Synthesis, Structure, and Reactivity of Novel Intramolecularly Coordinated Organolead(II) Compounds

Abstract

The intramolecularly coordinated heteroleptic organolead(II) compounds {4-tBu-2,6-[P(O)(OEt) 2 ] 2 C 6 H 2 }PbX (2, X = Cl; 3, X = SPh) have been synthesized. Single-crystal X-ray analyses reveal that both compounds adopt polymeric chain structures by intermolecular Pb−X···Pb bridges, a structural motif previously unknown for organolead(II) derivatives. Compound 2 reacts with lithium diisopropylamide, iPr 2 NLi, and lithium bis(trimethylsilyl)methane, (Me 3 Si) 2 CHLi, respectively, to provide in situ the corresponding organolead(II) compounds {4-tBu-2,6-[P(O)(OEt) 2 ] 2 C 6 H 2 }PbX (4, X = iPr 2 N; 5, X = (Me 3 Si) 2 CH], which were identified by NMR spectroscopy but could not be obtained as analytically pure sub-

Heteroleptic Organostannylenes and an Organoplumbylene Bearing Phosphorus‐Containing Pincer‐Type Ligands – Structural Variations and Insights into the Configurational Stability

“…Moreover, addition of [(Ph 3 P) 2 N] + Cl – to a solution of [4‐ t Bu‐2,6‐{P(O)(OEt) 2 } 2 C 6 H 2 ]SnCl in CD 2 Cl 2 caused low‐frequency shift of the 119 Sn resonance to δ = –163, a value being close to that of the chemical shift in the solid state 1o. The results were interpreted in terms of [4‐ t Bu‐2,6‐{P(O)(OEt) 2 } 2 C 6 H 2 ]SnCl being monomeric in solution but, via chlorido bridges, dimeric (or oligomeric) in the solid state, like the corresponding organoplumbylene [4‐ t Bu‐2,6‐{P(O)(OEt) 2 } 2 C 6 H 2 ]PbCl 11g. Unfortunately, no single crystals of [4‐ t Bu‐2,6‐{P(O)(OEt) 2 } 2 C 6 H 2 ]SnCl suitable for X‐ray diffraction analysis could be obtained to verify this interpretation.…”

Lead(II): misleading or merely hermaphroditic?

“…The common observation that Pb(II) is found in a very asymmetric environment of a large number (often 10 or more) of possible donor atoms [7,8], however, has often meant that this problem has been by no means easily resolved. In a particular case [12], leadoxygen separations ranging from 2.38-3.07 Å, for example, have been considered, on the basis of bondvalence calculations, to be indicative of significant bonding interactions and there are numerous examples [5,[12][13][14][15][16][17][18] of 'long' Pb···X contacts that are nonetheless much shorter than the next most distant contacts and that have thus been taken as indicative of weak attractions. Uncertainty in the definition of the primary coordination sphere donor atoms in turn generates uncertainty in the identification of any coordination sphere 'hole' that might be taken to signify the presence of a stereochemically active lone pair [7,15].…”

Three‐coordinate divalent Group 14 element derivatives and related compounds

“…Thus, the presence of ligands with donor side arms on the germanium or the tin element can (by transfer of electron density) reduce the deficit on 37 is, to our knowledge, the first example of an intramolecular base stabilized homoleptic dialkylgermylene. Various amino-, phosphino-, thioalkoxy-, alkoxy-and aryloxy-divalent species have also been isolated in monomeric form owing to this method of stabilization; one should mention in particular the studies of Jutzi and co-workers, 28,32,54,71 Veith and coworkers, 15,18,40,66 Parkin and co-workers, 67 Jurkschat and co-workers, 77,78 Dias and co-workers 31,35,42,69,80,81 and Roesky and co-workers. …”