211575-97-2Relevant academic research and scientific papers
Synthesis, structure and reactivity of PtII complexes containing the [o-(di-o-tolylphosphino)benzyl] cyclometalated ligand towards α-stabilized phosphorus ylides
Fernandez, Susana,Garcia, Maria M.,Navarro, Rafael,Urriolabeitia, Esteban P.
, p. 67 - 76 (2007/10/03)
The reaction of [Pt(C∧P)(NCMe)2]ClO4 2 [C∧P=ortho-(di-ortho-tolylphosphino)benzyl], with the α-stabilized phosphorus ylides Ph3P=C(H)R (R=COMe, COPh, COOMe, CN) in a 1:1 molar ratio results in the formation of [Pt(C∧P){C(H)(R)PPh3}(NCMe)]ClO4 (R=COMe 3, COPh 4, COOMe 5, CN 6). Complexes 3-6 appear as single isomers in which the ylide is selectively C-coordinated trans to the P atom of the C∧P ligand. The displacement of the remaining coordinated NCMe ligand by adding more ylide was only successfully accomplished with Ph3P=C(H)CN, giving [Pt(C∧P){C(H)(CN)PPh3}{NC-C(H)PPh 3}]ClO4 7, in which one ylide is C-coordinated trans to the P atom of the C∧P ring and the other ylide is N-coordinated trans to the C atom, showing the ambidentate character of Ph3P=C(H)CN as a ligand. The reaction of [Pt(C∧P)(μ-Cl)]2 1 with PPh3 (1:2 molar ratio, CH2Cl2, r.t.) results in the formation of the two expected isomers trans- and cis-[Pt(C∧P)Cl(PPh3)] (8 and 9, respectively). The trans isomer 8 is obtained as a single product by heating the mixture of isomers in toluene or, in one step, by carrying out the reaction of 1 with PPh3 in refluxing toluene. Treatment of 8 with TlClO4 in NCMe gives trans-[Pt(C∧P)(PPh3)(NCMe)]ClO4 10 which can also be obtained by the reaction of 2 with PPh3. Complex 10 reacts with Ph3P=C(H)R (R=COMe, COOMe, CN) in a 1:1 molar ratio resulting in the displacement of the NCMe ligand and the formation of [Pt(C∧P){OC(R′)=C(H)PPh3}PPh 3]ClO4 (R′=Me 11, OMe 12) or [Pt(C∧P){NC-C(H)=PPh3}PPh3]ClO4 13 in which the ylide ligand is selectively O- (11, 12) or N-coordinated (13). The reaction of [Pt(C∧P)(μ-Cl)]2 1 with Ph3P=C(H)R (R=COMe, COOMe, CN) in a 1:2 molar ratio results in the cleavage of the chlorine-bridge system and the formation of [Pt(C∧P)Cl{C(H)(R)PPh3}] (R=COMe 14, COOMe 15, CN 16) as single isomers in which the ylide is C-coordinated trans to the P atom of the C∧P ligand. Complex 14 reacts with TlClO4 and Ph3P=C(H)COMe (1:1:1 molar ratio) giving [Pt(C∧P){OC(Me)=C(H)PPh3}2]ClO4 17. Complex 17 shows two interesting features: the isomerization of the C-linked ylide in 14 to an O-bonded one in 17 and the simultaneous presence of two O-coordinated ylides to the same metal center. The selectivity in the observed coordination modes and the preferred coordination of the ylides trans to the P atom of the C∧P ligand are discussed in terms of electronic and steric factors.
