An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The interionic structure of complexes [Ru(eta(6)-Arene){(2-R-C6H4)N = C(Me)-C(Me)= N(2-R-C6H4)}Cl]X was investigated by an integrated experimental (PGSE diffusion and NOE NMR spectroscopy and X-ray single-crystal studies) and theoretical (DFT and ONIOM calculations) approach. PGSE NMR experiments indicated that ion pairing is the main aggregative process in CD2Cl2 and solvents with higher relative permittivity. They also showed that the tendency to ion pairing for isodielectric solvents is higher when the latter are protic. NOE interionic contacts were observed in 2-propanol-d(8) even for BARF(-) salts. Ion pairing was favored by more coordinating counterions and an increase in concentration. An equilibrium between ion pairs and ion quadruples was observed by PGSE measurements in chloroform-d and benzene-d(6). Such equilibrium is shifted toward ion quadruples by an increase in the concentration or when least coordinating counterions are used. For small fluorinated counterions, NOE studies located the anion in ion pairs above the plane containing the C = N imine moieties. ONIOM calculations found that this anion-cation orientation was at least 35.9 kJ/mol lower in energy than a second orientation with the anion close to cymene, which, in some cases, was observed in the solid state. NOE investigations on complexes with BPh4- counterion did not allow a single orientation capable of explaining the observed NOEs to be found. X-ray studies showed that one cation is surrounded by two anions. ONIOM calculations found that these two anion-cation orientations have similar energies. X-ray and NOE NMR data strongly suggest that ion quadruples with BPh4- anions are constituted by an alternation of cations and anions. Interionic NOE intensities are almost invariant on passing from ion pairs to ion quadruples with small fluorinated counterions. X-ray studies suggested at least four possible structures of ion quadruples differing in both disposition and orientation of the ionic moieties. Three structures considered by ONIOM calculations were similar in energy, but more stable than the separated ion pairs.

Palladacyclic compounds [Pd(C6H4(C6H5C=O)C=N-R)(N-N)] [X] (R = Et, Pr-i, 2,6-(Pr2C6H3)-Pr-i; N-N=bpy=2,2'-bipyridine, or 1,4-(o,o'-dialkylaryl)-1,4-diazabuta-1,3-dienes; [X](-)=[BF4](-) or [PF6](-)) were synthesized from the dimers [(Pd(C6H4(C6H5C=O)C=N-R)(mu-Cl)}2] and N-N ligands. Their interionic structure in CD2Cl2 was determined by means of F-19,H-1-HOESY experiments and compared with that in the solid state derived from X-ray single-crystal studies. [Pd(C6H4(C6H5C=O)C=N-R)(N-N)[X] complexes were found to copolymerize CO and p-methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4-(o,o'-dimethylaryl)-1,4-diazabuta-1,3-dienes were used, respectively. The reactions with CO and p-methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd-C bonds were isolated and completely characterized in solution.

The catalytic activity and stereoselectivity of complexes [Pd(eta(1),eta(2)-C(8)H(12)OMe)(Ar--N==C(R')--C(R')==N--Ar)]X in the copolymerization of CO and p-methylstyrene have been correlated with their interionic structure in solution and in the solid state, as determined by (19)F,(1)H-HOESY NMR spectroscopy and X-ray diffraction studies, respectively. The highest productivity is obtained with unhindered diimine ligands bearing electron-donating substituents and with the least coordinating counterion. Copolymers with a microstructure ranging from atactic to predominantly isotactic are obtained. The degree of isotacticity increases as the steric hindrance in the apical positions and the coordinating ability of the counterion increase. The counterion is located close to the diimine in both solution and the solid state but it moves toward the palladium as the steric hindrance in the apical positions decreases. When the latter is small the counterion competes with the substrate for apical coordination, and consequently it affects the productivity. In the case of ortho-dimethyl-substituted ligands the counterion is confined in the back, above the N==C(R')--C(R')==N moiety, and does not affect the productivity. However, it contributes to increasing the stereoregularity of the copolymer by making the aryl moieties more rigid. With R'=Me and Ar=o-Me(2)C(6)H(3) an ll of 81 % and 72 % was obtained with X(-)=CF(3)SO(3) (-) or BArF(-), respectively. The isotacticity of the copolymers produced by ortho-monosubstituted catalysts depends greatly on the counterion and ranges from 30 % to 59 % with X(-)=BArF(-) and X(-)=CF(3)SO(3) (-), respectively, with Ar=o-EtC(6)H(4) and R'=Me. Based on the interionic structural results, this effect can be explained by a greater reduction of the copolymerization rate of C(s)-symmetric isomers with respect to their C(2)-symmetric counterparts.

The aggregation tendency of complexes [Ru(eta6-cymene)(N,O)Cl]X [N,O = 2-benzoylpyridine (2-bzpy), 1, and 2-acetylpyridine (2-acpy), 2, X- = BPh4- or PF6-] has been studied by means of PGSE NMR experiments. It was found that complexes with PF6- as counterion are mainly present in CD2Cl2 as ion pairs at low concentration, as a mixture of ion triples and free anions at medium concentration and as ion quadruples at elevated concentration. 19F, 1H-HOESY NMR experiments revealed that in ion triples and ion quadruples two cationic Ru-units pair up. Consistently, in the solid-state structure of 1PF6, determined through X-ray single-crystal investigation, two cationic Ru-units are held together by an intermolecular pi-pi stacking interaction between the pyridyl rings. Complexes having BPh4- as counterion are only present in solution as even aggregates, namely ion pairs at low concentration and ion quadruples at elevated concentration. In such a case a counteranion bridges two cationic Ru-units as observed in the solid-state structure of 1BPh4. The reactivity of complexes 1-2 toward AgX salts has been investigated in different solvents. Bicationic [Ru(eta6-cymene)(N,O)(MeCN)]X2 (N,O = 2-bzpy, 3, and 2-acpy, 4) and [Ru(MeCN)4(N,O)]X2 (N,O = 2-bzpy, 5, and 2-acpy, 6) complexes were obtained by the reaction of 1 and 2 with AgX in the presence of three equivalents of acetonitrile or in acetonitrile, respectively. The reaction of 1 with AgPF6 in acetone afforded complex [Ru(eta6-cymene)(N,O,O)]PF6 (7, where N,O,O = 4-alcoxide-4-phenyl-4-(pyridin-2-yl)butan-2-one) from the C-C coupling of a deprotonated methyl group of the coordinated acetone and the C=O moiety of 2-bzpy ligand.

(S)-2-Pyridyl-imino-[2.2]paracyclophane ligands 1 and 2 were synthesized by a condensation reaction of 2-COR-C5H4N (1: R = H; 2: R = Me) with enantiopure (-)-S-amino-[2.2]-paracyclophane. The reactions of 1 and 2 with [Ru(mu(6)-cymene)Cl(p-Cl)]2 afforded complexes [Ru(eta(6)-cymene)Cl(N,N)]X (3: N,N = 1; 4: N,N = 2; X- = BPh4-, PF6-, BF4-) that were completely characterized in solution. For 4PF(6) the solid state structure was determined by X-ray single-crystal diffractometric studies. Two diastereoisomers [(S-Ru, S-L) and (R-Ru, S-L)] were obtained in solution due to the presence of the planar chirality of paracyclophane (L) and the central chirality on ruthenium. H-1-NOESY NMR experiments were used to determine the chirality of the metal center and, consequently, to identify (S-Ru, S-L) and (R-Ru, S-L) diastereoisomers. The cymene orientation, obtained by intramolecular 1H-NOESY NMR investigations, and the relative anion-cation position, determined by interionic H-1-NOESY or F-19,H-1-HOESY NMR studies, depended on the nature of the diastereoisomer. (c) 2005 Elsevier B.V. All rights reserved.

Fe(CO)(4)X-2 complexes [X = I (1), Br(1')] react with phosphine ligands L (L = PMe3, PEt3, PMe2Ph, PMePh2, PPh3) via a two-step mechanism: in the first step fac-Fe(CO)(3)LX2 Complexes are formed; in the second step two parallel pathways, a and b, are observed; in pathway a, reductive elimination with formation of equimolar amounts of Fe(CO)(3)L-2 (5) and phosphonium salts [LX]X-+(-) is observed; in pathway b, disubstituted dihalide complexes cis,trans,cis-Fe(CO)(2)L2X2 are formed. The relative weights of pathways a and b depend on the basicity, steric hindrance and concentration of ligand L, on the nature of the halogen and on temperature. A radical mechanism which accounts for most of the experimental results is proposed. (c) 2006 Elsevier B.V. All rights reserved.

Complexes cis, trans-Fe(CO)(2)(PMe3)(2)RR' (R = CH3, R' = Ph (2); R = CH3, R' = CH =CH2 (3); R = CH = CH2, R' = Ph (4); R = R' = CH = CH2 (5); R = R = CH3 (6)) were prepared by reaction of cis,trans-Fe(CO)(2)(PMe3)(2)RCl (1) with organolithium reagents LiR'. All complexes were characterized in solution by IR and H-1, P-31 and, in a few cases, C-13 NMR mono- and bi-dimensional spectroscopies. Complexes 5 and 6 were structurally characterized by X-ray diffractometric methods. In solution complexes 2, 3 and 4 undergo slowly coupling of the sigma-hydrocarbyl substituents leading to Fe(CO)(3)(PMe3)(2) and other decomposition products. Complex 6 was very stable in solution in the absence of nucleophiles and in the solid state. Complex 5 transformed through intramolecular coupling of the vinyl groups into Fe(CO)(PMe3)(2)(eta(4) -butadiene) (7), which was characterized in solution by IR and NMR spectroscopies. (c) 2005 Elsevier B.V. All rights reserved.

Syntheses and structures of octahedral vinyl halide and aryl halide complexes of iron are reported by reaction of dihalide complexes of iron with Grignard and lithium vinyl and aryl reagents. The effect of halide, Grignard and lithium reagents on the reaction yield is discussed.

PGSE and NOE NMR measurements were carried out for complexes [Ru(eta(6)-cymene)((2-R-C(6)H(4))N=C(Me)-C(Me)=N(2-R-C(6)H(4)))Cl]X (X = BF(4) or BPh(4)) in both protic and aprotic solvents with a relative permettivity (epsilon(r)) ranging from 2.27 (benzene-d(6)) to 46.45 (dimethyl sulfoxide-d(6)). PGSE and NOE results indicate that complexes have a tendency to aggregate even in medium-polarity solvents such as ethanol (epsilon(r) = 24.55) and methanol (epsilon(r) = 32.66). In addition, the aggregation process is favored by a decrease of epsilon(r) and, unexpectedly, by protic solvents. NOE measurement investigations, interpreted with the help of theoretical calculations and confirmed by X-ray single crystal studies, suggest different aggregation processes for the two counteranions: two cationic moieties approach each other when X = BF(4) while the anion bridges two cationic moieties when X = BPh(4).

The reactions of cis,trans-[M(CO)2(PMe3)2CH3I] [M=Fe (1), Ru (2)] and cis,trans,cis-[Fe(CO)2(PMe3)2(CH3)2] (3) with B(C6F5)3 involve Me-abstraction from the metal with formation of reactive species that undergo decomposition processes. In the presence of H2O complex 2 reacts with B(C6F5)3 forming cis,trans-[Ru(CO)2(PMe3)2I(HOB(C6F5)3)] (7) that slowly transforms in cis,trans-[Ru(CO)2(PMe3)2I(H2O)]+[(HOB(C6F5)3)]− (8), while complex 1 affords the cyclometallate complex trans-[Fe(CO)(PMe3)2I(C(Me)OB(C6F5)2OH)] (9) whose molecular structure was investigated by X-ray diffraction studies.

Complexes [M(eta(1),eta(2)-C8H12OMe)(pz(2)-YH2)]((+)) (M = Pd, Y = C, 1; M = Pt, Y = C, 2; M = Pt, Y = B, 3) and [M(eta(1),eta(2)-C8H12OMe)(pz(3)-YH)]((+)) (M = Pd, Y = C, 4; M = Pd, Y = B, 5; M = Pt, Y = C, 6; M = Pt, Y = B, 7) were synthesized by the reaction of the dimers [M(eta(1),eta(2)-C8H12OMe)Cl](2) with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1-7 were characterized in solution by multinuclear and multidimensional low-temperature NMR spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were investigated by X-ray single-crystal studies. The relative cation-anion position (interionic structure) was investigated in solution, for all cationic complexes at room and low temperature by (IF)-I-19, H-1-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable specifity of the interionic contacts is observed in solution: the counterion is placed close to the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the apical positions introduced by the nonplanar ligands and the delocalization of the positive charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement between the solid state and solution results: the anion selectively interacts with the CH and five protons of the pz(3)-CH ligand via an assembly of hydrogen bonds.

Complexes [M(η1,η2-C8H12OMe)((2,6-(R)2C6H3)NC(R′)C(R′)N((2,6-(R)2C6H3))]PF6 (where M=Pd, R=H and R′2=Me2 (1), M=Pd, R=Me and R′2=Me2 (2), M=Pd, R=Et and R′2=Me2 (3), M=Pd, R=iPr and R′2=Me2 (4), M=Pd, R=iPr and R′2=An (5), M=Pt, R=iPr and R′2=An (6)) were synthesized by the reaction of [M(η1,η2-C8H12OMe)Cl]2 with the appropriate α-diimine ligand in the presence of NH4PF6. Their ion pair structure in solution was investigated by detecting dipolar interactions between protons belonging to the cation and fluorine nuclei of the anion (interionic contacts) in the 19F, 1H-HOESY NMR spectra. In complexes 1–4, the anion in solution is located close to the peripheral protons of the α-diimine ligand and it interacts with the R′ protons and with the R protons that point toward the R′ groups. The steric protection of apical position exerted by the R substituents is clearly illustrated by the absence of interionic contacts between any protons of the cycloctenylmethoxy-moiety and the anion for R≥Me in 1–4. In complexes 5 and 6 the interactions between the anion and the peripheral N,N protons also predominate but other anion–cation orientations are significantly present and, consequently, the interionic structure is less specific.

Complexes trans-[Ru(PMe3)2(CO)(COMe)(N,N)]X (N,N = diimine or diamine ligand, X− = BF4− or BPh4−) have been synthesized by the reaction of cis,trans-[RuI(Me)(CO)2(PMe3)2] with N,N ligands having different steric and electronic properties. The syntheses were only successful with moderately hindered ligands; in other cases, solvento complexes were formed. Some of these were isolated and characterized. The interionic structures of the aforementioned cationic complexes have been investigated in dichloromethane solution by means of 1H-NOESY and 19F{1H}-HOESY NMR experiments. The anion−cation interactions (especially for the diamine complexes) were found to be more specific than those in analogous compounds bearing aromatic N,N ligands. For the first time, we have found that the anion preferentially resides close to the N arm trans to the COMe group.

The structure of the Ru(II) ion pairs trans-[Ru(COMe)[(pz(2))CH(2)](CO)(PMe(3))(2)]X (X(-) = BPh(4)(-), 1a; BPh(3)Me(-), 1b; BPh(3)(n-Bu)(-), 1c; BPh(3)(n-Hex)(-), 1d; B(3, 5-(CF(3))(2)(C(6)H(3)))(4)(-), 1e; PF(6)(-), 1f; and BF(4)(-), 1g; pz = pyrazol-1-yl-ring) was investigated in solution from both a qualitative (chloroform-d, methylene chloride-d(2), nithromethane-d(3)) and quantitative (methylene chloride-d(2)) point of view by performing 1D- and 2D-NOE NMR experiments. In particular, the relative anion-cation localization (interionic structure) was qualitatively determined by (1)H-NOESY and (19)F, (1)H-HOESY (heteronuclear Overhauser effect spectroscopy) NMR experiments. The counteranion locates close to the peripheral protons of the bispyrazolyl ligand independent of its nature and that of the solvent. In complexes 1c and 1d bearing unsymmetrical counteranions, the aliphatic chain points away from the metal center as indicated by the absence of NOE between the terminal Me group and any cationic protons. An estimation of the average interionic distances in solution was obtained by the quantification of the NOE build-up versus the mixing time under the assumption that the interionic and intramolecular correlation times (tau(c)) are the same. Such an assumption was checked by the experimental measurements of tau(c) from both the dipolar contribution to the carbon-13 longitudinal relaxation time T(DD-1)and the comparison of the intramolecular and interionic cross relaxation rate constant (sigma) dependence on the temperature. Both the methodologies indicate that anion and cation have comparable tau(c) values. The determined correlation time values were compared with those obtained for the neutral trans-[Ru(COMe)[(pz(2))BH(2)](CO)(PMe(3))(2)] complex (2), isosteric with the cation of 1. They were significantly shorter (approximately 3.8 times), indicating that the main contribution to dipolar relaxation processes comes from the overall ion pair rotation. As a consequence, the determined average interionic distances appear to be accurate. By using such interionic distances, it was possible to verify that the counteranion in complex 1b also orients the BMe group far away from the metal center.

Complexes trans-[Ru(PMe3)2(CO)(COMe)(N,N)]X (N,N = diimine or diamine ligand, X− = BF4− or BPh4−) have been synthesized by the reaction of cis,trans-[RuI(Me)(CO)2(PMe3)2] with N,N ligands having different steric and electronic properties. The syntheses were only successful with moderately hindered ligands; in other cases, solvento complexes were formed. Some of these were isolated and characterized. The interionic structures of the aforementioned cationic complexes have been investigated in dichloromethane solution by means of 1H-NOESY and 19F{1H}-HOESY NMR experiments. The anion−cation interactions (especially for the diamine complexes) were found to be more specific than those in analogous compounds bearing aromatic N,N ligands. For the first time, we have found that the anion preferentially resides close to the N arm trans to the COMe group.

cis,trans-Os(CO)2(PMe3)2CH3I (1) and fac-[Os(CO)3(PMe3)2CH3]+BPh4− (3) react with borohydrides (NaBH4, NBu4BH4, LiBEt3H) in diethyl ether to form the methyl hydride complex Os(CO)2(PMe3)2(CH3)H (7). Similarly the monosubstituted fac-Os(CO)3(PMe3)CH3I (9) reacts with borohydrides to give fac-Os(CO)3(PMe3)(CH3)H (10). The isoelectronic complexes of iron cis,trans-Fe(CO)2(PMe3)2CH3I (2) and fac-[Fe(CO)3(PMe3)2CH3]BPh4 (4) give instead the dihydride complex cis,trans-Fe(CO)2(PMe3)2H2 (8). Complexes (1)–(4) react with lithium methyl to form the dimethyl complexes cis,trans-M(CO)2(PMe3)2(CH3)2 [M=Os (5), Fe (6)]. The structures of the complexes are studied by IR and 1H-, 13C{1H}-, 31P{1H}-NMR spectroscopies. The different results are explained on the basis of a fast reductive elimination reaction in the case of iron and a fast decarbonylation reaction in the case of osmium.

The equilibrium and kinetics of isocyanide insertion of complexes [Fe(PMe3)2(CO)2(CH3)(CNR)]+X− (1) [CNR=tert-butylisocyanide; X−=I− (1a), BPh4− (1b); BF4− (1c)] which afford complexes [Fe(PMe3)2(CO)2(η2-C(CH3)NC(CH3)3)]+X− (2) were investigated in dichloromethane, methanol, acetone and nitromethane. The results indicate that the reaction proceeds via an associative mechanism with the preliminary formation of contact ion pairs. The structure of the contact ion pair in solution was studied by 1H-NOESY and 19F{1H}-HOESY NMR spectroscopy. The results indicate that structure is independent of the nature of the solvent and of the counterion. In complexes 1b,c the counterion is located between the CO and the isocyanide ligands; in complexes 2b,c the counterion is located near the dihaptoiminoacyl ligand. The reaction rate increases with the charge density and the coordinating power of the anions. The effect of the solvent can be also explained on the basis of its coordinating power.

The molecular self-diffusion coefficients of the complexes trans-[Ru(PMe3)(2)(CO)(COMe)(pz(2)-CH2)]BPh4 and trans-[Ru(PMe3)(2)(CO)(COMe)(pz(2)-BH2)] have been measured by pulsed field gradient spin-echo NMR measurements in nitromethane, chloroform, and methylene chloride as a function of concentration. By using the neutral complex as reference with the assumption that it does not undergo associative processes, clear indications of the presence of ions tin nitromethane), ion pairs fin chloroform at low concentration), and ion quadruples tilt chloroform at high concentration) have been obtained.