Activation of the Si–H bond of Et2SiH2 in photochemical reaction with W(CO)6: Spectroscopic characterization of intermediate W–Si compounds and the revisited crystal structure of the bis{(μ-η2-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η2

The photochemical reaction of W(CO)6 with diethylsilane has been used to generate new tungsten–silicon compounds varying in stability. The initially formed η2-silane intermediate complex [W(CO)5(η2-H–SiHEt2)], characterized by two equal-intensity doublets with 2JH–H = 10 Hz at δ = 5.10 (1JSi–H = 217 Hz) and δ = −8.05 (1JW–H = 38 Hz, 1JSi–H = 93 Hz), was detected by the 1H NMR spectroscopy (methylcyclohexane-d14, −10 °C). The η2-silane complex was converted in the dark to give more stable species. One of them was characterized by two equal-intensity proton signals observed as doublets with 2JH–H = 5.2 Hz at δ = −8.25 and −10.39 ppm. The singlet proton resonance at δ = −9.31 flanked by 29Si and 183W satellites (1JSi–H = 43 Hz, 2JSi–H = 34 Hz, 1JW–H = 40 Hz) was assigned to the agostic proton of the W(η2-H–SiEt2) group in the most stable compound isolated from the photochemical reaction products in crystalline form. The molecular structure of the bis{(μ-η2-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η2-H–SiEt2)(CO)4}2] was established by single-crystal X-ray diffraction studies. The tungsten hydride observed in the 1H NMR spectrum at δ = −9.31 was located in the structure at a chemically reasonable position between the W and Si atoms of the W–Si bond of the bridging silyl ligand. The reactivity of photochemically generated W–Si compounds towards norbornene, cyclopentene, diphenylacetylene, acetone, and water was studied. As was observed by IR and NMR spectroscopy, the η2-silane ligand in the complex [W(CO)5(η2-H–SiHEt2)] is very easily replaced by an η2-olefin or η2-alkyne ligand.