New Rhodium( I ) Complexes with Hemilabile Amphiphilic Phosphanes

A series of Rh I complexes was prepared and characterised with the following hemilabile amphiphilic phosphanes: R−(C 6 H 4 )−(OCH 2 CH 2 ) n −PPh 2 [ 1 (R = tert ‐octyl, n = 1), 2 (R = tert ‐octyl, $\bar n$ = 5), 3 (R = tert ‐octyl, $\bar n$ = 13), 4 (R = n ‐nonyl, $\bar n$ = 1.4), 5 (R = n ‐nonyl, $\bar n$ = 5), 6 (R = n ‐nonyl, $\bar n$ = 11)]. The reactions between 1 − 6 and [Rh(COD)(THF) 2 ] + , and the subsequent reaction with CO were studied by 31 P NMR and IR spectroscopy. The data are consistent with the formation of P‐coordinated and chelated (P,O) species for ligands 2 − 6 , in agreement with the hemilabile character of these ligands. In the case of ligand 1 , the complex trans ‐[Rh( 1 ) 2 (CO) 2 ] + has been isolated and the cis ‐[Rh( 1 ) 2 (CO) 2 ] + compound has been detected. [Rh( 1 ) 2 (CO)] + was prepared by decarbonylation of trans ‐[Rh( 1 ) 2 (CO) 2 ] + , and low‐temperature NMR spectroscopic studies have shown the hemilabile character of 1 with a very weak P−O interaction. The molecular structure of trans ‐Rh(CO)( 1 ) 2 Cl was determined by X‐ray crystallography and shows that the conformation of the tert ‐octylphenoxyethyl chains is nearly identical to that previously reported in the complex trans ‐PdCl 2 ( 1 ) 2 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)