Formation and Structures of [1,2–Bis(N-tert-butylcarbamoyl)cyclopentadienyl]zirconium Complexes – Coordination Chemistry of a “Fulvenologous” Malonic Amide Anion Ligand System

Abstract

Treatment of sodium cyclopentadienide with two molar equivalents of tert‐butyl isocyanate yields sodium 1,2‐bis(N‐tert‐butylcarbamoyl)cyclopentadienide (6). The [C5H3(1,2‐CONHCMe3)2]Na reagent 6 adds to Cp2Zr(CH3)Cl (8) to yield Cp2Zr(CH3)[C5H3(CONHCMe3)2] (9). In 9 the C5H3(CONHCMe3)2 ligand is bonded to zirconium through one of its carboxamido‐oxygen atoms (ĸO‐coordination). Treatment of 6 with CpZrCl3(THF)2 yields CpZrCl2[C5H3(CONHCMe3)2](THF) 11. In 11 the 1,2‐bis(N‐tert‐butylcarbamoyl)cyclopentadienide moiety serves as a Cs‐symmetric chelate ligand, binding to zirconium through both carbamoyl oxygens (ĸ2O,O′‐coordination). The same seven‐membered metallacyclic structural type is found in the reaction products of 6 with ZrCl4(THF)2 in 1:1 and 2:1 molar ratios. The former yields the distorted octahedral complex ZrCl3[C5H3(CONHCMe3)2](THF) (12), the latter gives the chiral octahedral system ZrCl2[C5H3(CONHCMe3)2]2 (13). In solution, complex 13 undergoes a thermally induced enantiomerization process (Λ → Δ interconversion), for which a Gibbs activation energy of ΔG‡enant = 14.0 ± 0.3 kcal mol−1 was determined by dynamic 1H‐NMR spectroscopy. The ĸ2O,O′‐coordination of the [C5H3(1,2‐CONHCMe3]− ligand in the complexes 11, 12, and 13 was secured by X‐ray crystal structure analyses.

Group 4 metallocenes in bioorganometallic chemistry

“…Another route utilized the strongly electrophilic character of the isocyanate function [19][20][21]. As a typical example, L-valin methylester (17) was converted to the isocyanate 18a by treatment with the (very toxic) ''phosgene dimer''.…”

Reactivity of the metal–cyclopentadienyl (indenyl, fluorenyl and cycloheptatrienyl) bonds

“…Whereas reaction of NaCp with 2 equiv. of t BuNCO leads to the selective formation of Na[C 5 H 3 -1,2-(CONH t Bu) 2 ] [19], the subsequent transmetalation reaction with metal halides of Group 8 leads to the formation of metallocene complexes M[g 5 -C 5 H 3 -1,2-(CONH t Bu) 2 ] 2 (M = Fe, Ru), but with metal halides of Group 4 giving the oxygen-coordinated complex Zr[j 2 -O,O-C 5 H 3 -1,2-(CONH t Bu) 2 ] 2 Cl 2 [18,20]. The coordination modes of the ligand depend strongly on the nature of the transition metal.…”

Acyl‐Functionalized Molybdenum Compounds [(η3‐C3H5)(η5‐Cp′)Mo(CO)2]: An Experimental Study Including the X‐ray Structure of a Rare endo Conformer

“…[2] The presence of electron-withdrawing groups in the Cp ring leads to a decrease in its electron density that may lead, in some cases, to an unusual bonding mode. [4] In a recent study we found that a similar substitu-tron-withdrawing acyl groups (e.g., -CHO, -COCF 3 ) show different outcomes in the protonation reactions compared with the parent cyclopentadienyl compound or derivatives bearing less electron-withdrawing groups (e.g., -COMe, -COPh). [4] In a recent study we found that a similar substitu-tron-withdrawing acyl groups (e.g., -CHO, -COCF 3 ) show different outcomes in the protonation reactions compared with the parent cyclopentadienyl compound or derivatives bearing less electron-withdrawing groups (e.g., -COMe, -COPh).…”

“…[1] So far, a large number of Cp ligands have been developed with a wide variety of substitution patterns, but only a few of the attached substituents, particularly perfluorinated ones, have shown strong electron-withdrawing properties when present in transitionmetal complexes. For example, Erker and co-workers described the κ 2 -O,O bonding of 1,2-(tBuNHCO) 2 C 5 H 3 in several zirconium(IV) compounds [3] whereas less oxophilic late-transition metals form the usual pentahapto coordination complexes. For example, Erker and co-workers described the κ 2 -O,O bonding of 1,2-(tBuNHCO) 2 C 5 H 3 in several zirconium(IV) compounds [3] whereas less oxophilic late-transition metals form the usual pentahapto coordination complexes.…”

“…For example, Erker and co-workers described the κ 2 -O,O bonding of 1,2-(tBuNHCO) 2 C 5 H 3 in several zirconium(IV) compounds [3] whereas less oxophilic late-transition metals form the usual pentahapto coordination complexes. For example, compounds bearing a cyclopentadienyl group with two ester or amide functions give cationic allyl complexes [(η 3 -C 3 H 5 )Mo(CO) 2 (NCMe) 3 ] + instead of the expected cyclopentadienyl molybdenum cations [(η 5 -CpЈ)Mo(CO) 2 -(NCMe) 2 ] + . This study has also revealed the increased reactivity of the formyl derivative [(η 3 -C 3 H 5 )(η 5 -C 5 H 4 CHO)Mo(CO) 2 ] towards aromatic amines.…”