Plumbane

Lead, like tin, forms only one hydride, plumbane. This hydride is very unstable, dissociating into lead and hydrogen with great rapidity. It has not been possible to analyse it rigorously or determine any of its physical properties, but it is probably PbH4. Although this hydride is unstable, some of its derivatives are stable thus, for example, tetraethyllead, Pb(C2Hj)4, is one of the most stable compounds with lead in a formal oxidation state of + 4. It is used as an antiknock in petrol. 

An exchange reaction between bis(trifluorometbyl)mercury and tetrame-thylleud gives trimethyl(mfluoromethyl)plumbane [23] (equation 17) This plum-bane can also be prepared via the reaction of tetramethyllead with tnfluoromethyl radicals produced in a radio-frequency discharge of C2F [24]... 

Networks with labeled branch points have also been synthesized by anionic techniques. The crosslinks contain either ferrocene units 107) or lead, originating respectively from vinylferrocene or tetrakis[4(l-phenylvinyl)phenyl]plumbane 94). 

Enantioenriched a-alkoxyorganolead compounds have been prepared through lithiation of stannane precursors and trapping of the lithiated species with a triorganolead halide (equation 35)75. In the presence of TiCU, these plumbanes add to aldehydes to afford monoprotected syn- 1,2-diols. The use of BF3OEt2 as a Lewis acid promoter leads mainly to the anti adducts (Table 13)70. 

The catenation abihty of lead being considerably lower than that of germanium or tin, plumbanes with Pb—Pb bonds are quite difficult to prepare, even though a number of such compounds have been synthesized. As already pointed out, the main method for the preparation of this type of compound is the reaction of an appropriate Grignard reagent with PbCl2159, e.g. 

By organoboration of bis(alkynyl)plumbanes 85, the compound 86, stabilized by a jt-bonding interaction, is prepared180. (Scheme 22a). The cation 86 is unstable and, at room temperature, decomposes rapidly to rearrange into a l,4-plumbabora-2,5-cyclohexa-diene, 87. 

Plumbanes with particular or bulky substituents can be prepared by several special procedures. For example, tetra-p-nitrophenyllead can be prepared by a disproportionation reaction, induced by hydrazine, of Ar2PbX2, where Ar = p-N(OCgFE, X = Cl, Br, I190 ... 

Mixed alkyl plumbanes can be prepared via trialkylplumbylmagnesium chlorides378 by the sequence of reactions... 

Addition of PbCl2 to the above-mentioned dilithiated derivatives generates spiro-plumbanes (99, 99a and 99b)385. The preparation of spiroplumbanes can also be performed... 

A number of related stannane compounds have now been characterized, although to date no plumbanes. In addition, there is no definite evidence for the formation of M—Ge—H interactions, although Carre and coworkers90 have suggested that one may exist in MeCpMn(CO)2(H)GePh3. For a full coverage of this subject see the review by Schubert92. 

Ge3H8) less flammable than silanes, are rapidly oxidized in air. Stannane (SnH4) decomposes rapidly even at 0°C plumbane (PbH4) has a doubtful existence. 

Similarly, trityl cation in aromatic hydrocarbons initiates the fragmentation of simple tetraalkyl plumbanes and stannanes yielding the plumbyl or stannyl cationic species, e.g. 11, and alkenes. The reaction is thought to proceed via plumbyl-or stannyl-substituted carbocations 12, which in a second step eliminate the al-kene. This approach was used in the synthesis of norbornyl cations of the elements tin and lead, e.g. 13, (Scheme 5). ... 

PbH4 plumbane BiH3 bismuthanet P0H2 polane... 

Lead Tetraethyl (Tetraethyl lead, Lead Tetraethide, Tetraethyl Plumbane). Pb(C2Hs)4, mw 323.45, colorless liq, fr p -136°, bp about 200°, also stated as 227.7° with decompn, d 1.653g/cc at 20° insol in w si sol in ale, sol in benz and eth. May be prepd by die action of Pb chloride on Zn ethyl or on a Grignard reag. Used extensively as an antiknock addition to gasoline, and has been proposed by Fr investigators as a flash reducer in proplnts (Ref 2)... 

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