Dichotomy of Enamines at the C⋮C Bond of a (1-Alkynyl)carbene Tungsten Complex. (1-Azoniabutadien-4-yl)carbonylmetalates (^-OC)₅WC(OEt)CR¹C(N⁺R₂)Me, Stable Torsion Isomers of (2-Aminoethenyl)carbene Complexes (OC)₅WC(OEt)CR¹C(NR₂)Me¹

Abstract

Addition of tertiary open-chain enamines R 1 HCdC(NR 2 )Me 7a-e [NR 2 ) pyrrolidine, N(i-Bu) 2 ; R 1) Ph, CO 2 Me, CO 2 Et, CO 2 Bz, CO 2 -t-Bu] to the 1-alkynylcarbene complex (CO) 5 WdC-(OEt)CtCPh (1a) affords novel (1-azoniabutadien-4-yl)carbonylmetalates ( -OC) 5 WC-(OEt)dC[C(dN + R 2 )Me]C(Ph)dCHR 1 (2E)-torquo-8a-f by dichotomy of the CdC(N) bond of 8 at the CtC bond of 1. Compounds (2E)-torquo-8 are stable in solid state but undergo (2E/2Z) isomerization in solution to give compounds (2Z)-torquo-8. X-ray structure analyses are reported of compounds (2E)-torquo-8e, (2E)-torquo-8f, and (2Z)-torquo-8a.

Organic Syntheses via Transition-Metal Complexes. 99.1Cyclopentadiene Annelation to Enolizable Cyclic Ketones via (1-Alkynyl)carbene Complexes (M = Cr, W)

“…tungsten complex (3 E )- 5a , δ 268.5; chromium complex (3 E )- 5b , δ 287.1) as well as of the C6−N unit (e.g. (3 E )- 5a , δ 157.2; (3 E )- 5b , 154.2) of compounds (3 E )- 5 are typically observed with planar and highly polarized enamino carbene complexes (OC) 5 MC(OEt)CH C(NR 2 )∼ of 3 E configuration 7 in a range clearly distinct from (nonplanar) torquo- carbiminium carbonylmetalates - (OC) 5 M−C(OEt)CHC(N + R 2 )∼ . The (planar) enamine structure of compounds ( E )- 5 is confirmed in the X-ray structure analysis of compound (3 E )- 5a by the dihedral angles C4−C5−C6−N7 = −173.8(8)°, C5−C6−N7−C8 = −174.6(9)°, and W−C4−C5−C6 = −176.7(6)° as well as by the pattern of nonalternating bond distances C4−C5 = 1.391(9) Å, C5−C6 = 1.392(9) Å, and C6−N7 = 1.346(9) Å within the ligand backbone, which indicates strong π-delocalization (Figure ).…”

Mesoionic Pyrrolium Complexes and Dihydropyrroles by Cycloaddition of (Non-enolizable) Imines to an [(1-Alkynyl)carbene]tungsten Complex

“…[1] Focusing more strongly on the reactivity of the CϭN bonds in aliphatic N(alkyl)-imines, e.g. PhCHϭCHϪCHϭN(iPr) yield (disystems, it was envisaged that non-enolizable imines might yield pyrrolium (ϭ azoniacyclopentadiene) complexes by tadienes by [3ϩ2] cycloaddition of (1-alkynyl)carbene com-similar to that found for iminium carbonylmetalates [10] derived from vinylogous seven-membered N-heterocyclic liplexes to HCϭC(N) bonds. [9] gands [7] (WϪC: δ ϭ 181.9).…”

Organic Syntheses via Transition Metal Complexes. 95.1 Rearrangement of (Cyclobutenyl)carbene Tungsten Complexes to 1-Tungsta-1,3,5-hexatrienes

“…Conjugated 6-amino-1-metalla-1,3,5-hexatrienes (CO) 5 MC(OEt)CHC(Ph)C(−)C(NR 2 )− ( C ) (Scheme , path b), resulting from addition of the enamine to the C⋮C bond of compound 1 , were shown to be key intermediates in these reactions. Other than tertiary enamines, reactions of tertiary enaminones with compounds 1 led to production of cross-conjugated metallahexatrienes (CO) 5 MC(OEt)C[C(NR 2 )−]C(Ph)CH−( B ) instead of conjugated 1-metalla-1,3,5-hexatrienes C by dichotomy of the −CHC(NR 2 )− unit at the C⋮C bond of compound 1 involving (cyclobutenyl)carbene complexes A as intermeditates (Scheme , path a) 1 Generation of Conjugated and Cross-Conjugated Metallatrienes via (Cyclobutenyl)carbene Complexes A (M = Cr, W) …”