Tuning the steric and electronic properties of chiral rhenium thiolate complexes

Reaction of the complex [CpRe(NO)(CO)(2)]BF4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(i-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 complexes [CpRe(NO)(L)(CH3)]. The structure of [CpRe(NO){P(i-Pr)(3)}(CH3)] was determined: triclinic space group <P(1)over bar> (No. 2), a = 8.442(4), b = 9.582(5), c = 11.820(8) Angstrom, alpha = 81.81(4), beta = 87.18(4), gamma = 63.87(5)degrees, 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(i-Pr)(3), R = CH2Ph, CH2(4-C6H4Cl), CH2(4-C6H4OMe), CH3, C2H5). The structure of [CpRe(NO){P(i-Pr)(3)}(SCH3)] was determined: monoclinic space group P2(1) (No. 3), a = 7.0525(7), b = 17.3469(10), c = 7.9727(7) Angstrom, beta = 114.021(7)degrees, 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.