Di­chloro­bis­(tri­phenyl­phosphine oxide)­magnesium

The compound [MgCl₂(C₁₈H₁₅OP)₂] was inadvertantly crystallized during a reaction involving magnesium germanide. It is isostructural to the Mn, Co, Cu and Zn analogs. Since four-coordinate Mg is rare, its structure is reported here. The Mg atom lies on a twofold axis and is surrounded by two O atoms and two Cl atoms in a distorted tetrahedral coordination geometry.

Key indicators

• Single-crystal X-ray study
• T = 90 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.023
• wR factor = 0.061
• Data-to-parameter ratio = 24.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           30.00
         From the CIF: _reflns_number_total               4774
         From the CIF: _diffrn_reflns_limit_ max hkl   26.   45.   13.
         From the CIF: _diffrn_reflns_limit_ min hkl  -26.  -45.  -13.
         TEST1: Expected hkl limits for theta max
         Calculated maximum hkl   29.   45.   13.
         Calculated minimum hkl  -29.  -45.  -13.
          ALERT: Expected hkl max differ from CIF values

REFLT_03
         From the CIF: _diffrn_reflns_theta_max           30.00
         From the CIF: _reflns_number_total               4774
         Count of symmetry unique reflns         2524
         Completeness (_total/calc)            189.14%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured      2250
         Fraction of Friedel pairs measured     0.891
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.

---

S1. Comment

Dichlorobis(triphenylphosphine oxide)magnesium, (I), was prepared serendipitously from the reaction of germanium tetrachloride, triphenylphosphine and magnesium germanide in 2-methoxyethyl ether. We were interested in trapping intermediates formed during the preparation of germanium nanoclusters (Taylor et al., 1999) with triphenylphosphine and obtained colorless parallelepiped crystals of (I).

Crystals of (I) are orthorhombic and crystallize in space group Fdd2 as do its analogues where magnesium is replaced with zinc (Rose et al., 1980; Kosky et al., 1982), copper (Bertrand & Kalyanaraman, 1971; Weinberger, 1997), cobalt (Cotton et al., 2002), and manganese (Tomita, 1985). The only notable difference is that (I) has a more idealized tetrahedral coordination, with bond angles about the metal atom ranging from 101.44 (5) to 113.54 (3)°. Table 1 compares various geometric parameters of the M^II isomorphs. The dihedral angle between the O—M—O' and Cl—M—Cl' planes is another measure of distortion from idealized tetrahedral geometry since an angle of 90° would correspond to tetrahedral and 0° would correspond to square planar. This angle is similar in all of the complexes except in the Cu complex. It shows considerable flattening of the tetrahedral geometry, as has been previously noted (Rose et al., 1980; Kosky, et al., 1982; Weinberger et al., 1997). Compound (I) is soluble in polar organic solvents, such as chloroform and dichloromethane, supporting the use of phosphine oxides as extraction agents for alkaline earth metals (Arnaud-Neu et al., 1999).

S2. Experimental

2-Methoxyethyl ether was distilled twice under argon from sodium and benzophenone prior to use. A degassed solution of triphenylphosphine (0.345 g, 1.32 mmol) and germanium tetrachloride (0.15 ml, 0.282 g, 1.32 mmol) and 20 ml of 2-methoxyethyl ether was added to a 250 ml Schlenk flask containing magnesium germanide (53 mg, 0.437 mmol) and 2-methoxyethyl ether (20 ml). The resultant mixture was refluxed for 18 h and cooled. Volatiles were removed in vacuo. Solids were dissolved in 10 ml of dried, degassed dichloromethane and separated from a small amount of solids via cannula. Over the period of several months crystals of (I) formed from this solution.

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SMART; data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1994); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. View of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) 1.5 − x, 0.5 − y, z.]

(I)

Crystal data

[MgCl2(C18H15OP)2]	F(000) = 2704
Mr = 651.75	Dx = 1.319 Mg m^−3
Orthorhombic, Fdd2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: F 2 -2d	Cell parameters from 718 reflections
a = 20.786 (2) Å	θ = 2.3–30.5°
b = 32.459 (3) Å	µ = 0.35 mm^−1
c = 9.7270 (11) Å	T = 90 K
V = 6562.8 (12) Å^3	Parallelepiped, colorless
Z = 8	0.43 × 0.23 × 0.13 mm

Data collection

Bruker SMART 1000 diffractometer	4774 independent reflections
Radiation source: normal-focus sealed tube	4691 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 8.3 pixels mm^-1	θmax = 30.0°, θmin = 2.3°
ω scans	h = −26→26
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	k = −45→45
Tmin = 0.865, Tmax = 0.956	l = −13→13
21340 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.023	H-atom parameters constrained
wR(F^2) = 0.061	w = 1/[σ^2(Fo^2) + (0.0408P)^2 + 2.5125P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max = 0.002
4774 reflections	Δρmax = 0.32 e Å^−3
196 parameters	Δρmin = −0.16 e Å^−3
1 restraint	Absolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.03 (3)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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
Mg1	0.7500	0.2500	0.72539 (5)	0.01309 (9)
Cl1	0.673718 (12)	0.216943 (9)	0.85434 (3)	0.02282 (6)
P1	0.834324 (12)	0.178146 (7)	0.54955 (3)	0.01390 (6)
O1	0.78833 (4)	0.21078 (2)	0.59911 (9)	0.01861 (14)
C1	0.81838 (5)	0.16767 (3)	0.37141 (11)	0.01635 (18)
C2	0.77734 (6)	0.19449 (4)	0.30159 (14)	0.0258 (2)
H2A	0.7571	0.2164	0.3498	0.031*
C3	0.76586 (8)	0.18932 (4)	0.16188 (15)	0.0343 (3)
H3A	0.7377	0.2075	0.1147	0.041*
C4	0.79591 (8)	0.15726 (4)	0.09152 (14)	0.0322 (3)
H4A	0.7891	0.1541	−0.0045	0.039*
C5	0.83568 (7)	0.12994 (4)	0.16088 (14)	0.0287 (3)
H5A	0.8552	0.1077	0.1127	0.034*
C6	0.84712 (6)	0.13498 (3)	0.30090 (13)	0.0227 (2)
H6A	0.8744	0.1163	0.3483	0.027*
C7	0.91698 (5)	0.19363 (3)	0.56348 (11)	0.01531 (18)
C8	0.95315 (5)	0.20411 (3)	0.44715 (11)	0.0193 (2)
H8A	0.9344	0.2025	0.3582	0.023*
C9	1.01682 (5)	0.21694 (4)	0.46239 (12)	0.0224 (2)
H9A	1.0414	0.2241	0.3836	0.027*
C10	1.04435 (5)	0.21921 (3)	0.59173 (13)	0.0211 (2)
H10A	1.0879	0.2277	0.6013	0.025*
C11	1.00853 (5)	0.20912 (3)	0.70795 (12)	0.0204 (2)
H11A	1.0275	0.2109	0.7966	0.024*
C12	0.94482 (5)	0.19648 (3)	0.69417 (11)	0.0189 (2)
H12A	0.9203	0.1898	0.7735	0.023*
C13	0.82614 (5)	0.13194 (3)	0.64971 (11)	0.01660 (18)
C14	0.76701 (5)	0.12396 (3)	0.71411 (12)	0.0195 (2)
H14A	0.7319	0.1423	0.7021	0.023*
C15	0.76015 (6)	0.08900 (4)	0.79572 (12)	0.0237 (2)
H15A	0.7201	0.0834	0.8387	0.028*
C16	0.81172 (6)	0.06216 (4)	0.81468 (12)	0.0245 (2)
H16A	0.8070	0.0387	0.8722	0.029*
C17	0.87014 (6)	0.06971 (4)	0.74944 (14)	0.0255 (2)
H17A	0.9050	0.0511	0.7612	0.031*
C18	0.87760 (5)	0.10449 (3)	0.66693 (12)	0.0218 (2)
H18A	0.9175	0.1096	0.6224	0.026*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mg1	0.0119 (2)	0.0158 (2)	0.0116 (2)	0.00002 (16)	0.000	0.000
Cl1	0.01663 (10)	0.03282 (13)	0.01900 (12)	−0.00568 (9)	0.00349 (9)	0.00370 (10)
P1	0.01418 (10)	0.01428 (10)	0.01322 (11)	0.00117 (8)	0.00047 (9)	−0.00044 (9)
O1	0.0182 (3)	0.0186 (3)	0.0190 (3)	0.0031 (3)	0.0025 (3)	−0.0026 (3)
C1	0.0185 (4)	0.0160 (4)	0.0146 (5)	−0.0002 (3)	−0.0010 (4)	−0.0007 (3)
C2	0.0332 (6)	0.0221 (5)	0.0221 (5)	0.0074 (4)	−0.0068 (5)	−0.0011 (4)
C3	0.0484 (8)	0.0292 (6)	0.0252 (6)	0.0042 (6)	−0.0137 (6)	0.0021 (5)
C4	0.0512 (8)	0.0293 (6)	0.0162 (5)	−0.0069 (5)	−0.0058 (5)	−0.0015 (4)
C5	0.0409 (7)	0.0239 (5)	0.0214 (6)	−0.0009 (5)	0.0014 (5)	−0.0074 (4)
C6	0.0289 (5)	0.0190 (4)	0.0203 (5)	0.0046 (4)	−0.0007 (4)	−0.0028 (4)
C7	0.0160 (4)	0.0149 (4)	0.0150 (4)	0.0003 (3)	0.0007 (3)	0.0001 (3)
C8	0.0177 (5)	0.0247 (5)	0.0155 (5)	0.0004 (4)	0.0012 (4)	0.0002 (4)
C9	0.0175 (5)	0.0302 (5)	0.0194 (5)	−0.0004 (4)	0.0041 (4)	0.0021 (4)
C10	0.0148 (4)	0.0251 (5)	0.0235 (5)	0.0011 (4)	0.0002 (4)	0.0015 (4)
C11	0.0196 (5)	0.0231 (5)	0.0185 (5)	0.0000 (4)	−0.0032 (4)	0.0011 (4)
C12	0.0198 (5)	0.0223 (5)	0.0147 (5)	−0.0015 (4)	0.0009 (4)	0.0012 (4)
C13	0.0186 (5)	0.0167 (4)	0.0145 (4)	−0.0013 (3)	−0.0013 (3)	0.0005 (3)
C14	0.0222 (5)	0.0191 (4)	0.0172 (5)	−0.0017 (4)	0.0030 (4)	−0.0020 (4)
C15	0.0307 (6)	0.0220 (5)	0.0183 (5)	−0.0065 (4)	0.0060 (4)	−0.0013 (4)
C16	0.0363 (6)	0.0205 (5)	0.0166 (5)	−0.0071 (4)	−0.0043 (4)	0.0037 (4)
C17	0.0269 (6)	0.0223 (5)	0.0273 (6)	−0.0018 (4)	−0.0088 (5)	0.0066 (4)
C18	0.0185 (5)	0.0214 (5)	0.0255 (5)	0.0000 (4)	−0.0039 (4)	0.0050 (4)

Geometric parameters (Å, º)

Mg1—O1	1.9401 (8)	C8—C9	1.3953 (16)
Mg1—O1^i	1.9401 (8)	C8—H8A	0.9500
Mg1—Cl1^i	2.2889 (4)	C9—C10	1.3841 (17)
Mg1—Cl1	2.2889 (4)	C9—H9A	0.9500
P1—O1	1.5062 (8)	C10—C11	1.3926 (16)
P1—C7	1.7952 (10)	C10—H10A	0.9500
P1—C13	1.7966 (11)	C11—C12	1.3929 (15)
P1—C1	1.7966 (11)	C11—H11A	0.9500
C1—C2	1.3954 (15)	C12—H12A	0.9500
C1—C6	1.3976 (15)	C13—C18	1.4021 (15)
C2—C3	1.3899 (19)	C13—C14	1.4036 (15)
C2—H2A	0.9500	C14—C15	1.3922 (16)
C3—C4	1.393 (2)	C14—H14A	0.9500
C3—H3A	0.9500	C15—C16	1.3933 (18)
C4—C5	1.388 (2)	C15—H15A	0.9500
C4—H4A	0.9500	C16—C17	1.3920 (18)
C5—C6	1.3922 (17)	C16—H16A	0.9500
C5—H5A	0.9500	C17—C18	1.3936 (15)
C6—H6A	0.9500	C17—H17A	0.9500
C7—C12	1.3999 (15)	C18—H18A	0.9500
C7—C8	1.4005 (15)
O1—Mg1—O1^i	101.44 (5)	C9—C8—C7	119.73 (10)
O1—Mg1—Cl1^i	111.72 (3)	C9—C8—H8A	120.1
O1^i—Mg1—Cl1^i	108.90 (3)	C7—C8—H8A	120.1
O1—Mg1—Cl1	108.90 (3)	C10—C9—C8	120.30 (10)
O1^i—Mg1—Cl1	111.72 (3)	C10—C9—H9A	119.8
Cl1^i—Mg1—Cl1	113.54 (3)	C8—C9—H9A	119.8
O1—P1—C7	112.73 (5)	C9—C10—C11	120.29 (10)
O1—P1—C13	110.70 (5)	C9—C10—H10A	119.9
C7—P1—C13	106.46 (5)	C11—C10—H10A	119.9
O1—P1—C1	108.95 (5)	C10—C11—C12	119.96 (11)
C7—P1—C1	107.60 (5)	C10—C11—H11A	120.0
C13—P1—C1	110.34 (5)	C12—C11—H11A	120.0
P1—O1—Mg1	157.64 (6)	C11—C12—C7	119.99 (10)
C2—C1—C6	119.75 (11)	C11—C12—H12A	120.0
C2—C1—P1	117.65 (8)	C7—C12—H12A	120.0
C6—C1—P1	122.56 (8)	C18—C13—C14	119.83 (10)
C3—C2—C1	120.36 (12)	C18—C13—P1	121.54 (8)
C3—C2—H2A	119.8	C14—C13—P1	118.62 (8)
C1—C2—H2A	119.8	C15—C14—C13	119.64 (10)
C2—C3—C4	119.57 (12)	C15—C14—H14A	120.2
C2—C3—H3A	120.2	C13—C14—H14A	120.2
C4—C3—H3A	120.2	C14—C15—C16	120.41 (11)
C5—C4—C3	120.37 (12)	C14—C15—H15A	119.8
C5—C4—H4A	119.8	C16—C15—H15A	119.8
C3—C4—H4A	119.8	C17—C16—C15	120.06 (10)
C4—C5—C6	120.16 (12)	C17—C16—H16A	120.0
C4—C5—H5A	119.9	C15—C16—H16A	120.0
C6—C5—H5A	119.9	C16—C17—C18	120.13 (11)
C5—C6—C1	119.76 (11)	C16—C17—H17A	119.9
C5—C6—H6A	120.1	C18—C17—H17A	119.9
C1—C6—H6A	120.1	C17—C18—C13	119.92 (11)
C12—C7—C8	119.72 (9)	C17—C18—H18A	120.0
C12—C7—P1	118.86 (8)	C13—C18—H18A	120.0
C8—C7—P1	121.39 (8)

Symmetry code: (i) −x+3/2, −y+1/2, z.