Robert C. Kerber

The oxidative degradation of some tetracyanoethylene-polyeneiron tricarbonyl adducts

Abstract The tetracyanoethylene adducts with cyclooctatetraeneiron tricarbonyl and with cycloheptatrieneiron tricarbonyl were oxidatively degraded. The organic products, 8,8,9,9-tetracyanotricyclo[5.2.1.0 4.10 ]deca-2,5-diene and 8,8,9,9-tetracyanobicyclo[3.2.2]nona-2,6-diene, are different from those obtained by direct reaction of the polyenes with TCNE; their structures suggest stepwise cycloaddition reactions of the complexes.

REACTIONS OF 1,1,2,2-TETRAMETHYLDISILANE WITH GROUP VIII METAL CARBONYLS

1,1,2,2-tetramethyldisilane reacts with Fe2(CO)9 to yield bis9μ-dimethylsilylene)-μ-carbonyls bis(tricarbonyliron)(FeFe). Reaction with octacarbonyldicobalt analogously gives bis-(μ-dimethylsilylene)bis-(tricarbonylcobalt)(CoCo) as stable product; spectroscopic results also indicate inter alia the formation of (tetramethyldisilyl)tetracarbonylcobalt, μ-(dimethylsilylene)-μ-carbonyl-bis(tricarbonyl)cobalt(CoCo), and cobalt cluster compounds. Reactivity of zerovalent transition metal compounds towars SiSi bonds seems to be greatest for the nickel triad and to decrease as one moves from right to left across the transition series.

Novel organoiron compounds resulting from the attempted syntheses of dibenzofulvalene complexes

Abstract Thermal reaction of 2,2′-biindenyl with Fe(CO) 5 generates (η 4 -2,2′-biindenyl)Fe(CO) 3 and a ferrole isomer of (μ,η 3 :η 3 -dibenzo[b,e]fulvalene)Fe 2 (CO) 6 . Reaction of the dianion of dibenzo[b,e]fulvalene with iron carbonyls produced a novel cyclized acyliron complex, whose structure was proven by X-ray crystallography; a mechanism is proposed for its formation. Reaction of the same dianion with (η 5 -cyclopentadienyl)Fe(CO) 2 Br generated another novel cyclic compound (C 18 H 12 )Fe(CO) 2 (C 5 H 4 ), probably via intramolecular radical attack on the η 5 -bound cyclopentadienyl ring. Treatment of dibenzo[a,d]fulvalene with Fe 2 (CO) 9 generates (η 2 -dibenzo[a,d]fulvalene)Fe(CO) 4 , (μ,η 2 :η 2 -dibenzo[a,d]fulvalene)Fe 2 (CO) 8 , and two compounds with bis(η 5 ) structures. These appear to have CO and Fe(CO) 4 groups inserted into the reactive Fe–Fe bond of (μ,η 5 :η 5 -dibenzo[a,d]fulvalene)Fe 2 (CO) 4 .

Structure and reactivity of (Dibenzo[b,e]fulvalene)Mo2(CO)6

Abstract The title compound 1 was prepared by a one pot double-deprotonation, migration, and oxidation sequence staring with ( μ , η 6 : η 6 -2,2′-biindenyl)Mo 2 (CO) 6 ( 2 ). An X-ray structure was determined, and the relevant structural features are compared with analogous fulvalene and dibenzo[a,d]fulvalene complexes. The reactions of 1 with 4-octyne and P(CH 3 ) 3 are described. Compound 1 is a more effective catalyst in the Kharasch reaction than other bimetallic molybdenum complexes.

Interaction of organometallic moleties with carbanions and other electron-rich centers

Abstract In this review, I cite literature data which suggest that polyhapto organometallic groups generally provide effective stabilization of β-carbanions through interactions summarized by . These interactions are also discernible in neutral compounds having electron-donor groups X = OH, OR, NR 2 , etc. The same interaction is responsible for the exo stereochemistry generally observed in deprotonation reactions of alkyl-substituted organometallics, and in electrophilic attacks on double conjugated with organometallic groups, the reverse reaction. And it is responsible for the instability of many η 1 -organometallics having acidic β-hydrogens. Wider recognition of the general ability of organometallic groups to stabilize carbanions should lead to broader synthetic exploitation of organometallic compounds.

Hindered rotation and structure in μ-Allylbis(η-Cyclopentadienyldicarbonyliron) cations

Abstract Studies of four μ-allylbis(η-cyclopentadienyldicarbonyliron) cations by IR and variable temperature 1H and 13C NMR indicate unsymmetrical hybrid structures. Rotation about the CC bonds of the μ-allyl moiety requires about 12 kcal (ΔG‡ ); interconversion of nonequivalent iron groups was not frozen out at −90°C.

Valence tautomers of dimethyl cycloocta-2,5,7-triene-1,4-dicarboxylate and an iron tricarbonyl complex therefrom

Abstract Carboxylation of cyclooctatrienyldilithium, Li 2 C 8 H 8 , gives predominantly tricyclo[5.1.0.0 2,4 ]oct-5-ene-3,8-dicarboxylic acid and trans,cis,cis,trans -deca-2,4,6,8,-tetraene-1,10-dioic acid; in addition, a small quantity of cycloocta-2,5,7-triene- trans -1,4-dicarboxylic acid has been identified as its dimethyl ester. The tricyclooctene diester is in equilibrium with a small amount of the isomeric cis -disubstituted cycloocta-2,5,7-triene in solution, and heating such a solution results in formation of a dimer. Reaction of the tricyclooctene diester with iron pentacarbonl produces exo (2–5)η-(3,8×-dicarbomethoxybicyclo[4.2.0]octa-2,4-diene]tricarbonyliron.

Markovnikov's Rule in History and Pedagogy

In 1870–75 Markovnikov enunciatedan empirical Rule which generalized theregiochemical outcome of addition reactions tounsymmetrical alkenes. This Rule remaineduseful for about 75 years, until suchreactions came to be better understood inmechanistic terms. Thereafter the Rule couldbe deduced from principles of relativecarbocation stabilization and ceased to servean independent purpose. Nevertheless, mostorganic textbooks continue to cite it (oftenin a historically inaccurate, anachronisticway), thereby distracting student attentionfrom the underlying principles. This paperadvocates doing away with the Rule in organicchemistry textbooks and classrooms.

Preparation and reactions of [2,2-bis(carbethoxy)propyl]cyclopentadienyldicarbonyliron

Abstract Although , (Fp  η-C 5 H 5 Fe(CO) 2 ) (I) is stable and characterizable, the lower homologue FpCH 2 CH(CO 2 CH 3 ) 2 (II) is not; this we attribute to a facile elimination reaction resulting from the relatively acidic β-hydrogen of II. Formation of I from Fp − and XCH 2 CE 2 CH 3 (X  Br, Cl; E  CO 2 CH 2 CH 3 ) and cleavage of its FeC bonds (using H + , Br 2 , Ce IV and Hg II ) occur without major amounts of ester group migrations, even though ·CH 2 CE 2 CH 3 radicals are involved in some of these reactions.

Reactions of group VIII metal carbonyl anions with 1,2-dichlorotetramethyl-disilane

Abstract Reactions of 1,2-dichlorotetramethyldisilane with transition metal carbonyl anions, NaCo(CO) 4 and Na 2 Fe(CO) 4 , proceed easily to give monodisplacement products. Thus, reaction with NaCo(CO) 4 yields a neutral chlorodisilanyl cobalt complex, Cl(CH 3 ) 2 Si(CH 3 ) 2 SiCo(CO) 4 , and the analogous reaction chlorodisilanyltetracarbonylferrate salt, [Cl(CH 3 ) 2 Si(CH 3 ) 2 SiFe(CO) 4 ] − Na + . The β-chloride of Cl(CH 3 ) 2 SiCo(CO) 4 was unreactive toward BCl 3 . Prolonged reaction with CaCo(CO) 4 resulted in formation of the cluster compound, (CO) 9 Co 3 COSi(CH 3 ) 2 Si(CH 3 ) 2 Co(CO) 4 and of bis(μ-dimethylsilylene)bis(tricarbonylcobalt)(CoCo).