Chemistry of Bridging Phosphanes: A Comparative Study within Cu^I‐Ag^I‐Au^I Triad‐Based Homonuclear Dimers

Abstract

Bridging ligands in Ag(I) and Au(I) bimetallic complexes: The P moiety of bis(2-pyridyl)phosphole acts as a symmetrically, semi-, or non-bridging donor in Ag(I) dimers (see figure). In related Au(I) complexes, only the non-bridging mode is observed. An unsaturated Ag(I) dimer is used as an adaptive molecular clip for the synthesis of pi-stacked metallocyclophanes.Bis(2-pyridyl)phosphole C reacted with AgPF(6) and dppm giving rise to dicationic dimer 1 in which C acts as a 1kappaN:1,2kappaP:2kappaN-donor with a symmetrically bridging P-centre. This complex gives the first example of dimers based on trigonal planar metal centres bearing a bridging sigma(3),lambda(3)-phosphane ligand. The reaction of two equivalents of C with AgPF(6) and Ag{Al[OC(CF(3))(3)](4)} afforded dicationic dimers 2 and 3 of general formula Ag(2)(C)(2) (2+), respectively. X-ray diffraction studies showed that one ligand C acts as a 1kappaN:1,2kappaP:2kappaN-donor with a symmetrically bridging P-centre and one behaves as a 1kappaN:2kappaP-chelate. In complex 3, one toluene molecule interacts with an Ag centre, giving the first example of a mixed coordination dimer featuring a bridging P-donor. Ag(I)-dimers 4 a-c of the general formula Ag(2)(C)(3) (2+), 2 X(-) (X=PF(6), BF(4), Al[OC(CF(3))(3)](4)) have been prepared according to different routes and characterised by X-ray diffraction study. In these derivatives, C exhibits a variety of coordination modes depending on the nature of the counteranion and of the solvent molecules included in the asymmetric units. These complexes can feature 0, 1, or 2 bridging P-donors. These results definitively demonstrate that the P-centre of phosphane ligands can easily switch from a bridging to a semi-bridging and a non-bridging coordination mode. Dimer 2 is used as an "adaptive" molecular clip for the synthesis of pi-stacked metallocyclophanes 7 a, b and 8 upon reaction with ditopic linkers. X-ray diffraction studies revealed that these supramolecular species behave as receptors for the counteranions (PF(6), BF(4)) and that the nature of the anion impacts the stereochemistry of the supramolecular metallocyclophanes. Au(I)-Dimers 10 a, b bearing two ligands C acting as 1kappaN:2kappaP-chelates are prepared and characterised in the solid-state.

Chiral and Extended π‐Conjugated Bis(2‐pyridyl)phospholes as Assembling N,P,N Pincers for Coordination‐Driven Synthesis of Supramolecular [2,2]Paracyclophane Analogues

“…The intermetallic distances within the Cu 2 fragments (2.9351(10)-3.0060(9) ) are among the longest observed to date for an M I dimer (M = Cu I , Ag I , Pd I , Pt I ) assembled by a bis(2-pyridyl)phosphole ligand with a bridging phosphane (the previous longest distance was 2.9501(6) ). [20] Nevertheless, the two mPÀCu distances are almost the same and in the range of those classically observed for bridging phosphole donors (Table 5). Despite these rather long intermetallic distances within the molecular clips, the p walls of rectangle C (Figure 7) in the solid state to form infinite p-stacked columns.…”

“…For example, multidipolar NLOphore A [16] and metal-bisA C H T U N G T R E N N U N G (helicene) assembly B [17] were obtained by stereoselective coordination of predesigned p-conjugated P,N ligands to a Pd 2 + center ( Figure 1). In this context, 2,5-bis(2-pyridyl)phosphole 1 a 1 (Scheme 1) plays a special role because it is an effective N,P,N pincer ligand for the stabilization of a variety of metal dimers, including Pd I , [18] Pt I , [19] Ag I , [20] and Cu I [21] ions. In these complexes, 1 a 1 acts as a six-electron m-1kN:1,2kP:2kN…”

The Variable Binding Modes of Phenylbis(pyrid‐2‐ylmethyl)phosphane and Bis(pyrid‐2‐ylmethyl) Phenylphosphonite with AgI and CuI

“…Cu2 has a distorted tetrahedral geometry due to both the chelating behavior of one of the ligands and the bridging interaction presented through P2, ranging the angles from 53.28(5)°to 159.20(17)°. The terminally bound ligand shows a close pyridyl π separation of 3.653 Å and an angle of 17.22 (26)°. This favorable π-stacking interaction may help account for the close proximity of Cu1 to Cu2, allowing for the opposing phosphane to undergo the 3-centered bridge.…”

“…Examples have been reported for several late transition metals including Pt II , Pd II , [18][19][20] Rh I , [21,22] Cu I , [23,24] and most recently Ag I . [25,26] In the case of Cu and Ag a very sterically constrained phosphazole was used as the bridging ligand. On the other hand, 2 (see Scheme 2) has been recently described [6] and the catalytic ability of its Ni +2 complex to oligomerize ethylene was studied.…”

Synthesis and Structural Characterization of Lithium and Iron Complexes Containing a Chelating Phenolate Phosphane Ligand

“…[24,[29][30][31][32] The difference of 0.1778 Å between the P1-Fe1 and P1-Fe2 distances highlights the semi-bridging nature of this phosphane donor. [33][34][35] The Fe-Fe distance of 2.824(1) Å in Fe 2 (L Ph ) 2 -(THF) 2 is substantially longer than those found in the diiron site of Fe-only hydrogenase structures (ca. 2.60 Å) [36,37] and their model complexes, such as Fe 2 (μ-S 2 C 3 H 6 )(CO) 6 [2.510(1) Å] [38] and [Fe 2 (μ-S 2 C 3 H 6 )(CO) 4 [42] Solution NMR spectroscopic studies showed that Fe 2 (L Ph ) 2 (THF) 2 is 31 P NMR silent, indicating this compound to be paramagnetic.…”