Os Br Research Articles

Molecular Structure, Spectroscopic, Frontier Molecular Orbital Analysis, Molecular Docking Studies, and In Vitro DNA-Binding Studies of Osmium(II)-Cymene Complexes with Aryl Phosphine and Aryl Phosphonium Assemblies.

X-ray crystallography, spectroscopy, computational methods, molecular docking studies, and in vitro DNA-binding studies have been useful in the investigations of intermolecular and intramolecular interactions of osmium-cymene oxalato complexes with aryl phosphine and aryl phosphonium groups in both primary and secondary coordination spheres, respectively. Molecular structures of the novel complexes PPh4[Os(η6-p-cymene)Br(κ2-O,O'-C2O4)] (1) and [Os(η6-p-cymene) (κ2-O,O'-C2O4)PPh3] (2) were resolved by single-crystal X-ray diffraction (XRD). Primary and secondary coordination sphere contacts were investigated using Hirshfeld surface analysis which was supported by molecular docking (MD) studies. The MD data obtained predicted significant differences in binding energy across three receptors for the two osmium complexes. An in vitro DNA-binding study was accomplished using UV-Vis spectroscopy which showed that both 1 and 2 bond with DNA through an intercalation approach. The optimized molecular geometry, frontier molecular orbital (EHOMO and ELUMO) energies, global electrophilicity index (ω), chemical hardness (η), chemical potential (µ), and the energy band gap (EHOMO-ELUMO) were calculated utilizing density functional theory (DFT) methods. Computed structural parameters (bond lengths and angles) support the experimental single-crystal XRD data.

Synthesis and structure of osmium complexes: [Ph3PR] 2 + [OsBr6]2– (R = cyclo-C3H5, n-C4H9, cyclo-C6H11, CH2C(O)Ph), [Ph3PPr] 2 + [OsBr6]2– ∙ DMSO, and [Ph3P(CH2)3PPh3]2+[OsBr6]2– ∙ DMSO

The complexes [Ph3PR]2[OsBr6], R = cyclo-C3H5 (I), n-C4H9 (II), cyclo-C6H11 (III), CH2C(O)Ph (IV), [Ph3PPr]2[OsBr6] ∙ DMSO (V), and [Ph3P(CH2)3PPh3][OsBr6] ∙ DMSO (VI) (CIF files CCDC nos. 1000171, 1000148, 1000172, 1000173, 1000147, and 1000149 for structures I–VI, respectively) were prepared by reactions of sodium hexabromoosmate with phosphonium bromides in dimethyl sulfoxide. According to X-ray diffraction data, phosphorus atoms in the cations have slightly distorted tetrahedral coordination (CPC angles, 105.2(3)°–115.5(3)°; P–C, 1.773(6)–1.814(6) A). In the octahedral [OsBr6]2– anions, the Os–Br bond lengths are 2.4734(8)–2.5203(5) A and the cis-BrOsBr and trans-BrOsBr angles are 88.38(2)°–91.53(3)° and 177.276(18)°–180°, respectively. The structural organization in the crystals is formed by H∙∙∙Br (2.74–3.04 A) and H∙∙∙ODMSO (2.28–2.63 A) ion–ion hydrogen bonds.

Osmium complexes [Ph4Sb · DMSO]2[OsBr6] and [p-Tol4Sb · DMSO][p-Tol4Sb][OsBr6]: Synthesis and structure

The ionic complexes [Ph4Sb · DMSO]2[OsBr6] (I) and [p-Tol4Sb · DMSO][p-Tol4Sb][OsBr6] (II) have been synthesized by the reaction between sodium hexabromoosmate and tetraphenyl- or tetra-para-tolylstibonium bromide in dimethyl sulfoxide (DMSO). According to X-ray diffraction data, the antimony atoms in [Ph4Sb · DMSO]+ and [p-Tol4Sb · DMSO]+ cations have a distorted trigonal bipyramidal coordination, and the pseudo-axial CSbO and pseudo-equatorial СSbС angles are 173.7(2)°, 172.8(3)° and 111.3(2)°‒121.8(2)°, 107.4(3)°‒120.3(3)°, respectively. In the tetrahedral [p-Tol4Sb]+ cation, the СSbС angles are 106.1(4)°‒111.3(4)°. In the octahedral [OsBr6]2‒ anions, the Os‒Br bond lengths are 2.4765(6)‒2.4981(6) A (I) and 2.4795(11)‒2.5063(11) A (II); the trans-BrOsBr angles are 180.00(2)° (I) and 178.83(4)°‒179.34(4)° (II).

Powdery Mildew of Crenate Deutzia Caused by Erysiphe deutziae in Korea

Crenate deutzia ( Deutzia crenata Sieb. & Zucc.) is a commonornamental shrub belonging to the Hydrangeaceae. In July 2007,powdery mildew infections were first noticed in a garden ofildew m wdery o P won, Korea. u S , er nt e C iversity d National Agrobiolesions on leaves and non-lignified stems were conspicuous,especially when growing in the shade (Fig. 1A). The leavesexhibited chlorotic circular patches, sometimes forming reddishdiscolorations (Fig. 1B). Production of chasmothecia was foundstarting from September and continued into November. Voucher9). 24694, F2477 KUS-F ( y t i s a Univer e at Kor are kept s n e ecim p sulation. abundant spor oped with devel s e l coloni a ici f uper s ite h WHyphal appressoria were lobed, single or opposite in pairs.Conidiophores were 55-98 × 7.5-10 µ m, composed of 3-4 cells,straight or slightly flexuous at the base, and producing conidiasingly. Conidia were ellipsoid to barrel-shaped, 25-34 × 12.5-16.5µ r a hil i r e ducing p pro and , s e bodi n i os br i conspicuous f of devoid , mgerm tubes. First formed conidia were rounded at the apex andsubtruncate at the base. Chasmothecia were 90-135 µ m in diam.,blackish brown, depressed globose. Appendages were about 8-14in number, substraight to mildly bent, 4-5 times dichotomouslybranched, apex recurved, 1-3-septate. Asci were 3-6 per chasmo-×36-45 42-52 , m u i c e th µ 18- oval, ores were p Ascos spored. 6-8- , m22×12.5-15 µ m (Fig. 1C-J). The observations were in full f o s d recor ous previ h ent wit eem agr ae i z t u e ysiphe d r E U. (Bunkina). 2005) , al. et Bolay 1997; a, ur (Nom . kam a T S. & Braun of n regio S T te I e l p the com ungus, e f h t f o ity e ident h t m confir o T3 S5 and P ers IT im d with pr e plifi m 24694 was a KUS-F om DNA fr re h T sequenced. y directl and 2009) ( al. et u ts a kam a T bed by i scr e as dresulting sequence of 560 bp was deposited in GenBankGA4 E using M d e m or f per s wa is s ogenetic analy l . Phy GU196146) (with neighbor-joining method (using Tajima-Nei model). TheKorean isolate showed 100% similarity with two sequences of E.deutaezi found on D. crenata and D. scabra Thunb. from the UK the sequence , e or f e Ther . ) respectively DQ861917 and DQ861918, (be to e pathogen h ed t i f i r e is v s analy E . deutziae .Erysiphe deutziae is the only powdery mildew fungus knownomfr Deutzia n Far a i Russ om r ed f d recor fungus has been s Thi spp. new ope with Eur om fr recently 1997) and a, ur (Nom n a p and Ja t s a E, Switzerde land and ad in Frhneance, Germa spr Polmepidt e ic , anyUK (Bolay et al., 2005; Denton and Henricot, 2007) on several species of Deutzia of record s no previou been ere has h T . ae i deutz . E of troduced species and in ve ea, where several nati Kor om r f Deaziutt hos s as it fungus as well this of ecord rst r e fi h is is t h T owing. e gr ar. a e Kor t in n a pl

Synthesis, Characterisation and Properties of Diazoketiminato-Chelate Complexes of Os(II)

Reactions of 2-(arylazo)aniline, L-NH2 [L-NH2 = p-RC6H4N=NC6H4NH2; where R=H for L1-NH2, CH3 for L2-NH2 and Cl for L3-NH2] with [Os(H)Br(CO)(PPh3)3] gave the complexes [OsBr(L-NH)(CO)(PPh3)2] for which cyclic volatammograms exhibited one quasi-reversible oxidative response within the range 0.54–0.6 V vs SCE. The X-ray crystal structure of [OsBr(L1-NH)(CO)(PPh3)2] has been determined and its electronic structure was evaluated on the basis of single point DFT calculations using its crystallographic coordinates.

Synthesis, characterization, reactivity and molecular structure of arene-osmium complexes: A new synthetic entry into (η 6-arene)osmium(II) chemistry

A new convenient one-pot procedure for the preparation of the p-cymene-osmium dimer [(η 6- p-MeC 6H 4Pr i )OsBr 2] 2 ( 1) from potassium osmate K 2[OsO 2(OH) 4] is described. The analogous hexamethylbenzene complex [(η 6-C 6Me 6)OsBr 2] 2 ( 2) and a series of new arene-osmium complexes [(η 6- p-MeC 6H 4Pr i )OsLBr 2] ( 3– 9) (L = CO, PPh 3, PEt 3, PMePh 2, P(OMe) 3, P(OBu n ) 3 and P(OPh) 3) have been prepared from 1. The complex [(η 6-C 6Me 6)Os(CO)Br 2] ( 10) was obtained from 2. All the complexes were characterized spectroscopically by NMR and IR and by elemental analysis. Single crystal X-ray structures of [(η 6- p-MeC 6H 4Pr i )OsBr 2] 2 ( 1) and [(η 6- p-MeC 6H 4Pr i )Os(PPh 3)Br 2] ( 3) are reported. The reactions of some of these complexes with BrMg(CH 2) 3CH CH 2 and MeLi are also described.

Synthesis and Reactivity of the Osmium(III) Pentamethylcyclopentadienyl Complex (C5Me5)2Os2Br4. X-ray Crystal Structures of (C5Me5)2Os2Br4, (C5Me5)2Os2(μ-O)Br4, and (C5Me5)2Os2(μ-NPh)2Br2

Treatment of H2OsBr6 with C5Me5H in tert-butyl alcohol affords the dinuclear osmium(III) species (C5Me5)2Os2Br4, a mono(pentamethylcyclopentadienyl) complex that serves as the key synthetic entry into a wide array of “half-sandwich” complexes of osmium. The X-ray crystal structure shows it to contain two bridging and two terminal bromide ligands, with the Os−Br bond distances being shorter for the bridging bromide ligands than for the terminal bromide ligands. The Os−Os distance of 2.970(1) Å is indicative of a single osmium−osmium bond. The compound is weakly paramagnetic in solution and in the solid state, and the magnetic susceptibility determined over the range 4−300 K gives a singlet−triplet splitting of >800 cm-1. The reactions of (C5Me5)2Os2Br4 with oxygen, bromine, lithium anilide, acetonitrile, and norbornadiene (NBD) are described, affording the compounds (C5Me5)2Os2(μ-O)Br4, (C5Me5)OsBr4, (C5Me5)2Os2(μ-NPh)2Br2, [(C5Me5)Os(MeCN)3][BPh4], and (C5Me5)Os(NBD)Br; the crystal structures of the bridging oxo and bridging imido complexes are given.

Synthesis, characterization, and X-ray crystal structure of the octabromodiosmate(III) salt [(C 5Me 4H) 2OsBr] 2[Os 2Br 8] and its conversion to [(C 5Me 4H) 2OsBr][Os 2HBr 4(cod) 2

Treatment of hexabromoosmic acid, H 2OsBr 6, with 4 equiv. of tetramethylcyclopentadiene (C 5Me 4H 2) in tert-butanol at reflux for 8 h affords the unusual salt [(C 5Me 4H) 2OsBr] 2[Os 2Br 8], 1, which is the bis(tetramethylcyclopentadienyl)bromoosmocinium(IV) salt of the octabromodiosmate(III) dianion. The brown color of the salt suggests that the anion adopts an eclipsed conformation ( D 4 h symmetry) and this conclusion has been confirmed by a single-crystal X-ray diffraction experiment. The X-ray crystal structure indicates that the osmium atoms in the [ Os 2 Br 8 2 - ] anion are disordered over two sites. The bromine atoms show no evidence of disorder and are disposed in a quasi-cubic arrangement; the two Os–Os vectors are almost exactly orthogonal to each other and each vector points toward a different pair of opposite square faces of the Br 8 cube. The Os–Os bond distances are 2.219(5) and 2.229(1) Å; the average Os–Br distance in the anion is 2.417(2) Å. Treatment of [(C 5Me 4H) 2OsBr] 2[Os 2Br 8] with excess 1,5-cyclooctadiene in ethanol at gentle reflux for 3 h affords [(C 5Me 4H) 2OsBr][Os 2HBr 4(cod) 2], 2. An X-ray crystallographic study was carried out on a sample in which the cation was a mixture of [(C 5Me 4H) 2OsBr +] and [(C 5Me 4H) 2OsH +]. The results demonstrate that the anion adopts a confacial bioctahedral structure in which the hydride ligand and two bromides bridge between the two osmium centers. The C C bonds of the cod ligands are trans to the bridging bromide groups. The Os–Os bond distance in the anion is 2.874(1) Å. The average Os–Br distance is 2.596(2) Å for the bridging bromides and 2.565(2) Å for the terminal bromides. Compound 2 is the first example of an anionic diosmium complex containing a bridging hydride. The reaction of 1 with cod also results in the formation of bis(tetramethylcyclopentadienyl)osmocene, (C 5Me 4H) 2Os, 3, which has been isolated and characterized. Treatment of (C 5Me 4H) 2Os with 1.0 equiv. of HBF 4 · Et 2O affords the osmocinium salt [(C 5Me 4H) 2OsH][BF 4].

Novel indenyl half-sandwich osmium(II) complexes. X-ray structure of [Os{CC(H)Bu t}(η 5-C 9H 7)(PPh 3) 2][PF 6]·OEt 2

Reaction of LiC 9H 7 with [OsBr 2(PPh 3) 3] gives the complex [Os(η 5-C 9H 7)Br(PPh 3) 2] ( 1). The analogous complex [Os(η 5-C 9H 7)I(PPh 3) 2] ( 2) is obtained from the metathesis reaction of [Os(η 5-C 9H 7)Cl(PPh 3) 2] with NaI. The treatment of [Os(η 5-C 9H 7)X(PPh 3) 2] with NaOMe leads to the hydride derivative [Os(η 5-C 9H 7)H(PPh 3) 2] ( 3) which can be protonated with HBF 4 to yield the cationic complex [Os(η 5-C 9H 7)H 2(PPh 3) 2][BF 4] ( 4). Abstraction of the halide ligand in complexes [Os(η 5-C 9H 7)X(PPh 3) 2] with NaPF 6 or AgBF 4 followed by the treatment with NCMe or terminal alkynes yield complexes [Os(η 5-C 9H 7)(NCMe)(PPh 3) 2][BF 4] ( 6) and [Os{ COCH 2(CH 2) 3C H 2}(η 5-C 9H 7)(PPh 3) 2][PF 6] ( 7), respectively. X-ray crystal structure of the vinylidene derivative [Os{CC(H) tBu}(η 5-C 9H 7)(PPh 3) 2][PF 6] is reported along with variable temperature NMR studies.

Dipyridiniomethanecis-Dibromotetrafluoroosmate(IV),cis-[(C5H5N)2CH2][OsBr2F4

The title compound is an AB-type salt with a completely ordered anion sublattice. Because of the strong trans influence of the Br ligands, both Os—Br bonds, of 2.466 (1) and 2.468 (1) Å, are shortened compared to those reported for K2[OsBr6] (2.51 Å). However, only one of the two F ligands coordinated trans to a Br ligand exhibits a longer Os—F distance [1.968 (4) Å] than those along the symmetrically coordinated F—Os—F axis [1.930 (4) and 1.929 (4) Å].

Synthesis and Characterization of Osmium(II) Compounds of Stoichiometry (C5Me5)OsL2Br, (C5Me5)OsL2H, and (C5Me5)Os(NO)Br2

The preparations of several new (pentamethylcyclopentadienyl)osmium(II) complexes from the osmium(III) compound (C5Me5)2Os2Br4 are described; among these are phosphine and alkene complexes of stoichiometry (C5Me5)OsL2Br and (C5Me5)OsL2H as well as the nitrosyl complex (C5Me5)Os(NO)Br2. Treatment of (C5Me5)2Os2Br4 with PPh3 in ethanol or PMe3 in dichloromethane affords the osmium(II) complexes (C5Me5)OsL2Br, where L = PPh3 or PMe3; the 1,5-cyclooctadiene complex (C5Me5)Os(cod)Br can be made similarly in ethanol. Treatment of either the PPh3 or cod complex with other tertiary phosphines in refluxing heptane affords several other compounds of this class: (C5Me5)OsL2Br, where L = PEt3, 1/2 Me2PCH2PMe2, 1/2 Me2PCH2CH2PMe2, or 1/2 Ph2PCH2PPh2. These bromoosmium(II) species serve as excellent starting materials for the preparation of other osmium(II) complexes. For example, treatment with NaBH4 in ethanol or with NaOMe in methanol affords the hydrides (C5Me5)OsL2H, where L = PMe3, PEt3, PPh3, 1/2 cod, 1/2 Me2PCH2PMe2, 1/2 Me2PCH2CH2PMe2, or 1/2 Ph2PCH2PPh2. Interestingly, treatment of (C5Me5)Os(PMe3)2Br with NaBH4 in refluxing ethanol affords the dihydride cation [(C5Me5)Os(PMe3)2H2+], which can be deprotonated with methyllithium in tetrahydrofuran to afford the electrically neutral hydride (C5Me5)Os(PMe3)2H. This hydride complex is expected to be one of the most basic transition metal complexes known. Finally, treatment of (C5Me5)2Os2Br4 with nitric oxide in dichloromethane yields the osmium(II) complex (C5Me5)Os(NO)Br2. IR, NMR, and mass spectra of the new complexes are described. A secondary 13C/12C isotope effect on the 31P NMR chemical shifts of ca. 0.025 ppm is noted in several compounds. Comparisons of these osmium(II) compounds with analogous ruthenium species suggests that the former have stronger metal−ligand bonds, are slower to undergo nucleophilic substitution reactions, and are stronger reducing agents.

The first Cp ∗ Os half-sandwich complexes containing chalcogenido ligands

The reactions of the pentamethylcyclopentadienyl-osmium compound Cp ∗Os(NO)Br 2 ( 1) with Na 2S 4 and (NEt 4) 2Se 6 in dimethyl- formamide solution lead to mononuclear tetrachalcogenido complexes Cp ∗ Os(NO) (E 4) (E = S ( 2a), Se ( 2b)), whereas binuclear products Cp 2 ∗Os 2(NO) 2(μ-E) 2 (E = S ( 3a), Se ( 3b), Te ( 3c)) are obtained from the reactions of 1 with Li 2 E in tetrahydrofuran solution. Dechalcogenation of 2a,b using tri(n-butyl)phosphane gives 3a,b. The molecular geometry of Cp ∗ Os(NO)(Se 4) ( 2b) has been determined by an X-ray crystal structure analysis which confirms the presence of a non-planar cyclotetraselenido chelate ligand.

Tetraphenylphosphonium trans-Aquatetrabromo(carbonyl)osmate(III), trans-[(C6H5)4P][OsBr4(CO)(H2O)

The X-ray structure determination of tetraphenylphosphonium trans-aquatetrabromo(carbonyl)osmate(III), trans-[(C6H5)4P][OsBr4(CO)(H2O)], at 293 K has revealed a slightly distorted octahedral coordination of the osmium(III) atom, with H2O trans to the almost linear carbonyl group. The distances are 1.795 (10) for Os—C, 2.181 (6) for Os—Ow, and 1.164 (9) Å for C—O; among the Os—Br bond lengths two are shorter, 2.4692 (8) and 2.4753 (10), and two are longer, 2.5042 (8) and 2.5072 (8) Å. Centrosymmetric dimers of the complex anions are formed by intermolecular hydrogen bonding between the coordinated water molecule and the two Br ligands that form longer bonds to the central atom.

Schwingungsspektren und Normalkoordinatenanalyse der Bromo-Iodo-Osmate(IV), [OsBrnI6-n]2-, n = 0-6 / Vibrational Spectra and Normal Coordinate Analysis of Bromo-Iodo-Osmates(IV), [OsBrnI6-n]2-, n = 0-6

The IR and Raman spectra of the ten bromo-iodo-osmates(IV) [OsBrnI6-n]2-, n = 0-6, including the geometrical isomers for n = 2, 3, 4, have been recorded at low temperature. The vibrational spectra are completely assigned according to point groups Oh, D4h, C4v, C3v, and C2v, as supported by normal coordinate analyses based on a general valence force field. Due to the different trans-influences Br<I in asymmetric axes Br′–Os–I′, the Os–I′ bonds are strengthened and the Os–Br′ bonds are weakened, as indicated by valence force constants, for Os–I′ on average 4% higher and for Os–Br′ 4% lower, as compared with the values calculated for symmetric I–Os–I and Br–Os–Br axes, respectively.

The structural chemistry of some osmium nitrosyl complexes

The two complexes tribromo(nitrosyl)(diethylsulfide)(diethylsulfoxide)osmium(II), Os(NO)Br 3(Et 2S)- (Et 2SO) and dichloro(nitrosyl)bis(diethylphenylphosphine)(2-methoxyethanoate)osmium(II), Os(NO)- Cl 2(Et 2PPh) 2(CH 3OCH 2CH 2O), have been isolated during studies of photochemical reactions of platinum metal nitrosyl compounds. The molecular structures of these compounds have been determined by single crystal X-ray diffraction. The bright red crystals of Os(NO)Br 3(Et 2S)(Et 2SO) are monoclinic P2 1/ c; a=13.398(3), b=8.501(2), c=16.199(3) Å, β=105.69(5)°, V=1776.41(55) Å 3, Z=4. The structure was refined to a R factor of 0.0617 and a R w, of 0.0599. The complex is isostructural with the ruthenium analogue whose structure has been reported previously. The nitric oxide is coordinated in the linear manner (OsNO=174.3(29)°) and the diethylsulfoxide ligand is oxygen bound (OsO=2.074(17) Å) trans to the NO as suggested from its infrared spectrum ( v(SO)=940 cm −1). The pale orange crystals of Os(NO)Cl 2(Et 2PPh) 2(CH 3OCH 2CH 2O) are also monoclinic P2 1/ c; a=10.869(1), b=11.381(1), c=22.673(2) Å, β=102.17(10)°, V=2741.5(10) Å 3, z=4. The structure was refined to an R of 0.0482 and a R w of 0.0464. The diethylphenylphosphine ligands are coordinated in the trans-arrangement, and the OsP bond lengths are identical; 2.427(3), 2.428(3) Å. The nitric oxide is coordinated in the linear manner (OsNO=1.837(10) Å) and the 2-methoxyethanoate is coordinated trans to the nitrosyl (OsO=1.949(7) Å).

Schwingungsspektren und Normalkoordinatenanalyse der Chloro-Bromo-Osmate(IV), [OsCl„Br6-n]2-, n = 0-6 / Vibrational Spectra and Normal Coordinate Analysis of Chloro-Bromo-Osmates(IV), [OsCl„Br6-n]2-, n = 0-6

The IR- and Raman spectra of the ten chloro-bromo-osmates(IV) [OsCl„Br6-n]2-, n = 0-6, including the geometrical isomers for n = 2, 3, 4 have been recorded at low temperature (80 K). The vibrational spectra of these complexes are completely assigned according to point groups Oh, D4h, C4v, C3v and C2v, supported by normal coordinate analyses based on a general valence force field. Due to the stronger trans-influence of Br as compared to Cl, in all asymmetric Cl—Os—Br axes the Os—Br bonds are strengthened and the Os—Cl bonds are weakened, indicated by valence force constants for Os— Br approximately 6% higher, for Os—Cl 6% lower, as compared with the values calculated for symmetrical Br—Os—Br and Cl-Os-Cl axes, respectively. The significantly stronger interaction between opposite bonds is revealed by the stretching interaction constants fdd, which are about three times larger than fdd for bonds at right angles.

Cyclopentadienyl-ruthenium and -osmium chemistry: XXIV. Some complexes containing the olefinic tertiary phosphine 2-CH 2CHC 6H 4PPh 2 (sp): X-ray structures of one isomer of OsBr(sp)(η-C 5H 5), and of [formula omitted]Ph 2-2)(η-C 5H 5), containing an η 3-dithiocarboxylato group

Reactions between MX(PPh 3) 2(η-C 5H 5) (M = Ru, X = Cl; M = Os, X = Br) and 2-CH 2CHC 6H 4PPh 2 afford MX(η 2-CH 2CHC 6H 4P Ph 2)(η-C 5H 5); the Os complex is obtained in two isomeric forms. The X-ray structure of the major isomer shows the CC double bond (OsC, 2.214, 2.195 Å; CC, 1.57 Å) is almost coplanar with the OsBr vector, with the terminal C cis to Br; the minor isomer is assumed to have the alternative, more sterically congested conformation, with the β-C cis to Br. The chlororuthenium complex reacts with NaOMe/MeOH to give the corresponding hydrido complex, which also exists as two isomers in solution; reaction of this complex with CS 2 gives the expected dithio acid derivative Ru(S 2CCHMeC 6H 4P Ph 2)(η-C 5H 5), together with small amounts of a complex assumed to be Ru[S 2C(CH 2) 2C 6H 4P Ph 2](η-C 5H 5). The X-ray structure of the major product reveals an unusual η 3-S 2C mode of coordination of the dithio acid fragment (RuS, 2.418, 2.426(1) Å; RuC 2.175(4) Å). Crystals of OsBr(η 2-CH 2CHC 6H 4P)Ph 2)( η-C 5H 5) are monoclinic, space group P2 1/ n, with a 12.696(2), b 21.719(6), c 15.929(3) Å, β 79.77(2)°, Z = 8; 2867 data ( I > 2.5σ( I)) were refined to R = 0.040, R w = 0.044. Crystals of Ru(η 3-S 2CCHMeC 6H 4P Ph 2)(η-C 5H 5) are orthorhombic, space group Pbca, with a 8.921(2), b 15.982(9), c 32.216(5) Å, Z = 8; 1685 data ( I > 2.5σ( I)) were refined to R = 0.027, R w = 0.030.

Polarised single-crystal electronic absorption spectra of tetraphenylarsonium tetrahalogenonitrido-osmate(VI) compounds and the crystal and molecular structures of tetraphenylarsonium tetrabromonitrido-osmate(VI)

The single-crystal polarised electronic absorption spectra of [AsPh4][OsNX4](X = Cl, Br, or I) at room temperature and 5 K are reported in the range 10 000–40 000 cm–1. The spectra have been interpreted using the observed polarisation and vibrational fine-structure data in conjunction with a parameterised ligand-field model. The single-crystal structure of [AsPh4][OsNBr4] has been determined by X-ray crystallography. The compound crystallises in the tetragonal space group P4/n, a=b= 12.774(3), c= 8.008(3)A, Z= 2. The [OsNBr4]– ion has 4mm(C4v) symmetry with Os–N 1.583(15), Os–Br 2.457(1)A, N–Os–Br 104.29(3)°. The [AsPh4]+ cation has crystallographic (S4) symmetry with As–C 1.891 (8)A, C–As–C 105.12(48) and 116.69(25)°.