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Synthesis and structures of organometallic derivatives of 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene |
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Dalton Transactions,
Volume 1,
Issue 20,
1997,
Page 3867-3878
Stephen Barlow,
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DALTON J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3867 Synthesis and structures of organometallic derivatives of 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene Stephen Barlow Douglas R. Cary Mark J. Drewitt and Dermot O’Hare *,† Inorganic Chemistry Laboratory University of Oxford South Parks Road Oxford UK OX1 3QR A new fused-ring compound 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene (H2L1) has been synthesized from p-xylene. Three transition-metal derivatives [Mn(h5-HL1)(CO)3] [Rh(h5-HL1)(h-C5Me5)]1[SbF6]2 and [Cr(h6-H2L1)(CO)3] have been characterised spectroscopic and crystallographic data for these compounds show the ligand system is strongly electron donating. Although H2L1 is readily deprotonated to the monoanion by potassium metal or potassium hydride surprisingly we have been unable to form (L1)22.The crystal structure of [K]1[HL1]2?18-crown-6 reveals the potassium ion to be sandwiched between the crown ether (1,4,7,10,13,16- hexaoxacyclooctadecane) and the (HL1)2 anion. Oligomers and polymers comprising strongly interacting metallocene units are expected to exhibit interesting delocalisation properties. One way to realise such materials may be a polymer in which metal atoms alternate with ligands such as pentalene and s-indacene (Fig. 1); these ligands can be regarded as two cyclopentadienyl units fused to one another either directly or through a benzene ring respectively.1 The bimetallic species [{M(h-C5Me5)}2L]n1 (L = pentalene or s-indacene; M = Fe Co or Ni; n = 0 1 or 2) have been studied by Manríquez and co-workers.2–5 Electron spin resonance Mössbauer electrochemical and magnetic measurements showed the coupling between metal centres to be extremely strong compared to many other linked metallocene systems.6 This is not surprising when one examines the bonding in these molecules; an extended-Hückel molecular orbital scheme published for the pentalene species is related to those for (h-C5H5)3M2 tripledecker complexes.2 Systems based on related ligands such as asindacene for which relatively localised structures can be drawn show significantly weaker interactions.Strategies for the rational stepwise construction of fused-ring oligomers and polymers have been outlined by Manríquez and Román.1 However synthetic progress towards such a goal has been hampered by escalating insolubility with increasing oligomerisation; trimetallic iron species based on pentalene have been reported 7 but the molecule shown in Fig.2 which could in principle function as a building block for higher oligomers has a solubility in boiling toluene of only ca. 400 mg l21.7 Clearly further progress will require a readily available fused-ring ligand with solubilising substituents. To this end we have recently begun investigating the organometallic chemistry of substituted sindacene ligand systems. Our first strategy was to investigate the effect of permethylation on the s-indacene system since many differences including solubility have been reported between C5H5 and C5Me5 chemistry.8–16 We also hoped that permethylation would afford kinetic and/or thermodynamic stability to {M(h-C5Me5)}2L type complexes for metals other than Fe Co and Ni.Thus here we described the synthesis and some chemistry of 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene. Part of this work has appeared as a preliminary communication.17 Experimental Instrumental methods Elemental analyses were performed by the analytical depart- † The Royal Society of Chemistry Sir Edward Frankland Fellow. ment of the Inorganic Chemistry Laboratory Oxford. Solution NMR spectra were recorded using a Bruker AM 300 or a Varian Unity Plus 500 spectrometer referenced via the residual protio-solvent; chemical shifts (d) are quoted in ppm relative to SiMe4 at 0 ppm. Low-resolution electron impact (EI) mass spectra were recorded using an AEI MS 9802 instrument calibrated with perfluorokerosene. Fourier-transform infrared spectra were recorded using a Perkin-Elmer FT 1710 spectrometer employing neat liquids or strong solutions between KBr plates.General considerations Operations involving oxygen- or water-sensitive materials were carried out under nitrogen or in vacuo using standard Schlenk techniques or a Vacuum Atmospheres glove-box. Where necessary solvents were dried by reflux over either sodium– potassium alloy [pentane light petroleum (b.p. 40–60 8C) diethyl ether] potassium (tetrahydrofuran thf) sodium [toluene light petroleum (b.p. 100–120 8C)] or P2O5 (dichloromethane). These solvents were distilled under nitrogen and stored under nitrogen over activated type 4 Å molecular sieves. They and others when appropriate were deoxygenated prior to use by passage of a stream of nitrogen through the solvent. The compounds CDCl3 CD2Cl2 and (CD3)2CO were used as received; C6D6 was dried by reflux over potassium and purified by trap to trap distillation.The following materials were used as supplied commercially without further purification methyllithium tertbutyllithium and n-butyllithium solutions p-xylene (99%) Fig. 1 Schematic view of an organometallic polymer based on pentalene or s-indacene M M M = or Fig. 2 A poorly soluble pentalene-based oligomer Fe Fe H H H H Fe 3868 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 methyl iodide (99.5%) and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) (99%) from Aldrich; silver(I) hexafluoroantimonate from Fluorochem. Potassium hydride was obtained from Aldrich as a dispersion in mineral oil; it was washed repeatedly with dry light petroleum (b.p. 40–60 8C) under nitrogen dried in vacuo and stored in an inert atmosphere.Potassium was obtained from Aldrich under mineral oil. It was washed with light petroleum (b.p. 40–60 8C) and cut and weighed out under light petroleum before transferring to the reaction vessel against a counter flow of nitrogen. Literature procedures were followed for the synthesis of [Cr(CO)3- (NH3)3] 18,19 and [{Rh(h-C5Me5)Cl2}2] 20 (from C5Me5H21 and RhCl3?xH2O). The compound FeCl2?1.5thf was obtained by Soxhlet extraction of anhydrous FeCl2 obtained by heating commercial FeCl2?4H2O to 200 8C in vacuo for 15 h. The compound [Mn(CO)3(py)2Br] (py = pyridine) was prepared following the general method given by Abel and Wilkinson.22 Specifically [Mn(CO)5Br] 23 (3.40 g 12.3 mmol) and pyridine (15 cm3) were loaded in a Schlenk tube and deoxygenated before heating slowly to 120 8C under nitrogen (with free access to an oil bubbler to allow CO to escape).After 30 min at 120 8C the pyridine was removed in vacuo. The solids were transferred to a sintered-glass Buchner funnel washed with pentane (3 × 20 cm3) and then dried on the Buchner funnel and in vacuo. The resulting orange-yellow powder gave satisfactory elemental analysis and showed strong carbonyl stretches in the infrared spectrum at 1911 1950 and 2033 cm21. Syntheses 2,3,4,7-Tetramethylindan-1-one I. Aluminium chloride (260 g 1.95 mol) and carbon disulfide (1 l) pre-dried on activated molecular sieves were placed in a round-bottomed flask (3 l) fitted with a mechanical stirrer and a nitrogen inlet. The mixture was cooled in ice–salt and vigorously stirred under nitrogen.To this mixture was added a mixture of tiglyl (2-methylbut- 2-enoyl) chloride (169 g 1.42 mol) and p-xylene (175 cm3 1.43 mol) over a period of 1 h. After 2 h of stirring at ca. 210 8C the orange reaction mixture was allowed to warm to room temperature and was stirred for 15 h. The flask was then fitted with a reflux condenser; the red-brown mixture was then refluxed under nitrogen for 3 h. After cooling to room temperature the reaction mixture was poured carefully in air onto a mixture of concentrated HCl (1.25 l) and ice (2 kg). When the reaction had subsided the mixture was transferred to a separating funnel; the green lower (CS2) layer was run off and the aqueous layer extracted with diethyl ether (3 × 500 cm3). The combined CS2 and ether layers were dried over MgSO4 and filtered prior to solvent removal on a rotary evaporator.The brown residue was distilled at ca. 0.1 mmHg (ca. 13.3 Pa) using a 60 cm Vigreux column; the major fraction was a colourless liquid boiling at ca. 97 8C (147 g 0.78 mol 55%) and partially crystallising in the condenser; the liquid was found to be a mixture of the two isomers of 2,3,4,7-tetramethylindan-1-one I (ca. 3 1 Ia to Ib). 1H NMR (CDCl3) Ia d 1.26 (d 3 H J = 7.5 CHCH3) 1.35 (d 3 H J = 7.0 CHCH3) 2.25 (q of d 1 H J = ca. 2.3 7.5 aliphatic CH) 2.37 (s 3 H benzylic CH3) 2.60 (s 3 H benzylic CH3) 2.96 (q of d 1 H J = ca. 2.3 7.5 aliphatic CH) 7.03 (d 1 H J = 7.5 aromatic CH 7.24 (d 1 H J = 7.5 aromatic CH); Ib d 1.09 (d 3 H J = 7.1 Hz CHCH3) 1.24 (d 3 H J = 7.3 Hz CHCH3) 2.37 (s 3 H benzylic CH3) 2.60 (s 3 H benzylic CH3) 2.77 (pseudo-quintet 1 H J = ca.7 aliphatic CH) 3.48 (pseudo-quintet 1 H J = ca. 7 Hz aliphatic CH) 7.03 (d 1 H J = 7.5 aromatic CH) and 7.24 (d 1 H J = 7.5 Hz aromatic CH). EI mass spectrum m/z 188 (M1) 173 (M1 2 Me) 158 (M1 2 2Me) and 143 (M1 2 3Me). IR (selected data liquid) 1699 cm21. 1,2,3,4,7-Pentamethylindene II. A solution of methyl iodide (45 cm3 103 g 0.73 mol) in dry diethyl ether (250 cm3) was added under nitrogen to a round-bottomed flask (2 l) containing a stirred suspension of magnesium turnings (16.2 g 0.67 mol) in dry diethyl ether (120 cm3). The rate of addition was controlled so the exothermic reaction maintained the contents of the flask at a gentle reflux. After the addition was complete the resulting grey solution was stirred for 45 min before addition of dry light petroleum (b.p.100–120 8C) (80 cm3). The ether was then removed under reduced pressure to yield a grey suspension to which dry light petroleum (b.p. 40–60 8C) (160 cm3) was added. The resulting slurry of methylmagnesium iodide was cooled in ice; a solution of compound I (102 g 0.54 mol) in dry light petroleum (b.p. 40–60 8C) (100 cm3) was then added under nitrogen over a period of 1 h. When the addition was complete the mixture was refluxed for 3 h. When the reaction mixture had cooled a mixture of concentrated HCl (100 cm3) and water (300 cm3) was added slowly. The resulting mixture was transferred in air to a separating funnel and extracted with diethyl ether (3 × 250 cm3). During this time the organic layers rapidly darkened presumably due to the aerial oxidation of iodide to iodine.The combined organic layers were therefore washed with 0.25 M aqueous sodium thiosulfate (3 × 200 cm3). The organic layers were filtered into a round-bottomed flask and stirred for 15 h with concentrated HCl (50 cm3). After this time a saturated aqueous solution of Na2CO3 was carefully added until the mixture was neutral. The layers were separated; the organic layer was washed with water (2 × 250 cm3). After drying over anhydrous Na2CO3 and filtering the solvent was removed in vacuo. The resulting white crystalline solid (97 g 0.52 mol 96%) was found to be essentially pure 1,2,3,4,7-pentamethylindene II by 1H NMR spectroscopy (CDCl3) d 1.27 (d 3 H J = 7.3 CHCH3) 1.98 (s 3 H CH3) 2.24 (s 3 H CH3) 2.40 (s 3 H CH3) 2.58 (s 3 H CH3) 3.19 (q 1 H J = 7.3 aliphatic CH) 6.83 (d 1 H J = 7.6 aromatic CH) and 6.93 (d 1 H J = 7.6 Hz aromatic CH).EI mass spectrum m/z 186 (M1) 171 (M1 2 Me) 156 (M1 2 2Me) and 141 (M1 2 3Me). Ketone III. A mixture of aluminium chloride (95 g 0.71 mol) and carbon disulfide (300 cm3) pre-dried on activated molecular sieves was mechanically stirred in a flask (1 l) and cooled in ice–salt; a solution of tiglyl chloride (65 g 0.56 mol) and compound II (97 g 0.52 mol) in carbon disulfide (70 cm3) was added under nitrogen over a period of 90 min. After 2 h stirring at ca. 210 8C the orange reaction mixture was allowed to warm to room temperature and was stirred for 15 h. The flask was then fitted with a reflux condenser; the red-brown mixture was refluxed under nitrogen for 3 h. After cooling to room temperature the reaction mixture was carefully poured onto a mixture of concentrated HCl (500 cm3) and ice (1 kg).Diethyl ether (400 cm3) were added and the mixture was transferred to a separating funnel. The brown lower (aqueous) layer and green organic layer were separated; the aqueous layer was further extracted with diethyl ether (2 × 400 cm3). After drying over MgSO4 the combined organic layers were filtered and the solvent removed in vacuo to yield a thick green oil. Proton NMR spectroscopy showed this oil was a complex mixture of products including two isomers of the ketone IIIa and IIIb in a ratio of ca. 2 1. Cooling a solution of the oil in dichloromethane–light petroleum (b.p. 40–60 8C) to 280 8C yielded a white powder (22.5 g) which was collected on a sintered-glass Buchner funnel washed with cold light petroleum (b.p.40–60 8C) and characterised as III principally the isomer denoted IIIa. Recrystallisation from hexane at 230 8C gave pure IIIa (Found C 85.45; H 8.75. Calc. for C19H24O C 85.03; H 9.01%). 1H NMR (CDCl3) d 1.25 (d 3 H J = 7.3 Hh) 1.28 (d 3 H J = 7.8 Ha) 1.32 (d 3 H J = 6.9 Hd) 1.99 (s 3 H Hg) 2.25 (s 3 H Hf) 2.26 (q of d 1 H J = ca. 1.5 7.8 Hb) 2.55 (s 3 H He) 2.67 (s 3 H Hj) 2.98 (q of d 1 H J = ca. 1.5 6.9 Hc) and 3.22 (q 1 H J = 7.3 Hz Hi) (assignments refer to Scheme 1). 13C-{1H} NMR (CDCl3) d 12.7 (CH3) 14.4 (2 × CH3) 15.1 (CH3) 15.4 (CH3) 17.7 (CH3) 21.7 (CH3) 40.4 (CH) 45.6 (CH) 52.4 (CH) 124.4 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3869 (quaternary) 128.6 (quaternary) 130.0 (quaternary) 132.5 (quaternary) 147.3 (quaternary) 149.6 (quaternary) 150.5 (quaternary) 158.8 (quaternary) and 210.8 (C]] O quaternary).EI mass spectrum m/z 268 (M1 100) 253 (M1 2 Me 35) 238 (M1 2 2Me 3) 223 (M1 2 3Me 5) and 212 (M1 2 CHMe]] CHMe 48%) and many lower mass fragments. IR (strong CH2Cl2 solution selected data) 1586 and 1685 cm21. Concentration of the dichloromethane–light petroleum supernatant followed by cooling produced a pale green powder (3.9 g) identified as principally compound IIIb. Recrystallisation from hexane at 230 8C afforded pure IIIb (Found C 86.11; H 9.31. Calc. for C19H24O C 85.03; H 9.01%.) 1H NMR (CDCl3) d 1.09 (d 3 H J = 7.1 Hd) 1.23 (d 3 H J = 7.3 Ha) 1.26 (d 3 H J = 7.3 Hh) 2.00 (s 3 H Hg) 2.27 (s 3 H Hf) 2.58 (s 3 H He) 2.67 (s 3 H Hj) 2.80 (pseudoquintet 1 H J = ca. 7.3 Hb) 3.24 (q 1 H J = 7.3 Hi) and 3.50 (pseudo-quintet 1 H J = ca.7.1 Hz Hc). 13C-{1H} NMR (CDCl3) d 10.2 (CH3) 12.6 (CH3) 14.2 (CH3) 14.4 (CH3) 14.6 (CH3) 15.4 (CH3) 17.8 (CH3) 35.8 (CH) 45.6 (CH) 48.1 (CH) 123.8 (quaternary) 128.8 (quaternary) 129.7 (quaternary) 132.5 (quaternary) 146.9 (quaternary) 149.3 (quaternary) 149.9 (quaternary) 159.3 (quaternary) and 209.9 (C]] O quaternary). EI mass spectrum m/z 268 (M1 100) 253 (M1 2 Me 35) 238 (M1 2 2Me 3) 223 (M1 2 3Me 5) and 212 (M1 2 CHMe]] CHMe 48%) and many lower mass fragments. IR (strong CH2Cl2 solution selected data) 1587 and 1689 cm21. The remaining supernatant from the powders was chromatographed on silica (Fluka 60739). The column was eluted with hexane containing increasing proportions of diethyl ether producing a number of bands. Neat ether eluted a yellow band; solvent removal afforded a yellow solid (47 g) shown to be a mixture of isomers of III sufficiently pure for use in further reactions.The total yield was therefore 72 g (53%). 1,2,3,4,5,6,7,8-Octamethyl-1,5-dihydro-s-indacene IV (H2L1). Methylmagnesium iodide (22 cm3 50 g 0.35 mol) was prepared as for compound II. A solution of III (72 g 0.27 mol) in dry light petroleum (b.p. 40–60 8C) (50 cm3) was then added to a suspension of MgMeI in light petroleum (b.p. 40–60 8C) under nitrogen over a period of 90 min. When the addition was complete the mixture was refluxed for 5 h. When the reaction mixture had cooled a mixture of concentrated HCl (50 cm3) and water (150 cm3) was added slowly. The resulting mixture was transferred in air to a separating funnel together with diethyl ether (200 cm3).The aqueous layer and solids were extracted with diethyl ether (4 × 500 cm3). White solids suspended in the organic layer (22 g) were filtered off and dried by washing with methanol and diethyl ether on a Buchner funnel. Proton NMR spectroscopy showed this solid to be essentially pure 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene IV. The diethyl ether solution was stirred for 15 h with concentrated HCl (100 cm3). After neutralisation with saturated aqueous Na2CO3 separation and drying over MgSO4 the solution was concentrated and cooled to 280 8C to yield additional (ca. 8 g) IV. The total yield was therefore ca. 30 g (0.11 mol 42%). An analytical sample was obtained after two recrystallisations from hot toluene (Found C 90.79; H 10.04. Calc. for C20H26 C 90.16; H 9.84%).1H NMR (CDCl3) d 1.25 (d 6 H J = 7.5 CHCH3) 1.95 (s 6 H CH3) 2.23 (s 6 H CH3) 2.56 (s 6 H CH3) and 3.18 (q 2 H J = 7.5 Hz CH). 13C-{1H} NMR (CDCl3) d 12.2 (CH3) 14.5 (CH3) 15.9 (CH3) 16.0 (CH3) 46.1 (CH) 122.9 (quaternary) 132.1 (quaternary) 140.1 (quaternary) 142.6 (quaternary) and 147.3 (quaternary). EI mass spectrum m/z 266 (M1 100) 252 (M1 2 Me 98) 236 (M1 2 2Me 33) 222 (M1 2 3Me 29) 206 (M1 2 4Me 21) and 192 (M1 2 5Me 5%). [K]1[HL1]2?0.1thf Va and [K]1[HL1]2?18-crown-6 Vb. [K]1[HL1]2?0.1thf Va method A. Potassium hydride (450 mg 11.2 mmol) and dry thf (50 cm3) were stirred in a Rotaflo ampoule. A slurry of compound IV (1.00 g 3.75 mmol) in dry thf (80 cm3) was added to this suspension; the ampoule was evacuated until the solvent began to boil then closed and placed in an oil-bath at 85 8C for 5��� h to yield a red solution.The excess of KH was filtered off; the solvent was then removed in vacuo to afford an orange-yellow oily solid. Prolonged drying in vacuo resulted in an essentially quantitative yield of a golden solid shown by NMR spectroscopy to be [K]1[HL1]2?0.1thf Va. [K]1[HL1]2?0.1thf Va method B. Potassium sand was made in a Rotaflo ampoule from potassium metal (421 mg 10.8 mmol) in dry thf (40 cm3). A slurry of compound IV (1.00 g 3.75 mmol) in dry thf (35 cm3) was added. After stirring for 2 h the indacene had mostly disappeared and the solution was reddish. The ampoule was then evacuated until the solvent began to boil then closed and placed in an oil-bath at 85 8C for 14 h. The excess of potassium was filtered off; the solvent was then removed in vacuo to afford an orange-yellow oily solid.Prolonged drying in vacuo resulted in an essentially quantitative yield of a golden solid shown by NMR spectroscopy to be [K]1[HL1]2?0.1thf Va. 1H NMR (C6D6) d 1.14 (d 3 H J = 6.5 CHCH3) 1.37 (m 0.5 H CH2 thf) 1.88 (s 3 H CH3) 1.92 (s 3 H CH3) 2.20 (s 3 H CH3) 2.25 (s 3 H CH3) 2.30 (s 3 H CH3) 2.39 (s 3 H CH3) 2.67 (s 3 H CH3) 3.08 (q 1 H J = 6.4 Hz CH) and 3.39 (m 0.5 H CH2 thf). 13C-{1H} NMR (C6D6) d 10.9 (CH3) 12.5 (CH3) 13.2 (CH3) 14.0 (CH3) 15.9 (CH3) 16.8 (CH3) 17.3 (CH3) 18.4 (CH3) 25.7 (CH2 thf ) 45.1 (CH) 67.5 (CH2 thf) 98.2 (quaternary) 99.1 (quaternary) 116.8 (quaternary) 118.7 (quaternary) 122.0 (quaternary) 123.9 (quaternary) 124.2 (quaternary) 131.2 (quaternary) 133.0 (quaternary) 134.1 (quaternary) and 137.7 (quaternary).[K]1[HL1]2?18-crown-6 Vb. The addition of thf (30 cm3) to a flask containing potassium chunks (127 mg 3.25 mmol) 18- crown-6 (860 mg 3.25 mmol) and compound IV (433 mg 1.63 mmol) gave a yellow heterogeneous mixture that slowly grew homogeneous and turned red-yellow within 2 h. After 3 h the mixture was filtered through filter aid on a frit. Pentane was layered onto the solution and allowed slowly to diffuse resulting in the formation of thin orange plates of [K(18-crown- 6)]1[HL1]2 suitable for X-ray crystallography. The same results were obtained using toluene as the solvent at reflux followed by filtration and cooling to 245 8C (675 mg 73%). 1H NMR (C6D6) d 1.58 (d 3 H J = 7.0 CHCH3) 2.11 (s 3 H CH3) 2.14 (s 3 H CH3) 2.46 (s 3 H CH3) 2.66 (s 3 H CH3) 3.03 (s 3 H CH3) 3.11 (s 24 H CH2) 3.16 (s 3 H CH3) 3.25 (s 3 H CH3) and 3.35 (q 1 H CH).13C-{1H} NMR (C6D6) d 70.1 (CH2 18- crown-6); the remaining resonances could not be satisfactorily resolved due to low solubility of the compound. [Mn(Á5-HL1)(CO)3] 1. A solution of compound Va (536 mg 1.76 mmol) in dry thf (30 cm3) was cooled to 278 8C; a slurry of [Mn(CO)3(py)2Br] (665 mg 1.76 mmol) in thf (40 cm3) was added dropwise. After the addition was complete the mixture was allowed to warm to room temperature; it soon became orange. After 20 h the solvent was removed in vacuo and the solids were extracted with light petroleum (b.p. 40–60 8C). The extracts were filtered through a bed of Celite reduced in volume and cooled to 280 8C. The solvent was decanted from the resulting solids which were washed with cold light petroleum (b.p.40–60 8C) and dried in vacuo to yield orange-yellow microcrystals (351 mg 0.87 mmol 49%) shown by NMR spectroscopy to be an approximately 1 1 mixture of the two isomers of [Mn(h5-HL1(CO)3] 1 (Found C 68.97; H 6.37. Calc. for C23H25MnO3 C 68.31; H 6.23%). 1H NMR (C6D6) 1a d 1.02 (d 3 H J = 7.0 CHCH3) 1.60 (s 3 H CH3) 1.66 (s 6 H CH3) 1.98 (s 3 H CH3) 2.13 (s 3 H CH3) 2.14 (s 3 H CH3) 2.38 (s 3 H CH3) 2.65 (s 3 H CH3) and 2.97 (q 1 H J = 7.0 CH); 1b d 1.04 (d 3 H J = 7.0 CHCH3) 1.60 (s 3 H CH3) 1.63 (s 6 H CH3) 1.98 (s 3 H CH3) 2.07 (s 3 H CH3) 2.14 (s 3 H CH3), 3870 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 2.32 (s 3 H CH3) 2.65 (s 3 H CH3) and 2.78 (q 1 H J = 7.0 Hz CH). 13C-{1H} NMR (C6D6) 1a d 10.5 (CH3) 12.3 (CH3) 13.3 (CH3) 13.7 (CH3) 15.2 (CH3) 16.2 (CH3) 16.3 (CH3) 17.0 (CH3) 45.3 (CH) 85.3 (quaternary) 87.5 (quaternary) 101.7 (quaternary) 104.1 (quaternary) 122.0 (quaternary) 123.5 (quaternary) 132.4 (quaternary) 142.0 (quaternary) 145.2 (quaternary) 145.8 (quaternary) and 227.3 (MnCO) (remaining quaternary obscured by solvent); 1b d 10.6 (CH3) 12.2 (CH3) 12.5 (CH3) 12.8 (CH3) 13.6 (CH3) 15.2 (CH3) 16.2 (CH3) 16.9 (CH3) 44.9 (CH) 86.3 (quaternary) 86.6 (quaternary) 100.2 (quaternary) 103.8 (quaternary) 122.1 (quaternary) 123.5 (quaternary) 132.4 (quaternary) 142.5 (quaternary) 145.5 (quaternary) 145.6 (quaternary) and 227.3 (MnCO) (remaining quaternary obscured by solvent).EI mass spectrum m/z 404 (M1 17) 348 (M1 2 2CO 8) 320 (M1 2 3CO 88) 265 [(HL1)1 50] 250 [(HL1)1 2 Me 30] and 235 [(HL1)1 2 2Me 11%] and many lower mass fragments.IR (strong CH2Cl2 solution selected data) 1914s (br) and 2001s cm21. Single crystals of the endo isomer 1a were obtained by slow cooling of a pentane solution of the isomeric mixture to 280 8C. [Rh(Á5-HL1)(Á-C5Me5)]1[SbF6]2 2. Silver(I) hexafluoroantimonate weighed out under nitrogen owing to its hygroscopic behaviour (684 mg 1.99 mmol) was added against a counter- flow of nitrogen to a deoxygenated solution of [{Rh(h-C5Me5)- Cl2}2] (684 mg 0.498 mmol) in acetone (4 cm3). White silver(I) chloride instantly precipitated. After 10 min the precipitate was filtered off in air using a Buchner funnel with a bed of Celite. The precipitate and Celite was washed with acetone (14 cm3); the combined acetone solutions were stirred with compound IV (200 mg 0.75 mmol) for 24 h.The mixture was then filtered and diethyl ether (ca. 20 cm3) added; the yellow solution was slowly cooled to 280 8C to yield yellow microcrystals. The solvent was decanted off and the solids were washed with diethyl ether (2 × 20 cm3) before drying in vacuo to give the endo isomer of [Rh(h5-HL1)(h-C5Me5)]1[SbF6]2 2a (105 mg 0.14 mmol 19%). Attempts to isolate more solids by addition of diethyl ether to the combined supernatant and washings resulted in deposition of a brown oil which was not investigated. The analytical sample of 2a was obtained by recrystallisation from dichloromethane –diethyl ether. The crystals of 2a used for structure determination were grown by layering a dichloromethane solution (ca. 5 mg in 1 cm3) with diethyl ether (ca. 6 cm3) (Found C 48.74; H 6.03.Calc. for C30H40F6RhSb C 48.74; H 5.45%). 1H NMR (CD2Cl2) d 1.24 (d 3 H JHH = 7.3 CHCH3) 1.57 (s 15 H C5Me5 CH3) 1.82 (s 3 H HL1 CH3) 1.96 (s 3 H HL1 CH3) 2.21 (s 3 H HL1 CH3) 2.26 (s 3 H HL1 CH3) 2.27 (s 3 H HL1 CH3) 2.43 (s 3 H HL1 CH3) 2.60 (s 3 H HL1 CH3) and 3.26 (q 1 H JHH = 7.3 Hz CH). 13C-{1H} NMR (CD2Cl2) d 8.2 (s C5Me5 CH3) 8.8 (s HL1 CH3) 12.0 (s HL1 CH3) 12.4 (s HL1 CH3) 12.9 (s HL1 CH3) 15.3 (s HL1 CH3) 16.1 (s HL1 CH3) 17.3 (s HL1 CH3) 17.6 (s HL1 CH3) 45.7 (s CH) 91.8 (d JRhC = 6.5 HL1 RhC) 91.9 (d 7.5 HL1 RhC) 98.0 (d JRhC = 7.0 C5Me5 RhC) 100.8 (d JRhC = ca. 5 HL1 RhC) 102.9 (d JRhC = ca. 9 HL1 RhC) 103.9 (d JRhC = ca. 6 Hz HL1 RhC) 117.9 (s HL1 quaternary) 122.1 (s HL1 quaternary) 132.3 (s HL1 quaternary) 146.2 (s HL1 quaternary) and 149.8 (s HL1 quaternary).[Cr(Á6-H2L1)(CO)3] 3. The compound [Cr(NH3)3(CO)3] (1.304 g 6.97 mmol) and IV (H2L1) (1.305 g 4.90 mmol) were refluxed in sieve-dried p-dioxane (50 cm3) under N2 for 7 h. After solvent removal the olive-green residue was extracted with dichloromethane. The extracts were filtered through Celite the solvent volume was reduced in vacuo and the solution was cooled to 280 8C. The resulting yellow microcrystals were filtered off washed with cold dichloromethane and dried in vacuo. A second crop was obtained by adding light petroleum (b.p. 40– 60 8C) to the supernatant reducing the solvent volume and cooling to 280 8C. The total yield was 1.660 g (4.12 mmol 84%). The NMR spectra showed the product to be an approximately 1 1 2 endo/endo (3a) exo/exo (3b) endo/exo (3c) isomer mixture.Single crystals of the endo/exo isomer 3c were obtained by slow cooling of a dichloromethane solution of the isomeric mixture (Found C 67.79; H 6.03. Calc. for C23H26CrO3 C 68.64; H 6.51%). 1H NMR (C6D6) isomeric mixture d 0.89 (d J = 7.5 exo CHCH3) 0.96 (d J = 7.5 exo CHCH3) 1.26 (d J = 7.5 endo CHCH3) 1.31 (d J = 7.5 endo CHCH3) 1.51 (s 2 × CH3) 1.58 (s CH3) 1.59 (s CH3) 1.87 (s CH3) 1.90 (s CH3) 1.92 (s CH3) 2.00 (s CH3) 2.22 (s CH3) 2.23 (s CH3) 2.27 (s CH3) 2.39 (s CH3) 2.60 (q J = 7.5 CH) 2.62 (q J = 7.5 CH) 2.93 (q J = 7.5 CH) and 3.30 (q J = 7.5 Hz CH). 13C-{1H} NMR (C6D6) isomeric mixture d 12.0 (CH3) 12.3 (2 × CH3) 12.4 (CH3) 13.8 (2 × CH3) 14.7 (CH3) 14.8 (CH3) 14.9 (CH3) 15.1 (CH3) 15.4 (CH3) 16.3 (2 × CH3) 16.4 (CH3) 19.7 (CH3) 20.2 (CH3) 45.5 (CH) 45.8 (CH) 45.9 (CH) 46.6 (CH) 93.3 (quaternary) 94.6 (quaternary) 104.2 (quaternary) 104.9 (quaternary) 108.6 (quaternary) 113.3 (quaternary) 115.0 (quaternary) 117.4 (quaternary) 117.7 (quaternary) 118.5 (quaternary) 120.8 (quaternary) 122.6 (quaternary) 130.2 (quaternary) 130.3 (quaternary) 130.4 (quaternary) 131.0 (quaternary) 144.1 (quaternary) 147.1 (quaternary) 147.2 (quaternary) 147.9 (quaternary) and 236.7 (CO).EI mass spectrum m/z 402 (M1 2) 346 (M1 2 2CO 1) 318 (M1 2 3CO 12) and 300 (2%) and many lower mass fragments. IR (strong CH2Cl2 solution selected data) 1844s and 1934s; (strong thf solution selected data 1863s and 1941s cm21. Crystallography Experimental details of the crystal structure determinations are summarised in Table 4. All crystallographic data were acquired with Mo-Ka radiation (l = 0.710 73 Å).In the case of compounds Vb and 3c the crystal was mounted on a fibre under oil and then cooled on the diffractometer. In the case of 1a and 2a crystals were mounted in Lindemann tubes under nitrogen which were then sealed with a small flame. For all structures the positions of the heavier atoms were determined by direct methods using SIR 92.24 Subsequent Fourier-difference syntheses revealed the positions of the other non-hydrogen atoms. Non-hydrogen atoms were refined with anisotropic thermal parameters by full-matrix least-squares procedures on F. Hydrogen atoms were fixed in geometrically idealised positions and allowed to ride on their attached carbon atoms with isotropic thermal parameters according to the atom to which they were attached (these were not refined).Absorption corrections were applied using DIFABS.25 Chebyshev weighting schemes 26 were applied in the refinement of all the structures; in all cases the data were corrected for the effects of anomalous dispersion and isotropic extinction (via an overall extinction parameter) 27 in the final stages of refinement. All crystallographic calculations were performed using the Oxford CRYSTALS system28 running on a Silicon Graphics Indigo R4000 computer. Neutral atom scattering factors were taken from the usual sources.29 The figures were produced using CAMERON.30 For compound Vb systematic absences clearly indicated P21/ n. Inspection of the residual electron density after the final refinement showed peaks primarily around the crown ether as well as one peak suggesting disorder of the methyl group attached to C(1); the latter disorder methyl was modelled successfully using two sites and refining their occupancies whilst constraining the total occupancy to be 1.However attempts to model disorder of the crown ether did not give chemically realistic bond lengths nor did it improve the overall fit of the model; the disorder is therefore simply reflected by the large thermal ellipsoids of some of the crown ether atoms. Presumably the unresolved disorder is responsible for the high R values. In the case of compound 2a systematic absences could not J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3871 unambiguously identify the space group; solution and refinement were therefore carried out in both P21 and P21/m. Refinement in the former space group gave chemically unreasonable lengths and angles.A much more satisfactory refinement was achieved in the latter space group. However in P21/m the [SbF6]2 ion lies on an inversion centre whilst the cation is bisected by a crystallographic mirror plane. This requires disorder of the indacene ring system about the mirror plane; the 5 and 7 positions are superimposed. Fourier maps showed this disorder could not be satisfactorily resolved. Thus the out-ofplane 5- and in-plane 7-methyl groups were represented by a single carbon at an intermediate position. CCDC reference number 186/683. Results and Discussion Ligand synthesis We wanted our synthesis for 1,2,3,4,5,6,7,8-octamethyl-1,5- dihydro-s-indacene to be cheap and straightforward compared to pre-existing routes to various dihydro-as-31–35 and s-indacene systems 35–40 and to dihydropentalene,41 hoping it would lead to an expansion of the field of fused-ring chemistry.The route we adopted is shown in Scheme 1; it is based on a modification of previously described preparations of 1,3-dimethylindene,42 1,2,3-trimethylindene 42,43 and 1,2,3,4,5,6,7-heptamethylindene. 44–46 The aluminium chloride-catalyzed reaction of tiglyl chloride 45 and p-xylene in carbon disulfide produced moderate yields of 2,3,4,7-tetramethylindan-1-one I as a colourless liquid. Proton NMR spectroscopy revealed the presence of two isomers in Scheme 1 (i) MeCH]] CMeCOCl AlCl3 CS2 then concentrated HCl; (ii) MgMeI light petroleum (b.p. 40–60 8C) then concentrated HCl H Me H Me Me H O Me H Me H O Me Me H H O Me Me H H H Me O Me H Me H H Me + + a b d c e h f g j i a b c d e f g h i j Ia II IIIa Ib IIIb IV ( ) ( ) ( ) i ii ii ( ) i an approximate ratio of 3:1.Examination of the coupling constants suggests that the major isomer is Ia. Similar isomerism is observed in 2,3,4,5,6,7-hexamethylindan-1-one prepared by the analogous reaction of tiglyl chloride and 1,2,3,4- tetramethylbenzene with aluminium chloride in dichloromethane. 47 We have found sieve-dried dichloromethane gives similar results in place of carbon disulfide in this type of Friedel–Crafts acylation reaction.48 1,2,3,4,7-Pentamethylindene II is a waxy solid and was obtained in excellent yield through the methylation of 2,3,4,7- tetramethylindan-1-one I with a light petroleum suspension of methylmagnesium iodide. This reaction was carried out in an analogous fashion to the procedure described for the methylation of 2,3,4,5,6,7-hexamethylindan-1-one.46 The methylation of 2,3,4,5,6,7-hexamethylindan-1-one has also been achieved by the use of methyllithium in either diethyl ether 45 or light petroleum.46 However use of methyllithium often leads to greatly varying yields due to competitive enolisation of the ketone which is then recovered after the aqueous work-up.46 The same problems occur with methyllithium in the present reaction.49 The reaction of tiglyl chloride and 1,2,3,4,7-pentamethylindene II was carried out in an analogous fashion to that with and p-xylene; moderate yields of the ketone III were obtained. Four readily distinguishable isomers may be envisaged differing in the relative disposition of the functionalities in the two five-membered rings and in the con- figurations of the chiral centres in the ketone ring.Additional isomers arising from different configurations of the chiral centre in the indene ring relative to those in the ketone ring would not be expected to be distinguishable by spectroscopic techniques. Proton and 13C NMR spectroscopy show two isomers are present in the reaction product in an approximate ratio of 2 1; these were separated and purified by fractional recrystallisation. The relative disposition of the functionalities in the two five-membered rings was shown by nuclear Overhauser effect spectroscopy (NOESY) experiments to be the same for both isomers. In both isomers the C]] C group of the indene ring was shown to be bonded to the benzene ring para to the C]] O of the ketone group i.e.the two isomers are IIIa and IIIb in Scheme 1. The difference between the NMR spectra of the two isomers is reminiscent of that found between the isomers of 2,3,4,7-tetramethylindan-1-one and between those of 2,3,4,5,6,7-hexamethylindanone both with respect to the difference in chemical shifts and the different coupling patterns of the ketone ring CH protons in the two isomers. This is consistent with both isomers having the same relative dispositions of indene and ketone rings as shown by the NOESY experiments but differing in the relative configurations of the chiral centres in the ketone ring. Again the coupling patterns suggest the major isomer is that with the two methyl groups in the ketone ring trans to one another (IIIa). This assumption is confirmed by the NOESY experiments.Compound IV (H2L1) was obtained in moderate yield by the methylation of its ketone precursor III; in analogy with the methylation of 2,3,4,7-tetramethylindan-1-one a light petroleum slurry of methylmagnesium iodide was used. The number of resonances observed in the 1H and 13C NMR spectra indicates the isomer is that with a C2 axis perpendicular to the plane of the molecule i.e. 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-sindacene rather than that with a plane of symmetry perpendicular to the plane of the molecule i.e. 1,2,3,4,5,6,7,8- octamethyl-1,7-dihydro-s-indacene. Further isomerism can arise from different relative configurations of the chiral centres in the two five-membered rings; however it is unlikely these isomers could readily be distinguished by NMR spectroscopy since the two centres are so distant as to have little effect on one another.1,2,3,4,5,6,7,8-Octamethyl-1,5-dihydro-s-indacene shows surprisingly low solubility in common organic solvents; it is 3872 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 most soluble in aromatic and halogenated solvents but even so the solubility in boiling toluene is only ca. 40 g l21. Synthesis and characterisation of organometallic derivatives Deprotonation of compound IV. Most organometallic indacene chemistry has involved the reaction of as- or sindacene dianions or the hydro-s-indacene anion.5,32,35,50–52 In general these anions are derived from deprotonation of the corresponding dihydroindacene although the dianion of sindacene has also been obtained by the reduction of s-indacene with sodium in liquid ammonia.37 For example Manríquez’s compounds were made from dilithio-s-indacene and [MII(h- C5Me5)(acac)] (M = Fe Co or Ni; acac = acetylacetonate).3–5,53 (We have recently discovered another route to such compounds the reaction of neutral 1,3,5,7-tetra-tert-butyl-s-indacene (H2L2) with [CoI(h-C5H5)(C2H4)2] yields [{Co(h-C5H5)}2(H2L2)] remarkably as a mixture of cis (major) and trans (minor) isomers.54,55) Hence attempts were made to prepare mono- and di-lithium salts of compound IV by reaction with appropriate quantities of n-butyllithium or tert-butyllithium in thf. The use of LiBun with or without added N,N,N9,N9-tetramethylethane-1,2- diamine (tmen) gave only the monoanion while LiBut gave no reaction at all. Unlike potassium which reacts with IV at room temperature freshly cut lithium metal does not react in refluxing 1,2-dimethoxyethane (dme) or thf.Reaction of solutions of the monolithiated material with compounds such as FeCl2?1.5thf and [Mn(CO)3(py)2Br] gave no tractable products. It was suspected that this chemistry was unsuccessful partly because any lithiated materials formed were strongly reducing. Therefore it was decided to synthesize a potassium salt of IV which might be expected to be less reducing. Refluxing a thf slurry of compound IV with either an excess of potassium hydride or of molten potassium metal led to disappearance of IV and formation of red solutions. Filtration and solvent removal afforded golden solids Va. Surprisingly given the relatively harsh conditions employed for the deprotonations 1H and 13C NMR spectra (C6H6) were entirely consistent with the formation of [K]1[HL1]2?xthf (x = ca.0.1) in both potassium hydride and potassium metal reactions with no evidence for formation of [L1]22. The use of toluene instead of thf did not enable isolation of the dipotassium salt. The use of 18-crown-6 did not aid formation of the dianion. However we were able successfully to isolate crystals of [K]1[HL1]2?18- crown-6 Vb and determine its crystal structure (see below). Reaction with LiBun–KOBut Schlosser’s base in light petroleum gave unselective deprotonation of the methyl groups without abstraction of both ring protons. The compound [K]1[HL1]2?0.1thf is much more soluble in solvents such as thf and benzene than is IV itself. Attempts to crystallise Va from these solvents by cooling or by precipitation with pentane gave oils which solidified upon complete solvent removal.It is possible that the increased solubility of Va relative to IV is related to favourable p-stacking interactions between the molecules of IV which are disrupted by metallation allowing the solubilising effect of the methyl groups to dominate. [Mn(Á5-HL1)(CO)3]. The reaction of compound V with [Mn(CO)3(py)2Br] gave moderate yields of orange [Mn(h5- HL1)(CO)3] 1 (Scheme 2) which we could then compare with other Mn(CO)3 species to assess the effect of methylation on the indacene ligand system. We chose [Mn(CO)3(py)2Br] 22 as a ‘[Mn(CO)3]1’ synthon as it has previously been found to be less easily reduced than [Mn(CO)5Br]. The reaction of [Mn(CO)3(py)2Br] with lithium or potassium reagents has previously been used to obtain Mn(CO)3 complexes of asindacene 52 trindene (2,3,4,5,6,7,8,9-octahydro-1H-cyclopentas- indacene) 56 and truxene (10,15-dihydro-5H-diindeno- [1,2-a:19,29-c]fluorene).57 Two isomers of compound 1 are possible depending whether the methyl group of the CHCH3 unit is on the same (endo) or opposite (exo) face of the indacene ring system as the manganese moiety.Cooling the saturated light petroleum extracts of the crude reaction product to 280 8C gave an approximately 1:1 1a to 1b isomer mixture (according to 1H NMR spectroscopy). Subsequent recrystallisations revealed 1a to be the less soluble isomer indicating 1b is probably the major product with more remaining in solution in the initial crystallisation. As X-ray crystallography (see below) identifies 1a to be the endo isomer it is not surprising that 1b is formed as the major isomer as it would be expected to be both kinetically and thermodynamically favoured.Interestingly the manganese complex is much more soluble in common organic solvents than is the parent hydrocarbon; the solubility of 1 in light petroleum (b.p. 40–60 8C) at 20 8C is approximately the same as that of IV in boiling toluene. Again this may reflect disruption of p-stacking interactions by complexation of the metal fragment. The 13C NMR spectrum of 1a shows a single carbonyl resonance (at d 227.3 in C6D6); this is usual for Mn(CO)3 complexes and reflects the rapid reorientation of the Mn(CO)3 unit relative to the indacene ring. The 13C NMR CO resonance of 1b occurs at a very similar shift to that of 1a. The infrared spectrum of compound 1 in dichloromethane shows two intense carbonyl stretching bands at 1914 and 2001 cm21 the former of which is rather broad.Two bands are generally seen for [Mn(h-C5H5)(CO)3] complexes but in principle three should be observed for indenyl-type com- Scheme 2 (i) K or KH thf reflux; (ii) [MnCO3(py)2Br] thf; (iii) [Rh(h-C5Me5)(Me2CO)3]212[SbF6]2 acetone; (iv) [Cr(CO)3(NH3)3] p-dioxane reflux Me Rh H Me H Me H Me Cr OC CO OC Me H Mn OC CO OC H Me Mn OC CO OC Me H Me H H H Cr OC CO OC Me H Me H Cr OC CO OC H Me Me + – K+ + SbF6 + + i ii iii iv ( ) ( ) ( ) ( ) Ia 3c 3a 3b Ib IV V 2a – J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3873 plexes owing to raising of the degeneracy of the antisymmetric pair of vibrations. However as shown in Table 1 this splitting is not necessarily observed in practice.The complexes tricarbonyl(5-hydro-s-indacene)manganese (s-indacene)-bis- (tricarbonylmanganese) 35 and (2,7-dimethyl-as-indacene)- bis(tricarbonylmanganese) 52 have been reported by Smart’s group. The last compound is unusual among bimetallic indacene compounds in that it is formed as a mixture of cis (minor) and trans (major) isomers; the crystal structure of the cis isomer features an indacene ring system significantly distorted from planarity due to steric repulsion between the two Mn(CO)3 moieties. Table 1 compares the stretching frequencies for 1 with those of Smart’s compounds including the close analogue tricarbonyl(5-hydro-s-indacene)manganese and also with other Mn(CO)3 species. The lower values seen for 1 reflect the weakening of the C]O bonds through more back-bonding owing to the more electron-donating HL1 ligand.The difference between the hydro-s-indacene and HL1 are similar to those between the C5H5 and C5Me5 species. [Rh(Á5-HL1)(Á-C5Me5)]1[SbF6]2. This compound was synthesized by following a procedure adapted by Bickert and Hafner61 from one originally described by Maitlis and coworkers. 62 They showed that solutions of [{M(h-C5Me5)Cl2}2] (M = Rh or Ir) react with silver salts to give species formulated as [M(h-C5Me5)(solv)3]21 (solv = solvent) which react with arenes to give [M(h-C5Me5)(h6-arene)]21 salts.62 When the arene is an indene derivative the product may be [M(h-C5Me5)- (h6-C9H8)]21; alternatively loss of H1 and migration of the (h-C5Me5)M can lead to [M(h-C5Me5)(h5-C9H7)]1 salts. In some cases the loss of H1 may be reversed by addition of strong acid.The balance between h6-indene and h5-indenyl co-ordination depends on the substitution pattern of the indene and whether the metal is rhodium or iridium. Bickert and Hafner61 extended the reaction to three dihydro-sindacenes although (h5-hydro-s-indacene)(h-pentamethylcyclopentadienyl) rhodocenium hexafluoroantimonate was obtained [with no evidence for any formation of (h6-dihydros- indacene)(h-pentamethylcyclopentadienyl)rhodocenium bis- (hexafluoroantimonate)] two 2,6-disubstituted s-indacenes gave the h6 products. In general it appears that electrondonating substituents on the five-membered ring of an indene or indacene impedes the formation of h5 complexes. Thus the reaction of IV with [Rh(h-C5Me5)(Me2CO)3]21 was carried out to see whether methylation of both five- and six-membered rings would lead to h5 or h6 products.The poor solubility of IV in acetone is presumably responsible for the rather slow rate of reaction as judged by the rate of disappearance of the indacene ligand and consequently owing to competing side reactions of the rhodium species the low isolated yield. The product was isolated as an air-stable yellow microcrystalline powder by crys- Table 1 Infrared C]] ] O stretching frequencies for selected Mn(CO)3 derivatives L (a) In [MnL(CO)3] C5H5 C5Me5 Indenyl Fluorenyl 5-Hydro-s-indacene HL1 (Isomer mixture of 1) (b) In [{Mn(CO)3}2L] trans-s-Indacene trans-2,7-Dimethyl-asindacene cis-2,7-Dimethyl-asindacene Medium Cyclohexane Hexane Cyclohexane Cyclohexane CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 n& CO/cm21 1953 2018 1928 2017 1940 1949 2030 1944 2027 1930 2004 1914 2001 1945 2004 1942 2012 1926 1958 2008 2028 Ref.58 59 60 60 35 This work 35 52 52 tallisation from the reaction mixture elemental analysis and NMR spectroscopy showed it to be [Rh(h5-HL1)(h-C5Me5)]1- [SbF6]2 2. Proton and 13C NMR spectroscopy show compound 2 is formed as a single isomer (shown to be the endo isomer 2a by X-ray diffraction see below). A possible explanation of why the major isomer is the (5-endo-CH3) assumes that IV occurs as a statistical (1 1) mixture of two isomers differing in whether the 1- and 5-methyl groups are on the same or opposite sides of the ring system. It may also be assumed following from previous work on the reaction of indenes and dihydroindacenes with ‘(h- C5Me5)Rh21’,61,62 that co-ordination of the (h-C5Me5)Rh initially occurs in h6 fashion to the central ring.By analogy with the synthesis of [Cr(h6-H2L1)(CO)3] (see below) a 1:1:2 mixture of endo/endo exo/exo and endo/exo isomers of [Rh(h6- H2L1)(h-C5Me5)]21 would be expected. Subsequent migration of the rhodium fragment might be expected to occur towards the less-hindered five-membered ring. In the endo/exo isomer where there is a choice the endo isomer of [Rh(h5-HL1)- (h-C5Me5)]1 would be expected to be formed. The net result would be a 1 3 exo to endo ratio from which it is not surprising that the pure endo isomer is isolated by crystallisation from the reaction mixture. An interesting feature of the 13C NMR spectrum of 2 is the coupling to 103Rh (100% I = ��� ) of the C5Me5 ring carbon resonance and of the resonances corresponding to the indacene ring carbon atoms bound to rhodium.Unfortunately no 13C NMR data for (h5-5-hydro-s-indacene)- (h-pentamethylcyclopentadienyl)rhodium are available for comparison; however the Rh]C coupling constants are similar in magnitude to those reported for [Rh(h5-C9H7)(h-C5Me5)]1- [PF6]2 and for [Rh(h5-C9H5Me2-4,6)(h-C5Me5)]1[PF6 2].61 Table 2 compares the 1H NMR shift of the C5Me5 methyl groups of 2 in (CD3)2CO with those of other indenyl and hydroindacene ligands; the upfield shift of the resonance of 2 again demonstrates the electron richness of the HL1 ligand. [Cr(Á6-H2L1)(CO)3]. The preparation of the yellow Cr(CO)3 complex of H2L1 3 was carried out in an analogous fashion to that of [Cr(h6-C9HMe7)(CO)3].63 Compound 3 is only the third reported h6 derivative of an indacene system (the other two complexes are Bickert and Hafner’s rhodium compounds) 61 and the first to be structurally characterised (see below).This complex could be a useful precursor for the construction of trimetallic indacene complexes and of cis-bimetallic indacene complexes. Doubly deprotonating 3 and treating with a ‘[(h- (C5H5)M]1’ synthon one could envisage both (h-C5H5)M units complexing to the opposite face of the ligand from the chromium moiety which might be removable at a later stage. In a preliminary investigation we carried out the reaction of 3 with 2 equivalents of LiBun in thf at 0 8C quenching with SiMe3Cl. The 1H NMR spectrum of the crude product showed no resonances corresponding to Me3Si-containing products. However Ceccon and co-workers 63–65 have found haptotropic shifts of the chromium tricarbonyl moiety to be a complication in the deprotonation reactions of [Cr(h6-C9H8)(CO)3] and various substituted derivatives; careful choices of base and temperature were necessary to circumvent their problems.Proton and 13C NMR spectra of compound 3 show all three possible isomers to be present; the spectra are consistent with Table 2 Proton NMR chemical shifts in (CD3)2CO for the C5Me5 resonances of selected complexes [RhL(h-C5Me5)]1X2 L h5-Indenyl h5-4,6-Dimethylindenyl h5-2-Methylindenyl h5-5-Hydro-s-indacene h5-HL1 X2 [PF6]2 [PF6]2 [SbF6]2 [SbF6]2 [SbF6]2 (2a) d 1.86 1.82 1.82 1.83 1.70 Ref. 62 62 61 61 This work 3874 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 an approximate 1:1:2 mixture of endo/endo exo/exo and endo/ exo isomers which is the situation that would occur if IV exists as an approximately 1 1 mixture of the two diastereomers possible and if complexation to chromium is unselective.This is however somewhat different from the situation reported for heptamethylindene the chromium complex of which is formed in a 19o to endo ratio.63 The 13C NMR spectrum of an isomeric mixture shows a single carbonyl resonance a single peak at d 236.4 in CDCl3 (d 236.7 in C6D6) presumably because of the very similar shifts for the three isomers. This is almost identical to the CO shift of the heptamethylindene analogue where the two isomers are observed at d 235.7 and 236.0 in CDCl3. The IR spectrum of a thf solution shows strong C]] ] O bands at 1863 and 1941 cm21.In Table 3 these data are compared with carbonyl stretching frequencies for a number of other [Cr(h6-arene)(CO)3] complexes. Two C]] ] O stretching modes are expected for such species; a symmetric and a twofold degenerate antisymmetric combination.68 In principle significant distortion of the complex from pseudo-axial symmetry should lead to lifting of the degeneracy of the antisymmetric pair of vibrations. However three bands are only observed in practice for severely distorted species generally where another aromatic ring is fused to the arene e.g. the rhodium–chromium bimetallic in Table 3. A notable trend among the data in Table 3 is the decrease in nCO with increasing electron richness of the ligand (e.g. compare the benzene and hexamethylbenzene complexes); this may be attributed to increased electron density at the metal and consequently stronger Cr]CO back bonding weakening the C]] ] O bonds.The frequencies for 3 are very similar to those for [Cr(h6-C9HMe7)(CO)3] as are the 13C NMR shifts of the carbonyl groups indicating the two ligands have very similar electron-donating abilities in this situation. Crystal structures of organometallic H2L1 derivatives We have determined the single-crystal structures of the alkaliand transition-metal derivatives of compound IV (Vb 1a 2a and 3c) discussed above. Crystallographic details are given in the Experimental section. Views of the structures of are shown in Figs. 3 (Vb) 4 and 5 (1a) 6 (2a) and 7 (3c); whilst selected bond lengths and angles are given in Tables 5–9. The molecular structure of compound Vb is shown in Fig.3. The potassium ion is sandwiched between the crown ether and the deprotonated five-membered ring of the [HL1]2 anion; this is similar to the arrangement in [Li]1[C5H5]2?12-crown-4 (12- crown-4 = 1,4,7,10-tetraoxacyclododecane).69 The unresolved disorder associated with the crown ether means that the details of its co-ordination to the potassium ion cannot be meaningfully discussed. The co-ordination of the potassium ion to the Table 3 Infrared C]] ] O stretching frequencies for selected [Cr(h6- arene)(CO)3] derivatives h6-Arene h6-C6H6 h6-C6Me6 h6-Naphthalene h6-Styrene h6-Indene h6-Fluorene (1-endo)h6-1,2,3,4,5,6,7- Heptamethylindene (1-exo) * h6-H2L1 (isomeric mixture of 3) Medium Cyclohexane Cyclohexane Cyclohexane Cyclohexane thf thf thf thf thf thf CH2Cl2 n& CO/cm21 1917 1987 1888 1962 1905 1918 1977 1913 1980 1898 1975 1892 1966 1862 1943 1866 1945 1851 1861 1937 1863 1941 1844 1934 Ref.66 66 66 19 67 67 63 63 63 This work This work * trans-[(h4-cod)Rh(m-h5 :h6-C9Me7)Cr(CO)3] where cod = cycloocta- 1,5-diene. hydrooctamethylindacene anion which can be regarded as an elaborate indenide ion is somewhat distorted from ideal h5 geometry with two relatively long and three relatively short bonds. However the pattern of long and short bonds is different to the slippage towards a h3-allyl/benzene type structure which has been observed in many transition-metal indenyl complexes (see below) and in [Li]1[C9H7]?tmen;70 in Vb the slippage appears to be towards a structure where the potassium is bound to one of the ring junction carbons and to two non-junction carbons.Since the potassium–anion interaction is presumably largely ionic and hence not strongly directional it is possible that the packing constraints of the other portions of the molecule rather than any electronic factor are responsible for this distortion. The K]C distances 3.007(5)–3.363(6) (average 3.194 Å) (Table 5) may be compared to those in [K]1- [C5Me5]2?2py [polymer with m-h5 :h5-C5Me5 units; K]C 2.962(2)–3.104(2) average 3.034 Å],71 [K]1[C5H4SiMe3]2 [polymer with m-h5 :h5-C5H4SiMe3 units; K]C 2.988(10)–3.079(10) average 3.03 Å] 72 and [K]1[C5(CH2Ph)5]2?3thf [monomeric ‘piano stool’ structure; K]C 2.968(5)–3.095(5) average 3.035 Å].73 The longer K]C distances in Vb may be at least partly due to the separation of the ion pair induced by the crown ether; comparison of the structures of [Li]1[C5H5]2?12-crown-4 (average Li]C 2.380 Å) 69 and [Li]1[C5H4Me]2?tmen (average Li]C 2.26 Å) 74 reveals an analogous effect.Whilst many crystal structures of covalent transition-metal indenyl derivatives have been published until recently structures of the more ionic indenides of Groups 1A and IIA were limited to those of [M]1[C9H7]2?tmen (M = Li 70 or Na 75) and of [Mg]212[C9H7]2.76 More recently the structures of [Ca]21- 2[C9H7]2?2thf [Sr]212[C9H7]2?thf [Ca]212[C9H5Pri 2-1,3]2?thf and [Ba]212[C9H5Pri 2-1,3]2?thf have been published.77 The lithium compound is monomeric with the lithium sandwiched between the tmen and the indenide anion which is slightly slipped towards an h3 allyl/benzene structure whilst the sodium compound is a polymer with Na(tmen) units sandwiched between bridging h1 :h2 indenide ions.Both polymeric and bis(indenide) sandwich structures are found among the alkaline earths. The pattern of bond lengths in the [HL1]2 anion in Vb is similar to that in the other Group IA and IIA indenides. A notable feature is the greater length of the ring-junction bond [1.471(7) Å] relative to the other C]C bonds of the deprotonated five-membered ring [1.378(8)–1.415(7) Å]. This effect (which is a general feature of the more covalent transitionmetal indenyl complexes) is common to the other alkali- and alkaline-earth-metal indenides apart from the magnesium species but it is most pronounced in Vb perhaps due to the degree of separation of the ion pair effected by the crown ether. The effect can be understood by examining the highest occupied molecular orbital (HOMO) of the indenide anion (illustrated for example by Rhine and Stucky) 70 which features an antibonding interaction between the two ring-junction atoms.The structures of compound 1a and 2a both display typical Fig. 3 View of the molecular structure of compound Vb in the crystal showing 50% thermal ellipsoids J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3875 Table 4 Details of the crystal structure determinations Formula M Crystal appearance Crystal size/mm Diffractometer T/K Crystal class Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z Dc/g cm23 m/cm21 F(000) q Limits/8 Total data measured Total unique data No. least-squares parameters No. observed data * R R9 Vb C32H49KO6 568.84 Orange plate 0.10 × 0.25 × 0.40 Enraf-Nonius DIP 2000 150 Monoclinic P21/n 9.836(1) 16.634(1) 19.384(1) 97.446(2) 3144.71(1) 4 1.20 2.0 1233 0–26 33 499 6913 362 3920 0.087 0.080 1a C23H25MnO3 404.39 Orange-yellow block 0.54 × 0.60 × 0.81 Enraf-Nonius CAD4 298 Orthorhombic Pbca 13.824(4) 15.920(4) 18.493(4) 40 70(1) 8 1.32 6.4 1689 0–25 4958 3559 245 1752 0.053 0.058 2a C30H37F6RhSb 736.27 Yellow plate 0.09 × 0.36 × 1.05 Enraf-Nonius CAD4 298 Monoclinic P21/m 8.961(19) 17.535(2) 9.530(18) 10.611(8) 1471.9(3) 2 1.66 15.3 734 0–29 4898 3965 185 2752 0.042 0.049 3c C23H26CrO3 402.45 Yellow block 0.16 × 0.24 × 0.32 Enraf-Nonius DIP 2000 170 Triclinic P1� 7.502(4) 9.522(4) 14.789(6) 101.125(3) 91.559(3) 111.629(3) 963.24(1) 2 1.39 6.0 424 0–26 17 416 3718 245 3236 0.051 0.059 * For compound Vb reflections with I > 6s(I) were used; for 1a and 2a and 3c those with I > 3s(I).features of covalent h5-indenyl species both show two long and three short metal–ring C distances the long bonds being those to the ring-junction carbons. Representative examples of this Fig. 4 View of molecule 1a in the crystal structure showing 50% thermal ellipsoids Table 5 Selected bond lengths (Å) and angles (8) for [K]1[HL]2?18- crown-6 Vb K1]C(5) K]C(11) K]C) K]C(12) K]C(7) C(1)]C(2) C(1)]C(9) C(2)]C(3) C(3)]C(10) C(4)]C(10) C(6)]C(5)]C(11) C(5)]C(6)]C(7) C(6)]C(7)]C(12) 3.007(5) 3.114(5) 3.148(6) 3.338(5) 3.363(6) 1.50(1) 1.536(8) 1.324(9) 1.467(8) 1.437(8) 108.0(5) 110.6(5) 108.1(5) C(4)]C(11) C(5)]C(6) C(5)]C(11) C(6)]C(7) C(7)]C(12) C(8)]C(9) C(8)]C(12) C(9)]C(10) C(11)]C(12) C(5)]C(11)]C(12) C(7)]C(12)]C(11) 1.418(7) 1.395(8) 1.415(7) 1.378(8) 1.406(8) 1.339(8) 1.421(8) 1.420(8) 1.471(7) 106.0(5) 107.3(5) phenomenon may be found in the structures of various Mn(CO)3 species compared in Table 7 and in the structures of bis(h5-1,3-dimethylindenyl)iron hexafluorophosphate [short M]C 2.063(4)–2.079(4) Å; long M]C 2.142(4)–2.156(4) Å],81 (h5-indenyl)(h4-norbornadiene)rhodium [2.224(5)–2.240(5) 2.388(3)–2.401(3) Å],65 bis(h5-indenyl)dimethylzirconium [2.502(5)–2.513(5) 2.600(5)–2.622(5) Å] 82 and (h5-heptamethylindenyl) titanium trichloride [2.352(4)–2.360(4) 2.383(4)– 2.400(4) Å].83 The bond-length alternation in the six-membered rings of both 1a and 2a is also typical of h5-indenyl structures.The C]C bonds in the co-ordinated five-membered rings of both compounds are longer than those of Vb paralleling differences seen between alkali- and transition-metal indenyl species.Several structural parameters for compound 6a are compared with those for other Mn(CO)3 complexes in Table 7. Interestingly the asymmetry of the bonding as measured by the difference of ra and rb (defined in Table 7) is significantly lower than in the 1-bromoindenyl and s-indacene complexes of Mn(CO)3 although not as low as that of the structurally characterised 2,7-dimethyl-as-indacene complex. The Mn]CO bond Fig. 5 Packing diagram for compound 1a 3876 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 lengths for 1a fall in the range 1.743(6)–1.766(6) Å; these are significantly shorter than in most other Mn(CO)3 complexes listed in Table 7. For example its closest relative tricarbonyl- (5-hydro-s-indacene)manganese has M]CO bond lengths in the range 1.772(6)–1.800(6) Å.The C]O bond lengths are correspondingly longer in 1a [range 1.160(7)–1.167(7) Å] than in most of the other complexes [range for tricarbonyl(5-hydros- indacene)manganese 1.143(5)–1.152(5) Å]. The differences in Mn]CO and C]O bond lengths between the hydro-s-indacene complex and its octamethylated analogue parallels that between the cyclopentadienyl and pentamethylcyclopentadienyl complexes. In each case the electron-donating effect of the methyl groups is evidently sufficient to lead to appreciably stronger metal d–CO p* back bonding and consequent shortening of the Mn]CO bonds and lengthening of the C]O bonds. The isomer 1a is presumably both thermodynamically and Fig. 6 View of the cation 2a in the crystal structure showing 50% thermal ellipsoids primes denote symmetry-generated atoms.Ring positions 5 and 7 refer to the carbon atoms labelled 9 and 99 Fig. 7 View of the molecule 8c in the crystal structure showing 50% thermal ellipsoids Table 6 Selected bond lengths (Å) and angles (8) for compound 1a Mn]]C(1) Mn]C(3) Mn]C(5) Mn]C(7) Mn]C(20) Mn]C(21) Mn]C(22) Mn]C(23) O(1)]C(21) O(2)]C(22) O(3)]C(23) C(1)]C(3) C(1)]C(20) C(3)]C(1)]C(20) C(1)]C(3)]C(5) C(3)]C(5)]C(7) C(5)]C(7)]C(20) 2.125(5) 2.137(5) 2.128(5) 2.185(5) 2.197(5) 1.763(7) 1.743(6) 1.766(6) 1.160(7) 1.167(7) 1.164(7) 1.397(8) 1.437(8) 108.6(5) 109.7(5) 106.9(5) 107.6(4) C(3)]C(5) C(5)]C(7) C(7)]C(8) C(7)]C(20) C(8)]C(10) C(10)]C(11) C(10)]C(17) C(11)]C(13) C(13)]C(15) C(15)]C(17) C(17)]C(18) C(18)]C(20) C(1)]C(20)]C(7) Mn]C(21)]O(1) Mn]C(22)]O(2) Mn]C(23)]O(3) 1.414(8) 1.454(8) 1.438(7) 1.439(7) 1.352(7) 1.488(7) 1.429(8) 1.317(8) 1.515(9) 1.514(8) 1.351(8) 1.437(8) 107.0(5) 178.0(6) 177.9(5) 178.4(7) kinetically disfavoured due to steric considerations compared to 1b.It is the least soluble and most easily crystallised of the two isomers. Crystallisation may be facilitated in 1a as the unencumbered face of the indacene ligand can pack against that of another molecule with favourable p–p interactions; this may be seen in the packing diagram Fig. 5. Compound 3a is only the third rhodocenium species to be structurally characterised. The others are [Rh{h5- C5H2(CO2Me)3-1,2,3}2]1[C5(CO2Me)5]284 and the bimetallic species m-h5 :h5-fulvalenebis[(pentamethylcyclopentadienyl)- rhodium].85 The Rh]C5Me5 ring C distances in 2a range from 2.161(6) to 2.182(4) (average 2.177 Å) and the Rh]HL1 bonds range from 2.174(5) to 2.217(4) (average 2.194 Å); these are similar to the Rh]C bond lengths for [Rh{C5H2(CO2Me)3- 1,2,3}2]1 [ 2.15(2)–2.19(2) average 2.17 Å] and those for the isoelectronic ruthenocenes e.g.[Ru(C5Ph4H)2] 86 has an average Ru]C distance of 2.20 Å. The bimetallic fulvalene species has average Rh]C bond lengths of 2.186 Å to the fulvalene ligand and 2.156 Å to the C5Me5.85 The neutral rhodocene [Rh(C5Ph4H)2] has significantly longer Rh]C distances ranging from 2.220(9) to 2.307(9) (average 2.26 Å) as the nineteenth electron resides in an orbital with some antibonding character. 87 The differences between rhodocene and rhodocenium species parallel those observed between cobaltocenes {e.g. [Co(C5Ph4H)2] 88 has an average Co]C bond length of 2.152 Å} and cobaltocenium salts {2[Co(h-C5Me5)2]1[tcne]22 (tcne = tetracyanoethylene) 89 is a typical example with an average Co]C bond length of 2.052 Å}.Interestingly the pentamethylcyclopentadienyl ring and the h5-indacene ring in compound 2a completely eclipse one another whereas in both the fulvalene compound85 and [Rh{C5H2(CO2Me)3-1,2,3}2]1[C5(CO2Me)5]284 the two rings are staggered (presumably staggering is necessary in the last case to prevent steric interference between the rather bulky ester substituents). In compound 3c the C]O bond lengths fall in the range 1.158(5)–1.161(4) Å (Table 9) whilst the Cr]CO bond lengths fall in the range 1.830(4)–1.834(4) Å. These are similar values to those reported for other electron-rich [Cr(h6-arene)(CO)3] complexes; for example for the hexamethylbenzene complex Cr]CO and C]O bonds are in the ranges 1.832(3)–1.840(3) and 1.155(5) Å respectively.90 For the benzene species Cr]CO and C]O bonds were found in the range 1.841(1)–1.842(2) and 1.157(2)–1.159(2) Å (according to a 77 K X-ray study; results from 92 K neutron data are very similar).91 The effect of electron-releasing methyl groups on the bond lengths of the Cr(CO)3 is evidently considerably less pronounced than that seen in Mn(CO)3 complexes (see below).The Cr]HL1 bond lengths are similar to those seen in other [Cr(h6-arene)(CO)3] complexes. Bond-length alternation has been observed in the arene rings of [Cr(h6-C6H6)(CO)3] (by diffraction methods in the crystal 91 and by microwave spectroscopy in the gas phase) 92 and [Cr(h6-C6Me6)(CO)3] (in the crystal).90 In 3c the C]C bond lengths in the h6 ring vary from 1.405(5) to 1.424(5) Å; however no bond-length alternation is found.This is perhaps unsurprising in view of the conformation of the Cr(CO)3 moiety relative to the ring (see below) and the possible effects of the ring substituents. The torsion angles given in Table 9 show that the Cr(CO)3 unit is ca. 218 away from an ideally staggered conformation (i.e. ca. 98 away from being perfectly eclipsed) with respect to the six-membered ring of H2L1. In this particular conformation one of the CO groups must lie more or less under one of the CHCH3 groups; this is found to be the exo-CH3 group [C(13)] thus avoiding steric interference with the endo-CH3 group. The Cr(CO)3 units of the heptamethylindene analogue of 3c and two heterobimetallic derivatives are all ca.4–58 from the ideal staggered conformation.63 Those of the benzene 90,93,94 and hexamethylbenzene 91,95 species are rigorously and essentially perfectly staggered respectively whilst that of the hexaethylbenzene compound is almost perfectly staggered.96 J. Chem. Soc. Dalton Trans. 1997 Pages 3867–3878 3877 Table 7 Comparison of some average bond lengths (Å) for some Mn(CO)3 derivatives L ra a/Å rb b/Å rc c/Å rd d/Å re e/Å Ref. (a) [MnL(CO)3] C5H5 2.138 1.407 1.793 1.144 78 C5Me5 2.129 1.387 1.729 1.175 79 1-Bromoindenyl 5-Hydro-s-indacene HL1 (1a) 2.128 2.119 2.130 2.213 2.214 2.191 1.42 1.414 1.428 1.793 1.788 1.757 1.14 1.149 1.164 80 35 This work (b) [{Mn(CO)3}2L] trans-s-Indacene cis-2,7-Dimethyl-asindacene 2.127 2.143 2.249 2.181 1.429 1.440 1.797 1.787 1.142 1.140 35 52 a Average manganese–non-ring-junction ring C distance.b Average manganese–ring junction ring C distance. c Average C]C distance in ring bound to Mn. d Average Mn]CO distance. e Average C]O distance. Electronic and intramolecular steric arguments have been used to explain the conformations of Cr(CO)3 complexes in many cases;97 however in other cases such as a series of pdisubstituted species studied by Gilbert et al.,98 such arguments were found to be insufficient and intermolecular steric (i.e. crystal-packing) arguments had to be invoked. Conclusion We have developed a convenient route to a new fused-ring permethylated ligand 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-sindacene (H2L1). We have shown that mononucelar organometallic complexes may be formed from it by several different routes.Spectroscopic and crystallographic data indicate both h5-HL1 and h6-H2L1 ligands to be strongly electron donating. Table 8 Selected bond lengths (Å) and angles (8) for compound 2a; primes denote atoms generated by symmetry Rh]C(1) Rh]C(3) Rh]C(5) Rh]C(13) Rh]C(15) Rh]C(17) C(1)]C(3) C(3)]C(5) C(3)]C(1)]C(39) C(1)]C(3)]C(5) 2.174(5) 2.181(4) 2.217(4) 2.161(6) 2.180(4) 1.282(4) 1.422(6) 1.453(5) 109.7(5) 107.5(4) C(5)]C(59) C(5)]C(6) C(6)]C(8) C(8)]C(89) C(13)]C(15) C(15)]C(17) C(17)]C(179) C(3)]C(5)]C(59) 1.447(7) 1.436(5) 1.364(6) 1.448(9) 1.437(7) 1.426(7) 1.45(1) 107.6(2) Table 9 Selected bond lengths (Å) angles and torsion angles (8) for compound 3c; CEN is the centroid of the six-membered ring Cr]C(4) Cr]C(8) Cr]C(9) Cr]C(10) Cr]C(11) Cr]C(12) Cr]C(20) Cr]C(21) Cr]C(22) O(20)]C(20) O(21)]C(21) O(22)]C(22) C(1)]C(2) C(10)]C(4)]C(11) C(9)]C(8)]C(12) C(8)]C(9)]C(10) C(4)]C(10)]C(9) C(4)]C(11)]C(12) C(20)]Cr]CEN]C(4) C(21)]Cr]CEN]C(12) 2.304(3) 2.269(2) 2.228(2) 2.253(2) 2.257(2) 2.255(2) 1.836(3) 1.837(3) 1.834(3) 1.160(4) 1.151(4) 1.154(4) 1.511(4) 116.8(2) 115.7(2) 123.4(2) 120.2(2) 122.6(2) 9.6(1) 9.0(9) C(1)]C(9) C(2)]C(3) C(3)]C(10) C(4)]C(10) C(4)]C(11) C(5)]C(6) C(5)]C(11) C(6)]C(7) C(7)]C(12) C(8)]C(9) C(8)]C(12) C(9)]C(10) C(8)]C(12)]C(11) Cr]C(20)]O(20) Cr]C(21)]O(21) Cr]C(22)]O(22) C(22)]Cr]CEN]C(9) 1.515(3) 1.345(4) 1.489(3) 1.423(4) 1.410(3) 1.518(4) 1.510(3) 1.344(4) 1.496(3) 1.418(5) 1.418(3) 1.420(4) 121.2(2) 178.4(2) 179.4(2) 179.1(3) 8.7(9) Unfortunately the synthesis of L1-based polymetallic species has been hampered by the difficulty of doubly deprotonating H2L1.Acknowledgements We thank the EPSRC for support and studentships (to S. 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ISSN:1477-9226
DOI:10.1039/a703598e
出版商:RSC
年代:1997
数据来源: RSC
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