The Utility of Sodium Diisopropylamide (NADA): Formation of a New Transition Metalate via Silyl Migration Chemistry, [(η⁵-Me₃SiC₅H₄)Fe(CO)(PPh₃)]⁻Na⁺(SiFpPNa), and Resulting Thermal Rearrangements of the Complexes SiFpP−CH₂SiMe₂R (R = H, SiMe₃) to SiFpP−SiMe₂CH₂R

Abstract

A new transition metalate system, [(η 5 -Me 3 SiC 5 H 4 )Fe(CO)(PPh 3 )] -M þ (SiFpPM; M = Li, Na), was synthesized via treatment of (η 5 -C 5 H 5 )Fe(CO)(PPh 3 )SiMe 3 with sodium and lithium diisopropylamides (MN(iPr 2 ); NADA and LDA, respectively). The utility of NADA was far superior to that of LDA, with shorter reaction times, lower reagent concentrations, and higher yields. Infrared spectroscopic analysis of the new ferrates indicated that their stability and utility were dependent upon the tight ion pairs Fe-CO-M; in the presence of coordinating solvents and ionophores the separated ion pairs formed led to the expulsion of the PPh 3 and CO scavenging led to formation of the dicarbonylferrate [(η 5 -Me 3 SiC 5 H 4 )Fe(CO) 2 ] -M þ . Hexane was the solvent of choice for formation and use of the ferrates. Reactions of the new ferrates with MeI led to [SiFpP]CH 3 , whereas reactions with ClCH 2 SiMe 2 R (R = H, SiMe 3 ) did not lead to the expected Fe-C bonded complexes [SiFpP]CH 2 SiMe 2 R but to high yields of the rearranged complexes [SiFpP]SiMe 2 CH 2 R. The presence of the thermally labile phosphine group readily produces a coordinatively unsaturated 16e species that permits Fe-CH 2 -SiMe 2 R to FeSiMe 2 CH 2 R rearrangements (previously observed photochemically with the simple Fp derivatives) to occur thermally.

Iron distannanes (η5-C5H5)Fe(CO)2SntBu2SntBu2X, (X=Cl, OMe): Thermal and photochemical transformations to iron stannylstannylenes

“…Attempts to synthesize 1 via homogeneous reactions in ethereal solvents were unsuccessful resulting in a mixture of products among which we could identify FpSn t Bu 2 Cl, a previously characterized complex [8]. The utility of such heterogeneous reactions of the Fp salt [9], or use of non-coordinating solvents for soluble variants of the Fp anion [10], to yield desired products rather than side-products involving (1) -NaCl secondary reactions has been reported previously. Clearly the ionpairing aspect of the salt is important.…”

Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Arene Metalations

“…Metalation of substituted arenes by NaDA must have been examined and possibly even reported, but our failure to find a literature example underscores a glaring omission (eq 2 ). In this paper, we describe NaDA-mediated arene sodiation from a synthetic organic and mechanistic perspective …”

Structure, Reactivity, and Synthetic Applications of Sodium Diisopropylamide

“…Other uses of NaDA (Scheme 11) include the metalation of diphenylmethane, 7 a cyclopentadienyl iron complex, 39 fluoroform, 40 and a few ketones (vide infra). The dates…”

“…31 The practicality of the protocol is illustrated by isomerization of neat 37b with catalytic NaDA. Rate studies showed a curious alternating preference for tri-, di-, and tri-solvated dimers with increasing substituent size from Me 3 Si to t-BuMe 2 Si to i-Pr 3 Si (39)(40)(41). Substitution at the 3-position (42 and 43) affords dienes (Scheme 18), whereas an alkyl moiety at the one position simply fails to isomerize.…”