Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107041352/sq3095sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107041352/sq3095Isup2.hkl |
CCDC reference: 665506
In an attempt to synthesize the borane, (III), from FcHgCl (0.88 g, 2.09 mmol) with Ph2BBr (0.51 g, 2.09 mmol) in hexane (45 ml) at 281 K, we obtained Ph2B—O—BPh2, (Ia), as a side-product. X-ray quality crystals of the title compound were grown from hexane at 281 K.
H atoms were located in a difference map, but were positioned geometrically and refined using a riding model, with fixed bond lengths and individual displacement parameters [C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C)].
Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003) and XP in SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: PLATON (Spek, 2003) and SHELXL97 (Sheldrick, 1997).
C24H20B2O | F(000) = 728 |
Mr = 346.02 | Dx = 1.174 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 7643 reflections |
a = 10.1489 (11) Å | θ = 3.8–25.5° |
b = 19.2851 (16) Å | µ = 0.07 mm−1 |
c = 10.1658 (11) Å | T = 173 K |
β = 100.286 (8)° | Block, orange-brown |
V = 1957.7 (3) Å3 | 0.19 × 0.17 × 0.17 mm |
Z = 4 |
Stoe IPDS II two-circle diffractometer | 2205 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.062 |
Graphite monochromator | θmax = 25.7°, θmin = 3.8° |
ω scans | h = −12→12 |
19779 measured reflections | k = −23→23 |
3682 independent reflections | l = −12→12 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.052 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.111 | H-atom parameters constrained |
S = 0.95 | w = 1/[σ2(Fo2) + (0.0425P)2] where P = (Fo2 + 2Fc2)/3 |
3682 reflections | (Δ/σ)max < 0.001 |
244 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.13 e Å−3 |
C24H20B2O | V = 1957.7 (3) Å3 |
Mr = 346.02 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.1489 (11) Å | µ = 0.07 mm−1 |
b = 19.2851 (16) Å | T = 173 K |
c = 10.1658 (11) Å | 0.19 × 0.17 × 0.17 mm |
β = 100.286 (8)° |
Stoe IPDS II two-circle diffractometer | 2205 reflections with I > 2σ(I) |
19779 measured reflections | Rint = 0.062 |
3682 independent reflections |
R[F2 > 2σ(F2)] = 0.052 | 0 restraints |
wR(F2) = 0.111 | H-atom parameters constrained |
S = 0.95 | Δρmax = 0.29 e Å−3 |
3682 reflections | Δρmin = −0.13 e Å−3 |
244 parameters |
Experimental. |
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 | ||
O1 | 0.67212 (15) | 0.38327 (8) | 0.51141 (13) | 0.0455 (4) | |
B1 | 0.7733 (2) | 0.34170 (14) | 0.5742 (2) | 0.0366 (6) | |
B2 | 0.6135 (3) | 0.41569 (13) | 0.3955 (2) | 0.0375 (6) | |
C1 | 0.80987 (19) | 0.35039 (11) | 0.73024 (19) | 0.0352 (5) | |
C2 | 0.8760 (2) | 0.29905 (12) | 0.81529 (19) | 0.0382 (5) | |
H2 | 0.8999 | 0.2566 | 0.7784 | 0.046* | |
C3 | 0.9073 (2) | 0.30951 (14) | 0.9529 (2) | 0.0488 (6) | |
H3 | 0.9527 | 0.2744 | 1.0090 | 0.059* | |
C4 | 0.8725 (3) | 0.37060 (16) | 1.0078 (2) | 0.0603 (8) | |
H4 | 0.8935 | 0.3774 | 1.1017 | 0.072* | |
C5 | 0.8068 (3) | 0.42218 (15) | 0.9264 (2) | 0.0614 (7) | |
H5 | 0.7833 | 0.4644 | 0.9645 | 0.074* | |
C6 | 0.7755 (2) | 0.41204 (13) | 0.7891 (2) | 0.0455 (6) | |
H6 | 0.7300 | 0.4475 | 0.7341 | 0.055* | |
C7 | 0.8415 (2) | 0.29119 (11) | 0.48572 (19) | 0.0349 (5) | |
C8 | 0.9738 (2) | 0.26868 (13) | 0.5240 (2) | 0.0441 (6) | |
H8 | 1.0217 | 0.2806 | 0.6100 | 0.053* | |
C9 | 1.0367 (2) | 0.22931 (14) | 0.4390 (2) | 0.0524 (6) | |
H9 | 1.1269 | 0.2151 | 0.4672 | 0.063* | |
C10 | 0.9689 (3) | 0.21056 (13) | 0.3137 (2) | 0.0525 (6) | |
H10 | 1.0120 | 0.1834 | 0.2560 | 0.063* | |
C11 | 0.8378 (3) | 0.23180 (13) | 0.2732 (2) | 0.0492 (6) | |
H11 | 0.7905 | 0.2192 | 0.1873 | 0.059* | |
C12 | 0.7758 (2) | 0.27113 (12) | 0.3574 (2) | 0.0418 (5) | |
H12 | 0.6856 | 0.2852 | 0.3279 | 0.050* | |
C13 | 0.7002 (2) | 0.46453 (11) | 0.32223 (19) | 0.0369 (5) | |
C14 | 0.8409 (2) | 0.46569 (12) | 0.3556 (2) | 0.0457 (6) | |
H14 | 0.8846 | 0.4342 | 0.4209 | 0.055* | |
C15 | 0.9172 (3) | 0.51121 (13) | 0.2963 (2) | 0.0527 (6) | |
H15 | 1.0121 | 0.5104 | 0.3206 | 0.063* | |
C16 | 0.8562 (3) | 0.55795 (13) | 0.2015 (2) | 0.0511 (6) | |
H16 | 0.9088 | 0.5894 | 0.1609 | 0.061* | |
C17 | 0.7179 (3) | 0.55867 (13) | 0.1661 (2) | 0.0474 (6) | |
H17 | 0.6755 | 0.5908 | 0.1013 | 0.057* | |
C18 | 0.6414 (2) | 0.51262 (12) | 0.2251 (2) | 0.0408 (5) | |
H18 | 0.5467 | 0.5135 | 0.1992 | 0.049* | |
C19 | 0.4588 (2) | 0.40369 (11) | 0.35428 (19) | 0.0349 (5) | |
C20 | 0.3929 (2) | 0.39576 (12) | 0.2208 (2) | 0.0429 (5) | |
H20 | 0.4421 | 0.4002 | 0.1500 | 0.051* | |
C21 | 0.2567 (2) | 0.38154 (13) | 0.1919 (2) | 0.0520 (6) | |
H21 | 0.2139 | 0.3752 | 0.1017 | 0.062* | |
C22 | 0.1830 (2) | 0.37657 (14) | 0.2930 (3) | 0.0558 (7) | |
H22 | 0.0897 | 0.3671 | 0.2721 | 0.067* | |
C23 | 0.2444 (2) | 0.38524 (13) | 0.4248 (2) | 0.0511 (6) | |
H23 | 0.1934 | 0.3827 | 0.4945 | 0.061* | |
C24 | 0.3807 (2) | 0.39763 (12) | 0.4542 (2) | 0.0421 (5) | |
H24 | 0.4227 | 0.4022 | 0.5451 | 0.050* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0381 (9) | 0.0575 (10) | 0.0387 (8) | 0.0098 (7) | 0.0004 (6) | 0.0082 (7) |
B1 | 0.0250 (12) | 0.0440 (15) | 0.0394 (12) | −0.0067 (10) | 0.0018 (10) | 0.0094 (11) |
B2 | 0.0416 (14) | 0.0399 (15) | 0.0296 (11) | 0.0100 (11) | 0.0025 (10) | −0.0023 (10) |
C1 | 0.0237 (10) | 0.0444 (13) | 0.0366 (10) | −0.0039 (9) | 0.0025 (8) | 0.0029 (9) |
C2 | 0.0299 (11) | 0.0460 (13) | 0.0374 (11) | −0.0040 (9) | 0.0025 (9) | 0.0063 (10) |
C3 | 0.0382 (13) | 0.0711 (18) | 0.0353 (11) | −0.0059 (12) | 0.0017 (10) | 0.0097 (12) |
C4 | 0.0499 (15) | 0.095 (2) | 0.0340 (12) | −0.0106 (15) | 0.0029 (11) | −0.0131 (13) |
C5 | 0.0521 (16) | 0.0728 (19) | 0.0574 (15) | −0.0035 (14) | 0.0047 (13) | −0.0233 (14) |
C6 | 0.0361 (12) | 0.0481 (14) | 0.0510 (13) | −0.0017 (10) | 0.0040 (10) | −0.0049 (11) |
C7 | 0.0284 (11) | 0.0397 (12) | 0.0357 (10) | −0.0054 (9) | 0.0037 (8) | 0.0082 (9) |
C8 | 0.0310 (12) | 0.0593 (15) | 0.0413 (11) | −0.0005 (10) | 0.0044 (10) | 0.0048 (10) |
C9 | 0.0307 (12) | 0.0641 (17) | 0.0644 (15) | 0.0047 (11) | 0.0141 (11) | 0.0055 (13) |
C10 | 0.0522 (15) | 0.0527 (15) | 0.0562 (14) | −0.0023 (12) | 0.0196 (12) | −0.0059 (12) |
C11 | 0.0511 (15) | 0.0507 (14) | 0.0446 (12) | −0.0047 (12) | 0.0054 (11) | −0.0057 (11) |
C12 | 0.0376 (12) | 0.0424 (13) | 0.0431 (12) | 0.0001 (10) | 0.0007 (10) | 0.0009 (10) |
C13 | 0.0352 (12) | 0.0398 (12) | 0.0349 (10) | 0.0013 (9) | 0.0039 (9) | −0.0045 (9) |
C14 | 0.0384 (13) | 0.0448 (13) | 0.0517 (13) | −0.0008 (11) | 0.0015 (10) | 0.0020 (11) |
C15 | 0.0404 (14) | 0.0507 (15) | 0.0656 (15) | −0.0064 (12) | 0.0056 (11) | −0.0017 (12) |
C16 | 0.0537 (16) | 0.0478 (14) | 0.0526 (13) | −0.0120 (12) | 0.0116 (12) | −0.0027 (12) |
C17 | 0.0568 (15) | 0.0458 (14) | 0.0394 (12) | 0.0020 (11) | 0.0082 (11) | 0.0001 (10) |
C18 | 0.0400 (13) | 0.0454 (13) | 0.0368 (11) | 0.0011 (10) | 0.0063 (9) | −0.0032 (10) |
C19 | 0.0332 (11) | 0.0369 (12) | 0.0330 (10) | 0.0067 (9) | 0.0013 (8) | 0.0042 (9) |
C20 | 0.0427 (13) | 0.0488 (14) | 0.0356 (11) | 0.0011 (11) | 0.0031 (9) | 0.0074 (10) |
C21 | 0.0435 (14) | 0.0618 (17) | 0.0444 (12) | −0.0044 (12) | −0.0091 (11) | 0.0132 (11) |
C22 | 0.0307 (12) | 0.0648 (17) | 0.0689 (16) | −0.0013 (11) | 0.0004 (12) | 0.0189 (13) |
C23 | 0.0404 (14) | 0.0626 (17) | 0.0529 (13) | 0.0046 (12) | 0.0158 (11) | 0.0094 (12) |
C24 | 0.0395 (13) | 0.0500 (14) | 0.0373 (11) | 0.0075 (10) | 0.0086 (9) | 0.0054 (10) |
O1—B1 | 1.367 (3) | C11—C12 | 1.377 (3) |
O1—B2 | 1.372 (3) | C11—H11 | 0.9500 |
B1—C7 | 1.568 (3) | C12—H12 | 0.9500 |
B1—C1 | 1.573 (3) | C13—C18 | 1.408 (3) |
B2—C13 | 1.565 (3) | C13—C14 | 1.408 (3) |
B2—C19 | 1.568 (3) | C14—C15 | 1.379 (3) |
C1—C6 | 1.403 (3) | C14—H14 | 0.9500 |
C1—C2 | 1.404 (3) | C15—C16 | 1.382 (3) |
C2—C3 | 1.393 (3) | C15—H15 | 0.9500 |
C2—H2 | 0.9500 | C16—C17 | 1.385 (4) |
C3—C4 | 1.376 (4) | C16—H16 | 0.9500 |
C3—H3 | 0.9500 | C17—C18 | 1.385 (3) |
C4—C5 | 1.386 (4) | C17—H17 | 0.9500 |
C4—H4 | 0.9500 | C18—H18 | 0.9500 |
C5—C6 | 1.389 (3) | C19—C24 | 1.401 (3) |
C5—H5 | 0.9500 | C19—C20 | 1.410 (3) |
C6—H6 | 0.9500 | C20—C21 | 1.389 (3) |
C7—C8 | 1.399 (3) | C20—H20 | 0.9500 |
C7—C12 | 1.409 (3) | C21—C22 | 1.377 (3) |
C8—C9 | 1.388 (3) | C21—H21 | 0.9500 |
C8—H8 | 0.9500 | C22—C23 | 1.384 (3) |
C9—C10 | 1.384 (3) | C22—H22 | 0.9500 |
C9—H9 | 0.9500 | C23—C24 | 1.382 (3) |
C10—C11 | 1.382 (4) | C23—H23 | 0.9500 |
C10—H10 | 0.9500 | C24—H24 | 0.9500 |
B1—O1—B2 | 147.34 (19) | C11—C12—C7 | 122.2 (2) |
O1—B1—C7 | 117.92 (18) | C11—C12—H12 | 118.9 |
O1—B1—C1 | 115.5 (2) | C7—C12—H12 | 118.9 |
C7—B1—C1 | 126.57 (19) | C18—C13—C14 | 116.3 (2) |
O1—B2—C13 | 119.3 (2) | C18—C13—B2 | 121.79 (19) |
O1—B2—C19 | 114.9 (2) | C14—C13—B2 | 121.81 (19) |
C13—B2—C19 | 125.64 (18) | C15—C14—C13 | 122.0 (2) |
C6—C1—C2 | 117.57 (18) | C15—C14—H14 | 119.0 |
C6—C1—B1 | 119.27 (19) | C13—C14—H14 | 119.0 |
C2—C1—B1 | 123.2 (2) | C14—C15—C16 | 120.2 (2) |
C3—C2—C1 | 120.9 (2) | C14—C15—H15 | 119.9 |
C3—C2—H2 | 119.5 | C16—C15—H15 | 119.9 |
C1—C2—H2 | 119.5 | C15—C16—C17 | 119.7 (2) |
C4—C3—C2 | 120.2 (2) | C15—C16—H16 | 120.2 |
C4—C3—H3 | 119.9 | C17—C16—H16 | 120.2 |
C2—C3—H3 | 119.9 | C18—C17—C16 | 120.1 (2) |
C3—C4—C5 | 120.2 (2) | C18—C17—H17 | 119.9 |
C3—C4—H4 | 119.9 | C16—C17—H17 | 119.9 |
C5—C4—H4 | 119.9 | C17—C18—C13 | 121.7 (2) |
C4—C5—C6 | 119.9 (3) | C17—C18—H18 | 119.1 |
C4—C5—H5 | 120.1 | C13—C18—H18 | 119.1 |
C6—C5—H5 | 120.1 | C24—C19—C20 | 117.2 (2) |
C5—C6—C1 | 121.2 (2) | C24—C19—B2 | 119.23 (17) |
C5—C6—H6 | 119.4 | C20—C19—B2 | 123.6 (2) |
C1—C6—H6 | 119.4 | C21—C20—C19 | 120.5 (2) |
C8—C7—C12 | 116.4 (2) | C21—C20—H20 | 119.7 |
C8—C7—B1 | 122.24 (18) | C19—C20—H20 | 119.7 |
C12—C7—B1 | 121.13 (18) | C22—C21—C20 | 120.6 (2) |
C9—C8—C7 | 121.5 (2) | C22—C21—H21 | 119.7 |
C9—C8—H8 | 119.3 | C20—C21—H21 | 119.7 |
C7—C8—H8 | 119.3 | C21—C22—C23 | 120.2 (2) |
C10—C9—C8 | 120.5 (2) | C21—C22—H22 | 119.9 |
C10—C9—H9 | 119.7 | C23—C22—H22 | 119.9 |
C8—C9—H9 | 119.7 | C24—C23—C22 | 119.3 (2) |
C11—C10—C9 | 119.3 (2) | C24—C23—H23 | 120.3 |
C11—C10—H10 | 120.3 | C22—C23—H23 | 120.3 |
C9—C10—H10 | 120.3 | C23—C24—C19 | 122.14 (19) |
C12—C11—C10 | 120.1 (2) | C23—C24—H24 | 118.9 |
C12—C11—H11 | 120.0 | C19—C24—H24 | 118.9 |
C10—C11—H11 | 120.0 | ||
B2—O1—B1—C7 | −24.0 (5) | C8—C7—C12—C11 | −0.3 (3) |
B2—O1—B1—C1 | 155.6 (3) | B1—C7—C12—C11 | 174.2 (2) |
B1—O1—B2—C13 | −54.2 (4) | O1—B2—C13—C18 | −163.16 (19) |
B1—O1—B2—C19 | 130.2 (3) | C19—B2—C13—C18 | 12.0 (3) |
O1—B1—C1—C6 | −21.7 (3) | O1—B2—C13—C14 | 13.0 (3) |
C7—B1—C1—C6 | 157.8 (2) | C19—B2—C13—C14 | −171.9 (2) |
O1—B1—C1—C2 | 158.3 (2) | C18—C13—C14—C15 | −0.2 (3) |
C7—B1—C1—C2 | −22.2 (3) | B2—C13—C14—C15 | −176.5 (2) |
C6—C1—C2—C3 | −0.6 (3) | C13—C14—C15—C16 | 0.4 (4) |
B1—C1—C2—C3 | 179.4 (2) | C14—C15—C16—C17 | −0.2 (4) |
C1—C2—C3—C4 | 0.5 (3) | C15—C16—C17—C18 | −0.2 (4) |
C2—C3—C4—C5 | −0.3 (4) | C16—C17—C18—C13 | 0.5 (3) |
C3—C4—C5—C6 | 0.3 (4) | C14—C13—C18—C17 | −0.3 (3) |
C4—C5—C6—C1 | −0.4 (4) | B2—C13—C18—C17 | 176.1 (2) |
C2—C1—C6—C5 | 0.6 (3) | O1—B2—C19—C24 | 34.5 (3) |
B1—C1—C6—C5 | −179.5 (2) | C13—B2—C19—C24 | −140.8 (2) |
O1—B1—C7—C8 | 152.9 (2) | O1—B2—C19—C20 | −142.9 (2) |
C1—B1—C7—C8 | −26.6 (3) | C13—B2—C19—C20 | 41.8 (3) |
O1—B1—C7—C12 | −21.3 (3) | C24—C19—C20—C21 | −0.9 (3) |
C1—B1—C7—C12 | 159.2 (2) | B2—C19—C20—C21 | 176.5 (2) |
C12—C7—C8—C9 | 0.6 (3) | C19—C20—C21—C22 | 1.5 (4) |
B1—C7—C8—C9 | −173.8 (2) | C20—C21—C22—C23 | −0.4 (4) |
C7—C8—C9—C10 | −0.7 (4) | C21—C22—C23—C24 | −1.2 (4) |
C8—C9—C10—C11 | 0.4 (4) | C22—C23—C24—C19 | 1.8 (4) |
C9—C10—C11—C12 | −0.1 (4) | C20—C19—C24—C23 | −0.8 (3) |
C10—C11—C12—C7 | 0.1 (4) | B2—C19—C24—C23 | −178.3 (2) |
Experimental details
Crystal data | |
Chemical formula | C24H20B2O |
Mr | 346.02 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 173 |
a, b, c (Å) | 10.1489 (11), 19.2851 (16), 10.1658 (11) |
β (°) | 100.286 (8) |
V (Å3) | 1957.7 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.19 × 0.17 × 0.17 |
Data collection | |
Diffractometer | Stoe IPDS II two-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 19779, 3682, 2205 |
Rint | 0.062 |
(sin θ/λ)max (Å−1) | 0.609 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.052, 0.111, 0.95 |
No. of reflections | 3682 |
No. of parameters | 244 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.13 |
Computer programs: X-AREA (Stoe & Cie, 2001), SHELXS97 (Sheldrick, 1990), PLATON (Spek, 2003) and XP in SHELXTL-Plus (Sheldrick, 1991), PLATON (Spek, 2003) and SHELXL97 (Sheldrick, 1997).
Angle | (Ia) | (Ib) |
O1-B1-C1-C2 | 158.3 (2) | -140.9 |
O1-B1-C7-C8 | 152.9 (2) | -167.5 |
B2-O1-B1-C1 | 155.6 (3) | 156.9 |
B2-O1-B1-C7 | -24.0 (5) | -26.4 |
B1-O1-B2-C13 | -54.2 (4) | -59.1 |
B1-O1-B2-C19 | 130.2 (3) | 126.3 |
O1-B2-C19-C20 | -142.9 (2) | -135.3 |
O1-B2-C13-C18 | -163.2 (2) | -167.1 |
Compound | B—O—B | B—O | B—O |
BUBXEB | 165.46 | 1.359 | 1.370 |
BZBPER | 159.39 | 1.340 | 1.347 |
DTBOPE | 152.63 | 1.358 | 1.358 |
UCITEF | 152.69 (2) | 1.345 (4) | 1.349 (4) |
(Ia) | 147.34 (19) | 1.367 (3) | 1.372 (3) |
Recently, we have synthesized the anionic [1,1]diborataferrocenophane, (II), which represents a highly efficient Li+ scavenger (see scheme) (Scheibitz et al., 2003), and anionic ferrocene derivatives such as the ferrocenyl borate, (IV) (Kaufmann et al., 2007). In an attempt to synthesize the borane, (III), from FcHgCl (Fc = C5H4FeC5H5) and Ph2BBr, we have obtained the title compound, tetraphenyldiboroxane, Ph2B—O—BPh2, (Ia), as a side-product. The ferrocene derivative, (III), represents a versatile starting material for the synthesis of a broad range of ferrocenyl-substituted polyborates.
Both B atoms in (Ia) are in trigonal planar environments (Fig. 1). The sums of the bond angles are 360.0 (2) and 359.8 (2)° for atoms B1 and B2, respectively. Another monoclinic polymorph of the title compound, (Ib), has been described at 190 K in space group P21/c, with cell parameters a = 12.378 (5), b = 8.019 (2) and c = 19.180 (7) Å, β = 100.89 (3)°, and V = 1869.51 Å3 (Lange et al., 2002). The only similarity between the cell parameters of the two polymorphs is that the c axis of (Ia) and the b axis of (Ib) differ by just 0.1 Å. Since the cell parameters are otherwise completely different, the setting in P21/n has been selected for (Ia). A least-squares fit of the two polymorphs shows that the orientations of the phenyl rings attached to atom B2 are almost identical in (Ia) and (Ib), while the orientations of the phenyl rings attached to atom B1 differ significantly (Fig. 2). This difference can also be illustrated by a comparison of the corresponding torsion angles (Table 1); only the torsion angles about the B1—C1 and B1—C7 bonds differ significantly.
An analysis of short intramolecular distances for both polymorphs reveals two somewhat shorter X···H distances in (Ib), which might be the reason for the different orientations of the phenyl rings [B2···H10 = 2.63 Å in (Ib) versus 2.74 Å in (Ia), and C2···H6 = 2.71 Å in (Ib) versus 2.79 Å in (Ia); all C—H distances are 0.93 Å in both polymorphs]. A molecular mechanics calculation with the molecular modelling program MOMO (Beck et al., 1991) shows that the conformation of (Ia) is more stable than that of (Ib), by 4.2 kcal mol−1 [1 kcal mol−1 = 4.184 kJ mol−1].
The packing motifs of the two polymorphs are quite different, presumably due to the different orientations of two of the four aromatic rings. The orientations of the packing diagrams (Figs. 3 and 4) have been chosen so that one molecule (shown with dashed bonds) has approximately the same orientation in both figures. Comparison of the diagrams shows that the orientation of the remaining molecules differs markedly.
An analysis of short intermolecular distances in the crystal packing of both polymorphs shows only two notable short distances in (Ib) [C14···H8i = 2.96 Å and C21···H2ii = 2.93 Å; symmetry codes: (i) x, y − 1, z; (ii) x + 1, y, z], whereas there are five intermolecular C···H distances of less than 3 Å in (Ia): C6···H15i = 2.99 Å, C3···H9ii = 2.91 Å, C10···H17iii = 2.95 Å, C17···H5iv = 2.90 Å and C20···H2v = 2.99 Å [symmetry codes: (i) 2 − x, 1 − y, 1 − z; (ii) −1/2 + x, 1/2 − y, 1/2 + z; (iii) 3/2 − x, −1/2 + y, 1/2 − z; (iv) x, −1 + y, −1 + z; (v) −1/2 + x, 1/2 − y, −1/2 + z]. In addition, there is one very short intermolecular H···H distance in (Ia) [H4···H22vi = 2.40 Å; symmetry code: (vi) 1 + x, y, 1 + z], for which there is no equivalent in (Ib). The difference in all these intermolecular contacts shows that a single molecule is in a different environment in both structures.
A search of the Cambridge Structural Database (Version 5.28, November 2006, updated May 2007; Allen, 2002) for the fragment (Car)2B—O—B(Car)2 shows just four entries, namely BUBXEB (Cardin et al., 1983), BZBPER (Cynkier & Furmanova, 1980), DTBOPE (Aurivillius, 1974) and UCITEF, which is (Ib) (Lange et al., 2002). It is worth noting that in all of these structures the B—O—B angle is wider than in (Ia) and the B—O bond lengths are shorter (Table 2), although the measurement temperatures of 173 K for (Ia) and 190 K for (Ib) are almost equal.