Hydridotris(3,5-dimethylpyrazolyl)borate Tungsten Alkyne Complexes for Nonlinear Optics

Deprotonation of the propargyl site of racemic or enantiomerically pure Tp‘(CO)IW(C6H5C⋮CCH3) (Tp‘= hydridotris(3,5-dimethylpyrazolyl)borate) yields an η2-allenyl anion which has been reacted with a series of aldehydes and ketones possessing electron-donating substituents. Elimination under either acidic or basic conditions generates chiral trans conjugated enynes. Characterization has been accomplished by NMR, IR, UV−vis, and elemental analysis. Additionally, X-ray diffraction has been used to structurally characterize racemic Tp‘(CO)IW(C6H5C⋮CCHC(CH3)C5H4FeC5H5). The structural analysis reveals a centrosymmetric space group (P1̄); cell dimensions of a = 10.690(5) Å, b = 13.360(7) Å, c = 15.392(7) Å, α = 92.57(6)°, β = 101.70(5)°, and γ = 100.97(4)°; Z = 2 molecules/unit cell; and Rw = 4.7% and R = 3.9%. Second harmonic generation of the enynes has been measured by the Kurtz powder technique

Hydridotris(3,5-dimethylpyrazolyl)borate Tungsten Alkyne Complexes for Nonlinear Optics

Deprotonation of the propargyl site of racemic or enantiomerically pure Tp‘(CO)IW(C6H5C⋮CCH3) (Tp‘= hydridotris(3,5-dimethylpyrazolyl)borate) yields an η2-allenyl anion which has been reacted with a series of aldehydes and ketones possessing electron-donating substituents. Elimination under either acidic or basic conditions generates chiral trans conjugated enynes. Characterization has been accomplished by NMR, IR, UV−vis, and elemental analysis. Additionally, X-ray diffraction has been used to structurally characterize racemic Tp‘(CO)IW(C6H5C⋮CCHC(CH3)C5H4FeC5H5). The structural analysis reveals a centrosymmetric space group (P1̄); cell dimensions of a = 10.690(5) Å, b = 13.360(7) Å, c = 15.392(7) Å, α = 92.57(6)°, β = 101.70(5)°, and γ = 100.97(4)°; Z = 2 molecules/unit cell; and Rw = 4.7% and R = 3.9%. Second harmonic generation of the enynes has been measured by the Kurtz powder technique

Stepwise Oxidation of Benzylamine Coordinated to the [Tp‘W(CO)(PhC₂Me)]⁺ Moiety

Coordination of benzylamine to the [Tp‘W(CO)(PhC2Me)]+ moiety activates the amine for stepwise oxidation by sequential hydride/proton removal steps. Each metal complex along the stepwise reaction path (amine, amido, imine, azavinylidene, and nitrile) has been isolated and characterized. The structure of the imine complex [Tp‘W(CO)(PhC2Me)(NHCHPh)][BF4] (4) has been confirmed by an X-ray diffraction study. Complex 4 crystallizes in the space group P21/c (Z = 4, a = 13.790(3) Å, b = 13.225(3) Å, c = 19.150(4) Å, β = 108.769(1)°, R = 3.5%, Rw = 4.4%), and key geometric features include a W−N dative bond length of 2.135(6) Å to the imine nitrogen and a W−N−C angle of 129.7(5)°

Stepwise Synthesis of (⋮CCH₂CH₂C⋮), (⋮CCHCHC⋮), and (⋮CC⋮CC⋮) Bridges between Molybdenum or Tungsten Centers

Stepwise Synthesis of (⋮CCH2CH2C⋮), (⋮CCHCHC⋮), and (⋮CC⋮CC⋮) Bridges between Molybdenum or Tungsten Center

Deprotonation and Oxidation of the W⋮CCH₂−W Bridge To Form a C₂-Biscarbyne W⋮C−C⋮W Bridge

Reaction of the anionic vinylidene complex K[Tp‘(CO)2MCCH2] (M = Mo, W; Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with Tp(CO)(PhC⋮CPh)W−I (Tp = hydridotris(pyrazolyl)borate) yields Tp‘(CO)2MCCH2−W(CO)(PhC⋮CPh)Tp (M = Mo, 4; W, 5) and potassium iodide. Removal of a methylene proton from the (⋮CCH2−) bridge with KOBut forms a monoanion containing a putative carbene moiety. Oxidation of the anion with iodine leads to net hydride removal and yields the unusual C2-bridged dimers Tp‘(CO)2M⋮CC⋮W(CO)(PhC⋮CPh)Tp (M = Mo, 7; W, 8). Conversion of the tungsten−carbon single bond in the precursor complex to a triple bond in the product is accompanied by a significant reduction in donation to the metal from the alkyne π⊥ orbital

Reaction of a Tungsten(II) Methylene Complex with Excess Base To Form a C₃H₅-Bridged Dimer

Reaction of [Tp‘(CO)(PhC2Me)WCH2][PF6] (1) with excess base (NaOH/H2O or KH) in methylene chloride yields the C3H5-bridged dimer [Tp‘(CO)(PhC2Me)WCH2C(H)CH2W(PhC2Me)(CO)Tp‘][PF6] (2). Dimer 2 is reproducibly formed in yields of 10−15%; it is inert toward a variety of nucleophiles. Structural and spectroscopic features of 2 form the basis for a discussion of the bonding in this unusual complex. Bonding extremes for the hydrocarbon bridge include an allylic C3H5 fragment bound to the two tungsten centers through opposite faces of the allyl ligand, a linkage which is σ-bonded at each metal with a carbocationic central carbon, and a σ,π-bridging system. Metric parameters in the solid state and 1H, 13C NMR and infrared spectroscopies suggest that the dominant resonance contribution derives from the allylic formalism. A surrogate solvent (1,2-dichloroethane) results in no observable change in the reaction, and thus, the methide source needed to link the two monomeric fragments is believed to originate from the carbene complex

<i>p</i>-Anisaldehyde as a Ligand in Molybdenum and Tungsten Complexes: σ or π?

The different binding modes of p-anisaldehyde to the [TpMo(CO)(MeC⋮CMe)]+ and [TpW(CO)(MeC⋮CMe)]+ fragments in solution have been assessed by IR and 1H and 13C NMR spectra. X-ray analyses substantiate that p-anisaldehyde is σ-bound in the molybdenum complex 1 and π-bound in the tungsten complex 2

Stepwise Oxidation of Benzylamine Coordinated to the [Tp‘W(CO)(PhC₂Me)]⁺ Moiety

Coordination of benzylamine to the [Tp‘W(CO)(PhC2Me)]+ moiety activates the amine for stepwise oxidation by sequential hydride/proton removal steps. Each metal complex along the stepwise reaction path (amine, amido, imine, azavinylidene, and nitrile) has been isolated and characterized. The structure of the imine complex [Tp‘W(CO)(PhC2Me)(NHCHPh)][BF4] (4) has been confirmed by an X-ray diffraction study. Complex 4 crystallizes in the space group P21/c (Z = 4, a = 13.790(3) Å, b = 13.225(3) Å, c = 19.150(4) Å, β = 108.769(1)°, R = 3.5%, Rw = 4.4%), and key geometric features include a W−N dative bond length of 2.135(6) Å to the imine nitrogen and a W−N−C angle of 129.7(5)°

Synthesis and Deprotonation/Alkylation Reactions of the Chiral Carbene Complex Tp‘(CO)(NO)MoC(OMe)(Me)

The Fischer carbene complex Tp‘(CO)(NO)MoC(OMe)(Me) (1) has been synthesized, and functionalization of the carbene methyl substituent has been achieved via deprotonation/alkylation reaction sequences. The chiral metal center produced moderate diastereoselectivity. Isomeric, geometric, and thermodynamic features are discussed for the complexes Tp‘(CO)(NO)MC(OMe)(R) (M = W, R = Me; M = Mo, R = Me, Et, Ph, −CH2CH2CHCH2, −C(H)(Me)CH2CHCH2), and evidence of a substantial metal carbene rotational barrier is presented. Important structural features for Tp‘(CO)(NO)MoC(OMe)(Ph) (7), which was characterized by single-crystal X-ray crystallography, include a short molybdenum−carbon bond distance to the carbene (2.085(4) Å) and a carbene carbon−oxygen bond distance of 1.356(5) Å

<i>N</i>-Porphyrinylamino and -amido Compounds by Addition of an Amino or Amido Nitrogen to a Porphyrin Meso Position

This report describes the synthesis and characterization of a series of octaethylporphyrin derivatives in which the porphyrin π-network is connected to phenyl, 3-fluoranthenyl, or 1-pyrenyl aromatic systems through a meso amino or amido nitrogen. Metal-free bases and zinc(II) and iron(III) complexes have been obtained. These compounds represent the first examples of linkages between porphyrins and extended π-networks through a nitrogen atom directly attached to a porphyrin meso position. 1H NMR studies of the metal-free bases and zinc complexes showed that in the amido-linked adducts, the plane containing the aryl substituent was oriented perpendicular to the plane of the porphyrin. Linkage through the secondary amino nitrogen, however, allowed the aryl plane to rotate toward coplanarity with the porphyrin plane, resulting in conjugation of the highest occupied aryl and porphyrin molecular orbitals through the nitrogen lone pair. In developing routes to the amino-linked compounds, the facile formation of fused azaaryl chlorins via an oxidative intramolecular cycloaddition was observed. An aryl carbon ortho to the meso linkage attacked the β-carbon of an adjacent pyrrole ring, accompanied by 1,2-migration of a pyrrole β-ethyl substituent and a two-electron oxidation of the initially formed macrocycle. The resulting structures are analogous to benzochlorins. The electronic spectra of the metal-free bases are characterized by intense, long-wavelength bands in the visible region. Molecular structures of the chloroferric complexes of the azabenzofluorantheno- and azabenzpyrenoporphyrin macrocycles (derived from fusion of the fluoranthenyl and pyrenyl substituents, respectively) were obtained by X-ray diffraction. The porphyrin moiety in the azabenzofluoranthenoporphyrin adopted a gable structure, with a 22° fold along a diagonal including the pyrrole-ring C4 and C16 α-carbons. By contrast, the azabenzpyrenoporphyrin was virtually planar