Triple bonding to germanium:: Characterization of the transition metal germylynes (η5-C5H5)(CO)2MGe-C6H3-2,6-MeS2 (M = Mo, W; Mes = -C6H2-2,4,6-Me3) and (η5-C5H5)(CO)2MGe-C6H3-2,6-Trip2 (M = Cr, Mo, W; Trip -C6H2-2,4,6-i-Pr3) and the related single bonded metallogermylenes (η5-C5H5)(CO)3M-Ge-C6H3-2,6-Trip2 (M = Cr, W)

The synthesis and characterization of several m-terphenyl stabilized germylyne transition metal complexes and related metallogermylenes are reported. The reaction of Na[M(eta(5)-C5H5)(CO)(3)] (M = Cr, or W) with Ge(Cl)C6H3-2,6-Trip(2) (Trip = -C6H2-2,4,6-i-Pr-3) below room temperature affords the metallogermylenes (eta(5)-C5H5)(CO)(3)M-Ge-C6H3-2,6-Trip(2) (M = Cr, 1; W, 5). However, for the analogous reaction with Na[Mo(eta(5)-C5H5)(CO)(3)], the metallogermylene was not isolated. Instead, the germylyne complex (eta(5)-C5H5)(CO)(2)Mo drop Ge-C6H3-2,6-Trip(2) (3) was obtained directly with elimination of carbon monoxide. The corresponding chromium and tungsten compounds (eta(5)-C5H5)(CO)(2)M drop Ge-C6H3-2,6-Trip(2) (M = Cr, 2; W, 6) could be obtained by refluxing 1 or 5 in toluene or by photolysis. The related germylyne (eta(5)-C5H5)(CO)(2)W drop Ge-C6H3-2,6-Mes(2) (7), as well as the recently reported molybdenum analogue (eta(5)-C5H5)(CO)(2)Mo drop Ge-C6H3-2,6-Mes(2) (4), which was the first example of a triply bonded germanium species? are also described. All compounds were characterized by H-1 and C-13 NMR, UV-vis, and IR spectroscopy, and by 6, H analysis. The X-ray crystal structures of 1-3, 5, and 7 have also been determined. The M drop Ge (M = Cr, Mo, W) triple bonds in the germylynes are typically ca. 0.4 ti shorter than the hl-Ge single bonds in the metallogermylenes. In addition, angles at germanium in the germylynes are nearly linear (range 170.9(3)-175.99(6)degrees) whereas in the metallogermyleness the corresponding angles are 114.7(6) and 117.8(2)degrees, consistent with the presence of a lone pair at germanium. The synthesis of the series of compounds 1-7 has enabled, for the first time, a comparison of single and triple bond lengths between closely related species involving the same coordination number and substituents at the heavier group 14 element.