Synthesis and Structure of Pt(II) Phosphonato-Phosphine Complexes and of a P,O-Stabilized Metal−Metal-Bonded Pt₂Ag₂Complex

Abstract

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.

Steric Effects of the Initiator Substituent Position on the Externally Initiated Polymerization of 2-Bromo-5-iodo-3-hexylthiophene

“…There are at least two possible explanations how steric effects could inhibit the % headgroup incorporation for In2-PPh 3 , one of which is the possible coordination of the oxygen atom of the phosphonate group to the Ni metal center, inhibiting reaction with an incoming ligand. There have been numerous reports of the PdO group coordinating to the metal center via the oxygen atom [62][63][64][65][66][67][68][69][70][71][72][73][74][75] particularly when the two are in close proximity to each other such as the case with In2-PPh 3 where the Ni 3 3 3 O distance is 3.443 A ˚. Such binding would inhibit the dppp ligand exhange reaction as was observed in the 31 P NMR and 1 H NMR, where there was significant amount of In2-PPh 3 remaining after the addition of 1.5 equiv of dppp.…”

Pt–Ag clusters and their neutral mononuclear Pt(ii) starting complexes: structural and luminescence studies

“…For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt01451f chemistry of platinum(II), electron-rich anionic perhalophenyl-8 and/or alkynyl 9,10 complexes have been successfully used in the synthesis of cluster complexes containing Pt(II) → M (M = Cu I , Ag I , Au I , Cd II , Hg II , Tl I , Sn II , Pb II ) donor-acceptor bonds, with Pt(II) → Ag(I) compounds being the most numerous. 8,11,12 Cyclometallating ligands such as 2-phenylpyridine (Hphpy), 2-(2-thienyl)pyridine (Hthpy) or benzo{h}quinoline (Hbzq), are known to enhance the electron-donating ability of Pt(II), allowing the formation of Pt-M bonds, 12-16 even when neutral substrates of the type [Pt(C Ÿ N) 2 ] (C Ÿ N = C, N cyclometallated ligand) [17][18][19] or the cationic [Pt(phpy)9S3] + (9S3 = 1,4,7-trithiacyclononane) 14 were used. Although C,N-cyclometallated complexes of Pt(II) have been well known for a long time, more recently considerable attention has been paid to them due to their attractive photochemical and photophysical properties and they have been the subject of some excellent, comprehensive reviews.…”

Aminophosphines derived from morpholine and N-methylpiperazine: Synthesis, oxidation reactions and transition metal complexes

“…There has been large interest in the use of hybrid ligands or hemi labile ligands having both hard and soft donor centers. These hemi labile ligands form weak metal-oxygen [1], metal-sulfur [2], or metal-nitrogen bonds [3], while phosphorus atom can strongly coordinate to the metal centers. The hard centers in these hemi labile ligands may behave as intramolecular solvent molecules stabilizing the empty coordination site and due to chelate effect these complexes are much more stable than simple solvent adducts.…”