Bis{(2-diphenylphosphino)phenyl}mercury: A P-donor ligand and precursor to mixed metal�mercury (d 8 �d 10 ) cyclometalated complexes containing 2-C 6 H 4 PPh 2 .

Abstract

Treatment of HgCl2 with 2-LiC6H4PPh2 gives [Hg(2-C6H4PPh2)2] (1), whose phosphorus atoms take up oxygen, sulfur, and borane to give the compounds [Hg{2-C6H4P(X)Ph2}2] [X = O (3), S (4), and BH3 (5)], respectively. Compound 1 functions as a bidentate ligand of wide, variable bite angle that can span either cis or trans coordination sites in a planar complex. Representative complexes include [HgX2·1] [X = Cl (6a), Br (6b)], cis-[PtX2·1] [X = Cl (cis-7), Me (9), Ph (10)], and trans-[MX2·1] [X = Cl, M = Pt (trans-7), Pd (8), Ni (11); X = NCS, M = Ni (13)] in which the central metal ions are in either tetrahedral (6a,b) or planar (7-11, 13) coordination. The trans disposition of 1 in complexes trans-7, 8, and 11 imposes close metal-mercury contacts [2.8339(7), 2.8797(8), and 2.756(8) Å, respectively] that are suggestive of a donor-acceptor interaction, M→Hg. Prolonged heating of 1 with [PtCl2(cod) gives the binuclear cyclometalated complex [(η2-2-C6H4PPh2) Pt(μ-2-C6H4PPh2)2HgCl] (14) from which the salt [(η2-2-C6H4PPh2)Pt (μ-2-C6H4PPh2)2Hg] PF6 (15) is derived by treatment with AgPF6. In 14 and 15, the μ-C6H4PPh2 groups adopt a head-to-tail arrangement, and the Pt-Hg separation in 14, 3.1335(5) Å, is in the range expected for a weak metallophilic interaction. A similar arrangement of bridging groups is found in [Cl(nBu3P)Pd(μ-2-C6H4 PPh2)2HgCl] (16), which is formed by heating 1 with [PdCl2(PnBu3)2]. Reaction of 1 with [Pd(dba)2] [dba = dibenzylideneacetone] at room temperature gives [Pd(1)2] (19) which, in air, forms a trigonal planar palladium(0) complex 20 containing bidentate 1 and the monodentate phosphine-phosphine oxide ligand [Hg(2-C6H4PPh2) {2-C6H4P(O)Ph2}]. On heating, 19 eliminates Pd and Hg, and the C-C coupled product 2-Ph2PC6H4C6H4 PPh2-2 (18) is formed by reductive elimination. In contrast, 1 reacts with platinum(0) complexes to give a bis(aryl)platinum(II) species formulated as [Pt(η1-C-2-C6H4PPh2) (η2-2-C6H4PPh2) (η1-P-1)]. Crystal data are as follows. Compound 3: monoclinic, P21/n, with a = 11.331(3) Å, b = 9.381(2) Å, c = 14.516 Å, β = 98.30(2)°, and Z = 2. Compound 6b·2CH2Cl2: triclinic, P1, with a = 12.720(3) Å, b = 13.154(3) Å, c = 12.724(2) A, α = 92.01(2)°, β = 109.19(2)°, γ = 90.82(2)°, and Z = 2. Compound trans-7·2CH2Cl2: orthorhombic, Pbca, with a = 19.805(3) Å, b = 8.532(4) Å, c = 23.076(2) Å, and Z = 4. Compound 11·2CH2Cl2: orthorhombic, Pbca, with a = 19.455(3) Å, b = 8.496(5) Å, c = 22.858(3) Å, and Z = 4. Compound 14: monoclinic, P21/c, with a = 13.150(3) Å, b = 12.912(6) Å, c = 26.724(2) Å, β = 94.09(1)°, and Z = 4. Compound 20·C6H5CH3 .0.5CH2Cl2: triclinic, P1, with a = 13.199(1) Å, b = 15.273(2) Å, c 17.850(1) Å, α = 93.830(7), β= 93.664(6), γ = 104.378(7)°, and Z = 2.