PNP pincer-type complexes of titanium(III) and -(IV) have been prepared, characterized, and proven to be remarkably stable, despite having terminal alkylidene, phosphinidene, and imide functionalities.

The PdII complexes [PO]Pd(Me)(py) (1a−c; [PO] = 2-PAr2-4-Me-benzenesulfonate); Ar = 2-Et-Ph (a), 2-OMe-Ph (b), Ph (c)) catalyze the copolymerization of ethylene and vinyl fluoride in toluene at 80 °C to produce fluorinated polyethylene. Low levels (0.1−0.5 mol %) of vinyl fluoride incorporation are observed. At 80 psi vinyl fluoride and 220 psi ethylene, 1a produces a linear copolymer with M w = 35000, M w/M n = 3.0, and 0.17 mol % vinyl fluoride incorporation. At a total pressure of 300 psi, increasing the proportion of vinyl fluoride in the feed results in an increase in the level of vinyl fluoride incorporation (to 0.45 mol %) and a decrease in polymer yield and molecular weight. 1a is more reactive and produces higher molecular weight copolymer than 1b,c, but all three catalysts incorporate similar levels of vinyl fluoride. Control experiments rule out a radical copolymerization mechanism, and an insertion mechanism is proposed.

A Rh complex of a bulky diarylamino-based PNP pincer ligand is a robust catalyst for the dimerization of terminal alkynes and highly selective for the trans-enyne product.

The rigid PNP pincer ligand (PNP ) deprotonated anion of bis(ortho-diisopropylphoshinoaryl)amine) is shown to stabilize the (ZrdCHR) 2+ fragment. (PNP)Li(THF) (2-THF) contains P-Li bonds, as evinced by the observation of the Li-P coupling in the solution 31 P NMR spectrum and by the X-ray structural determination in the solid state. 2-THF reacts with ZrCl 4 (Et 2 O) 2 to give (PNP)ZrCl 3 (3). (PNP)ZrCl 3 (3) can be alkylated with RCH 2 MgCl to give (PNP)Zr(CH 2 R) 3 (4a-c). (PNP)ZrMe 3 (4a) is thermally stable, and its solid-state structure is characterized by severe distortions from the octahedral geometry. The (PNP)Zr(CH 2 R) 3 (R ) phenyl (4b) or p-tolyl (4c)) compounds undergo R-abstraction at ambient temperature to give isolable Zr alkyl/alkylidenes (PNP)Zr(dCHR)(CH 2 R) (5b,c). The reaction follows a first-order rate law (t 1/2 at 298 K ≈ 2.3 h). The activation parameters were determined from the VT NMR studies (4b f 5b): ∆H q ) 19(1) kcal/mol; ∆S q ) -14(3) cal/(mol K); ∆G q 298 ) 23( 2) kcal/mol. The importance of the enforcement of the phosphine coordination by the rigid PNP ligand is discussed.