An Extremely Bulky Tris(pyrazolyl)methanide: A Tridentate Ligand for the Synthesis of Heteroleptic Magnesium(II) and Ytterbium(II) Alkyl, Hydride, and Iodide Complexes

Abstract

The tris(pyrazolyl)methane compound HC(3-Ad-5-Mepz)3 [1, 3-Ad-5-Mepz=3-(1-adamantyl)-5-methylpyrazolyl] and its regioisomer, HC(3-Ad-5-Mepz)2 (3-Me-5-Adpz), were synthesized and crystallographically characterized. Deprotonation of 1 with MeLi afforded the lithium complex [{κ(3) -N-C(3-Ad-5-Mepz)3 }Li(thf)], which incorporates a tris(pyrazolyl)methanide ligand of unprecedented bulk. Reaction of 1 with MeMgI gave the ionic coordination complex [{κ(3) -N-HC(3-Ad-5-Mepz)3 }MgMe]I, which was readily deprotonated to afford the neutral compound [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgMe]. The related magnesium butyl compound [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgBu] was prepared from the reaction of 1 and MgBu2 . Treating this with LiAlH4 or LiAlD4 led to rare examples of terminal magnesium hydride/deuteride complexes, [{κ(3) -N-C(3-Ad-5-Mepz)3 }MgH/D]. All neutral magnesium alkyl and hydride compounds were crystallographically authenticated. Reaction of [{κ(3) κN-C(3-Ad-5-Mepz)3 }Li(thf)] with [YbI2 (thf)2 ] yielded the first structurally characterized f-block tris(pyrazolyl)methanide complex, [{κ(3) -N-C(3-Ad-5-Mepz)3 }YbI(thf)].

Formation and Reactivity of a Molecular Magnesium Hydride with a Terminal MgH Bond

“…This is significantly high-field shifted compared to that in the known terminal magnesium hydride complexes [(tBuNacnac)MgH(DMAP)] (d = 4.65 ppm; A), [2e] [(Ar*Nacnac)MgH] (d = 4.07 ppm; B), [4] and [{k 3 N-C(3-Ad-5-Mepz) 3 }MgH] (d = 5.68 ppm; C). [5] Differential scanning calorimetry (DSC) measurements of 3 revealed ad ecomposition temperature of 122 8C, close to that of [{k 3 N-C(3-Ad-5-Mepz) 3 }MgH] (C). [5] Ad ecomposition experiment performed in av olume-reduced NMR tube, as described by Harder et al, [2b] indicated the formation of dihydrogen in the 1 HNMR spectra.…”

Asymmetric Magnesium‐Catalyzed Hydroboration by Metal‐Ligand Cooperative Catalysis

“…However, aMg À Hspecies was not formed. [10] Thegroups of Nozaki and Hill reported several Mg À Bactivation modes. [11] Based on the literature 11 BNMR values and the Lewis acidity/basicity affinity,t he shift in the 11 BNMR activation of the HBpin is most probably due to adual MgÀOand OÀBcoordination.…”

“…From the different chiral (R)-(+ +)-BINOL scaffolds (1a-h)tested, magnesium complexes of ligand 1a provided the best enantioselectivity (entries 2vs. [7][8][9][10][11][12][13]. Finally,w ei nvestigated the effect of alkali salt additives as they can have an influence on the performance.However, only as light increase in enantioselectivity was observed (entry 14 vs.2 ).…”

Methanediide Formation via Hydrogen Elimination in Magnesium versus Aluminium Hydride Complexes of a Sterically Demanding Bis(iminophosphoranyl)methanediide

“…This, however, yielded a product mixture with stoichiometric HBpin, including some unreacted 1, and a product mixture with one major L-containing species ( 31 P{ 1 H} NMR resonance: δ 22.8 ppm) if an excess of HBpin is used. As a previously used alternative pathway to an MgH species on a sterically demanding monomeric tris(pyrazolyl)methanide MgnBu complex [35] (10), N(1)-P(1)-C(1)101.55 (13), N(2)-P(2)-C(1) 104.52 (14), P(4)-C(2)-P(3) 125.13 (19), N(3)-P(3)-C(2) 100.99 (14), N(4)-P(4)-C(2) 104.70 (14). (13), N(2)-P(2)-C(1) 104.52 (14), P(4)-C(2)-P(3) 125.13 (19), N(3)-P(3)-C(2) 100.99 (14), N(4)-P(4)-C(2) 104.70 (14).…”