TY - JOUR
T1 - Functionally substituted arylcopper compounds
T2 - Synthesis, structure, and reactivity of (2-(2-oxazolinyl)aryl)copper(I) species
AU - Wehman, Erik
AU - Van Koten, Gerard
AU - Jastrzebski, J. T B H
AU - Rotteveel, Marc A.
AU - Stam, Casper H.
PY - 1988
Y1 - 1988
N2 - Arylcopper(I) compounds containing an oxazoline substituent in the position ortho to the Cu-C bond have been synthesized from the corresponding aryllithium compounds and CuBr. Depending on the order of addition this reaction afforded either a pure arylcopper(I) compound (slow addition of CuBr to the aryllithium reagent) or a mixture of arylcopper(I) and its CuBr adduct with [(RCu)2CuBr]2 stoichiometry (addition of aryllithium to a CuBr suspension). The new arylcopper(I) compounds were characterized by 1H NMR spectroscopy and cryoscopic molecular weight determinations in benzene, and for two of them the X-ray crystal structure has been determined. The structure of [Cu(MeOXL)]2 (MeOXL = 2-(4,4-dimethyl-2-oxazolinyl)-5-methylphenyl) (2b) (monoclinic crystals of space group P2/n, Z = 8, with a = 19.050 (1) Å, b = 6.671 (1) Å, c = 18.927 (1) Å, and β = 106.49 (1)°) shows a dimeric molecule containing a bridging 2-(2-oxazolinyl)aryl moiety, with two-center, two-electron carbon-copper bonds (Cu-C = 1.899 (5) Å). The oxazoline substituent is coordinated via the nitrogen with a Cu-N distance of 1.902 (4) Å. Such a two-center, two-electron bridge bonding mode is unprecedented in arylcopper chemistry. The CuBr adduct of 2b [Cu2(MeOXL)2CuBr]2 (triclinic crystals of space group P1, Z = 2, with a = 13.661 (3) Å, b = 19.154 (4) Å, c = 11.666 (5) Å, α = 95.46 (3)°, β = 92.49 (3)°, and γ = 110.49 (3)°) also shows a dimeric structure containing six copper atoms which form a distorted octahedron with four three-center, two-electron bridging aryl groups (Cu-C = 2.031 (3) Å (mean); Cu-Cu = 2.436 (3) Å (mean)) and two three-center, four-electron bridging bromine atoms (Cu-Br = 2.524 (3) Å (mean); Cu-Cu = 3.023 (4) Å (mean)). The oxazoline substituent is coordinated via the nitrogen atom (Cu-N = 1.968 (4) Å (mean)). Ullmann biaryl coupling reactions of the new organocopper(I) compounds with 2-iodopiperonal imine were little influenced by a hetero substituent in either the arylcopper(I) compound or the aryl iodide anchoring group. Moreover, since the addition of P(OMe)3 did not influence the coupling reaction, it can be concluded that "external" ligands do not have a critical role in these reactions. The results of this study show clearly the important influence that an ortho-chelating substituent (i.e. the 2-oxazolinyl group in the present compounds) can have on both the structural features and the reactivity of the arylcopper compounds.
AB - Arylcopper(I) compounds containing an oxazoline substituent in the position ortho to the Cu-C bond have been synthesized from the corresponding aryllithium compounds and CuBr. Depending on the order of addition this reaction afforded either a pure arylcopper(I) compound (slow addition of CuBr to the aryllithium reagent) or a mixture of arylcopper(I) and its CuBr adduct with [(RCu)2CuBr]2 stoichiometry (addition of aryllithium to a CuBr suspension). The new arylcopper(I) compounds were characterized by 1H NMR spectroscopy and cryoscopic molecular weight determinations in benzene, and for two of them the X-ray crystal structure has been determined. The structure of [Cu(MeOXL)]2 (MeOXL = 2-(4,4-dimethyl-2-oxazolinyl)-5-methylphenyl) (2b) (monoclinic crystals of space group P2/n, Z = 8, with a = 19.050 (1) Å, b = 6.671 (1) Å, c = 18.927 (1) Å, and β = 106.49 (1)°) shows a dimeric molecule containing a bridging 2-(2-oxazolinyl)aryl moiety, with two-center, two-electron carbon-copper bonds (Cu-C = 1.899 (5) Å). The oxazoline substituent is coordinated via the nitrogen with a Cu-N distance of 1.902 (4) Å. Such a two-center, two-electron bridge bonding mode is unprecedented in arylcopper chemistry. The CuBr adduct of 2b [Cu2(MeOXL)2CuBr]2 (triclinic crystals of space group P1, Z = 2, with a = 13.661 (3) Å, b = 19.154 (4) Å, c = 11.666 (5) Å, α = 95.46 (3)°, β = 92.49 (3)°, and γ = 110.49 (3)°) also shows a dimeric structure containing six copper atoms which form a distorted octahedron with four three-center, two-electron bridging aryl groups (Cu-C = 2.031 (3) Å (mean); Cu-Cu = 2.436 (3) Å (mean)) and two three-center, four-electron bridging bromine atoms (Cu-Br = 2.524 (3) Å (mean); Cu-Cu = 3.023 (4) Å (mean)). The oxazoline substituent is coordinated via the nitrogen atom (Cu-N = 1.968 (4) Å (mean)). Ullmann biaryl coupling reactions of the new organocopper(I) compounds with 2-iodopiperonal imine were little influenced by a hetero substituent in either the arylcopper(I) compound or the aryl iodide anchoring group. Moreover, since the addition of P(OMe)3 did not influence the coupling reaction, it can be concluded that "external" ligands do not have a critical role in these reactions. The results of this study show clearly the important influence that an ortho-chelating substituent (i.e. the 2-oxazolinyl group in the present compounds) can have on both the structural features and the reactivity of the arylcopper compounds.
UR - http://www.scopus.com/inward/record.url?scp=0001669625&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0001669625
SN - 0276-7333
VL - 7
SP - 1477
EP - 1485
JO - Organometallics
JF - Organometallics
IS - 7
ER -