trans-Bis­[O-2,4-di-tert-butyl­phenyl (4-methoxy­phenyl)­di­thio­phosphonato-κ²S,S′]­nickel(II)

In the the title compound, [Ni(C₂₁H₂₈O₂PS₂)₂], the Ni atom resides on an inversion centre and is coordinated in a square-planar array by four S atoms, with Ni—S and P—S bond lengths of 2.2336 (12)/2.2351 (13) and 1.9910 (16)/2.0010 (17) Å, respectively. The two O-2,4-di-tert-butyl­phenyl and two 4-methoxy­phenyl moieties adopt trans configurations about the central Ni atom.

S1. Comment

Owing to their insecticide and antioxidant activities, dithiophosphonate compounds have been widely investigated in medical, industrial and agricultural fields. Despite this, studies on the molecular structures of dithiophosphonate complexes have not been reported adequately up until recently. In recent years, Ni^II complexes of this type have received increasing attention owing to their extensive applications as both antioxidants and antiwear additives in the rubber industry and in lubrication engineering (Harrison & Kikabhai, 1987; Kovtun et al., 1992). Additionally, the adducts and their products are also useful in biological applications (Hao et al., 2001). Consequently, the synthesis, physicochemical investigations and crystal structures of many similar complexes and their adducts have been reported (You et al., 1994; Huang et al., 1995; Hao, Fun et al., 2001; Hao, Jian et al., 2001). A previous study involving a related Ni^II–dithiophosphonate complex, namely trans-bis[O-(n-propyl) (p-methoxyphenyl)dithiophosphonato]nickel(II), has been reported (Özcan et al., 2002). The title complex, (III), was prepared and the structure determined in an extension of our previous research studies.

The Ni atom lies on a crystallographic centre of symmetry and the asymmetric unit consists of half of the nickel(II) complex molecule (Fig. 1). The Ni atom is coordinated by four S atoms and has a trans configuration imposed by the ligands in a square-planar environment. The dihedral angle between the S—Ni—S coordination planes is 88.70 (5)°, and the Ni—S and S—P bond lengths are 2.2336 (12)/2.2351 (13) and 1.9910 (16)/2.0010 (17) Å, respectively. These bond lengths compare well with those found in other related Ni^II complexes (Haiduc et al., 1984; Hoskins & Tiekink, 1985; Arca et al., 1997; van Zyl et al., 1998; Hao, Fun et al., 2001; Hao, Jian et al., 2001; Özcan et al., 2002).

The differences in the Ni—S and S—P bond lengths are comparable with those found in our previous study (Özcan et al., 2002), where the values were 2.2251 (9)/2.2283 (9) and 2.004 (1)/2.008 (1) Å, respectively. These differences were explained by electron delocalization in the P—S π-bonding in our previous work. Similar observations have alos been made in the present and related studies (Ooi & Fernando, 1968; Arora et al., 1978; Hoffmann et al., 1979; Hoskins & Tiekink, 1985; Hao, Fun et al., 2001; Hao, Jian et al., 2001). Small differences in all the geometric parameters around the central Ni atom may also be explained by the steric effect of different molecular groups attached to the P atom in related complexes. The mean Ni—S—P angle in (III) (Table 1) is in good agreement with similar angles found in bis(butyldithiophosphonato)bis(4-aminopyridine)nickel(II) [82.83 (5)°; You et al., 1994] and [Ni{(C₄H₉O)₂PS₂}](pyridine)₂ [82.57°; Liu et al., 1987]. The C—O distance in the O-(2,4-di-tert-butylphenyl) (O-dtb) group is much longer than the range found in bis(p-MePh-diaryldithiophosphato)(1,10-phenanthroline)nickel(II) [1.398 (4)–1.47 (1) Å] and is probably the result of electronic effects from the aromatic ring. All other structural parameters have normal values. The methoxyphenyl group and the main part of O-dtb group (atoms O1, C8–C14 and C18) are individually planar and the dihedral angle between these planes is 62.6 (1)°.

S2. Experimental

Lawesson's reagent, (I) (1.48 g, 3.53 mmol), was treated with 2,4-di-tert-butylphenol (1.45 g, 7.07 mmol) in hot benzene (25 ml), yielding the O-di-tert-butylphenyl ester of dithiophosphonic acid, (II). The title compound, (III), was prepared by the reaction of (II) with nickel(II) acetate in a 1:1 mixture of benzene and acetic acid. The compound crystallizes directly from the reaction medium and these crystals were used for the X-ray study. The purple-coloured compound (III) melts at 515–516 K, is stable well over its melting point, and recrystallizes, upon cooling, just below the melting temperature without any observable change in its colour. IR (KBr, cm^-1): 552 (5) (PS, symmetric), 670 (5) (PS, asymmetric); 1028 (5) (POC).

S3. Refinement

H atoms bonded to C atoms were placed geometrically and all H atoms were treated as riding, with C—H distances of 0.93 and 0.96 Å, and U_iso(H) values of 1.2U_eq(C).

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1993); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

Fig. 1. An ORTEP-3 (Farrugia, 1997) drawing of (III) showing the atom-numbering scheme and ellipsoids at the 40% probability level.

(III)

Crystal data

[Ni(C21H28O2PS2)2]	F(000) = 924
Mr = 873.76	Dx = 1.275 Mg m^−3
Monoclinic, P21/c	Melting point: 515 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 8.1782 (18) Å	Cell parameters from 4916 reflections
b = 32.060 (12) Å	θ = 9.9–18.0°
c = 8.709 (3) Å	µ = 0.72 mm^−1
β = 94.68 (3)°	T = 293 K
V = 2275.8 (12) Å^3	Prism, violet
Z = 2	0.30 × 0.25 × 0.20 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.045
ω–2θ scans	θmax = 26.3°
Absorption correction: ψ scan (North et al., 1968)	h = −10→10
Tmin = 0.814, Tmax = 0.870	k = 0→39
4916 measured reflections	l = −10→0
4611 independent reflections	4916 standard reflections every 120 min
2618 reflections with I > 2σ(I)	intensity decay: 0.9%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.141	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.0613P)^2 + 0.9574P] where P = (Fo^2 + 2Fc^2)/3
4611 reflections	(Δ/σ)max < 0.001
241 parameters	Δρmax = 0.53 e Å^−3
3 restraints	Δρmin = −0.35 e Å^−3

Special details

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ni	0.5000	0.5000	0.5000	0.0394 (2)
S1	0.45582 (14)	0.55703 (4)	0.63830 (14)	0.0495 (3)
S2	0.72010 (14)	0.53133 (4)	0.41663 (13)	0.0474 (3)
P1	0.68335 (14)	0.57097 (4)	0.58638 (13)	0.0417 (3)
O1	0.7092 (3)	0.61873 (9)	0.5419 (3)	0.0468 (7)
O2	1.1623 (5)	0.55785 (14)	1.1311 (4)	0.0924 (13)
C1	1.3164 (8)	0.5383 (2)	1.1210 (7)	0.101 (2)
C2	1.0583 (6)	0.55944 (16)	1.0011 (6)	0.0591 (13)
C3	1.0941 (6)	0.54453 (17)	0.8620 (6)	0.0626 (14)
C4	0.9785 (6)	0.54820 (17)	0.7365 (6)	0.0600 (14)
C5	0.8299 (5)	0.56609 (14)	0.7491 (5)	0.0444 (11)
C6	0.7925 (7)	0.58003 (17)	0.8941 (6)	0.0722 (16)
C7	0.9072 (8)	0.57664 (19)	1.0180 (6)	0.0817 (18)
C8	0.6565 (5)	0.63718 (13)	0.3977 (5)	0.0441 (11)
C9	0.5019 (6)	0.62997 (17)	0.3351 (6)	0.0619 (14)
C10	0.4478 (6)	0.64813 (17)	0.1951 (6)	0.0670 (15)
C11	0.5487 (6)	0.67348 (15)	0.1194 (5)	0.0515 (12)
C12	0.7051 (6)	0.68043 (14)	0.1891 (5)	0.0518 (12)
C13	0.7659 (5)	0.66294 (14)	0.3284 (5)	0.0450 (11)
C14	0.9393 (6)	0.67216 (16)	0.3998 (6)	0.0589 (13)
C15	1.0310 (8)	0.7017 (2)	0.2974 (8)	0.118 (3)
C16	0.9326 (7)	0.69336 (19)	0.5575 (7)	0.091 (2)
C17	1.0413 (6)	0.63234 (19)	0.4230 (7)	0.0759 (17)
C18	0.4914 (7)	0.69379 (16)	−0.0340 (5)	0.0636 (14)
C19	0.3603 (13)	0.6682 (3)	−0.1253 (9)	0.197 (6)
C20	0.4342 (13)	0.7379 (3)	−0.0068 (8)	0.192 (6)
C21	0.6319 (11)	0.6968 (3)	−0.1387 (8)	0.164 (4)
H1A	1.3778	0.5393	1.2197	0.151*
H1B	1.3760	0.5526	1.0464	0.151*
H1C	1.2999	0.5098	1.0901	0.151*
H3	1.1950	0.5320	0.8507	0.075*
H4	1.0038	0.5381	0.6412	0.072*
H6	0.6901	0.5916	0.9069	0.087*
H7	0.8821	0.5861	1.1143	0.098*
H9	0.4319	0.6129	0.3859	0.074*
H10	0.3418	0.6429	0.1525	0.080*
H12	0.7740	0.6980	0.1392	0.062*
H15A	0.9695	0.7271	0.2810	0.177*
H15B	1.0436	0.6885	0.2001	0.177*
H15C	1.1372	0.7080	0.3472	0.177*
H16A	0.8691	0.7185	0.5456	0.137*
H16B	1.0419	0.7000	0.5989	0.137*
H16C	0.8826	0.6748	0.6265	0.137*
H17A	1.1490	0.6393	0.4679	0.114*
H17B	1.0498	0.6190	0.3254	0.114*
H17C	0.9890	0.6138	0.4904	0.114*
H19A	0.4009	0.6405	−0.1406	0.296*
H19B	0.3333	0.6811	−0.2235	0.296*
H19C	0.2640	0.6667	−0.0695	0.296*
H20A	0.5194	0.7530	0.0518	0.287*
H20B	0.3378	0.7372	0.0491	0.287*
H20C	0.4090	0.7516	−0.1040	0.287*
H21A	0.6722	0.6693	−0.1581	0.246*
H21B	0.7189	0.7133	−0.0894	0.246*
H21C	0.5930	0.7096	−0.2345	0.246*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.0371 (4)	0.0491 (5)	0.0315 (4)	0.0008 (4)	0.0003 (3)	0.0013 (4)
S1	0.0450 (7)	0.0550 (7)	0.0496 (7)	−0.0011 (6)	0.0109 (5)	−0.0043 (6)
S2	0.0446 (7)	0.0603 (8)	0.0378 (6)	−0.0032 (6)	0.0067 (5)	−0.0049 (6)
P1	0.0406 (6)	0.0483 (7)	0.0357 (6)	0.0008 (5)	0.0009 (5)	0.0020 (5)
O1	0.0475 (18)	0.0488 (18)	0.0424 (17)	−0.0024 (14)	−0.0061 (14)	0.0057 (14)
O2	0.103 (3)	0.104 (3)	0.062 (3)	0.008 (3)	−0.040 (2)	−0.005 (2)
C1	0.094 (5)	0.108 (5)	0.090 (5)	0.008 (4)	−0.053 (4)	0.018 (4)
C2	0.065 (3)	0.060 (3)	0.048 (3)	0.002 (3)	−0.019 (3)	0.003 (3)
C3	0.047 (3)	0.089 (4)	0.051 (3)	0.010 (3)	−0.001 (2)	0.013 (3)
C4	0.054 (3)	0.085 (4)	0.041 (3)	0.009 (3)	0.000 (2)	0.003 (2)
C5	0.047 (3)	0.049 (3)	0.036 (2)	0.002 (2)	−0.001 (2)	0.004 (2)
C6	0.078 (4)	0.082 (4)	0.055 (3)	0.026 (3)	−0.003 (3)	−0.011 (3)
C7	0.102 (5)	0.101 (5)	0.039 (3)	0.014 (4)	−0.014 (3)	−0.016 (3)
C8	0.042 (2)	0.047 (3)	0.043 (3)	0.003 (2)	−0.001 (2)	0.004 (2)
C9	0.039 (3)	0.083 (4)	0.062 (3)	−0.010 (3)	−0.007 (2)	0.025 (3)
C10	0.046 (3)	0.079 (4)	0.072 (4)	−0.005 (3)	−0.017 (3)	0.022 (3)
C11	0.055 (3)	0.056 (3)	0.042 (3)	0.003 (2)	−0.005 (2)	0.003 (2)
C12	0.055 (3)	0.053 (3)	0.048 (3)	−0.005 (2)	0.006 (2)	0.008 (2)
C13	0.047 (3)	0.048 (3)	0.040 (3)	−0.004 (2)	0.003 (2)	0.001 (2)
C14	0.047 (3)	0.067 (3)	0.061 (3)	−0.013 (3)	−0.004 (2)	0.008 (3)
C15	0.069 (4)	0.160 (7)	0.120 (6)	−0.051 (4)	−0.017 (4)	0.063 (5)
C16	0.085 (4)	0.087 (4)	0.096 (5)	−0.006 (4)	−0.028 (4)	−0.034 (4)
C17	0.049 (3)	0.100 (5)	0.078 (4)	0.003 (3)	0.002 (3)	−0.006 (3)
C18	0.079 (4)	0.066 (3)	0.043 (3)	0.014 (3)	−0.007 (3)	0.006 (2)
C19	0.261 (12)	0.210 (10)	0.100 (6)	−0.110 (9)	−0.115 (7)	0.066 (7)
C20	0.342 (14)	0.155 (8)	0.069 (5)	0.168 (9)	−0.042 (7)	0.009 (5)
C21	0.160 (8)	0.267 (12)	0.068 (5)	0.068 (8)	0.023 (5)	0.079 (6)

Geometric parameters (Å, º)

Ni—S2	2.2336 (12)	C14—C17	1.529 (7)
Ni—S1	2.2351 (13)	C14—C16	1.538 (7)
Ni—P1	2.7942 (14)	C14—C15	1.538 (7)
P1—O1	1.598 (3)	C2—C3	1.356 (7)
P1—C5	1.787 (4)	C3—H3	0.9300
P1—S2	1.9910 (16)	C18—C20	1.515 (8)
P1—S1	2.0010 (17)	C18—C19	1.522 (8)
O1—C8	1.423 (5)	C18—C21	1.527 (8)
C13—C8	1.390 (6)	C17—H17A	0.9600
C13—C12	1.391 (6)	C17—H17B	0.9600
C13—C14	1.530 (6)	C17—H17C	0.9600
C8—C9	1.356 (6)	C16—H16A	0.9600
C11—C10	1.365 (7)	C16—H16B	0.9600
C11—C12	1.388 (6)	C16—H16C	0.9600
C11—C18	1.525 (6)	C1—H1A	0.9600
C12—H12	0.9300	C1—H1B	0.9600
C4—C5	1.356 (6)	C1—H1C	0.9600
C4—C3	1.391 (6)	C15—H15A	0.9600
C4—H4	0.9300	C15—H15B	0.9600
C5—C6	1.397 (6)	C15—H15C	0.9600
C6—C7	1.375 (7)	C20—H20A	0.9600
C6—H6	0.9300	C20—H20B	0.9600
C10—C9	1.391 (7)	C20—H20C	0.9600
C10—H10	0.9300	C19—H19A	0.9600
C9—H9	0.9300	C19—H19B	0.9600
C7—C2	1.372 (7)	C19—H19C	0.9600
C7—H7	0.9300	C21—H21A	0.9600
O2—C2	1.361 (5)	C21—H21B	0.9600
O2—C1	1.416 (7)	C21—H21C	0.9600
S2—Ni—S1	88.70 (5)	C3—C2—C7	120.0 (4)
S2—P1—S1	102.98 (7)	O2—C2—C7	115.7 (5)
P1—S1—Ni	82.34 (6)	C2—C3—C4	119.3 (5)
P1—S2—Ni	82.60 (6)	C2—C3—H3	120.4
O1—P1—C5	100.53 (18)	C4—C3—H3	120.4
O1—P1—S2	113.63 (13)	C20—C18—C19	111.8 (7)
C5—P1—S1	112.16 (16)	C20—C18—C11	109.8 (4)
S2—Ni—P1	44.96 (4)	C19—C18—C11	112.4 (5)
S1—Ni—P1	45.21 (4)	C20—C18—C21	107.0 (7)
C5—P1—S2	113.64 (16)	C19—C18—C21	104.7 (7)
O1—P1—S1	114.38 (13)	C11—C18—C21	110.9 (5)
O1—P1—Ni	142.55 (12)	C14—C17—H17A	109.5
C5—P1—Ni	116.92 (15)	C14—C17—H17B	109.5
S2—P1—Ni	52.44 (5)	H17A—C17—H17B	109.5
S1—P1—Ni	52.44 (4)	C14—C17—H17C	109.5
C8—O1—P1	125.2 (3)	H17A—C17—H17C	109.5
C8—C13—C12	114.9 (4)	H17B—C17—H17C	109.5
C8—C13—C14	123.1 (4)	C14—C16—H16A	109.5
C12—C13—C14	122.0 (4)	C14—C16—H16B	109.5
C9—C8—C13	122.6 (4)	H16A—C16—H16B	109.5
C9—C8—O1	119.3 (4)	C14—C16—H16C	109.5
C13—C8—O1	118.1 (4)	H16A—C16—H16C	109.5
C10—C11—C12	117.1 (4)	H16B—C16—H16C	109.5
C10—C11—C18	121.5 (4)	O2—C1—H1A	109.5
C12—C11—C18	121.4 (4)	O2—C1—H1B	109.5
C11—C12—C13	124.6 (4)	H1A—C1—H1B	109.5
C11—C12—H12	117.7	O2—C1—H1C	109.5
C13—C12—H12	117.7	H1A—C1—H1C	109.5
C5—C4—C3	121.9 (5)	H1B—C1—H1C	109.5
C5—C4—H4	119.0	C14—C15—H15A	109.5
C3—C4—H4	119.0	C14—C15—H15B	109.5
C4—C5—C6	118.2 (4)	H15A—C15—H15B	109.5
C4—C5—P1	121.4 (4)	C14—C15—H15C	109.5
C6—C5—P1	120.5 (4)	H15A—C15—H15C	109.5
C7—C6—C5	119.9 (5)	H15B—C15—H15C	109.5
C7—C6—H6	120.1	C18—C20—H20A	109.5
C5—C6—H6	120.1	C18—C20—H20B	109.5
C11—C10—C9	120.8 (5)	H20A—C20—H20B	109.5
C11—C10—H10	119.6	C18—C20—H20C	109.5
C9—C10—H10	119.6	H20A—C20—H20C	109.5
C8—C9—C10	120.0 (5)	H20B—C20—H20C	109.5
C8—C9—H9	120.0	C18—C19—H19A	109.5
C10—C9—H9	120.0	C18—C19—H19B	109.5
C2—C7—C6	120.7 (5)	H19A—C19—H19B	109.5
C2—C7—H7	119.7	C18—C19—H19C	109.5
C6—C7—H7	119.7	H19A—C19—H19C	109.5
C2—O2—C1	117.7 (5)	H19B—C19—H19C	109.5
C17—C14—C13	111.7 (4)	C18—C21—H21A	109.5
C17—C14—C16	108.0 (5)	C18—C21—H21B	109.5
C13—C14—C16	110.4 (4)	H21A—C21—H21B	109.5
C17—C14—C15	107.8 (5)	C18—C21—H21C	109.5
C13—C14—C15	111.3 (4)	H21A—C21—H21C	109.5
C16—C14—C15	107.5 (5)	H21B—C21—H21C	109.5
C3—C2—O2	124.3 (5)