A Triad of Bis(orthometalated) d(8)-Complexes Containing Four-Membered Rings

摘要

Reaction of 2-LiC6F4PPh2 with [MCl2(SEt2)(2)] in diethyl ether gives the monomeric bis(chelate) complexes trans-[M(kappa(2)-2-C6F4PPh2)(2)] [M = Pt (1), Pd (2)] or, in the case of platinum, a mixture of cis- and trans-isomers. Treatment of a mixture of NiCl2 and 2-BrC6F4PPh2 in THF with zinc dust gives trans-[Ni(kappa(2)-2-C6F4PPh2)(2)] (3). The four-membered chelate rings in 1-3 are opened on addition of the bidentate ligand 1,2-bis(diphenylphosphino)ethane (dppe), and, in the case of 3, 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen), to give complexes of the type cis-[M(kappa C-C6F4-2-PPh2)(2)(L-L)] [L-L = dppe, M = Ni (6), Pd (7), Pt (8); M = Ni, L-L = bipy (9), phen (10)], in which the PPh2 groups are uncoordinated. Complexes 6-8 show unexpectedly large four-bond coupling constants ((4)J(PF)), in the range 75-95 Hz, between the fluorine atoms (F-6) ortho to the metal-carbon sigma-bond and the phosphorus atoms of the PPh2 groups, possibly because F-6 and the lone pairs on phosphorus adopt a close to synperiplanar conformation. Treatment of 2 with [PdCl2(NCMe)(2)] gives the dinuclear complex [Pd-2(mu-Cl)(2)(kappa(2)-2-C6F4PPh2)(2)] (11), which dimerizes in solution to the tetranuclear complex [Pd-4(mu-Cl)(4)(mu-2-C6F4PPh2)(4)] (12) as a result of opening of the chelate 2-C6F4PPh2 rings. Carbon monoxide inserts into a nickel-carbon sigma-bond of 3 to give, after oxidation, bis-2,2'-(diphenylphosphinoyl)octafluorobenzophenone, {2,2'-C6F4P(O)Ph-2}(2)CO (14). The molecular structures of complexes 1-3, 6, 8, 9, and 14 have been determined by single-crystal X-ray methods.