Reactivity of Scorpionate-Anchored Yttrium Alkyl Complex toward Organic Nitriles

Reactivity of Rare Earth Metal Alkyl Complexes with Nitriles or Isonitrile: Versatile Ways toward Multiply Functionalized β-Diketiminato, (Iso)indolyl, and Imidazolyl Chelating Rare Earth Metal Complexes

The reactivity of the rare earth metal alkyl complexes LRE(CH2SiMe3)(THF)2 (1RE) [RE = Y (1Y), Yb (1Yb), Lu (1Lu); L = 2,5-[(2-pyrrolyl)CPh2]2(N-methylpyrrole)] with various nitriles and isonitriles has been fully developed. Treatment of the yttrium monoalkyl complex (1Y) with 2 equiv of aromatic nitriles afforded the symmetric trisubstituted β-diketiminato yttrium complexes (2Y(H), 2Y(Me), and 2Y(F)) through successive cyano group insertion into the RE-C bond and 1,3-H shift or the unsymmetric trisubstituted β-diketiminato yttrium complex (3Y) unexpectedly via a 1,3-SiMe3 shift when 4-(trifluoromethyl)benzonitrile was used in this reaction under the same conditions. By treating 1Y with 2 equiv of tolyl acetonitrile, an activation of the sp3 C-H bond occurred to form the corresponding β-aryl keteniminato complexes 4Y(p-tol) and 4Y(m-tol). Remarkably, a heteroleptic cleavage of the CO-CN bond took place in the reaction of 1Y with benzoyl nitrile, affording the unsymmetric trinuclear yttrium complex 5Y bridged by three cyanide groups. Dinuclear ytterbium and lutetium complexes 6Yb and 6Lu containing a functionalized isoindole fragment were synthesized from the reactions of 1 with phthalonitrile by tandem insertion and cyclization. Further studies indicated that the temperature and stoichiometric ratio have a great influence on the reactivity patterns between the reactions of 1RE with benzylisonitrile: two tetrasubstituted β-diketiminato complexes 8 and 9 were obtained at -30 °C, and tetrasubstituted imidazolyl yttrium and lutetium complexes 7 were isolated at elevated temperature, respectively. In addition, the tetrasubstituted β-diketiminato complexes 8 and 9 could be irreversibly converted to the cyclization products 7 by elevating the reaction temperature not only on the NMR scale but also on the preparative scale. Notably, when the phenyl isonitrile instead of benzyl isonitrile was reacted with 1Yb, a 2,3-functionalized indolyl ytterbium complex 10Yb was isolated.

Reversible addition of tin(II) amides to nitriles

Lappert's stannylene (Sn[N(SiMe₃)₂]₂) has been reacted with various nitriles, dinitriles and trinitriles with the formation of heteroleptic amidotin(II) amidinates of the general formulae [RC(NSiMe₃)₂]SnN(SiMe₃)₂, R'{[C(NSiMe₃)₂]SnN(SiMe₃)₂}₂ and R''{[C(NSiMe₃)₂]SnN(SiMe₃)₂}₃, where R = Ph (1), 2-(CN)-C₆H₄ (2), 3-(CN)-C₆H₄ (3); R' = 1,3-C₆H₄ (4), 1,4-C₆H₄ (5) and R'' = 1,3,5-C₆H₃ (6). The reactions of amidotin(II) benzamidinate 1 with an excess of benzonitrile proceed to homoleptic tin(II) bis(benzamidinate) [PhC(NSiMe₃)₂]₂Sn, which reversibly eliminates benzonitrile and 1 when warmed. The premise of reversibility has been supported by a multinuclear time-dependent NMR study and a theoretical (DFT) description. On the other hand, magnesium(II) bis(benzamidinate) [PhC(NSiMe₃)₂]₂Mg (8) and lanthanum(II) tris(benzamidinate) [PhC(NSiMe₃)₂]₃La (7) have been synthesised from appropriate metal hexamethyldisilazides and benzonitrile.

Lanthanocene and Cerocene Alkyl Complexes: Synthesis, Structure, and Reactivity Studies

Lanthanocene and cerocene alkyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(CH₂C₆H₄-o-NMe₂) (Ln = La 3 and Ce 4) were obtained from the salt metathesis of {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(μ₃-κ³-O₃SCF₃)₂K(THF)₂}₂·THF (Ln = La 1·THF and Ce 2·THF) with LiCH₂C₆H₄-o-NMe₂. Reactivity of 3 and 4 toward various small molecules provides access to a series of lanthanide derivatives. For example, reactions of 3 and 4 with elemental chalcogens (sulfur and selenium) in 1:1 molar ratio give the lanthanide thiolates {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(μ-SCH₂C₆H₄-o-NMe₂)}₂ (Ln = La 5 and Ce 6) and selenolates {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln(μ-SeCH₂C₆H₄-o-NMe₂)}₂ (Ln = La 7 and Ce 8). The compounds 3 and 4 react with two equivalents of elemental chalcogens (sulfur and selenium) to afford the lanthanide disulfides {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln}₂(μ-η²:η²-S₂) (Ln = La 9 and Ce 10) and diselenides {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln}₂(μ-η²:η²-Se₂) (Ln = La 11 and Ce 12). The lanthanide disulfides (9 and 10) or diselenides (11 and 12) can also be readily obtained through oxidation of the corresponding lanthanide thiolates (5 and 6) or selenolates (7 and 8) by elemental chalcogens concomitant with the (Me₂N-o-C₆H₄CH₂)₂E₂ (E = S or Se) release. Treatment of 3 and 4 with one equivalent or two equivalents of benzonitrile produces the serendipitous lanthanum and cerium-1-azaallyl complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln[N(H)C(Ph)═CHC₆H₄-o-NMe₂] (Ln = La 13 and Ce 14) or amidine complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln[N(H)C(Ph)NC(Ph)═CHC₆H₄-o-NMe₂]·C₇H₈ (Ln = La 15·C₇H₈ and Ce 16·C₇H₈), respectively. The compound 15 or 16 can also be readily synthesized by further insertion of one benzonitrile molecule into the 1-azaallyl complex 13 or 14. Insertion of N,N'-dicyclohexylcarbodiimide or phenyl isothiocyanate into Ln-C bonds within 3 and 4 results in the formation of the amidine complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln[CyNC(CH₂C₆H₄-o-NMe₂)NCy] (Cy = cyclohexyl, Ln = La 17 and Ce 18) or thioamidato complexes [η⁵-1,3-(Me₃C)₂C₅H₃]₂Ln[SC(CH₂C₆H₄-o-NMe₂)NPh] (Ln = La 19 and Ce 20). All of the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Reactivity of a β-diketiminate-supported magnesium alkyl complex toward small molecules

The reactivity of the magnesium alkyl {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(nBu)}2 (1) toward various small molecules provides access to a variety of magnesium derivatives. For example, the insertion of elemental chalcogens (S8 and Se8) into the Mg-C bond of complex 1 gives the dimeric magnesium thiolate {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(μ-SnBu)}2 (2), magnesium selenolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(SenBu)(THF) (3), and magnesium diselenolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(Se2nBu)(THF) (4). Meanwhile, compound 4 can be readily obtained by further insertion of one selenium atom into complex 3. Moreover, the reactions of complex 1 with diphenyl dichalcogenides (PhSSPh and PhSeSePh) by σ bond metathesis afford the corresponding magnesium phenyl chalcogenolates [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(EPh)(THF) (E = S 5, Se 6) concomitant with PhEnBu release. Furthermore, the treatment of complex 1 with benzonitrile and phenyl isothiocyanate produces the serendipitous magnesium-1-azaallyl complex [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(N(H)C(Ph)[double bond, length as m-dash]CHC3H7)(DME) (7) and the diimino-thioamidato magnesium compound {κ3-N,N',N''-(ArNCMe)2[N(Ph)CS]CH}Mg[(Ph)NC(nBu)S] (8) (Ar = 2,6-iPr2C6H3). In addition, deprotonation occurs between compound 1 and 1-methylimidazole to generate the imidazolyl complex {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(μ-Im)}2 (9) (Im = 2-N-methylimidazolyl). These results indicated that the butylmagnesium complex 1 possesses high activity toward small molecules and revealed several unusual transformations. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Nitrile-nitrile C-C coupling at group 4 metallocenes to form 1-metalla-2,5-diaza-cyclopenta-2,4-dienes: synthesis and reactivity

The CC coupling of aryl nitriles at Group 4 metallocenes leads to unusual ring-strained 1-metalla-2,5-diaza-cyclopenta-2,4-dienes. The structural, energetic, and chemical properties of these complexes are described. The reactions of these compounds towards CH3 CN, H2 , CO2 , and HCl usually lead to the release of one nitrile and its replacement by different co-substrates.