Synthesis, characterization, and reactivity of alkoxo complexes containing Cp*M(NO) groups (M = molybdenum, tungsten)

Legzdins, Peter; Lundmark, Penelope J.; Rettig, Steven J.

doi:10.1021/om00033a029

Cited by 12 publications

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“…Thermolysis of the red tungsten vinyl complex 1 at 45 °C in the presence of esters such as methyl or ethyl acetate affords the oxametallacyclopentadienyl complexes Cp*W(NO)(OMe)(η 2 - O C(Me)CH C Ph) ( 2 ) and Cp*W(NO)(OEt)(η 2 - O C(Me)CH C Ph) ( 3 ), respectively, in high yield and purity (eq 1). These four-legged, piano-stool complexes are burgundy crystalline solids that are air-stable at ambient temperatures for periods up to 1 week. The Nujol-mull IR bands attributable to the NO stretch in 2 and 3 are located at 1532 and 1538 cm -1 , typical of 18e alkoxide-containing complexes . The 1 H and 13 C NMR signals displayed by complexes 2 and 3 are readily assigned.…”

Section: Resultsmentioning

confidence: 88%

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Legzdins

Lumb

1998

Organometallics

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Thermolysis of the alkyl vinyl complex Cp*W(NO)(CH2SiMe3)(CPhCH2) (1) in the presence of unsaturated, heteroatom-containing compounds such as esters and nitriles quantitatively affords metallacyclic products of reductive coupling. These are trapped as 18e complexes via either intramolecular rearrangement or intermolecular reaction with added trapping reagents. The nature of these metallacycles is consistent with the intermediacy of the acetylene complex Cp*W(NO)(η2-CPh⋮CH) (A) derived in situ from the reductive elimination of SiMe4 from 1. With esters ROAc (R = Me, Et), reductive coupling and C−O bond cleavage yields the alkoxide-containing oxametallacyclopentadiene complexes Cp*W(NO)(η2-OC(Me)CHCPh)(OR) (2, R = Me; 3, R = Et). Thermolysis of 1 in RCN (R = Me, Et, iPr) containing small excess amounts of R‘OH yields the respective hydroxide or alkoxide compounds Cp*W(NO)(η2-NHC(R)CHCPh)(OR‘) (4, R = Me, R‘ = H; 5, R = Et, R‘ = H; 6, R = iPr, R‘ = H; 7, R = Me, R‘ = C3H5). Utilization of cyclopentadiene (CpH) as the trapping agent in MeCN affords the aminopentafulvene complex Cp*W(NO)(HNC(C(C4H4))(Me))(η2- NHC(Me)CHCPh) (8). VT 1H NMR spectroscopy reveals the fluxional solution behavior of the fulvene ligand in 8. Thermolysis of 1 in RCN (R = Me, iPr) containing trace amounts of acetone gives the bicyclic species Cp*W(NO)(η3-OC(Me)2 NC(Me)CHCPh) (9, R = Me; 10, R = iPr). In the absence of added trapping reagent, thermolysis of 1 in RCN (R = Me, Et) yields the vinyl amidinate complexes Cp*W(NO)(η3-NHC(R)NC(C(R1)(R2))CHCPh) (11, R = Me, R1 = R2 = H; 12, R = Et, R1 = H, R2 = Me). The molecular structures proposed for 2, 4, 8, and 10 are confirmed by single-crystal X-ray analyses. Mechanistic proposals to account for the observed chemistry are corroborated by the results of labeling studies, while a kinetic study of the transformations yielding 3, 4, and 11 implicates the rate-limiting generation of acetylene intermediate A. A qualitative orbital overlap rationale is proposed to account for the observed chemistry.

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Section: Resultsmentioning

confidence: 88%

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Legzdins

Lumb

1998

Organometallics

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“…In recent years we have been particularly interested in the properties of Cp‘M(NO)-containing complexes [Cp‘ = Cp (η 5 -C 5 H 5 ) or Cp* (η 5 -C 5 Me 5 ); M = Cr, Mo, or W], and to date we have investigated the characteristic reactivity of M−C, M−N, and M−O bonds in these compounds. A logical extension of this earlier work is to encompass the related complexes containing M−P linkages.…”

Section: Introductionmentioning

confidence: 99%

Different Modes of Reaction of Lithium Phosphides with Cp*M(NO)(X)Cl Complexes of Molybdenum and Tungsten

et al. 1997

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Treatment of Cp*M(NO)(X)Cl complexes (M = Mo, W; X, = CH2SiMe3, CH2CMe3, NHCMe3, OCMe3, Cl) with lithium phosphides can result in one of three different types of reactions. Some reactions involve the starting material undergoing metathesis of a chloro ligand, and others effect reduction of the organometallic reactant, while a third class results in a scrambling of the ligands of the starting complex. Reactions of Cp*M(NO)(X)Cl with LiPPh2 lead to formation of the respective phosphido-containing complexes Cp*M(NO)(X)(PPh2) [M = W, X = CH2SiMe3 (1), CH2CMe3 (2), NHCMe3 (3), OCMe3 (4); M = Mo, X = NHCMe3 (5)]. In contrast, treatment of the molybdenum complexes Cp*Mo(NO)(X)Cl (X = CH2SiMe3, CH2CMe3, OCMe3) with LiPPh2 under identical conditions affords no isolable products. When metathesis of the chloro ligands in the Cp*M(NO)Cl2 complexes of Mo and W is attempted with either LiPPh2 or LiPPhH, the only isolable products formed are those resulting from the reduction of the organometallic reactant. Thus, treatment of Cp*W(NO)Cl2 with 1 equiv of LiPPh2 leads to isolation of the NO bond-cleaved product, [Cp*W(NO)(Cl)](μ-N)[Cp*W(O)Cl] (6), in low (15%) yield, while reactions of Cp*M(NO)Cl2 (M = Mo, W) with 2 equiv of either LiPPh2 or LiPPhH afford modest yields of the bimetallic products [Cp*W(NO)(μ-PPh2)]2 (7), [Cp*Mo(NO)(μ-PPh2)]2 (8), and [Cp*Mo(NO)(μ-PHPh)]2 (9). Finally, the reaction of Cp*W(NO)(NHCMe3)Cl with LiPPhH induces a ligand-scrambling process in which an amide ligand from one molecule of the starting material is transferred to the tungsten center of another to produce Cp*W(NO)(NHCMe3)2 (10). A similar example of ligand scrambling occurs during the reaction of Cp*Mo(NO)(CH2SiMe3)Cl with LiPPhH. In this case the unexpected product {[Cp*Mo(NO)(CH2SiMe3)2][Li(THF)]}2 (11, isolated in 3% yield) has also undergone a further one-electron reduction at the metal center. The solid-state molecular structures of compounds 9−11 have been established by X-ray crystallographic analyses.

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“…Synthesis of Alkoxo Alkyl Complexes. We have previously reported that alkoxo alkyl complexes, Cp*M(NO)(R)(OR‘) (M = Mo, W; R, R‘ = hydrocarbyl), are preparable via alkoxide-for-chloride metathesis reactions . As summarized in eq 1, the desired complexes result from treatment of the appropriate alkyl chloro precursor with an alkali-metal alkoxide.…”

Section: Resultsmentioning

confidence: 99%

“…The pale yellow reaction mixture became red as it was stirred at ambient temperatures for 2 d. The final reaction mixture was taken to dryness in vacuo, the remaining red-brown oil was redissolved in pentane (15 mL), and the pentane solution was filtered through Celite (2 × 5 cm) supported on a sintered glass frit. Solvent was removed from the filtrate in vacuo to obtain a red oil which was identified as Cp*W(NO)(CH 2 SiMe 3 )(OCMe 3 ) by comparison of its spectroscopic properties with those exhibited by an authentic sample …”

Section: Methodsmentioning

confidence: 99%

Chloride Metathesis or Nitrosyl N−O Bond Cleavage in Cp*W(NO)(CH₂SiMe₃)Cl upon Treatment with Alkali-Metal Alkoxides

1996

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The bimetallic compound [Cp*W(NO)(CH2SiMe3)](μ2-η1:η2-NC{H}SiMe3)[Cp*W(Cl)(O)] (1), is produced in low yield by the heterogeneous reaction between Cp*W(NO)(CH2SiMe3)Cl and KOCMe3 in pentane. However, when this reaction is performed in THF or Et2O, the expected metathesis product, Cp*W(NO)(CH2SiMe3)(OCMe3), is obtained. When Cp*W(NO)(CH2SiMe3)Cl is treated with KOMe in pentane, a different bimetallic compound, [Cp*W(NO)(CH2SiMe3)Cl](μ-N)[Cp*W(Cl)(η2-N{O}{H}CH2SiMe3)] (2), is produced along with the known dioxo alkyl complex Cp*W(O)2(CH2SiMe3). Again, the expected alkyl alkoxide product, Cp*W(NO)(CH2SiMe3)(OMe), is produced when the reaction is effected in THF or Et2O. The roles of KOCMe3 or KOMe during the formation of complexes 1 and 2 are presently unclear. However, when the reactions are performed using the Li or Na alkoxide salts, the expected metathesis products, namely the alkyl alkoxide complexes, are indeed produced. The solid-state molecular structures of bimetallic complexes 1 and 2 have been established by single-crystal X-ray crystallographic analyses.

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Synthesis, characterization, and reactivity of alkoxo complexes containing Cp*M(NO) groups (M = molybdenum, tungsten)

Cited by 12 publications

References 0 publications

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Different Modes of Reaction of Lithium Phosphides with Cp*M(NO)(X)Cl Complexes of Molybdenum and Tungsten

Chloride Metathesis or Nitrosyl N−O Bond Cleavage in Cp*W(NO)(CH₂SiMe₃)Cl upon Treatment with Alkali-Metal Alkoxides

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Synthesis, characterization, and reactivity of alkoxo complexes containing Cp*M(NO) groups (M = molybdenum, tungsten)

Cited by 12 publications

References 0 publications

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Ligand Elaboration Mediated by a Cp*W(NO) Template: Stepwise Incorporation of Small Molecules into a Tungsten Vinyl Fragment

Different Modes of Reaction of Lithium Phosphides with Cp*M(NO)(X)Cl Complexes of Molybdenum and Tungsten

Chloride Metathesis or Nitrosyl N−O Bond Cleavage in Cp*W(NO)(CH2SiMe3)Cl upon Treatment with Alkali-Metal Alkoxides

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Chloride Metathesis or Nitrosyl N−O Bond Cleavage in Cp*W(NO)(CH₂SiMe₃)Cl upon Treatment with Alkali-Metal Alkoxides