Vinylsilanes are very useful building blocks in organic synthesis and have widespread applications in life sciences and materials chemistry. Here we describe the potential of complex cis-[Fe(PCP-iPr)(CH₂CH₂CH₃)(CO)₂] as an effective catalyst for the hydrosilylation of both terminal and internal alkynes with SiPhH3 to give vinylsilanes. The reactions were typically performed with a catalyst loading of 1 mol% for 24 h at 70 °C. The catalytic reaction is initiated by migratory insertion of a CO ligand into the Fe─alkyl bond to yield an acyl intermediate, which reacts with silanes to form the 16e⁻ Fe(II) silyl catalyst [Fe(PCP-iPr)(SiPhH₂)(CO)]. In the case of aliphatic terminal alkynes good regioselectivity (anti-Markovnikov addition) toward the thermodynamically more stable β-(E)-vinylsilanes in ratios of up to 10:90 was achieved, while for aromatic alkynes the selectivities were poor with ratios of β-(Z)- to β-(E)-vinylsilanes of about 40:60. With internal unsymmetrical alkynes, the two possible regioisomers of the syn-addition of SiPhH₃ were obtained in different ratios with no clear trend toward one regioisomer. Internal symmetrical alkynes yielded exclusively the respective syn-products in high yields. Mechanistic investigations including deuterium labelling studies were undertaken to provide a reasonable reaction mechanism.
