Bis{(2-diphenylphosphino)phenyl}mercury: A P-Donor Ligand and Precursor to Mixed Metal−Mercury (d⁸−d¹⁰) Cyclometalated Complexes Containing 2-C₆H₄PPh₂

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-C6H4PPh2)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-Ph2PC6H4C6H4PPh2-2 (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, P1̄, with a = 12.720(3) Å, b = 13.154(3) Å, c = 12.724(2) Å, 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, P1̄, 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.将氯化汞(II)（HgCl₂）与2-锂代(二苯基膦基)苯（2-LiC₆H₄PPh₂）反应，可得到二[2-(二苯基膦基)苯基]合汞(II)（记为化合物1）。该化合物的磷原子能分别与氧、硫及硼烷结合，得到相应配合物[Hg{2-C₆H₄P(X)Ph₂}₂]，其中X分别为O（化合物3）、S（化合物4）与BH₃（化合物5）。 化合物1作为双齿配体，具有宽幅可变的咬角（bite angle），可在平面配合物中占据顺式（cis）或反式（trans）配位位点。代表性配合物包括：[HgX₂·1]（X=Cl（6a）、Br（6b））、顺式-[PtX₂·1]（X=Cl（顺式-7）、Me（9）、Ph（10）），以及反式-[MX₂·1]（X=Cl时，M=Pt（反式-7）、Pd（8）、Ni（11）；X=NCS时，M=Ni（13））。上述配合物中，中心金属离子的配位环境分别为四面体（6a、6b）或平面构型（7~11、13）。 在反式-7、8与11中，化合物1以反式构型配位，使得金属与汞原子间存在近距离接触，键长分别为2.8339(7)、2.8797(8)与2.756(8)埃（Å），这暗示存在供体-受体相互作用M→Hg。 将化合物1与[PtCl₂(cod)]（cod为环辛二烯，cyclooctadiene）长时间加热，可得到双核环金属化配合物[(η²-2-C₆H₄PPh₂)Pt(μ-2-C₆H₄PPh₂)₂HgCl]（化合物14）；经六氟磷酸银（AgPF₆）处理后，可衍生得到盐类化合物[(η²-2-C₆H₄PPh₂)Pt(μ-2-C₆H₄PPh₂)₂Hg]PF₆（化合物15）。在化合物14与15中，桥联的μ-C₆H₄PPh₂基团采用头对尾（head-to-tail）排列方式，且化合物14中的Pt-Hg键长为3.1335(5)埃，处于弱亲金属相互作用的典型范围之内。 类似的桥联基团排列模式也存在于[Cl(nBu₃P)Pd(μ-2-C₆H₄PPh₂)₂HgCl]（化合物16）中，该化合物由化合物1与[PdCl₂(PnBu₃)₂]加热反应制得，其中nBu₃P为三正丁基膦（tri-n-butylphosphine）。 将化合物1与[Pd(dba)₂]（dba为二苄基丙酮，dibenzylideneacetone）在室温下反应，可得到[Pd(1)₂]（化合物19）；该化合物在空气中会形成三角平面型钯(0)配合物20，其中包含双齿配位的化合物1，以及单齿配位的膦-膦氧化物配体[Hg(2-C₆H₄PPh₂){2-C₆H₄P(O)Ph₂}]。对化合物19进行加热时，会发生Pd与Hg的消除反应，经还原消除得到C-C偶联产物2-Ph₂PC₆H₄C₆H₄PPh₂-2（化合物18）。 与之相反，化合物1与铂(0)配合物反应则会得到双(芳基)铂(II)物种，其结构式可表示为[Pt(η¹-C-2-C₆H₄PPh₂)(η²-2-C₆H₄PPh₂)(η¹-P-1)]。 各化合物的晶体数据如下： 化合物3：单斜晶系，空间群P2₁/n，晶胞参数a=11.331(3) Å，b=9.381(2) Å，c=14.516 Å，β=98.30(2)°，Z=2。 化合物6b·2CH₂Cl₂：三斜晶系，空间群P$overline{1}$，晶胞参数a=12.720(3) Å，b=13.154(3) Å，c=12.724(2) Å，α=92.01(2)°，β=109.19(2)°，γ=90.82(2)°，Z=2。 化合物trans-7·2CH₂Cl₂：正交晶系，空间群Pbca，晶胞参数a=19.805(3) Å，b=8.532(4) Å，c=23.076(2) Å，Z=4。 化合物11·2CH₂Cl₂：正交晶系，空间群Pbca，晶胞参数a=19.455(3) Å，b=8.496(5) Å，c=22.858(3) Å，Z=4。 化合物14：单斜晶系，空间群P2₁/c，晶胞参数a=13.150(3) Å，b=12.912(6) Å，c=26.724(2) Å，β=94.09(1)°，Z=4。 化合物20·C₆H₅CH₃·0.5CH₂Cl₂：三斜晶系，空间群P$overline{1}$，晶胞参数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)°，Z=2。