Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807052646/bg2119sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807052646/bg2119Isup2.hkl |
CCDC reference: 667239
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.008 Å
- R factor = 0.045
- wR factor = 0.111
- Data-to-parameter ratio = 26.2
checkCIF/PLATON results
No syntax errors found
Alert level C PLAT241_ALERT_2_C Check High Ueq as Compared to Neighbors for O2 PLAT341_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ... 8 PLAT601_ALERT_2_C Structure Contains Solvent Accessible VOIDS of . 32.00 A 3
Alert level G REFLT03_ALERT_4_G 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. From the CIF: _diffrn_reflns_theta_max 30.04 From the CIF: _reflns_number_total 3407 Count of symmetry unique reflns 1992 Completeness (_total/calc) 171.03% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 1415 Fraction of Friedel pairs measured 0.710 Are heavy atom types Z>Si present yes PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature 293 K PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature . 293 K PLAT791_ALERT_1_G Confirm the Absolute Configuration of C2 = . S PLAT791_ALERT_1_G Confirm the Absolute Configuration of C7 = . S PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints ....... 2
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 3 ALERT level C = Check and explain 6 ALERT level G = General alerts; check 4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 2 ALERT type 2 Indicator that the structure model may be wrong or deficient 2 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check
The crystal structure of tetra[(R)-lactamide-κ2O,O']strontium(II) dibromide was compared with bis[(R)-lactamido-κ2O,O']boron(III) bromide (Bekaert et al., 2007) and tris[(R)-lactamido-κ2 O,O']zinc(II) tetrabromozincate (Bekaert et al., 2005).
For related literature, see: Finlay et al. (2005); Makhijani (2003); Reginster et al. (2007); Stahl et al. (2006).
The title compound was prepared as follows: S-lactamide (0.356 g, 4 mmole) was dissolved in 20 ml of hot ethanol. Strontium dibromide (0.247 g, 1 mmole) was added to this solution with the help of an ultrasonic bath; the reaction medium was kept at 40° C for 48 h. Colourless plates of the title compound slowly appeared in the solution, whereupon crystals suitable for X-ray diffraction were obtained.
H atoms except those bonded to hydroxy O atoms were positioned geometrically and refined using a riding model, with C—H = 0.96–0.98 Å and N—H = 0.86 Å with Uiso(H) = 1.2 (1.5 for methyl groups) times Ueq(C, O). H atoms bonded to hydroxy O atoms were located in a difference map and refined with an O—H distance restrained to 0.82 (1) Å and a common displacement parameter.
Strontium provides some of the most important radioactive isotopes in the environment; e.g., 90Sr (Finlay et al., 2005), a by-product of the fission of uranium and plutonium in nuclear reaction or nuclear weapons, of which large amounts were produced during the Tchernobyl nuclear power plant disaster in 1986. It was later found in milk and vegetables. It is chemically similar to calcium and tends to deposit in bones and teeth. The half-life of 90Sr is 29.1 years emitting beta particules. Another isotope, 89Sr, is the active ingredient in Metastonρe.g, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer (Makhijani, 2003). Cold strontium ranelate (Prodelosρe.g) is the first antiosteoporotic treatment to simultaneously increase bone formation and decrease bone resorption (Reginster et al., 2007). In order to find new ligands of strontium as osteoporosous drugs, a new complex of strontium dibromide and R-lactamide has been studied. Compound (1) (Fig. 1) contains one monomeric octa-coordinated strontium complex cation, [Sr(C3H7NO2)4]2+, and two Br- anions. In the cation, the Sr atom lies on a twofold axis and is surrounded by four R-lactamide ligands coordinated in a bidentate fashion via amide atom O1 (or O6) and hydroxy atom O2 (or O7) and their symmetry equivalents. The Sr coordination in the cation can be approximately described as a very distorted square antiprism arrangement [with square bases: O1 O2 O6i O7i and O1i O2i O6 O7; i: 1 - x, 1 - y, z] with the Sr atom shifted away from these (symmetry realated) least-squares planes by 1.481 (2) Å. The Sr—O (amide) distances are similar within three estimated standard deviations [Sr—O1 (or O1i): 2.533 (3) and Sr—O6 (or O6i): 2.544 (4) Å]; among the Sr—O (hydroxy) distances Sr—O2 (or O2i): 2.535 (4) Å is equivalent to precedent values within three estimated standard deviations but very different from the two other distances Sr—O7 (or O7i): 2.703 (3) Å. All these values can be compared to those found in the poly[[tetaaquatris(monomethyl fumarato)distrontium(II)]monomethyl fumarate] in which the Sr atom is octa- coordinated by oxygen atoms which range from 2.499 (2) to 2.812 (2)Å (Stahl et al., 2006). Among the two possible coordination modes (N,O or O,O) in metal complexes with lactamide or its derivatives described in the literature, the title compound presents the O,O mode like those in the complexes with the [Zn(lactamide)3]2+ (Bekaert et al., 2005) or the [B(lactamide)2]+ (Bekaert et al., 2007) cations.
The packing is charaterized by a number of H-bonds (Table 2). In particular, Br- anions are linked to the cation by N–H···Br and O–H···Br hydrogen bonds, generating a three dimensional network.
The crystal structure of tetra[(R)-lactamide-κ2O,O']strontium(II) dibromide was compared with bis[(R)-lactamido-κ2O,O']boron(III) bromide (Bekaert et al., 2007) and tris[(R)-lactamido-κ2 O,O']zinc(II) tetrabromozincate (Bekaert et al., 2005).
For related literature, see: Finlay et al. (2005); Makhijani (2003); Reginster et al. (2007); Stahl et al. (2006).
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: WinGX (Version 1.63.02; Farrugia, 1999).
[Sr(C3H7NO2)4]Br2 | F(000) = 600 |
Mr = 603.82 | Dx = 1.708 Mg m−3 |
Orthorhombic, P21212 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P22ab | Cell parameters from 25 reflections |
a = 10.385 (2) Å | θ = 3.2–10.4° |
b = 17.919 (2) Å | µ = 5.74 mm−1 |
c = 6.308 (1) Å | T = 293 K |
V = 1173.8 (3) Å3 | Parallelepiped, colourless |
Z = 2 | 0.25 × 0.16 × 0.12 mm |
Enraf–Nonius CAD-4 diffractometer | 2379 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.067 |
Graphite monochromator | θmax = 30.0°, θmin = 2.3° |
ω–2θ scans | h = −14→14 |
Absorption correction: empirical (using intensity measurements) [multi-scan (Blessing, 1995)] | k = 0→25 |
Tmin = 0.27, Tmax = 0.50 | l = 0→8 |
7106 measured reflections | 3 standard reflections every 60 min |
3407 independent reflections | intensity decay: 1% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.111 | w = 1/[σ2(Fo2) + (0.0439P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.99 | (Δ/σ)max < 0.001 |
3407 reflections | Δρmax = 0.68 e Å−3 |
130 parameters | Δρmin = −1.77 e Å−3 |
2 restraints | Absolute structure: Flack (1983), 1415 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.017 (15) |
[Sr(C3H7NO2)4]Br2 | V = 1173.8 (3) Å3 |
Mr = 603.82 | Z = 2 |
Orthorhombic, P21212 | Mo Kα radiation |
a = 10.385 (2) Å | µ = 5.74 mm−1 |
b = 17.919 (2) Å | T = 293 K |
c = 6.308 (1) Å | 0.25 × 0.16 × 0.12 mm |
Enraf–Nonius CAD-4 diffractometer | 2379 reflections with I > 2σ(I) |
Absorption correction: empirical (using intensity measurements) [multi-scan (Blessing, 1995)] | Rint = 0.067 |
Tmin = 0.27, Tmax = 0.50 | 3 standard reflections every 60 min |
7106 measured reflections | intensity decay: 1% |
3407 independent reflections |
R[F2 > 2σ(F2)] = 0.045 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.111 | Δρmax = 0.68 e Å−3 |
S = 0.99 | Δρmin = −1.77 e Å−3 |
3407 reflections | Absolute structure: Flack (1983), 1415 Friedel pairs |
130 parameters | Absolute structure parameter: −0.017 (15) |
2 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
Sr1 | 0.5000 | 0.5000 | 0.22123 (9) | 0.02564 (14) | |
Br2 | 0.46507 (5) | 0.22333 (3) | 0.18621 (9) | 0.04246 (16) | |
O1 | 0.6729 (4) | 0.4010 (2) | 0.1870 (6) | 0.0382 (8) | |
N1 | 0.8257 (5) | 0.3235 (3) | 0.3141 (8) | 0.0451 (11) | |
H1A | 0.8500 | 0.3105 | 0.1891 | 0.054* | |
H1B | 0.8631 | 0.3049 | 0.4237 | 0.054* | |
C1 | 0.7299 (5) | 0.3726 (3) | 0.3381 (9) | 0.0339 (11) | |
O2 | 0.6163 (5) | 0.4554 (2) | 0.5510 (5) | 0.0532 (12) | |
C2 | 0.6915 (5) | 0.3896 (3) | 0.5667 (8) | 0.0358 (11) | |
H2 | 0.7692 | 0.4003 | 0.6494 | 0.043* | |
C3 | 0.6207 (6) | 0.3266 (4) | 0.6677 (10) | 0.0531 (15) | |
H3A | 0.5987 | 0.3398 | 0.8107 | 0.080* | |
H3B | 0.6743 | 0.2830 | 0.6685 | 0.080* | |
H3C | 0.5435 | 0.3166 | 0.5889 | 0.080* | |
O6 | 0.3820 (4) | 0.4505 (2) | −0.1029 (5) | 0.0395 (8) | |
N6 | 0.2431 (5) | 0.3752 (3) | −0.2688 (7) | 0.0512 (13) | |
H6A | 0.2706 | 0.3886 | −0.3916 | 0.061* | |
H6B | 0.1821 | 0.3429 | −0.2586 | 0.061* | |
C6 | 0.2940 (5) | 0.4038 (3) | −0.0976 (8) | 0.0315 (10) | |
O7 | 0.3377 (3) | 0.3834 (2) | 0.2705 (6) | 0.0310 (7) | |
C7 | 0.2392 (5) | 0.3787 (3) | 0.1129 (7) | 0.0293 (10) | |
H7 | 0.2085 | 0.3271 | 0.1016 | 0.035* | |
C8 | 0.1284 (6) | 0.4296 (4) | 0.1775 (11) | 0.0549 (16) | |
H8A | 0.0944 | 0.4135 | 0.3114 | 0.082* | |
H8B | 0.0619 | 0.4274 | 0.0720 | 0.082* | |
H8C | 0.1592 | 0.4799 | 0.1899 | 0.082* | |
H2A | 0.616 (6) | 0.478 (3) | 0.664 (5) | 0.048 (13)* | |
H7A | 0.377 (5) | 0.3439 (18) | 0.284 (10) | 0.048 (13)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Sr1 | 0.0258 (3) | 0.0306 (3) | 0.0205 (2) | −0.0015 (2) | 0.000 | 0.000 |
Br2 | 0.0340 (3) | 0.0484 (3) | 0.0450 (3) | 0.0041 (2) | 0.0001 (2) | −0.0050 (2) |
O1 | 0.046 (2) | 0.046 (2) | 0.0221 (17) | 0.0127 (16) | 0.0012 (16) | −0.0005 (15) |
N1 | 0.045 (3) | 0.055 (3) | 0.036 (2) | 0.021 (2) | 0.009 (2) | 0.000 (2) |
C1 | 0.032 (3) | 0.033 (3) | 0.036 (3) | −0.003 (2) | 0.005 (2) | 0.001 (2) |
O2 | 0.075 (3) | 0.059 (3) | 0.026 (2) | 0.034 (2) | −0.0096 (19) | −0.0134 (18) |
C2 | 0.039 (3) | 0.042 (3) | 0.027 (2) | 0.013 (2) | −0.004 (2) | −0.004 (2) |
C3 | 0.051 (3) | 0.070 (4) | 0.038 (3) | 0.002 (3) | 0.007 (3) | 0.009 (3) |
O6 | 0.043 (2) | 0.050 (2) | 0.0253 (16) | −0.0210 (18) | 0.0001 (15) | 0.0049 (16) |
N6 | 0.053 (3) | 0.074 (4) | 0.027 (2) | −0.032 (3) | −0.001 (2) | 0.003 (2) |
C6 | 0.028 (3) | 0.038 (3) | 0.029 (2) | −0.002 (2) | −0.0001 (19) | 0.000 (2) |
O7 | 0.0345 (17) | 0.0374 (18) | 0.0212 (16) | −0.0033 (14) | −0.0022 (13) | 0.0008 (14) |
C7 | 0.030 (3) | 0.036 (3) | 0.022 (2) | −0.006 (2) | 0.0018 (18) | 0.0018 (18) |
C8 | 0.033 (3) | 0.079 (4) | 0.053 (4) | 0.005 (3) | 0.007 (3) | −0.007 (3) |
Sr1—O1i | 2.533 (3) | C2—H2 | 0.9800 |
Sr1—O1 | 2.533 (3) | C3—H3A | 0.9600 |
Sr1—O2 | 2.535 (4) | C3—H3B | 0.9600 |
Sr1—O2i | 2.535 (4) | C3—H3C | 0.9600 |
Sr1—O6 | 2.544 (4) | O6—C6 | 1.239 (6) |
Sr1—O6i | 2.544 (4) | N6—C6 | 1.307 (7) |
Sr1—O7i | 2.703 (3) | N6—H6A | 0.8600 |
Sr1—O7 | 2.703 (3) | N6—H6B | 0.8600 |
O1—C1 | 1.232 (6) | C6—C7 | 1.513 (7) |
N1—C1 | 1.337 (7) | O7—C7 | 1.429 (6) |
N1—H1A | 0.8600 | O7—H7A | 0.82 (4) |
N1—H1B | 0.8600 | C7—C8 | 1.523 (7) |
C1—C2 | 1.526 (7) | C7—H7 | 0.9800 |
O2—C2 | 1.417 (6) | C8—H8A | 0.9600 |
O2—H2A | 0.82 (4) | C8—H8B | 0.9600 |
C2—C3 | 1.490 (8) | C8—H8C | 0.9600 |
O1i—Sr1—O1 | 170.23 (17) | C2—O2—H2A | 111 (4) |
O1i—Sr1—O2 | 128.95 (12) | Sr1—O2—H2A | 124 (4) |
O1—Sr1—O2 | 60.74 (12) | O2—C2—C3 | 112.8 (5) |
O1i—Sr1—O2i | 60.74 (12) | O2—C2—C1 | 104.1 (4) |
O1—Sr1—O2i | 128.95 (12) | C3—C2—C1 | 112.4 (5) |
O2—Sr1—O2i | 69.71 (18) | O2—C2—H2 | 109.1 |
O1i—Sr1—O6 | 80.46 (13) | C3—C2—H2 | 109.1 |
O1—Sr1—O6 | 91.65 (13) | C1—C2—H2 | 109.1 |
O2—Sr1—O6 | 141.18 (13) | C2—C3—H3A | 109.5 |
O2i—Sr1—O6 | 122.69 (15) | C2—C3—H3B | 109.5 |
O1i—Sr1—O6i | 91.65 (13) | H3A—C3—H3B | 109.5 |
O1—Sr1—O6i | 80.46 (13) | C2—C3—H3C | 109.5 |
O2—Sr1—O6i | 122.69 (15) | H3A—C3—H3C | 109.5 |
O2i—Sr1—O6i | 141.18 (13) | H3B—C3—H3C | 109.5 |
O6—Sr1—O6i | 73.01 (15) | C6—O6—Sr1 | 124.7 (3) |
O1i—Sr1—O7i | 84.87 (12) | C6—N6—H6A | 120.0 |
O1—Sr1—O7i | 96.26 (12) | C6—N6—H6B | 120.0 |
O2—Sr1—O7i | 81.50 (13) | H6A—N6—H6B | 120.0 |
O2i—Sr1—O7i | 87.64 (14) | O6—C6—N6 | 122.7 (5) |
O6—Sr1—O7i | 131.51 (11) | O6—C6—C7 | 120.1 (5) |
O6i—Sr1—O7i | 61.46 (11) | N6—C6—C7 | 117.1 (4) |
O1i—Sr1—O7 | 96.26 (12) | C7—O7—Sr1 | 114.3 (3) |
O1—Sr1—O7 | 84.87 (12) | C7—O7—H7A | 112 (5) |
O2—Sr1—O7 | 87.64 (14) | Sr1—O7—H7A | 112 (4) |
O2i—Sr1—O7 | 81.50 (13) | O7—C7—C6 | 108.9 (4) |
O6—Sr1—O7 | 61.46 (11) | O7—C7—C8 | 108.6 (4) |
O6i—Sr1—O7 | 131.51 (11) | C6—C7—C8 | 109.9 (4) |
O7i—Sr1—O7 | 166.78 (15) | O7—C7—H7 | 109.8 |
C1—O1—Sr1 | 124.3 (3) | C6—C7—H7 | 109.8 |
C1—N1—H1A | 120.0 | C8—C7—H7 | 109.8 |
C1—N1—H1B | 120.0 | C7—C8—H8A | 109.5 |
H1A—N1—H1B | 120.0 | C7—C8—H8B | 109.5 |
O1—C1—N1 | 122.8 (5) | H8A—C8—H8B | 109.5 |
O1—C1—C2 | 121.5 (5) | C7—C8—H8C | 109.5 |
N1—C1—C2 | 115.6 (5) | H8A—C8—H8C | 109.5 |
C2—O2—Sr1 | 125.6 (3) | H8B—C8—H8C | 109.5 |
Symmetry code: (i) −x+1, −y+1, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7A···Br2 | 0.82 (4) | 2.43 (3) | 3.203 (4) | 158 (6) |
N1—H1A···Br2ii | 0.86 | 2.72 | 3.572 (5) | 171 |
N1—H1B···Br2iii | 0.86 | 2.73 | 3.568 (5) | 167 |
O2—H2A···O6iv | 0.82 (4) | 1.95 (4) | 2.759 (5) | 169 (6) |
N6—H6A···O7v | 0.86 | 2.24 | 3.071 (6) | 161 |
N6—H6B···Br2vi | 0.86 | 2.59 | 3.424 (5) | 164 |
Symmetry codes: (ii) x+1/2, −y+1/2, −z; (iii) x+1/2, −y+1/2, −z+1; (iv) −x+1, −y+1, z+1; (v) x, y, z−1; (vi) x−1/2, −y+1/2, −z. |
Experimental details
Crystal data | |
Chemical formula | [Sr(C3H7NO2)4]Br2 |
Mr | 603.82 |
Crystal system, space group | Orthorhombic, P21212 |
Temperature (K) | 293 |
a, b, c (Å) | 10.385 (2), 17.919 (2), 6.308 (1) |
V (Å3) | 1173.8 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 5.74 |
Crystal size (mm) | 0.25 × 0.16 × 0.12 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 |
Absorption correction | Empirical (using intensity measurements) [multi-scan (Blessing, 1995)] |
Tmin, Tmax | 0.27, 0.50 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7106, 3407, 2379 |
Rint | 0.067 |
(sin θ/λ)max (Å−1) | 0.704 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.111, 0.99 |
No. of reflections | 3407 |
No. of parameters | 130 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.68, −1.77 |
Absolute structure | Flack (1983), 1415 Friedel pairs |
Absolute structure parameter | −0.017 (15) |
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 1997), CAMERON (Watkin et al., 1996), WinGX (Version 1.63.02; Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7A···Br2 | 0.82 (4) | 2.43 (3) | 3.203 (4) | 158 (6) |
N1—H1A···Br2i | 0.86 | 2.72 | 3.572 (5) | 171 |
N1—H1B···Br2ii | 0.86 | 2.73 | 3.568 (5) | 167 |
O2—H2A···O6iii | 0.82 (4) | 1.95 (4) | 2.759 (5) | 169 (6) |
N6—H6A···O7iv | 0.86 | 2.24 | 3.071 (6) | 161 |
N6—H6B···Br2v | 0.86 | 2.59 | 3.424 (5) | 164 |
Symmetry codes: (i) x+1/2, −y+1/2, −z; (ii) x+1/2, −y+1/2, −z+1; (iii) −x+1, −y+1, z+1; (iv) x, y, z−1; (v) x−1/2, −y+1/2, −z. |
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Strontium provides some of the most important radioactive isotopes in the environment; e.g., 90Sr (Finlay et al., 2005), a by-product of the fission of uranium and plutonium in nuclear reaction or nuclear weapons, of which large amounts were produced during the Tchernobyl nuclear power plant disaster in 1986. It was later found in milk and vegetables. It is chemically similar to calcium and tends to deposit in bones and teeth. The half-life of 90Sr is 29.1 years emitting beta particules. Another isotope, 89Sr, is the active ingredient in Metastonρe.g, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer (Makhijani, 2003). Cold strontium ranelate (Prodelosρe.g) is the first antiosteoporotic treatment to simultaneously increase bone formation and decrease bone resorption (Reginster et al., 2007). In order to find new ligands of strontium as osteoporosous drugs, a new complex of strontium dibromide and R-lactamide has been studied. Compound (1) (Fig. 1) contains one monomeric octa-coordinated strontium complex cation, [Sr(C3H7NO2)4]2+, and two Br- anions. In the cation, the Sr atom lies on a twofold axis and is surrounded by four R-lactamide ligands coordinated in a bidentate fashion via amide atom O1 (or O6) and hydroxy atom O2 (or O7) and their symmetry equivalents. The Sr coordination in the cation can be approximately described as a very distorted square antiprism arrangement [with square bases: O1 O2 O6i O7i and O1i O2i O6 O7; i: 1 - x, 1 - y, z] with the Sr atom shifted away from these (symmetry realated) least-squares planes by 1.481 (2) Å. The Sr—O (amide) distances are similar within three estimated standard deviations [Sr—O1 (or O1i): 2.533 (3) and Sr—O6 (or O6i): 2.544 (4) Å]; among the Sr—O (hydroxy) distances Sr—O2 (or O2i): 2.535 (4) Å is equivalent to precedent values within three estimated standard deviations but very different from the two other distances Sr—O7 (or O7i): 2.703 (3) Å. All these values can be compared to those found in the poly[[tetaaquatris(monomethyl fumarato)distrontium(II)]monomethyl fumarate] in which the Sr atom is octa- coordinated by oxygen atoms which range from 2.499 (2) to 2.812 (2)Å (Stahl et al., 2006). Among the two possible coordination modes (N,O or O,O) in metal complexes with lactamide or its derivatives described in the literature, the title compound presents the O,O mode like those in the complexes with the [Zn(lactamide)3]2+ (Bekaert et al., 2005) or the [B(lactamide)2]+ (Bekaert et al., 2007) cations.
The packing is charaterized by a number of H-bonds (Table 2). In particular, Br- anions are linked to the cation by N–H···Br and O–H···Br hydrogen bonds, generating a three dimensional network.