posted on 2024-01-09, 12:34authored byAtheer
M. Madlool, Ahmed Alwaaly, Casey M. Dixon, Paul G. Waddell, William Clegg, Michael R. Probert, Ross W. Harrington, Keith Izod
The benzyl-substituted
phosphine–boranes PhCH2P(BH3)R2 [R = iPr (1H), Ph (2H), Cy (3H)] are accessible
through
either the reaction between R2PCl and PhCH2MgBr,
followed by treatment with BH3·SMe2 or
the reaction between R2P(BH)3Li and PhCH2Br. Treatment of 1H, 2H, or 3H with nBuLi, PhCH2Na, or PhCH2K gave the corresponding alkali metal complexes [{iPr2P(BH3)CHPh}Li(THF)]2 (1Li), [{Ph2P(BH3)CHPh}Li(OEt2)2] (2Li), [{Cy2P(BH3)CHPh}Li(TMEDA)] (3Li), [iPr2P(BH3)CHPh]Na (1Na), [{Ph2P(BH3)CHPh}Na(THF)2]2 (2Na), [Cy2P(BH3)CHPh]Na(THF)0.5 (3Na), [{iPr2P(BH3)CHPh}K]∞ (1K), [{Ph2P(BH3)CHPh}K(THF)]∞ (2K), and [{Cy2P(BH3)CHPh}K.0.5PhMe]∞ (3K). X-ray crystallography revealed that, while 2Li and 3Li crystallize as monomers, 1Li and 2Na crystallize as borane-bridged dimers. The potassium complexes 1K, 2K, and 3K all crystallize with
polymeric structures, in which the monomer units are linked to each
other through a range of both bridging BH3 groups and multihapto
interactions between the potassium cations and the aromatic rings.
The reactions between two equivalents of either 1Li or 3Li and Cp2Sn gave the corresponding dialkylstannylenes
[{R2P(BH3)CHPh}2Sn] [R = iPr (1Sn), Cy (3Sn)]. These compounds
were isolated as mixtures of the rac and meso diastereomers. X-ray crystallography reveals that rac-1Sn and rac-3Sn crystallize as discrete monomers each exhibiting two agostic-type
B–H···Sn contacts.