Heterobimetallic alkoxysilyl cationic complexes: investigations into the displacement of a μ-η2-Si,O bridge by functional phosphine ligands

Abstract

The lability of the SiO→M interaction unique to some bimetallic complexes may confer hemilabile properties to the Si(OR) 3 ligand and various bifunctional phosphines P-Z have been used in order to evaluate the possible competition for co-ordination between the bridging SiO→M interaction and P-Z chelation. Thus, treatment of the heterobimetallic complexes [(OC) 3 Fe{µ-Si(OMe) 2 (OMe)}(µ-dppm)MCl] (M = Pd 4 or Pt 6; dppm = Ph 2 PCH 2 PPh 2 ) and [(OC) 3 Fe{µ-Si(OMe) 2 (OMe)}(µ-dppa)PdCl] 5 (dppa = Ph 2 PNHPPh 2 ) with TlPF 6 in the presence of P-Z afforded the corresponding cationic compoundsNPh 2 , f ). These complexes are stabilized by the occurrence of a Fe-Si-O→M four-membered ring and the pre-existent SiO→M interaction in 4-6 was not displaced by the donor function of the incoming P-Z ligand. Complexes 1b and 1f were obtained as mixtures of two isomers, the P-Z ligands acting either as monodentate or as a P,O chelate. In the latter cases formation of fiveco-ordinated palladium species is proposed. Displacement of the SiO→Pd interaction originally present in 4 was observed when the diphosphines (Ph 2 P) 2 NR (R = Me or (CH 2 ) 3 Si(OEt) 3 ) were used, since the two phosphorus atoms co-ordinate to the Pd. Surprisingly these diphosphine ligands show different co-ordination modes, depending on whether dppa or dppm is used as the assembling ligand. In the former case, chelation to the Pd is observed, which leads to complex [(OC) 3 {(MeO) 3 Si}Fe(µ-dppa)Pd{Ph 2 PN(Me)PPh 2 }]PF 6 2g, whereas in the latter case, oligomeric entities of the type [{(OC) 3 {(MeO) 3 Si}Fe(µ-dppa)Pd[Ph 2 PN(R)PPh 2 ]} n ][PF 6 ] n 1g,1h (n probably equals two) were formed. The molecular structures of [PdCl(dppm-P,PЈ){Ph 2 PC 6 H 4 (o-OMe)}]PF 6 g and [Pd 2 Cl 2 (µ-CO)-(µ-dppm) 2 ] 10, obtained during this work, have been determined by X-ray diffraction.

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

“…The situation in Scheme has been examined recently for two chemically different hemilabile ligands (with the donor atoms D being Si and P, respectively) which carry different oxygen functionalities able to compete for the same coordination site, as shown in Scheme 71…”

Electron‐Rich Vaska‐Type Complexestrans‐[Ir(CO)Cl(2‐Ph2PC6H4COOMe)2] andtrans‐[Ir(CO)Cl(2‐Ph2PC6H4OMe)2]: Synthesis, Characterisation and Reactivity

“…Another long-range interaction was earlier reported for a palladium complex of 2-phenyl phosphanyl anisole, where the Pd···O distance was 3.17 Å. [15] Miller and Shaw also indicated a typical long-range interaction for the complex trans-[Ir-(CO)Cl{PMe 2 (2-MeOC 6 H 4 )} 2 ] in which an Ir···O "secondary" bond with the methoxy oxygen was reported. [16] …”

Synthesis and Coordination Chemistry of Cyano-Substituted Phosphines

“…Upon introduction of CEP into the polynuclear metal complex 123, it demonstrates the properties of Pmonodentate ligand with retaining of 4-membered bimetallic Fe-Si-O-Pd cycle in 124 [108]. At the same time for the Salts NiX2 (X = Cl, B, I) interact directly with CEP in acetone to afford either bright-red complexes NiX2(CEP)2 126 (so called -modification, the product of the kinetic control of the reaction) at stoichiometric reactant ratio or a green 1:1 adduct NiX2(CEP) [94].…”