Theoretical studies on titanium pentafulvene complexes

Bis(η5:η1‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

“…[35] Hydrogen atoms (apart from those at C6, C41 and C42) and isopropyl groups are omitted for clarity. Ellipsoids are set at 50 %p robability.S elected bond lengths []and angles [8 8]: Nb1-N1 1.7996 (10),N b1-C42 2.2648(11),C 1-C6 1.5147-(16), C21-C26 1.5213(13), C26-C41 1.5522 (14),C 41-C42 1.5310(15); Nb1-N1-C43 171.88(10), Nb1-C42-C411 14.85 (6).…”

“…[2] By using suitable pentafulvenes ligands,sodium or magnesium as reducing agents,a nd various Ti IV ,T i III ,Z r IV ,a nd Hf IV precursors,( h 5 :h 1 -C 5 H 4 CR 2 ) 2 M( M: Ti,Z r), [3] (h 5 :h 1 -C 5 H 4 CR 2 )(h 5 -C 5 R 5 )MX (M:T i, Zr,H f; X: Cl, R: H, Me), [4] and (h 5 :h 1 -C 5 H 4 CR 2 )(h 5 -C 5 H 5 ) 2 Zr [5] complexes become available in good yields on amultigram scale.The resulting p-h 5 :sh 1 coordination mode is attributed to as trong p backdonation from the metal to the fulvene moiety.T his coordination involves ac hange of the polarity (umpolung) of the exocyclic carbon atom of the fulvene ligand (C exo ). [6] This umpolung leads to astrong nucleophilic character of the C exo center compared to its electrophilic reactivity in the free ligand as used in the heydays of the pentafulvene chemistry in the early 1970s (Scheme 1). [7] Fort he (h 5 :h 1 -C 5 H 4 CR 2 ) 2 M( M: Ti,Z r) complexes, ab road range of subsequent reactions,s uch as electrophilic attack, [8] haptotropic shifts, [9] insertion of multiple-bondcontaining substrates (for example,n itriles,i sonitriles, imines,o rc arbonyl compounds), [3c, 10] and E À Hb ond activations are found.…”

Tricarbonyl-6,6′-dimethylfulvene chromium(0) – Structural properties

“…Fulvene complexes exhibit a wide range of coordination modes of the fulvene ligand to the metal center [3e6] depending on the transition metal, the oxidation state of the metal center, and the substituents of the fulvene ligand, ranging from peh 2 :peh 2 :peh 2 type to a single peh 2 coordination of the exocyclic CeC double bond [4,7]. For example, for chromium fulvene complexes redox-induced haptotropic rearrangements were described [8].…”

Endoscopic

“…In 2008, we reported on the synthesis of a [1],[1]disilamolybdenocenophane ( 1 ),8 which is distinctly different from the previously reported mono‐ and bis‐fulvene‐type molybdenocenophanes 7a,9. Compound 1 was prepared photochemically from the corresponding [2]disilamolybdenocenophane dihydride ( 1′ ) with elimination of dihydrogen.…”