DALTON J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 205 Reactions of [Mn(CO)3{Á5-C5H4[(Á5-C6H6)Mn(CO)3]}] and [WMe(CO)3{Á5-C5H4[(Á5-C6H6)Mn(CO)3]}] with aryllithium reagents Ronghua Li, Jiabi Chen,* Yong Yu and Jie Sun Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China The reactions of [Mn(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 1 and [WMe(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 2 with aryllithium reagents, LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4), in diethyl ether at low temperature afforded acylmetalate intermediates, which on alkylation with Et3OBF4 in aqueous solution at 0 8C gave alkoxycarbene complexes [Mn(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R]}] and [WMe(CO)3{h5- C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R]}].The structure of [Mn(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)C6H4- Me-o]}], established by X-ray diffraction, shows that the carbene ligand is attached to the manganese atom co-ordinated to the h5-cyclohexadienyl moiety.Olefin-co-ordinated transition-metal carbene complexes and/or their isomerized products have been examined extensively in our laboratory.1–17 Earlier we demonstrated 1–12 several novel isomerizations of olefin ligands, and a series of isomerized carbene complexes with novel structure were isolated by the reactions of olefin-ligated metal carbonyl compounds with nucleophiles. The isomerizations and reaction products depend not only on the olefin ligands but also on the central metals.3–5,8,12–15 For instance, tricarbonyl(cycloheptatriene)iron and tricarbonyl(norbornadiene)iron reacted with aryllithium reagents, and subsequent alkylation with Et3OBF4 gave novel ring-opened isomerized complexes (Scheme 1).3,4 However, the reactions of tricarbonyl(cycloheptatriene)-molybdenum and -chromium14 and tetracarbonyl(norbornadiene)-chromium, -molybdenum and -tungsten 13,14 with aryllithium reagents under the same conditions gave normal olefin-co-ordinated carbene complexes in which the diene ligand and carbene ligand coexist stably (Scheme 2).In our previous research the central metals were usually the Group VIIIB metals (d8) and Group VIB metals (d6). Continuing our interest in olefin-co-ordinated metal carbene and carbyne complexes, we turned our attention to olefinligated carbonyl compounds of Group VIIB metal (d7), such as tricarbonyl(exo-cyclopentadienyl-h5-cyclohexadienyl)manganese, 18 which gave a series of normal olefin-co-ordinated manganese carbene complexes in this reaction (Scheme 3).17 In order further to investigate the effect of different metal centre, on the isomerization of the olefin ligand and the reaction Scheme 1 (i) (a) LiC6H4Me-o, (b) Et3OBF4; (ii) (a) LiR (R = C6H4Meo, C6H4Me-p or C6H4CF3-p), (b) Et3OBF4 Fe CO OC CO Fe OC CO (i ) Me C OEt Fe(CO)2 OEt R Fe COCO D6/04436K/A1 (ii ) CO products, we chose [Mn(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 1 and [WMe(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 2, in which the two metal centres are not directly bonded to each other, as starting materials in reactions with aryllithium reagents.This paper describes a detailed study of these reactions and the structural characterization of the resulting products. Experimental All the procedures were performed under a dry, oxygen-free nitrogen atmosphere using standard Schlenk techniques. The solvents were reagent grade, dried by refluxing over appropriate drying agents and stored over 4 Å molecular sieves under a nitrogen atmosphere.Tetrahydrofuran (thf) and diethyl ether were distilled from sodium–benzophenone, light petroleum (b.p. 30–60 8C) from CaH2, and CH2Cl2 from P2O5. The neutral Scheme 2 (i) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-p or C6H4CF3-p), (b) Et3OBF4: (ii) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-m, C6H4Me-p, C6H4OMe-p or C6H4CF3-p), (b) Et3OBF4 M CO OC CO M CO OC C OEt R M OC CO OC OC M CO OC CO C OEt R D6/04436K/A2 M = Cr or Mo (i ) (ii ) M = Cr, Mo or W Scheme 3 (i) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-m, C6H4Me-p, C6H4OMe-p or C6H4CF3-p), (b) Et3OBF4 Mn CO OC CO Mn CO OC C OEt R D6/04436K/A3 Mn CO OC CO or (i)206 J.Chem. Soc., Dalton Trans., 1997, Pages 205–211 alumina used for chromatography was deoxygenated at room temperature under high vacuum for 16 h, deactivated with 5% w/w N2-saturated water, and stored under N2. Compounds 1,18 2,18 and 15,18 Et3OBF4,19 and aryllithium reagents 20–24 were prepared by literature methods.The IR spectra were measured on a Shimadzu IR-440 spectrophotometer, 1H NMR spectra on a Bruker AM-300 spectrometer at ambient temperature in (CD3)2CO solution with SiMe4 as the internal reference and electron ionization (EI) mass spectra on a Hewlett-Packard 5989A spectrometer. Melting points obtained on samples in sealed nitrogen-filled capillaries are uncorrected. Preparation [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Me-o]}] 3.To a solution of compound 1 (70 mg, 0.16 mmol) in diethyl ether (30 cm3) at 278 8C was added dropwise LiC6H4Me-o20 (0.38 mmol) in diethyl ether (10 cm3) with stirring. The light yellow solution was stirred initially at 278 to 265 8C for 0.5 h and then at 260 to 245 8C for 4 h, during which time it turned yellow to orange-red. The resulting solution was evaporated to dryness under vacuum at 250 to 240 8C. To the orange solid residue obtained was added Et3OBF4 (ca. 3 g). This solid mixture was dissolved in N2-saturated water (20 cm3) at 0 8C with vigorous stirring and the mixture covered with light petroleum. Immediately afterward, Et3OBF4 (ca. 8 g) was added portionwise with vigorous stirring to the aqueous solution until it became acidic. The aqueous solution was extracted with light petroleum. The combined extract was evaporated in vacuo, and the residue chromatographed on an alumina column (neutral, 100–200 mesh, 1.6 × 10–15 cm) at 220 8C with light petroleum followed by light petroleum–Et2O (10 : 1) as the eluent.The orange-yellow band was eluted and collected. Removal of the solvent under vacuum and recrystallization of the crude product from light petroleum–CH2Cl2 solution at 280 8C gave 64 mg (71%, based on 1) of orange-red crystals of compound 3, m.p. 118–119 8C (decomp.). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn(CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (MnC5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.9; H, 4.2. Calc.for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mem]}] 4. Similarly, compound 1 (200 mg, 0.48 mmol) dissolved in ether (50 cm3) was reacted with LiC6H4Me-m20 (1.06 mmol) at 265 to 245 8C for 4 h. Subsequent alkylation and further treatment as describved above gave 165 mg (64%, based on 1) of orange-red crystals of 4, m.p. 90–92 8C (decomp). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn(CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (MnC5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.7; H, 3.9. Calc. for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mep]}] 5.Similarly, compound 1 (150 mg, 0.36 mmol) was allowed to react with LiC6H4Me-p20 (0.80 mmol) at 265 to 245 8C for 4 h. Subsequent alkylation and further treatment as described above afforded 134 mg (70%, based on 1) of 5 as orange-red crystals, m.p. 58–60 8C (decomp.). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn- (CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (Mn- C5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.9; H, 3.55.Calc. for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)Ph]}] 6. The reaction of compound 1 (200 mg, 0.48 mmol) with LiPh21 (1.10 mmol) was carried out at 260 to 240 8C for 4 h. Subsequent alkylation and further treatment as described above yielded 150 mg (60%, based on 1) of 6 as orange-red crystals, m.p. 100– 102 8C (decomp.).Mas spectrum: m/z 526 (M+), 502 (M+ 2 CO), 470 (M+ 2 2CO), 426 (M+ 2 2CO 2 OC2H4), 398 (M+ 2 3CO 2 OC2H4), 386 (M+ 2 5CO), 370 (M+ 2 4CO 2 OC2H5), 342 (M+ 2 5CO 2 OC2H4), 330 [M+ 2 Mn(CO)3 2 2CO], 251 (MnC5H4C6H6Mn)+, 190 [MnCH(OC2H5)C6H5]+ and 135 [(C6H5)CH(OC2H5)]+ (Found: C, 56.95; H, 3.8. Calc. for C25H20Mn2O6: C, 57.05; H, 3.85%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4OMep]}] 7. A solution of p-MeOC6H4Br (80 mg, 0.34 mmol) in ether (20 cm3) was mixed with LiBun 22 (0.34 mmol).After 30 min of stirring at room temperature, the resulting ether solution of LiC6H4OMe-p 23 was allowed to react, as described above, with compound 1 (70 mg, 0.17 mmol) at 260 to 240 8C for 4 h, followed by alkylation; further treatment gave 65 mg (70%, based on 1) of orange-red crystalline 7 which is a viscous oil at room temperature. Mass spectrum: m/z 556 (M+), 500 (M+ 2 2CO), 456 (M+ 2 2CO 2 OC2H4), 428 (M+ 2 3CO 2 OC2H4), 416 (M+ 2 5CO), 400 (M+ 2 4CO 2 OC2H4), 372 (M+ 2 5CO 2 OC2H5), 360 [M+ 2 Mn(CO)3 2 2CO], 251 (MnC5H4C6H6Mn)+, 220 [MnCH(OC2H5)C6H4OCH3]+ and 165 [(CH3OC6H4)CH(OC2H5)]+ (Found: C, 53.2; H, 3.6.Calc. for C26H22Mn2O7?0.5CH2Cl2: C, 53.15; H, 3.85%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4CF3- p]}] 8. A solution of LiBun (0.38 mmol) in ether (10 cm3) was added dropwise to a solution of p-CF3C6H4Br (86 mg, 0.38 mmol) in ether (20 cm3). After 30 min of stirring at room temperature the resulting ether solution of LiC6H4CF3-p 24 was treated with compound 1 (80 mg, 0.19 mmol) in ether (40 cm3) at 260 to 240 8C for 4 h.Subsequent alkylation as above afforded 60 mg (53%, based on 1) of orange-red crystalline 8 which is a viscous oil at room temperature. Mass spectrum: m/z 594 (M+), 538 (M+ 2 2CO), 494 (M+ 2 2CO 2 OC2H4), 466 (M+ 2 3CO 2 OC2H4), 454 (M+ 2 5CO), 438 (M+ 2 4CO 2 OC2H4), 410 (M+ 2 5CO 2 OC2H5), 398 [M+ 2 Mn- (CO)3 ] 2CO], 258 [MnCH(OC2H5)C6H4CF3]+, 251 (MnC5H4- C6H6Mn)+ and 203 [(CF3C6H4)CH(OC2H5)]+ (Found: C, 52.8; H, 2.65.Calc. for C26H19F3Mn2O6: C, 52.55; H, 3.2%). [WMe(CO)3[Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Meo]}] 9. To a solution of compound 2 (200 mg, 0.36 mmol) in ether (50 cm3) at 270 8C was added dropwise LiC6H4Me-o (0.78 mmol) in ether (10 cm3) with stirring. The orange-yellow solution was stirred initially at 270 to 265 8C for 0.5 h and then at 265 to 250 8C for 4 h, during which time it turned orange-red to red.The resulting solution was evaporated under vacuum at 250 to 240 8C to dryness. Subsequent alkylation of the residue obtained with Et3OBF4 and further treatment as described above gave 65 mg (26%, based on 2) of orange-yellow crystals of 9 which is a viscous oil at room temperature. Mass spectrum: m/z 628 (M+ 2 2CO), 584 (M+ 2 3CO 2 CH3 2 H), 556 (M+ 2 4CO 2 CH3 2 H), 528 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+ and [(CH3C6H4)CH(OC2H5)]+ (Found: C, 43.7; H, 3.33.Calc. for C27H25MnO6W?CH2Cl2: C, 43.7; H, 3.55%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mem]}] 10. Similarly, compound 2 (100 mg, 0.18 mmol) wasJ. Chem. Soc., Dalton Trans., 1997, Pages 205–211 207 allowed to react with LiC6H4Me-m (0.39 mmol) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment as above afforded 35 mg (29%, based on 2) of 10 as orange-red crystals, m.p. 127–128 8C (decomp.). Mass spectrum: m/z 656 (M+ 2 CO), 600 (M+ 2 3CO), 480 [CH3(OC)3WC5H4C6H6- Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+ and 149 [(CH3C6H4)CH(OC2H5)]+. [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mep]}] 11. Similarly, compound 2 (200 mg, 0.36 mmol) dissolved in ether (50 cm3) was treated with LiC6H4Me-p (0.76 mmol) at 265 to 250 8C for 4 h, followed by alkylation; further treatment as described above yielded 70 mg (29%, based on 2) of orange-red crystalline 11 which is a red viscous oil at room temperature.Mass spectrum: m/z 628 (M+ 2 2CO), 584 (M+ 2 3CO 2 CH3 2 H), 556 (M+ 2 4CO 2 CH3 2 H), 528 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [Mn- CH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+, 149 [(CH3C6H4)- CH(OC2H5)]+ (Found: C, 45.6; H, 3.15. Calc. for C27H25Mn- O6W?0.5CH2Cl2: C, 45.45; H, 3.15%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)Ph]}] 12.The reaction of compound 2 (100 mg, 0.18 mmol) with LiPh (0.39 mmol) was carried out as described above at 265 to 250 8C for 4 h. After evaporation of the solvent in vacuo, further treatment of the resulting residue as described above gave 48 mg (40%, based on 2) of orange-red crystals of 12, m.p. 81– 83 8C (decomp.). Mass spectrum: m/z 614 (M+ 2 2CO), 570 (M+ 2 3CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 196 (C5H4C6H5Mn)+, 190 [MnCH(OC2H5)C6H5]+ and 135 [(C6H5)- CH(OC2H5)]+ (Found: C, 46.25; H, 3.6.Calc. for C26H23- MnO6W: C, 46.6; H, 3.45%). [WMe(CO)3{Á5-C5H4[Á5-C6H6)(OC)2Mn]] C(OEt)C6H4OMep]}] 13. Compound 2 (120 mg, 0.22 mmol) was treated as described above, with fresh LiC6H4OMe-p prepared by the reaction of p-MeOC6H4Br (90 mg, 0.48 mmol) with LiBun (0.48 mmol), in ether solution (50 cm3) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment yielded 44 mg (30%, based on 2) of orange-red crystals of 13 which is a viscous oil at room temperature.Mass spectrum: m/z 644 (M+ 2 2CO), 602 (M+ 2 3CO 2 CH3 2 H), 572 (M+ 2 4CO 2 CH3 2 H), 544 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3- WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4- C6H5Mn)+, 220 [MnCH(OC2H5)C6H4OCH3]+, 196 (C5H4C6H5- Mn)+ and [(CH3OC6H4)CH(OC2H5)]+ (Found: C, 46.8; H, 3.4. Calc. for C27H25MnO7W: C, 46.3; H, 3.6%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4CF3- p]}] 14.Similarly compound 2 (100 mg, 0.18 mmol) was treated with fresh LiC6H4CF3-p prepared by the reaction of p-CF3C6H4Br (90 mg, 0.40 mmol) with LiBun (0.40 mmol) in ether solution (50 cm3) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment as described above yielded 65 mg (45%, based on 2) of 14 as orange-red crystals, m.p. 70– 72 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 638 (M+ 2 3CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 258 [MnCH(OC2H5)C6H4CF3]+, 203 [(CF3C6H4)CH(OC2H5)]+ and 196 (C5H4C6H5Mn)+ (Found: C, 41.1; H, 2.75.Calc. for C27H22F3MnO6W?CH2Cl2: C, 40.85; H, 2.95%). [(OC)3Mn{(Á5-C6H6)(Á5-C5H4)Fe(Á5-C5H4)(Á5-C6H6)}Mn- (CO)2{]] C(OEt)C6H4Me-o}] 16. The compound [(OC)3Mn{(h5- C6H6)(h5-C5H4)Fe(h5-C5H4)(h5-C6H6)}Mn(CO)3] 15 18 (100 mg, 0.16 mmol) was dissolved in ether (30 cm3) at 270 8C. To this solution was added dropwise LiC6H4Me-o (0.33 mmol) with stirring. The light yellow solution was stirred initially at 270 to 255 8C for 0.5 h and then at 255 to 235 8C for 4 h, during which time it turned yellow and a yellow precipitate separated.After evaporation of the solution to dryness in vacuo, the residue was subsequently alkylated with Et3OBF4 and further treated as described above to give 50 mg (44%, based on 15) of yellow crystals of 16, m.p. 42–44 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 626 (M+ 2 4CO), 618 (M+ 2 C2H5 2 CH3C6H4), 534 (M+ 2 3CO 2 C2H5 2 CH3C6H4), 450 [(MnC6- H6C5H4)2Fe]+, 395 [Mn(C6H6C5H4)2Fe]+, 338 [(C6H5C5H4)2Fe]+, 196 (MnC6H5C5H4)+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 59.75; H, 4.3.Calc. for C37H32FeMn2O: C, 60.2; H, 4.35%). [(OC)3Mn{(Á5-C6H6)(Á5-C5H4)Fe(Á5-C5H4)(Á5-C6H6)}Mn- (CO)2{=C(OEt)C6H4Me-p}] 17. Similarly, compound 15 (200 mg, 0.32 mmol) dissolved in ether (40 cm3) was treated with LiC6H4Me-p (0.65 mmol) at 255 to 235 8C for 4 h. Subsequent alkylation and further treatment as described above afforded 70 mg (31%, based on 15) of orange crystalline 17, m.p. 68–70 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 638 (M+ 2 2CO 2 OC2H4), 626 (M+ 2 4CO), 618 (M+ 2 C2H5 2 CH3C6H4), 588 (M+ 2 COC2H5 2 CH3C6H4 2 2H), 534 (M+ 2 3CO 2 C2H5 2 CH3C6H4), 450 [(MnC6H6C5H4)2Fe]+, 395 [Mn- (C6H6C5H4)2Fe]+, 338 [(C6H5C5H4)2Fe]+, 252 [MnC6H5C5- H4Fe]+, 196 (MnC6H5C5H4)+ and 149 [(CH3C6H4)CH- (OC2H5)]+ (Found: C, 60.35; H, 4.25. Calc. for C37H32FeMn2- O6: C, 60.2; H, 4.35%).Crystallography Single crystals of complex 3 suitable for X-ray diffraction study were obtained by recrystallization from light petroleum– CH2Cl2 solution at 280 8C. A crystal of approximate dimensions 0.20 × 0.20 × 0.40 mm was sealed in a capillary under a nitrogen atmosphere. Intensity data for 4152 independent reflections, of which 2516 had I > 3s(I), were collected with a Rigaku AFC7R diffractometer at 20 8C using Mo-Ka radiation (l 0.710 69 Å) with w–2q scan mode in the range 5 < 2q < 508.The intensity data were corrected for Lorentz-polarization effects and an empirical absorption correction based on azimuthal scans of several reflections was applied which resulted in transmission factors ranging from 0.636 to 1.000. The structure was solved and expanded by Fourier techniques. The non-hydrogen atoms were refined anisotropically. The hydrogen atoms were included but not refined. The final cycle of full-matrix least-squares refinement was based on 2516 observed reflections and 308 variable parameters and converged (largest parameter was 0.06 times its e.s.d.).The standard deviation of an observation of unit weight was 1.74. The weighting scheme was based on counting statistics and included a factor (p = 0.030) to downweight the intense reflections. The maximum and minimum peaks on the final Fourier-difference map corresponded to 0.45 and 20.53 e Å23, respectively. All calculations were performed using the TEXSAN crystallographic software package.25 Details of the crystallographic data and the procedures used for data collection and reduction are given in Table 3.Atomic coordinates, thermal parameters, and bond lengths and angles have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Instructions for Authors, J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 186/288. Results and Discussion Compound 1 was treated with 2 molar equivalents of aryllithium reagents LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4) in ether at 265 to 245 8C for 4 h.The acylmetalate intermediates formed were subsequently alkylated208 J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 with Et3OBF4 in aqueous solution at 0 8C. After removal of the solvent under high vacuum at low temperature, chromatography of the solid residue on an alumina column at 220 8C, and recrystallization from light petroleum–CH2Cl2 solution at 280 8C, orange-red crystalline complexes 3–8 were obtained with the composition [(OC)3Mn{h5-C5H4[(h5-C6H6)(OC)2- Mn]] C(OEt)R]}] (Scheme 4) in 53–71% yields. The complexes are soluble in polar organic solvents but only slightly soluble in non-polar solvents.They are sensitive to air and temperature in solution but fairly stable in the crystalline state. They are formulated as cyclohexadienyl-co-ordinated manganese carbene complexes on the basis of their elemental analyses and spectroscopic studies and a single-crystal X-ray diffraction study of 3.There are two olefin-co-ordinated Mn(CO)3 units in complex 1. However, neither dicarbene complexes nor cyclopentadienylco- ordinated carbene complexes were obtained in the reactions, only products 3–8, even though more than 2 molar equivalents of aryllithium reagents were used. This might be ascribed to the different carbonyls of the two kinds of Mn(CO)3 in 1.To compare the reactivity, we treated [Mn(h5-C5H5)(CO)3] 26 with aryllithium reagents at 0–5 8C to afford the same manganese carbene complexes as reported.27 It was also reported by Sheridan et al.28 that tricarbonyl(h5-cyclohexadienyl)manganese reacted with aryllithium at 250 8C to produce the manganese carbene complex. The difference between the temperatures at which tricarbonyl(h5-cyclopentadienyl)- and Scheme 4 (i) 2LiR, Et2O, 265 to 245 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO M CO OC n C O–Li+ R 1 D6/04436K/A4 (OC)3Mn (OC)3Mn M CO OC (ii ) (i ) (OC)3Mn n C OEt R a b c d e f f e b c 3 o –MeC6H4 4 m–MeC6H4 5 p –MeC6H4 6 Ph 7 p –MeOC6H4 8 p –CF3C6H4 R Table 1 Infrared specta of complexes 1–17 in hexane in the n(CO) region Complex n& (CO)/cm21 1 18 2 18 3456789 10 11 12 13 14 15 18 16 17 2020s, 1960s, 1954s 2020s, 1994w, 1966s, 1958s, 1940w, 1935s 2000s, 1961s, 1947s, 1908m 2000s, 1957s, 1943s, 1900m 2002s, 1960s, 1948s, 1900m 2001s. 1958s, 1950s, 1902m 2002s, 1961s, 1952s, 1900m 2000s, 1960s, 1945s, 1910m 2010s, 1964s, 1953m, 1932vs, 1910w 2000s, 1960s, 1953s, 1931vs, 1900w 2000s, 1960s, 1953s, 1932vs, 1900w 2000s, 1960s, 1956m, 1934vs, 1905s 2000s, 1960s, 1955s, 1932vs, 1900m 2000s, 1962s, 1954s, 1933vs, 1911w 2000s, 1950vs 2025s, 1959vs, 1950s, 1905m 2020s, 1957vs, 1950s, 1898m tricarbonyl(h5-cyclohexadienyl)-manganese react with the aryllithiums shows that the reactivities of the two kinds of olefinco- ordinated Mn(CO)3 in 1 are different.However, when 1 was treated with aryllithium reagents either at 0–5 8C or while the temperature was allowed to rise slowly from 265 to 0–5 8C only cyclohexadienyl-co-ordinated products 3–8 were obtained, not the expected cyclopentadienyl-co-ordinated manganese carbene complexes. The carbene formation at the less-electron-rich centre is predictable because cyclopentadienyl is a better donor than cyclohexadienyl. The IR spectra (Table 1) and the solution 1H NMR spectra (Table 2), as well as the mass spectra, of complexes 3–8 are consistent with the proposed structure. In the 1H NMR spectra resonances at d 5.20–3.30 and 1.60–1.40 are attributed to the ethoxy group and at d 7.80–6.80 to the aryl group, in addition to the expected proton signals of the cyclopentadienyl and cyclohexadienyl groups. As compared with the starting material 1, the chemical shift of Ha moved upfield and that of Hd changed a little, while use of Hb and Hc remained almost constant in 3–8, indicating that the extent of back donation of d electrons from Mn to the p* orbital of the co-ordinated cyclohexadienyl increased only a little, upon formation of the carbene ligand.The difference between the chemical shifts of the cyclohexadienyl protons might be ascribed to the different distant shielding from the p electrons of the Ha, Hb, Hc and Hd protons, as shown for tricarbonyl(h5-cyclohexadienyl)- manganese by Winkhaus et al.29 The structural data for 3 show that Ha lies in the shielding area of the aryl ring.So we prefer to consider that the greatest influence on d(Ha) comes from the shielding of the aryl ring. In contrast to the singlet signal of complex 1, all of the signals of the cyclopentadienyl protons in 3–8 split into doublet and triplet or multiplet peaks, indicating that the carbene ligand not only influences the extent of donation of d electrons from Mn to the cyclohexadienyl moiety but also changes the chemical environment of the C5H4 ring.The mass spectra of complexes 3–8 (Experimental section) showed, besides their molecular ions, the principal fragments produced by successive loss of CO ligands and peaks generated by further cleavage of these principal fragments. The most important is [C5H4C6H5Mn]] CHR]+, which is characteristic of the combination of carbene ligands with manganese. The molecular structure of complex 3 is shown in Fig. 1. The X-ray study confirmed the assigned structure and has many common features with previously determined carbene complex structures.17,30 The Mn(1)]C(12) distance is 1.885(6) Å, which signifies a high double-bond character, and is the same within experimental error as that in the analogous carbene complexes [Mn(h5-C5H5)(h5-C6H6)(CO)2{]] C(OEt)Ph}] [1.89(1) Å] 17 and [Mn(h5-C5H5)(h5-C6H6)(CO)2{]] C(OEt)C6H4Me-o}] [1.881(4) Å],17 but slightly longer than that in [Mn(h5-C5H5)(CO)2- {C(OEt)Ph}] [1.865(4) Å].30 The C(12)]O(1) bond length of 1.354(7) Å is the same within experimental error as that of the corresponding C]O bond in [Mn(h5-C5H5)(CO)2{C(OEt)Ph}] [1.356(17) Å] 30 and comparable with that in [Mn(h5-C5H5)(h5- C6H6)(CO)2{]] C(OEt)Ph}] [1.34(1) Å] 17 and [Mn(h5-C5H5)(h5- C6H6)(CO)2{]] C(OEt)C6H4Me-o}] [1.337(4) Å].17 Unusual features are the O(1)]C(20) [1.484(9) Å] and the C(20)]C(21) [1.44(1) Å] bond lengths of the OEt group; the former is much longer than that of a normal C]O distance and the latter is between normal C]C and C]] C distances, both of them being obviously different from that of OEt in analogous carbene complexes.For example, the corresponding O]C and C]C distances are 1.46(1) and 1.54(2) Å in [Mn(h5-C5H5)(h5-C6H6)- (CO)2{]] C(OEt)Ph}], and 1.471(17) and 1.507(21) Å in [Mn(h5- C5H5)(CO)2{C(OEt)Ph}]. It is proposed that the fairly strong electron donation from O(1) to the carbene carbon weakens the bonding between O(1) and C(20), leading to a lengthening of the bond distance and a lowering of the electron density around C(20).To compensate, part of the electron cloud around C(21)J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 209 Table 2 Proton NMR spectra of complexes 1–17 in (CD3)2CO at 20 8C* Complex d(C5H4C6H6) d(aryl) d(OEt) d(Me) 1 18 2 18 3 4 5 6 7 8 9 10 11 12 13 14 15 18 16 17 6.07 (t, 1 H), 5.20 (t, 2 H), 4.75 (s, 4 H), 3.51 (t, 2 H), 3.38 (t, 1 H) 6.07 (t, 1 H), 5.45 (t, 2 H), 5.30 (t, 2 H), 5.21 (t, 2 H), 3.45 (m, 3 H) 5.68 (t, 1 H), 5.20 (t, 2 H), 4.68 (m, 4 H), 3.21 (m, 3 H) 5.65 (t, 1 H), 5.19 (t, 2 H), 4.75 (t, 2 H), 4.69 (d, 2 H), 3.50 (t, 2 H), 3.30 (t, 1 H) 5.65 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.70 (d, 2 H), 3.52 (t, 2 H), 3.34 (m, 1 H) 5.68 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.69 (q, 2 H), 3.51 (t, 2 H), 3.33 (t, 1 H) 5.67 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.70 (d, 2 H), 3.53 (t, 2 H), 3.12 (t, 1 H) 5.74 (t, 1 H), 5.19 (t, 2 H), 4.83 (t, 2 H), 4.74 (d, 2 H), 3.51 (t, 2 H), 3.25 (t, 1 H) 5.68 (t, 1 H), 5.45 (d, 1 H), 5.40 (d, 1 H), 5.30 (d, 2 H), 5.24 (d, 2 H), 3.45 (m, 3 H) 5.67–5.61 (m, 1 H), 5.45 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 2 H), 5.21 (m, 2 H), 3.45 (t, 2 H), 3.37 (t, 1 H) 5.67 (t, 1 H), 5.45 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 1 H), 5.24 (t, 1 H), 5.20 (d, 2 H), 3.46 (t, 2 H), 3.39 (t, 1 H) 5.68 (t, 1 H), 5.45 (d, 1 H), 5.39 (d, 1 H), 5.30 (t, 1 H), 5.23 (d, 1 H), 5.21 (d, 2 H), 3.45 (t, 2 H), 3.38 (t, 1 H) 5.69 (t, 1 H), 5.46 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 2 H), 5.22 (m, 2 H), 3.46 (m, 2 H), 3.08 (t, 1 H) 5.72 (t, 1 H), 5.43 (t, 1 H), 5.39 (t, 1 H), 5.28 (t, 1 H), 5.23 (t, 1 H), 5.18 (d, 2 H), 3.43 (t, 2 H), 3.36 (t, 1 H) 5.74 (t, 2 H), 4.85 (t, 4 H), 3.94 (t, 4 H), 3.75 (t, 4 H), 3.33 (m, 6 H) 5.99 (m, 1 H), 5.60 (t, 1 H), 5.08 (m, 2 H), 4.56 (m, 2 H), 4.02 (t, 2 H), 3.95 (t, 2 H), 3.89 (t, 2 H), 3.83 (t, 2 H), 3.40 (q, 3 H), 3.19 (t, 3 H) 5.97 (t, 1 H), 5.57 (t, 1 H), 5.09 (m, 2 H), 4.65 (t, 2 H), 4.02 (t, 2 H), 3.95 (t, 2 H), 3.89 (t, 2 H), 3.83 (q, 2 H), 3.41 (t, 3 H), 3.23 (t, 3 H) 7.18 (m, 3 H), 6.84 (m, 1 H), 3.30 (s, 3 H) 7.36–7.09 (m, 4 H), 2.34 (s, 3 H) 7.36 (m, 2 H), 7.16 (m, 2 H), 2.33 (s, 3 H) 7.36 (m, 5 H) 7.70 (d, 2 H), 6.93 (d, 2 H), 3.84 (s, 3 H) 7.71 (d, 2 H), 7.40 (d, 2 H) 7.25–7.13 (m, 3 H), 6.84 (m, 1 H), 3.28 (s, 3 H) 7.26–7.09 (m, 4 H), 2.36 (s, 3 H) 7.36 (m, 2 H), 7.19 (m, 2 H), 2.35 (s, 3 H) 7.34 (m, 5 H) 7.69 (d, 2 H), 6.92 (d, 2 H), 3.86 (s, 3 H) 7.69 (d, 2 H), 7.38 (d, 2 H) 7.36–7.12 (m, 3 H), 6.86 (m, 1 H), 2.32 (s, 3 H) 7.36 (m, 2 H), 7.19 (m, 2 H), 2.36 (s, 3 H) 4.53 (q, 2 H), 1.43 (t, 3 H) 5.03 (q, 2 H), 1.53 (t, 3 H) 5.13 (q, 2 H), 1.56 (t, 3 H) 5.08 (q, 2 H), 1.57 (t, 3 H) 3.37 (q, 3 H), 1.60 (t, 3 H) 5.08 (q, 2 H), 1.57 (t, 3 H) 4.52 (q, 2 H), 1.43 (t, 3 H) 5.04 (q, 2 H), 1.55 (t, 3 H) 5.12 (q, 2 H), 1.58 (t, 3 H) 5.07 (q, 2 H), 1.57 (t, 3 H) 4.78 (q, 2 H), 1.60 (t, 3 H) 5.05 (q, 2 H), 1.55 (t, 3 H) 3.60 (q, 2 H), 1.44 (t, 3 H) 3.60 (q, 2 H), 1.58 (t, 3 H) 0.36 (s, 3 H) 0.33 (s, 3 H) 0.36 (s, 3 H) 0.34 (d, 3 H) 0.34 (d, 3 H) 0.35 (d, 3 H) 0.33 (d, 3 H) * Internal reference SiMe4.moves toward C(20) to form a partial double bond, C(20)] C(21). The carbene carbon C(12) lies essentially in the benzene ring plane (±0.0068 Å). The C5H4 ring plane is oriented at an angle Table 3 Crystal data and experimental details for complex 3 Empirical formula M Crystal symmetry Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z D/g cm23 m(Mo-Ka)/cm21 Orientation reflections, 2q range/8 Data collection range, 2q/8 No.unique data, total with I > 3.00s(I), No No. of parameters refined, Np Ra R9 b Goodness of fit c Maximum shift/error in final cycle C26H22Mn2O6 540.33 Triclinic P1� (no. 2) 12.018(4) 12.415(3) 8.758(2) 106.71(2) 102.15(2) 71.56(2) 1177.0(6) 2 1.525 11.12 14, 23.5–26.4 2–50.0 4152 2516 308 0.047 0.054 1.74 0.06 a R = S||Fo| 2 |Fc||/S|Fo|.b R9 = [Sw(|Fo| 2 |Fc|)2/Sw|Fo|2]� �� ; w = 1/s2(|Fo|). c [Sw(|Fo| 2 |Fc|)2/(No 2 Np)]� �� . of 84.878 with respect to the h5-dienyl plane, thus the C5H4 ring and h5-dienyl ring planes are almost perpendicular to each other. The angle between the benzene ring and the C5H4 ring planes is 80.098, thus these planes are also nearly perpendicular to each other. The angle between the benzene ring and the h5- dienyl C(7)–C(11) plane of 10.548 shows that the benzene ring plane is nearly parallel to the h5-dienyl ring plane.The preparation of complexes 9–14 is similar to that of 3–8. Compound 2 was treated with 2 molar equivalents of aryllithium reagents. LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4) in ether at 265 to 250 8C for 4 h. After work-up the orange-red crystalline complexes 9–14 with compositions [WMe(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R}] (Scheme 5) were isolated in 26–45% yields.The complexes have similar properties to those of 3–8. They are formulated as cyclohexadienyl- co-ordinated manganese carbene complexes on the basis of their elemental analyses and spectroscopic studies. There are two different M(CO)3 units in 2, however no manganese–tungsten dicarbene complexes or cyclopentadienylco- ordinated tungsten carbene complexes were obtained even though more than 2 molar equivalents of aryllithiums were used.The complexes 9–14 showed 1H NMR spectral data consistent with the assigned structures (see Table 2). Compared with 2, the cyclohexadienyl signals had greatly changed. The chemical shift of Ha moved upfield and the signal of Hb split into two triplet bands. Whereas a multiplet occurred for 2, the signals of Hc and Hd were two triplets for 9–14. As for the C5H4 ring, there is not much difference in the signals from 2 and 9–14. In210 J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 Table 4 Bond distances (Å) and angles (8) for complex 3 * Mn(1)]C(7) Mn(1)]C(9) Mn(1)]C(11) Mn(1)]C(22) Mn(2)]C(1) Mn(2)]C(3) Mn(2)]C(5) Mn(2)]C(25) O(1)]C(12) O(2)]C(22) O(4)]C(24) 2.231(6) 2.152(6) 2.244(5) 1.792(7) 2.142(6) 2.134(6) 2.147(5) 1.803(7) 1.354(7) 1.152(7) 1.148(8) Mn(1)]C(8) Mn(1)]C(10) Mn(1)]C(12) Mn(1)]C(23) Mn(2)]C(2) Mn(2)]C(4) Mn(2)]C(24) Mn(2)]C(26) O(1)]C(20) O(3)]C(23) O(5)]C(25) 2.158(6) 2.147(6) 1.885(6) 1.803(7) 2.139(6) 2.153(5) 1.779(9) 1.798(7) 1.484(9) 1.140(7) 1.134(7) O(6)]C(26) C(1)]C(5) C(3)]C(4) C(4)]C(6) C(6)]C(11) C(8)]C(9) C(10)]C(11) C(13)]C(14) C(14)]C(15) C(16)]C(17) C(18)]C(19) 1.145(7) 1.411(8) 1.407(7) 1.522(7) 1.520(8) 1.399(9) 1.380(8) 1.401(8) 1.387(9) 1.358(10) 1.494(9) C(1)]C(2) C(2)]C(3) C(4)]C(5) C(6)]C(7) C(7)]C(8) C(9)]C(10) C(12)]C(13) C(13)]C(18) C(15)]C(16) C(17)]C(18) C(20)]C(21) 1.418(9) 1.409(9) 1.417(8) 1.517(7) 1.409(8) 1.412(9) 1.501(8) 1.392(8) 1.395(10) 1.392(9) 1.44(1) C(4)]Mn(2)]C(25) C(5)]Mn(2)]C(24) C(5)]Mn(2)]C(26) C(24)]Mn(2)]C(26) C(12)]O(1)]C(20) C(1)]C(2)]C(3) C(3)]C(4)]C(6) CC(4)]C(6)]C(11) C(6)]C(7)]C(8) C(8)]C(9)]C(10) C(6)]C(11)]C(10) Mn(1)]C(12)]C(13) C(7)]Mn(1)]C(12) C(7)]Mn(1)]C(23) C(8)]Mn(1)]C(12) C(8)]Mn(1)]C(23) C(9)]Mn(1)]C(22) 152.1(3) 153.0(3) 97.1(3) 90.2(3) 122.8(5) 107.2(5) 124.2(5) 107.8(5) 111.3(5) 120.0(5) 116.8(5) 119.7(5) 123.8(4) 109.8(2) 86.0(3) 91.6(2) 122.3(3) 106.6(3) C(4)]Mn(2)]C(26) C(5)]Mn(2)]C(25) C(24)]Mn(2)]C(25) C(25)]Mn(2)]C(26) C(2)]C(1)]C(5) C(2)]C(3)]C(4) C(3)]C(4)]C(5) C(5)]C(4)]C(6) C(4)]C(6)]C(7) C(7)]C(6)]C(11) C(7)]C(8)]C(9) C(9)]C(10)]C(11) Mn(1)]C(12)]O(1) O(1)]C(12)]C(13) C(7)]Mn(1)]C(22) C(8)]Mn(1)]C(22) C(9)]Mn(1)]C(12) C(9)]Mn(1)]C(23) 95.8(2) 113.9(3) 91.5(3) 92.1(3) 108.4(6) 108.9(6) 107.7(5) 128.0(5) 117.0(5) 102.7(4) 120.3(5) 121.9(6) 132.5(4) 103.2(5) 166.2(2) 142.1(3) 102.0(2) 148.8(3) C(10)]Mn(1)]C(22) C(11)]Mn(1)]C(12) C(11)]Mn(1)]C(23) C(12)]Mn(1)]C(23) C(1)]Mn(2)]C(24) C(1)]Mn(2)]C(26) C(2)]Mn(2)]C(24) C(2)]Mn(2)]C(26) C(3)]Mn(2)]C(25) C(3)]Mn(2)]C(26) C(12)]C(13)]C(14) C(14)]C(13)]C(18) C(14)]C(15)]C(16) C(16)]C(17)]C(18) C(13)]C(18)]C(19) O(1)]C(20)]C(21) Mn(1)]C(23)]O(3) Mn(2)]C(25)]O(5) 90.1(2) 169.0(2) 86.7(2) 102.4(3) 139.7(3) 129.9(3) 102.3(3) 159.8(3) 140.9(3) 127.0(3) 118.4(5) 120.4(5) 119.0(6) 122.1(7) 121.3(6) 107.8(8) 173.8(6) 179.2(6) C(10)]Mn(1)]C(12) C(10)]Mn(1)]C(23) C(11)]Mn(1)]C(22) C(12)]Mn(1)]C(22) C(22)]Mn(1)]C(23) C(1)]Mn(2)]C(25) C(2)]Mn(2)]C(25) C(3)]Mn(2)]C(4) C(3)]Mn(2)]C(24) C(4)]Mn(2)]C(24) C(12)]C(13)]C(18) C(13)]C(14)]C(15) C(15)]C(16)]C(17) C(13)]C(18)]C(17) C(17)]C(18)]C(19) Mn(1)]C(22)]O(2) Mn(2)]C(24)]O(4) Mn(2)]C(26)]O(6) 135.3(2) 122.3(3) 102.3(2) 83.4(3) 95.3(3) 90.3(3) 103.3(3) 38.3(2) 90.5(3) 115.1(3) 121.0(5) 120.2(6) 120.3(6) 117.9(6) 120.7(6) 178.1(6) 178.1(7) 179.8(6) * Estimated standard deviations in the least significant figure are given in parentheses.addition, the chemical shift of the methyl protons attached to the W(CO)3 moiety is almost unchanged.It seems that the carbene ligand has much more influence on the chemical environment of the cyclohexadienyl than that of the cyclopentadienyl moiety, which suggests that the carbene ligand is attached to Mn instead of W. The mass spectra of complexes 9–14 showed no molecular ion peaks due to the difficulty of vaporization, but showed principal fragments produced by loss of CO and carbene ligands and peaks such as [MnCH(OEt)R]+ and [CH(OEt)R]+, which are characteristic of the carbene ligands.Fig. 1 Molecular structure of complex 3 showing the atom-labelling scheme and probability ellipsoids As mentioned above, the starting materials, 1 and 2, both have two different M(CO)3 (M = Mn or W) units co-ordinated to the different olefin ligands. Owing to the different reactivities of the carbonyls, only one kind of manganese carbene complex was obtained when treating 1 and 2 with aryllithium reagents.Thus, we chose [(OC)3Mn{(h5-C6H6)(h5-C5H4)Fe(h5- C5H4)(h5-C6H6)}Mn(CO)3] 15, in which the two Mn(CO)3 units have the same chemical environment, as starting material for the reaction under the same conditions. However, we did still not obtain the expected dicarbene complex. When compound 15 was treated with 2 molar equivalents of LiR (R = o- or p- MeC6H4) in ether at 255 to 235 8C for 4 h, followed by alkylation with Et3OBF4 in aqueous solution at 0 8C, work-up afforded orange-red crystalline complexes 16 and 17 (Scheme 6) in 44 and 31% yields.These complexes have properties similar Scheme 5 (i) 2LiR, Et2O, 265 to 250 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO M CO OC n C O–Li+ R 2 D6/04436K/A6 (OC)3MeW (OC)3MeW M CO OC (ii ) (i ) (OC)3MeW n C OEt R a b c d e f f e b c 9 o –MeC6H4 10 m–MeC6H4 11 p –MeC6H4 12 Ph 13 p –MeOC6H4 14 p –CF3C6H4 RJ. Chem. Soc., Dalton Trans., 1997, Pages 205–211 211 to those of 3–8. They are formulated as cyclohexadienylco- ordinated manganese carbene complexes with only one carbene on the basis of their elemental analyses and spectroscopic studies.Similarly, even increasing the amount of the aryllithium reagents used gave no dicarbene manganese complexes. In the 1H NMR spectra of complexes 16 and 17, resonances at d 3.60 and 1.58–1.44 attributed to the ethoxy group and at d 7.36–6.86 assigned to the aryl group, in addition to the expected proton signals of the cyclopentadienyl and cyclohexadienyl groups, were observed. As compared with 15, the proton signals of the cyclohexadienyl ring of 16 and 17 changed greatly.In 15, Ha and Ha9 and Hb and Hb9 shared the same triplet signals, and the signals of Hc, Hc9 and Hd, Hd9 appeared as a multiplet. On the other hand, for 16 and 17, the signals of Ha, Ha9 and Hb, Hb9 all split into two multiplet or triplet bands, and the signals of Hc, Hc9 and Hd, Hd9 also appeared as a triplet or a quartet.As for the C5H4 rings, the proton signals appeared as two triplet bands for 15 but as four triplets for 16 and 17. The 1H NMR spectra showed that the chemical environments of the two cyclohexadienyl ligands in both complexes 16 and 17 are very different from that of 15, being characteristic of a complex with only one carbene ligand. The mass spectra of complexes 16 and 17 showed no molecular ions but the principal fragments produced by successive loss of CO ligands and peaks such as [Mn(C6H6C5H4)2Fe]+, [C6H5C5H4Fe]+, [MnC6H5C5H4]+ and [RCH(OC2H5)]+, all of which provided useful structure information.Scheme 6 (i) Et2O, 255 to 235 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO Fe Mn CO OC CO Mn CO OC CO Fe M CO OC + n C 2LiR (i ) OEt R (ii ) D6/04436K/A7 a b c d e f f e b c a¢ b¢ c¢ d¢ e¢ f¢ f¢ e¢ b¢ c¢ 15 16 o –MeC6H4 17 p –MeC6H4 R Acknowledgements Financial support from the National Natural Science Foundation of China and the Science Foundation of the Chinese Academy of Sciences is gratefully acknowledged.References 1 J.-B. Chen, G.-X. Lei, W.-H. Xu, X.-L. Jin, M.-C. Shao and Y.-Q. Tang, J. Organomet. 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