3]Ferrocenophanes with the bisphosphanotetryl bridge: inorganic rings on the way to tetrylenes

Denis Kargin,László Nyulászi,Zsolt Kelemen,Kristijan Krekić,Clemens Bruhn,Rudolf Pietschnig,Martin Maurer

doi:10.1039/c5dt03107a

Abstract

A series of [3]ferrocenophanes with functional P-E-P motifs (E = group 14 fragments) is reported. Out of these, the silicon compounds with the general formula Fe(C5H4PtBu)2SiXY (XY = Cl2, Br2, I2, H2, HCl) have been characterized by spectroscopic means and the bonding situation was analyzed using X-ray crystallography and quantum chemical calculations. Despite the two stereogenic phosphanyl centers, most of the [3]ferrocenophanes have been obtained as single isomers in the course of stereospecific reactions. The corresponding stannylene Fe(C5H4PtBu)2Sn has been obtained in the form of its dimeric adduct.

Highlights

A series of [3]ferrocenophanes with functional P–E–P motifs (E = group 14 fragments) is reported
The silicon compounds with the general formula Fe(C5H4PtBu)2SiXY (XY = Cl2, Br2, I2, H2, HCl) have been characterized by spectroscopic means and the bonding situation was analyzed using X-ray crystallography and quantum chemical calculations
These findings suggest that the >P–E–P< motif (E = group 14 elements) can be achieved, the steric protection exerted by the t-butyl groups at phosphorus is obviously insufficient to prevent dimerization

Summary

Introduction

Our DFT calculations revealed that the other possible stereoisomers of 4, 6 and 7 in which the two t-butyl units at the two phosphorus atoms point to different sites of the molecule (Fig. S1 in the ESI‡) exhibit somewhat lower stability Regarding the sum of the angles at the phosphorus atoms, smaller angles in the range between 310° and 311°, combined with the smaller angle at the silicon atom PSiP = 98.54(3)° suggest a slightly higher ring strain within the bridge of [3]ferrocenophane 8 compared with the previously discussed compounds in which this angle increases with the electronegativity of the halide (4: P1–Si1–P2 = 102.46(2)°, 6: P1–Si1–P2 = 100.73(5)°, 7: P1–Si1–P2 = 100.21(3)°).

Results

Conclusion