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COMMUNICATIONS TO THE EDITOR
VOl. 81
METAL COMPLEXES WITH 2,2, I-BICYCLOHEPTADIENE
Irradiation of Fe(C0)5 in bicycloheptadiene with sunlight for 5 hours gave, in addition to I and the Sir: unidentified ketone, a solid hydrocarbon, m.p. A recent re-investigation of the interesting metal- 67-68', which, from analysis and molecular weight organic compounds obtained following reaction of determination, appears to be a dimer of bicyclobutadiene and its derivatives with iron pentacar- heptadiene. Similar irradiation of bicycloheptabony1 led Hallam and Pauson' to conclude that diene in the absence of Fe(CO), did not yield this conjugation of the double bonds was an essential compound. feature for the metal-organic bonding. The bondA molybdenum derivative analogous to I was ing was considered to be closely related to that in- obtained after reaction of 1 1 0 ( C 0 ) ~with excess volved in ferrocene and other such sandwich com- bicycloheptadiene. Bicycloheptadienemolybdeplexes rather than that in the various platinous- nuni-tetracarbonyl (11) formed pale yellow plates non-conjugated diene complexes.2 from petroleum ether which were stable in air We now wish to report the formation of coin- (m.p. 76-77'; found: C, 43.6; H, 2.6; 110,33.0). pounds related to the butadiene complexes follow- The infrared spectrum of this compound showed ing reaction of iron pentacarbonyl and molyb- three strong carbonyl peaks a t 4.93, 5.05-52, and denum hexacarbonyl with 2,2,l-bicycloheptadiene. 5.35 p in contrast to the one sharp peak a t 3.1 p In bicycloheptadiene the two double bonds arc showii by ,1Io(CO)6. Both compounds I and I1 not in conjugation but still have a suitable spatial showed medium absorption peaks in the i.0, arrangement for possible interaction with the metal 7.75 and S.5 p regions. atomic orbitals. The butadiene-iron tricarbonyl complexes and The refluxing of Fe(CO)6 with excess 2,2,1- the present compounds I and I1 appear to be bicycloheptadiene for 15 hours and then fractional chemically analogous as far as metal-organic bonddistillation led to the isolation of bicycloheptadiene ing is concerned. I t would seem therefore that iron-tricarbonyl (1) in a 30% yield (b.p. 60.5" a t i t is not the conjugation of the two olefinic bonds, 0.2 mm.; found: C, 52.1; H, 3.7; mol. wt., 221). but a suitable spatial arrangement necessary for Considerable amounts of a higher boiling ketone effective overlap with the metal atomic orbitals were also obtained. The ketone was obtained as which is the essential factor leading to bond white needles from alcohol (m.p. 8 2 " ; found: formation. As mono-olefinic complexes of coniC, 85.1; H, 7.3). The 2,$-dinitrophenylhydrazone parative stability are not known, then the 7r formed orange needles from alcohol (m.p. 186-7" ; orbitals of the diene may not be acting indeFoundC, 64.3; H, 3.3, N, 13.9). pendently. Therefore, as with other sandwich The iron coinpound I is an orange red liquid a t type complexes, the formula given affords a satisroom temperature which solidifies to a yellow crystalline mass below 10". I t is stable when factory representation of the coinpound I ; a stored under nitrogen but is oxidized slowly in air with the deposition of iron oxide. Compound I readily dissolves in cold concentrated sulfuric acid, from which solutions i t can be recovered unchanged on dilution. The solutions in concentrated SUIfuric acid liberate sulfur dioxide when heated. coco co Oxidation of I with ferric chloride liberates bicycloheptadiene, thus proving that prior rearrangement to cycloheptatriene followed by complex formation, similar structure is proposed for compound 11. The author is indebted to the Research Corporasimilar to that in cycloheptatriene molybdenum tion for financial assistance. tricarbonyl, had not occurred.
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F. Hallani and P. L. Pauson, J . Ci7em. SOL.,G12 (195s). (2) J, C h a t t , L. &I. Valarino and I.. If. Venanzi a n d references therein, i b i d . , 21913 (1057). (:1) IC. W. A l x l , M. .A. Bennett a n d G. IViikinson, Pi-oi. Cheiii. .Sur., 152 '1958). (1) B.
DEPARTMENT O F CHEMISTRY UNIVERSITYOF TEXAS ACSTIK, TEXAS K c c ~ r v mJ A S U A R Y 3 , 1'339
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