The isolation of three-coordinate silicon cations, R,Si + , have been the subject of many recent reports.['.
However, analogous germanium cations have not been described. in a related vein, Ogino, Tobita and co-workers have isolated a cationic diiron complex bridged by a germanium center. This germanium center is substituted with one alkyl group and a Lewis baseL3"] and can be viewed as a base-stabilized germyl cation. We now report the synthesis and structure of a germanium-bridged tungsten dimer, which formally contains a base-free dimetalated gerrnyl cation (germylium ion).
Thermolysis of [Cp,W(SiMe,)(GeMe,OTf)] (1)'") in a solution of benzene at 80Β°C results in the formation of three new products, trimethylsilyl triflate (Me,SiOSO,CF,), [Cp,W(SiMe,)(GeMe,)] (2), and the dinuclear compound 3 [Eq. (a)]. Interestingly, the reaction also occurs when the solid is heated at 80 "C in the absence of a solvent.
Me. ,M" 3 Trimethylsilyl triflate was identified by 'H and 19F N M R spectroscopy and compared with an authentic sample. The tungsten germyl silyl complex 2 has previously been synthesized independently.[41 The dimeric compound 3 has been isolated in good yield (93% of theoretical) as a bright orange powder, which is moderately soluble in acetonitrile. The 'H N M R spectrum (in CD,CN) exhibits three singlets for the intact Cp rings and three broad multiplets for the substituted C,H, ring. The resonance for the remaining C,H, proton is obscured by the Cp signals. Two singlets correspond to the nonequivalent methyl groups of the C,H,GeMe, fragment and a singlet at 6 = 1.73 to the methyl group on the germanium bridging the two tungsten centers, more than 1 ppm downfield from the GeMe, resonance. A singlet corresponding to the tungsten hydride is observed at 6 = -10.8 (' Jw, = 79.9 Hz). Significantly, both this hydride chemical shift and tungsten coupling constant are normal for tungstenocene hydrides (cf. 4,; see below), which indicates that [