文摘
The dinuclear platina-尾-diketone [Pt2{(COMe)2H}2(渭-Cl)2] (1) reacted with 2-pyridyl-functionalized monoximes and with dioximes in the presence of NaOMe to yield oxime鈥揹iacetyl platinum(II) complexes [Pt(COMe)2(2-pyCR鈺怤OH)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(HON鈺怌R鈥揅R鈺怤OH)] (R/R = Me/Me, 5a; Ph/Ph, 5b; (CH2)4, 5c; NH2/NH2, 5d), respectively. The strong intramolecular O鈥揌路路路O hydrogen bonds in these complexes give rise to an activation of the acetyl ligands for Schiff-base type reactions, thus forming with primary amines iminoacetyl platinum complexes [Pt(COMe)(CMe鈺怤HR鈥?(2-pyCR鈺怤O)] (R/R鈥?= H/Bn, 6a; Me/Bn, 6b; Ph/Bn, 6c; H/CH2CH2Ph, 6d; H/CH2CH鈺怌H2, 6e; Bn = benzyl) and [{Pt(CMe鈺怤HR鈥?2(ON鈺怌R鈥揅R鈺怤O)}2] (R/R = Me/Me, 7a鈥?b>d; Ph/Ph, 8a鈥?b>d; (CH2)4, 9a; R鈥?= Bn, a; CH2CH2Ph, b; CH2CH鈺怌H2, c; CH2CH2OH, d). The intramolecular N鈥揌路路路O hydrogen bonds in type 6鈥?b>9 complexes make clear that protonated iminoacetyl ligands (i.e., aminocarbene ligands) and deprotoanted oxime ligands are present. These complexes could also be obtained in reactions of [Pt(COMe)2(NH2R鈥?2] (3) with pyridyl-functionalized monoximes and with dioximes where type 4/5 complexes were found to be intermediates. In solution, the bis(iminoacetyl) complexes 7鈥?b>9 were found to be present as dimers (as also 8a in the solid state) with smaller amounts of monomers. The importance of hydrogen bonds for activation of acetyl ligands was further evidenced by synthesis of complexes [Pt(COMe)2(2-pyCH鈺怤OMe)] (10) and [Pt(COMe)2(HON鈺怌Me鈥揅Me鈺怤OMe)] (11) bearing O-methylated oxime ligands and their reactivty toward amines. The hydrogen-bond activated acetyl and iminoacetyl ligands in type 5, 7, and 8 complexes were found to undergo in CD3OD solutions facile H/D exchange reactions resulting in complexes bearing C(CD3)鈺怬/C(CD3)鈺怤DR鈥?ligands. The constitution of all complexes was unambiguously confirmed analytically, spectroscopically and in part by single-crystal X-ray diffraction analyses. Structural and NMR parameters as well as DFT calculations gave evidence for relatively strong intramolecular hydrogen bonds.
