Synthesis of η6-arene complexes of molybdenum containing β-ketophosphine and related P,O mixed donor ligands

Monocyclopentadienyl complexes of niobium, tantalum and tungsten containing heterodifunctional P,O ligandsDedicated to Prof. P. Royo on the occasion of his 65th birthday, with our warmest congratulations.

“…Complexes 5a-c were stable in solution for several hours and in the solid state for a few days, in the absence of oxygen. Contrary to the situation reported for the Mo complexes mentioned in the introduction, 20,22,23 there was no observed tendency for chelation for 1 in complexes 5a-c.…”

“…This would result in an enhanced acidity of the PCH 2 protons and thus favour HCl elimination. This is consistent with our recent observation of an H/D exchange involving the methylene protons of 2 in the Mo(II) complexes 23 The dehydrochlorination may also be facilitated by intra-and/or inter molecular HÁ Á ÁCl interactions involving the methylene protons, a bonding situation which has been encountered in the crystal structure of the Mo(II) complex [(Z-C 6 H 5 Me)Mo(Z-C 3 H 5 )Cl{Ph 2 PCH 2 C(O)Ph}]. 23 The complexes 6 exhibit remarkable stability both in solution and in the solid state.…”

“…More recently, we have described the synthesis of Z-arene-molybdenum complexes, such as [(Z-C 6 H 5 R)Mo(Z-C 3 H 5 ){Ph 2 PXHC(O)R 0 -k 2 P,O}]-[PF 6 ] (R ¼ H, Me; R 0 ¼ Ph, NPh 2 , Me; X ¼ N, C). 22,23 In these complexes, the P,O ligands act either as P-monodentate phosphine or as a P,O-chelate, whereas O-monocoordination, which may have been anticipated owing to the relatively hard nature of molybdenum vs. late transition metals, was not observed. Although ligands with carbonyl functions (ketones, [24][25][26] amides, 27,28 acids/esters 29,30 ) are known to coordinate readily to groups 5 and 6 metals, there has been no example reported, to the best of our knowledge, when a phosphine donor is also present in the ligand.…”

“…to the best of our knowledge, rare examples of early transition metal complexes, containing a chelating phosphinoenolate ligand. 22,23 60 The titanocene and zirconocene complexes of a camphor-derived phosphino-enolate have also been described. 61 Further zirconocene phosphino-enolates derived from the a-ketophosphine Ph 2 PC(O)R (R ¼ Me, Et) have been prepared by Floriani et al 62,63 Here, we report the first investigations into the coordination chemistry of P,O ligands, namely Ph 2 PCH 2 C(O)NPh 2 1, Ph 2 PCH 2 C(O)Ph 2 and Ph 2 PNHC(O)Me 3, with the halfmetallocene complexes [(Z-C 5 R 5 )MCl 4 ] 4 (a: R 5 ¼ H 5 , M ¼ Nb; b: R 5 ¼ H 5 , M ¼ Ta; c: R 5 ¼ Me 5 , M ¼ Ta; d: R 5 ¼ i PrH 4 , M ¼ W).…”

Exploring Pathways for Activation of Carbon Monoxide by Palladium Iminophosphines

“…In all studied systems, the LUMOs are localised mainly at the phosphorus substituents and on the (enolisable) CH 2 bridge throughout the series: this type of ligand has already been shown to play a role in a nucleophilic attack during the initiation steps of the process, and the enolisable ligand facilitates reactions with substrates in which a partial transfer of H is involved 8a. 9a,d…”