Synthesis of Highly Functionalized Spirocycles and Pentafulvene-Containing Dyes Involving 2-(2'-ketoalkyl)-1,3-indandiones.

Synthesis of highly functionalized spiro[4.4]nonane and spiro[4.5]decane motifs by the reaction of dimethylacetylenedicarboxylate (DMAD) with 2-(2'-ketoalkyl)-1,3-indandiones and 2-(3'-ketoalkyl)-1,3-indandiones, respectively, has been developed by utilizing a catalytic amount of DABCO. The tertiary hydroxy-containing spiro[4.4]nonane products were converted into fully conjugated pentafulvene π-systems in an acidic medium through dehydration and unprecedented C-C bond rearrangement.

Vanadium Pentafulvene Complexes: Synthon for Unprecedented VanadoceneIII Derivatives.

The benzene ligand at CpV(η6 -C6 H6 ) (1) is exchanged for pentafulvenes. Using sterically demanding pentafulvenes gives a clean exchange reaction, yielding vanadium pentafulvene (2 a and 2 b) and benzofulvene complexes (3 a and 3 b). The molecular structures of the target compounds suggest a π-η5 :σ-η1 coordination mode with a vanadiumIII center. With the sterically low demanding 6,6-dimethylpentafulvene, a C-H activation at the leaving ligand is observed, yielding the ring-substituted vanadoceneII 4. The reactivity of the pentafulvene complexes was investigated. A series of unprecedented vanadoceneIII compounds were synthesized: Under mild conditions, E-H splitting of 4-tert-butylphenol, diphenylamine, and 2,6-diisopropylaniline yield well characterized examples of rare vanadoceneIII phenolate and amide complexes. Insertion reactions into the V-Cexo bond of the pentafulvene complexes by multiple bond containing substrates were found for acetone, 4-chlorobenzonitril and N,N'-dicyclohexylcarbodiimide.

Elemental Magnesium as an Early Transition Metal Substitute: From Pentafulvene Coordination to Deprotonation of Amines.

The reaction of magnesium turnings and 6,6-di-para-tolylpentafulvene was investigated. Under mild conditions, the magnesium dissolves, forming the MgII complex 1 with a π-η5 : σ-κ1 coordinating ligand of the dimerized pentafulvene, analyzed by NMR and XRD investigations. As a magnesium pentafulvene complex was a possible intermediate, amines were employed as intercepting agents. Thereby, the amines were formally deprotonated by elemental magnesium, yielding the first examples of Cp'Mg(THF)2 NR2 complexes. This reaction competes with the formation of 1 and a consecutive formal [1,5]-H-shift forming an ansa-magnesocene. Employing amines with low basicity gave quantitative conversion to the amide complexes.

(Carbazol-9-ido-κN)di-chlorido-(η5:η1-2,3,4,5-tetra-methyl-penta-fulvene)tantalum(V).

The reaction of (η5:η1-2,3,4,5-tetra-methyl-penta-fulvene)tantalum(V) dicarbazolide chloride (1) with etheric HCl results in the formation of the title compound (2), [Ta(C10H14)(C12H8N)Cl2]. The TaV atom has a distorted tetra-hedral coordination environment in a three-legged piano-stool fashion. The conformation of the penta-fulvene exocyclic C atom to the three other ligands is staggered and not eclipsed, as found in the crystal structure of 1. Inter-molecular inter-actions include π-π stacking, H⋯π inter-actions and weak C-H⋯Cl hydrogen bonds.

Coordination complexes of chromium(0) with a series of 1,3-diphenyl-6-aryl-fulvenes.

The synthesis and structural properties of a series of chromium tricarbonyl 'piano-stool' complexes bearing substituted penta-fulvene ligands were studied. The complexes, tricarbon-yl(1,3,6-tri-phenyl-fulvene)chromium(0) benz-ene hemisolvate, [Cr(C24H18)(CO)3]·0.5C6H6 (I), tricarbon-yl[1,3-di-phen-yl-6-(3-vinyl-phen-yl)fulvene]chromium(0), [Cr(C26H20)(CO)3] (II), and tricarbon-yl[1,3-diphenyl-6-(pyren-1-yl)fulvene]chromium(0), [Cr(C34H22)(CO)3] (III), each have a distorted octa-hedral geometry, with the fulvene coordinated in a π-η2:π-η2:π-η2 fashion. Significant deviation of the exocyclic fulvene double bond from the cyclo-penta-diene plane accompanies coordination. Evidence of non-covalent π-π inter-actions was observed in both (I) and (III), with centroid-to-centroid distances ranging from 3.330 (8) to 3.494 (8) Å.

Crystal structure of the formal 20 electron zirconocene penta-fulvene complex Cp2Zr(η5,η1-adamantyl-idene-penta-fulvene):toluene:n-hexane = 1:0.125:0.125.

The crystal structure of a solvated zirconocene penta-fulvene complex with a bulky adamantyl-idene substitution pattern, namely (η5,η1-adamantyl-idene-penta-fulvene)bis-(η5-cyclo-penta-dien-yl)zirconium(IV)-toluene-n-hexane (8/1/1), [Zr(C15H18)(C5H5)2]·0.125C7H8·0.125C6H14, is reported. Reducing zirconocene dichloride with magnesium results in the formation of a low-valent zirconocene reagent that reacts readily with adamantyl-idene-penta-fulvene to give the aforementioned complex. Single crystal X-ray diffraction proves the dianion-like η5:η1 binding mode of the fulvene ligand to the central ZrIV atom. The asymmetric unit contains four independent mol-ecules of [η5:η1-adamantyl-idene-penta-fulvene]bis-[(η5)-cyclo-penta-dien-yl]zirconium(IV), together with half a mol-ecule of toluene disordered with half a mol-ecule of n-hexane (the solvent mol-ecules have no direct influence on the complex). In each of the four complex mol-ecules, the central ZrIV atom has a distorted tetra-hedral coordination environment. The measured crystal consisted of two domains with a refined ratio of 0.77:0.23.

Formation of Binuclear Zigzag Hexapentaene Titanium Complexes via a Titanacumulene [Ti=C=C=CH2 ] Intermediate.

The reaction of bis(η5 :η1 -pentafulvene)titanium complexes with an allylidenephosphorylide Ph3 P=C(H)- C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C6 H4 unit can be described as a spontaneous double C-H bond activation process, leading to an R3 P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR )2 Ti=C=C=CH2 ] (R: 2-adamantyl, CH(p-tol)2 ). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single-crystal X-ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.