A 199Hg NMR spectroscopic study of two and three-coordinate methylmercury(II) complexes, [MeHgL]NO3

¹⁹⁹Hg NMR spectra are reported for the complexes [MeHgL]NO₃ containing either two- (e.g. L = pyridine) or three-coordinate mercury (e.g. L = 2,2′-bipyridyl). For unidentate and bidentate ligands of similar basicity chelation with bidentate ligands to give three-coordinate mercury results in upfield shifts of ¹⁹⁹Hg resonances from that of the linear complexes. For complexes of unidentate ligands shifts correlate with changes in base strength of the ligands, and methyl substitution in the 2 position of pyridine appears to result in an upfield shift of ca. 30 ppm. Effects of substitution in the 2 position are very strong in complexes of unidentate 2-benzylpyridine and 3,3′-dimethyl-2,2′-bipyridyl. Comparison of the ¹⁹⁹Hg shifts with J(¹H-¹⁹⁹Hg) shows the coupling constant to be insensitive to substitution in the 2 position in linear complexes and is a function only of the ligand base strength.     

σ,π-conjugation and 199Hg shielding constants in benzyl derivatives of mercury

The ¹⁹⁹Hg chemical shifts in a number of benzylmercuric chlorides containing methyl substituents in various positions of the benzene nucleus are studied by the heteronuclear ¹H-{¹⁹⁹Hg} double resonance technique. Meta- and para-methyl substituents are shown to have no pronounced action on the shielding whereas ortho-methyl groups each shift the signal by 30 ppm downfield. The observed effect is due to an increase in the population of conformers with the CHg bond lying out of the aromatic cycle plane. The departure from planarity favours conjugation between the electrons of the CHg bond and the π-electronic system of the ring. The J(¹H¹⁹⁹Hg) and J(¹³C¹⁹⁹Hg) coupling constant values obtained in this work confirm the latter conclusion.     

Etude par RMN 13C Et 199Hg de composes oxobromo- et dioxomercuriques

Organomercuric compounds of the general formula

and [RCOCH(R′)]₂Hg, obtained from three ketones, 2,2-dimethyl 3-pentanone, 1-mesityl 1-propanone and 1-mesityl 1-ethanone, have been studied by ¹³C and ¹⁹⁹Hg NMR techniques. Coupling constants J(CHg) and J(HgH) are consistent with C-metalated species; in each case the values of δ(C(2)) and J(C(2)H) observed are higher than expected for purely sp³ carbon. The contribution of O-metalated species and hyperconjugative effects are discussed. For two dioxomercuric compounds (R′  Me, R  t-Bu, mesityl) the existence of diastereoisomers is suggested from ¹⁹⁹Hg NMR data.     

119Sn Chemical Shifts in five- and six-coordinate organotin chelates

¹¹⁹Sn chemical shifts, δ(¹¹⁹Sn), relative to Me₄Sn in five- and six-coordinate organotin chelates were measured by means of FT NMR spectroscopy. ¹¹⁹Sn resonances were found to lie between ca. ?90 and ?330 ppm in the five-coordinate compounds and between ca. ?125 and ?515 ppm in the six-coordinate derivatives. thus δ(¹¹⁹Sn) moves upfield by 60–150 ppm with a change of the coordination number of tin from four to five and by 130–200 ppm from five to six. the δ(¹¹⁹Sn) values were shifted depending on the nature of chelating ligands and this shift was discussed in terms of the bonding between the ligand and tin. Replacement of methyl groups attached to tin by phenyl groups in five- and six-coordinate compounds induces upfield shifts in δ(¹¹⁹Sn) parallel to those found in four-coordinate organotin halides.     

Coordination compounds of [Hg{PPh2[M(CO)5]}2], (M = Cr, Mo, W)

Coordination of various neutral N and O ligands causes drastic changes in ¹J(³¹P-¹⁹⁹Hg) (increase up to the threefold) and δ(³¹P) (shifts up to 30 ppm to low frequencies), which are due to the presence of the M(CO)₅ groups. The complexes with DMSO, phen and bipy were isolated in the solid state. No coordination of [Hg{PCy₂[Cr(CO)₅]}₂] with the above ligands is observed.     

Studies on main group metal-transition-metal bonded compounds 7. A 199Hg NMR study of home group of some group VI trasition-metal mercury compounds

A ¹⁹⁹Hg Fourier Tranformation NMR study has been carried out on Hg[M(CO)₃C₅H₅]₂ (M = Cr, Mo, W), [C₅H₅(CO)₃M]HgCl, and [C₅H₅(CO)₃W]HgX (X = Cl, Br, I, SCN). The ¹⁹⁹Hg chemical shifts are ?80, +115 and ?348 ppm respectively for the symmetrical compounds, ?542, ?617, and ?997 ppm for the chloride and ?1200, ?1529 and ?924 ppm for the Br, I, SCN-tungsten derivatives respectively. The ₁₉₉Hg chemical shifts for several other mercury derivatives are reported for comparison. All chemical shifts are relative to 90% HgMe₂/10% internal lock C₆F₆ with positive values indicating decreasing shielding. The J_199Hg-183W values are 151, 706, 690, 630 and 684 Hz for the symmetrical compound and the Cl, Br, I and SCN derivatives respectively. The factors which may influence these parameters are discussed briefley.     

NMR investigation of bis(2,3-alkanedione dioximato)-bis(pyridine)cobalt(III) iodide complexes: 1H and 13C NMR spectra and 13C spin-lattice relaxation time measurements

The complexes of trans-[Co(III)(R,CH₃-dioxH)₂(py)₂]I2 (R = CH₃, C₂H₅, n-C₃H₇ and n-C₄H₉) were investigated in solution by ¹H and ¹³C NMR spectra and ¹³C spin-lattice relaxation time measurements. The ¹H and ¹³C-resonances of the R = C₂H₅, n-C₃H₇ and n-C₄H₉) groups were shifted to higher field than those of the free ligands by the complexation; it was attributable to the ring current shielding due to the axial pyridine ligands of the complexes. ¹³C spin-lattice relaxation times were interpreted as due to movement of the axial pyridine ligands as if they twist around the CoN (pyridine nitrogen) bond axis and the above R groups were moving segmentally. These segmental movements allowed the R groups to approach closely toward the axial pyridine ring plane to experience the ring current shielding.     

Structural correlations for 1H, 13C and 15N NMR coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with lutidines and collidine

¹H, ¹³C and ¹⁵N NMR studies of gold(III), palladium(II) and platinum(II) chloride complexes with dimethylpyridines (lutidines: 2,3‐lutidine, 2,3lut; 2,4‐lutidine, 2,4lut; 3,5‐lutidine, 3,5lut; 2,6‐lutidine, 2,6lut) and 2,4,6‐trimethylpyridine (2,4,6‐collidine, 2,4,6col) having general formulae [AuLCl₃], trans‐[PdL₂Cl₂] and trans‐/cis‐[PtL₂Cl₂] were performed and the respective chemical shifts (δ^1H, δ^13C, δ^15N) reported. The deshielding of protons and carbons, as well as the shielding of nitrogens was observed. The ¹H, ¹³C and ¹⁵N NMR coordination shifts (Δ^1H_coord, Δ^13C_coord, Δ^15N_coord; Δ_coord = δ_complex ? δ_ligand) were discussed in relation to some structural features of the title complexes, such as the type of the central atom [Au(III), Pd(II), Pt(II)], geometry (trans‐ or cis‐), metal‐nitrogen bond lengths and the position of both methyl groups in the pyridine ring system. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis, 119Sn, 13C and 195Pt NMR studies of five-coordinate rhodium(I), iridium(I) and platinum(II) complexes containing three trichlorostannate ligands

The synthesis and ¹¹⁹Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of Rh^I, Ir^I and Pt^II are reported. The Rh^I and Ir^I complexes are complex dianions of the form (PPN)₂[M(SnCl₃)₃L₂] where L can be CO, CN (cyclohexyl) or L₂, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl₃)₃L₂] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl₃)L₄] including [Ir(SnCl₃)(NBD)(1,5-COD)] have been prepared and characterized. Their δ(¹¹⁹Sn), δ(¹³C), δ(¹⁹⁵Pt) as well as ¹J(¹⁰³Rh, ¹¹⁹Sn), ¹J(¹⁹⁵Pt, ¹¹⁹Sn), ²J(¹¹⁹Sn, ¹¹⁷Sn) and ²J(¹¹⁹Sn, ¹³C) data are given. A trans influence series, based on ¹J(¹⁹⁵Pt, ¹¹⁹Sn), reveals the following sequence: H^? > PR₃ > AsR₃ > SnCl₃^? > olefin > Cl^?.     

Gaseous complexes of cobalt(II) bromide and pyridine

The stepwise decomposition of CoBr₂py₂(s) has been investigated on a thermobalance by the “modified entrainment” method yielding Δ₁H=88.6 kJ mol¹, Δ₁S=156.6 JK^?1 mol^?1 and Δ₂H=119.0 kJ mol^?1, Δ₂S=211.8 JK^?1 mol^?1 for the dissociation of the first and second pyridine. The evaporation of CoBr₂py₂(l) and the association of gaseous pyridine to CoBr₂py(l) forming CoBr₂py₂(g) has been studied by vis spectroscopy at 250?420°C. By combining the new results with literature values, a complete thermodynamic cycle for the solid-liquid-gas equilibria in the CoBr₂-pyridine system could be established. It shows that in solution the formation of CoBr₂py₂ is not determined by the cobalt-pyridine bond energy but by the solvation energy of the rectants.     

Mercury(II) cyanide complexes with alkyldiamines: solid-state/solution NMR,computational, and antimicrobial studies

Mercury cyanide complexes of alkyldiamines (1–6), [Hg(L)(CN)₂] (where L?=?en (1,2-diaminoethane), pn (1,3-diaminopropane), N-Me-en, N, N′-Me₂-en, N, N′-Et₂-en, and N, N′-ipr₂-en), have been synthesized and characterized by elemental analysis, IR, ¹³C, and ¹⁵N solution NMR in DMSO-d₆, as well as ¹³C, ¹⁵N, and ¹⁹⁹Hg solid-state NMR spectroscopy. Complexes 1 and 2 have been studied computationally, built and optimized by GAUSSIAN03 using DFT at B3LYP level with LanL2DZ basis set. Binding modes of en and bn (where bn?=?1,4-diaminobutane) toward Hg(CN)₂ are completely different. Complexes with en and pn show chelating binding to Hg(II), while bn behaves as a bridging ligand to form a polymeric structure, [Hg(CN)₂-bn]_∞ [B.A. Al-Maythalony, M. Fettouhi, M.I.M. Wazeer, A.A. Isab. Inorg. Chem. Commun., 12, 540 (2009).]. The solution ¹³C NMR of the complexes demonstrates a slight shift of the ?C≡N (0.9 to 2?ppm) and ?C–NH₂ (0.25 to 6?ppm) carbon resonances, while the other resonances are relatively unaffected. ¹⁵N labeling studies have shown involvement of alkyldiamine ligands in coordination to the metal. The principal components of the ¹³C, ¹⁵N, and ¹⁹⁹Hg shielding tensors have been determined from solid-state NMR data. Antimicrobial activity studies show that the complexes exhibit higher antibacterial activities toward various microorganisms than Hg(CN)₂.     

1H, 13C and 199Hg NMR Studies of the Complexation of HgCl2 by Imidazolidine-2-Thione and its Derivatives

Abstract

Mercury(II) complexes of imidazolidine-2-thione and its derivatives have been synthesized and their ¹H, ¹³C and ¹⁹⁹Hg NMR spectra measured. HgCl₂ forms L₂HgCl₂ type complexes (where L = imidazolidine-2-thione and its derivatives). The NH group of the ligand is shifted downfield by about +1.37 ppm in the ¹H NMR after complexation. The C-2 carbon in the ¹³C NMR is shifted by—6.50 ppm for mono N-substituted ligands, but by—5.30 ppm for N,N''-disubstituted ligands. The ¹⁹⁹Hg NMR resonance is shifted by about—60 ppm for N-substituted ligands, but—140 ppm shifts were observed for N',N'-disubstituted ligands.     

Variable-temperature and solvent NMR study of bis(μ2-methanethiolato)-bis(dinitrosyliron) and bis(μ2-methaneselenolato)-bis(dinitrosyliron)

The ¹H NMR spectrum of Fe₂(SMe)₂(NO)₄ has been measured in a total of 22 solvents, and the activation barrier ΔG^≠ for the C_2h?C_2v isomerisation in nine of these solvents. In aromatic solvents, the solvent-induced shifts are consistent with the formation of charge-transfer complexes, either 1:1 or 1:n; in non-aromatic, non-halogenated solvents of high dipolarity/polarizability the solvent-induced shifts follow the variation of the solvatochromic parameter, π*. The behaviour of Fe₂(SeMe)₂(NO)₄ in a limited range of solvents is similar. The activation barrier ΔG^≠ in Fe₂(SMe)₂(NO)₄ is ca 78 kJ mol^?1 in the majority of solvents, but that for Fe₂(SeMe)₂(NO)₄ is significantly higher.     

95Mo NMR spectral studies on seven-coordinate molybdenum(II) isocyanide complexes

The ⁹⁵Mo NMR spectra of a series of seven-coordinate molybdenum(II) isocyanide complexes of the types [Mo(CNR)_7-nL_n](PF₆)₂ (R = CH₃, CHMe₂, CMe₃, C₆H₁₁, CH₂Ph; L = py, bpy, Me₂bpy, phen, dppe, P-n-Bu₃; n = 0,1,2) [Mo(CNC-Me₃)₆X]PF₆ (X = Cl, Br, I) and [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)](PF₆)₃ (NN = bpy, Me₂bpy, phen) have been studied. The ⁹⁵Mo chemical shift range for this group of complexes is about 1100 ppm. An increase in the size of the R group attached to the isocyanide ligand generally tends to shield the ⁹⁵Mo nucleus. Replacement of the isocyanide ligand with a phosphorus ligand also increases the shielding, whereas the replacement of isocyanide with a heterocyclic nitrogen donor leads to deshielding by 800–900 ppm. This group of complexes shows a normal halogen dependence, i.e. replacement of Cl^? by Br^? and I^? increases the shielding of the ⁹⁵Mo nucleus. The cyano-bridged cations [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)]³⁺ (NN = bpy, Me₂bpy, or phen) show two ⁹⁵Mo NMR signals, one for the molybdenum coordinated to the carbon of the bridging CN and one for the N-coordinated molybdenum. Comparison of the chemical shifts and linewidths of the cyano-bridged species with those of the corresponding mononuclear molybdenum(II) complexes [Mo(CNCMe₃)₅(NN)](PF₆)₂ leads to the assignment of the more deshielded signal to the N-coordinated molybdenum. The ¹⁴N and ³¹P NMR spectra for these complexes have also been measured, as have the ¹³C NMR spectra of the pairs of complexes [Mo(CNCMe₃)₅(NN)](PF₆)₂ and [{Mo(CNCMe₃)₄(NN)}₂(μ-CN)](PF₆)₃ (NN = bpy or phen). The ¹⁸³W NMR spectra for [W(CNR)₅(bpy)](PF₆)₂ (R = CMe₃ and CH₂Ph), show that the δ(¹⁸³W)/δ(⁹⁵Mo) chemical shift ratios for isocyanide complexes are different from the ratio found for M⁰ and M^VI.     

Stereochemical nonrigidity of the square complex (PPh3)2Pt(HgGePh3)(GePh3)

³¹P, ¹⁹⁵Pt and ¹⁹⁹Hg NMR spectra of complex (PPh₃)₂Pt(HgGePh₃)(GePh₃) (I) have been studied. The spectra at temperatures below ?40°C prove that (I) is a cis-isomer with the square-planar coordination of the Pt atom. The reversibility of temperature dependences of spectra, insensitivity of line shape to the solvent, concentration and presence of free phosphine establish the fluxional behaviour of (I). The activation parameters of the intramolecular rearrangement which is realized, most probably, through a digonal twist, are: Δ^≠₂₉₈ = 51.5 ± 2.9 kJ/mol, ΔH^≠ = 59.3 ± 2.9 kJ/mol, ΔS^≠ = 26.2 ± 9.7 J/mol. K.     

Synthesis,structure, and kinetic studies on [RuCl2(NCCH3)2(cod)]

[RuCl₂(NCCH₃)₂(cod)], an alternative starting material to [RuCl₂(cod)] _n for the preparation of ruthenium(II) complexes, has been prepared from the polymer compound and isolated in yields up to 87% using a new work-up procedure. The compound has been obtained as a yellow solid without water of crystallization. The complexes [RuCl₂(NCR)₂(cod)] spontaneously transform into dimers [Ru₂Cl(μ-Cl)₃(cod)₂(NCR)] (R?=?Me, Ph). ¹H NMR kinetic experiments for these transformations evidenced first-order behavior. [RuCl₂(NCPh)₂(cod)] dimerizes slower by a factor of ten than [RuCl₂(NCCH₃)₂(cod)]. The following activation parameters, ΔH ^#?=?114?±?3?kJ?mol^?1 and ΔS ^#?=?66?±?9?J?K^?1?mol^?1 for R?=?CH₃CN (ΔG ^#?=?94?±?5?kJ?mol^?1, 298.15?K) and ΔH ^#?=?122?±?2?kJ?mol^?1 and ΔS ^#?=?75?±?6?J?K^?1?mol^?1 for R?=?Ph (ΔG ^#?=?100?±?4?kJ?mol^?1, 298.15?K), have been calculated from the first-order rate constants in the temperature range 294–323?K. The kinetic parameters are in agreement with a two-step mechanism with dissociation of acetonitrile as the rate-determining step. The molecular structures of [Ru₂Cl(μ-Cl)₃(cod)₂(NCR)] (R?=?Me, Ph) have been determined by X-ray diffraction.     

Darstellung und spektroskopische Charakterisierung von bindungsisomeren Halogenoselenocyanato-Osmaten(IV) und -Rhenaten(IV)

Preparation and Spectroscopic Characterization of Bond Isomeric Halogenoselenocyanato-Osmates(IV) and -Rhenates(IV) By oxidative ligand exchange of appropriate chloro-iodo complexes of Os^IV or Re^IV with (SeCN)₂ in CH₂Cl₂ or by heterogeneous reaction with Pb(SeCN)₂ or AgSeCN in CH₂Cl₂ the new complexes cis-[OsCl₄(NCSe)(SeCN)]^2?, tr.-[OsCl₄Br(NCSe)]^2?, tr.-[OsCl₄Br(SeCN)]^2?, [ReCl₅(NCSe)]^2?, [ReCl₅(SeCN)]^2?, tr.-[ReCl₄I(NCSe)]^2?, tr.?[ReCl₄(NCSe)(SeCN)]^2? and tr.?[ReCl₄(NCSe)₂]^2? are formed and isolated as pure compounds by ion exchange chromatography on DEAE-cellulose. The bond isomers are significantly distinguished by the frequencies of innerligand vibrations: n?_CN(Se) > n?_CN(N); n?_CSe(N) > n?_CSe(Se); δ_NCSe > δ_SeCN. The electronic spectra (10 K) of the solid salts reveal a bathochromic shift for the charge transfer bands of the Se isomers as compared with the corresponding N isomers. The intra-configurational transitions are observed for the Os^IV complexes at 600 to 2400 and for the Re^IV complexes at 500 to 1600 nm. The ⁷⁷Se nmr signals of the Os^IV bond isomers are registrated for Se binding in the region 970 to 1040 ppm, for N coordination downfield at 1540 to 1640 ppm.     

Thermal [1,5] sigmatropic rearrangements in (σ-7-cycloheptatrienyl)triphenyltin and (σ-5-cyclohepta-1,3-dienyl)triphenyltin: A 1H and 13C NMR reinvestigation

It has been confirmed by ¹H and ¹³C NMR spectroscopies that Sn(σ-C₇H₇)Ph₃ undergoes either 1,4- or 1,5-shifts of the SnPh₃ moiety around the cycloheptatrienyl ring with ΔH³ = 13.8 ± 0.4 kcal mol^?1, ΔS3 = ?5.6 ± 1.2 cal mol^?1 deg^?1, and ΔG³₃₀₀ = 15.44 ± 0.14 kcal mol^?1. Similarly, (σ-5-cyclohepta-1,3-dienyl)triphenyltin undergoes 1,5-shifts with ΔH³ = 12.4 ± 0.6 kcal mol^?1, ΔS³ = ?11.2 ± 1.8 cal mol^?1 deg^?1, and ΔG³₃₀₀ = 15.76 ± 0.13 kcal mol^?1. It is therefore probable that Sn(σ-5-C₅H₅)R₃ and Sn(σ-3-indenyl)R₃ do not undergo 1,2-shifts as previously suggested but really undergo 1,5-shifts.     

195Pt, 119Sn and 31P NMR studies of alkyl,aryl and acyl trichlorostannate complexes of platinum(II). The crystal structure of trans-[Pt(SnCl3)(COC6H5)(PEt3)2]

¹⁹⁵Pt, ¹¹⁹Sn and ³¹P NMR characteristics of the complexes trans-[Pt(SnCl₃)(carbon ligand)(PEt₃)₂] (1a-1e) are reported, (carbon ligand = CH₃ (1a), CH₂Ph (1b), COPh (1c), C₆Cl₅ (1d), C₆Cl₄Y (e); Y = meta- and para-NO₂, CF₃, Br, H, CH₃, OCH₃, or Pt(SnCl₃)(PEt₃)₂. The values of ¹J(¹⁹⁵Pt, ¹¹⁹Sn) vary from 2376 to 11895 Hz with the COPh ligand having the smallest and the C₆Cl₅ ligand the largest value, making a total range for this coupling constant, when the dimer syn-trans-[PtCl(SnCl₃)(PEt₃)]₂ is included, of ca. 33000 Hz. In the meta- and para-substituted phenyl complexes ¹J(¹⁹⁵Pt, ¹¹⁹Sn) (a) is greater for electron-withdrawing substituents, (b) varies more for the meta-substituted derivatives (5634 to 7906 Hz) than for the para analogues (6088 to 7644 Hz) and (c) has the lowest values when the Pt(SnCl₃)(PEt₃)₂ group is the meta- or para-substituent. The direction of the change in ¹J(¹⁹⁵Pt, ¹¹⁹Sn) is opposite to that found for ¹J(¹⁹⁵Pt, ¹¹⁹P). For the aryl complexes linear correlations are observed between δ(¹¹⁹Sn), ¹J(¹⁹⁵Pt, ¹¹⁹Sn), ¹J(¹⁹⁵Pt, ³¹P), ¹J(¹¹⁹Sn, ³¹P) and the Hammett substituent constant σⁿ. δ(¹¹⁹Sn) and ¹J(¹⁹⁵Pt, ¹¹⁹Sn) are related linearly to v(Pt-H) in the complexes trans-[PtH(C₆H₄Y)(PEt₃)₂]; δ(¹¹⁹Sn) and δ(¹H) (hydride) are also linearly related. Based on ¹J(¹⁹⁵Pt, ¹¹⁹Sn), the acyl ligand is suggested to have a very large NMR trans influence. The differences in the NMR parameters for (1a-e) are rationalized in terms of differing σ- and π-bonding abilities of the carbon ligands.The structure of 1c has been determined by crystallographic methods. The complex has a slightly distorted square planar geometry with trans-PEt₃ ligands. Relevant bond lengths (Å) and bond angles (°) are: PtSn, 2.634(1), PtP, 2.324(4) and 2.329(4), PtC, 2.05(1); PPtP, 170.7(6), SnPtC, 173.0(3), SnPtP, 92.1(1), 91.7(1), PPtC, 88.8(4) and 88.3(4). The PtSn bond separation is the longest yet observed for square-planar platinum trichlorostannate complexes, and would be consistent with a large crystallographic trans influence of the benzoyl ligand. The PtSn bond separation is shown to correlate with ¹J(¹⁹⁵Pt, ¹¹⁹Sn).     

31P-NMR and X-Ray Studies of the Complexes [HgX2 (1)]. (1=2, 11-bis (diphenylphosphinomethyl)benzo [c]phenanthrene,X=Cl,I)

The ³¹P{¹H}-NMR characteristics of the complexes [HgX₂( 1 )] and [HgX₂-(PPh₂Bz)₂] (X = NO₃, Cl, Br, I, SCN, CN) and the solid state structures of the complexes [HgCl₂( 1 )] and [HgI₂( 1 )] ( 1 = 2,11-bis (diphenylphosphinomethyl)benzo-[c]phenanthrene) have been determined. The ¹J(¹⁹⁹Hg, ³¹P) values increase in the order CN < I < SCN < Br < Cl < NO₃. The two molecular structures show a distorted tetrahedral geometry about mercury. Pertinent bond lengths and bond angles from the X-ray analysis are as follows: Hg? P = 2.485(7) Å and 2.509 (8) Å, Hg? Cl = 2.525 (8) Å and 2.505 (10) Å, P? Hg? P = 125.6(3)°, Cl? Hg? Cl = 97.0(3)° for [HgCl₂( 1 )] and Hg? P = 2.491 (10) Å and 2.500(11) Å, Hg? I = 2.858(5) Å and 2.832(3) Å, P? Hg? P = 146.0(4)°, I? Hg? I = 116.9(1)° for [HgI₂( 1 )]. The equation, derived previously, relating ¹J(¹⁹⁹Hg, ³¹P) and the angles P? Hg? P and X? Hg? X is shown to be valid for 1 .