General Preparation of Cyclopentadienyl Molybdenum Dicarbonyl η³-2-Alkylidene Cyclobutanonyl Complexes

Abstract

Cyclopentadienylmolybdenumdicarbonyl anion reacts with a variety of allenic electrophiles to produce η 3 -2-alkylidene cyclobutanoyl complexes. Three of these complexes have been characterized by X-ray crystallography, and the 2-alkylidene cyclobutanone has been removed and recovered from one complex via oxidative demetalation.

Preparation and Subsequent Reaction Chemistry of Cyclopentadienyl Molybdenum Dicarbonyl η3-2-Alkylidene Cyclobutanonyl Complexes

“…12,13 The X-ray crystal structure of 9 indicated that the σ-bond representation (9b) that contains a methylidene cyclobutanone was a better model of this complex than 9a. 8 The solid state structure of this complex showed that the π-allyl portion of the molecule was exo (9) with respect to the CpMo-(CO) 2 fragment. 14 Faller had previously observed acyclic π-allyls substituted on both the 1 and 2 positions also have high exo:endo ratios, 15 and our observations here were consistent with those previous reports.…”

“…7,10 Reaction of the CpMo(CO) 3 anion 4 (M ) Na) 11 with tosylate 5 initially produced 6; however, 6 rapidly underwent further reaction at 25 °C to produce another air-stable yellow complex, which we identified as alkylidene cyclobutanonyl complex (9). 7,8 We could account for the formation of 9 via a CO insertion (alkyl migration) from 6 to form 8 followed by an alkene insertion. There is ample precedent for a σ-acyl π-alkene complex like 8 in cyclopentadienyl molybdenum, tungsten, and iron chemistry involving other alkenyl or allenyl ligands.…”

“…7 Last year, we communicated the results of a number of reactions of methyl-substituted allenic electrophiles with the CpMo(CO) 3 anion. 8 Here we give full details of the reactions of a number of methyl-and phenyl-substituted allenic electrophiles with the CpMo(CO) 3 anion to produce a number of alkylidene cyclobutanonyl and η 3 -butadienyl complexes, several of which have also been characterized by X-ray crystallography. Details of subsequent demetalation and enolate reaction chemistry of the product alkylidene cyclobutanonyl complexes are also presented.…”

12 Chromium, molybdenum and tungsten

“…Three of these, including 5, have been characterised by X-ray crystallography. 54 The Z-cycloheptatrienyl complexes [M(Z-C 7 H 7 )(L)I 2 ] (M Mo, W; L MeCN, PPh 3 ) activated with Me 3 SiCH 2 MgCl catalyse the ring-opening polymerisation of norbornene to give poly(1,3-cyclopentylenevinylene) in high yield. The tungsten complexes are more active but less selective than their molybdenum analogues.…”

Addition of Aromatic C−H Bonds to Terminal Metal−Carbonyl Groups. A New Method for Cyclocarbonylation of Aromatic Groups

“…Two possible mechanisms are shown in Scheme . Previously, Rosenblum reported that protonation of propargylmetal compounds yielded metal−η 2 -cis-allene cation A as the kinetically favorable intermediate. This cis-configuration of A is very important because it allows intramolecular attack of its tethered 2,5-dimethoxybenzene group at the coordinated CO group to effect an electrophilic substitution, yielding species B and C sequentially.…”