A Versatile Approach to Access Trimetallic Complexes Based on Trisphosphinite Ligands

Abstract

A straightforward method for the preparation of trisphosphinite ligands in one step, using only commercially available reagents (1,1,1-tris(4-hydroxyphenyl)ethane and chlorophosphines) is described. We have made use of this approach to prepare a small family of four trisphosphinite ligands of formula [CH₃C{(C₆H₄OR₂)₃], where R stands for Ph (1a), Xyl (1b, Xyl = 2,6-Me₂-C₆H₃), ⁱPr (1c), and Cy (1d). These polyfunctional phosphinites allowed us to investigate their coordination chemistry towards a range of late transition metal precursors. As such, we report here the isolation and full characterization of a number of Au(I), Ag(I), Cu(I), Ir(III), Rh(III) and Ru(II) homotrimetallic complexes, including the structural characterization by X-ray diffraction studies of six of these compounds. We have observed that the flexibility of these trisphosphinites enables a variety of conformations for the different trimetallic species.

Keywords: coordination polymer; multidentate ligands; phosphinite; polymetallic; supramolecular chemistry; trimetallic.

Scheme 1

Synthesis of trisphosphinite ligands from 1,1,1-tris(4-hydroxyphenyl)ethane and dihalophosphines.

Figure 1

ORTEP view of the solid structure of compound 1b with thermal ellipsoids set at 50% probability. Hydrogen atoms have been excluded for the sake of clarity.

Scheme 2

Synthesis of gold (2a) and silver (3a) trimetallic complexes, and suggested coordination polymer structure of the copper based compound 4a, based on trisphosphinite 1a.

Figure 2

¹H, ¹H NOESY experiments of compounds 2a, 3a, and 4a. Grey balls in 4a represent C₆H₄-O-PPh₂ moieties.

Figure 3

(a) ORTEP view of the solid structure of compound 2a with thermal ellipsoids set at 50% probability. Hydrogen atoms have been excluded for the sake of clarity. Selected bond distances (Å) and angles (°): Au1–P1, 2.214(3); Au1–Cl1, 2.279(4); Au2–P2, 2.228(3); Au2–Cl2, 2.290(3); Au3–P3, 2.219(3); Au3–Cl3, 2.277(3); P1–O1, 1.631(8); P2–O2, 1.621(7); P3–O3, 1.618(8); P1–Au1–Cl1, 177.66(13); P2–Au2–Cl2, 173.51(11); P3–Au3–Cl3, 177.91(11); O1–P1–Au1, 114.0(3); O2–P2–Au2, 111.0(3); O3–P3–Au3, 115.0(3); (b) intermolecular weak C—H/π interactions (red dotted lines) that produce 1D supramolecular chains of 2a along [1 0 0].

Scheme 3

Reaction of trisphosphinite 1a with several common late transition metal precursors.

Figure 4

ORTEP view of the solid structure of compounds 5a, 6a, and 7a with thermal ellipsoids set at 50% probability. Hydrogen atoms and solvent molecules have been excluded for the sake of clarity. Selected bond distances (Å) and angles (°): Compound 5a: Rh1–P1, 2.2829(16); Rh1–Cl1, 2.3945(15); Rh1–Cl2, 2.4017(16); P1–O1, 1.619(4); P1–Rh1–Cl1, 95.44(5); C1–Rh1–Cl2, 155.27(17); P1–Rh1–Cl2, 91.64(6); Cl1–Rh1–Cl2, 88.57(6); Compound 6a: Ir1–P1, 2.2611(17); Ir1–Cl1, 2.4047(13); Ir1–Cl2, 2.4114(15); P1–O1, 1.625(5); C1–C2, 1.581(14); C1–Ir1–P1, 111.11(18); P1–Ir1–Cl1, 95.92(5); P1–Ir1–Cl2, 92.08(6); O1–P1–Ir1, 115.89(16); Compound 7a (selected from the two independent molecules in the asymmetric unit): Ru1–P1, 2.305(3); Ru1–Cl2, 2.403(3); Ru1–Cl1, 2.418(3); Ru2–P2, 2.300(3); Ru2–Cl4, 2.410(3); Ru2–Cl3, 2.414(3); P1–O1, 1.637(7); P2–O2, 1.651(7); C2–C1, 1.550(19); P1–Ru1–Cl2, 82.72(9); P1–Ru1–Cl1, 92.94(9); Cl2–Ru1–Cl1, 88.98(10); P2–Ru2–Cl4, 82.69(9); P2–Ru2–Cl3, 93.08(9); Cl4–Ru2–Cl3, 88.89(10); O1–P1–Ru1, 114.7(3); O2–P2–Ru2, 115.3(3).

Figure 5

Projection of the crystal structure of 6a along [0 0 1] highlighting intermolecular π-π (red dotted lines) and C—H/π (blue dotted lines) interactions between triiridium compounds. Each molecule of 6a has been highlighted in different colors for clarity, while metal centers are represented as balls.

Scheme 4

Synthesis of trimetallic complexes based on trisphosphinite ligands 1b–d.

Figure 6

ORTEP view of the solid structure of compounds 6c and 6d with thermal ellipsoids set at 50% probability. Hydrogen atoms and solvent molecules have been excluded for the sake of clarity. Selected bond distances (Å) and angles (°): Compound 6c: Ir1–P1, 2.295(6); Ir2–P2, 2.296(7); Ir3–P3, 2.302(8); Ir1–Cl2. 2.396(6); Ir1–Cl1. 2.420(6); Ir2–Cl3, 2.398(8); Ir2–Cl4, 2.398(8); Ir3–Cl6, 2.398(7); Ir3–Cl5, 2.406(6); P1–O1, 1.637(17); P2–O2, 1.65(2); P3–O3, 1.646(19); C1–C2, 1.62(3); P1–Ir1–Cl2, 92.6(2); P1–Ir–Cl1, 92.1(2); Cl2–Ir1–Cl1, 85.0(2); P2–Ir2–Cl3, 90.0(3); P2–Ir2–Cl4, 88.6(3); P3–Ir3–Cl6, 89.9(3); P3–Ir3–Cl5, 92.1(2). Compound 6d: Ir1–P1, 2.2801(14); Ir1–Cl1, 2.3940(17); Ir1–Cl2, 2.4003(16); Ir2–P2, 2.3088(14); Ir2–Cl4, 2.3896(17); Ir2–Cl3, 2.4066(16); Ir3–P3, 2.2862(15); Ir3–Cl5, 2.4000(14); Ir3–Cl6, 2.4146(16); P1–O1, 1.642(4); P2–O2, 1.645(4); P3–O3, 1.638(4); C1–C2, 1.562(7); P1–Ir1–Cl1, 92.05(6); C21–Ir1–Cl2, 98.65(18); P1–Ir1–Cl2, 92.07(5); Cl1–Ir1–Cl2, 86.82(7); P2–Ir2–Cl4, 91.22(5); P2–Ir2–Cl3, 87.27(5); P3–Ir3–Cl5, 90.89(5); P3–Ir3–Cl6, 89.09(6); Cl5–Ir3–Cl6, 89.02(7); O1–P1–Ir1, 112.94(15); O2–P2–Ir2, 115.71(14); O3–P3–Ir3, 113.42(17).

Figure 7

Labeling scheme used for ¹H and ¹³C{¹H} NMR assignments.