Stabilization of Pentaphospholes as η<sup>5</sup>‐Coordinating Ligands
Christoph Riesinger, Gábor Balázs, Michael Bodensteiner, Manfred Scheer
Abstract
Abstract Electrophilic functionalisation of [Cp*Fe(η 5 ‐P 5 )] ( 1 ) yields the first transition‐metal complexes of pentaphospholes (cyclo‐P 5 R). Silylation of 1 with [(Et 3 Si) 2 (μ‐H)][B(C 6 F 5 ) 4 ] leads to the ionic species [Cp*Fe(η 5 ‐P 5 SiEt 3 )][B(C 6 F 5 ) 4 ] ( 2 ), whose subsequent reaction with H 2 O yields the parent compound [Cp*Fe(η 5 ‐P 5 H)][B(C 6 F 5 ) 4 ] ( 3 ). The synthesis of a carbon‐substituted derivative [Cp*Fe(η 5 ‐P 5 Me)][X] ([X] − =[FB(C 6 F 5 ) 3 ] − ( 4 a ), [B(C 6 F 5 ) 4 ] − ( 4 b )) is achieved by methylation of 1 employing [Me 3 O][BF 4 ] and B(C 6 F 5 ) 3 or a combination of MeOTf and [Li(OEt 2 ) 2 ][B(C 6 F 5 ) 4 ]. The structural characterisation of these compounds reveals a slight envelope structure for the cyclo‐P 5 R ligand. Detailed NMR‐spectroscopic studies suggest a highly dynamic behaviour and thus a distinct lability for 2 and 3 in solution. DFT calculations shed light on the electronic structure and bonding situation of this unprecedented class of compounds.