Richard H. Jones

A comparison of trimethylphosphine and tricyclohexylphosphine complexes (η5-C5Me5)Re(CO)(PR3(N2 (R = Me, cyclo-C6H11) in inter- and intra-molecular C-H activation reactions. X-ray structure of the cyclometallated product (η5-C5Me5)Re(η2-C6H10P{C6H11}2)(H)(CO) · 0.5C6H14

Abstract Irradiation of (η 5 -C 5 Me 5 )Re(CO)(PMe 3 )(N 2 ) ( 1 ) in benzene forms trans -(H,Ph)-(η 5 -C 5 Me 5 )Re(CO)(PMe 3 )(H)(Ph) ( 4 ), whereas irradiation in cyclohexane results in intramolecular C-H activation of the PMe 3 group, yielding trans -(H,CH 2 )-(η 5 -C 5 Me 5 )Re(η 2 -CH 2 PMe 2 )(CO)(H) ( 5 ). By contrast, irradiation of (η 5 -C 5 Me 5 )Re-(CO)(P{C 6 H 11 } 3 )(N 2 ) ( 2 ) in benzene does not result in any observable product derived from intermolecular C-H activation of benzene. Instead, intramolecular C-H activation of the tricyclohexylphosphine ligand occurs, as it does when 2 is irradiated in cyclohexane, to give the C-1 ( ipso ) cyclometallated product (η 5 -C 5 Me 5 )Re(η 2 -C 6 H 10 P{C 6 H 11 } 2 )(H)(CO) ( 3 ). The crystal structure of 3 has been determined at 212 K. Distances and angles in the 3-membered metallacycle are Re(1)-P(1) 2.324(6), Re(1)-C(21) 2.27(2), P(1)-C(21) 1.77(3) A, C(21)-Re(1)-P(1) 45.2(8), C(21)-P(1)-Re(1) 65.9(7), P(1)-C(21)-Re(1) 68.9(7)°. Other pertinent dimensions are Re-C(1) 1.75(2), C(1)-O(1) 1.26(2), P(1)-C(31) 1.84(2), P(1)-C(41) 1.86(2) A, Re(1)-C(1)-O(1) 1.76(2), C(31)-P(1)-Re(1) 117.4(7), C(31)-P(1)-C(21) 114.2(10), C(41)-P(1)-Re(1) 126.2(7), C(21)-P(1)-C(41) 114.1(9) and C(31)-P(1)-C(41) 110.8(10)°. The hydride ligand was not located but it is reasoned to be in a position pseudo- trans to the phosphorus atom in a four-legged piano stool structure; there was no observable 2 J (HP) coupling for the hydride resonance in the 1 H NMR spectrum.

Dimethyl 4b,8b,8c,8d-Tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene-8b-carboxylate-8c-thionocarboxylate and the Corresponding 8c-Thiolocarboxylate

The title compounds, methyl 8c-[methoxy(thiocarbonyl)]-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene-8b-carboxylate, C 20 H 16 O 3 S, and methyl 8c-[(methylthio)]carbonyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene-8b-carboxylate, C 20 H 16 O 3 S, are the photoproducts in the photolysis of the dibenzobarrelene thiono and thiolo esters. The geometry and dimensions of the molecules are similar to those of related materials. Only one photoproduct (of two possible) is formed in each case, with initial vinyl-benzo bond formation involving the vinyl C atom carrying the non-thioester group ; intermediate biradicals are stabilized by resonance interaction with the thioester groups.

Methyl 8c-Phenyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene-8b-carboxylate

The title molecule, C 24 H 18 O 2 , is the sole product of photolysis of a phenyl-methoxycarbonyl-dibenzobarrelene derivative, has a dibenzosemibullvalene structure, 8c-phenyl and 8b-methoxycarbonyl substituents, and normal bond lengths and angles.

N,N-Diethyl-N'-methyl-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd]pentalene-8b,8c-dicarboxamide

The title compound, C 23 H 24 N 2 O 2 , is a product of photolysis of an unsymmetrical dibenzobarrelene diamide and has a dibenzosemibullvalene structure with normal molecular geometry and dimensions. Molecules are linked by one N-H...O hydrogen bond.

Structures and photochemistry of 1,5-disubstituted dibenzobarrelenes

The effect of 1,5-disubstitution on the photochemistry of 9,10-ethenoanthracene-11,12-diesters has been studied and correlated with the crystal structures determined for several derivatives ; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. The crystals studied are : (1)-Cl, dimethyl 1,5-dichloro-9,10-dihydro-9,10-ethenoanthracene-1,12-dicarboxylate, C 20 H 14 Cl 2 O 4 , P2 1 /n ; (1)-CN, 1,5-dicyano derivative, C 22 H 14 N 2 O 4 , P2 1 /n ; (1)-CN.0.5p-xylene, C 22 H 14 N 2 O 4 .0.5C 8 H 10 , P21/c ; (1)-CN.xxylene, C 22 H 14 N 2 O 4 .xC 8 H 10 , P2 1 /n ; (1)-OMe, 1,5-dimethoxy derivative, C 22 H 20 O 6 , P1 ; (2b)-Cl, C 20 H 14 Cl 2 O 4 , dimethyl 1,5-dichloro-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[c,d]pentalene-8c,8d -dicarboxylate, Pna2 1 . The dibenzobarrelene molecules all have geometries and dimensions similar to those of related materials. In particular, the orientations of the two ester groups in each molecule differ, one being in general almost fully conjugated with the C(11)=C(12) double bond and the other almost non-conjugated. Relationships are sought between the ratios of the two regioisomeric photoproducts and molecular and crystal structures ; both electronic and steric effects are considered, but no one effect seems to dominate.

α- and γ-Polymorphs of Dimethyl 9-Chloromethyl-9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate

Two further polymorphic forms (α = P2 1 and γ = P2 1 /c) of the title compound (C 21 H 17 ClO 4 ) have been obtained and their crystal structures determined. The molecular geometries and photochemical behaviour are very similar to those of the previously described β-form reported in the P2 1 /c space group [Chen, Pokkuluri, Scheffer & Trotter (1993). Acta Cryst. B49, 905-909].

Crystal structure and photochemistry of dimethyl 1,4-dihydro-1,4,5,8-tetramethyl-1,4-ethenonaphthalene-2,3-dicarboxylate

The photochemical rearrangement of a bridgeheadmethylated 1,4-ethenonaphthalene has been studied by crystal structure analyses of (1b) and two of its photoproducts (2b and 3b). Crystal data: T=295 K, Cu Kα, λ=1.54178 A, C 20 H 22 O 4 , M r =326.39. Dimethyl 1,4-dihydro-1,4,5,8-tetramethyl-1,4-ethenonaphthalene-2,3-dicarboxylate (1b), P2 1 c, a=12.643 (1), b=9.288 (1), c=15,153 (1) A, β=105.70 (1) o , Z=4, R=0.037 for 1974 reflections with I>3σ(1). Dimethyl 2a,2b,6b,6c-tetrahydro1,2b,3,6-tetramethylbenzo[a]cyclopropa[c,d]pentalene-6b,6c-dicarboxylate (2b), Pca2 1 , a=7.325 (1), b=14.781 (1), c=15.535 (1) A, Z=4, R=0.045 for 1419 reflections