摘要:

AbstractStructural results of X‐ray investigations on group VIa metal carbyne complexes are described and the influences of different substituents on the metal carbon triple bond are discussed. From the M‐Ccarbynedistances metal triple bond radii are deri

ISSN:0021-2148    

DOI:10.1002/ijch.197600027

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe structure of nitrosyltris(triphenylphosphine)rhodium, Rh(NO)‐(P(C6H5)3)3, has been determined from three‐dimensional X‐ray data. The compound crystallizes in the space groupP3 of the trigonal system with three molecules in a unit cell of dimensionsa= 19.057(4) andc= 10.799(2)Å. Least‐squares refinement of the 162 variables has led to a value of the conventional R index (on F) of 0.052 for the 5456 independent reflections having F2o>3 σ (F2o). There are three independent molecules in the unit cell, one‐third of each being unique. The best first approximation is to describe the complex as a tetrahedral Rh( ‐I) complex; average parameters: Rh—P = 2.350(3), Rh—N = 1.759(13), N—O = 1.27(2) Å, P—Rh—P = 102.2(6), N—Rh—P = 116.0(5), Rh—N—O = 156.7(26)°.The nitrosyl groups are disordered about the threefold axes. The structure is compared with other metal nitrosyl phosphine complexes and the me

ISSN:0021-2148    

DOI:10.1002/ijch.197600028

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe crystal and molecular structures of the two title compounds have been determined. The two isoelectronic species are almost isostructural, with only small deviations in bond angles, distances and planarity of the ring systems. The results are compared with those of analogous nickel(II) and gallium(III) complexes, where both square planar and tetrahedral ligand arrangements are present, respectively. The typical ligand properties of the new double ylide chelates can thus be derived.

ISSN:0021-2148    

DOI:10.1002/ijch.197600029

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe crystal and molecular structure of the compound having the composition Re2Br2(CO)6S2(CH3)2was determined from three‐dimensional X‐ray diffraction data collected by automated counter methods. The substrate crystallises in the space group P21/c with cell constantsa= 6.798(2),b= 14.493(5),c= 17.028(6) Å and β = 94.70(3)°, V = 1673.0 Å3and Z = 4 molecules/unit cell for dcalc. 3.161g cm−3; dobe= 3.15(2)g cm−3. The dimeric molecules consist of two hexacoordinated Re(I) cations surrounded by three carbonyl groups in afacarrangement with one occupying an axial position and two equatorial ones. The other two axial positions of the dimer are occupied by the two sulphur atoms of the bridging dimethyldisulphide ligand. The (OC)2ReBr2(OC)2fragment is not planar, instead, there is a folding of the molecule along the Br–Br′ vector, such that the two ReBr2fragments make an angle of 28.0°. The Re–CO fragments are normal and compare well in structural parameters with other studied elsewhere; the same is true of the Re–Br and of the Re–S bonds. The changes introduced in the dimethyldisulphide ligand are principally in the S–S distance, the C–S–S angle and the C–S–S–C torsional angle, which are noticeably affected by bonding to the Re(I) cation.Spectral data for the Re2Br2(CO)6S2R2complexes (R=Me, Ph, C6H4–pMe) have been collected in solution. The equilibrium (R = Me, Ph)Re2Br2(CO)6S2R2+ 2 THF ⇋ Re2Br2(CO)6(THF)2+ S2R2has been found to be strongly affected by the nature of the group R. In spite of a larger variation of the torsional angle when dimethyldisulfide leaves the coordination sphere of the metal, the displacement of the S2Me2ligand by tetrahydrofuran is a less favourable process than the corresponding reaction with Re2Br2(CO)6S2Ph2. If solvation effects by THF can be ignored, the conclusion is that the Re2S2Me2system is inherently stronger than Re2S2Ph2. This conclusion could not easily be drawn from a conside

ISSN:0021-2148    

DOI:10.1002/ijch.197600030

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe X‐ray photoelectron spectra of a series of thiocyanato and isothiocyanato complexes of the transition metals have been recorded. Carbon 1st, nitrogen 1s and sulfur 2p binding energies were measured in order to establish whether there was any clear correlation with the mode of thiocyanate bonding. Complexes which were studied included those possessing M–NCS, M–SCN and M–NCS–M units. In addition, several species were investigated which contained two different thiocyanate environments within the same molecule. These were the ionic complexes [Cu(tren)(NCS)]SCN and [Cu(trien)(SCN)]SCN, where tren = tris(2‐aminoethyl)amine and trien = triethylenetetramine, and Pd(dppe)(NCS)(SCN), where dppe = 1,2‐bis(diphenylphosphino)ethane. The latter complex contains both N‐ and S‐bound thiocyanate. Within the range of complexes studied, the S 2p energies of M–NCS, M–SCN and SCN−differ at most by a few tenths of an electron volt. This indicates that the XPS technique will not usually permit a ready distinction between these different bonding modes in most tra

ISSN:0021-2148    

DOI:10.1002/ijch.197600031

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractIt has been shown conclusively by the observation of57Fe–13C coupling (J = 8.3 Hz) that in Fe3(CO)12the scrambling is intramolecular and that all of the CO groups have equal access to all three of the iron atoms. This result is fully in accord with the scrambling mechanism proposed in an earlier paper from this laboratory. We have found that for axially substituted amine derivatives of iron pentacarbonyl, AmFe(CO)4, the activation energy for CO scrambling is raised from the extremely low value (ca. 2 kcal mol−1) characteristic of Fe(CO)5to a range (ca. 5.0–5.5 kcal mol−1) such that the coalescence temperatures are at, or very near, the threshold (ca. – 150°C) of experimental observation. The crystal and molecular structures of (1,2‐C4H4N2)Fe(CO)4are also reported. The molecular structure is very similar to those of the (C5H5N)Fe(CO)4and (1,4‐C4H4N2)Fe(CO)4compounds. The space group is P21/n with unit cell dimensions a = 6.487(1)Å, b = 11.331(3)Å, c = 14.226(3)Å, β = 107.85(2)Å, V = 995.3(4)Å3. Finally, in the compound (C9H8O)Fe(CO)3, where C9H8O is derived from barbaralone, the scrambling of the three CO groups proceeds in a concerted manner with an activation energy of 16.5(3) kcal mol−1. The available data for CO scrambling in M(CO)3moieties in general is su

ISSN:0021-2148    

DOI:10.1002/ijch.197600032

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

ISSN:0021-2148    

DOI:10.1002/ijch.197600033

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractOnly a limited number of the many possible networks of planar sp2carbon atoms are sufficiently compact to bond entirely to a single transition metal atom as perhapto ligands. These networks, which are conveniently called elplacarnets, correspond to the vertices of a tree. The edges of this elplacarnet tree correspond to four different types of growth processes which occur at vertices of degree 1, at vertices of degree 2, in rings, and across an edge connecting two vertices of degree 1. For the middle transition metals (e.g. chromium through cobalt) the elplacarnet tree contains 13 vertices and 12 edges. Some applications of the elplacarnet tree in understanding the extensive varieties of structures of transition metal organometallic complexes containing unsaturated hydrocarbon ligands are summarized.

ISSN:0021-2148    

DOI:10.1002/ijch.197600034

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe more common Ligand Field parameterizations have been reviewed and the conditions under which the various schemes are equivalent have been discussed. The relations among equivalent sets of parameters have been tabulated. Attempts to give a physical meaning to the parameters as they derive from the characterization of various physical properties of related compounds have been critically reviewed.

ISSN:0021-2148    

DOI:10.1002/ijch.197600035

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractElectron transfer quenching of excited states can lead to separated redox products for which back electron transfer can be highly favored. Application of flash photolysis leads to a relaxation technique in which a system at equilibrium is perturbed by separate excitation‐quenching steps. The rates of several electron transfer reactions have been studied using the technique based on redox quenching of the CT excited state Ru(bpy)2+−3. Quenching and back electron transfer has also been observed for a series of excited states including examples of CT(Ru(phen)2+3, etc), π ‐ π * (Pd(OEP)), and f‐f(Eu(phen)3+3) states. In recent work, even non‐emitting excited states have been shown to be quenched by electron transfer which suggests that the technique may have broad applicability. In properly designed systems containing more than one redox reagent, the quenching and back electron transfer steps can be separated and reactions have been studied which are driven photocatalytically by excited states like Ru(bpy)2+−3. A modification of the technique has been used to estimate the self‐exchange rate for the Ru(bpy)3+/2+3couple and to measure rates of electron transfer for a series of systems where the rates measured do not invo

ISSN:0021-2148    

DOI:10.1002/ijch.197600036

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY