O.I. Trifonova

Indenyl and flourenyl transition metal complexes : III. Some new reactions of flourenyl- and indenyl-metal tricarbonyl anions

Abstract Deprotonation of η 6 -flourenechromium tricarbonyl (III) with excess t-BuOK in THF at70°C yields [η 6 -C 13 H 9 Cr(CO) 3 ] − K + (Ia), which isomerizes to η 5 -C 13 H 9 Cr(CO) 3 Cr − K + (II) at temperatures above −20°C. [η 6 -C 13 H 9 Cr(CO) 3 ] − Li + (Ib) may be obtained in the solid state by treatment of III with BuLi in absolute ether followed by precipitation with n-hexane. Methylation of Ib and II with methyl iodide goes stereospecifically to give η 6 - exo - (IX) and η 6 -(9- endo -methylfuorene)chromium tricarbonyl (XII) from Ib and II, respectively. Acylation of Ia with CH 3 COCl yields the acetate of 9-acetylfluorenechromium tricarbonyl (VII) in its enol form. Treatment of III with excess t-BuOK and CH 3 I in THF at −30°C leads to the derivative (XI), which is fully methylated at C(9). Phenyldiazonium borofluoride, diphenyliodonium iodide, ferrocenium borofluoride, trimethylchlorostannane and triethylbromogermane react with η 5 -C 9 H 7 (CO) 3 M − K + in THF to give compounds of the η 5 -series: η 5 -C 9 H 7 (CO) 2 MN 2 C 6 H 5 (M  Cr, Mo, W), η 5 -C 9 H 7 (CO) 3 WC 6 H 5 , [η 5 -C 9 H 7 (CO) 3 M] 2 (M  Mo, W), η 5 -C 9 H 7 (CO) 3 MSnMe 3 (M  Cr, Mo, W) and η 5 -C 9 H 7 (CO) 3 MGeEt 3 (M  Cr, Mo, W), respectively.

Indenyl and fluorenyl transition metal complexes : VIII. Synthesis, structure and properties of metal carbonyl derivatives of azafluorenes, indole, carbazole and the corresponding anions

Abstract The interaction of indole, carbazole and aza-analogues of fluorene, 1-azafluorene (I), 2-azafluorene (II), 3-methyl-II (III), 3-azafluorene (IV), 4-azafluorene (V), 7-methyl-V (VI) and [2,3]benzo-V (VII) with Cr(CO)6 (diglyme/heptane, 140° C), and with (NH3)3Cr(CO)3 (boiling dioxan) and of II with [BrM(CO)5] [NEt4] (M  Cr, Mo, W) has been studied. In all cases II and IV form only N-donor complexes of the LCr(CO)5 type, and the other heterocycles: arene-chromium tricarbonyl derivatives coordinated to the benzene, and not the heterocyclic, ring. The interaction of I and III with (NH3)3Cr(CO)3 results in the formation of a mixture of both types of complexes, predominantly arene ones. Reactions with (NH3)3Cr(CO)3 give appreciably higher yields than similar processes involving Cr(CO)6. Deprotonation of arenechromium tricarbonyl compounds (THF, t-BuOK) leads to η6-anions which reversibly isomerize in the case of complexes Ill, V and VI into η5-anions. These are new examples of metallotropic tautomerism in which the metal “slips” between the rings along the plane of the aromatic ligand. In the case of η6-anions of complexes of indole, carbazole, I and VII no such isomerization takes place. Alkylation of η6-anions yields 9-exo-alkyl compounds. These are also the only substances that can be isolated from the alkylation of tautomeric mixtures of anions obtained from XI, XIII and XXIV.

Indenyl and fluorenyl transition metal complexes: XIII. Determination of geometric configuration of (9-substituted fluorenes)chromium tricarbonyl complexes by ASIS-effect in 1H NMR spectra☆

Abstract A method to determine the geometric configuration of chromium tricarbonyl complexes of 9-substituted fluorenes (η 6 -9-RC 13 H 9 )Cr(CO) 3 which allows one to distinguish between exo -isomers (IIIa–e) and endo -isomers (Va–e) is proposed; a, R = CH 3 ; b, R = CH 2 HC 6 H 5 , c, R = D; d, R = t-C 4 H 9 ; e, R = C 6 H 5 . This method is based on measuring chemical shifts induced in 1 H NMR spectra by aromatic solvents when passing from CDCl 3 to C 6 D 6 solutions (ASIS effect). The validity of the criterion is confirmed by X-ray analysis of IIIb. Exo -isomers, IIIb,c, were obtained by alkylation of the η 6 -fluorenylchromium tricarbonyl anion (I) with the corresponding halides RX in tetrahydrofuran (THF) at low temperature. Endo -isomers (Vb,c) have been obtained by alkylation of the η 6 -fluorenylchromium tricarbonyl anion (II) with subsequent thermal rearrangement of intermediate σ-organometal derivatives (IV) without their isolation. Endo -isomers, Vd,e, have been formed by stereoselective protonation of substituted complex anions [(η 6 -9-RC 13 H 8 )Cr(CO) 3 ] − .

Ricochet inter-ring haptotropic rearrangement of σ-methyl-(η5-indenyl) chromium tricarbonyls. Experimental kinetic and theoretical DFT study

Abstract σ -Methyl-( η 5 -indenyl) chromium tricarbonyl ( III ) rearranges quantitatively into η 6 -1-endo-methylindene) chromium tricarbonyl ( IV ) in C 6 D 6 solution at 30–60°C. Methyl group attachment to the positions 2 or 3 of indenyl ligand in ( III ) has no influence on the activation parameters of this ricochet inter-ring haptotropic rearrangement ( ΔG # =23.6 kcal mol −1 ; ΔH # =18.9±0.2 kcal mol −1 ; ΔS # =−18.6±0.2 cal K −1 mol −1 ). ( IV ) undergoes further irreversible isomerization at 60–120° into ( ν 6 -3-methylindene) chromium tricarbonyl ( V ) with a higher activation barrier ( ΔG # =28.5±0.1 kcal mol −1 ) via two consecutive [1,5]-sigmatropic hydrogen shifts. The mechanisms of both rearrangements have been studied in detail using density functional theory (DFT) calculations with extended basis sets. Calculations show that the rearrangement ( III ) → ( IV ) proceeds in two steps. Methyl group migration from chromium into position 1 of the indenyl ligand is the rate-determining step leading to the formation of the 16-electron intermediate ( VII ). The calculated activation barrier ( E a =19.6 kcal mol −1 ) is in good agreement with the experimental one. Further rearrangement ( VII ) → ( V ) proceeds via a trimethylenemethane-type transition state ( XVIII ) with an activation barrier 11.8 kcal mol −1 . The coordination of the chromium tricarbonyl group at the six-membered ring has only minor influence on the kinetic parameters of the hydrogen [1,5]-sigmatropic shift in indene.

Indenyl and fluorenyl transition metal complexes: X. Anionic chromium tricarbonyl complexes of fluoradene, substituted fluorenes and indene: The structure of ion pairs and η6 → η5 rearrangements

Abstract The metallotropic η 6 ⇌ η 5 tautomeric equilibrium in anionic chromium tricarbonyl complexes of fluoradene, substituted fluorenes and indene has been studied. A criterion is proposed for determining the ion-pair type in η 6 -anions according to the E -band splitting in the ν(CO) region of their IR spectra. The influence of ligand structure and cation solvation on K eq. is discussed.

Indenyl and fluorenyl transition metal complexes: XIV. Synthesis and reactions of chromium tricarbonyl complexes of 5,10-dihydroindeno[2,1-α]indene

Abstract 1-4,4a,10b-η 6 -5,10-dihydroindeno[2,1-α]indene chromium tricarbonyl (III) has been obtained by Rauschs method. Deprotonation of III by t-BuOK in THF solution, by potassium solution in HMPTA or by KH in THF at −65°C yields an η 6 -anion IV, which is irreversibly rearranged into η 5 -anion V at 20°C. Action of n-BuLi/t-BuOK mixture in THF at −65°C results in the formation of η 6 -dianion VI, which is irreversibly converted into η 5 -dianion VII above 0°C. Alkylation of IV with benzyl iodide yields 5- exo -benzyl(III). Reaction of V with benzyl iodide leads to the σ-benzyl derivative, which is isomerized into 5- endo -benzyl(III). The reaction of V with N -nitroso- N -methyltosylamide yields the η 5 -nitrosodicarbonyl complex of chromium (XI).

Synthesis and reactions of dicarbonyl (?2-indene)-?5-indenyl complexes of manganese and rhenium

Photochemical reactions of M(CO)3(η5-C9H7), where M=Mn (1) or Re (2), with indene have produced η2-indene complexes M(CO)2(η2-C9H8)(η5-C9H7), where M=Mn (3) or Re (4). Deprotonation of complex3 witht-BuOK in THF at −60 °C gives the anion [Mn(CO)2(η1-C9H7)(η5-C9H7)− (5), in which there occurs a rapid interchange of the Mn(CO)2(η5-C9H7) group between positions 1 and 3 in the η1-indenyl ligand. The reaction of complex4 with Ph3CPF6 in CH2Cl2 at 0 °C leads to the complex [Re(CO)2(η3-C9H7)(η5-C9H7)PF6, whereas the similar reaction of complex3 gives only decomposition products even at −20 °C.

Synthesis, structure, and rearrangements of new tricarbonylchromium complexes of substituted heptalenes

Reactions of 1,2,5,6,8,10-hexamethylheptalene (1) and its bond isomer, 1,4,5,6,8,10-hexamethylheptalene (2), with tricarbonylchromium complexes L{in3}Cr(CO){in3} (L=NH{in3} and Py) have been investigated. Thermodynamically less stable complex 1 exhibits higher reactivity with respect to Py{in3}Cr(CO){in3}/BF{in3} · Et{in2}O under the conditions of Öfeles reaction than complex2. At 10–30 °C, the Cr(CO){in3} group is coordinated to the asymmetrically substituted ring, which is accomplished by the shift of double bonds in the ligand, to afford tricarbonyl-[1,4,5,6,8,10-hexamethyl-η{su6}-(10a, 1–5)heptalene]-chromium (6) as the only mononuclear complex. Under more drastic conditions (Raushs reaction, 80 °C),1 ↔ 2 interconversion proceeds faster than the reaction of individual bond isomers with coordinatively unsaturated “hot” particles (solv){inn}Cr(CO){in3}. In this case, all of the four possible isomeric mononuclear complexes (6–9) and two binuclear complexes (10 and 11) are formed. The structures of complexes 6–11 have been studied by NMR and mass spectrometry, the structure of6 has been established by X-ray diffraction analysis. Heating a solution of6 in octane at 115 °C results in the isomerization of6 into complex7 through the intracycle 1,2-shift of the Cr(CO){in3} group and also in its conversion into complex8, which is the first example of interring η{su6}→η{su6}-haptotropic rearrangement in nonplanar seven-membered π-systems.

Mechanism of haptotropic rearrangements in the chromium tricarbonyl complexes of naphthalene and its analogs

Conclusions1.The haptotropic rearrangements in the chromium tricarbonyl complexes of 1-methylacenaphthene take place predominantly with retention of the stereochemistry, i.e., the exo-and endo-configuration of the interconverting complexes is preserved during the rearrangement.2.The mechanism of the rearrangements observed in the chromium tricarbonyl complexes of naphthene and its analogs was established. It involves intramolecular migration of the organometallic group betwen the six-membered rings.

Synthesis and reactions of chromium tricarbonyl complexes of 5,10-dihydroindeno[2,1-a]indene

Conclusions1.1-4,4a,10a-η6-5,10-Dihydroindeno[2,l-a]-indenechromium tricarbonyl was synthesized. Upon treatment with t-BuOK in THF at -65‡C the corresponding anion with the η6-structure was formed which irreversibly isomerized to the η5-form at 25‡C.2.The η6- and η5-anions react with benzyl iodide regio- and stereospecifically. In the case of the6-anion attack of the electrophile proceeds at the carbon atom in position 5 and the entering benzyl group takes the exo position. The η5-anion is attacked at the metal atom and subsequent ricochet haptotropic rearrangemnet leads to an arene complex with the endo-benzyl group in position 5.