Versatile Routes to Mono- and Bis(alkynyl) Manganese(II) and Manganese(III) Complexes via Manganocenes

Unseld, Dieter; Krivykh, V. V.; Heinze, Katja; Wild, Ferdinand R. W. P.; Artus, Georg R. J.; Schmalle, Helmut W.; Berke, Heinz

doi:10.1021/om9810549

Cited by 64 publications

(78 citation statements)

References 90 publications

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“…[63] A related carbon±-carbon coupling was observed in the studies of our group using the [Mn(MeC 5 H 4 )(dmpe)(CCPh)] complex. [48] A related coupling process was considered using as starting components…”

Section: Synthesis Of Asymmetric Trans-bis-alkynylmentioning

confidence: 99%

Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

Fernández

Venkatesan

Blacque

et al. 2003

Chemistry A European J

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The symmetric d(5) trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)] (R = Me, 1 a; Et, 1 b; Ph, 1 c) (dmpe = 1,2-bis(dimethylphosphino)ethane) have been prepared by the reaction of [Mn(dmpe)(2)Br(2)] with two equivalents of the corresponding acetylide LiC triple bond CSiR(3). The reactions of species 1 with [Cp(2)Fe][PF(6)] yield the corresponding d(4) complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)][PF(6)] (R = Me, 2 a; Et, 2 b; Ph, 2 c). These complexes react with NBu(4)F (TBAF) at -10 degrees C to give the desilylated parent acetylide compound [Mn(dmpe)(2)(C triple bond CH)(2)][PF(6)] (6), which is stable only in solution at below 0 degrees C. The asymmetrically substituted trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(C triple bond CH)][PF(6)] (R = Me, 7 a; Et, 7 b) related to 6 have been prepared by the reaction of the vinylidene compounds [Mn(dmpe)(2)(C triple bond CSiR(3))(C=CH(2))] (R = Me, 5 a; Et, 5 b) with two equivalents of [Cp(2)Fe][PF(6)] and one equivalent of quinuclidine. The conversion of [Mn(C(5)H(4)Me)(dmpe)I] with Me(3)SiC triple bond CSnMe(3) and dmpe afforded the trans-iodide-alkynyl d(5) complex [Mn(dmpe)(2)(C triple bond CSiMe(3))I] (9). Complex 9 proved to be unstable with regard to ligand disproportionation reactions and could therefore not be oxidized to a unique Mn(III) product, which prevented its further use in acetylide coupling reactions. Compounds 2 react at room temperature with one equivalent of TBAF to form the mixed-valent species [[Mn(dmpe)(2)(C triple bond CH)](2)(micro-C(4))][PF(6)] (11) by C-C coupling of [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] radicals generated by deprotonation of 6. In a similar way, the mixed-valent complex [[Mn(dmpe)(2)(C triple bond CSiMe(3))](2)(micro-C(4))][PF(6)] [12](+) is obtained by the reaction of 7 a with one equivalent of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The relatively long-lived radical intermediate [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] could be trapped as the Mn(I) complex [Mn(dmpe)(2)(C triple bond CH)(triple bond C-CO(2))] (14) by addition of an excess of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to the reaction mixtures of species 2 and TBAF. The neutral dinuclear Mn(II)/Mn(II) compounds [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))] (R = H, 11; R = SiMe(3), 12) are produced by the reduction of [11](+) and [12](+), respectively, with [FeCp(C(6)Me(6))]. [11](+) and [12](+) can also be oxidized with [Cp(2)Fe][PF(6)] to produce the dicationic Mn(III)/Mn(III) species [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))][PF(6)](2) (R = H, [11](2+); R = SiMe(3), [12](2+)). Both redox processes are fully reversible. The dinuclear compounds have been characterized by NMR, IR, UV/Vis, and Raman spectroscopies, CV, and magnetic susceptibilities, as well as elemental analyses. X-ray diffraction studies have been performed on complexes 4 b, 7 b, 9, [12](+), [12](2+), and 14.

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Section: Synthesis Of Asymmetric Trans-bis-alkynylmentioning

confidence: 99%

Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

Fernández

Venkatesan

Blacque

et al. 2003

Chemistry A European J

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“…2ϩ (∆G ϶ ϭ 56.7 kJ/mol), [30] and the cycloheptatrienylmolybdenum complex [(η 7 -C 7 H 7 )(dppe)MoϭCϭ CH 2 ] ϩ (dppe ϭ Ph 2 PC 2 H 4 PPh 2 ; ∆G ϶ ϭ 51.9 kJ/mol). [31] The highest activation energy for vinylidene rotation of which we are aware has been observed for the rhenium com-…”

Section: Synthesis Molecular Structures and Spectroscopic Propertiesmentioning

confidence: 99%

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

et al. 2003

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, L 2 = 2 PPh 3 or 1,1Ј-bis(diphenylphosphanyl)ferrocene (dppf), R = Ph or ferrocenyl] and their spectroscopic and electrochemical characteristics. Three of these compounds possess redox-active, ferrocenebased substituents or ligands − that are oxidized at lower potentials than the ruthenium center itself − attached either to the terminal carbon atom of the allenylidene ligand or to the ruthenium atom. The Fc/Ph-substituted complexes 3a and 3b provide unique examples of hindered rotation of the allenylidene substituent around the M=C bond. For 3a (L 2 = 2 PPh 3 ), two isomers differing in the orientation of the vertically aligned, unsymmetrically substituted allenylidene ligand are discernible even at 388 K. The dppf-substituted congener 3b has the allenylidene ligand in a horizontal orientation and exhibits a rotational barrier, as determined by dynamic 31 P NMR spectroscopy, of ∆G ϶ = 47 kJ/mol at T C = 238 K. The changes in the spectroscopic and electrochemical properties upon replacement of the PPh 3 by a dppf ligand and the Ph by an Fc moiety can be explained in terms of the bonding within these systems. These effects are attenuated when the ferrocene-based redox tags are oxidized, as shown by IR and

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“…A similar scheme was also reported for (Z 5 -C 5 H 4 Me)(dmpe)Mn=C=CHPh. 5 In this paper we report on the oxidative dehydrodimerization of manganese vinylidene complexes (Z 5 -…”

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confidence: 99%

Oxidative dehydrodimerization of manganese vinylidene complexes (η⁵‐C₅R₅)(CO)(L)MnCCHPh (R = Me, L = CO; R = H, L = PPh₃)

Novikova

Peterleitner

Sevumyan

et al. 2002

Applied Organom Chemis

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The oxidative dehydrodimerization of the phenylvinylidene manganese complexes (Z 5 -C 5 R 5 )(CO)(L)Mn=C=CHPh (5: R=Me, L=CO; 6: R=H, L=PPh 3 ) into the corresponding bisvinylidene compounds (Z 5 -C 5 R 5 )(CO)(L)Mn=C=CPhÐCPh=C=Mn(CO)(L)(Z 5 -C 5 R 5 ) (7: R=Me, L=CO; 8: R=H, L=PPh 3 ) was studied by cyclic voltammetry and chemical experiments. It was found that dehydrodimerization of 5 and 6 proceeds via direct C (b) ÐC (b) In this paper we report on the oxidative dehydrodimerization of manganese vinylidene complexes (Z 5 -C 5 R 5 )(CO)(L)Mn=C=CHPh (5: R=Me, L=CO; 6: R=H, L=PPh 3 ). Despite 5 and 6 having a close similarity to 1, their dehydrodimerization proceeds according to a different scheme, as will be shown below. (7) was carried out using a procedure similar to that for 1, 9 i.e. 5 was oxidized by AgBF 4 in dichloromethane at À40°C, the solution was kept at this temperature for 2 h and finally reduced by (Z-C 6 H 6 ) 2 Cr. The target complex 7 was obtained in 40% yield and characterized by 1 H and 13 C NMR spectroscopy as well as by mass spectrometry. We found that the yield of 7 can be increased to 85±90% if either potassium t-butylate or triethylamine is used in the final reaction step. In order to determine the mechanism of the dehydrodimerization process, we studied the electrochemical behavior of complexes 5 and 7 by cyclic voltammetry in CH 2 Cl 2 solution (see Table 1).Complex 7 displays two one-electron reversible oxidation waves at 0.17 V (peak A) and 0.58 V (peak B) (see Fig. 1). Complex 5 oxidizes irreversibly at 0.77 V (see Fig. 2, peak C). The reverse scanning of potentials revealed new cathodic peaks at 0.67 V and 0.27 V (peaks D and E respectively). These peaks do not coincide with the reduction peaks A', B' of 7 .Thus, 7 is not an initial product of transformation of 5 Á ,i.e. dehydrodimerization of 5 proceeds by a different mechanism than that for complex 1 (Scheme 1). We believe Scheme 1.Scheme 2. Figure 1. CV of bis-vinylidene complex 7 at 20°C. ). In order to confirm the validity of the mechanism shown in Scheme 3, we studied the oxidative dehydrodimerization of the triphenylphosphine-substituted phenylvinylidene complex (Z 5 -C 5 H 5 )(CO)(PPh 3 )Mn=C=CHPh (6), since we expected the product of direct C (b) ÐC (b) that the isomers differ in the orientation of the phenyl group relative to the cyclopentadienyl ring. Oxidative dehydrodimerization of 6 was carried out under the same conditions as the analogous processes for 1 and 5. The bis-vinylidene complex 8 proved to be rather unstable, and was obtained in 20% yield. Its structure was confirmed by IR-, NMR 1 H, and 31 P spectroscopy and mass spectroscopy. According to the NMR spectra, complex 8 exists as a mixture of two diastereomers in 3:1 ratio.Electrochemical oxidation of 6 and 8 was studied by cyclic voltammetry (CV) in dichloromethane solution. The cyclic voltammogram of the bis-vinylidene complex 8 showed two reversible one-electron oxidation peaks at 0.19 V and 0.61 V (Fig. 3, peaks F and G respectively). The cyclic voltam...

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Versatile Routes to Mono- and Bis(alkynyl) Manganese(II) and Manganese(III) Complexes via Manganocenes

Cited by 64 publications

References 90 publications

Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

Oxidative dehydrodimerization of manganese vinylidene complexes (η⁵‐C₅R₅)(CO)(L)MnCCHPh (R = Me, L = CO; R = H, L = PPh₃)

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Versatile Routes to Mono- and Bis(alkynyl) Manganese(II) and Manganese(III) Complexes via Manganocenes

Cited by 64 publications

References 90 publications

Generation and Coupling of [Mn(dmpe)2(CCR)(CC)]. Radicals Producing Redox‐Active C4‐Bridged Rigid‐Rod Complexes

Generation and Coupling of [Mn(dmpe)2(CCR)(CC)]. Radicals Producing Redox‐Active C4‐Bridged Rigid‐Rod Complexes

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

Oxidative dehydrodimerization of manganese vinylidene complexes (η5‐C5R5)(CO)(L)MnCCHPh (R = Me, L = CO; R = H, L = PPh3)

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Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

Generation and Coupling of [Mn(dmpe)₂(CCR)(CC)]^. Radicals Producing Redox‐Active C₄‐Bridged Rigid‐Rod Complexes

Oxidative dehydrodimerization of manganese vinylidene complexes (η⁵‐C₅R₅)(CO)(L)MnCCHPh (R = Me, L = CO; R = H, L = PPh₃)