Substitution reactions of a .mu.-thioether ligand in dinuclear cyclopentadienylmolybdenum complexes

Tucker, David S.; Dietz, Steven; Parker, Keith G.; Carperos, Vasili; Gabay, J.; Noll, B.; DuBois, M. Rakowski; Campana, Charles F.

doi:10.1021/om00009a041

Cited by 21 publications

(11 citation statements)

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“…The Mo−CO distance (2.053(6) Å) is comparable with known diamagnetic Mo(III) dimers containing CO ligands, i.e. [CpMo(CO) 2 (μ-S- t -Bu)] 2 (BF 4 ) (average 2.016(16) Å), [Cp 2 Mo 2 (CO) 3 (MeCN)(μ-SPh) 2 ](BF 4 ) 2 (average 2.01(4) Å), and [(CpMoCO) 2 (μ-SMe)(S 2 CH 2 )]OTf (average 2.068(12) Å) . The Mo−Cl distance (2.473(2) Å) compares well with those in other half-sandwich Mo(III) complexes, e.g.…”

Section: Resultssupporting

confidence: 61%

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Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions

1996

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The first examples of stable, mononuclear 17-electron carbonyl complexes of Mo(III) have been synthesized, isolated, and characterized by IR and EPR spectroscopy. Oxidation of Cp*MoCl(CO)(PMe3)2 (1; E 1/2 = −0.48 V vs Fc/Fc+), Cp*MoCl(CO)(dppe) (2; E 1/2 = −0.44 V), and CpMoCl(CO)(dppe) (3; E 1/2 = −0.25 V) with Fc+PF6 - yields [1]PF6, [2]PF6, and [3]PF6, respectively. The IR stretching vibration of the 17-electron oxidation products are 136−153 cm-1 blue-shifted with respect to the corresponding stretching vibrations of the parent Mo(II) compounds. The room temperature EPR spectra show observable coupling to the Mo and P nuclei and indicate a trans geometry for 1 + and a cis geometry for 2 + and 3 +. The four-legged piano stool geometry of 2 + with the phosphines atoms in relative cis positions has been confirmed by a single-crystal X-ray analysis. The X-ray data for [2]PF6·THF are the following: monoclinic, P21/n, a = 13.7394(14) Å, b = 20.421(2) Å, c = 14.857(2) Å, β = 99.119(8)°, V = 4115.8(8) Å3, Z = 4, D x = 1.469 g·cm-3, λ(Mo Kα) = 0.71073 Å, μ (Mo Kα) = 0.562 mm-1, R(F) = 4.59%, R(wF 2) = 10.77% for 4299 data with F o > 4σ(F o). The thermal stability of the cations decreases with increasing carbonyl stretching frequencies in the order 1 + > 2 + ≫ 3 +. The decarbonylated product of thermolysis of 3 +, [CpMoClF(dppe)(MeCN)]+PF6 -, [4]PF6, which is believed to arise via a 15-electron [CpMoCl(dppe)]+ intermediate, has been isolated and characterized by 1H, 31P, and 19F NMR spectroscopies as well as a single-crystal X-ray analysis. The structure of 4 + shows a distorted pseudooctahedral geometry with the Cp ring and the F atom occupying the two axial coordination sites and the two phosphine atoms of the dppe occupying two cis equatorial sites. The data for [4]PF6·MeCN are as follows: monoclinic, P21/n, a = 13.160(2) Å, b = 10.942(2) Å, c = 25.010(3) Å, β = 95.225(10)°, V = 3586.4(9) Å3, Z = 4, D x = 1.557 g·cm-3, μ(Mo Kα) = 0.71073 Å, R(F) = 4.11%, R(wF 2) = 11.81% for 5964 data with F o > 4σ(F o). The nucleophilic addition of Cl- to 1 + , 2 + , or 3 + is followed by redox processes to afford mixtures of the parent Mo(II) carbonyl complexes 1−3 and Mo(IV) or Mo(V) products, depending on the nature of the ligands. The mechanism of these reactions has been elucidated through parallel chemical and electrochemical studies.

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Section: Resultssupporting

confidence: 61%

“…Stable CO derivatives of Mo(III) were previously limited to dinuclear, metal−metal bonded, diamagnetic compounds, e.g. [Cp 2 Mo 2 (μ-SR) 2 (CO) 3 L] 2+ (R = Me, Ph; L = CO, MeCN, t -BuCN), − [Cp 2 Mo 2 (μ-SMe) 3 (CO) 2 ] + , and [Cp 2 Mo 2 (μ-SMe)(μ-S 2 CH 2 )(CO) 2 ] + …”

Section: Introductionmentioning

confidence: 99%

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions

1996

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“…Molybdenum(IV) centers are known to bind both CO and Bu t NC [72,73,74,75]. Isocyanides also bind to the iron centers of Fe-S cubanes and similar clusters [76,77].…”

Section: Discussionmentioning

confidence: 99%

“…If this sul®do-based chemistry can be shown to occur with FeMoco(sr), then the possible implications with respect to the mechanism of nitrogen ®xation are clear. It is relevant here to note that binding of isocyanides at sulfur does not occur in analogous Cp-capped Mo(IV) complexes in which the bridging ligands are thiolate rather than sul®de [73,74,75].…”

Section: Discussionmentioning

confidence: 99%

Determination of ligand binding constants for the iron-molybdenum cofactor of nitrogenase: monomers, multimers, and cooperative behavior

Frank

Angove

Burgess

2001

J. Biol. Inorg. Chem.

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Equilibrium titrations in N-methylformamide (NMF) of G-25 gel filtered (ox)-state FeMo cofactor [FeMoco(ox)] from Azotobacter vinelandii nitrogenase were carried out using sodium ethanethiolate and followed using UV/Vis absorption spectroscopy. For Fe-Moco(ox), a non-linear least squares (NLLSQ) fit to the data indicated a strong equilibrium thiolate-binding step with Keq = 1.3+/-0.2x10(6) M(-1). With 245 molar excess imidazole, cooperative binding of three ethanethiolates was observed. The best NLLSQ fit gave Keq=2.0+/-0.1x10(5) M(-2) and a Hill coefficient n=2.0+/-0.3. A Scatchard plot of these data was concave upward, indicating positive cooperativity. The fit to previously published data involving benzenethiol titration of the one-electron reduced (semi-reduced) cofactor, FeMoco(sr), as followed by EPR required a model that included both a sub-stoichiometric ratio of thiol to FeMoco(sr) and about five cooperative ligand binding sites. These constraints were met by modeling FeMoco(sr) as an aggregate, with fewer thiol binding sites than FeMoco(sr) units. The best fit model was that of FeMoco(sr) as a dodecamer with five cooperative benzenethiol binding sites, yielding a thiol binding constant of 3.32+/-0.09x10(4) M(-4.8) and a Hill coefficient n=4.8+/-0.6. The results of all the other published ligand titrations of FeMoco(sr) were similarly analyzed successfully in terms of equilibrium models that include both cooperative ligand binding and dimer-level aggregation. A possible structural model for FeMoco aggregation in NMF solution is proposed.

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“…We found this to be the case for the Μο(ΠΙ) complex 10, which shows reactivity of the C-S bonds of the THT bridge, but in addition it undergoes ligand substitution. Finally in this section we refer to the elegant studies of the Rakowski DuBois group, who have observed some remarkable examples of both C-S bond-making and bond-breaking in [(CpMo) 2 (S 2 CH 2 )^-SMe 2 )^-SMe)] + and related systems (29). In addition, and uniquely different from our systems, is the lability of the bridging thioether, and its easy replacement by other ligands.…”

Section: 518mentioning

confidence: 76%

C—S Bond-Breaking and Bond-Making Reactions in Molybdenum and Tungsten Complexes

Boorman

Gao

Kraatz

et al. 1996

ACS Symposium Series

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Selected C-S bond-breaking and bond-making reactions from our work are discussed that have implications to the modeling of both industrial and biological processes. The complexes WCl5(SR) were found to be subject to elimination of RCl, with concomitant formation of WCl4S via a carbonium ion mechanism. Attempts to emulate the C-S bond cleavage step of hydrodesulfurization by introduction of hydride into the coordination sphere, or by reaction with a second transition metal hydride, resulted in the synthesis of a variety of homonuclear and heteronuclear complexes, with elimination of the appropriate alkane. The synthesis of complexes of the type Cl 3 W(µ-R 2 S) 3 WCl 3 led to the discovery of the reactivity of the C-S bonds toward nucleophiles, including hydride. A computational study provides an explanation for this lability. Reactions of the [MoS4]2-and [WS4]2-ions with organic halides, have been reinvestigated.[PPh4][WS 3 (SR)] (R = Et, i Pr, t Bu) and [PPh4][MoS3(S t Bu)] have been characterized crystallographically. These complexes undergo reductive elimination reactions forming polynuclear sulfidometalates such as W3S92-. The synthetic potential and possible biological significance of these reactions is discussed.The rich chemistry of molybdenum and tungsten with sulfide and organosulfur ligands has been recognized for more than two decades. It is punctuated by complicated redox behavior of both metal and ligands, and also by unexpected reactions of the coordinated ligands. In this regard the metal-assisted cleavage of C-S bonds has been of particular interest, since this process is believed to be involved in the catalytic hydrodesulfurization of fossil fuels. The reverse process, namely the formation of C-S bonds has attracted less attention, but it is interesting to speculate as to the possible importance of this process in the biosynthesis of metalloenzymes.

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Substitution reactions of a .mu.-thioether ligand in dinuclear cyclopentadienylmolybdenum complexes

Cited by 21 publications

References 0 publications

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions

Determination of ligand binding constants for the iron-molybdenum cofactor of nitrogenase: monomers, multimers, and cooperative behavior

C—S Bond-Breaking and Bond-Making Reactions in Molybdenum and Tungsten Complexes

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Substitution reactions of a .mu.-thioether ligand in dinuclear cyclopentadienylmolybdenum complexes

Cited by 21 publications

References 0 publications

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl-Addition Reactions

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl-Addition Reactions

Determination of ligand binding constants for the iron-molybdenum cofactor of nitrogenase: monomers, multimers, and cooperative behavior

C—S Bond-Breaking and Bond-Making Reactions in Molybdenum and Tungsten Complexes

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Product

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Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions

Stable Mononuclear, 17-Electron Molybdenum(III) Carbonyl Complexes. Synthesis, Structure, Thermal Decomposition, and Cl^-Addition Reactions