John B. Sheridan

Synthesis and electrophilic reactivity of dicarbonylnitrosyl(cyclohexadienyl)manganese cations: double nucleophilic addition to coordinated arenes

Synthese des cations (cyclohexadienyl)Mn(CO)(NO)L + par traitement de (cyclohexadienyl)Mn(CO) 2 L (L=CO, PBu 3 ) avec NOPF 6 . Mecanisme des reactions de ces cations avec les nucleophiles

A metal mediated [6 + 3] cycloaddition reaction. Coupling of azirines and cycloheptatriene.

Abstract UV irradiation of tricarbonyl(cycloheptatriene)chromium(0) and 2-phenyl-1-azirines through pyrex at 0° C leads to 7-aza-8-phenylbicyclo[4.3.1]deca-2,4,7-trienes via a [6 + 3] cycloaddition of the azirine to the cycloheptatriene ring.

Reduction–oxidation properties of organotransition-metal complexes. Part 24. The oxidative dimerisation of [Ru(CO)2L(η4-cot)](L = CO or PPh3, cot = cyclo-octatetraene)

Electrochemical studies show that [Ru(CO)2L(η4-cot)](1, L = CO or PPh3, cot = cyclo-octatetraene) undergoes a diffusion-controlled, but irreversible, one-electron oxidation at a platinum-bead electrode in CH2Cl2. The reaction of [Fe(η-C5H5)2][PF6] with (1, L = PPh3) in CH2Cl2 gives [Ru2(CO)4(PPh3)2(η2,η3: η′2,η′3-C16H16)][PF4]2via the C–C bond coupling of the radical cation [Ru(CO)2(PPh3)(C8H8)]+.

Reduction–oxidation properties of organotransition-metal complexes. Part 21. Synthesis and X-ray structural characterisation of the redox-related pair of cyclohexadienyl complexes [Mn(CO)(dppe)(η5-C6H6Ph)] and [Mn(CO)(dppe)(η5-C6H6Ph)][PF6]·0.5CH2Cl2

The cyclohexadienyl complexes [Mn(CO)3–nLn(η5-C6H6Ph)][la, n= 1, L = PPh3; 1b, n= 2, L2= Ph2PCH2CH2PPh2(dppe)], prepared by U.V. photolysis of [Mn(CO)3(ηC6H6Ph)] and L, undergo reversible one-electron oxidation at a platinum electrode in CH2Cl2. The paramagnetic salt [Mn(CO)(dppe)(η-5C6H6Ph)][PF6](2) is isolable from the reaction between (1b) and [Fe(η-C5H5)2][PF6]. X-Ray structural studies on (1b) and (2)·0.5CH2Cl2 show the most pronounced effects of oxidation to be on the mean Mn–P distances which change from 2.221 A in (1b) to 2.338 A in (2). The effect on the conformation of the Mn(CO)(dppe) unit relative to the cyclohexadienyl moiety is small; in both complexes the CO ligand lies beneath the saturated ring carbon, giving approximate Cs symmetry to (1b) and (2). The structural consequences of one-electron oxidation on the geometry about the metal and within the ligands are discussed with regard to the nature of the highest occupied molecular orbital of (1b) and its depopulation in (2).

Allylic alkylation of complexed cyclo-octatetraene (cot)via the reaction of [Fe{P(OMe)3}(NO)2(η3-allyl)]+ with [M(CO)3(η4-cot)](M = Fe or Ru) derivatives; X-ray structure of [Ru(CO)2(PPh3)(η2,η3-C8H8R)][PF6]·0.5CH2Cl2[R = CH2C(Me)CH2]

The reaction of [Fe{P(OMe)3}(NO)2(η3-allyl)][PF6][1; allyl = CH2CHCH2 or CH2C(Me)CH2] with [Ru(CO)2L(η4-cot)](L = CO or PPh3, cot = cyclo-octatetraene) gives [Ru(CO)2L(η2,η3-C8H8R)][PF6][2; R = CH2CHCH2 or CH2C(Me)CH2] whereas that of (1; allyl = CH2CHCHMe) yields [2; R = CH(Me)CHCH2], as a mixture of two diastereomers, and (2; R = CH2CHCHMe). The X-ray structure of [2; R = CH2C(Me)CH2] shows that the addition of the 2-methylallyl group to the C8 ring yields the exo isomer, and confirms that the resulting cyclo-octatrienyl ligand is η2,η3-co-ordinated to ruthenium. The η2-alkene unit is trans to the PPh3 ligand, and the η3-allyl moiety is transoid to the two carbonyl ligands. Complex (1) and [Fe(CO)2(CNBut)(η4-cot)] give [Fe(CO)2(CNBut)(η5-C8H8R)][PF6] as a mixture of cyclo-octatrienyl (3) and bicyclo[5.1.0]octadienyl (4) isomers, the former showing rotamerism of the Fe(CO)2(CNBut) group with respect to the η5-bound hydrocarbon; diastereomerism is observed for [3; R = CH(Me)CHCH2]. The cationic iron and ruthenium complexes (2)–(4) are deprotonated by NEt3 in CH2Cl2 to give the allyl-substituted cot complexes [M(CO)2L(η4-C8H7R)][5; M = Fe, L = CNBut, R = CH2CHCH2, CH2C(Me)CH2, CH(Me)CHCH2, or CH2CHCHMe; M = Ru, L = PPh3, R = CH2C(Me)CH2] which undergo two dynamic processes in solution, namely rotamerism (M = Fe) and oscillation of the M(CO)2L unit with respect to the η4-bound hydrocarbon. The compounds [Fe(CO)2(CNBut)(η4-C8H7R)][R = CH2CHCH2orCH2C(Me)CH2] react sequentially with [1; R = CH2CHCH2 or CH2C(Me)CH2] and NEt3 to give the difunctionalised cyclo-octatetraene derivatives [Fe(CO)2(CNBut)(η4-C8H6R2)][6; R = CH2CHCH2 or CH2C(Me)CH2]. The substituted cyclo-octatetraenes C8H7[CH2C(Me)CH2] and C8H6[CH2C(Me)CH2]2 are detached from the appropriate iron complexes, (5) or (6), on reaction with ONMe3·2H2O.

Isolation and characterisation of a well defined precatalyst for the ring-opening polymerisation of silicon-bridged [1]ferrocenophanes

Reaction of the silicon-bridged [1]ferrocenophane [Fe(η-C 5 H 4 ) 2 SiMe 2 ] with [Pt(cod) 2 ] (cod = cycloocta-1,5-diene) yields a [2]platinasilaferrocenophane [Fe(η-C 5 H 4 ) 2 Pt(cod)SiMe 2 ] which functions as a precatalyst for the ring-opening polymerisation of the silicon-bridged [Fe(η-C 5 H 4 ) 2 SiMe 2 ] to yield the poly(ferrocenylsilane) [{Fe(η-C 5 H 4 ) 2 SiMe 2 } n ]; a key step in the mechanism is believed to involve dissociation of the cod ligand.

Reduction–oxidation properties of organotransition-metal complexes. Part 22. Stereospecific oxidative cyclopropane ring opening and reductive cyclobutane ring formation in polycyclic hydrocarbon complexes of iron; X-ray crystal structures of [Fe2(CO)6(η5:η′5-C16H16)][PF6]2·CH3NO2 and [Fe2(CO)6(η4:η′4-C16H16)]

Electrochemical studies show that [Fe2(CO)6(η4:η′4-C16H16)](2) undergoes irreversible two-electron oxidation at a platinum electrode in CH2Cl2. Chemical oxidation with [Fe(η-C5H5)2][PF6] gives [Fe2(CO)6(η5:η′5-C16H16)][PF6]2(3), X-ray structural studies on the nitromethane solvate of which reveal the detailed stereochemistry of the polycyclic hydrocarbon ligand. Two cycloheptadienyl moieties, each η5-bonded to Fe(CO)3 units, are fused to a central cyclohexene ring at C(2)–C(3) and at C(2′)–C(3′). The six-membered ring adopts a very flattened chair conformation with C(4) and C(4′)(bonded to iron as terminal members of pentadienyl units) in pseudo-axial sites, at 3.78 A apart. Complex (3) is reduced by K[BH(CHMeEt)3] to [Fe2(CO)6(η4:η′4-C16H16)](4), X-ray structural studies on which show stereospecific cyclobutane ring formation via the linking of atoms C(4) and C(4′) of (3). This linking is accompanied by ring inversion of the cyclohexene residue and by significant twisting of the ring double bond [C(2)–C(1)–C(1′)–C(2′) torsion angle –8.6(5)°]. The C(4)–C(4′) bond formed is the longest in the cyclobutane ring at 1.596(4)A[cf. others, average 1.548(3)A]. The ring inversion is required to bring C(4) and C(4′) into adjacent pseudo-equatorial sites and hence proximity [the C(4)–C(3)–C(3′)–C(4′) torsion angle is 159.7(4)° in (3) and 25.2(2)° in (4)]. Complex (4) is oxidised by [Fe(η-C5H5)2][PF6] to (3) which reacts with PPh3 and with iodide ion to give [Fe2(CO)6{η4:η′4-C16H16(PPh3)2}][PF6]2(5) and [Fe2l2(CO)4(η5:η′5-C16H16)](6), respectively.

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

Treatment of the agostic compound [Mn(η3:CH-C6H8Ph)(CO)3]1a with HBF4·Et2O in CH2Cl2 gave the arene complex [Mn{η6-C6H5(C6H9)}(CO)3][BF4]2via migration of the metal from the cyclohexenyl ring to the aryl substituent. Reaction of 2 with the nucleophiles triphenylphosphine and methylmagnesium chloride respectively gave the substitution product [Mn{η6-C6H5(C6H9)}(CO)2(PPh3)][BF4]3 and the addition product [Mn{η5-C6H5Me(C6H9)}(CO)3]4 as a mixture of isomers. The crystal structure of complex 2 has been determined: triclinic, space group P, a= 9.399(3), b= 10.644(2), c= 8.979(1)A, α= 93.03(1), β= 116.39(2), γ= 79.45(3)°, R= 0.057 for 1316 independent reflections.

Synthesis and reactions of acyl(cyclohexadienyl)manganates

The cyclohexadienyl complexes [Mn(η5-C6H6R1)(CO)3]1(R1=exo-H, Me or C6H4Me-4) react with LiR2(R2= Me or Ph) to give acylmetalates [Li(OEt2)][Mn(η5-C6H6R1)(CO)2{C(O)R2}]2. Complex 2(R1= Me, R2= Ph) has been characterised by an X-ray crystallography study: orthorhombic, space group P212121, a= 9.113(2), b= 14.491(8), c= 32.803(9)A, R= 0.064 for 1458 independent reflections. Protonation of 2 with HBF4·Et2O induces an aryl- or alkyl-group transfer to the endo face of the cyclohexadienyl ring yielding the new agostic cyclohexenyl complexes [Mn(η3:CHC6H7R1R2)(CO)3]3. The cyclohexenyl ligands can be decomplexed from the metal via treatment of 3 with 1,2-bis-(diphenylphosphino)ethane (dppe) in tetrahydrofuran to afford mixtures of substituted cyclohexa-1,3-dienes and [MnH(CO)3(dppe)]. The acylmetalates 2 react with [NO][BF4] at –78 °C to give [Mn(η5-C6H6R1)(CO)(NO){C(O)R2}] which decompose at room temperature to form the trans-disubstituted acylcyclohexadienes C6H6R1[C(O)R2]. Reaction of 2 with electrophiles SiMe3Cl, [Me3O][BF4] or [Et3O][BF4] results in O alkylation and formation of stable carbene complexes [Mn(η5-C6H6R1)(CO)2{C(OE)R2}](E = SiMe3, Me or Et).

Synthesis and protonation of cyclohexadienyl manganese acylmetallates; alkyl and aryl group transfer from an acyl to a dienyl ligand

Reaction of the cyclohexadienyl complex [(η5-C6H7)Mn(CO)3](1) with RLi gives the acylmetallates [Li(OEt2)][(η5-C6H7)Mn(CO)2C{O}R](R = Me, Ph)(2a,b) in 80–90% isolated yield, which, following protonation with HBF4·Et2O, undergo aryl or alkyl group transfer to the cyclohexadienyl ring; the products are new cyclohexenyl complexes [(η3-C6H8R)Mn(CO)3](3a,b) that contain an agostic endo C–H bond and an endo R group.