Reaction of PPN[W(CO)3(dmpe)(SH)] 2 (PPN = Ph3PNPPh3, dmpe = Me2PC2H4PMe2) with aqueous formaldehyde in the presence of trifluoroacetic acid gives the thioformaldehyde complex mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 3 in almost quantitative yield. The isotopomer mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCD2)] 3-D22 was obtained analogously. 3 has a slightly distorted pentagonal-bipyramidal structure with one carbonyl group, two P atoms and the C and S atoms of the thioformaldehyde ligand spanning the pentagonal plane. In solution, 3 is in equilibrium with fac-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 4. The structures and energies of 3 and 4 and their rotamers 3Ⲡand 4Ⲡwere calculated by DFT methods leading to a very good agreement with experimental data. FT-IR and FT-Raman spectra of 3 and 3-D22 were recorded and assigned with the aid of DFT calculations. Calculated vibrational amplitudes emphasize the extensive mixing of modes, particularly in the low-wavenumber region. The HOMO of 3 can approximately be described as a lone-pair at sulfur and
is 0.38 eV higher in energy than that of isomer 4. The LUMOs of both isomers are highly delocalized with that of 4 being 0.45 eV lower in energy. On this basis it is expected that electrophiles will add preferentially at the sulfur atom of 3 while nucleophiles if at all will add to the thiocarbonyl carbon of 4.
P
PN[W(CO)3(dmpe)(SH)] 2(P
PN = Ph3
PNPPh3,dmpe = Me2PC2H4PMe2)与
水溶性
甲醛在
三氟乙酸存在下反应,几乎定量生成了
硫醛
金属配合物 mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 3。类似地,异构体 mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCD2)] 3-D22 也获得了。配合物 3 具有轻微扭曲的五角双锥结构,其中一个羰基、两个
磷原子以及
硫醛
配体的碳和
硫原子位于五角平面上。在溶液中,3 与 fac-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 4 处于平衡状态。通过 DFT 方法计算了 3 和 4 及其异构体 3′ 和 4′ 的结构和能量,结果与实验数据非常契合。记录了 3 和 3-D22 的 FT-IR 和 FT-Raman 光谱,并在 DFT 计算的帮助下进行了归属。计算的振动幅度强调了模式的广泛混合,特别是在低波数区域。3 的 HOMO 可以大致描述为
硫的孤对,能量比异构体 4 高出 0.38 eV。两个异构体的 LUMO 都高度去局域化,而 4 的 LUMO 能量低 0.45 eV。基于这一点,预计亲电试剂将优先在 3 的
硫原子上加成,而亲核试剂(如果有的话)则会加到 4 的
硫羰基碳上。