Probing the Antiaromaticity and Coordination Chemistry of Bowl-Shaped Zinc(II) Norcorrole.

Zinc norcorrole was prepared as its pyridine complex (ZnNc·pyridine) by metalation of freebase norcorrole. The ZnNc·pyridine complex is distinctly bowl-shaped, as demonstrated by both X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopy showed characteristic ring current deshielding effects, with different magnitudes on either face of the bowl-shaped complex. Exchanging the pyridine ligand with the bidentate ligand DABCO results in the formation of a stable (ZnNc)2·DABCO sandwich complex, which was also characterized by crystallography and NMR spectroscopy. The NMR resonances of the axial ligands in all of the complexes demonstrate that the paratropic ring current in zinc norcorrole is approximately 40 nA/T, which is comparable in magnitude to the diatropic ring current in porphyrin. Analysis of the ligand-exchange processes on addition of DABCO to ZnNc·pyridine showed that ZnNc coordinates to axial nitrogen-containing ligands with approximately 1000-fold higher binding constants than analogous zinc porphyrins.

Spin Crossover Induced by Changing the Identity of the Secondary Metal Ion from PdII to NiII in a Face-Centered FeII 8 MII 6 Cubic Cage.

Discrete spin crossover (SCO) heteronuclear cages are a rare class of materials which have potential use in next-generation molecular transport and catalysis. Previous investigations of cubic cage [Fe8 Pd6 L8 ]28+ constructed using semi-rigid metalloligands, found that FeII centers of the cage did not undergo spin transition. In this work, substitution of the secondary metal center at the face of the cage resulted in SCO behavior, evidenced by magnetic susceptibility, Mössbauer spectroscopy and single crystal X-ray diffraction. Structural comparisons of these two cages shed light on the possible interplay of inter- and intramolecular interactions associated with SCO in the NiII analogue, 1 ([Fe8 Ni6 L8 (CH3 CN)12 ]28+ ). The distorted octahedral coordination environment, as well as the occupation of the CH3 CN in the NiII axial positions of 1, prevented close packing of cages observed in the PdII analogue. This led to offset, distant packing arrangements whereby important areas within the cage underwent dramatic structural changes with the exhibition of SCO.

Unusual Alternating Crystallization-Induced Emission Enhancement Behavior in Nonconjugated ω-Phenylalkyl Tropylium Salts.

The alternating physical properties, especially melting points, of α,ω-disubstituted n-alkanes and their parent n-alkanes had been known since Baeyer's report in 1877. There is, however, no general and comprehensive explanation for such a phenomenon. Herein, we report the synthesis and examination of a series of novel ω-phenyl n-alkyl tropylium tetrafluoroborates, which also display alternation in their physicochemical characters. Despite being organic salts, the compounds with odd numbers of carbons in the alkyl bridge exist as room temperature ionic liquids. In stark contrast to this, the analogues with even numbers of carbons in the linker are crystalline solids. These solid nonconjugated molecules exhibit curious photoluminescent properties, which can be attributed to their ability to form through-space charge-transfer complexes to cause crystallization-induced emission enhancement. Most notably, the compound with the highest photoluminescent quantum yield in this series showed an unusual arrangement of carbocationic dimer in the solid state. A combination of XRD analysis and ab initio calculations revealed interesting insights into these systems.

A Rare Example of a Complete, Incomplete, and Non-Occurring Spin Transition in a [Fe2L3]X4 Series Driven by a Combination of Solvent-and Halide-Anion-Mediated Steric Factors.

A trend between the degree of steric congestion of the Fe(II) coordination environment and the extent of spin transition (percentage completeness) has been observed in a series of halide salts of a dinuclear triple helicate architecture with the general form [Fe2L3]X4 (where X = Cl- for 1, Br- for 2, and (I-)3/I3- for 3, and L is (1E,1'E)-N,N'-(oxybis(4,1-phenylene))bis(1-(1H-imidazol-4-yl)methanimine). Crystal packing densities of adjacent helicates were found to decrease with increasing anion size. Greater steric congestion by neighboring helicates favored the [HS-HS] state of the dinuclear triple helicate architecture. As a result, the highly crowded Cl- salt (1) did not undergo spin-crossover (SCO), the more congested Br- salt (2) underwent an incomplete solvent-dependent transition, and the least crowded (I-)3/I3- analogue (3) exhibited a full SCO from the [HS-HS] ↔ [LS-LS] state. Furthermore, an interesting two-step transition was observed in the Br- salt, exhibiting a 28 K thermal hysteresis in the higher temperature step, the largest thermal hysteresis reported to date for a Fe(II) dinuclear triple helicate system. Variable-temperature single-crystal X-ray diffraction (SCXRD) analysis of 2 demonstrated that this two-step profile was found to be the result of crystallographic parameters evolving in a two-step manner with temperature, rather than a crystallographic phase change.

Guest Removal and External Pressure Variation Induce Spin Crossover in Halogen-Functionalized 2-D Hofmann Frameworks.

The effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [FeIIPd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1Cl·2H2O and 2Br·2H2O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest removal or the application of external physical pressure. Notably, removal of solvent water reveals a robust framework scaffold with only marginal variation between the solvated and desolvated structures (as investigated by powder and single crystal X-ray diffraction). Yet, one-step complete SCO transitions are revealed in 1Cl and 2Br with a transition temperature shift between the analogues due to various steric, structural, and electronic considerations. SCO can also be induced in the solvated species, 1Cl·2H2O and 2Br·2H2O, with the application of physical pressure, revealing a complete one-step SCO transition above 0.62 GPa (as investigated by magnetic susceptibility and single crystal X-ray diffraction measurements).

Gel- and Solid-State-Structure of Dialanine and Diphenylalanine Amphiphiles: Importance of C⋠⋠⋠H Interactions in Gelation.

To investigate the role of the capping group in the solution and solid-state self-assembly of short peptide amphiphiles, dialanine and diphenylalanine have been linked via the N-terminus to a benzene (phenyl) and 3-naphthyl capping groups using three different methylene linkers; (CH2 )n , n=0-4 for the benezene and 0, 1 and 2 for the naphthalene capping group. Atomic force microscopy (AFM), oscillatory rheology, circular dichroism (CD), and IR analysis have been employed to understand the properties of these peptide-based hydrogels. Several X-ray structures of these short peptide gelators give useful conformational information regarding packing. A comparison of these solid state structures with their gel state properties yielded greater insights into the process of self-assembly in short peptide gelators, particularly in terms of the important role of C⋅⋅⋅H interactions appear to play in determining if a short aromatic peptide does form a gel or not.

Investigation of the High-Temperature Spin-Transition of a Mononuclear Iron(II) Complex Using X-ray Photoelectron Spectroscopy.

This study presents a new mononuclear complex (1) of the form [FeL](BF4)2, incorporating the thiazolylimine donor moiety, which was found to exhibit a high-temperature spin-transition. The effect of scan rate was investigated, with magnetic susceptibility being measured at 4, 2, and 1 K min-1. The magnetic susceptibility results were confirmed by variable temperature X-ray photoelectron spectroscopy (XPS) (100, 270, 400, and 500 K) and single crystal X-ray diffraction (150 and 400 K) experiments. A rare example of a high-temperature (400 K) single crystal structure of 1 has been reported. The high-spin fraction was calculated indirectly from XPS data, presenting a method for analyzing the spin-state in the surface layers of spin-crossover materials.

Synthesis and biological evaluation of novel acyclic and cyclic glyoxamide based derivatives as bacterial quorum sensing and biofilm inhibitors.

Bacteria regulate the expression of various virulence factors and processes such as biofilm formation through a chemically-mediated communication mechanism called quorum sensing. Bacterial biofilms contribute to antimicrobial resistance as they can protect bacteria embedded in their matrix from the effects of antibiotics. Thus, developing novel quorum sensing inhibitors, which can inhibit biofilm formation, is a viable strategy to combat antimicrobial resistance. We report herein the synthesis of novel acyclic and cyclic glyoxamide derivatives via ring-opening reactions of N-acylisatins. These compounds were evaluated for their quorum sensing inhibition activity against P. aeruginosa MH602 and E. coli MT102. Compounds 20, 21 and 30 displayed the greatest quorum sensing inhibition activity against P. aeruginosa MH602, with 71.5%, 71.5%, and 74% inhibition, respectively, at 250 µM. Compounds 18, 20 and 21 exhibited the greatest QSI activity against E. coli MT102, with 71.5%, 72.1% and 73.5% quorum sensing inhibition activity, respectively. In addition, the biofilm inhibition activity was also investigated against P. aeruginosa and E. coli at 250 µM. The glyoxamide compounds 16, 18 and 19 exhibited 71.2%, 66.9%, and 66.5% inhibition of P. aeruginosa biofilms, respectively; whereas compounds 12, 20, and 22 showed the greatest inhibitory activity against E. coli biofilms with 87.9%, 90.8% and 89.5%, respectively. Finally, the determination of the in vitro toxicity against human MRC-5 lung fibroblast cells revealed that these novel glyoxamide compounds are non-toxic to human cells.

A Capped Dipeptide Which Simultaneously Exhibits Gelation and Crystallization Behavior.

Short peptides capped at their N-terminus are often highly efficient gelators, yet notoriously difficult to crystallize. This is due to strong unidirectional interactions within fibers, resulting in structure propagation only along one direction. Here, we synthesize the N-capped dipeptide, benzimidazole-diphenylalanine, which forms both hydrogels and single crystals. Even more remarkably, we show using atomic force microscopy the coexistence of these two distinct phases. We then use powder X-ray diffraction to investigate whether the single crystal structure can be extrapolated to the molecular arrangement within the hydrogel. The results suggest parallel ß-sheet arrangement as the dominant structural motif, challenging existing models for gelation of short peptides, and providing new directions for the future rational design of short peptide gelators.

Bio-inspired transition metal-organic hydride conjugates for catalysis of transfer hydrogenation: experiment and theory.

Taking inspiration from yeast alcohol dehydrogenase (yADH), a benzimidazolium (BI(+) ) organic hydride-acceptor domain has been coupled with a 1,10-phenanthroline (phen) metal-binding domain to afford a novel multifunctional ligand (L(BI+) ) with hydride-carrier capacity (L(BI+) +H(-) ⇌L(BI) H). Complexes of the type [Cp*M(L(BI) )Cl][PF6 ]2 (M=Rh, Ir) have been made and fully characterised by cyclic voltammetry, UV/Vis spectroelectrochemistry, and, for the Ir(III) congener, X-ray crystallography. [Cp*Rh(L(BI) )Cl][PF6 ]2 catalyses the transfer hydrogenation of imines by formate ion in very goods yield under conditions where the corresponding [Cp*Ir(L(BI) )Cl][PF6 ] and [Cp*M(phen)Cl][PF6 ] (M=Rh, Ir) complexes are almost inert as catalysts. Possible alternatives for the catalysis pathway are canvassed, and the free energies of intermediates and transition states determined by DFT calculations. The DFT study supports a mechanism involving formate-driven RhH formation (90 kJ mol(-1) free-energy barrier), transfer of hydride between the Rh and BI(+) centres to generate a tethered benzimidazoline (BIH) hydride donor, binding of imine substrate at Rh, back-transfer of hydride from the BIH organic hydride donor to the Rh-activated imine substrate (89 kJ mol(-1) barrier), and exergonic protonation of the metal-bound amide by formic acid with release of amine product to close the catalytic cycle. Parallels with the mechanism of biological hydride transfer in yADH are discussed.

An easy one-pot synthesis of diverse 2,5-di(2-pyridyl)pyrroles: a versatile entry point to metal complexes of functionalised, meridial and tridentate 2,5-di(2-pyridyl)pyrrolato ligands.

A wide variety of 2,5-di(2-pyridyl)pyrroles (dppHs) substituted at the C3 and C4 positions of the pyrrole core were obtained by direct condensation of a 2-pyridylcarboxaldehyde (2 equiv), an α-methylene ketone with at least one electron-withdrawing substituent and ammonium acetate. A novel 2,5-di(1,10-phenanthrolin-2-yl)pyrrole was also characterised. The dppHs provide a direct, quick entry to dipyridylpyrrolato (dpp(-) )-metal complexes. The meridial tridentate dpp(-) ligand is a useful anionic analogue of the terpyridyl ligand. The first (dpp)Ru complexes are described; the 3,4-substitution of the central pyrrole significantly perturbs the potentials of the redox processes of these complexes. A [(dpp)Ru(bpy)(MeCN)](+) (bpy=2,2'-bipyridine) complex is an electrocatalyst for the reductive disproportionation of carbon dioxide to carbon monoxide and the carbonate ion.

Spin crossover of a Fe(II) mononuclear complex induced by intermolecular factors involving chloride and solvent ordering.

Two new salts of a mononuclear tripodal Fe(II) complex were prepared, using ClO4- and Cl-. The ClO4- sample (1) remained HS at low temperatures, similar to the previously reported BF4- analogue. Crystallising with the Cl- anion (2) led to a markedly different crystal packing arrangement, and engendered SCO activity. This has been correlated to the lower crystal packing density in 2 and the coordination complex conformational differences arising due to the packing motifs of 1 and 2. Further, solvent ordering effects have been proposed to facilitate spin transition behaviour in 2.

Low oxidation state iron(0), iron(I), and ruthenium(0) dinitrogen complexes with a very bulky neutral phosphine ligand.

The synthesis of a series of iron and ruthenium complexes with the ligand P(2)P3(Cy), P(CH2CH2PCy2)3 is described. The iron(0) and ruthenium(0) complexes Fe(N2)(P(2)P3(Cy)) (1) and Ru(N2)(P(2)P3(Cy)) (2) were synthesized by treatment of [FeCl(P(2)P3(Cy))](+) and [RuCl(P(2)P3(Cy))](+) with an excess of potassium graphite under a nitrogen atmosphere. The Fe(I) and Ru(I) species [Fe(N2)(P(2)P3(Cy))](+) (3) and RuCl(P(2)P3(Cy)) (4) were synthesized by treatment of [FeCl(P(2)P3(Cy))](+) and [RuCl(P(2)P3(Cy))](+) with 1 equiv of potassium graphite under a nitrogen atmosphere. The cationic dinitrogen species [Fe(N2)H(P(2)P3(Cy))](+) (6) and [Ru(N2)H(P(2)P3(Cy))](+) (7) were formed by treatment of 1 and 3, respectively, with 1 equiv of a weak organic acid. The iron(II) complex Fe(H)2(P(2)P3(Cy)) (5) was also synthesized and characterized. Complexes [RuCl(P(2)P3(Cy))][BPh4], 1, 2, 3[BPh4], 4, 5, 6[BF4], and 7[BF4] were characterized by X-ray crystallography. The Fe(I) and Ru(I) complexes 3 and 4 were characterized by electron paramagnetic resonance (EPR) spectroscopy, and the Fe(I) complex has an EPR spectrum typical of a metal-centered radical.

Structure of racemic duloxetine hydro-chloride.

Duloxetine hydro-chloride (trade name Cymbalta) is marketed as a single enanti-omer (S)-N-methyl-3-(naphthalen-1-yl-oxy)-3-(thio-phen-2-yl)propyl-am-in-ium chloride, C18H20NOS+·Cl-, which is twice as effective as the (R)-enanti-omer in serotonin uptake. Here, we report the crystal structure of duloxetine hydro-chloride in its racemic form (space group Pna21), where it shows significant differences in the mol-ecular conformation and packing in its extended structure compared to the previously reported (S)-enanti-omer crystal structure. Mol-ecules of this type, comprising aromatic groups with a single side chain terminated in a protonated secondary amine, are commonly found in active anti-depressants. A Cambridge Structural Database survey of mol-ecules with these features reveals a strong correlation between side-chain conformation and the crystal packing: an extended side chain leads to mol-ecules packed into separated layers of hydro-phobic and ionic hydro-philic phases. By comparison, mol-ecules with bent side chains, such as racemic duloxetine hydro-chloride, lead to crystal-packing motifs where an ionic hydro-philic phase is encapsulated within a hydro-phobic shell.

New superhindered polydentate polyphosphine ligands P(CH2CH2P(t)Bu2)3, PhP(CH2CH2P(t)Bu2)2, P(CH2CH2CH2P(t)Bu2)3, and their ruthenium(II) chloride complexes.

The synthesis and characterization of the extremely hindered phosphine ligands, P(CH(2)CH(2)P(t)Bu(2))(3) (P(2)P(3)(tBu), 1), PhP(CH(2)CH(2)P(t)Bu(2))(2) (PhP(2)P(2)(tBu), 2), and P(CH(2)CH(2)CH(2)P(t)Bu(2))(3) (P(3)P(3)(tBu), 3) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl(2)(P(2)P(3)(tBu)) (4), RuCl(2)(PhP(2)P(2)(tBu)) (5), and RuCl(2)(P(3)P(3)(tBu)) (6). The bulky P(2)P(3)(tBu) (1) and P(3)P(3)(tBu) (3) ligands are the most sterically encumbered PP(3)-type ligands so far synthesized, and in all cases, only three phosphorus donors are able to bind to the metal center. Complexes RuCl(2)(PhP(2)P(2)(tBu)) (5) and RuCl(2)(P(3)P(3)(tBu)) (6) were characterized by crystallography. Low temperature solution and solid state (31)P{(1)H} NMR were used to demonstrate that the structure of RuCl(2)(P(2)P(3)(tBu)) (4) is probably analogous to that of RuCl(2)(PhP(2)P(2)(tBu)) (5) which had been structurally characterized.

Rhodium complexes of a chelating ligand with imidazol-2-ylidene and pyridin-2-ylidene donors: the effect of C-metalation of nicotinamide groups on uptake of hydride ion.

Rhodium complexes of the imidazolylidene (C-im) N-heterocyclic carbene (NHC) ligand, C-im-pyH(+), bearing a nicotinamide cation substituent (pyH(+)) have been targeted for ligand-centered uptake and delivery of hydride ion. This work reveals that rhodium(I) complexes such as [Rh(C-im-pyH(+))(COD)X][PF(6)] (1, a: X = Cl, b: X = I) undergo facile C-metalation of the nicotinamide ring to afford rhodium complexes of a novel chelate ligand, C,C'-im-py, with coordinated imidazolylidene (C(im)) and pyridylidene (C(py)) NHC-donors. Seven examples were characterized and include rhodium(III) monomers of the general formula [Rh(C,C'-im-py)L(x)I(2)](z+) (2: z = 1, L = H(2)O or solvent, x = 2; 3, 5, 7: z = 0, L = carboxylate, x = 1) and novel rhodium(II) dimers, the anti/syn-isomers of [Rh(2)(C,C'-im-py)(2)(µOAc)(2)I(2)] (4-anti/syn). The NMR data, backed by DFT calculations, is consistent with attribution of the C,C'-im-py ligand as a bis(carbene) donor. Single crystal X-ray diffraction studies are reported for 2, 3, 4-anti, 4-syn and 7. Consistently, within the each complex, the Rh-C(im) bond length is shorter than the Rh-C(py) bond length, which is the opposite trend to that expected based on simple electronic considerations. It is proposed that intramolecular steric interactions imposed by different rings in the rigid C,C'-im-py chelate ligand dictate the observed Rh-C(NHC) bond lengths. Attempts to add hydride to the C-metalated nicotinamide ring in 3 were unsuccessful. The redox behavior of 3 and 4 and, for comparison, an analogous bis(imidazolylidene)rhodium(III) monomer (8), were characterized by cyclic voltammetry, electron paramagnetic resonance (EPR), and UV-vis spectroelectrochemistry. In 3 and 4, the C-metalated nicotinamide ring is found to exhibit a one-electron reduction process at far lower potential (-2.34 V vs. Fc(+)/Fc in acetonitrile) than the two-electron nicotinamide cation-dihydronicotinamide couple found for the corresponding nonmetalated ring (-1.24 V). The C,C'-ligand is electrochemically silent over a large potential range (from -2.3 V to the anodic solvent limit), thus for both 3 and 4 the first reduction processes are metal-centered. For 4-anti, the cyclic voltammetry and UV-vis spectrochemical results are consistent with a diamagnetic [Rh(I)Rh(II)](2) tetrameric reduction product. Density functional theory (DFT) calculations were used to further probe the uptake of hydride ion by the nicotinamide ring, both before and after C-metalation. It is found that C-metalation significantly decreases the ability of the nicotinamide ring to take up hydride ion, which is attributed to the "carbene-like" character of a C-metalated pyridylidene ring.

Two dibenzodiazepinone molecules with dissimilar dimeric associations and apparent different tautomeric forms.

In two dibenzodiazepinones, viz. the tricyclic core structure, 5H-dibenzo[b,e]diazepin-11(10H)-one, C(13)H(10)N(2)O, and an acylated derivative, 1-(11-hydroxy-5H-dibenzo[b,e]diazepin-5-yl)-2-{4-[3-(1H-imidazol-1-yl)propyl]piperidin-1-yl}ethanone ethanol monosolvate, C(26)H(29)N(5)O(2)·C(2)H(5)OH, dimeric association via hydrogen-bond bridging between the cyclic amide entities is evident, but there are considerable differences between the parent compound and the amidated derivative. Highly consistent with reported structures of related tricyclic lactams, two molecules of the nonsubstituted compound are bridged through two N-H...O hydrogen bonds across a crystallographic centre of symmetry and the bond lengths of the cyclic amide entity correspond to the amino-oxo (lactam) tautomeric form. In contrast, the structure of the derivative shows two similar, but crystallographically unique, molecules hydrogen bonded into a dimeric unit exhibiting an approximate (noncrystallographic) C2 axis. The bond lengths of the two derivative cyclic amide groups support their potential presence in the hydroxyimine (lactim) tautomeric forms, with the resulting possibility of intermolecular tautomerism. Likely driving forces for the two extreme configurations are discussed.

(3R,4S,5S,8S,10R,13R)-3-Hy-droxy-kaura-9(11),16-dien-18-oic acid.

The title compound, C(20)H(28)O(3), was isolated during our investigation into the chemical composition and pharmacological activity of Centipeda cunninghamii (DC.) A. Braun & Asch. (Asteraceae). The enanti-opure compound, a diterpene with a carbon skeleton, is composed of three six- and one five-membered rings in chair, twist-boat, half-chair and envelope conformations, respectively. Each mol-ecule makes one intra- and one inter-molecular O-H⋯O hydrogen bond in the crystal lattice, forming hydrogen-bonded chains along [010]. The absolute configuration of the compound was assigned on the basis of optical rotation measurements.

3,4-Bis-O-propargyl-1,2:5,6-di-O-isopropylidene-D-mannitol: a study of multiple weak hydrogen bonds in the solid state.

The title homochiral compound, C18H26O6, 1, was examined by single-crystal X-ray crystallography in order to understand its potential as a synthetic building block, particularly in inter- and intramolecular cyclocondensation reactions. It has also proven to be an excellent model for understanding multiple weak donor-acceptor D-H...A interactions involving terminal acetylenes as donors and as acceptors. The asymmetric unit of 1 comprises three almost identical independent molecules, each with the mannitol 2R,3R,4R,5R configuration and different conformations. Like independent molecules align in strands through acetylenic donor C-H...O contacts with equivalent dioxolanyl acceptor groups. Two of the strands are aligned unidirectionally, in parallel, while the third strand aligns perpendicular to the first two, to give interwoven layers in the supramolecular structure. A detailed study of the interdigitation of the second propargyl group from each independent molecule between strands, and of other short interstrand C-H...O contacts, provides new insight into the application of weak hydrogen-bond theory within the context of a conformationally flexible symmetrical molecule. Analyses of the Cambridge Structural Database using Crystal Packing Features and ConQuest search motifs support the importance of the D...A distance parameter, demonstrate the different influences of donor and acceptor types, and reveal the interplay between H...A and D...A contributions in different contact types.

Ruthenium hydride complexes of the hindered phosphine ligand tris(3-diisopropylphosphinopropyl)phosphine.

The synthesis and characterization of the novel hindered tripodal phosphine ligand P(CH(2)CH(2)CH(2)P(i)Pr(2))(3) (P(3)P(3)(iPr)) (1) are reported, along with the synthesis and characterization of ruthenium chloro and hydrido complexes of 1. Complexes [RuCl(P(3)P(3)(i)Pr)][BPh(4)] (2[BPh(4)]), RuH(2)(P(3)P(3)(i)Pr) (3), and [Ru(H(2))(H)(P(3)P(3)(iPr))][BPh(4)] (4[BPh(4)]) were characterized by crystallography. Complex 2 is fluxional in solution, and low-temperature NMR spectroscopy of the complex correlates well with two dynamic processes, an exchange between stereoisomers and a faster turnstile-type exchange within one of the stereoisomers.