Synthesis, Structural Authentication, and Structurally Defined Metalation Reactions of Lithium and Sodium DA-Zincate Bases (DA = diisopropylamide) with Phenylacetylene

Abstract

In a study aimed at developing the diisopropylamido (DA) chemistry of zincates, the new lithium DA-zincate [(TMEDA) • Li( t Bu)(DA)Zn( t Bu)] (4) has been synthesized by an interlocking cocomplexation approach comprising mixing of its three component chemicals, LDA, t Bu 2 Zn, and TMEDA, in a 1:1:1 ratio in hexane solution. Previously made by transamination from the corresponding TMP-zincate, the known sodium congener [(TMEDA) • Na( t Bu)(DA)Zn( t Bu)] (2) was also synthesized by this approach, substituting NaDA for LDA. Closely resembling each other, their molecular structures determined by X-ray crystallography can be categorized as contact ion-pair ates of TMEDA-chelated alkali metal cations linked to trigonal-planar dialkyl-Zn anions via bridging DA ligands. Reaction of 4 and 2 with phenylacetylene affords the bimetallic acetylides [{(TMEDA) • Li(CtCPh) 2 Zn( t Bu)} 2 • (TMEDA)] ( 5) and [{(TMEDA) • Na(CtCPh) 2 Zn( t Bu)} 2 ] (6), respectively. X-ray crystallographic studies reveal 5 is a pseudodimer (tetranuclear) with two (LiCZnC) rings linked at the Zn atoms by a bridging, nonchelating TMEDA ligand; in contrast 6 adopts a distorted cubane of alternating PhCtC and metal (2 Na, 2 Zn) corners. For comparison, the synthesis and crystal structures of the neutral zinc complexes [(TMEDA) • Zn(CtCPh) 2 ] (7) and [(TMEDA) • Zn( t Bu)(CtCPh)] ( 8), formally components of the ate complexes 5 and 6, are also reported. In addition, the 1 H and 13 C NMR spectra of 2, 4, 5, 6, 7, and 8 recorded from solutions in C 6 D 6 are disclosed.

Structural and Magnetic Insights into the Trinuclear Ferrocenophane and Unexpected Hydrido Inverse Crown Products of Alkali‐Metal‐Mediated Manganation(II) of Ferrocene

“…The structure of 1 is completed by weak toluene solvation of the sodium cations, covering the "head-and foot-rest" positions in the ring (Na···centroid 3.165 ). The Mn II inverse crowns [(TMP) 6 Na [16] [Na 2 Mn 2 A C H T U N G T R E N N U N G (HMDS) 4 (O)] [18] and [Li 2 Mn 2 - [18] all show Na À guest or Li À guest interactions (i.e., Na À arene, Na À O or Li À O interactions) with no further solvation of the Na (or Li) required. This p solvation of Na in the host ring of 1 compensates for the absence of any significant NaÀguest interactions, making it a new feature for the emerging Mn II family of inverse crown structures.…”

“…[1,2] Direct metalation reactions (metal-hydrogen exchange reactions) are usually the domain of highly reactive, highly polar organometallics, most typically alkyllithium or lithium amide compounds. [3,4] However, these alkali-metal ate reagents, typically constructed from a less electropositive metal such as Mg, [5] Al [6][7][8] or Zn [9][10][11][12][13] and an alkali-metal amide, allow low-polarity (i.e., Mg, Al or Zn) metalations of various organic substrates. As the alkali metal is essential, but does not perform the deprotonation directly, these bimetallic-dictated reactions can be described as examples of alkali-metal-mediated metalation (AMMM), in which M = Mg, Al or Zn.…”

Synthesis, Structure, and Reactivity of a Tetranuclear Amidinato Zinc Hydride Complex

“…(1.20(2) Å), [Zn(CC-CCSiMe3)(NPEt3)]4 (1.22(1) Å), [10] [(dpp-BIAN)Zn(μ-CCPh)]2 (1.2099(17) Å), [11] DippNacNacZnCCPh (1.207(3) Å), [12] as well as to the base-stabilized complex (PhCC)2Zn(tmeda) (1.211(5), 1.219(5) Å), [13] respectively. The CC triple bond lengths in 5 (1.170( 5)-1.183(3) Å) are shorter than in 4 but comparable to that reported for free acetylene (1.126(8) Å at 140K).…”

“…2a [3] and sodium phenylacetylene [17] were prepared according to literature methods. 1 H and 13 C NMR spectra were recorded on a Bruker DMX 300 spectrometer and are referenced to internal C6D5H…”

Zinc, cadmium and mercury

“…A series of ''highly coordinated'' tetra-substituted zincate compounds, [Li(TMEDA)] 2 [Zn(NMe 2 ) 3 Me] and [Li(TMEDA)] 2 [ZnMe 4 ] were presented and structurally characterized, 18 and the metallation reaction between Li-and Na-diisopropylamide zincate bases with phenylacetylene was published. 19 The reactivity of similar sodium TMP-zincates with nitrile compounds has been the subject of a separate study. 20 The reaction between ZnCl 2 (TMEDA) and dilithioferrocene afforded ''the first example of a first row transition metal-bridged [1.1]ferrocenophane'', which was shown to exist in the anti-conformation by X-ray crystallography.…”