I. Description of Lab Jobs
A.Dry Boxes: Regenerate every month and change gloves as well as changing pump oil after each regeneration.
B.Freezers: Defrost and clean out freezers every ___ months.
C.High Vacuum Line and Pump.
D.All Pumps: Change pump oil every 6 weeks on all line pumps, including the filtration pumps for glove boxes, keeping oil stocked in lab.
E.GC: Change tanks (N2 + He) as well as septas and injection port liners, as well as ordering paper for integrators.
F.Solvent Stills: Fill, clean, turn on stills, buy solvents.
G.FTIR, IR Cells, KBr Presses: Maintain IR and cells, order paper and transparencies for plotter and printer. Maintain contact with companies for repair. Backup of computers that operate these IRs.
H.Mettler Balances: Check on and keep area clean near all balances.
I.Electrochem Equip.
J.Hoods: Police the hood areas to keep clean.
K.Chemical Inventory and Cabinets: Police to keep the inventory up to date and enter updates in the computer.
L.Lamps and Photolysis Equip.
M.Base Baths and Ovens: Clean and refill base baths periodically (once every other month as needed), maintain ovens.
N.Rotovap: Maintain rotovap and area.
O.UV-vis and Cells, FTP Cells: UV-vis area is kept neat and UV-vis is kept working and supplied with chart paper. Uv-vis cells should be monitored such that matching cells are available for use. FPT cells should be clean and spare O-rings should be on hand.
P.IBM/Mac Computers: One person assinged to each platform. Duties include: backing up hard drives in SyQuest, purchasing software and upgrades, backing up all new software on floppy disk (be sure to make a separate copy for Cliff and notify him of changes to lab computers), and keeping the computers, printers, and network in running order. This includes supplying toner and paper.
Q.Centrifuge, Sonicator, and Microscope: Individual keeps these items clean and in working order, and keeps areas around these tools neat.
R.Laser System: Person keeps laser in working order, keeps crystal under constant N2, cycles fluid through cooling pumps at least monthly, and keeps area around laser tidy.
S.Wastes: Committee members keep waste containers available to group members, monitor group waste disposal habits making sure members indicate contents they add to waste containers, and prepare waste containers for disposal by REM including calling REM to request pick-up.
T.CAS On-Line: This person is responsible for understanding operation of CAS, making sure it is operational on the Macintosh, teaching other group members how to use CAS, and keeping track of billing.
U.Lab N2: Responsibilities inlcude keeping the lab supplied with "house" N2 for schlenk lines, glove boxes, IR, etc. The auxillary argon or N2 cylinders near each glove box must also be kept operational. At no time for any reason should the N2 levels be allowed to drop to the point that the glove boxes become contaminated. The liquid N2 tank for trap N2 is also maintained by this committee.
V.Glassware Inventory/Repair: Any broken but economically repairable glassware should be taken to the glassblower and returned to appropriate storage location. Committee members should be sure glass is clean before delivery to glassblower, but may commission the individual who broke the item(s) to clean sufficiently. Members should also be aware of glassware inventory and purchase additional glassware as needed.
W.NMR Solvents: This person insures that NMR solvents used by the group are kept in stock. New solvent bottles should be ordered sufficiently in advance so as to never run out of a particular solvent. Primary solvents include CO3CN, CO2Cl2, acetone, benzene, tolnene, CO3, DMSO, THF, D2O, and pyridine.
X.HPLC: Assignment entails keeping the HPLC and related equipment in trouble free, running condition. The area around the HPLC should be kept organized as well. Members of this committee should be familiar with operation of HPLC and prepared to assist other group members in its operation.
Y.Aquisition Committee: Members gather information, discuss with company representatives, and inform the research group of details concerning purchase of capital equipment.
II. Our Favorite Molecules
A. Preparation of μ-methylene Diphosphine Ligands
1. Bis(dichlorophosphino)methane (dcpm)
CH2I2
Al + CH2Cl2 → Cl2AlCH2AlCl2
CH2Cl2
Cl2AlCH2AlCl2 + PCl3 + POCl3 → Cl2PCH2PCl2 + 2"Cl3PO:AlCl3"
Procedure
Caution. The aluminum and phosphorous chloride compounds are extremely water sensitive. This preparation should be carried out in a good fume hood with appropriate precautions.
Two 1 L three-neck round bottom flasks, equipped with magnetic stirrers, magnetic stir bars, reflux condensers, and rubber septa, were charged with Al foil (16.2 g each, 0.60 mol, cut into 2 x 2 cm sections). The apparatus were evacuated and filled with nitrogen. The CH2Cl2 (~500 mL, dried over CaH2 and degassed) was added to each apparatus via a stainless steel cannula. The mixtures were heated to reflux at which time CH2I2 (~2 mL each) was added via syringe to initiate the reaction. More CH2I2 may be needed if it is noticed a reaction has not started after several hours. The mixtures were refluxed until all of the Al foil had reacted (12-24 h) to give dark amber solutions of Cl2AlCH2AlCl2 (dcam). The dcam solutions were allowed to cool to room temperature and any insoluble material was allowed to settle out. Do not allow the dcam solutions to sit for extended periods of time since dcam will precipitate out.
A 2 or 3 L three-neck round bottom flask equipped with a mechanical stirrer, reflux condenser, and septum was evacuated and filled with nitrogen. To this apparatus was added PCl3 (MCB, 104 mL, 1.2 mol, degassed) and CH2Cl2 (~300 mL, dried and degassed). The dcam solutions were slowly added via cannula over a period of 1-2 h. None of the solids produced in the dcam reactions were added. During addition, the CH2Cl2 starts to reflux from the exothermic reaction between dcam and PCl3. After addition, the mixture was refluxed 2-3 h then cooled to room temperature. The POCl3 (Fischer Scientific, 112 mL, 1.2 mol, degassed) was slowly added via cannula over a period of 1 h. This addition was also accompanied by an exothermic reaction causing the CH2Cl2 to reflux. The mixture was refluxed for 3-4 h then cooled to room temperature. Any solids present were allowed to settle out. The remaining solution was transferred to a 1 L one neck round bottom flask and concentrated on a rotary evaporator equipped with a nitrogen supply. The solid remaining in the reaction flask was thoroughly washed with ~200 mL portions of CH2Cl2. The extract solutions were added to the original solution. The solution was concentrated down to a paste. The brown paste was vacuum distilled to remove all volatiles. Distillation was continued until AlCl3, from the decomposition of Cl3PO:AlCl3, began to sublime. The distillate was redistilled under nitrogen to remove any CH2Cl2 and PCl3 present. The POCl3 was removed under reduced pressure (0.5 mm Hg) at 25°C. The Cl2PCH2PCl2 (dcpm) was distilled at 45-50°C/0.5 mm Hg to give 35-40 mL (44-50%) colorless liquid.
Caution. Care should be taken when cleaning up the residues from the dcam and dcpm reactions. Slowly react the residue first with isopropyl alcohol then with H2O behind a safety shield.
Properties
The product exists as colorless to yellow liquid which is air sensitive and highly water sensitive. 1H NMR (CDCl3, TMS int): δ 3.51 (t, JPH = 16.4 Hz). 13C NMR (CDCl3, TMS int): δ 55.6 (t, JCP = 66 Hz). 31P{1H} NMR (CDCl3, 85% H3PO4 ext): δ 175 (s).
References
1.Kubiak, C. P.; Kullberg, M. L.; Lemke, F. R.; RaghuVeer, K. S.; King, C.; Roundhill, D. M. Inorg. Synth. in press.
2.Novikova, Z. S.; Prishchenko, A. A.; Lutsenko, I. F. Zh. Obshchei. Khim. 1977, 47, 775.
3.Ort, M. R.; Mottus, E. H. J. Organomet. Chem. 1973, 50, 47.
2. Bis(dimethylphosphino)methane (dmpm)
Et2O
Cl2PCH2PCl2 + 4CH3MgBr → (CH3)2PCH2P(CH3)2 + 4MgBrCl
Procedure
Caution. Dmpm is extremely air sensitive and must be prepared under very oxygen free conditions. Also, dmpm is a highly toxic compound with an unbearable obnoxious odor. It is absorbed through the skin very rapidly. Inhalation or absorption of this compound, even in minute quantities, causes severe headache, nausea, blurred vision, fainting, rise in body temperature, weakness of limbs, and changes in temperament. It is imperative to handle this compound in an efficient hood and gloves must be used. All vapors from the apparatus must be passed through bromine or sodium hypochlorite solutions before release to hood exhaust.
Methyl magnesium bromide (Aldrich, 142 mL, 0.43 mol, 3 M in diethyl ether) was siphoned under nitrogen into a 3-neck flask containing diethyl ether (100 mL anhydrous, degassed) and fitted with a mechanical stirrer, a Friederichs condenser, and a pressure-equalized dropping funnel. The flask was immersed in a -10 °C) bath. The dcpm (13.4 mL, 0.10 mol) was dropped in slowly, over a period of 0.5 h, while the contents of the flask were stirred. After this addition was complete the bath was removed and the flask was slowly brought to room temperature without interrupting the stirring. The cooling bath was replaced and maintained at -10 - 0°C. A solution of ammonium chloride (47 g) in deoxygenated water (150 mL) was dropped in slowly over a 2 h period without interrupting the stirring.
The solution of ammonium chloride was added to hydrolyze the unreacted Grignard reagent and dissolve the magnesium halides. In one experiment this step was omitted and the yield of dmpm was only 55%. Since dmpm is easily oxidized, the water was thoroughly deoxygenated. In some trials, the magnesium halides did not completely dissolve and acetic acid was added (hydrochloric acid must not be used as it reacts with dmpm).
The stirring was stopped and when the contents of the flask had settled much of the aqueous layer was siphoned out. The remainder of the liquid was transferred to a separatory funnel and separated. The aqueous portion was reextracted with two 100 mL portions of diethyl ether. Diethyl ether was removed by distillation at atmospheric pressure (diethyl ether must not be removed in a flash evaporator to save time as much of the product will be carried over with the ether). The residue was subjected to vacuum distillation. Distillate boiling at 45-50°C/10-15 mm was collected in a flask kept at -78°C. Yield: 12-13 g (88 - 96%).
Properties
The product exists as an extremely air sensitive colorless liquid which fumes on contact with small amounts of oxygen. 1H NMR (CDCl3, TMS int): δ 1.40 (t, 2JPH = 0.7 Hz, CH2), δ 1.08 (t, N = (2JPH + 4JP'H) = 3.0 Hz, CH3). 13C{1H} NMR (CDCl3, TMS int): δ 15.8 (t, JCP = 2 Hz, CH3), δ 34.9 (t, JCP = 20 Hz, CH2). 31P{1H} NMR (CDCl3, 85% H3PO4 ext): δ -56.5 (s).
References
1.Kubiak, C. P.; Kullberg, M. L.; Lemke, F. R.; RaghuVeer, K. S.; King, C.; Roundhill, D. M. Inorg. Synth. in press.
2.Karsch, H. H. Z. Naturforsch. 1983, 38B, 1027.
3.Fild, M.; Heinze, J.; Kruger, W. Chem Ztg. 1977, 101, 259.
B. Preparation of Methyl Isocyanide; CNMe
Dehydration of N-methyl Formamide
CH3NHCHO + p-C6H4Me.SO2Cl + 2C9H7N → CH3NC + 2C9H8N+ + p-C6H4Me.SO3 + Cl-
Caution. Isocyanides are very toxic materials having an extremely obnoxious odor. Methyl isocyanide has a very high vapor pressure and will also polymerize at room temperature over a period of time. It should be stored in glass (reacts with septa) in a freezer.
Procedure. To a 500 mL three neck round bottom flask(a) equipped with a stir bar and heating mantle is added 118 mL (129 g) of quinoline.(b) The temperature of the flask and quinoline is raised to 75 ± 10 °C (this can be monitored by a thermometer positioned between the heating mantle and the flask). During this time, 72.5 g of toluene-p-sulphonyl chloride(c) is added and dissolved in the warm quinoline. N-methyl formamide 14.8 mL (15.0 g) is placed in the addition funnel (Figure 2-1), the system is sealed and placed under a N2 atmosphere by three evacuation/flush cycles. Place system under vacuum [60 mm using a controlled bleed and a manometer, however without use of a manometer, simply pull a full vacuum on the system and shut the vacuum line stopcock off to prevent CNCH3 from collecting in vacuum line trap (do this regularly to keep up vacuum)]. Cool stages 2, 3, and 4 (Figure 2-1) in liquid nitrogen traps.(d) If temperature is now regulated, slowly add the N-methyl formamide dropwise over a 20 min period to the stirred solution. Methyl isocyanide will distill rapidly and be collected in the receiving flask (stage 2). Don't worry about fluxuations in the temperature, self refluxing may drive the temperature to ~90 °C, this means that more quinoline is being driven into the receiving flask. A second bulb to bulb distillation is required anyway. A simple procedure to follow is to simply close off stage 2 and let the CNMe condense into stage 3. Expect yields of 80-90% and select an appropriate receiving flask.(e)
Data: Formula weight 41.05 g mol-1; Density 0.69 g mL-1; IR(neat) à(CN) 2170 cm-1 (previously reported 2166 cm-1); 1H NMR (neat) δ 2.85 (t).
Notes
(a)Scaling up the reaction does not decrease yield. However, a large dead volume in the reaction flask should be maintained to allow vigorous refluxing of the reaction solution. Therefore, increase the size of the three neck flask accordingly; 2 liter round bottom for a scale of 4x ... etc.
(b)Quinoline need not be freshly distilled. However, at least 1/2 the volume used should be from a freshly opened bottle.
(c)Toluene-p-sulphonyl chloride need not be recrystallized, reagent grade is sufficient.
(d)Improvements in yield come from additional vacuum trap stages by preventing loss of already prepared CNCH3. Stage 4 is recommended but not required for high yields; it is simply a precaution. Stages 3 and 4 allow the greatest condensation in stage 2, by regulating vacuum.
(e)Isocyanides can be decomposed by two methods, both of which should be used in clean up. Clean up should be done immediately after isolation of CNCH3 while quinoline is still warm. If allowed to polymerize, glassware is forfeited. Add an equal volume of warm H2O and carefully add H2SO4 to the quinoline solution. This mixture can now be disposed of down a hood drain with a copious amount of water. Rinse glassware with a 50/50 mixture of H2O/bleach then clean glassware in the base bath. Hands should be rinsed quickly with fresh bleach mixture and washed with soap and water.
References
1.Casanova, J.; Schuster, R. E.; Werner, N. D. J. Chem. Soc. 1963, 4280.
C. Preparation of Labeled Methyl Isocyanide
1. Preparation of Methyl 13C-Isocyanide; 13CNMe
K13CN + AgNO3 → Ag13CN + KNO3
Ag13CN + MeI → "Ag(13CNMe)I"
"Ag(13CNMe)I" + 2KCN → 13CNMe + (K2Ag(CN)2)
Silver 13C-cyanide (99% enriched, prepared from K13CN and AgNO3(a), 1.937 g, 0.0144 mol) was placed in a 50 mL Pyrex high-pressure reactor.(b) After addition of 0.90 mL of MeI (99%, 0.0145 mol) by syringe, the reactor was heated with shaking at 70-75°C for two hours. The mixture became a dark brown liquid.(c) Upon cooling to room temperature, a solution of 2.4 g of KCN (0.037 mol) in approximately 6 mL water was added by syringe, and the contents were vigorously shaken until all solids dissolved. The reactor was attached to an empty bubbler trap which is attached to a 100 mL Schlenk flask which served as a trap for 13CNMe. The bubbler trap is used due to the likeliness of the reaction mixture to bump this trap keeps any bumped material from contaminating the final product. The volatiles from the reaction mixture were distilled into the trap (cooled in liquid N2) under vacuum until only a thick paste remained in the reactor. To facilitate distillation, the reactor was warmed by using a water bath at 40-45°C.(d) The trap was warmed to room temperature affording an aqueous solution of 13CNMe.(e) In reactions where large amounts of water are a problem, the 13CNMe can be extracted into CH2Cl2 using 3X 6 ml of CH2Cl2.
Notes
(a)Silver cyanide is prepared by reaction of a stoichiometric amount of KCN and AgNO3 in water. The resulting precipitate is air dried and protected from light prior to use. (Extreme care should be observed when handling KCN and MeNC in view of their high toxicity.)
(b)The reactor was constructed from a thick-walled glass tube to which a "T-tube" teflon stopcock was attached (Figure 2-2).
(c)The mixture was best shaken by continually rolling the tube in the oil bath as often as possible. During this period, the solid mixture gradually turns into a brown syrup but sometimes solidifies upon reaction completion.
(d)Extreme care must be taken to prevent contamination of the distillate by the reaction mixture (which contains excess cyanide) through bumping.
(e)Just as N-methyl formamide can be dehydrated to give MeNC, MeNC can be hydrated to give N-methyl formamide. The hydration is acid and base catalyzed. It is best to seperate the MeNC from the H2O as soon as possible.
(f)KC15N is also commercially available. Using the same techniques as above Me15NC can be prepared.
References
1.DeLaet, D. L.; del Rosario, R.; Fanwick, P. E.; Kubiak, C. P. J. Am. Chem. Soc. 1987, 109, 754.
2.Mottern, J. G.; Fletcher, W. H. Spectrochimica Acta 1962, 18, 995.
2. Preparation of Perdeuteriomethyl Isocyanide; CNCD3
KCN + AgNO3 → AgCN + KNO3
AgCN + CD3I → "Ag(CNCD3)I"
"Ag(CNCD3)I" + 2KCN → CNCD3 + K2Ag(CN)2
The preparation is the same as the preparation of 13CNMe except using CD3I instead of CH3I and KCN instead of K13CN.
D. Preparation of Chloro-1,5-cyclooctadiene Metal(I) Dimer; [MCl(COD)]2 M=Rh,Ir and [RhCl(cod)]2
2MCl3 + 2C8H12 + 2CH3CH2OH → [MCl(C8H12)]2 + 4HCl + 2CH3CHO
Into a 100 mL 3-necked flask equipped with a condenser, a magnetic stir bar, and a heating mantle is added 2.0 g of MCl3.3H2O. The system is flushed with N2 gas and 25 mL of degassed H2O added. It is then heated under N2 while stirring until all the solids are dissolved. Degassed, freshly opened EtOH, 30 mL, is added by a syringe and the mixture is stirred for 3 min. 1,5-Cyclooctadiene (COD), 2 mL, is added to the flask by a syringe and the solution is refluxed under N2 for a period of 18 h - 24 h. The temperature is slowly cooled while a stream of N2 is passed through the solution to decrease the volume of solvent to about 30 mL. The solid is collected by filtration and is washed with water 3 times and dried under vacuum. The solid is brick-red for M=Ir and yellow for M=Rg.
Typical yield is 1.5 g (78%).
Note
For M=Rh, the ratio of 5:1 EtOH/H2O works well.
References
1.Herde, J. L.; Lambert, J. C.; Senoff, C. V. Inorg. Synth. 1974, 15, 18. (M=Ir)
2.Giordano, G.; Crabtree, R. H. Inorg. Synth., 1990, 28, 88. (M=Rh)
E. Preparation of Palladium(I) and Platinum(I) Dinuclear Complexes.
1. Preparation of [Pd2(CNMe)6][PF6]2
PdCl2 + 2NaCl → Na2PdCl4
Na2PdCl4 + xs CNMe → Pd2(CNMe)62+ + 2NaCl
Pd2(CNMe)62+ + xs NH4PF6 → [Pd2(CNMe)6][PF6]2 + NH4+
A solution of PdCl42- was prepared by dissolving PdCl2 (600 mg, 3.4 mmol) and NaCl (600 mg, 10.4 mmol) in 30 mL of water. Methyl isocyanide (0.8 mL, 13.5 mmol) was added and the brown solution immediately turned colorless. The clear solution was allowed to stand for 18 h during which time bubbles of a gas slowly evolved and a bright yellow color developed. A solution containing 1 g (6 mmol) of ammonium hexafluorophosphate was added and the pale yellow product precipitated immediately. The pure crystalline salt was obtained as an acetone solvate following recrystallization from acetone/2-propanol or from acetone/diethyl ether. Acetone-free material was produced by heating the product under vacuum at 60°C for 12 h (yield 70-80%).
Data: Formula weight 749.10 g mol-1; IR[KBr] à(CN) 2236 cm-1; 1H NMR (CD3CN) δ 3.65.
Notes
(a) Work in a hood.
(b)10 h is usually a sufficient standing period (check for yellow color, no bubbles) - longer periods occasionally lead to plating Pd metal. If this happens, work up the solution anyway. The metal may be removed by filtering through Celite before recrystallization.
(c)Recrystallize from acetonitrile/diethyl ether to get acetone free product.
(d)Store product in a desiccator or under N2 (keep away from moisture).
References
1.Boehm, J. R.; Doonan, D. J.; Balch, A. L. J. Am. Chem. Soc. 1976, 98, 4845.
2. Preparation of [Pt2(CNMe)6][BF4]2
K2PtCl4 + 2NaBF4 → Na2PtCl4 + 2KBF4
Na2PtCl4 + xs CNMe + xs NaBF4 → [Pt2(CNMe)6][BF4]2
Potassium tetrachloroplatinate(II) (830 mg, 2 mmol) was added to 10 mL of an aqueous solution saturated with sodium tetrafluoroborate. The mixture was stirred 15 min and filtered to remove the insoluble potassium tetrafluoroborate which formed. The filtrate was treated with methyl isocyanide (0.5 mL, 8.3 mmol) added dropwise with stirring. The pale yellow solution was allowed to stand for 24 h during which time the product formed as white crystals. The mixture was filtered and the solids were washed with water. The filtrate yielded a smaller second crop of crystals during the following 24 h. The combined crops were recrystallized from acetonitrile/ether (yield: 370 mg, 46%).
Data: Formula weight 810.16 g mol-1; IR[KBr] à(CN) 2242 cm-1; 1H NMR (CD3CN) δ 3.51 (12 H), 3.33 (6 H).
Notes
(a)Work in a hood.
(b)Keep solution volume under 10 mL - yield decreases with more dilute solutions.
(c)Add CH3NC very slowly.
(d)If no solid is formed after 24 h, then cool the solution in an ice bath.
(e)Do not expect a 46% yield - usually get about 30%.
(f)Store product in a desiccator or under N2 (keep away from moisture).
(g)Yields over 80% have been obtained when 5-7 mL of sat. NaBF4(aq) solution was used for 1.0 g K2PtCl4. The reaction was cropped first after 2 days stirring and cropped three more times over a course of 1-2 weeks.
References
1.Boehm, J. R.; Doonan, D. J.; Balch, A. L. J. Am. Chem. Soc. 1976, 98, 4845.
3. Preparation of [PdPt(CNMe)6][PF6]2
[Pt(CNMe)4][PF6]2 + Pd2(dba)3.CHCl3 + 4CNMe → [PdPt(CNMe)6][PF6]2
Palladium chloride, 1.05 g (5.92 mmol), was added to hot (ca. 50°C) methanol, 150 mL, containing dba (dibenzylideneacetone) 4.60 g (19.6 mmol) and sodium acetate 3.90 g (47.5 mmol). The mixture was stirred for 4 h at 40°C to give a reddish-purple precipitate and allowed to cool to complete the precipitation. The precipitate was collected by filtration, washed successively with water and acetone and dried in vacuo. The precipitate, 3.39 g, was dissolved in hot chloroform, 120 mL, and filtered to give a deep violet solution. To the solution, diethyl ether, 170 mL, was added slowly. Deep purple needles precipitated. These were removed by filtration, washed with diethyl ether, and dried in vacuo. The complex, m.p. 122-124° dec., satisfying the composition of Pd2(dba)3(CHCl3) was obtained in 80% yield.
Methyl isocyanide (0.32 mL) was added to a filtered solution of 0.313 g of potassium tetrachloroplatinate in 10 mL of water. Immediately a filtered solution of 0.60 g of ammonium hexafluorophosphate in 10 mL of methanol was added. The white precipitate, which rapidly formed, was collected by filtration, washed with water, and vacuum dried. Purification was achieved by recrystallization from acetonitrile, yield 95%: conductivity K0.001 M = 181 cm2 mol-1 ohm-1 (nitromethane); IR [KBr] à(CN) 2308 cm-1; 1H NMR [CD3CN] δ 3.68(s).
To a solution of 125.4 mg (0.193 mmol) of [(CH3NC)4Pt][PF6]2 in 10 mL of acetonitrile was added successively 0.25 mL of methyl isocyanide and 100 mg (0.097 mmol) of solid Pd2(dba)3.CHCl3. The mixture was heated briefly until the solid dissolved to give a clear yellow solution. After filtering, the white product was obtained by addition of diethyl ether and purified by dissolution in acetone and reprecipitation with diethyl ether; yield 94%.
Data: Formula weight 837.79 g mol-1; IR [KBr] à(CN) 2231 cm-1; 1H NMR [CD3CN] δ 3.55 (6 H), 3.44 (9 H), 3.38 (3 H).
References
1.Boehm, J. R.; Doonan, D. J.; Balch, A. L. J. Am. Chem. Soc. 1976, 98, 4845.
2.Ukai, T.; Kawazwra, H.; Ishii, Y. J. Organomet. Chem., 1973, 65, 253.
3.Miller, J.; Balch, A. Inorg. Chem. 1972, 11, 2069.
F. Preparation of Nickel(O) Dinuclear Complexes
1.Preparation of Ni2(CNMe)3(dppm)2
NiCp2 + 4CNMe → Ni(CNMe)4
2Ni(CNMe)4 + 2dppm → Ni2(CNMe)3(dppm)2 + 5CNMe
All manipulations were done under N2. To a solution of NiCp2 (1 g) in ether was added 1.6 mL of CNMe at 0°C. The reaction led to the formation of Ni(CNMe)4 as a light yellow solid. After 1 h, the solid was collected, rinsed with hexane, and dried under vacuum: Yield 80%.
To a suspension of Ni(CNMe)4 in C6H6 was added one equivalent of dppm in C6H6. The reaction solution was stirred for several hours. Part of the solvent was removed under vacuum in order to remove the liberated CNMe. More C6H6 was added and stirring continued. This procedure was repeated at least three times before the solution was concentrated and hexanes added to initiate precipitation. The solution was cooled to -20°C overnight. Ni2(CNMe)3(dppm)2 was isolated and washed with hexane, then MeCN to remove any impurities. Yield 60-70%.
Data: Formula weight: 1008.3; 1H NMR (C7D8, -30 °C) δ 2.44 (s, 3H), 2.55 (s, 6H), 4.31 (m, 4H), 7.2-8.1 (m, 40H); 31P{1H} NMR (C7D8, 25 °C) δ 18.21 (s); IR (toluene) à(CN) 2075, 1717 cm-1.
References
1.DeLaet, D. L.; Powell, D. R.; Kubiak, C. P. Organometallics 1985, 4, 954.
2.DeLaet, D. L.; Fanwick, P. E.; Kubiak, C. P. Organometallics 1986, 5, 1807.
3.Nickelocene is commercially available from Aldrich or can be prepared according to the literature preparation: Barnett, K. W. J. Chem. Educ. 1977, 51 422.
2.Preparation of Ni2(CO)3(dppm)2
Mn
NiBr2 + 2 COD → Ni(COD)2
2Ni(COD)2 + 2dppm + 3CO → Ni2(CO)3(dppm)2 + 2COD
Anhydrous NiBr2, 24 g, was dissolved in 150 mL of ethylene glycol monomethyl ether(methyl cellosolve) by refluxing. The solution was cooled and 50 mL of 1,5-cyclooctadiene and 20 mL of quinoline added. The mixture was cooled to -10°C and 8 g of finely powdered manganese was added under nitrogen with stirring. After a short induction period, the solution turned orange-red (an intermediate complex with quinoline is formed) and after 15-20 min dicyclooctadienenickel(O) began to precipitate. The reaction was continued for about 1 h with stirring, the temperature of the bath being kept between -5 and -10°C. The mixture was filtered under nitrogen then washed first with cold (0°C) methyl cellosolve until the filtrate remained colorless (100-150 mL of solvent), and then with ether cooled at -30°C. The bright yellow solid obtained was dried and consisted of a mixture of dicyclooctadienenickel(O) and residual metallic manganese.
To remove the metal, dicyclooctadienenickel(0) may be crystallized as follows. The crude product is placed on a Buchner funnel under nitrogen and washed with a toluene solution (250 mL) containing 1-2 mL of quinoline and 5-10 mL of cyclooctadiene, kept at 90°C and added in small amounts (80 mL) to the Buchner funnel without sucking; the precipitate was agitated with a glass rod and filtration then carried out by applying a gentle nitrogen pressure from the nitrogen line. The process was repeated until the filtrate remained colorless. The combined filtrates were placed in a flask under nitrogen and immersed in a bath at -70°C. The dicyclooctadienenickel(O) formed was filtered, extensively washed with cold ether (at -30°C) and dried under vacuum. Yield 50-80%.
Freshly prepared Ni(COD)2 was dissolved in THF to which was added 1.1 eq dppm in a small amount of THF. The mixture is stirred for about 20 min and the color of the solution changes from yellow to orange yellow. With the flask under a slight vacuum, 1.5 - 1.6 eq. CO gas is added via syringe. The mixture is stirred for 30 min and stored at -20°C overnight.(a) A small amount of yellow precipitate forms overnight. Warm the reaction solution to 45°C and stir 30 min. Allow the reaction solution to cool to room temperature. The reaction volatiles were removed via vacuum(b) until a large amount of yellow precipitate with a small amount of solvent is left. The yellow precipitate is filtered, washed with ether and dried under vacuum: Yield 80%.
Data: Formula weight 970.22 g mol-1; IR [KBr] à(CO) 1970, 1948, 1781 cm-1; 31P{1H} NMR [CH2Cl2] δ 22.92 ppm; 1H NMR [CD2Cl2] δ 2.61 (m, 2H), 3.42 (m,2H0, 6.92-7.38 (m, 40H).
Notes
(a)During the preparation, there is a possibility of forming a trace amount of Ni(CO)4. The reaction solution is stored in the freezer to prevent any Ni(CO)4 from escaping. Ni(CO)4 is a colorless, highly volatile, highly toxic liquid [b.p. 42.2 °C (760 mm Hg), IR (neat) à(CO) 2022-2038 cm-1].
(b)The reaction volatiles are collected in a liquid N2 cooled trap between the reaction flask and vacuum line. Any Ni(CO)4 is disposed of by treatment of the trap distillate with bromine water until the solution turns orange.
References
1.Franco, G.; Giuseppe, S. J. Organomet. Chem. 1976, 114, 339.