Anthony A. Chalmers

Sulphur-containing metal complexes: III. Tetracarbonyl(carbene—thio) complexes of chromium(0) and tungsten(0)

Abstract Reaction of α-lithiated sulphides with (CO) 6 Cr and (CO) 6 W followed by alkylation with (Et 3 O)BF 4 give the new series of neutral carbene-thiometal chelates of general formulae cis -(CO) 4 MC(OEt)[C(OH)C(S R 1 )R 2 ] (I) and cis -(CO) 4 MC(OEt)[C(OEt)C(S R 1 )R 2 ] (II). This route probably involves carbonyl insertion into a metalcarbene bond. Complexes of type II can also be prepared by treatment of pentacarbonyl(thio)metal complexes, (CO) 5 MS(CH 2 R 2 )R 1 , with BuLi, and subsequent alkylation. It is suggested that the second method proceeds via the generation of an anion α to a coordinated sulphur atom followed by a double ( cis-cis ) carbonylation.

Sulphur-containing metal complexes: X. Reactions of [Fe(CO)5] with ethylenetrithiocarbonate. Structure of [Fe3(Co)9{CS(CH2)2S}S] containing a μ-dithiocarbene ligand

Abstract Four different conversions were observed when a mixture of [Fe(CO)5] and ethylenetrithiocarbonate was irradiated with ultraviolet light in tetrahydrofuran: (i) the thione bond in the ligand was broken and the sulphur atom was incorporated into a cluster to produce [Fe3(CO)9(μ3-S)2], (I); (ii) cleavage of the two CS single bonds occurred and the S(CH2)2S moiety was used to stabilize the complex [Fe2(CO)6{μ-S(CH2)2S}], (II); (iii) the ligand exhibited significant charge redistribution during coordination, in the compound [Fe2(CO)6-{S CS(CH 2 ) 2 S }], (III) and finally, (iv) the thione bond was cleaved and both fragments were used by the metalcarbonyl to yield the major product, [Fe3(CO)9{μ3- CS(CH 2 ) 2 S }(μ3-S)], (IV). A single crystal X-ray study of IV revealed that a dithiocarbene ligand caps an open iron triangle by forming a methylene bridge between two iron atoms and links up with the third iron atom via a sulphur atom.

13C NMR of pterocarpans

13CNMR spectra of eight pterocarpans are reported Assignments are based on multiplicities and second-order features in off-resonance decoupled spectra and on chemical shifts in model compounds. Comparison of the degree of long-range (C, H) coupling in 1H-coupled spectra is found useful

Benzo[b]thiophenium S,C-ylides: Preparation, structure and comparison with thiophenium analogues

Abstract A series of new S,C-ylides derived from benzo[b]thiophene and β-dicarbonyldiazocompounds were prepared and characterised. NMR ( 1 H, 13 C) studies revealed that ylides substituted additionally at position 2 of the thiophene ring can exist as pairs of diastereoisomers, not interchangeable at room temperature. The slow exchange between two sites was attributed to the restricted rotation about the ylidic SC bond. The crystal structure determined for one ylide demonstrated different molecular environment for two parts of the β-dicarbonyl ylidic substituent with respect to the benzothiophene ring. The prepared ylides were found to be much less reactive than the previously studied thiophenium S,C-ylides.

Formation of a homoleptic unbridged metal–metal bonded isocyanide dimer of ruthenium(I) by metal–carbon bond cleavage in [Ru(1–2,5-η-C8H13)(CN-xylyl)4]PF6: the X-ray structure determination of [Ru2(CN-xylyl)10][BPh4]2

Refluxing [Ru(1–2,5-η-C8H13)(CN-xylyl)4]PF6 in [2H6]acetone gives C8H13D and [Ru2(CN-xylyl)10][PF6]2; an X-ray structure determination of [Ru2(CN-xylyl)10][BPh4]2 shows the cation to be an unbridged, metal–metal bonded dimer of ruthenium(I) containing eclipsed 2,6-dimethylphenyl isocyanide ligands.

η3-Allyruthenium(II) complexes as intermediates in substitution and isomerization of diene ligands; the dominant role of steric effects

The formation of [Ru(η3-C8H13)L3]PF6 as intermediates in the conversion of [RuH(cod)L3]PF6[cod = cyclo-octa-1,5-diene, L = PMe3, P(OMe)2Ph,PMe2Ph, P(OMe)Ph2, and P(OCH2CMe3)3] into [RuHL4(solvent)]PF6[L = P(OMe)Ph2 and P(OCH2CMe3)3] and [RuHL5]PF6[L = PMe3, P(OMe)2Ph and PMe2Ph] and cyclo-octa-1,3-diene, has been shown be dependent upon the size of L.

The X-ray structural characterization and solution dynamics of bis[(μ-2,6-dimethylphenylisocyanide)-(cyclopentadienyl)(2,6-dimethylphenylisocyanide)iron(I)]

Abstract The X-ray structure of trans-[{Fe(η5-C5H5)(CNC6H3Me2-2,6)2}2] (1a) and the solution dynamics of both cis- and trans-[{Fe(η5-C5H5)(CNC6H3Me2-2,6)2}2] have been studied. The trans-isomer of 1a crystallizes in the space group P21/n with a 14.588(4), b 8.811(2) and c 14.847(4) A, β 92.08(2)°. The molecule lies across a crystallographic centre of inversion with a trans arrangement of cyclopentadienyl ligands and a strictly planar bridging Fe2C2 ring. The FeFe bond lenght is 2.518(1) A and the bridging isocyanide ligands are symmetrically bonded to iron with a mean FeC(bridging) bond lenght of 1.928(3) A. Solution 1H NMR spectra of 1a show the presence of both cis- and trans-isomers, and a 500 MHz 1H NMR study at low temperature reveals two distinct exchange processes; the lower energy one results in the coalescence of the signals for the inequivalent methyl groups on the bridging isocyanide ligands of the cis-isomer, whereas the higher energy process brings about coalescence of the methyl signals for the bridging and terminal isocyanide ligands of the trans-isomer. At elevated temperatures all the methyl signals coalesce.

Hydrogen transfer processes in the formation of cationic η5 -dienyl complexes of ruthenium(II): X-ray structure of [Ru(1-5-η-cyclooctadienyl)(PMe2Ph)3][PF6]

Abstract The cations [Ru(1—3:5—6-η-C 8 H 11 )(η 6 -1,3,5-cyclooctatriene)] + ( 2 ) and [RuH(COD)L 3 ] + ( 5 ) (COD = cycloocta-1,5-diene, L = PMe 2 Ph, AsMePh 2 ) are convenient precursors to a range of η 5 -dienyl complexes of ruthenium(II); evidence for hydrogen transfer processes is presented.

Formation of the η5-bicyclo[5.1.0]octadienyl ligand by reaction of cyclooctatetraene with a ruthenium(II) hydride complex: Molecular structure of [Ru(2–6-η-bicyclo[5.1.0]octadienyl)(PMe2Ph)3][PF6]

Abstract [Ru(2–6-η-bicyclo[5.1.0]octadienyl)(PMe 2 Ph) 3 ][PF 6 ], formed from the reaction of cyclooctatetraene with [RuH(COD)(PMe 2 Ph) 3 ][PF 6 ] (COD = cycloocta-1,5-diene), has been characterised spectroscopically from 1 J (CH) coupling constants and an X-ray structural analysis; the bicyclic ligand contains an elongated bridging CC bond (1.63 A).