Peter S. White

Preparation and crystal structures of (S7I)4S4(AsF6)6 and S4(AsF6)2·0.6SO2; a convenient synthesis of hexafluoroarsenate salts of chalcogen homoatomic cations

The oxidising ability of AsF5 is greatly enhanced by traces of bromine, and in its presence S4(AsF6)2·xSO2, (x⩽ 1) was prepared quantitatively from AsF5 and S8 in SO2; the X-ray structures of S4(AsF6)2·0.6SO2, and (S7I)4S4(AsF6)6 confirm the square planar geometry of S42+ in both salts, the former having a sulphur–sulphur bond distance of 2·014(4) and the latter of 1·98(1)A.

The reaction of scandium trifluoride with cyclopentadienyl salts and the crystal and molecular structure of the trimer of fluorodicyclopentadienylscandium

Abstract The reaction of ScF3 with (C5H5)2Mg gives a mixture of (C5H5)3Sc and (η5-C5H5)2ScF, not pure (C5H5)3Sc as reported previously. The same mixture is obtained on treating ScF3 with C5H5Na in tetrahydrofuran. The two products can be separated since (η-C5H5)2ScF is soluble in toluene whereas (C5H5)3Sc is not. The structure of (η-C5H5)2ScF shows it to be trimeric with a planar (ScF)3 ring (average ScF distance 2.046(8) A, FScF and ScFSc angles 86.5(3) and 153.4(4)°, respectively). Crystal data: monoclinic, Cc, a 17.019(8), b 15.273(7), c 10.359(8) A, β 92.33(5)°, Z = 4; Mo-Kα radiation, R = 0.076 for 1238 observed reflections and 325 variables.

Conformational variability in π-complexes of hexaethylbenzene. Crystal and molecular structure of [(C6Et6)(C5H5)Fe]BPh4

Abstract [(Hexaethylbenzene)Fe(C 5 H 5 )][BPh 4 ], [ 1 BPh 4 ], crystallizes in the monoclinic space group, P 2 1 / C , with a 15.7288(23), b 15.4411(14), c 16.3356(20)A, β 107.972(10)° and D calc 1.208 g cm −3 for Z = 4. Least-squares refinement gave a conventional R value of 0.047 for 2881 independent observed reflections. The structure reveals that the complexed hexaethylbenzene moiety in 1 adopts a conformation such that five ethyl groups point away from the iron atom (distal) and only one is directed towards the iron atom (proximal). This observation contrasts with an earlier crystallographic study conducted ( 1 PF 6 ), in which the hexaethylbenzene ligand was shown to adopt a four distal/two proximal conformation. In other ways the cations in 1 BPh 4 and 1 PF 6 are almost identical, thereby suggesting that even subtle packing effects may influence the conformation adopted by sterically crowded ligands such as hexaethylbenzene.

The crystal and molecular structure of μ-oxalatobis[di(η5-cyclopentadienyl)titanium]

Abstract μ-Oxalatobis[di-(η 5 -cyclopentadienyl)titanium], [μ-(C 2 O 4 ) {(η 5 -C 5 H 5 ) 2 Ti} 2 ], 0.5 (C 2 H 5 ) 2 O crystallises in the orthorhombic space group Pbcn with a 17.228(13), b 12.224(13), c 30.309(23) A and Z = 12. The final R was 0.061 ( R w 0.104). The oxalato group acts as a planar tetradentate bridging ligand, with the Ti atoms displaced in a cis fashion cut of the C 2 O 4 2− plane. The reason for this displacement is analysed in terms of σ and π interaction between the metal and ligand, and steric contacts between the Cp rings. Comparison with the iso-electronic [μ-{C 2 (N(C 6 H 4 CH 3 - p )) 4 } {(η 5 -C 5 H 5 ) 2 Ti} 2 ] is made.

Preparation and crystal structure of S2I42+(AsF6–)2 containing the distorted right triangular prismatic disulphur tetraiodine(2+) cation and a disulphur unit of bond order greater than two

S2I42+(AsF6–)2 has been prepared and its crystal structure determined in which the S2I42+ cation was found to have a distorted right triangular prismatic structure, with one S2 and two I2 units joined by weak sulphur–iodine bonds; the sulphur–sulphur bond distance is the shortest reported in an isolated compound, and is indicative of the presence of a 3pπ–3pπ bond and a bond order greater than two.

Crystal and molecular structure of (η5-1,3,5-trimethyl-6- phenylcyclohexadienyl)(η5-cyclopentadienyl)iron, a mixed full sandwich iron(II) complex

Abstract (η 5 -1,3,5-trimethyl-6-phenylcyclohexadienyl)(η 5 -cyclopentadienyl)Fe ( 9 ) was synthesized via reaction of phenyllithium with [(cyclopentadienyl)(mesitylene)Fe][PF 6 ]. 9 crystallized from hexanes in the monoclinic space group P 2 1 / n with a 8.5703(5), b 8.5283(9), c 21.8436(23) A, β 93.868(6)° and D calc 1.327 g cm −3 for Z = 4. Least-squares refinement gave a conventional R value of 0.035 for 2046 independent observed reflections. The structure reveals that the phenyl moiety added in the expected exo fashion and that the Fe-ring distances are statistically identical, averaging 2.059(3) and 2.06(3) A for the cyclopentadienyl and cyclohexadienyl moieties, respectively. A comparison with other mixed iron(II) full-sandwich complexes is made in an attempt to determine relative π-back bonding abilities of the four isoelectronic π-ligands: arene, cyclopentadienyl, pentadienyl, and cyclohexadienyl.

Preparation and X-ray crystal structure of µ-iodo-bis(4-iodo-cyclo-hepta-sulphur) tris(hexafluoroantimonate)–bis(arsenic trifluoride), [(S7I)2I]3+[SbF6]–3·2AsF3

The reaction of S8, I2, and SbF5 in the appropriate ratios in AsF3 gave essentially quantitative yields of S14I3(SbF6)3·2AsF3, shown by X-ray crystallography to contain the novel cation [(S7I)2I]3+, consisting of two [S7I]+ fragments bridged by a linear S–I–S bond.

Trimethylaluminum mediated halomethylation of [(arene)2Fe]2+ cations

Abstract The arene salts [(arene) 2 Fe](PF 6 ) 2 (arene = mesitylene 1a , and hexamethylbenzene, 1c ) react readily with AlMe 3 in dichloromethane or dibromomethane to produce the novel exo -halomethyl-η 5 -cyclohexadienyl salts [(η 5 - exo -CH 2 XC 6 H 3 Me 3 )(η 6 -C 6 H 3 Me 3 )Fe]PF 6 (X = Cl, 2d ; X = Br, 2e ) and [(η 5 - exo -CH 2 XC 6 Me 6 )(η 6 -C 6 Me 6 )Fe]PF 6 (X = Cl, 2f ; X = Br, 2g ) which have been characterized spectroscopically and, in the case of 2f , crystallographically.

Preparation and X-ray crystal-structure determinations of structural isomers of ferrocenyl-substituted dihydrofurans

The reaction of tris(3-iodopentane-2,4-dionato)cobalt(III) with vinylferrocene in the presence of triphenylphosphine and a catalytic amount of PdII produced two structural isomers. The characterisation of these isomers, 2- and 3-ferrocenyl-4-acetyl-2,3-dihydro-5-methylfuran [(B) and (C), respectively] is described. Their structures have been determined by single-crystal X-ray diffractometry: (B) is orthorhombic, space group Pbca with a= 9.821 (2), b= 10.414(4), c= 27.761(6)A, final R= 0.031, R′= 0.050 for 1 706 reflections; (C) is monoclinic, space group P21/c with a= 9.692(1), b= 7.678(5), c= 19.082(3)A, β= 97.76(1)°, final R= 0.031, R′= 0.048 for 1 641 reflections.

The preparation, characterization in solution of the 7 π radical 1,2,4-triseleno-3, 5-diazolylium, and the 6π 1,2,4-triseleno-3-5-diazolium (2+) cations, and the X-ray crystal structures of (SeNSeNSe)2(AsF6)2 and SeNSeNSe(AsF6)2 containing the first stable binary selenium-nitrogen species

Abstract Numerous binary sulphur-nitrogen species have been prepared and structurally characterized. Analogous Selenium-nitrogen compounds are restricted to Se4N4 which is even more thermodynamically and kinetically unstable than S4N4. As a result for a search for SeNSe+ [cf. SNS+, which has a very extensive chemistry [1]] we prepared ( SeNSeNS e)2(AsF6)2 and SeNSeNS e(AsF6)2 by a variety of routes, containing the first reported thermally stable binary selenium nitrogen species including the indefinitely stable 7π radical cation SeNSeNS e+.. These salts were fully characterized both in the solid state [X-ray], and in solution, [ SeNSeNS e+., e.s.r.; SeNSeNS e2+, Raman, 14N, 77Se N.M.R.]. Interestingly SeNSeNS e2+ retains its ring structure in solution in contrast to SNSNS 2+, in solid S3N2(AsF6)2, which dissociates to NS+ and SNS+ [2].