Bis[1,2-bis(4-tert-butylphenyl)ethylene-1,2-dithiolato(1−)]nickel(II) pentane 0.25-solvate

Square-planar bis[1,2-bis(4-tert-butylphenyl)ethylene-1,2-dithiolato(1–)]nickel(II) crystallizes on a general position in chiral P41212, where asymmetry is induced by twisting of the aryl rings due to intermolecular t Bu-C—H⋯ringcentroid interactions in the packing pattern.


Chemical context
Group 10 metallodithiolene complexes have elicited considerable and sustained interest because their optical and solidstate properties are well suited for such important applications as reversibly bleaching dyes in neodymium YAG lasers (Mueller-Westerhoff et al., 1991), as robust dyes for optical data storage (Nakazumi et al., 1992), as non-linear optical devices (Deplano et al., 2010) and as conducting (Robertson & Cronin, 2002;Kato, 2004;Ouahab, 1998) or magnetic materials (Robertson & Cronin, 2002;Ouahab, 1998;Faulmann & Cassoux, 2003). Among the ligand type generally, those with aryl (Ar) substituents enjoy the advantages of straightforward synthesis from readily accessible benzoin or benzil precursors and of qualitatively predictable effect upon redox potentials and absorption spectra. Our own interest in complexes featuring such ligands has been motivated by their potential to host, by means of appropriately set dithiolene radicals, coherent quantum states for application in quantum computing and data storage (McGuire et al., 2018). With the aim of broadening the window of redox potentials for the [Ar 2 C 2 S 2 2-] À e À ! [Ar 2 C 2 S . S À ] oxidation, thereby creating the possibility for completely resolving and separately observing these oxidation processes in mixed dithiolene complexes of the form [(Ar 2 C 2 S 2 )M(tpbz)M(S 2 C 2 Ar' 2 )] (tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene; Ar 6 ¼ Ar'), we have undertaken the synthesis and electrochemical characterization of a variety of [Ni(S 2 C 2 Ar 2 ) 2 ] complexes with either electron-withdrawing or electron-donating ring substituents. In the course of this effort, crystalline samples of [Ni(S 2 C 2 (C 6 H 4 -4-t Bu) 2 ) 2 ] that were suited for crystallography were obtained. Herein, the details of this structure are described.

Supramolecular features
For 1, the appreciably longer molecular axis that bisects the dithiolene C-C chelate bonds and the non-planarity/nonorthogonality of the arene rings relative to the NiS 4 C 4 core are features that support the occurrence of P4 1 2 1 2, as seen with similarly elongated molecules bearing a twisted character [cf., for example, ACAGAN (Dowd & Stevens, 2004); BALWAO Redox levels of the dithiolene ligand with typical intraligand bond lengths.

Figure 1
Atom labeling for 1. Displacement ellipsoids are shown at the 50% probability level. For clarity, the disordered t Bu groups (C11!C14A and C41!C44A) are edited to show only one of the two orientations.

Figure 3
Molecules of 1 related by translations along the a axis (left side). Molecules of 1 related by the 2 1 screw axis operation along c (right side). Displacement ellipsoids are drawn at the 50% level, and all H atoms are omitted for clarity. (Trzeciak-Karlikowska et al., 2011); CANCIH (Lin et al., 2021)]. Simple translations relate one molecule of 1 to another along the a-and b-axis directions (Fig. 3, left), while in the direction of the c axis, replication of 1 arises by movement along 2 1 axes that are coincident with the c edges of the cell (Fig. 3, right) and by 4 1 axes positioned parallel to the c axis at the middle of the ac and bc faces. Multiple intermolecular t Bu-C-HÁ Á Áarene centroid and t Bu-C-HÁ Á ÁNiS 2 C 2centroid close contacts appear to play a decisive role in determining the packing symmetry patterns (Fig. 4). The most important of these interactions, as gauged by physical proximity, is the C22-H22AÁ Á ÁNi2S3S4C3C4 centroid contact (2.78 Å ). Table 1 summarizes selected data pertinent to a set of structurally characterized Group 10 and 11 bis(dithiolene) complexes that are symmetrically substituted with the same arene rings, which now includes three complete series for Group 10 (Ar = Ph, MeO-4-C 6 H 4 , t Bu-4-C 6 H 4 ). The database entries included in this tabular survey are NIDPDS01 (Megnamisi-Belombe & Nuber, 1989), NIDPDS03 (Miao et al., 2011), GOLRAA (Sheu & Lee, 1999), BUGDUC (Dessy et al., 1982), SICWOR (Arumugam et al., 2007), SONPUI (Chandrasekaran et al., 2014), SOPMOB (Chandrasekaran et al., 2014), ECEKAA (Miao et al., 2011), DATTUR (Koehne et al., 2022), JUHJUR (Nakazumi et al., 1992), TEYSEW (Kokatam et al., 2007), TIDBEO , and TEYSAS (Kokatam et al., 2007). Constancy of crystal system, space group, and unit-cell dimensions is found only for the Ar = Ph series, primarily owing to the absence versus presence of co-crystallized solvent in the other series. However, [Au(S 2 C 2 (C 6 H 4 -4-t Bu) 2 ) 2 ]ÁCH 2 Cl 2 crystallizes in P4 1 2 1 2 with unit cell parameters nearly identical to those of 1Á0.25(C 5 H 12 ). Nickel-sulfur bond lengths generally assemble tightly at 2.12 Å . Although the resolution for its structure is somewhat more coarse, [Au(S 2 C 2 (C 6 H 4 -4-t Bu) 2 ) 2 ] differs from the Group 10 metal complexes in having, effectively, its dithiolene ligand set halfway between redox states a and b in Fig. 2 such that the Au 3+ ion is paired with three anionic ligand charges arising from one fully reduced dithiolate ligand and one half-oxidized monoanionic ligand. Consequently, its S-C and C-C chelate bond lengths are longer and shorter, respectively, than those in its Group 10 counterparts. Conspicuous among the ' values for these compounds is the relatively large ' 66 angle  Intermolecular arene centroid Á Á ÁH-C t Bu interactions, shown as dashed lines, that guide the packing arrangement for 1. The H23BÁ Á ÁC5!C10 centroid and H32BÁ Á ÁC5!C10 centroid contacts are 3.00 and 2.90 Å , respectively. Symmetry transformation used to generate equivalent molecules: 3 2 À x, À 1 2 + y, 5 4 À z; À 1 2 À x, 1 2 + y, 5 4 À z.

Database survey
observed for one unique Ph group in the [M(S 2 C 2 Ph 2 ) 2 ] (M = Ni, Pd, Pt) series, which has its origin in specific intermolecular phenyl C-HÁ Á Áarene centroid interactions that are not pertinent to 1.

Synthesis and crystallization
[Ni(S 2 C 2 (C 6 H 4 -4-t Bu) 2 ) 2 ], 1. A mixture of 4,4 0 -di-tert-butylbenzoin (0.350 g, 1.1 mmol) and P 4 S 10 (0.355 g, 0.8 mmol) and dioxane (30 ml) in an oven-dried 100 ml three-neck flask was refluxed at 378 K for 12 h under N 2 with continuous stirring. Vapor-diffusion methods were effective in generating crystals of diffraction quality. Crystals grown without interstitial solvent were complicated by significant non-merohedral twinning. However, introduction of n-pentane vapor into a THF solution of 1 produced crystalline 1Á0.25(C 5 H 12 ) that was not subject to this problem or otherwise necessitating special treatment.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (