110313-86-5Relevant articles and documents
Transition-metal-promoted cyclization reactions of isocyanide ligands. Synthesis of cyclic aminooxycarbene complexes of platinum(II) and X-ray structure of trans -{(PPh3)2Pt[CN(C6H4-p-Me)CH 2CH2O]Br}BF4
Michelin, Rino A.,Zanotto, Livio,Braga, Dario,Sabatino, Piera,Angelici, Robert J.
, p. 85 - 92 (2008/10/08)
Electrophilic isocyanide CNR ligands in cationic Pt(II) complexes of the type trans-[(PR′3)2Pt(CNR)Cl]BF4 (I) (PR′3 = PPh3, PMe2Ph; R = p-MeOC6H4, p-MeC6H4, p-NO2C6H4, Me, C6H11) are converted to the corresponding 5-membered cyclic aminooxycarbene derivatives trans-{(PR′3)2Pt[CN(R)CH2CH 2O]X}BF4 (II) (X = Cl, Br) by reaction in THF with 2-bromoethanol in the presence of n-BuLi. These reactions are likely to proceed by nucleophilic attack of the alkoxide on the isocyanide carbon atom to give an imidoyl intermediate, which cyclizes intramolecularly to yield the carbene products. The less sterically hindered CNMe and aryl isocyanide ligands in I are converted in a few minutes to the final products II in ca. 70-90% yield; the more bulky CNC6H11 derivative gives only a 25% yield. The t-BuNC ligand in the complex trans-[(PPh3)2Pt(CN-t-Bu)Cl]BF4 does not react at all, nor does p-MeOC6H4NC in trans-[(PCy3)2Pt(CNC6H 4-p-OMe)Cl]BF4 with bulky PCy3 ligands. Treatment of cis-Cl2Pt(CNC6H4-p-OMe)2 with 2 equiv of 2-bromoethoxide gave the bis(aminooxycarbene) Br2Pt[CN(C6H4-p-OMe)CH2CH 2O]2. The Pt(II)-cyclic aminooxycarbenes II were characterized by their elemental analysis and IR, 1H NMR, and 31P NMR spectra. An X-ray-determined structure of trans-{(PPh3)2Pt[CN(C6H 4-p-Me)CH2CH2O]Br}BF4, space group P21/a, a, = 12.175 (2) ?, b = 26.137 (3) ?, c = 13.274 (4) ?, β = 91.61 (2)°, and Z = 4, was refined to R = 0.039 (Rw = 0.044) for 5325 independent reflections. The coordination geometry around the Pt(II) atom is square planar with the carbene ligand perpendicular to the plane. The cyclic aminooxycarbene ligand is planar with C(sp2)-N and C(sp2)-O bond distances of 1.30 (1) and 1.33 (1) ?, indicating significant π-bonding between the nitrogen, oxygen, and carbene carbon.
