Coordinatively and Electronically Unsaturated Tungsten(0) Carbonyl Complexes Stabilized by π-Donating Amido Ligands

Darensbourg, Donald J.; Klausmeyer, Kevin K.; Reibenspies, Joseph H.

doi:10.1021/ic950985z

Cited by 43 publications

(36 citation statements)

References 15 publications

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“…Hence, the typical (semi)-benzoquinonediimine-type electron distribution of these NIL systems appears to be hindered in [(btmgb)NiCl 2 ], which is in line with rather long C benzyl À N bond lengths (C1 À N1 = 1.4118 (7) and C6 À N4 = 1.4072 (7) ). These distances are close to the ones of the innocent ligand reference system (Et 4 N) 2 [23] which range from 1.372(6) to 1.418 (6) . Furthermore, the six CÀN bonds attached to the central guanidine carbon atoms display rather equal distances (C7ÀN: 1.3245 (7) [20] This dislocation of the metal atom in [(btmgb)NiCl 2 ] is a consequence of the envelope-type ring puckering of the five-membered metallacycle (Ni,N1,C1,C6,N4), which displays a pronounced interplanar angle of 18.26(3)8 between the N1,C1,C6,N4 and N1,Ni,N4 entities.…”

Section: Resultssupporting

confidence: 64%

On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

Roquette

Maronna

Peters

et al. 2010

Chemistry A European J

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In this work we report on the syntheses and properties of several new Ni complexes featuring the chelating bisguanidines bis(tetramethylguanidino)benzene (btmgb), bis(tetramethylguanidino)naphthalene (btmgn), and bis(tetramethylguanidino)biphenyl (btmgbp) as ligands. All complexes were structurally characterized by single-crystal X-ray diffraction and quantum chemical calculations. A detailed inspection of the magnetic susceptibility of [(btmgb)NiX(2)] and [(btmgbp)NiX(2)] (X=Cl, Br) revealed a linear temperature dependence of chi(-1)(T) above 50 K, which was in agreement with a Curie-Weiss-type behavior and a triplet ground state. Below approximately 25 K, however, magnetic susceptibility studies of the paramagnetic d(8) Ni complexes revealed the presence of a significant zero-field splitting (ZFS) that results from spin-orbit mixing of excited states into the triplet ground state. The electronic consequences that might arise from the mixing of states as well as from a possible non-innocent behavior of the ligand have been explored by an experimental charge density study of [(btmgb)NiCl(2)] at low temperatures (7 K). Here, the presence of ZFS was identified as one potential reason for the flat angle-spherical Cl-Ni-Cl deformation potential and the distinct differences between the angle-spherical X-Ni-X valence angles observed by experiment and predicted by DFT. An analysis of the topology of the experimentally and theoretically derived electron-density distributions of [(btmgb)NiCl(2)] confirmed the strong donor character of the bisguanidine ligand but clearly ruled out any significant non-innocent ligand (NIL) behavior. Hence, [(btmgb)NiCl(2)] provides an experimental reference system to study the mixing of certain excited states into the ground state unbiased from any competing NIL behavior.

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Section: Resultssupporting

confidence: 64%

On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

Roquette

Maronna

Peters

et al. 2010

Chemistry A European J

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“…Thus, [Fe II A C H T U N G T R E N N U N G (pda 2À ) 2 ] 2À in 2 and 3 LT is the first such example and its geometric details may serve as a reference point for the fully reduced ligand form of the o-phenylenediamide ligand. [13] Surprisingly, the geometry of [Fe II -A C H T U N G T R E N N U N G (pda 2À ) 2 ] 2À in 2 and 3 LT is similar, but not identical. The di-A C H T U N G T R E N N U N G anion in 2 has a 128 less twisted geometry compared to 3 LT , which we ascribed to differing packing forces in the unit cell.…”

Section: Between [Fe IImentioning

confidence: 97%

Characterization of Three Members of the Electron‐Transfer Series [Fe(pda)₂]ⁿ (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non‐innocent Derivatives of N,N′‐Bis(pentafluorophenyl)‐o‐phenylenediamide(2−, 1^.−, 0)]

Khusniyarov

Bill

Weyhermüller

et al. 2008

Chemistry A European J

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The four-coordinate iron complexes, [Fe(III)(pda(2-))(pda(.-))] (1) and [AsPh(4)](2)[Fe(II)(pda(2-))(2)] (2) were synthesized and fully characterized; pda(2-) is the closed-shell ligand N,N'-bis(pentafluorophenyl)-o-phenylenediamido(2-), and pda(.-) represents its one-electron-oxidized pi-radical anion. Single-crystal X-ray diffraction studies of 1 and 2 performed at 100(2) K reveal a distorted tetrahedral coordination environment at the iron centers, as a result of the intramolecular pi-pi interactions between C(6)F(5) rings. The electronic structures of 1 and 2 were unambiguously determined by a combination of (57)Fe Mössbauer and electronic spectroscopy, magnetic susceptibility measurements, X-ray crystallography, and DFT calculations. Compound 1 contains an intermediate-spin Fe(III) ion (S(Fe)=3/2) strongly antiferromagnetically coupled to a pi-ligand radical (S(R)=1/2) yielding an S(t)=1 ground state. Complex 2 possesses a high-spin Fe(II) center (S(Fe)=2) with two closed-shell dianionic ligands. Complexes 1 and 2 are members of the redox series [Fe(pda)(2)](n) with n=0 for 1 and n=2- for 2. The anion n=1- has been reported previously in the coordination salt [Fe(dad)(3)][Fe(pda)(2)] (3; dad=N,N'-bis(phenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene). A complicated temperature-dependent electronic structure has been observed for this salt. Here, DFT calculations performed on 3 confirm the previous assignments of spin- and oxidation-states. Thus, [Fe(pda)(2)](n) (n=0, 1-, 2-) constitutes an electron-transfer series, which has also been established by cyclic voltammetry; the mono- and dications (n=1+ and 2+) are also accessible in solution, but have not been further investigated. The (57)Fe Mössbauer spectra of [Fe(pda)(2)](n) species in 1 and 3 show extremely large quadrupole splitting constants due to addition of the valence and covalence contributions that have been confirmed by DFT calculations.

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“…Polyacrylamide ͑PAM͒ was employed as an inhibitor because the surface of oxidized W films is coordinately bonded with the amine group. 10,11 Consequently the adsorption of PAM on the W film could impede the corning of the seam on the W plug.…”

mentioning

confidence: 99%

Constraints of the Corning on Plugs of W Film in W Chemical Mechanical Planarization

Kim

Hong

Kim

et al. 2009

Electrochem. Solid-State Lett.

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The constraints of corning on the W plug in W chemical mechanical planarization ͑CMP͒ were investigated by controlling the corrosion behavior and static etch rate of the W film. Poly͑acrylic amide͒ ͑PAM͒ was used as an inhibitor to decrease the static etch rate of the W film. The interaction between PAM and the surface of the W film was determined by potentiostatic measurement using a potentiometer and by force measurement using an atomic force microscope ͑AFM͒. AFM results revealed that the adlayer of PAM formed on the W film, which prevented the oxidation of the W film. Consequently the addition of PAM suppressed the corning defect on the W plug in a W CMP test that used patterned wafers.According to memory device integration, pattern structures are becoming more and more complicated, and more than 10 layers of different metals, polymers, barriers, and oxides are stacked above the silicon. 1 Tungsten ͑W͒ is commonly used in contemporary memory devices as a wiring material for contact/via fill applications. 2 W is commonly deposited by chemical vapor deposition ͑CVD͒, 3 after which W plugs in metal interconnection are formed through chemical mechanical planarization ͑CMP͒. 4,5 In the W CMP process, W deposited by CVD should be polished to improve the lithography in multilevel device fabrication and to offer global planarization. 2,6 During CMP the tungsten-polishing mechanism is decided by both the formation of a passive oxide layer by slurry chemicals and the subsequent polishing by a slurry abrasive. 3 Kaufman et al. described the polishing mechanism of W CMP as the repeated formation and removal of the WO 3 layer. 2 The WO 3 layer is easily removed by the abrasive because the WO 3 layer is softer than the native W layer. 7 Therefore the oxidizer in the CMP slurry plays an important role in the high removal rate. 8 However when exposed tungsten is removed by CMP, the oxidizer in the CMP slurry attacks part of the seam on the W plug, 9 which is formed by CVD. The interaction between the oxidizer and the seam on the W plug results in the formation of a pit on the W plug, which is called a corning defect. Corning defects in memory devices have caused serious problems, such as electrical device degradation and leakage current in capacitor structures. This is true especially as the critical dimension of current semiconductor devices decreases below 70 nm. Therefore suppression of corning defects should be achieved to complete the formation of W plugs. Kishii et al. reported that W plugs could be formed without etching holes in seams by a MnO 2 slurry. 9 However the use of a MnO 2 slurry is improper for the formation of the W plug because the removal rate of the MnO 2 slurry is 10 times less than that of a commercial slurry based on fumed silica particles. Therefore a new approach is needed to suppress the corning defects. In this study, we considered the electrochemical properties of a W film as a critical factor to reduce its static etch rate and suppress the corning defects. Thus an attempt to control the potenti...

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Coordinatively and Electronically Unsaturated Tungsten(0) Carbonyl Complexes Stabilized by π-Donating Amido Ligands

Cited by 43 publications

References 15 publications

On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

Characterization of Three Members of the Electron‐Transfer Series [Fe(pda)₂]ⁿ (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non‐innocent Derivatives of N,N′‐Bis(pentafluorophenyl)‐o‐phenylenediamide(2−, 1^.−, 0)]

Constraints of the Corning on Plugs of W Film in W Chemical Mechanical Planarization

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Coordinatively and Electronically Unsaturated Tungsten(0) Carbonyl Complexes Stabilized by π-Donating Amido Ligands

Cited by 43 publications

References 15 publications

On the Electronic Structure of NiII Complexes That Feature Chelating Bisguanidine Ligands

On the Electronic Structure of NiII Complexes That Feature Chelating Bisguanidine Ligands

Characterization of Three Members of the Electron‐Transfer Series [Fe(pda)2]n (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non‐innocent Derivatives of N,N′‐Bis(pentafluorophenyl)‐o‐phenylenediamide(2−, 1.−, 0)]

Constraints of the Corning on Plugs of W Film in W Chemical Mechanical Planarization

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On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

On the Electronic Structure of Ni^II Complexes That Feature Chelating Bisguanidine Ligands

Characterization of Three Members of the Electron‐Transfer Series [Fe(pda)₂]ⁿ (n=2−, 1−, 0) by Spectroscopy and Density Functional Theoretical Calculations [pda=Redox Non‐innocent Derivatives of N,N′‐Bis(pentafluorophenyl)‐o‐phenylenediamide(2−, 1^.−, 0)]