Organoscandium chemistry

Structure of (C₅H₅)Sc(CH₂tms)₂(thf) (tms = Si(CH₃)₃, thf = tetrahydrofuran).^[1]

Organoscandium chemistry is an area with organometallic compounds focused on compounds with at least one carbon to scandium chemical bond.^[2]^[3] The interest in organoscandium compounds is mostly academic but motivated by potential practical applications in catalysis, especially in polymerization. A common precursor is scandium chloride, especially its THF complex.^[4]

As with the other elements in group 3 – e.g. yttrium, forming organoyttrium compounds – and the lanthanides, the dominant oxidation state for scandium in organometallic compounds is +3 (electron configuration [Ar] 3d¹4s²). The members of this group also have large ionic radii with vacant s,p and d orbitals (88 pm for Sc³⁺ compared to 67 pm for Al³⁺) and as a result they behave as hard Lewis acids and tend to have high coordination numbers of 9 to 12. The metal to ligand chemical bond is largely ionic.

Illustrative complexes

Sc(III) derivatives

Many organoscandium(III) compounds have at least one cyclopentadienyl-type ligand. The reaction of scandium trichloride with two equivalents of sodium cyclopentadienide (NaCp) produces the chloride-bridged dimer:

2 ScCl₃ + 4 NaCp → [Cp₂Sc(μ-Cl)]₂ + 4 NaCl

Cp₃Sc is a polymer wherein one third of the Cp ligands serving as bridging ligands.^[5]

Bulkier cyclopentadienide ligands give monoscandium derivatives, e.g. (C₅Me₅)₂ScCl.^[6] The corresponding alkyls polymerize alkenes.^[7] ^[8]

The synthesis of a tris(allyl)scandium complex is analogous to the above methods, involving the reaction of ScCl₃ with allyl potassium in THF solution, The product is Sc(C₃H₅)₃(THF)₂ wherein two allyl ligands are η³ coordinated and one allyl ligand is η¹.^[9]

Sc(II) and Sc(I) derivatives

Organoscandium compounds in lower oxidation states have been prepared.^[10]^[11]

References

^ Li, Xiaofang; Nishiura, Masayoshi; Hu, Lihong; Mori, Kyouichi; Hou, Zhaomin (2009). "Alternating and Random Copolymerization of Isoprene and Ethylene Catalyzed by Cationic Half-Sandwich Scandium Alkyls". Journal of the American Chemical Society. 131 (38): 13870–13882. doi:10.1021/ja9056213. PMID 19728718.
^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
^ C. Elschenbroich, A. Salzer Organometallics : A Concise Introduction (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7
^ Manzer, L. E. (1982). Tetrahydrofuran Complexes of Selected Early Transition Metals. Inorganic Syntheses. Vol. 21. pp. 135–140. doi:10.1002/9780470132524.ch31.
^ Atwood, Jerry L.; Smith, Karl D. (1973). "Crystal Structure of di-µ-chloro-bis[di-η-cyclopentadienylscandium(III)]". J. Chem. Soc., Dalton Trans. (22): 2487–2490. doi:10.1039/DT9730002487.
^ Huynh, Winn; Culver, Damien B.; Tafazolian, Hosein; Conley, Matthew P. (2018). "Solid-state ⁴⁵Sc NMR Studies of Cp*₂Sc–X and Cp*₂ScX(THF)". Dalton Transactions. 47 (37): 13063–13071. doi:10.1039/C8DT02623H. PMID 30160275.
^ Thompson, Mark E.; Baxter, Steven M.; Bulls, A. Ray; Burger, Barbara J.; Nolan, Michael C.; Santarsiero, Bernard D.; Schaefer, William P.; Bercaw, John E. (1987). "σ-Bond Metathesis for Carbon-Hydrogen Bonds of Hydrocarbons and Sc-R (R = H, alkyl, aryl) Bonds of Permethylscandocene Derivatives. Evidence for Noninvolvement of the π System in Electrophilic Activation of Aromatic and Vinylic C-H Bonds". Journal of the American Chemical Society. 109: 203–219. doi:10.1021/ja00235a031.
^ Bouwkamp, Marco W.; Budzelaar, Peter H. M.; Gercama, Jeroen; Del Hierro Morales, Isabel; De Wolf, Jeanette; Meetsma, Auke; Troyanov, Sergei I.; Teuben, Jan H.; Hessen, Bart (2005). "Naked (C₅Me₅)₂M Cations (M = Sc, Ti, and V) and Their Fluoroarene Complexes" (PDF). Journal of the American Chemical Society. 127 (41): 14310–14319. doi:10.1021/ja054544i. PMID 16218625.
^ Standfuss, Sabine; Abinet, Elise; Spaniol, Thomas P.; Okuda, Jun (2011). "Allyl Complexes of Scandium: Synthesis and Structure of Neutral, Cationic and Anionic Derivatives". Chemical Communications. 47 (41): 11441–11443. doi:10.1039/C1CC14180E. PMID 21946865.
^ Polly L. Arnold; F. Geoffrey; N. Cloke; Peter B. Hitchcock & John F. Nixon (1996). "The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring". J. Am. Chem. Soc. 118 (32): 7630–7631. doi:10.1021/ja961253o.
^ Ana Mirela Neculai; Dante Neculai; Herbert W. Roesky; Jörg Magull; Marc Baldus; et al. (2002). "Stabilization of a Diamagnetic Sc^IBr Molecule in a Sandwich-Like Structure". Organometallics. 21 (13): 2590–2592. doi:10.1021/om020090b.

[1] Li, Xiaofang; Nishiura, Masayoshi; Hu, Lihong; Mori, Kyouichi; Hou, Zhaomin (2009). "Alternating and Random Copolymerization of Isoprene and Ethylene Catalyzed by Cationic Half-Sandwich Scandium Alkyls". Journal of the American Chemical Society. 131 (38): 13870–13882. doi:10.1021/ja9056213. PMID 19728718.

[2] Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997

[3] C. Elschenbroich, A. Salzer Organometallics : A Concise Introduction (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7

[4] Manzer, L. E. (1982). Tetrahydrofuran Complexes of Selected Early Transition Metals. Inorganic Syntheses. Vol. 21. pp. 135–140. doi:10.1002/9780470132524.ch31.

[5] Atwood, Jerry L.; Smith, Karl D. (1973). "Crystal Structure of di-µ-chloro-bis[di-η-cyclopentadienylscandium(III)]". J. Chem. Soc., Dalton Trans. (22): 2487–2490. doi:10.1039/DT9730002487.

[6] Huynh, Winn; Culver, Damien B.; Tafazolian, Hosein; Conley, Matthew P. (2018). "Solid-state ⁴⁵Sc NMR Studies of Cp*₂Sc–X and Cp*₂ScX(THF)". Dalton Transactions. 47 (37): 13063–13071. doi:10.1039/C8DT02623H. PMID 30160275.

[7] Thompson, Mark E.; Baxter, Steven M.; Bulls, A. Ray; Burger, Barbara J.; Nolan, Michael C.; Santarsiero, Bernard D.; Schaefer, William P.; Bercaw, John E. (1987). "σ-Bond Metathesis for Carbon-Hydrogen Bonds of Hydrocarbons and Sc-R (R = H, alkyl, aryl) Bonds of Permethylscandocene Derivatives. Evidence for Noninvolvement of the π System in Electrophilic Activation of Aromatic and Vinylic C-H Bonds". Journal of the American Chemical Society. 109: 203–219. doi:10.1021/ja00235a031.

[8] Bouwkamp, Marco W.; Budzelaar, Peter H. M.; Gercama, Jeroen; Del Hierro Morales, Isabel; De Wolf, Jeanette; Meetsma, Auke; Troyanov, Sergei I.; Teuben, Jan H.; Hessen, Bart (2005). "Naked (C₅Me₅)₂M Cations (M = Sc, Ti, and V) and Their Fluoroarene Complexes" (PDF). Journal of the American Chemical Society. 127 (41): 14310–14319. doi:10.1021/ja054544i. PMID 16218625.

[9] Standfuss, Sabine; Abinet, Elise; Spaniol, Thomas P.; Okuda, Jun (2011). "Allyl Complexes of Scandium: Synthesis and Structure of Neutral, Cationic and Anionic Derivatives". Chemical Communications. 47 (41): 11441–11443. doi:10.1039/C1CC14180E. PMID 21946865.

[10] Polly L. Arnold; F. Geoffrey; N. Cloke; Peter B. Hitchcock & John F. Nixon (1996). "The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring". J. Am. Chem. Soc. 118 (32): 7630–7631. doi:10.1021/ja961253o.

[11] Ana Mirela Neculai; Dante Neculai; Herbert W. Roesky; Jörg Magull; Marc Baldus; et al. (2002). "Stabilization of a Diamagnetic Sc^IBr Molecule in a Sandwich-Like Structure". Organometallics. 21 (13): 2590–2592. doi:10.1021/om020090b.

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