Dimorphs of [1,2-bis(diphenylphosphino)ethane]dichloronickel(II)

Abstract

The two known forms, A and B, of [1,2-bis(diphenylphosphino)ethane]dichloronickel(II), [Ni(dppe)Cl₂], were synthesised and identified by IR spectroscopy. The spectra showed that form A had a lower symmetry than form B. The forms were also found to differ by solid-state P-31 NMR spectroscopy and powder X-ray diffraction, but the solution properties were identical. The IR spectrum of the dichloromethane solvate of [Ni(dppe)Cl₂] was the same as that of form B but with a strong additional band due to CH₂Cl₂. The X-ray diffraction pattern from this sample matched that calculated for a previously published crystal structure of [Ni(dppe)Cl₂].CH₂Cl₂, thus identifying the form used in that work. Crystals of form A obtained from acetone were used for a single-crystal X-ray structure determination. Comparison of the molecular structures showed that both forms have the same chelate-ring conformation (delta) but differ in the orientations of the phenyl rings. There is a non-crystallographic two-fold axis in form B which is absent from A, explaining the additional bands present in the IR spectrum of the latter. Solid-state P-31 NMR was better than IR spectroscopy at distinguishing the two forms from each other and from mixtures

Synthesis and characterization of three nickel(ii) carborane complexes containing nido- or closo-carborane diphosphine ligand

“…The coordination sphere of the Ni atom can be described as a square-planar formed by two Cl atoms and two P atoms. The bond length of Ni(1)-Cl(1) is 2.226(2) Å , which is in agreement well with the average distance 2.200 Å in dichloro[1,2-bis(diphenylphosphino)ethane]nickel(II) [26]. The average distance of P-Ni (2.168 Å ) and the P-Ni-P angle (86.88 (7) Ni(1)P(1)C(7)C(8)P(2) five-membered chelating ring, due to the Ni atom out of the plane formed by the other four atoms 0.55 Å , there form an envelope conformation between these five atoms.…”

Structure, magnetism and colour in simple bis(phosphine)nickel(II) dihalide complexes: an experimental and theoretical investigation

“…The analogous complexes of bis(diphenylphosphanyl)ethane, (dppe-2 P)NiX 2 (X = Cl, Br and I), with an ethylene rather than a propylene bridge between the P atoms, are reported to be red (Cl and Br) and deep purple (I), and diamagnetic in the solid state and in solution at all temperatures (van Hecke & Horrocks, 1966), although the initial report of (dppe-2 P)-NiCl 2 indicated that it showed variable amounts of paramagnetism (Booth & Chatt, 1965). The structures of the dichloride and dibromide have been reported multiple times and the compounds are always square planar (Beaudoin et al, 2001;Bomfim et al, 2003;Busby et al, 1993;Rahn et al, 1989;Spek et al, 1987). However, the same complexes (dppe-2 P)NiX 2 (X = Cl, Br and I) have also been reported to exhibit temperature-independent paramagnetism in the solid state (Hudson et al, 1968;Jarrett & Sadler, 1991), while being diamagnetic in solution (Jarrett & Sadler, 1991).…”

A new polymorph, formC, of [1,2-bis(diphenylphosphino)ethane]dichloronickel(II)

“…The Cambridge Structural Database (CSD; Allen & Kennard, 1993), accessed at the Chemical Database Service of the EPSRC (Fletcher et al, 1996), provides three reports of structures for the title compound. Spek et al (1987) reported the structure of the dichloromethane solvate (FUJXUD) which was subsequently re-examined by Busby et al (1993) and designated form B along with a second unsolvated structure (form A, PIFDUD). The structure of form A was later determined with greater precision (PIFDUD01; Davies et al, 1998).…”

“…The structure of form A was later determined with greater precision (PIFDUD01; Davies et al, 1998). Following the notation of Busby et al (1993), we designate the polymorph described here as form C. In the following discussion the various structures (polymorphs) are designated simply by letter as A, B or C and in addition the 150 and 293 K structures presented here are further differentiated as A(150), C(150) and C(293).…”

“…Thus, in addition to Ni in the 2a special positions of the space group I2, the asymmetric unit consists of one Cl and half of the ligand comprising P, the ethane C1, and C2±C13 of the phenyl groups attached to P. The latter are in the 4b general positions. According to Busby et al (1993), molecules of B possess similar but non-crystallographic twofold axial symmetry, while those of A do not due to the disposition of the phenyl groups. In all of the polymorphs, the coordination of Ni remains essentially similar, in the form of a slight tetrahedral distortion from a square-planar arrangement.…”