Suzuki C oupling, C op per(I) C om p lex, X -R ay D ataA synthetic route to 6,6'-d im esityl-2,2'-bipyrid in e is presented that involves a Suzuki c o u pling o f 6,6'-d ib rom o-2,2'-b ip yridin e with m esityl boronic acid. The new sterically crow ded ligand is in vestigated by X -ray analysis and its coordination behavior in the p resence o f co p p er(I) is exam in ed .
A three-step preparation of the benzofluorene core is presented. The last step involves thermal cyclization of 3 -ene-1,6 -diyne (7) leading to the formation of four benzofluorene derivatives, one of which has been investigated by X-ray analysis. The harsh thermal conditions indicate that the cyclization of 7 might not proceed via a biradical intermediate as would be anticipated by a mechanistic proposal from Ueda.
Propionitrile complexes fac-[M(CO)(3)(P-P)(NCEt)] (M = Mo (3), W (4); P-P = Ph(2)PCH(2)PPh(2) (a), Ph(2)PC(2)H(4)PPh(2) (b), Ph(2)PC(3)H(6)PPh(2) (c), (S,S)-Ph(2)PCHMeCHMePPh(2) (d), Fe(C(5)H(4)PPh(2))(2) (e)) were synthesized from [M(CO)(3)(NCEt)(3)] and the corresponding diphosphine. Reactions of 3 and 4 with sulfur dioxide initially gave complexes fac-[M(CO)(3)(P-P)(eta(2)-SO(2))] (M = Mo (5), W (6)), which slowly isomerized to mer-[M(CO)(3)(P-P)(eta(1)-SO(2))] (M = Mo (7), W (8)). The structures of 7b and 8b were determined by X-ray crystallography. Both compounds are isostructural (monoclinic, space group P2(1)/n (No. 14)) with almost identical unit cell dimensions (7b, a = 14.511(5) A, b = 12.797(2) A, c = 16.476(6) A, beta = 115.92(2); 8b, a = 14.478(8) A, b = 12.794(3) A, c = 16.442(9) A, beta = 116.01(2)) and molecular geometries. Treatment of either fac-[M(CO)(3)(P-P)(eta(2)-SO(2))] or mer-[M(CO)(3)(P-P)(eta(1)-SO(2))] with diazomethane yielded the sulfene complexes mer-[M(CO)(3)(P-P)(eta(2)-CH(2)SO(2))] (M = Mo (9), W (10)). The structure of 10a was determined crystallographically: monoclinic, space group P2(1)/n (No. 14), a = 11.719(2) A, b = 17.392(4) A, c = 13.441(3) A, beta = 95.58(2). The tungsten atom resides in the center of a distorted pentagonal bipyramid. The sulfene ligand occupies two adjacent equatorial sites with the bond distances W-C, 2.322(13) A, W-S, 2.353(3) A, and S-C, 1.721(12) A. The latter equals the S-C single bond distance in thiirane S,S-dioxide, indicating a high degree of charge density transfer into the LUMO of the sulfene ligand.
Reaction of the chiral racemic complex [CpRu(mppe)(SO2)]PF6 (1, mppe = Me2PC2H4PPh2) with diazomethane or ‐ethane gave the sulfene complexes [CpRu(mppe)(RHC/SO2)]PF6 (R = H, 2a; R = Me, 2b). Treatment of 2a with prochiral enamines or deprotonated β‐oxo esters yielded C–C coupling products with 32–60% de. An analog of 2a, [NmcpRu(mppe)(H2C/SO2)]PF6 (8, Nmcp = neomenthylcyclopentadienyl) was prepared in a four‐step synthesis starting from LiNmcp and [RuCl2(PPh3)3]. Repeated crystallization of the intermediate [NmcpRu(mppe)Cl] (6) provided diastereomerically pure 6′ which added methylene stereospecifically to give diastereomerically pure 8′. Compound 8 turned out to be much less reactive towards nucleophiles than 2a, but still added deprotonated ethyl 2‐methyl‐3‐oxobutanoate with 44% de. The chiral, enantiomerically pure sulfur dioxide complex [CpRu(chir)(SO2)]PF6 [10, chir = (S,S)‐Ph2PCHMeCHMePPh2] was synthesized from [CpRu(chir)Cl] and SO2 and was characterized by X‐ray crystallography. Reaction of 10 with diazomethane gave the enantiomerically pure sulfene complex [CpRu(chir)(H2C/SO2)]PF6 (11). Addition reactions of 11 with N‐(1‐cyclopentenyl)morpholine, as well as with various enolates derived from β‐oxo esters or 1,3‐diesters proceeded with high yields and 20–90% de. The structure of a diastereomerically pure addition product, [CpRu(chir)(SO2CH2C(Me){C(O)Me}{C(O)OtBu}] (13d′), was determined crystallographically and was shown to have (R) configuration at the quaternary carbon atom. After alkylation of one of the S/O functions, the sulfinate ligand was cleaved from the metal center by ligand substitution with acetonitrile, and the resulting acetonitrile complex 15 was converted back into 10 by treatment with SO2.
Rhenium Complexes, Thiolate Ligands, Structure Reaction of the complex [CpRe(NO)(CO)2]BF4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(/-Pr)3}(CO)]BF4. The corresponding triphenylphosphite complex [CpRe(NO){P(OPh)3}(CO)]BF4 may be obtained by oxidative CO removal. Reduction of the remaining CO ligand with NaBH4 furnishes the corresponding methyl com plexes [CpRe(NO)(L)(CH3)]. The structure of [CpRe(NO){P(/-Pr)3}(CH3)] was determined: triclinic space group PI (No. 2), a = 8.442(4), b = 9.582(5), c -11.820(8) A, a = 81.81 (4), ß = 87.18(4), 7 = 63.87(5)°, Z = 2. Reaction of the methyl complexes with HBF4 in the presence of thiols gives, after chromatographic workup, the thiolate derivatives [CpRe(NO)(L)(SR)] (L = CO, P(OPh)3, P(/-Pr)3, R = CH2Ph, CH2(4-C6H4C1), CH2(4-C6H4OMe), CH3, C2H5). The structure of [CpRe(NO){P(/-Pr)3}(SCH3)] was determined: monoclinic space group P2i (No. 3), a = 7.0515(7), b = 17.3469(10), c = 7.9727(7) Ä, ß = 114.021(7)°, Z = 2. In both structures, a significant opening of the angle N-Re-X (X = C, S) suggests that antibonding interactions between orbitals of the ligand X and the second-highest MO of the [CpRe(NO)(L)] complex fragment are avoided.
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