Fe2 CO

Fe2(CO)gB2H6 is volatile, and the solvent-free, pure compound (viscous, yellow-brown, oil) can be obtained only by removing the solvent under vacuum at — 15°C or below. The compound is very air-sensitive (but not pyrophoric) in either the pure state or in solution. Further, it can be stored for long periods of time in an inert atmosphere (e.g., N2) at low temperature (e.g., - 20 C). MS, = Fe2 B2 Ce 06 H6+, 307.9048 calculated, 307.9066 observed. The BNMR spectrum in hexane at 25 C shows an apparent broad quartet at 24.4 ppm with Jb-h infrared spec- 

The trinuclear ferraborane, Fe3H(CO),oBH2, can also be obtained from the above procedure for the preparation of Fe2(CO)fiB2 He by employing a 8 1 

Buck and M. S. Brookhart, in Experimental Organometallic Chemistry, A. L. Wayda, and M. Y. Darensbourg (eds.), ACS Symposium Series, American Chemical Society, Washington, DC, 1987, p. 27, 

PREPARATION OF THE METAL- AND HYDROGEN-RICH FERRABORANE Fe3H(CO)gBH4 

Submitted by XIANGSHENG MENG and THOMAS P. FEHI,NER Checked by KENTON H. WHITMIREf 

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Iron forms the carbonyls FelCO),. Fe2(CO)g and FcjlCOlij- In iron pentacarbonyl. the iron(O) is 5-coordinated. as shown in Figure 13.5 to give a trigonal bipyramid the substance is volatile... 

State is similar to that of Fe2(CO)g, with one less bridging CO ligand. 

The deterrnination of the stmcture of Fe (00) 2 proved to be a difficult problem. An early report on the crystal stmcture claimed the molecule was a monoclinic prism and estabHshed the molecular formula (22). In a later report stmcture (8) was shown to be a triangular array of iron atoms with two bridging and 10 terminal CO molecules. This accepted stmcture was initially deduced from an x-ray crystal stmcture of the Fe2(CO)22H analogue (23). 

Syntheses in Solvent Systems. Very few examples of syntheses of metal carbonyls in aqueous solution are reported. An exception is the preparation of Co2(CO)g from CoSO (66% yield) or C0CI2 (56% yield) and CO at 9.6—11 MPa (95—110 atm) in aqueous ammonia at 120°C for 16—18 h (101). Triiron dodecacarbonyl is prepared almost exclusively in aqueous solution. Quantitative yields of Fe2(CO)22 have been obtained by oxidising alkaline solutions of carbonyl ferrates with manganese dioxide (102—104). 

Similarly, reaction of B6H10 with Fe2(CO)9 (p. 1 104) at room temperature results in the smooth elimination of Fe(CO)s to form [Fe(r -B6Hio)(CO)4] as a. stable, volatile yellow solid. Use of these electron-donor propcities of B(,H o towards reactive (vacant orbital) borane radicals resulted in the preparation of several new coti/uncm-boranes. e.g. BnHiy, BuHji and B15H23 (p. 162),... 

Reaction of P4Sc4 with soluble polyselenides afforded the first isolated P/Se anion, the yellow P2Seg (17) which further reacts with Fe(CO)s to generate the novel brown cluster anion [Fe2(CO)4(PSc5)2] (18).Numerous other examples are known indeed, the whole field is still rapidly developing and many new types of compound are being synthesized and characterized each year. 

The treatment of iron carbonyls with aqueous or alcoholic alkali can, by varying the conditions, be used to produce a series of interconvertible carbonylate anions [HFe(CO)4] , [Fe(CO)4] ", [Fe2(CO)g]2-, [HFe3(CO) ]- and [Fe4(CO)i3]"". Of these the first has a distorted trigonal bipyrarmdal stracture with axial H, the second... 

Tlie isolable stable 1,2-dithietaiie, dithiatopazine (73), was prepared in 1988 and fully characterized (the name dithiatopazine was coined for its beautifully yellow-orange topazlike crystalline form) (87JA3801 88JA4856 90JA3029). Tlius, controlled photoirradiation of a dithiono-lactone (117) produced 73 in 65% yield along with an alkene 118 in 12% yield. Photolytic or thermal decomposition of 73 led to the alkene 118, a conversion that could be also carried out by a variety of reagents [m-BusShH-AIBN, Raney Ni, MCPBA, Fe2(CO)9, Mo(CO)6] in excellent yields. 

Benzothiadiborolene with [Fe2(CO)9] and [Fe3(CO)i2] forms species 42, where the annulated benzene ring is not delocalized and behaves like the cyclohexatriene system (75AGE262). 

Dimethyl-l,2,2,3-tetramethyl-A -1,2,5-azasilaboroline with [Fe2(CO)9] gives sandwich 62 and sandwich 63 (82AGE207, 82CB738) with Cp)Co(C2H4)2]. With [Ni(CDT)] or in a vapor phase with metallic nickel, sandwich 64 (M =Ni) is formed. The vapor-phase synthesis with iron gives 64 (M = Fe). In all these sandwiches, 62-64, the j " -coordination of the heterocyclic ligand is realized. 

Ethyl 1//-l,2-diazepine-l-carboxylate (0.50g, 3.1 mmol) in benzene (100 mL) was treated with Fe2(CO)9 (1.50 g, 4.1 mmol) and the mixture was vigorously agitated at 20 C under N2. The mixture was filtered, the filtrate was evaporated and the residue was chromatographed (silica gel, EtOAc/cyclohexane 2 3) to give the product, which was sublimed at 60°C/0.04Torr yellow crystals mp 115 C. (The yield was not reported.)... 

Ley and Middleton synthesized ketone-functionalized lactam complexes 260 (Scheme 2.64) by sonication of vinylaziridines 259 with Fe2(CO)9 in benzene. These complexes were easily converted into the corresponding (3-lactams 261 by stereoselective addition of nucleophiles such as NaBH4 or trialkylaluminium to the carbonyl group followed by decomplexation with Me3NO [96]. 

Vinyloxiranes can also be converted into P-lactones (Scheme 9.30) [133, 134], Opening of 66 with Fe2(CO)9 resulted in the (7t-allyl)tricarbonyliron derivative 67 in good yield, together with a minor diastereomer (not shown). Oxidative cleavage of 67 then gave 3-lactone 68, which was used as a key intermediate in the preparation of the cholesterol biosynthesis inhibitor 1233A. 

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