Diamidato-bis(diphenylphosphino) platinum(II) complexes: Synthesis, characterization, and reactivity in the presence of acid

The reaction of Pt(COD)Cl-2, where COD is 1,5- cyclooctadiene, with one equivalent of a diamidatobis(phosphino) Trost ligand ((R, R)- 2 = N, N'- bis(2- diphenylphosphino- 1- benzoyl)-(1R, 2R)- 1,2- diaminocyclohexane, (R, R)- 3 = N, N0- bis(2- diphenylphosphino- 1- naphthoyl)-(1R, 2R)- 1,2- diaminocyclohexane, or (+/-)- 4 = N, N'-bis(2-diphenylphosphino-1-benzoyl)- 1,2- bis(aminobenzene)) in the presence of base afforded square planar diamidato- bis(phosphino) platinum(II) complexes (R, R)-2-Pt, (R, R)- 3- Pt, (+/-)-4-Pt. Characterization of all complexes included the solution and solid state structure determination of each complex based on multinuclear NMR and X- ray analyses, respectively. Stability of the complexes in acid was examined on addition of HCl to (R, R)-2-t in chloroform and compared to the unreactive nature of the similar diamidato- bis(phosphino) complex 1- Pt (1 = 1,2-bis-N-[2'-(diphenylphosphino)benzoyl] diaminobenzene) in the presence of acid. Protonation of the bound amidato nitrogen atoms of (R, R)- 2- Pt was observed along with decoordination of the nitrogen atoms from the platinum(II) center producing (R, R)-2-PtCl2 in quantitative yield by NMR analysis. Confirmation of the product was made on comparison of the NMR spectra to that of authentic (R, R)-2-PtCl2 prepared on reaction of Pt(COD) Cl-2 with (R, R)-2 in CH2Cl2 and characterized by single- crystal X-ray diffraction analysis and NMR spectroscopy. Results add to the knowledge of rich coordination chemistry of bis(phosphino) ligands with late transition metals, metal- amidato chemistry, and has implications in catalysis. (C) 2010 Elsevier B. V. All rights reserved.