Nitrile Coordination Research Articles

Exploring Dinuclear Titanium Complexes in Titanium(III) Catalysis

AbstractThe synthesis of one achiral and two chiral propylene‐bridged dititanocenes and their evaluation as catalysts in titanium(III) catalyzed ketone‐nitrile coupling reactions are reported. A reaction progress kinetics analysis of the cross‐coupling between acetophenone and benzyl cyanide reveals that, using a dinuclear titanocene catalyst, the order in catalyst is reduced from two to one in comparison to a mononuclear catalyst. Although the obtained coupling yields and enantioselectivities did not reach the results obtained with the latter, these examples constitute a proof of concept for the templated C─C coupling through coordination of ketone and nitrile to the two tethered titanium centers of a dinuclear catalyst.

Cooperative Nitrile Coordination Using Nickel and a Boron-Containing Secondary Coordination Sphere.

Metal-ligand cooperation has emerged as a versatile tool for substrate activation in chemical reactivity. Herein, we provide the synthesis and characterization of a monoboranyl-containing analogue of the ubiquitous bulky diphosphine ligand, 1,2-bis(di-tert-butylphosphino)ethane, whose reactivity has been examined using nickel. Together, the pairing of nickel and boron provides a platform that allows for the cooperative coordination of organonitriles, giving unusual examples of intermolecularly bound dinickelacycles.

Reactions of nickel boranyl compounds with pnictogen-carbon triple bonds.

The catalytic conversion of unsaturated small molecules such as nitriles into reduced products is of interest for the production of fine chemicals. In this vein, metal-ligand cooperativity has been leveraged to promote such reactivity, often conferring stability to bound substrate - a balancing act that may offer activation at the cost of turnover efficiency. This report describes the reactivity of a [(diphosphine)Ni] compound with pnictogen carbon triple bonds (R-C[triple bond, length as m-dash]E; E = N, P), where the diphosphine contains two pendant borane groups. For E = N, cooperative nitrile coordination is observed to afford {Ni}2 complexes displaying B-N interactions, whereas for E = P, B-P interactions are absent. This work additionally outlines a structure-activity relationship that uses nitrile dihydroboration as a model reaction to unveil the effect of SCS stabilization, employing [(diphosphine)Ni] where the diphosphine contains 0, 1, or 2 pendant Lewis acid groups.

Aluminum Metal–Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis

The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal–organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon–oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.

Construction of dual coordination networks in epoxidized butadiene-acrylonitrile rubber/CuSO4 composites and mechanical behaviors

Dual coordinated cross link networks were designed in epoxidized butadiene-acrylonitrile rubber (NBR)/CuSO4 composites to make commercial NBR become advanced soft materials. First, NBR was modified through organic peroxy acid method to produce epoxidized butadiene-acrylonitrile rubber (ENBR). Next, CuSO4 was introduced in bulk to form strong Cu2+-nitrile coordination bonds acting as strong cross link points and Cu2+-epoxy bonds acting as weak cross link points. XPS analysis, FT-IR spectra and rheological curves proved the dual coordination bonds. Curing rheology curves, crosslinking density and thermal properties effectively demonstrated the formation of related dual cross link networks. The ENBR/CuSO4 composites exhibited excellent mechanical properties due to the synergistic effect of strong and weak metal-ligand coordination networks. During stretching, the weak coordination bonds acted as sacrificial bonds which could dissipate energy, while the strong coordination bonds sustained the network and imparted the elasticity. Under the combined functions of dual coordination bonds, the modulus, tensile strength, and toughness of ENBR/CuSO4 composites could be improved and tuned by controlling the structure parameter of coordination networks such as epoxidation degree and content of CuSO4.

DFT Mechanistic Insight into the Dioxygenase-like Reactivity of a CoIII-peroxo Complex: O-O Bond Cleavage via a [1,3]-Sigmatropic Rearrangement-like Mechanism.

Dioxygen O-O bond activation is a process for oxygenases and oxidases to perform biological functions and synthetic biomimetic catalysts to carry out oxygenation reactions using molecular O2 as an oxidant. Inspired by the experimental development of a CoIII-peroxo complex (i.e., [CoIII(TBDAP)(O2)]+, TBDAP = N,N-ditert-butyl-2,11-diaza[3.3](2,6)-pyridinophane) that exhibits dioxygenase-like reactivity to activate nitriles, a density functional theory (DFT) mechanistic study has been carried out to understand how the peroxo ligand is broken to activate nitriles. The study unveils that the O-O bond cleavage takes place via conversion to a CoII-superoxo complex aided by nitrile coordination, followed by formation of a five-membered intermediate via superoxo O2 radical nucleophilic attack at the nitrile carbon. Finally, a [1,3]-sigmatropic rearrangement-like process breaks the dioxygen bond. The otherwise difficult [1,3]-sigmatropic rearrangement is enabled by the mediation of CoIII(TBDAP) which alters a concerted rearrangement to a sequential process of O-O bond cleavage and N-O bond formation. Expectedly, the unveiling of the O-O bond cleavage mechanism could offer a clue for the development of biomimetic metal oxygenation catalysts.

Nitrile coordination to rhodium does not lead to C-H activation.

Tris(pyrazolyl)borate complexes of rhodium are well known to activate C-H bonds. The reactive [Tp'Rh(PMe3)] fragment [Tp' is tris(3,5-dimethylpyrazol-1-yl)hydroborate] is found to react with valeronitrile to give the κ1N-bound complex (pentanenitrile-κN)(trimethylphosphane-κP)[tris(3,5-dimethylimidazol-1-yl)hydroborato-κ2N2,N2']rhodium(I), [Rh(C15H22BN6)(C5H9N)(C3H9P)]. In contrast to the widespread evidence for the reaction of this fragment with C-H bonds via oxidative addition, no evidence for such a complex is observed.

Organometallic Reactivity of [Silver(I)­(Pyridine‐Containing Ligand)] Complexes Relevant to Catalysis

AbstractSilver(I) complexes of pyiridine‐containing macrocyclic ligands (Pc‐L) have already been demonstrated as active catalysts for some domino and multicomponent reactions. Here, we report new chiral [AgI(Pc‐L*)] cationic complexes that have been synthesized and fully characterized, including structural determination by single‐crystal X‐ray diffraction. The complexes show a rich coordination chemistry, demonstrating both the σ‐philic (alcohol and nitrile coordination) and the π‐philic (alkyne coordination) nature of silver. The η2 coordination mode of the naphthyl pendant arm of the ligands on silver has been observed in solution by NMR spectroscopic experiments. 2D NMR spectroscopy revealed the presence of positive cross peaks resulting from rotational processes and the rate of rotation was measured by using 2D exchange spectroscopy (EXSY).

Synthesis and structure of nitrile-solvated rare earth metallocene cations [Cp2Ln(NCR)3][BPh4] (Cp = C5Me5, C5H4SiMe3; R = Me, tBu, Ph)

The coordination chemistry of MeCN, tBuCN, and PhCN with the cationic rare earth metallocene complexes [(C5Me5)2Ln][(μ-Ph)2BPh2], 1-Ln (Ln=Y, La, Gd), has been examined to determine how nitrile coordination will affect the metallocene geometry. Crystallographic determination of geometry was possible for [(C5Me5)2Ln(NCMe)3][BPh4] (2-Y, 2-Gd), [(C5Me5)2Y(NCtBu)3][BPh4] (3-Y), and [(C5Me5)2Ln(NCPh)3][BPh4] (4-La, 4-Gd). In each case, only three nitriles are found to coordinate and the metallocenes are bent with (C5Me5 ring centroid)–metal–(C5Me5 ring centroid) angles of 137–140°. The THF adduct, [(C5Me5)2La(NCMe)2(THF)][BPh4], 5-La, was also crystallographically characterized. A similar result was observed with the yttrium metallocene of the trimethylsilyl-containing ligand (C5H4SiMe3)1−: coordination of only three nitriles is found in [(C5H4SiMe3)2Y(NCMe)3][BPh4], 6-Y, which has a 136.8° (C5Me5 ring centroid)–Y–(C5Me5 ring centroid) angle.

Role of the Amide Carbonyl Groups in the Nitrile Hydratase Active Site for Nitrile Coordination Using Co(III) Complex with N2S3-type Ligand

Abstract The role of the amide carbonyl oxygens in the nitrile hydratase (NHase) active site for the nitrile coordination to the metal center was studied using a distorted square-pyramidal N2S3-type Co(III) complex at room temperature in the presence of a folded-sheet mesoporous material (FSM) or sodium cation.

Structural studies on tris(2-cyanoethyl)phosphine complexes of Cu(I): The sensitivity of the secondary nitrile coordination to the nature of the anion

Tris(2-cyanoethyl)phosphine (tcep) reacts with the copper(I) compounds, CuX (X=Cl, Br, I and SCN), in a 1:1 ratio to give 1:1 complexes, CuX(tcep), whereas it reacts with CuY (Y=PF6, ClO4, NO3, BH4, CN and CF3COO) in a 2:1 ratio to give the 2:1 complexes, CuY(tcep)2. Single crystal X-ray structures show that for the anions X=Br and SCN, the complexes are coordination polymers, [CuX(tcep)]n, with the Cu centres being bridged by the anion, and as well, one nitrile arm per tcep ligand coordinates intermolecularly to the Cu to give tetrahedral ‘PBr2N’ and ‘PSN2’ coordination spheres respectively. The 2:1 compounds exhibit a variety of structures. For Y=ClO4, CN and CF3COO polymeric structures are formed except for Y=BH4 where the compound is a discrete monomer, [Cu(BH4)(tcep)2], with a chelating anion and two monodentate P-bound tcep ligands. Both the compounds obtained with Y=CN and CF3COO also contain coordinated anions and are formulated as [Cu(CN)(tcep)2]n and [Cu(CF3COO)(tcep)2]n respectively. In the case of Y=CN the anion is bridging and the tcep ligands are only P-bound giving a ‘P2NC’ coordination sphere. In contrast, for Y=CF3COO, the anion is an O-bound monodentate and the tcep ligands bridge to give a ‘P2NO’ environment for the copper. In the case of Y=ClO4, the anion is not coordinated but a polymeric structure, [Cu(tcep)2]n(ClO4)n, is formed via bridging tcep ligands linking Cu centres intermolecularly resulting in a ‘P2N2’ coordination sphere.

Diagnosis of the Redox Levels of TCNQF4 Compounds Using Vibrational Spectroscopy

AbstractThe vibrational spectroscopy of TCNQF40, TCNQF41− and TCNQF42− has been investigated by means of density functional theory. Band assignments in infrared and Raman spectra have been clarified and a series of diagnostics developed for redox level characterisation of TCNQF4 compounds. In the CC stretching region (1460–1600 cm−1), TCNQF40 and TCNQF41− show two bands, with the more energetic being at 1600 cm−1 in TCNQF40 and at approximately 1535 cm−1 in TCNQF41−; in TCNQF42− both modes absorb below 1500 cm−1, often merging to give a single band. In the CF and endocyclic CC stretching region (1290 and 1360 cm−1), TCNQF40 and TCNQF41− show strong bands, whereas TCNQF42− absorbs weakly or not at all. (Additional bands, e.g. from co‐crystallised solvent molecules, may complicate this region.) In the nitrile stretching region (2000–2250 cm−1), modes are highly sensitive to nitrile coordination by metal cations. All three redox levels can produce bands above 2200 cm−1, however bands below 2150 cm−1 are usually due to TCNQF42−. This sensitivity to coordination is likely to affect the spectra of many organic molecular ions.

(3-Methylbenzonitrile-κN)tetrakis(μ-N-phenylacetamidato)-κ4N:O;κ4O:N-dirhodium(II)(Rh—Rh)

In the title compound, [Rh2(C8H8NO)4(C8H7N)], the four acetamidate ligands bridging the dirhodium core are arranged in a 2,2-trans manner. One RhII atom is five-coordinate, in a distorted pyramidal geometry, while the other is six-coord­in­ate, with a disorted octa­hedral geometry. For the six-coord­inate RhII atom, the axial nitrile ligand shows a non-linear Rh–nitrile coordination with an Rh—N—C bond angle of 166.4 (4)° and a nitrile N—C bond length of 1.138 (6) Å. Each unique RhII atom is coordinated by a trans pair of N atoms and a trans pair of O atoms from the four acetamide ligands. The Neq—Rh—Rh—Oeq torsion angles on the acetamide bridge varies between 12.55 (11) and 14.04 (8)°. In the crystal, the 3-methyl­benzo­nitrile ring shows a π–π inter­action with an inversion-related equivalent [inter­planar spacing = 3.360 (6) Å]. A phenyl ring on one of the acetamide ligands also has a face-to-face π–π inter­action with an inversion-related equivalent [inter­planar spacing = 3.416 (5) Å].

Mechanistic Evaluation of the Ni(IPr)2-Catalyzed Cycloaddition of Alkynes and Nitriles to Afford Pyridines: Evidence for the Formation of a Key η1-Ni(IPr)2(RCN) Intermediate.

A detailed mechanistic evaluation of the Ni(IPr)2-catalyzed [2+2+2]-cycloaddition of diynes and nitriles was 2 conducted. Through kinetic analysis of these reactions, observed regioselectivities of the products, and stoichiometric reactions, Ni(IPr)2-catalyzed cycloadditions of diynes and nitriles appear to proceed by a heterooxidative coupling mechanism, contrary to other common cycloaddition catalysts. Reaction profiles demonstrated strong dependence in nitrile, resulting in variable nitrile-dependent resting states. Strong coordination and considerable steric bulk of the carbene ligands facilitate selective initial binding of nitrile thereby forcing a heterocoupling pathway. In situ IR data suggests the initial binding of the nitrile resides in a rare, η1-bound conformation. Following nitrile coordination are a rate-determining hapticity shift of the nitrile and subsequent loss of carbene. Alkyne coordination then leads to heterooxidative coupling, insertion of the pendant alkyne, and reductive elimination to afford pyridine products.

A structural study of seven salt forms of sulfonated azo dyes containing nitrile functional groups

Abstract The crystal structures of seven salt forms of nitrile functionalised monosulfonated azo dyes, as isolated from aqueous solution, are described. The presence of nitrile gives unique structures for the Na salts examined. The normally observed Na–O3S bonding is absent and has been replaced by Na–NC interactions, giving supramolecular structures not previously seen for similar azo colourants. A highly unusual side-on nitrile coordination mode is observed and this bonding is observed both crystallographically and by IR spectroscopy. However, the alkaline earth element salts are all of structural types seen before for other non-nitrile bearing sulfonated azo dyes. Thus the Mg salts are solvent-separated ion-pair species based on the [Mg(OH2)6] ion and the Ca and Sr species are simple complexes of the type [M(L)2(OH2)6], where L is the azo dye anion bonded to the metal centre through a single O atom of the sulfonate group.

Use of metallopeptide based mimics demonstrates that the metalloprotein nitrile hydratase requires two oxidized cysteinates for catalytic activity.

Nitrile hydratases (NHases) are non-heme Fe(III) or non-corrin Co(III) containing metalloenzymes that possess an N(2)S(3) ligand environment with nitrogen donors derived from amidates and sulfur donors derived from cysteinates. A closely related enzyme is thiocyanate hydrolase (SCNase), which possesses a nearly identical active-site coordination environment as CoNHase. These enzymes are redox inactive and perform hydrolytic reactions; SCNase hydrolyzes thiocyanate anions while NHase converts nitriles into amides. Herein an active CoNHase metallopeptide mimic, [Co(III)NHase-m1] (NHase-m1 = AcNH-CCDLP-CGVYD-PA-COOH), that contains Co(III) in a similar N(2)S(3) coordination environment as CoNHase is reported. [Co(III)NHase-m1] was characterized by electrospray ionization-mass spectrometry (ESI-MS), gel-permeation chromatography (GPC), Co K-edge X-ray absorption spectroscopy (Co-S: 2.21 Å; Co-N: 1.93 Å), vibrational, and optical spectroscopies. We find that [Co(III)NHase-m1] will perform the catalytic conversion of acrylonitrile into acrylamide with up to 58 turnovers observed after 18 h at 25 °C (pH 8.0). FTIR data used in concert with calculated vibrational data (mPWPW91/aug-cc-TZVPP) demonstrates that the active form of [Co(III)NHase-m1] has a ligated SO(2) (ν = 1091 cm(-1)) moiety and a ligated protonated SO(H) (ν = 928 cm(-1)) moiety; when only one oxygenated cysteinate ligand (i.e., a mono-SO(2) coordination motif) or the bis-SO(2) coordination motif are found within [Co(III)NHase-m1] no catalytic activity is observed. Calculations of the thermodynamics of ligand exchange (B3LYP/aug-cc-TZVPP) suggest that the reason for this is that the SO(2)/SO(H) equatorial ligand motif promotes both water dissociation from the Co(III)-center and nitrile coordination to the Co(III)-center. In contrast, the under- or overoxidized motifs will either strongly favor a five coordinate Co(III)-center or strongly favor water binding to the Co(III)-center over nitrile binding.

Effects of Divalent Ligand Interactions on Surface-Induced Ordering of Liquid Crystals

We report the synthesis of a mesogen that contains two nitrile groups (4-pentyl-3′,4′-dicyanobiphenyl, DCB), and the use of the mesogen in an investigation of the effects of multivalent ligand interactions on the ordering of liquid-crystalline phases at surfaces decorated with copper (Cu2+) ions. Differential scanning calorimetry (DSC) confirmed that DCB was miscible with nematic phases of 4-pentyl-4′-cyanobiphenyl (5CB). Quantitative measurement of the optical retardance of mixtures of DCB and 5CB in contact with surfaces decorated with Cu2+ (characterized by X-ray photoelectron spectroscopy, XPS) revealed a continuous ordering transition in the nematic LC as a function of increasing concentration of DCB (0.9−2 wt %). In contrast, Fourier transform infrared (FTIR) spectroscopy of 5 mM Cu2+ dissolved in bulk benzonitrile revealed no evidence of a change in nitrile coordination around the Cu2+ upon addition of 5CB or DCB, thus leading to the proposition that the effect of DCB on the ordering of the LC phas...

Adsorbate-Induced Ordering Transitions of Nematic Liquid Crystals on Surfaces Decorated with Aluminum Perchlorate Salts

We report an investigation of interfacial physicochemical phenomena underlying adsorbate-induced ordering transitions in nitrile-containing liquid crystals (LCs) supported on surfaces coated with metal perchlorate salts. When the mass density of Al(ClO4)3 deposited onto a surface was low (0.39 ± 0.03 ng/mm2), we measured 20 μm thick films of nematic 4-cyano-4′-n-pentyl-biphenyl (5CB) to initially exhibit perpendicular (homeotropic) ordering, consistent with the influence of coordination interactions between the nitrile groups of 5CB and Al3+ ions on the surface on the ordering of the LC. Furthermore, exposure of freshly prepared LC films to vapors of an adsorbate that coordinates strongly to Al3+ ions (dimethylmethylphosphonate, DMMP) triggered an ordering transition in the LC films, supporting our conclusion that the initial perpendicular orientation of the LC was induced by nitrile-Al3+ coordination interactions. Subsequent equilibration of the LC on the surface (hours), however, resulted in a slow, time-dependent ordering transition in the absence of DMMP that corresponded to the tilting of the LC away from the surface normal. Measurements of the solubility of Al(ClO4)3 in nematic 5CB (saturation value of 1.7 μmol/mL) supported our hypothesis that the slow ordering transition observed in the absence of DMMP was due to the loss of metal ions from the surface into the LC film (dissolution). In contrast, the solubilization capacity of a 20 μm thick film of 5CB was determined to be insufficient to dissolve 2.14 ± 0.24 ng/mm2 of the salt from a surface, and we measured the homeotropic ordering of nematic films of 5CB on these surfaces to persist for days. Equilibration of these samples, however, was accompanied by a loss of response to DMMP (perpendicular orientation of the LC before and after exposure to DMMP). Control experiments performed with a noncoordinating metal perchlorate salt (sodium perchlorate) confirmed our proposition that the loss of response to DMMP was due to formation of an electrical double layer that promoted perpendicular ordering of the LC and thus masked the effects of changes in coordination interactions induced by DMMP on the ordering of the LC (the electric field of the double layer promotes the perpendicular orientation of the 5CB). Finally, by coating surfaces with Al(ClO4)3 at loadings that were intermediate to those reported above (1.13 ± 0.09 ng/mm2), we observed (i) perpendicular ordering of the LC in the absence of DMMP, and (ii) reversible ordering transitions induced by DMMP during storage of samples over 4−5 days. These results, when combined, indicate that the ordering of the LC on the metal-salt-decorated surfaces is strongly dependent on the loading of metal salt, with key interfacial physicochemical processes being metal ion−nitrile coordination interactions, dissolution of salt into the LC, and formation of electrical double layers. The results of this study provide guidance for the design of LC films that respond to specific chemical analytes and suggest principles for passive chemical sensors.

Density Functional Studies on the Complexation and Spectroscopy of Uranyl Ligated with Acetonitrile and Acetone Derivatives

The coordination of nitrile (acetonitrile, propionitrile, and benzonitrile) and carbonyl (formaldehyde, acetaldehyde, and acetone) ligands to the uranyl dication (UO(2)(2+)) has been examined using density functional theory (DFT) utilizing relativistic effective core potentials (RECPs). Complexes containing up to six ligands have been modeled in the gas phase for all ligands except formaldehyde, for which no minimum could be found. A comparison of relative binding energies indicates that 5-coordinate complexes are predominant, while 6-coordinate complexes involving propionitrile and acetone ligands might be possible. Additionally, the relative binding energy and the weakening of the uranyl bond is related to the size of the ligand, and in general, nitriles bind more strongly to uranyl than carbonyls.

Reactions of (Me 2C)(Me 2Si)[(η 5-C 5H 3)Mo(CO) 3] 2 with nitrile and subsequent cleavage of the C [tbnd]N bond by cooperation of molybdenum and ruthenium

Reaction of the doubly bridged dinuclear molybdenum complex (Me 2C)(Me 2Si)[(η 5-C 5H 3)Mo(CO) 3] 2 ( 1) with benzonitrile in refluxing xylene afforded complexes (Me 2C)(Me 2Si)[(η 5-C 5H 3) 2Mo 2(CO) 4(μ-η 2-η 2(⊥)-N CPh)] ( 2) (50%) and (Me 2C)(Me 2Si)[(η 5-C 5H 3) 2Mo 2(CO) 4(μ-η 1-η 2-N CPh)] ( 3) (6%) with different coordination of nitrile. The corresponding μ-η 2-η 2 acetonitrile and propionitrile complexes 4 and 5 could be obtained from the reactions of (Me 2C)(Me 2Si)(C 5H 4) 2 with (RCN) 3Mo(CO) 3 (R = Me, Et) in refluxing xylene. Reactions of 1 with isonitriles generated μ-η 1-η 2-C NR (R = t Bu, Ph, C 6H 11) bridged complexes 6– 8 in 53–63% yields. Subsequent reaction of 4 with Ru 3(CO) 12 yielded two C N bond cleavaged MoRu clusters (Me 2C)(Me 2Si)(η 5-C 5H 3) 2Mo 2Ru 3(CO) 10(μ-CO)(μ 3-CMe)(μ 4-N) ( 9) (7%) and [(Me 2C)(Me 2Si)(η 5-C 5H 3) 2] 2Mo 4Ru 6(CO) 16(μ-CO)(μ 4-CO) 2(μ 3-η 1-η 2-η 2-N CMe)(μ 3-CMe)(μ 5-N) ( 10) (8%). All the new complexes have been fully characterized. The molecular structures of 2, 4, 6, 9, and 10 have been determined by X-ray diffraction analysis.