A Novel Group of Alkaline Earth Metal Amides:  Syntheses and Characterization of M[N(2,6-ⁱPr₂C₆H₃)(SiMe₃)]₂(THF)₂(M = Mg, Ca, Sr, Ba) and the Linear, Two-Coordinate Mg[N(2,6-ⁱPr₂C₆H₃)(SiMe₃)]₂

Abstract

Novel alkaline earth metal aryl-substituted silylamides were prepared using alkane (Mg) and salt elimination reactions (Mg, Ca, Sr, and Ba). The salt elimination regime involved the treatment of the alkaline earth metal iodides with 2 equiv of the respective potassium amide KNDiip(SiMe(3)), (Diip = 2,6-i-Pr(2)C(6)H(3)). The organomagnesium source for the alkane elimination was ((n)()Bu/(s)()Bu)(2)Mg. All compounds were characterized using (1)H, (13)C NMR, and IR spectroscopy, in addition to X-ray crystallography (except Mg[NDiip(SiMe(3))](2)THF(2)). Crystal data with Mo Kalpha (lambda = 0.710 73 A) are as follows: Mg[NDiip(SiMe(3))](2), 1, a = 9.4687(6) A, b = 9.6818(6) A, c = 17.9296(1) A, alpha = 96.487(1) degrees, beta = 94.537(1) degrees, gamma = 89.222(1) degrees, V = 1608.8(2) A(3), Z = 2 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0508; (n)()BuMg[NDiip(SiMe(3))]THF(2), 2, a = 9.5413(1) A, b = 16.493(2) A, c = 9.8218(1) A, beta = 108.149(2) degrees, V = 1468.7(4) A(3), Z = 2, monoclinic, space group P2(1), R1(all data) = 0.1232; Ca[NDiip(SiMe(3))](2)THF(2), 4, a = 9.7074(1) A, b = 20.9466(4) A, c = 21.6242(3) A, alpha = 73.573(1) degrees, beta = 78.632(1) degrees, gamma = 89.621(1) degrees, V = 4129.1(1) A(3), Z = 4 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0902; Sr[NDiip(SiMe(3))](2)THF(2), 5, a = 20.5874(5) A, b = 9.8785(2) A, c = 20.8522(5) A, beta = 102.035(2) degrees, V = 4147.6(2) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0756; Ba[NDiip(SiMe(3))](2)THF(2), 6, a = 20.5476(2) A, b = 10.0353(2) A, c = 20.9020(4) A, beta = 101.657(1) degrees, V = 4221.0(1) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0573.

Advances in alkaline earth-nitrogen chemistry

“…Again, M· · ·C() contacts from the phenyl substituents arise to help stabilize the metal center (Table 6). Along with Mg[N(SiMe 3 )(Dipp)] 2 [67], (Dipp = 2,6-di-isopropyltrimethylsilylphenyl) which will be described in a subsequent section, Mg[N(SiMe 3 )(SiPh 2 t Bu)] 2 and Mg[N(SiMePh 2 ) 2 ] 2 represent the only three examples of two-coordinate magnesium amides. Replacement of all methyl substituents from a -SiMe 3 moiety by phenyl substituents affords a four-coordinate species Ca[N(SiMe 3 )(SiPh 3 )] 2 (thf) 2 (Scheme 2, Route i), where M· · ·C() and M· · ·H-C agostic interactions arise further stabilizing the metal center (Table 6) [66].…”

Structural Diversity in Alkali Metal and Alkali Metal Magnesiate Chemistry of the Bulky 2,6‐Diisopropyl‐N‐(trimethylsilyl)anilino Ligand

“…However, potassium has been observed in interesting transition‐metal bimetallic systems reported by Tilley14 that demonstrate the large, soft alkali metal's propensity for engaging with arene‐π systems (Figure 1). 15 While Ruhlandt‐Senge16 has described two‐coordinate [Mg{N(SiMe 3 )(Dipp)} 2 ] and the THF solvate [(THF) 2 Mg{N(SiMe 3 )(Dipp)}( n Bu)], and [Mg{N(SiMe 3 )(Dipp)} 2 (OEt 2 )]17 was described by our group, to the best of our knowledge no alkali metal magnesiate has hitherto been reported. Therefore this study sets out to fill in important gaps in the alkali metal chemistry of [N(SiMe 3 )(Dipp)] − and to synthesise and characterise the first magnesiate examples as a prerequisite to determining whether this amide also possesses synergistic template base potential 1…”

Synthesis, Structures and Characterization of the Calcium Pyrrolates [Ca{(2‐(dimethylaminomethyl)pyrrolyl}2 donorn] (donor = THF and pyridine, n = 2; DME and TMEDA, n = 1) as Potential Precursors for Solid‐State Applications

“…The initial starting point was salt elimination, used successfully for the preparation of amidocalcium derivatives. [6,8] Following a similar procedure, we obtained an inseparable precipitate containing the pyrrolyl target compound and potassium iodide. A change in reaction conditions did not improve this result.…”

“…Derivatives of the hexamethyldisilazane ligand replacing one trimethylsilyl group by a bulky aromatic substituent display a reduced tendency towards NϪSi bond cleavage and have partially fulfilled the aim for volatile precursors. [8] Still, advanced amido-based precursors would avoid the presence of silyl groups altogether, but synthetic difficulties have so far precluded the preparation of these highly reactive materials. [9] Volatile precursor materials will likely consist of monomeric compounds.…”