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Oberbeckmann-Winter N, Morise X, Braunstein P, Welter R: Synthesis and structure of Pt (II) phosphonato-phosphine complexes and of a P,O-stabilized metal-metal-bonded Pt2Ag2 complex. Inorg Chem. 2005 Mar 7;44(5):1391-403.
As part of our interest in the design and reactivity of P,O ligands, and because the insertion chemistry of small molecules into a metal alkyl bond is very dependent on the ancillary ligands, the behavior of Pt-methyl complexes containing the beta-phosphonato-phosphine ligand rac-Ph2PCH (Ph) P (O)(OEt) 2 (abbreviated PPO in the following) toward CO insertion has been explored. New, mononuclear Pt (II) complexes containing one or two PPO ligands, [PtClMe (kappa2-PPO)] (1), [Pt{C (O) Me}Cl (kappa2-PPO)] (2), [PtMe (CO)(kappa2-PPO)] OTf (3 x OTf), [PtMe (OTf)(kappa2-PPO)] (4), trans-[PtClMe (kappa1-PPO) 2] (5), [PtMe (kappa2-PPO)(kappa1-PPO)] BF4 (6 x BF4), [PtMe (kappa2-PPO)(kappa1-PPO)] OTf (6 x OTf), and [Pt{C (O) Me}(kappa2-PPO)(kappa1-PPO)] BF4 (7 x BF4) have been prepared and characterized. Hemilability of the ligands is observed in the cations 6 and 7 in which the terminally bound and chelating PPO ligands exchange their role on the NMR time-scale. The acetyl complexes 2 and 7 are stable in solution, but the former deinserts CO upon chloride abstraction. We also demonstrate the ability of PPO to behave as an assembling ligand and to stabilize a heterometallic Pt-Ag metal complex, [PtMe (kappa2-PPO){mu-(eta1-P;eta1-O) PPO)}Ag (OTf)(Pt-Ag)] OTf (8 x OTf), which was obtained by reaction of 5 with AgOTf to generate more reactive, cationic complexes. Whereas the first equivalent of AgOTf abstracted the chloride ligand, the second equivalent added to the cationic complex with formation of a Pt-Ag bond (2.819 (1) A). The complexes 1, 2, 4, 5 x CH2Cl2, and (8 x OTf) 2 have been structurally characterized by single-crystal X-ray diffraction. The latter has a dimeric nature in the solid state, with two silver-bound triflates acting as bridging ligands between two Pt-Ag moieties. In addition to the Ag-Pt bond, the Ag+ cation is stabilized by a dative O --> Ag interaction involving one of the PPO ligands. |
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