Half-Sandwich Tungsten Complexes with Metal- and η⁵-Cyclopentadienyl-Bound Functional Stannyl Groups and Their Transformation intoAnsaComplexes^†

We report the introduction of two stannyl groups into a half-sandwich tungsten complex and their subsequent functionalization in order to generate useful precursors for the formation of diverse ansa-type tungsten complexes. Bis-stannylation is achieved by treatment of the dilithiated species Li-[W(eta(5)-C5H4Li)(CO)(3)] (7) with 2 equiv of Me3SnCl, yielding [{Me3Sn(eta(5)-C5H4)}(OC)(3)W(SnMe3)] (8). Successive chlorination is achieved by use of Me2SnCl2 and SnCl4 center dot 2OEt(2) and enables the selective formation of [{Me3Sn(eta(5)-C5H4)}(OC)(3)W(SnMe2Cl)] (10), [{ClMe2Sn(eta(5)-C5H4)}(OC)(3)W(SnMe2Cl)] (11), and [{ClMe2Sn(eta(5)-C5H4)}(OC)W-3(SnMeCl2)} (12). The reaction of 11 with sodium amalgam gives a product mixture, consisting of the tristanna-bridged ansa complex [{eta(1)-SnMe2-SnMe2-SnMe2-(eta(5)-C5H4)}(CO)(3)W] (13) and the cyclic dinuclear tungsten compound [{Me2Sn-(eta(5)-C5H4}-(OC)(3)W](2) (14). Ring closure of 12 was achieved upon reaction with Na2S to yield [{eta(1)-Sn(Cl)Me-S-SnMe2-(eta(5)-C5H4)}(CO)(3)W] (15), which displays a chiral, tungsten-bound tin center. All new compounds have been fully characterized by elemental analyses and, in solution, by IR and multinuclear NMR spectroscopy. The crystal structures of complexes 8, 11, 12, 14, and 15 were presented and discussed, showing Sn-W bond lengths of 2.8481(5) (8), 2.7586(3) (11), 2.7256(3) (12), 2.8180(3) (14), and 2.7662(2) angstrom (15).