Synthesis and reactions of acyl(cyclohexadienyl)manganates

Abstract

The cyclohexadienyl complexes [Mn(q5-C,H,R1)(CO),] 1 (R' = exo-H, M e or C,H,Me-4) react with LiR2 (R2 = M e or Ph) to give acylmetalates [Li(OEt,)] [Mn(7\5-C,H,R1)(CO),{C(0)R2}] 2. Complex 2 ( R1 = Me, R2 = Ph) has been characterised by an X-ray crystallographic study: orthorhombic, space group P212121, a = 9.1 13(2), b = 14.491 (8), c = 32.803(9) A, R = 0.064 for 1 4 5 8 independent reflections. Protonation of 2 with HBF,*Et20 induces an aryl-or alkyl-group transfer t o the endo face of the cyclohexadienyl ring yielding t h e new agostic cyclohexenyl complexes [Mn(q3:CHC6H,R1R2) (CO),] 3. The cyclohexenyl ligands can be decomplexed from the metal via treatment of 3 with 1,2-bis-(dipheny1phosphino)ethane (dppe) in tetrahydrofuran to afford mixtures of substituted cyclohexa-l,3dienes and [MnH(CO),(dppe)]. The acylmetalates 2 react with [NO] [BF,] at -78 "C to give [Mn(q5-C,H,R1) (CO) (NO){C(O) R2}] which decompose at room temperature to form the trans-disubstituted acylcyclohexadienes C,H,R1[C(0)R2]. Reaction of 2 with electrophiles SiMe,CI, [Me,O] [BF,] or [Et,O] [BF,] results in 0 alkylation and formation of stable carbene complexes [Mn(q5-C6H,R1)(CO),-{C(OE)R2}] ( E = SiMe,, M e or Et).

Unusual migration of manganese to an arene via protonation of an agostic η3:CH-cyclohexenyl complex

“…Protonation of Cyclohexenyl Agostic Managanese Complexes.-The addition of a slight excess of tetrafluoroboric aciddiethyl ether complex to l a in dichloromethane leads to protonation of the cyclohexenyl ring and migration of the metal to the phenyl substituent at C (5). The product, tricarbonylC(1-6-q)-(cyclohex-3-enyl)benzene]manganese(1) tetrafluoroborate 2, was isolated as a pale yellow solid in 88% yield [equation (l)].…”

Reactions of [Mn(CO)3{η5-C5H4[( η5-C6H6)Mn(CO)3]}] and [WMe(CO)3{η5-C5H4[( η5-C6H6)Mn(CO)3]}] with aryllithium reagents

“…To compare the reactivity, we treated [Mn(η 5 -C 5 H 5 )(CO) 3 ] 26 with aryllithium reagents at 0-5 ЊC to afford the same manganese carbene complexes as reported. 27 It was also reported by Sheridan et al 28 that tricarbonyl(η 5 -cyclohexadienyl)manganese reacted with aryllithium at Ϫ50 ЊC to produce the manganese carbene complex. The difference between the temperatures at which tricarbonyl(η 5 -cyclopentadienyl)-and tricarbonyl(η 5 -cyclohexadienyl)-manganese react with the aryllithiums shows that the reactivities of the two kinds of olefinco-ordinated Mn(CO) 3 in 1 are different.…”

Manganese Hydrocarbon Complexes Excluding Cyclopentadienyl

“…80% yield, 2:1 mixture of (36): (37) Reaction of neutral tricarbonyl(r| 5 -dienyl)manganese complexes with nucleophiles also has been examined, with a variety of results. Reaction of organolithium reagents with (rj 5 -cyclohexadienyl)-manganese complexes (2) at 25 °C in diethyl ether produces acyl manganese species (38), via attack at carbon monoxide.…”

“…Protonation of this anion at -78 °C induces migration of the former nucleophile to the endo face of the rc-complex, generating a mixture of fluxional (r\ 3 -cyclohexenyl)manganese complexes (39), (40), and (41), containing agostic hydrogen interactions (Scheme 4). 37 Reaction o f phenyllithium with (t| 5 …”