Georgy A. Domrachev

FERROUS TRIS( TRIMETHYLSILYL) SILANOLATES : SYNTHESIS, STRUCTURE, REACTIVITY AND THERMAL DECOMPOSITION

Abstract Reaction of FeBr2 with 3 equiv. of sodium tris(trimethylsilyl)silanolate (1) in DME affords the ate-complex {(Me3Si)3SiOFe[μ-OSi(SiMe3)]2Na(DME)} (2). X-ray studies have shown the Fe atom in 2 is bonded to three O atoms of OSi(SiMe3)3 groups, two O atoms are connecting as a μ-bridge the Fe[OSi(SiMe3)3]3] unit with the Na(DME) group. The FeO3 core is slightly non-planar: the deviation of the Fe atom from the O3 plane is 0.08A. The four-member Fe(μ-O)2Na cycle is also non-planar: the dihedral angle between the Fe(μ-O)2 and the (μ-O)2Na planes is 31.0°. The bridging and terminal FeO distances are 1.840(2) and 1.894(2), 1.910(2) A, respectively. The average SiSi and SiC distances are 2.358(8) A and 1.873(8) A. Interaction of FeBr2 with two equiv. of 1 in THF followed by treatment with pyridine yields the adduct, [(Me3Si)3SiO]2Fe(Py)2 (3). The Mossbauer spectrum of complex 2 at 295 K consists of a single doublet with isomer shift 0.60(1) mm/s and quadrupole splitting 0.90(3) mm/s. The corresponding parameters of 3 are as follows: isomer shift, 1.08(1) mm/s, and quadrupole splitting, 2.12(2) mm/s. Molecular oxygen is easily incorporated into the SiSi bonds of compounds 2 and 3 by activation at the iron (II) center. Reaction of 2 with 1 equiv. of tetracyanoethylene leads to iron (III) silanolate, [(Me3Si)3SiO]3Fe (4) and the anion-radical salt, Na +TCNE−. Slow thermolysis of 2 and 3 yields (Me3Si)2SiOSiMe3 and (Me3Si)4Si as well as polyferrsiloxane with MW ∼ 3500. Fast thermolysis results in formation of α-Fe and a complicated mixture of oligosiloxanes.

Transition metal NMR chemical shifts and polarizability effect in organometallic complexes

The literature data on substituent influence on the 51V, 55Mn, 57Fe, 59Co, 61Ni, 95Mo, 103Rh, 183W, 187Os and 195Pt NMR chemical shifts (δ) and on J (M, P; M = Mn, Fe, Mo, Rh, W, Os) coupling constants have been analyzed for 30 series of the organometallic complexes. It has been established for the first time that the δ and J values depend on the inductive, resonance and polarizability effects of substituents. The polarizability effect is caused by the partial charge on the central M atom. The contribution of this effect ranges from 3 to 86%. Copyright

TRIS(TRIMETHYLSILYL)SILOXIDES OF GADOLINIUM AND LANTHANUM : SYNTHESIS, STRUCTURE AND SOME PROPERTIES

A series of gadolinium and lanthanum siloxide complexes of empirical formula [(Me 3 Si) 3 SiO] 3 Ln(L n ) {Ln=Gd, L n =(THF) 2 ( 1 ), (MeCN) 2 ( 2 ), [N(C 2 H 4 ) 3 N] 2 ( 3 ), (4,4′-dipyridyl) 2 ( 4 ), (4,4′-dipyridyl) 1 ( 5 ); Ln=La, L n =(THF) 4 ( 6 )} have been prepared by the reaction of [(Me 3 Si) 2 N] 3 Ln (Ln=Gd, La) with (Me 3 Si) 3 SiOH or LnCl 3 (Ln=Gd) with (Me 3 Si) 3 SiONa in various solvents. Both [(Me 3 Si) 3 SiO] 3 Gd(THF) 2 ( 1 ) and [(Me 3 Si) 3 SiO] 3 Gd[N(C 2 H 4 ) 3 N] 2 ( 3 ) have been characterized by X-ray crystallography. The Gd in both 1 and 3 has a trigonal-bipyramidal environment with three O atoms in equatorial and two B atoms (B=O in 1 and N in 3 ) in axial positions. The symmetries of molecules of 1 and 3 are C 3 i and C 3 h , respectively. The GdOSi angles and the GdO distances are 161.2(3)°, 2.142(7) A in 1 and 165.4(2)°, 2.161(4) A in 3 . The GdO(THF) distances in 1 are 2.448(9), 2.314(18) and the GdN distance in 3 is 2.520(6) A. Gadolinium complex ( 1 ) and the lanthanum complex ( 6 ) readily absorb one and three moles of CO 2 , respectively to form the corresponding carbonates. Compounds 1 and 6 sublime at 205°C in vacuo to form homoleptic siloxides. A subsequent rise in temperature results in their decomposition to give polylanthanosiloxanes, and (Me 3 Si) 3 SiOH as the only volatile product up to 300°C.

Synthesis of bis(arene)chromium compounds from 1,4-diphenylbutane and chromium vapour

Abstract Bridged dibenzenechromium 1,1′-tetramethylenedibenzenechromium (I) together with bis(1,4-diphenylbutane)chromium (II) and bis-1,4[1′-(δ-phenylbutano)dibenzenechromo]butane (III) were synthesized from the reaction of 1,4-diphenylbutane with chromium vapour.

Cobalt(II) and iron(II) tris(trimethylsilyl)siloxides: synthesis, structure and reactivity

Abstract A series of cobalt(II) and iron(II) siloxide complexes, [(Me3Si)3SiO]2M(Ln) {M=Co, Ln=none (1), (THF) (3), (THF)2 (4), (DME) (5), (MeCN)2 (6), (PhCN)2 (7), (2,2′-dipyridyl) (8), 4,4′-dipyridyl (9), (Ph3P)2 (10); M=Fe, Ln=none (2), (2,2′-dipyridyl) (11) were prepared by the reaction of metal silylamides [(Me3Si)2N]2M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with two [(Me3Si)3SiO]2Co units bonded via the two μ2-O atoms. The central [Co(μ2-O)]2 cycle has a ‘butterfly shape’ being bent along the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The μ2-bridging and terminal CoO distances are 1.945(7)–1.963(7) and 1.781(8), 1.793(7) A, respectively. The Co⋯Co distance in 1 is relatively short, 2.735(2) A. However, the high value of magnetic moment (6.0 μB) of compound 1 indicates the absence of a direct interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2′-dipyridyl and two terminal OSi(SiMe3)3 groups and has a distorted tetrahedral environment. The FeN(1), FeN(2) and FeO(1), FeO(2) distances in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) A, respectively. Addition of one equivalent of PhCCH to 7 results in the substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC2)CoOSi(SiMe3)3}2. Subsequent addition of PhC2H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and 4 in solution.

Degenerate four-wave mixing measurements of the ?(3) non-linear optical properties of poly(arylene-ethynylenesilylene)s

The third-order optical non-linearity in solution of a series of poly(arylene-ethynylenesilylene)s containing a variety of backbone arylene groups and substituents at silicon has been studied by using the degenerate four-wave mixing technique at 1064 nm with a 6 ns pulse duration. Thermal grating effects may be neglected under the experimental set-ups employed. The results obtained are greater by more than two orders of magnitude than those previously measured for some of the polymers using the Z-scan technique at the same wavelength. The electronic contribution to the fast non-linearity is greater than the nuclear (orientational) contribution by a factor of at least 4. The presence of a single 8-(dimethylamino)naphthyl ligand at silicon affording pentacoordination has a beneficial effect on the X (3) properties. The high X (3) properties of the polymers (e.g. [Re(X (3) )]=9.5 × 10 -12 esu for [-C≡C-SiPh 2 -C≡C - (1,4-C 6 H 4 )-] n in chloroform [5 g] l -1 ]) confirm the presence of extensive through-Si conjugation along the backbone.

Synthesis of dibenzenechromocenophanes from α,ω-diphenylalkanes and chromium vapour

Abstract Complexes of the composition [C 6 H 5 (CH 2 ) n C 6 H 5 ]Cr having the structure of [4]- and [5]-dibenzenechromocenophanes, [C 6 ]H 5 (CH 2 ) n C 6 H 5 ] 2 Cr, and [C 6 H 5 (CH 2 ) 4 C 6 H 5 ] 3 Cr 2 ( n = 4, 5) have been isolated from reactions of chromium vapour with 1,4-diphenylbutane and 1,5-diphenylpentane.

Chromium-containing organometallic nanomaterials for non-linear optics

Novel non-linear optical polymeric film-producing nanocomposites based on bis(arene)chromium complexes incorporated into a CN-containing matrix have been developed. Polymeric nanocomposite precursors were prepared by the reaction of Cr(EtnC6H6−n)2 (n = 1,2,3) with CN-containing vinyl monomers (acrylonitrile, crotononitrile or ethyl 2-cyanopropenoate). Extraordinarily high third-order non-linear optical susceptibilities of the ultra-fast electronic type have been demonstrated at various wavelengths for polymer films prepared from these composites by using the Z-scan technique and the spectrally-resolved two-beam coupling method. A notable electro-optical response of the composite with an essential contribution of orientational effects was established. The electron-diffraction pattern in films and the presence of a non-zero electro-optical coefficient in the absence of an external poling field indicate the formation of self-organized structures. In CrPAN and [CrPAN]+TCNE−, a single Cr–C distance was found in the EXAFS data refinement, showing that the arene rings are parallel and symmetric as in bis(benzene)chromium. The Cr–C distances in these two materials are very similar to the 2.13 A in bis(benzene)chromium. In [CrPAN]+OH−, more than one metal–carbon distance was resolved, showing either that the two arene rings are at different distances from the metal, or that they are tilted rather than parallel.

The role of carbon and metal in self-assembly of the iron-carbon system at various component ratios

The problem of self-assembly in a metal-carbon system under dynamic conditions (equilibrium and nonequilibrium) is considered using the iron-carbon system as an example. It is proved theoretically and experimentally that the ratio of the components of the system affects the possibility of carbon self-assembly with the formation of fractal iron structures and of metal self-assembly with the participation of polyhapto derivatives of iron and the formation of fullerene-like carbon structures.

One-step synthesis of bisarenechromium complexes from ethyl esters of phenylacetic and phenylpropionic acids

The low-temperature cocondensation of chromium vapors with the vapors of the ethyl esters of phenyl-acetic andβ-phenylpropionic acid gave the corresponding bisarenechromium complexes.