799297-10-2Relevant academic research and scientific papers
Terphenyl ligand stabilized lead(II) derivatives: Steric effects and lead-lead bonding in diplumbenes
Hino, Shirley,Olmstead, Marilyn,Phillips, Andrew D.,Wright, Robert J.,Power, Philip P.
, p. 7346 - 7352 (2004)
The reaction of PbBr2 with the lithium reagents LiC 6H3-2,6-(C6H3-2,6-Pr i2)2 (LiArPri2) and Et2O·LiC6H3-2,6-(2,6-Pr i-4-Bu1C6H2)2 (Et 2O·LiArPri2But) furnished the bromide bridged organolead(II) halides {Pb(μ-Br)ArPri 2}2 (1) and {Pb-(μ-Br)ArPri 2But}2 (2) as orange crystals. Treatment of 1 with a stoichiometric amount of methylmagnesium bromide resulted in the "diplumbene" Pri2Ar(Me)PbPb(Me)ArPr i2 (3). The addition of 1 equiv of 4-tert- butylphenylmagnesium bromide to 1 afforded the feebly associated, Pb-Pb bonded species {Pb(C6H4-4-But)ArPri 2}2 (4), whereas the corresponding reaction of tert-butylmagnesium chloride and 1 afforded the monomer Pb(Bu t)ArPri2 (5). The reaction of the more crowded aryl lead(II) bromide {Pb(μ-Br)ArPri3}2 (Ar* = C6H3-2,6(C6H2-2,4,6- Pri3)2) with 4-isopropylbenzylmagnesium bromide or LiSi(SiMe3)3 yielded the monomers 6, [Pb(CH 2C6H4-4-Pri)ArPri 3], or 7, [Pb(Si(SiMe3)3)-ArPri 3]. All compounds were characterized with use of X-ray crystallography, 1H, 13C, and 207Pb NMR (3-7), and UV-vis spectroscopy. The dimeric Pb-Pb bonded (Pb-Pb = 3.1601(6) A) structure of 3 may be contrasted with the previously reported monomeric structure of Pb(Me)ArPri3, which differs from 3 only in that it has para Pri substituents on the flanking aryl rings. The presence of these groups is sufficient to prevent the weak Pb-Pb bonding seen in 3. The dimer 4 displays a Pb-Pb distance of 3.947(1) A, which indicates a very weak lead-lead interaction, and it is possible that this close approach could be caused by packing effects. The monomeric structures of 6 and 7 are attributable to steric effects and, in particular, to the large size of ArPri3.
