Reactivity of cyclooligophosphanes: synthesis and structural characterisation of cyclo-1,4-(BH3)2(P4Ph4CH2) and cyclo-1,2-(BH3)2(P5Ph5).
The borane complexes cyclo-1,4-(BH3)2(P4Ph4CH2) (3) and cyclo-1,2-(BH3)2(P5Ph5) (4) were prepared by reaction of cyclo-(P4Ph4CH2) and cyclo-(P5Ph5) with BH3(SMe2). Only the 2:1 complexes 3 and 4 were isolated, even when an excess of the borane source was used. In solution, 3 exists as a mixture of the two diastereomers (R(P)*,S(P)*,S(P)*,R(P)*)-(+/-)-3 and (R(P)*,R(P)*,R(P)*,R(P)*)-(+/-)-3. However, in the solid state the (R(P)*,S(P)*,S(P)*,R(P)*)-(+/-) diastereomer is the major stereoisomer. Similarly, while only one isomer of 4 is observed in its X-ray structure, NMR spectroscopic investigations reveal that it forms a complex mixture of isomers in solution. 3 may be deprotonated with tBuLi to give the lithium salt cyclo-1,4-(BH3)2(P4Ph4CHLi) (3 x Li), though this could not be isolated in pure form.
Wolf
Robert
R
Institut für Anorganische Chemie der Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
Finger
Markus
M
Limburg
Carolin
C
Willis
Anthony C
AC
Wild
S Bruce
SB
Hey-Hawkins
Evamarie
E
D001880:Boranes / Q000737:chemistry; D002412:Cations; D003460:Crystallization; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D017553:Phosphorus Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012996:Solutions
D001880:Boranes; D002412:Cations; D017553:Phosphorus Compounds; D012996:Solutions