Tuning the Steric and Electronic Properties of Chiral Rhenium Thiolate Complexes [1]

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.