 3 P) 2 -3-Cl-3,1,2-RhC 2 B 9 H 11 ( 10 ), prepared from closo -3,3-(Ph 3 P) 2 -3- H -3,1,2-RhC 2 B 9 H 11 by analogy with 5 , are also reported.

Synthesis, solution behaviour and molecular structures of 16-electron closo-2-(Ph3P)-1-N,2-[μ-(η2-CH2CHCh2)]-1-N-(σ-CH2CHCH2)-2,1- RhCB10H10, the first η2-olefinic monocarbon metallacarborane

The first η 2 -olefinic monocarbon metallacarbone closo -2-(Ph 3 P)-1-N,2-[ μ -( η 2 -CH 2 CHCh 2 )]-1-N-( σ -CH 2 CHCH 2 )-2,1- RhCB 10 H 10 has been prepared by the reaction of the dimeric anion {[Ph 3 PRhB 10 H 10 CNH 2 ] 2 -μ-H} − [PPN] + with allyl bromide and characterized by a combination of spectroscopic methods and a single-crystal X-ray diffraction study. The variable temperature 1 H and 13 C NMR studies revealed the fluxional behavior of the η 2 -olefinic complex in CD 2 Cl 2 solution which is associated with the allyl side-chain exchange process.

Synthesis and some reactions of the stable carbocations stabilized by the 1-[closo-3,3,3-(CO)3-3,l,2-ReC2B9H10]−group. The structure of closo-3,3,3-(CO)3-3,1,2-ReC2B9H10−-1-C+Me2

Abstract The stable carbenium cations in the zwitterionic complexes closo-3,3,3-(CO)3- 3,1,2-ReC2B9 H 10-1- C +RR′ (R = R′ = H; R = H, R′ = Me; R = R′ = Me) have been prepared by protonation of closo-3,3,3-(CO)3-3,1,2-ReC2B9H10-1-CH2OR (R = H, Me) and closo-3,3,3-(CO)3-3,l,2-ReC2B9H10-1-CRCH2 (R=H, Me). Some of the reactions of the zwitterions with neutral and charged nucleophilic reagents have been studied. The crystal and molecular structure of closo-3,3,3-(CO)3-3,1,2-ReC2B9 H 10- 1- C + Me2 has been established. It is shown that the carbocationic centre in these zwitterions is stabilized by direct ReC interaction.

Separation of racemiccloso-3,3-(η3,2-norbornadienyl)rhodacarboranes into enantiomers by HPLC on chiral stationary phasesinto enantiomers by HPLC on chiral stationary phases

Racemiccloso-rhodacarboranes,vis.closo-(η3,2-C7H3-2-CR21)-1-R2-2-R3-3,1,2-RhC2B9H9 (R1=R2=R3=H; R1=H, R2=R3=Me; R1=R2=R3=Me) and (closo-2,2-(η3,2-C7H7-2-CH2)-2,1,7-RhC2B9H11), were successfully separated into enantiomers by high-performance liquid chromatography (HPLC).

Synthesis and structural identification of 10-vertex closo-nickelacarborane with cage carbon atoms in unusual polyhedral positions

Many transition metal metallacarboranes, in parti cular, based on radioactive isotopes, are applied as diag nostic tracers in medicine.1 In addition, the extensive use of metallacarborane catalysts in the stereoselective syn thesis of, for example, drugs2 or precursors of biologically active compounds,3 as well as in the design of new immo bilized homogeneous catalytic systems4 promotes the fur ther development of this area of chemistry. In this study, we report the synthesis of new 10 vertex closo nickelacarborane [2,2 (PPh3)2 2,1,3 closo NiC2B7H9] (1) containing carbon atoms in the 1,3 posi tions of the metallacarborane. This is the first example of such an arrangement of cage carbon atoms. Complex 1 was synthesized as air stable yellow crystals in 52% yield by the reaction of NiCl2(PPh3)2 5 with non icosahedral carborane [5,6 nido C2B8H12] under gentle (40 min) re flux in methanol. It should be noted that the coordination of the 10 vertex carborane [5,6 nido C2B8H12] to deriva tives of transition metals in other solvents (CH2Cl2, CDCl3, Ar solvents) in the presence of N,N,N ́,N ́ tetra methyl 1,8 diaminonaphthalene (tmnda) as a base ge nerally gives rise to 11 vertex clusters with isonido geo metry.6 In the case under consideration, the reaction is more complicated and is accompanied by the mild low temperature monodeboronation of the intermediate 11 vertex complex, which loses one BH vertex via the intramolecular activation according to Scheme 1. We failed to detect the 11 vertex intermediate by NMR monitoring of the reaction at low temperature. The 11B/11B{1H} NMR spectra in CD3OD at 0 C show only signals of the starting {C2B8} carborane, complex 1, and B(OCD3)3. At lower temperatures, 11B/11B{1H} NMR spectra are non informative because of strong broadening of signals (quadrupole relaxation of 11B nuclei).7 These data suggest that the deboronation of the 11 vertex com plex occurs rather rapidly and, apparently, cannot be de tected on the NMR time scale.

Highly efficient synthesis of trimethylarsine

A convenient, highly efficient, and environmentally safe procedure for the preparation of trimethylarsine was proposed. A quantitative yield of this compound in the reaction of As2O3 with AIMe3 was attained for the first time by using mechanochemical activation of the process.