Barbara A. Kelly

Fluxional dirhodium complexes: crystal and molecular structure of [Rh2(CO)2(µ-SPh)2(C8H8)]

Variable temperature n.m.r. studies of complexes [Rh2(CO)2(µ-SPh)2L] and [Rh2(µ-SR)2L2](R = Me, Et, Pri, But, or Ph; L = cyclo-octatetraene or cyclo-octa-1,5-diene) reveal the existence of both an olefin rotation and an inversion of non-planar Rh2S2 ring; this non-planarity is established by an X-ray diffraction study of [Rh2(CO)2(µ-SPh)2(C8H8)].

Reactions of manganese atoms with cyclic dienes and cycloheptatriene: crystal structure of carbonylbis(1–4-η-cyclohexa-1,3-diene)manganese

Condensation of manganese atoms with cyclopentadiene, cyclohexa-1,3-diene, cycloheptatriene, and cyclo-octa-1,3-diene at –196 °C, followed by warming to 20 °C in the presence of CO, has given organomanganese carbonyl complexes in yields of 5–10% based on Mn. The new compounds [Mn(η4-C6H8)2(CO)], [Mn(η4-C7H8)2(CO)], and [Mn(η3-C8H13)(CO)4] have been isolated. A single-crystal X-ray diffraction study of [Mn(η4-C6H8)2(CO)] shows that the manganese atom adopts a square-pyramidal configuration with the carbonyl ligand in the axial position. The two hexadiene rings are each folded equatorially away from the Mn atom and the molecule has C2v symmetry. As in other diene complexes, the two inner C atoms are slightly closer to the metal [Mn–C (mean) 2.078(8)A] than are the outer C atoms [Mn–C (mean) 2.159(7)A]. The crystals are orthorhombic, space group P212121(no. 19) with Z= 4 in a unit cell with a= 8.570(1), b= 17.220(1), and c= 7.562(1)A. The structure has been refined to R 0.045.

Isomerisation of [{Rh(µ-SR1)(η-C5H4R2)}2]: 1H nuclear magnetic resonance and electrochemical studies and the X-ray crystal structure of [anti-{Rh(µ-SPh)(η-C5H5)}2]

The isomerisation of [syn-{Rh(µ-SR1)(η-C5H4R2)}2] to the anti-isomer, the structure of which (R1= Ph, R2= H) has been elucidated by X-ray crystallography, involves opening of the Rh2S2 ring; insertion into the metal–metal bond to give [Rh2(µ-SR1)2(µ-X)(η-C5H4R2)2]+(X = SR1 or Cl) is initiated by one-electron oxidation.

Reduction–oxidation properties of organotransition-metal complexes. Part 9. Silver(I) adducts of cyclic polyeneone complexes, the X-ray crystal structure of [{Fe(CO)3[η5-C5Ph4OAg(OH2)]}2][PF6]2, and comments on the use of the silver(I) ion as a one-electron oxidant

The tetraphenylcyclopentadienone complexes [M(CO)2L(η4-C5Ph4O)][1; M = Fe, L = CO, PPh3, or P(OMe)3; M = Ru, L = CO] and [Rh(η5-C5H5)(η4-C5Ph4O)](2) react with Ag[PF6] to give dimeric oxygen-bonded silver adducts [{M(CO)2L(η5-C5Ph4OAg)}2][PF6]2(3) and [{Rh(η5-C5H5)(η5-C5Ph4OAg)}2][PF6]2(4). The X-ray crystal structure of (3; M = Fe, L = CO) confirms that the cation contains a central planar asymmetric Ag2O2 bridge (Ag–O, 2.27 and 2.65 A) but there is a molecule of water co-ordinated to each Ag atom. The five-membered ring of the Fe(CO)3(C5Ph4O) moiety is best regarded as a substituted cyclopentadienyl although the carbon atom bearing the oxygen is significantly further from the iron atom (Fe–C, 2.31 A) than are the other four carbon atoms [Fe–C, 2.11 (mean)A]. There are also weak interactions between the silver atom and the two phenyl rings adjacent to the CO group in the C5 ring. The crystals were of poor quality, due to partial inclusion of molecules of CH2Cl2 the positions of which were not refined. This is reflected in the-relatively poor R value and high standard deviations. The crystals are monoclinic, a= 13.293(7), b= 14.128(6). c= 19.805(14)A, β= 105.75(5)°, space group P21/n. The Structure was solved by heavy-atom methods and refined to R 0.11 5 for 2 847 reflections. The iron complexes (3) react with halide ions to regenerate (1). but form [FeX(CO)2L(η4-C5Ph4O)][PF6][5; X = Br or I, L = CO, PPh3, or P(OMe)3] with halogens. Reaction of Ag[BF4] with [Cr(CO)3(η6-tropone)] gives [Cr(CO)3{η7-C7H6(OH)}][BF4]via the decomposition of an adduct related to (3) and (4). A summary is given of the behaviour of AgI as a reagent in organometallic chemistry, and a brief comment made on its use as a one-electron oxidant.

Crystal structure of dipotassium pentasulphide

Crystals of K2S5 are orthorhombic, space group P212121 with Z= 4 in a unit cell of dimensions: a= 6.494(1), b= 6.600(2), c= 17.414(5)A. The structure has been elucidated by vector methods from 656 independent diffracted intensities measured on a four-circle diffractometer and refined to R 0.045. The [S5]2– anion exists as a contorted but unbranched chain in which successive S–S bond lengths are 2.037, 2.074, 2.075, and 2.050(5)A, and the bond angles are close to tetrahedral. The torsions in the chain around the S(2)–(3) and S(3)–S(4) bonds are 74 and 69° respectively. The potassium ions are evenly distributed between the S5 units with minimum K ⋯ S 3.215(4)A, and a nearest-neighbour K ⋯ K of just under 4 A.

Reaction of halide ion with [Cr(CO)2(η-C6Me6)(NO)][PF6]: stabilisation of the product by phosphine substitution and X-ray crystal structure of trans, trans-[Cr(I)(CO)2(PPh2Me)2(NO)]

Addition of halide ion, X-, to [Cr(CO)2(η-C6Me6)(NO)][PF6] afords red solutions from which, on addition of phosphorus donor ligands, L, may be isolated [Cr(X)(CO)2(L)2(NO)]. The identities of two carbonylnitrosyl species present in the intermediate red solutions are discussed with reference to the crystal structure of trans,trans-[Cr(I)(CO)2(PPh2Me)(NO)]; crystals are monoclinic, space group P21, with Z= 2 in a unit cell of dimensions a= 9.796(4), b= 18.019(8), c= 8.968(1)A, β= 116.96(3)°. The structure was solved from diffractometer data by the heavy-atom method, and refined to R 0.005 for 2.233 observed reflections.

Molecular and crystal structure of tris(acetonitrile)nitrosylbis(triphenylphosphine)rhodium(III) dication as its hexafluorophosphate salt

Crystals of [Rh(NCMe)3(NO)(PPh3)2][PF6]2 are monoclinic, space group P21/n, with a= 14.053(8), b= 27.512(15), c= 11.914(8)A, β= 97.29(5)°, and Z= 4. The structure has been elucidated by the analysis of 8 502 observed intensities recorded at ca. 215 K on a four-circle diffractometer, and refined by least squares to R 0.075. In the cation the metal is octahedrally bound to trans-phosphorus atoms (mean Rh–P 2.405 A) and three acetonitrile ligands [Rh–N 2.030(7). 2.104(7), and 2.308(8)A] the last lying trans to the nitrosyl function [Rh–NO 2.026(8)A] which acts as the one-electron donor [NO]–[Rh–N–O 118.4(6)°]. The two hexafluorophosphate counter ions exhibit differing thermal activity which is correlated to their crystal environments.