Di-μ-halogeno-bis[halogeno(triphenylphosphine)mercury(II)], [Ph₃PHgX(μ-X)₂XHgPPh₃], reinvestigated at 120 K forX= Cl and Br, and a second polymorph forX= I, also at 120 K

Abstract

Di-mu-chloro-bis[chloro(triphenylphosphine)mercury(II)], [Hg2Cl4(C18H15P)2], (I), and di-mu-bromo-bis[bromo(triphenylphosphine)mercury(II)], [Hg2Br4(C18H15P)2], (II), have been reinvestigated at 120 K. The molecules of (I) lie across inversion centres in space group P2(1)/n, and in both (I) and (II) the complexes are linked into three-dimensional frameworks by a combination of C-H...X (X = Cl and Br) and C-H...pi(arene) hydrogen bonds. At 120 K, di-mu-iodo-bis[iodo(triphenylphosphine)mercury(II)], [Hg2I4(C18H15P)2], (III), crystallizes as a new polymorphic form having Z' = 1/2, where the complexes lie across inversion centres in space group P2(1)/n; the complexes are linked into sheets by a combination of C-H...I and C-H...pi(arene) hydrogen bonds. In the Z' = 1 polymorph of this compound, a single C-H...I hydrogen bond generates simple chains.

Coordination chemistry of the main group elements with phosphine, arsine and stibine ligands

“…The Ga-P and Ga-X distances are longer than in the tetrahedral GaX 3 P species due to the increased coordination number, but the Ga-P distances differ only slightly with changes in X. The distortions from cubic symmetry are again sufficient to cause loss of the 71 Ga NMR resonances of the cations, and the coordination shifts in the 31 P{ 1 H}NMR spectra are erratic. The reaction of GaCl 3 with o-C 6 H 4 (PMe 2 ) 2 in a 2:1 molar ratio produced an insoluble complex which was probably [GaX 2 {o-C 6 H 4 (PMe 2 ) 2 }][GaX 4 ] containing a distorted tetrahedral cation, although X-ray structural authentication is lacking [170].…”

“…In the absence of chemical problems such as fast exchange on the NMR timescale, all the I = 1/2 nuclei can be observed relatively easily (all have a greater receptivity than 13 C, although 29 Si and 119 Sn have long T 1 's which can be problematic). The quadrupolar nuclei are a more mixed batch, 9 Be and 11 B have small Q's and are easily observed, 27 Al and 71 Ga can be observed if the electric field gradient is sufficiently small, whereas in practice 115 In is only seen in close to cubic symmetry environments. 25 Mg, 67 Zn and 73 Ge all have unfavourable properties: in addition to being quadrupolar, they have low absolute frequencies and poor natural abundance, and although all have been observed in certain high symmetry cases, they are generally not likely to be useful.…”

“…Recent interest has focused on the 1:1 complexes for which isomers of the [Hg 2 X 2 (-X) 2 (PR 3 ) 2 ] type have been found, and on some other stoichiometries, as well as the subtle relationships between 1:1 and 2:1 complexes, especially with phosphines with large cone angles. The large amount of structural data available has also shown that intermolecular effects such as long halide bridges or -stacking play a role in determining the structures adopted [71,72]. The complexes of P n Pr 3 illustrate the complexities observed [72,73].…”

“…The three complexes [GaX 3 {P(SiMe 3 ) 3 }] are anomalous in that the Ga-P bond lengths have the reverse trend with X [178], but we note that two of the structures are solvates, and it is likely that this series is a further example of the subtle effects of other contributions such as molecule-solvate interactions, which can mask the underlying trends. Despite the moderate quadrupole moment, 71 Ga NMR data are usually readily obtained for C 3v [GaX 3 (ER 3 )] complexes, and the gallium chemical shifts exhibit systematic changes with X and E (Table 8), and in some cases 71 Ga-31 P and 69 Ga-31 P couplings are resolved. However, in other symmetries including distorted octahedral, the gallium resonances have not been observed, due to fast relaxation and the resulting extreme line broadening.…”

“…28) which are the only forms isolated in the solid state, although in situ 31 P{ 1 H} NMR studies suggested other species may be present in solution in the presence of excess diphosphine. The structures of the cations are distorted by the small chelate bite of the diphosphine (<P-Ga-P ∼85 • ), and the distortions cause loss of the 71 Ga NMR resonances of the cations as a consequence of the increased electric field gradients and resulting fast relaxation [170,179] (Fig. 29) [170].…”