Plumbylene complexes

Divalent organotin and organolead compounds can be divided into two classes, viz, those in which the organic groups are organic groups are 7r-bonded to the metal. We will deal with these two classes separately beginning with the 7r-bonded species. A third section will cover transition metal stannylene and plumbylene complexes from both classes. 

Organostannylene and plumbylene complexes of transition metals can be synthesized from both divalent and tetravalent starting materials. 

Two spectroscopically characterized examples of base-free plumbylene complexes are (CO)5MoPb N(SiMe3)2 2 and [Pd( i -C3H5)(/u.-Cl)Pb N(SiMe3)2 2]2- A simple route to obtain Mo-Pb(II) complexes involves the amine elimination reaction shown in equation (16). ... 

In the solid state, both 46 and 47 exist as bent monomeric sandwich complexes with ring centroid-lead-ring centroid angles of 152.2° in 46 and 144.2° in 47. Interestingly, if the reaction between PbCl2 and [Li(dme)2][/Bu2G2P3] is carried out in tmen rather than DME, the product formed is not a homoleptic plumbylene but rather the novel heterobimetallic compound 48.73... 

Direct synthesis of complexes of structure type B from germylenes, stannylenes and plumbylenes is possible in several cases. Many complexes of the very sterically hindered metallenes M[CH-(SiMe3)2]2 (M = Ge, Sn, Pb) have been obtained (Scheme 1).2 27... 

This absorption probably belongs to a complex of this plumbylene with solvent (toluene). 

VII. VIBRATIONAL SPECTRA OF COMPLEXES OF GERMYLENES, STANNYLENES AND PLUMBYLENES WITH LEWIS BASES... 

Data on the redox potentials of germylenes, stannylenes, plumbylenes and their complexes are scarce. In fact, only the electrochemistry of dihalogermylenes, dihalostan-nylenes and their complexes with Lewis bases338 as well as with chromium, molybdenum and tungsten pentacarbonyles339 has been studied. 

There are several reports concerning the thermal and photochemical reactivity of triorganolead metal complexes. In general they eliminate plumbylenes, R2Pb, with a concurrent transfer of the organic radical to the metal center. Such chemistry is reported for platinum, iron and molybdenum inter alia. A typical reaction is outlined in equation 195484.494,507,509... 

The mechanistic details for these disproportionation reactions are not clear. It is possible that a-elimination chemistry as outlined in equation 197 is involved, resulting in transient plumbylene metal complexes however, no definitive data are available to substantiate such intermediates. 

Very few reactions have been reported for organostannylene and plum-bylene complexes. The complexes are generally air sensitive, but less so than the parent divalent stannylenes or plumbylenes. Triphenylphosphine fails to displace the terminal stannylene in the complex shown in Eq. (54). 

As mentioned above, cationic phosphenium is isoelectronic with carbene, silylene, germylene, stannylene, and plumbylene, because the central element has lone pair electrons and a vacant p orbital as well as two substituents. Therefore, their transition metal complexes have attracted considerable attention. It might be of special interest to compare cationic phosphenium complexes with silylene complexes because phosphorus and silicon are both situated in the third row of the periodic table. 

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