Structural trends in a series of bulky dialkylbiarylphosphane complexes of Cu^I

Cu^I complexes containing the bulky dialkylbiarylphosphane 2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl (^tBuXPhos, L) and an ancillary ligand (Cl^-, Br^-, I^-, MeCN, ClO₄^- or SCN^-) have been structurally characterized, namely, chlorido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuCl(C₂₉H₄₅P)], 1, bromido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuBr(C₂₉H₄₅P)], 2, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]iodidocopper(I), [CuI(C₂₉H₄₅P)], 3, (acetonitrile-κN)[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I) hexafluoridophosphate, [Cu(CH₃CN)(C₂₉H₄₅P)]PF₆, 4, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP](perchlorato-κO)copper(I), [Cu(ClO₄)(C₂₉H₄₅P)], 5, and di-μ-thiocyanato-κ²S:N;κ²N:S-bis{[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I)}, [Cu₂(NCS)₂(C₂₉H₄₅P)₂], 6. Iodide complex 3 shows significant Cu^I-arene interactions, in contrast to its chloride 1 and bromide 2 counterparts, which is attributed to the weaker interaction between the iodide ion and the Cu^I centre. When replacing iodide with an acetonitrile (in 4) or perchlorate (in 5) ligand, the reduced interaction between the Cu^I atom and the ancillary ligand results in stronger Cu^I-arene interactions. No Cu^I-arene interactions are observed in dimer 6, due to the tricoordinated Cu^I centre having sufficient electron density from the coordinated ligands.