Cisoid Arrangement Research Articles

N-O Bond Activation and Cleavage Reactions of the Nitrosyl-Bridged Complexes [M2Cp2(μ-PCy2)(μ-NO)(NO)2] (M = Mo, W).

The title complexes (1a,b) were prepared in two steps by first reacting the hydrides [M2Cp2(μ-H)(μ-PCy2)(CO)4] with [NO](BF4) in the presence of Na2CO3 to give dinitrosyls [M2Cp2(μ-PCy2)(CO)2(NO)2](BF4), which were then fully decarbonylated upon reaction with NaNO2 at 323 K. An isomer of the Mo2 complex having a cisoid arrangement of the terminal ligands ( cis-1a) was prepared upon irradiation of toluene solutions of 1a with visible-UV light at 288 K. The structure of these trinitrosyl complexes was investigated using X-ray diffraction and density functional theory (DFT) calculations, these revealing a genuine pyramidalization of the bridging NO that might be associated in part to an increase of charge at the N atom and anticipated a weakening of the N-O bond upon reaction with bases or reducing reagents. Complexes 1a,b reacted with [FeCp2](BF4) to give first the radicals [M2Cp2(μ-PCy2)(μ-NO)(NO)2](BF4) according to CV experiments, which then underwent H-abstraction to yield the nitroxyl-bridged complexes [M2Cp2(μ-PCy2)(μ-κ1:η2-HNO)(NO)2](BF4), alternatively prepared upon protonation with HBF4·OEt2. The novel coordination mode of the nitroxyl ligand in these products was thermodynamically favored over its tautomeric hydroximido form, according to DFT calculations, and similar nitrosomethane-bridged cations [M2Cp2(μ-PCy2)( μ-κ1:η2-MeNO)(NO)2]+ were prepared by reacting 1a,b with CF3SO3Me or [Me3O]BF4. Complexes 1 reacted with M(Hg) (M = Zn, Na) in tetrahydrofuran to give the amido-bridged derivatives [M2Cp2(μ-PCy2)(μ-NH2)(NO)2] with retention of stereochemistry, a transformation also induced by using mild O atom scavengers such as CO and phosphites in the presence of water. In the absence of water, phosphites accomplished a deoxygenation of the bridging NO of the Mo2 complexes to yield the phosphoraniminato-bridged derivatives [Mo2Cp2(μ-PCy2){μ-NP(OR)3}(NO)2] (R = Et, Ph), also with retention of stereochemistry.

Heterometallic clusters derived from the unsaturated carbyne-bridged dimolybdenum complexes [Mo2(η5-C5H5)2(μ-CPh) (μ-PCy2) (CO)x] (x = 1, 2)

The carbonyl-bridged complex [Mo2Cp2(μ-CPh) (μ-PCy2) (μ-CO)] (1) reacted with [Fe2(CO)9] at room temperature to give the 46-electron trinuclear cluster [FeMo2Cp2(μ3-CPh) (μ-PCy2) (CO)5] (Mo–Mo = 2.6782(4) Å), and a similar Mo2Ru cluster was obtained upon reaction with [Ru3(CO)12] under irradiation with visible-UV light (Cp = η5-C5H5). Compound 1 reacted with [Co2(CO)8] at room temperature to give the 60-electron tetrahedral cluster [Co2Mo2Cp2(μ3-CPh) (μ-PCy2) (CO)7], which in solution exits as an equilibrium mixture of two isomers and presumably displays phosphide and carbyne ligands in a cisoid arrangement. This compound evolved thermally to give a third isomer having these ligands arranged in a transoid way (P–Mo–C = 126.3(1)o, Mo–Mo = 2.9612(6) Å). The dicarbonyl complex [Mo2Cp2(μ-CPh) (μ-PCy2) (CO)2] (2) reacted with W(CO)6 under visible-UV light irradiation to give two thermally unstable isomers of the 46-electron trinuclear cluster [Mo2WCp2(μ3-CPh) (μ-PCy2) (CO)6]. Reaction of 2 with [AuCl(PR3)] (R = Me, p-tol, iPr) in the presence of TlPF6 gave first the corresponding cationic clusters trans-[AuMo2Cp2(μ3-CPh) (μ-PCy2) (CO)2(PR3)]PF6, which then evolved thermally to the more stable isomers cis-[AuMo2Cp2(μ3-CPh) (μ-PCy2) (CO)2(PR3)]PF6 (Mo–Mo = 2.810(1) Å for R = iPr), selectively formed with a syn conformation of the carbyne and Cp ligands, except for the PMe3 complex. In contrast, reaction of 2 with CuCl led to a cluster of composition [CuMo2ClCp2(μ3-CPh) (μ-PCy2) (CO)2], presumably present as a monomer in solution, but certainly appearing in the solid state as a centrosymmetric dimer held by bridging Cu–Cl–Cu interactions (Mo–Mo = 2.8004(5), Cu–Cl = 2.309(1), 2.409(1) Å).

Reactivity of the 16e (p-cymene)Ru half-sandwich complex containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand towards diynes

The reactions of the 16e half-sandwich complex (p-cymene)Ru(S(2)C(2)B(10)H(10)) (Ru16e) with 1,4-diethynylbenzene (L1), 3',6-diethynyl-1,1'-binaphthyl-2,7'-diyl diacetate (L2), 2-bromo-5-ethynylthiophene (L3) and 2,5-diethynylthiophene (L4) lead to 18e mononuclear complexes (p-cymene)Ru(S(2)C(2)B(10)H(9))(H(2)CCPhC≡CH) (1), (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(24)H(16)O(4))C≡CH] (2), (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)Br] (3) and (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)C≡CH] (4), respectively. In all of them, metal-induced B-H activation has occurred, which leads to a stable Ru-B bond, and the structures take a cisoid arrangement. Only in the case of L4, the binuclear complexes [(p-cymene)Ru(S(2)C(2)B(10)H(9))](2)[H(2)CC(C(4)H(2)S)CCH(2)] (5a and 5b) are observed, which are conformational isomers generated by the differing orientations of the p-cymene unit. 4 can be readily converted to the complex (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(4)H(2)S)COCH(3)] (6) in the presence of silica and H(2)O. All of these products 1-6 were characterized by NMR, IR, elemental analysis and mass spectrometry. The structures of 1, 3, and 5a were also determined by single-crystal X-ray diffraction analysis.

Carbodiimide insertion reactions of homoleptic heavier alkaline earth amides and phosphides

A series of homoleptic guanidinate-type complexes of the heavier alkaline earth (Ae) metals calcium and strontium have been prepared. The six-coordinate compounds [Ae{(i)PrNC(NPh(2))CN(i)Pr}(2)(THF)(2)] (Ae = Ca and Sr) were synthesised through reactions of the appropriate THF-solvated hexamethyldisilazide [Ae{N(SiMe(3))(2)}(2)(THF)(2)] with two molar equivalents of diphenylamine and 1,3-di-iso-propylcarbodiimide. Both compounds were shown to crystallise with a cisoid arrangement of the two THF molecules at the metal centres. In contrast, the (Me(3)Si)(2)N-substituted calcium guanidinate, [Ca{CyNC{N(SiMe(3))(2)}CNCy}(2)(THF)(2)], contains two coordinated THF molecules with a trans disposition. Further reactions of the free amidine [{(2-FC(6)H(4))N}C(NH(i)Pr)(2)] with either [Ca{N(SiMe(3))(2)}(2)(THF)(2)] or its dimeric unsolvated analogue provided monomeric or dimeric derivatives respectively in which the ligands had tautomerised to an anisobidentate form. A further reaction of the phosphaguanidine [CyN=C(PPh(2))N(H)Cy] with [Sr{N(SiMe(3))(2)}(2)(THF)(2)] provided the first example of a phosphaguanidinate complex of this heavier alkaline earth metal. This compound has also been characterised in the solid state and shown to exist with a transoid configuration of the coordinated THF molecules.

The Heteropolytungstate Core {BW13O46}11‐ Derived as Monomer, Dimer, and Trimer.

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Alkenyl Derivatives of the Unsaturated Dimolybdenum Hydride Complex [Mo2(η5-C5H5)2(μ-H)(μ-PCy2)(CO)2

The 30-electron hydride complex [Mo2Cp2(μ-H)(μ-PCy2)(CO)2] reacts at room temperature with p-tolylacetylene to give the unsaturated σ:π-bonded alkenyl derivatives trans-[Mo2Cp2(μ-η1:η2-CRCH2)(μ-PCy2)(CO)2] and trans-[Mo2Cp2(μ-η1:η2-CHCHR)(μ-PCy2)(CO)2] (R = ptol; Cp = η5-C5H5), with the α-substituted alkenyl complex being transformed completely into its β-substituted isomer slowly at room temperature. In solution, both compounds exhibit an isomeric equilibrium (rapid on the NMR time scale) involving the alternate π-binding of the alkenyl ligand to each of the metal centers. In addition, the presence of CO allows the partial conversion of the α-substituted complex into its cis-dicarbonyl isomer cis-[Mo2Cp2(μ-η1:η2-CRCH2)(μ-PCy2)(CO)2], so as to reach a roughly equimolar equilibrium ratio. In contrast, the β-substituted alkenyl complex experiences full carbonylation under the same conditions to give the tricarbonyl complex [Mo2Cp2{μ-η1:η2-CHCHR}(μ-PCy2)(CO)3], but similarly displaying a cisoid arrangement o...

The Heteropolytungstate Core {BW13O46}11− Derived as Monomer, Dimer, and Trimer

A study of the borotungstate system has led to the characterization of new, original compounds based on the unconventional Keggin derivative [H(3)BW(13)O(46)](8-) ion (denoted as 1). [H(3)BW(14)O(48)](6-) (2) and the dimer [H(6)B(2)W(26)O(90)](12-) (3) crystallize as mixed cesium/ammonium salts and have been characterized by single-crystal X-ray diffraction analysis. Anion 2 reveals an unusual arrangement, consisting of an outer {W(3)O(9)} core grafted onto the monovacant [BW(11)O(39)](9-) Keggin moiety and exhibits an unprecedented distorted square-pyramidal arrangement for a cis-{WO(2)} core. Elemental analysis, supported by bond distance analysis, is consistent with the presence of three protons distributed over the terminal oxygens of the outer {W(3)O(7)} capping fragment. The [H(6)B(2)W(26)O(90)](12-) ion (3) is formally derived from the direct condensation of two [H(3)BW(13)O(46)](8-) subunits. The cisoid arrangement of the two [BW(11)O(39)](9-) subunits, coupled with the antiparallel arrangement of the two quasi-linear O=W...O=W-OH2 chains within the central {W(4)O(12)} connecting group, breaks any symmetry, thereby resulting in a chiral compound. Polarography and pH-metric titrations reveal the formation of the monomeric precursor [H(3)BW(13)O(46)](8-) (anion 1) under stoichiometric conditions. (183)W NMR analysis of 2 and 3 in solution gives complex spectra, consistent with the presence of equilibria between several species. In the frame of this study, we also report on a structural re-investigation of the [H(6)B(3)W(39)O(132)](15-) ion (4) based on reliable results obtained in the solid state by means of single-crystal X-ray diffraction analysis, and in solution by means of 1D and 2D COSY (183)W NMR. X-ray diffraction analysis revealed the presence of three attached aquo ligands on the central {W(6)O(15)} connecting core, generating three O=W...O=W-OH2 quasi-linear chains, which are responsible for the chirality of the trimeric assembly. This structural arrangement accounts for the 39-line (183)W solution spectrum. The 2D COSY spectrum permits reliable assignments of the six strongly shielded resonances (around -250 and -400 ppm) to the six central W atoms, as well as additional assignments. The origin of such strong shielding for these particular W atoms is discussed on the basis of previously published results. Infrared data for compounds 1, 3, and 4 are also presented.

A Conformational Study of Phospha(III)- and Phospha(V)-guanidine Compounds

Spectroscopic, crystallographic, and computational studies of the substituent distribution about the "NCN" unit in a series of phospha(III)- and phospha(V)-guanidines, R(2)PC{NR'}{NHR'} and R(2)P(E)C{NR'}{NHR'} (R = Ph, Cy; R' = (i)Pr, Cy; E = S, Se), are reported. In the phosphorus(III) systems, the P-diphenyl substituted compounds are observed as only one isomer, shown by NMR spectroscopy to be the E(syn)-(alpha) configuration. In contrast, the corresponding P-dicyclohexyl derivatives exist as a mixture of E(syn)-(alpha) and Z(anti) in solution. Spectroscopic techniques are unable to determine whether the latter isomer exists as the alpha- or beta-conformer relative to rotation about the P-C(amidine)() bond; however, DFT calculations indicate a low-energy structure for the N,N'-dimethyl model complex in the beta-conformation. In their oxidized sulfo and seleno forms, the P-diphenyl compounds are present as an interconverting equilibrium mixture of the E(syn)-(beta) and Z(syn)-(beta) isomers in solution ( approximately 3:2 ratio), whereas for the P-dicyclohexyl analogues, the latter configuration (in which the nitrogen substituents are in a more sterically unfavorably cisoid arrangement about the imine double bond) is the dominant form. Intramolecular E...HN (E = S, Se) interactions are observed in solution for the Z(syn)-(beta) configuration of both P-substituted species, characterized by J(SeH) coupling in the NMR spectrum for the P(V)-seleno compounds and a bathochromic shift of the NH absorption in the infrared spectrum. An X-ray crystallographic analysis of representative Ph(2)P(E)- and Cy(2)P(E)-substituted species shows exclusively the E(syn)-(beta) configuration for the P-diphenyl substituted compounds and the Z(syn)-(beta) form for the P-dicyclohexyl derivatives, independent of the chalcogen and the nitrogen substituents. Results from a DFT analysis of model compounds fail to identify a compelling electronic argument for the observed preferences in substituent orientation, suggesting that steric factors play an important role in determining the subtle energetic differences at work in these systems.

Rare earth metal complexes based on β-diketiminato and novel linked bis(β-diketiminato) ligands: Synthesis, structural characterization and catalytic application in epoxide/CO 2-copolymerization

Mesityl substituted β-diketiminato lanthanum and yttrium complexes [(BDI)Ln{N(SiRMe 2)} 2] (BDI = ArNC(Me)CHC(Me)NAr, Ar = 2,4,6-Me 3C 6H 2, Ln = La, R = Me ( 1), H ( 2a); Ln = Y, R = H ( 2b)) can be prepared via facile amine elimination starting from [La{N(SiMe 3) 2} 3] and [Ln{N(SiHMe 2) 2} 3(THF) 2] (Ln = Y, La), respectively. The X-ray crystal structure analysis of 1 revealed a distorted tetrahedral geometry around lanthanum with a η 2-bound β-diketiminato ligand. A series of novel ethylene- and cyclohexyl-linked bis(β-diketiminato) ligands [C 2H 4(BDI Ar) 2]H 2 and [Cy(BDI Ar) 2]H 2 [Ar = Mes (=2,4,6-Me 3C 6H 2), DEP (=2,6-Et 2C 6H 3), DIPP (=2,6- i-Pr 2C 6H 3)] were synthesized in a two step condensation procedure. The corresponding bis(β-diketiminato) yttrium and lanthanum complexes were obtained via amine elimination. The X-ray crystal structure analysis of the ethylene-bridged bis(β-diketiminato) complex [{C 2H 4(BDI Mes) 2}YN(SiMe 3) 2] ( 3b) and cyclohexyl-bridged complexes [{Cy(BDI Mes) 2}LaN(SiHMe 2) 2] ( 7) and [{Cy(BDI DEP) 2}LaN(SiMe 3) 2] ( 8) revealed a distorted square pyramidal coordination geometry around the rare earth metal, in which the amido ligand occupies the apical position and the two linked β-diketiminato moieties form the basis. The geometry of the bis(β-diketiminato) ligands depends significantly on the linker unit. While complexes with an ethylene-linked ligand adopt a cisoid arrangement of the two aromatic substituents, complexes with cyclohexyl linker adopt a transoid arrangement. Either one ( 3b) or both ( 7, 8) of the β-diketiminato moieties are tilted out of the η 2 coordination mode, resulting in close Ln⋯C contacts. The β-diketiminato and linked bis(β-diketiminato) complexes were moderately active in the copolymerization of cyclohexene oxide with CO 2. A maximum of 92% carbonate linkages were obtained using the ethylene-bridged bis(β-diketiminato) complex [{C 2H 4(BDI Mes) 2}LaN(SiHMe 2) 2] ( 4).

Group 14 triple-decker cations

The triple-decker cations trans-[(Cp*Sn)(2)(mu-eta(5):eta(5)-Cp*)](+) and trans-[(Cp*Pb)(2)(mu-eta(5):eta(5)-Cp*)](+) have been prepared and structurally characterized as their [B(C(6)F(5))(4)](-) salts from the reactions of [Cp*M][B(C(6)F(5))(4)](M = Sn, Pb) with the appropriate decamethylmetallocene. Both triple-decker cations adopt a cisoid arrangement of terminal Cp* groups, whereas the two known triple-decker main-group anions possess a transoid arrangement of terminal Cp groups. The reason for this conformational difference has been probed on the basis of DFT calculations.

The structural and spectroscopic characterisation of three actinyl complexes with coordinated and uncoordinated perrhenate: [UO2(ReO4)2(TPPO)3], [[(UO2)(TPPO)3]2(mu2-O2)][ReO4]2 and [NpO2(TPPO)4][ReO4

The first structural characterization of an actinide complex with coordinated perrhenate is reported, [UO2(ReO4)2(TPPO)3] (1). In this [UO2]2+ complex two [ReO4]- anions and three TPPO (triphenylphosphine oxide) P=O donor ligands are coordinated in the equatorial plane in a cisoid arrangement. This bonding arrangement, and apparent strain observed in the equatorially bonded ligands, is attributed to the solid state packing in adjacent molecules in which hydrophobic TPPO ligands form an effective "shell" around a hydrophilic core of two UO2(ReO4)2 moieties. Solid state vibrational spectroscopy (infrared and Raman), 31P CP MAS NMR and elemental analysis are also consistent with the formula of 1. Solution state vibrational spectroscopy and 31P NMR measurements in EtOH indicate the lability of the TPPO and [ReO4]- groups. The photolytic generation of peroxide in EtOH solutions of 1 leads to the formation of trace quantities of [[(UO2)(TPPO)3]2(mu2-O2)][ReO4]2, 2, in which the coordinated [ReO4]- groups of 1 have been displaced by bridging O2(2-), derived from atmospheric O2. Finally, attempts to synthesise a [NpO2]+ analogue of have resulted only in the formation of [NpO2(TPPO)4][ReO4], 3, in which [ReO4]- acts solely as a counter anion. From these results it can be concluded that [ReO4]- will bond to [UO2]2+, but will be readily displaced by a more strongly coordinating ligand (e.g. peroxide) and will not coordinate to an actinyl cation with a lower charge, [NpO2]+, under the same reaction conditions.

Synthesis and characterization of dirhodium(II,II) formamidinate complexes containing short-bite nitrogen ligands

The Rh 2 4+ complex [Rh 2(form) 2(O 2CCF 3) 2(H 2O) 2] (form= N, N′-di- p-tolylformamidinate anion) easily reacts with the short-bite ligand pyrido[2,3- b]pyrazine, molar ratio 1:2, yielding the complex [Rh 2(form) 2(pyrido[2,3-b]pyrazine) 2(O 2CCF 3) 2] which has been characterized by conductivity measurements and IR and 1H NMR spectroscopy. The complex exhibits a “lantern” type structure with the two nitrogen ligands coordinated, in a cisoid arrangement, at the equatorial positions across the dirhodium unit while the axial sites are occupied by two monoligated trifluoroacetate groups. Conductivity and IR data show that in DMSO the complex undergoes dissociation of both the axial ligands leading to the species [Rh 2(form) 2(pyrido[2,3-b]pyrazine) 2(DMSO) 2] 2+. The parent compound reacts also with 2-chloro-5,7-dimethyl-1,8-naphtyridine and 2,7-dichloro-5-methyl-1,8-naphtyridine leading to [Rh 2(form) 2(O 2CCF 3)(C 10H 9N 2O)(H 2O)] and [Rh 2(form) 2(O 2CCF 3)(C 9H 6N 2ClO)(H 2O)], respectively, in which the dirhodium unit is supported by three different bridging ligands. Microanalysis, 1H NMR and X-ray data unambiguously show that the reaction proceeds, unexpectedly, with elimination of a trifluoroacetate group and the substitution of a chlorine atom of the naphtyridine ligands by oxygen.

Me2Si(η5-C5H4)2-Bridged Dinuclear Ruthenium Complexes: X-ray Crystal Structures of [Ru2{μ-(η5-C5H4)2SiMe2}(Cl)2(CO)4] and [Ru2{μ-(η5-C5H4)2SiMe2}(μ-Br)(CO)4][BF4

The treatment of the binuclear tetracarbonyl complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-CO)2(CO)2] (1) with HBF4 in dichloromethane leads to the electrophilic addition of one proton to yield the bridging hydride complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-H)(CO)4][BF4] (2). Complex 1 also reacts with Li[BHEt3] to afford the bridging methylene complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-CH2)(μ-CO)(CO)2] (3). Binuclear complexes [Ru2{μ-(η5-C5H4)2SiMe2}(X)2(CO)4] (X = Cl (4a), Br (4b), and I (4c)) have been synthesized in good yields from the reaction of complex 1 with N-chlorosuccinimide (X = Cl) and X2 (X = Br, I) in CH2Cl2. The structure of complex 4a which has been determined by X-ray crystallography shows a three-legged piano-stool geometry around each ruthenium atom linked by the bridging Me2Si(η5-C5H4)2 group. The cyclopentadienyl rings which are coordinated in a η5 fashion are rotated in opposite directions around the Si−C(bridgehead) bond, leading to the trans arrrangement of the metal fragments and giving rise to a long ruthenium−ruthenium distance (6.120(6) Å). Complex 4c has been used as a precursor in a series of halide and carbonyl substitution reactions. The reaction of 4c with the cuprate derivative Li[CuMe2] in THF leads to the exchange of both iodide anions to give the dimethyl complex [Ru2(μ-(η5-C5H4)2SiMe2}(CH3)2(CO)4] (5). The treatment of complex 4c with AgBF4 in refluxing acetonitrile leads to halide abstraction to afford the cationic complex [Ru2{μ-(η5-C5H4)2SiMe2}(CO)4(NCMe)2][BF4]2 (9). The analogous reaction of complexes 4a−c with AgBF4 in CH2Cl2 or acetone at room temperature gives the cationic double-bridged derivatives [Ru2{μ-(η5-C5H4)2SiMe2)}(μ-X)(CO)4][BF4] (10a−c). The X-ray crystal structure of 10b shows the two ruthenium moieties bridged by a halogen atom, forcing a cisoid arrangement in the molecule. Irradiation of a solution of 4c and PCy3 in THF leads to carbonyl substitutions to yield the monocarbonyl complex [Ru2{μ-(η5-C5H4)2SiMe2}(I)2(CO)2(PCy3)2] (6c). Analogous isocyanide carbonyl substituted complexes [Ru2{μ-(η5-C5H4)2SiMe2}(I)2(CNR)x(CO)4-x] (R = CH2Ph, x = 1 (7a), x = 2 (7b), x = 3 (7c), x = 4 (7d); R = Cy, x = 1 (8a), x = 2 (8b), x = 3 (8c), x = 4 (8d)) have been obtained by UV irradiation of 4c and the corresponding isocyanide in THF, depending on the ligand:complex ratio.

A Novel Highly Charged (+12) Anion Receptor That Encapsulates Simultaneously NO3− and PF6− Ions

Coordination of (en)PdII entities (en = ethylenediamine) forces the two pyrazine halves of the 2,2′-bipyrazine ligands (bpz) of the molecular triangle [{(en)Pt(bpz))}3]6+ to adopt a cisoid arrangement. The resulting cationic (+12) complex [{(en)Pt(bpz)Pd(en)}3]12+ (see picture) displays a pronounced affinity for anions and encapsulates simultaneously NO3− and PF6− ions, which has been confirmed by X-ray structural analysis.

Synthesis and characterization of new ruthenium(II) complexes containing diisopropylmethylphosphine

The reaction between RuCl3 and PiPr2Me in 2-methoxyethanol yielded the five-co-ordinate complex [RuCl2(CO)(PiPr2Me)2] in which the phosphine groups show a cisoid arrangement. The co-ordination sphere of the ruthenium nucleus can be completed with neutral ligands such as CO, tBuNC, Hpz, 3,5-dimethylpyrazole and HNCPh2. Likewise, it reacts with S-donor reagents like PhSH and 2-sulfanylpyridine and readily undergoes metathesis reactions with salts of some chelating ligands like NaS2CNEt2, KS2COR (R = Me, Et or iPr) and K(acac) which are bonded in a bidentate mode.

(±)-6,7-Dihydro-1,6,11-trimethyl-5H-dibenz[c,e]azepine

In the title compound, C17H19N, the central seven-membered azepine ring adopts a twisted boat conformation. The molecule exhibits a huge deviation from planarity by rotation of the two fused ortho-methyl-substituted phenyl rings around the central C12—C14 single bond. The dihedral angle between the planes of these two rings amounts to 56.05 (4)° with a cisoid arrangement around the C12—C14 bond. Because of this non-planarity, the molecule is axially chiral.

Phosphonous acid dichlorides and tricyclic phosphoranes from hexafluoro- and trifluoropentane-2,4-dione

1,1,1,5,5,5-Hexafluoro-2-hydroxy-2-pentene-4-one reacted diastereospecifically with phosphonous acid di-chlorides, RPCl2 (R = Me, Et, iPr, tBu, Me3SiCH2, PhCH2, Ph) to give in a concerted mechanism thermally stable tricyclic λ5σ5P phosphoranes containing two five- and one six-membered ring. In one case, hydrolysis gave 3,5-dihydroxy-2-oxo-1,2λ5σ4-oxaphosphalane, whereas methanol added to the double bond in the six-membered ring furnishing two isomeric phosphoranes. When 1,1,1-trifluro-2-hydroxy-2-pentene-4-one was reacted with RPCl2 (R = Et, Me3SiCH2, PhCH2, Ph), diastereomerically pure regioisomeric phosphoranes were obtained. The solid-state molecular structures of three λ5σ5P species exhibited two oxygen atoms in the axial position of a slightly distorted trigonal-bipyramidal geometry at phosphorus. Surprisingly, the two CF3 groups bonded to an sp3-hybridized carbon were in a cisoid arrangement, having closest nonbonding F · · · F distances of 301.4 or 273.5 pm. These findings reflect the “through-space” F-F coupling constants of the tricyclic phosphoranes (JFF = 4.0–7.0 Hz) in solution. The solid-state structure of the phospholane revealed the two hydroxy groups to be directed to one side of the five-membered ring. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:173–181, 1998

Preparation and Anti‐Tumour Activity of Some Arylbismuth(III) Oxine Complexes

New arylbismuth(lll) oxinates, PhBi(MeOx)2, (p-MeC6H4)Bi(Ox)2, (p-MeC6H4)Bi(MeOx)2, (p-ClC6H4)Bi(Ox)2, and (p-ClC6H4)Bi(MeOx)2 (Ox− = quinolin-8-olate and MeOx−=2-methylquinolin-8-olate) have been prepared by reaction of the appropriate diarylbismuth chlorides with Na(Ox) or Na(MeOx) in the presence of 15-crown-5. An X-ray crystallographic study has shown PhBi(MeOx)2 to be a five coordinate monomer with distorted square pyramidal stereochemistry. Chelating MeOx ligands have a cisoid arrangement in the square plane and the phenyl group is apical. The lattice is stabilised by significant π-π interactions between centrosymmetric molecules. A range of these complexes has been shown to have high in vitro biological activity (comparable with or better than cisplatin) against L1210 leukaemia, the corresponding cisplatin resistant line, and a human ovarian cell line, SKOV-3. However, initial in vivo testing against a solid mouse plasmacytoma (PC6) and P388 leukaemia has not revealed significant activity.

Co-ordination of hydrazine and substituted hydrazines on reaction with [Rh2(CO)4Cl2] and disproportionation of 1,2-N2H2Ph2

The progressive addition of hydrazine and the following increasingly substituted hydrazines L (N2H4 Ia, H2NNHMe Ib, H2NNHPh Ie, H2NNMe2 Id, or MeHNNHMe Ic) to [Rh2(CO)4Cl2] resulted in the initial formation of [{Rh(CO)2Cl}2(µ-L)] 1 followed by the formation of cis-[Rh(CO)2L(Cl)] 2; analogous mononuclear complexes were formed directly on addition of the more heavily substituted hydrazines Me2NNMe2 IIf and H2NNPh2 IIg, but addition of 1,2-N2H2Ph2 IIIh to [Rh2(CO)4Cl2] resulted in disproportionation of the hydrazine and formation of cis-[Rh(CO)2(NH2Ph)Cl] 3 and cis-[Rh(CO)2(PhNNPh)Cl] 4. The above complexes have been spectroscopically characterised by IR and 13C/15N NMR measurements. X-Ray structural analysis on [{Rh(CO)2Cl}2(µ-L)] (L = H2NNHMe or MeHNNHMe) confirmed that L adopts a µ-η1∶η1-mode of bonding with a cisoid arrangement of the Rh(CO)2Cl groups about the N–N bond.

The Reduction of Oxalic Amidines with Metallic Lithium: Preparation of Lithiated Bisamides [R″N(RR′N)C=C(NRR′)NR″]Li2 and Their Use as Intermediates in a Novel Synthesis of Tetraaminoethenes

AbstractReduction of the 1,4‐diaza‐1,3‐butadiene substructure of hexasubstituted oxalic amidines with lithium metal yields the new lithium diamides 3. Subsequent reaction of 3 with various electrophiles gives the title substances 4, 5, and the acylated derivative 6, respectively. The first SET step in this reaction is the formation of monolithium radical anions 2, which were detected by EPR spectroscopy. The second electron transfer leads to the deeply colored dianions 3. – In the case of compound 3a [cis‐3a · 3 Et2O], the X‐ray crystal structure reveals the cisoid arrangement of the bidental ligand and three molecules of diethyl ether which are located in a 2:1 fashion in the first coordination sphere of the lithium cations. The NMR 2D‐1H,6Li‐HOESY investigations of 3a in [D10]diethyl ether/diethyl ether (8:1) show Li+ contacts to the hydrogen atoms of the ether molecules and to the ortho‐hydrogen atoms of the aryl moieties. Results of semiempirical calculations (PM3) are throughout in acceptable agreement with the experimental data and explain the unusual coordination pattern of the lithium cations of compounds 3.