Crystal structures vibrational 31p NMR studies of complexes of tertiary phosphine ligands with mercury(II) halides

Abstract The mercury(II) phosphine complexes (R 3 P) 2 HgX 2 (R 3 P = PPh 3 , PEt 3 , 1-phenyldibenzophosphole (DBP), 1-phenyl-3, 4-dimethylphosphole (DMPP); X = Cl, Br, I and PBu 3 ; X = Cl) have been prepared and their solution and solid state structures determined by a combination of elemental analyses, IR, Raman NMR spectroscopy. The structures of (DBP) 2 HgBr 2 ( 1 ), (PPh 3 ) 2 Hg 2 Br 4 ( 2 ), (DMPP) 2 Hg 2 I 4 ( 3 ) and (Bu 3 P) 2 Hg 2 I 4 ( 4 ) have been determined from three-dimensional X-ray data collected by counter methods. Compound 1 crystallizes in space group P 1 with a = 10.568(6), b = 17.390(6), c = 9.610(3) A, α = 106.02(4), β = 100.62(4), γ = 101.41(5)° and Z = 2. Compound 2 crystallizes in space group P 2 1 / a with a = 18.619(7), b = 10.938(4), c = 18.762(5) A, β = 90.36(2)° and Z = 4. Compound 3 crystallizes in space group Pbc 2 1 with a = 8.516(4), b = 19.404(7), c = 19.545(6) A and Z = 4. Compound 4 crystallizes in space group P 2 1 / c with a = 16.450(16), b = 20.609(21), c = 24.263(31) A, β = 109.38(8)° and Z = 8. Compound 1 deviates from ideal C 2 symmetry having slightly different HgBr (2.618(2), 2.604(2) A) and HgP (2.513(3), 2.490(3) A bond distances. The inequivalence of the phosphines is manifested as a second order ABX CP/MAS 31 P{ 1 H} NMR spectrum for 1 . Compound 2 is a symmetric doubly bromide bridged dimer with essentially equivalent HgP (2.40(2), 2.44(2) A) bond distances but its CP/MAS 31 P{ 1 H} NMR spectrum displays two AX resonances, showing that the phosphines are not magnetically equivalent. Compound 3 is a symmetric, doubly iodide bridged dimer having slightly different HgP (2.437(7), 2.470(7) A) bond distances displays three AX resonances in its CP/MAS 31 P{ 1 H} NMR spectrum. Compound 4 is an unsymmetrical doubly iodide bridged dimer [(Bu 3 P) 2 HgI 2 HgI 2 ] having equivalent HgP (2.393(21), 2.391(22) A bond lengths but its CP/MAS 31 P{ 1 H} NMR spectrum shows two ABX resonances arising from the two different molecules in the unit cell with the phosphines being magnetically inequivalent in each molecule. Variable temperature 31 P NMR spectroscopy shows that equilibria between monomeric (R 3 P) 2 HgX 2 and dimeric [R 3 PHgX 2 ] 2 occur in solution for R 3 P = DMPP and Bu 3 P the dimers are very easily formed from the monomers.