Bidentate Chelate Complexes of Palladium(II) with the Carbanion 2-C₆F₄PPh₂and Their Transformation into Complexes Containing Bridging 2-C₆F₄PPh₂

Abstract

ARTICLEsolution by opening of the chelate rings to a tetranuclear complex of the same composition as 5, [Pd 4 (μ-Cl) 4 (μ-2-C 6 F 4 PPh 2 ) 4 ] (6), which is structurally analogous to 1. We now report the behavior of the corresponding bromide, iodide, carboxylate, pseudohalide, and acetylacetonato derivatives, thereby establishing the existence of a family of ortho-palladated compounds of a similar type, i.e., of identical composition but containing either chelate k 2 -P,C-2-C 6 F 4 PPh 2 or bridging μ 2 -P,C-2-C 6 F 4 PPh 2 . We have also discovered two compounds that display both coordination modes. Finally, we report reactions of 5 and 8 with acetonitrile and of 8 with PPh 3 and PCy 3 , which also lead to irreversible opening of the chelate ring.

Cyclopalladated complexes containing 2-C6R4PPh2 ligands (R = H, F): one-electron electrochemical reduction leading to metal–carbon σ-bond cleavage via palladium(i)

“…The 1 H NMR spectrum of 12 is similar to that of 11 and only shows a single methine resonance at δ 6.13 due to the equivalent hfacac groups. The 31 P NMR spectrum shows a multiplet at δ 25.8, the chemical shift being comparable to that of 8 (δ 24.5) 5 The presence of the dangling PPh 2 group in 13 was confirmed by single-crystal X-ray diffraction and the molecular structure is shown in Fig. 3.…”

“…The 1 H NMR spectrum of 12 is similar to that of 11 and only shows a single methine resonance at δ 6.13 due to the equivalent hfacac groups. The 31 P NMR spectrum shows a multiplet at δ 25.8, the chemical shift being comparable to that of 8 (δ 24.5) 5 and to the chemical shifts of the structurally similar complexes [Pd 2 (O,O′-acac) 2 (μ-2-C 6 H 4 PPh 2 ) 2 ] (3) (δ 26.4) and [Pd 2 (O,O′-hfacac) 2 (μ-2-C 6 H 4 PPh 2 ) 2 ] (δ 26.9). 19 In the crystal structure of [Pd 2 (O,O′-hfacac) 2 (μ-2-C 6 F 4 PPh 2 ) 2 ] (12), shown in Fig.…”

“…19 In the crystal structure of [Pd 2 (O,O′-hfacac) 2 (μ-2-C 6 F 4 PPh 2 ) 2 ] (12), shown in Fig. 2 5 and may indicate a weak metal-metal interaction. The bond lengths and angles in 12 are generally comparable to those in 8, although the Pd-O bond lengths are slightly longer (ca.…”

“…3,5,18,19 In the case of 3, the reported method 3 was modified slightly: the salt [Pd 2 (THF) 4 (μ-2-C 6 H 4 PPh 2 ) 2 ][BF 4 ] 4 , generated in situ from [Pd 2 (μ-Br) 4 (μ-2-C 6 H 4 PPh 2 ) 4 ] (250 mg, 0.14 mmol) and AgBF 4 (109 mg, 0.56 mmol) in CH 2 Cl 2 -THF was treated with [Na(acac)] (68 mg, 0.56 mmol) and the mixture was stirred overnight. The product was isolated as reported in 80% yield (209 mg).…”

“…On the reverse scan, an oxidation process was observed at +0.59 V, which may be assigned as above to Br − oxidation. 21 It is worth noting that 7 is rapidly converted into 9 in CH 3 CN 5 and that coordination of CH 3 CN causes the first reduction potential at the palladium centres to become ca. 0.4 V more negative, i.e., the presence of CH 3 CN in the coordination sphere disfavours reduction.…”