The title compound, C20H32B2N4, is monoclinic at ambient temperature but triclinic (pseudo-monoclinic) below 150 K. The structures of the two phases, determined at 200 and 120 K, respectively, are very similar, the molecular symmetry being crystallographic C2 and approximate (local) C2, respectively. There is significant π conjugation within each N—B—N moiety, but none between them or between the N—B—N and arene moieties.
Supporting information
CCDC references: 851743; 851744
Compound (I) was prepared by reaction of Me2NB(Cl)B(Cl)NMe2 with
LiHNC6H3Me2-2,6, as described by Patton et al. (2001).
[Crystals
obtained directly, or by solvent evaporation from which solvent?]
All H atoms were located in difference maps. Methyl groups were refined as
rigid bodies rotating around C—C or N—C bonds, with C—H = 0.98 Å. The
C10H3 group in α-(I) was treated as ideally disordered. The arene H atoms
were treated as riding on their C atoms, with C—H = 0.95 Å. The amino H
atoms were refined with N—H distances restrained to 0.88 (2) Å. The
Uiso values of the methyl H atoms were constrained to 1.5 times, and
those of other H atoms to 1.2 times, the Ueq of the respective C or N
atom.
Data collection: SMART (Bruker, 1998) for aI; SMART (Bruker, 2001) for bI. For both compounds, cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Version 6.12; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.12; Sheldrick, 2008); molecular graphics: OLEX2 (Version 1.1-β+++; Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Version 1.1-β+++; Dolomanov et al., 2009).
(aI) 1,2-bis(dimethylamino)-1,2-bis(2,6-dimethylanilino)diborane
top
Crystal data top
C20H32B2N4 | F(000) = 380 |
Mr = 350.12 | Dx = 1.100 Mg m−3 |
Monoclinic, P2/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yac | Cell parameters from 4810 reflections |
a = 10.4957 (11) Å | θ = 2.6–28.9° |
b = 9.6327 (10) Å | µ = 0.07 mm−1 |
c = 10.5554 (11) Å | T = 200 K |
β = 98.06 (2)° | Plate, colourless |
V = 1056.63 (19) Å3 | 0.53 × 0.35 × 0.05 mm |
Z = 2 | |
Data collection top
Siemens SMART 1000 CCD area-detector diffractometer | 2436 independent reflections |
Radiation source: fine-focus sealed tube | 1779 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.028 |
Detector resolution: 8 pixels mm-1 | θmax = 27.5°, θmin = 2.1° |
ω scans | h = −13→13 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | k = −12→12 |
Tmin = 0.924, Tmax = 1.000 | l = −13→13 |
10983 measured reflections | |
Refinement top
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)] = 0.043 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.128 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0582P)2 + 0.1935P] where P = (Fo2 + 2Fc2)/3 |
2436 reflections | (Δ/σ)max < 0.001 |
124 parameters | Δρmax = 0.28 e Å−3 |
1 restraint | Δρmin = −0.16 e Å−3 |
Crystal data top
C20H32B2N4 | V = 1056.63 (19) Å3 |
Mr = 350.12 | Z = 2 |
Monoclinic, P2/n | Mo Kα radiation |
a = 10.4957 (11) Å | µ = 0.07 mm−1 |
b = 9.6327 (10) Å | T = 200 K |
c = 10.5554 (11) Å | 0.53 × 0.35 × 0.05 mm |
β = 98.06 (2)° | |
Data collection top
Siemens SMART 1000 CCD area-detector diffractometer | 2436 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | 1779 reflections with I > 2σ(I) |
Tmin = 0.924, Tmax = 1.000 | Rint = 0.028 |
10983 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.043 | 1 restraint |
wR(F2) = 0.128 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.28 e Å−3 |
2436 reflections | Δρmin = −0.16 e Å−3 |
124 parameters | |
Special details top
Experimental. The data collection nominally covered full sphere of reciprocal space, by a
combination of 4 runs of narrow-frame ω-scans (scan width 0.3° ω, 20 s
exposure), every run at a different ϕ angle. Crystal to detector distance
4.41 cm. |
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. Methyl groups
were refined as rigid bodies rotating around C—C or N—C bonds, except
C(10)H3 which was treated as ideally disordered between 2 orientations
(riding model). The amino hydrogen - Only coordinates of H atoms refined with
the N—H distance restrained to 0.88 (2), arene H atoms - riding model. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
N1 | 0.11688 (10) | 0.21137 (13) | 0.12955 (11) | 0.0417 (3) | |
H1N | 0.0336 (12) | 0.2042 (16) | 0.1103 (14) | 0.050* | |
N2 | 0.08526 (12) | 0.42128 (13) | 0.24982 (12) | 0.0509 (3) | |
C1 | 0.17641 (11) | 0.09284 (14) | 0.08258 (11) | 0.0351 (3) | |
C2 | 0.13404 (11) | −0.03951 (14) | 0.11391 (11) | 0.0363 (3) | |
C3 | 0.18564 (12) | −0.15600 (15) | 0.06326 (12) | 0.0427 (3) | |
H3 | 0.1572 | −0.2430 | 0.0846 | 0.051* | |
C4 | 0.27814 (13) | −0.14390 (18) | −0.01784 (13) | 0.0486 (4) | |
H4 | 0.3133 | −0.2279 | −0.0517 | 0.058* | |
C5 | 0.31867 (13) | −0.01409 (18) | −0.04859 (12) | 0.0486 (4) | |
H5 | 0.3823 | −0.0122 | −0.1044 | 0.058* | |
C6 | 0.26890 (12) | 0.10617 (16) | −0.00077 (12) | 0.0424 (3) | |
C7 | 0.03494 (12) | −0.05473 (16) | 0.20282 (12) | 0.0433 (3) | |
H7A | 0.0167 | −0.1534 | 0.2140 | 0.065* | |
H7B | −0.0443 | −0.0070 | 0.1664 | 0.065* | |
H7C | 0.0677 | −0.0137 | 0.2860 | 0.065* | |
C8 | 0.31144 (16) | 0.24532 (19) | −0.04330 (15) | 0.0611 (4) | |
H8A | 0.3816 | 0.2805 | 0.0196 | 0.092* | |
H8B | 0.2389 | 0.3103 | −0.0506 | 0.092* | |
H8C | 0.3416 | 0.2360 | −0.1266 | 0.092* | |
C9 | 0.12520 (17) | 0.53273 (16) | 0.33939 (17) | 0.0592 (4) | |
H9A | 0.2166 | 0.5218 | 0.3727 | 0.089* | |
H9B | 0.0743 | 0.5296 | 0.4104 | 0.089* | |
H9C | 0.1118 | 0.6222 | 0.2953 | 0.089* | |
C10 | −0.05069 (17) | 0.4308 (2) | 0.1985 (2) | 0.0774 (6) | |
H10A | −0.0921 | 0.3408 | 0.2075 | 0.116* | 0.50 |
H10B | −0.0597 | 0.4563 | 0.1078 | 0.116* | 0.50 |
H10C | −0.0918 | 0.5016 | 0.2457 | 0.116* | 0.50 |
H10D | −0.0655 | 0.5254 | 0.1656 | 0.116* | 0.50 |
H10E | −0.0806 | 0.3739 | 0.1232 | 0.116* | 0.50 |
H10F | −0.0941 | 0.4219 | 0.2744 | 0.116* | 0.50 |
B1 | 0.16980 (14) | 0.31610 (16) | 0.21743 (14) | 0.0391 (3) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0265 (5) | 0.0522 (7) | 0.0449 (6) | 0.0033 (5) | −0.0007 (4) | −0.0041 (5) |
N2 | 0.0400 (6) | 0.0517 (7) | 0.0587 (7) | 0.0077 (5) | −0.0009 (5) | −0.0089 (6) |
C1 | 0.0261 (6) | 0.0500 (8) | 0.0276 (5) | 0.0015 (5) | −0.0023 (4) | −0.0013 (5) |
C2 | 0.0272 (6) | 0.0532 (8) | 0.0270 (5) | 0.0011 (5) | −0.0012 (4) | 0.0001 (5) |
C3 | 0.0375 (7) | 0.0495 (8) | 0.0393 (7) | 0.0027 (6) | −0.0010 (5) | −0.0012 (6) |
C4 | 0.0400 (7) | 0.0637 (10) | 0.0414 (7) | 0.0103 (7) | 0.0035 (6) | −0.0105 (7) |
C5 | 0.0316 (7) | 0.0804 (11) | 0.0347 (6) | 0.0035 (7) | 0.0082 (5) | −0.0050 (7) |
C6 | 0.0316 (6) | 0.0630 (9) | 0.0315 (6) | −0.0036 (6) | 0.0006 (5) | 0.0012 (6) |
C7 | 0.0341 (7) | 0.0608 (9) | 0.0347 (6) | −0.0016 (6) | 0.0040 (5) | 0.0033 (6) |
C8 | 0.0581 (9) | 0.0747 (12) | 0.0530 (9) | −0.0121 (8) | 0.0163 (7) | 0.0093 (8) |
C9 | 0.0604 (10) | 0.0481 (9) | 0.0690 (10) | 0.0055 (7) | 0.0086 (8) | −0.0092 (8) |
C10 | 0.0462 (9) | 0.0832 (13) | 0.0978 (14) | 0.0227 (9) | −0.0075 (9) | −0.0223 (11) |
B1 | 0.0352 (7) | 0.0439 (8) | 0.0379 (7) | 0.0009 (6) | 0.0040 (6) | 0.0034 (6) |
Geometric parameters (Å, º) top
N1—C1 | 1.4237 (16) | C7—H7A | 0.9800 |
N1—B1 | 1.4290 (19) | C7—H7B | 0.9801 |
N1—H1N | 0.871 (12) | C7—H7C | 0.9800 |
N2—B1 | 1.4197 (19) | C8—H8A | 0.9803 |
N2—C9 | 1.453 (2) | C8—H8B | 0.9800 |
N2—C10 | 1.456 (2) | C8—H8C | 0.9798 |
C1—C6 | 1.4043 (17) | C9—H9A | 0.9800 |
C1—C2 | 1.4049 (18) | C9—H9B | 0.9800 |
C2—C3 | 1.3855 (18) | C9—H9C | 0.9801 |
C2—C7 | 1.5026 (17) | C10—H10A | 0.9800 |
C3—C4 | 1.3864 (19) | C10—H10B | 0.9800 |
C3—H3 | 0.9283 | C10—H10C | 0.9800 |
C4—C5 | 1.374 (2) | C10—H10D | 0.9800 |
C4—H4 | 0.9777 | C10—H10E | 0.9800 |
C5—C6 | 1.394 (2) | C10—H10F | 0.9800 |
C5—H5 | 0.9512 | B1—B1i | 1.727 (3) |
C6—C8 | 1.501 (2) | | |
| | | |
C1—N1—B1 | 129.99 (11) | C6—C8—H8C | 109.5 |
C1—N1—H1N | 109.3 (10) | H8A—C8—H8C | 109.5 |
B1—N1—H1N | 119.5 (10) | H8B—C8—H8C | 109.5 |
B1—N2—C9 | 123.43 (12) | N2—C9—H9A | 109.5 |
B1—N2—C10 | 124.61 (13) | N2—C9—H9B | 109.6 |
C9—N2—C10 | 111.96 (13) | H9A—C9—H9B | 109.5 |
C6—C1—C2 | 119.99 (12) | N2—C9—H9C | 109.3 |
C6—C1—N1 | 121.37 (12) | H9A—C9—H9C | 109.4 |
C2—C1—N1 | 118.48 (11) | H9B—C9—H9C | 109.5 |
C3—C2—C1 | 119.36 (11) | N2—C10—H10A | 109.4 |
C3—C2—C7 | 120.28 (13) | N2—C10—H10B | 109.6 |
C1—C2—C7 | 120.35 (12) | H10A—C10—H10B | 109.5 |
C2—C3—C4 | 121.04 (14) | N2—C10—H10C | 109.4 |
C2—C3—H3 | 118.8 | H10A—C10—H10C | 109.5 |
C4—C3—H3 | 120.2 | H10B—C10—H10C | 109.5 |
C5—C4—C3 | 119.28 (13) | N2—C10—H10D | 106.8 |
C5—C4—H4 | 121.4 | H10A—C10—H10D | 143.7 |
C3—C4—H4 | 119.3 | H10B—C10—H10D | 55.4 |
C4—C5—C6 | 121.76 (12) | H10C—C10—H10D | 58.2 |
C4—C5—H5 | 115.6 | N2—C10—H10E | 116.9 |
C6—C5—H5 | 122.7 | H10A—C10—H10E | 59.2 |
C5—C6—C1 | 118.55 (13) | H10B—C10—H10E | 51.1 |
C5—C6—C8 | 119.43 (12) | H10C—C10—H10E | 133.5 |
C1—C6—C8 | 121.98 (13) | H10D—C10—H10E | 102.5 |
C2—C7—H7A | 109.5 | N2—C10—H10F | 103.5 |
C2—C7—H7B | 109.4 | H10A—C10—H10F | 65.1 |
H7A—C7—H7B | 109.5 | H10B—C10—H10F | 146.0 |
C2—C7—H7C | 109.5 | H10C—C10—H10F | 50.0 |
H7A—C7—H7C | 109.5 | H10D—C10—H10F | 107.6 |
H7B—C7—H7C | 109.5 | H10E—C10—H10F | 118.8 |
C6—C8—H8A | 109.5 | N2—B1—N1 | 117.45 (12) |
C6—C8—H8B | 109.5 | N2—B1—B1i | 120.76 (10) |
H8A—C8—H8B | 109.5 | N1—B1—B1i | 121.80 (10) |
| | | |
C6—C1—N1—B1 | −69.21 (18) | N1—B1—B1i—N1i | −67.7 (3) |
C1—N1—B1—B1i | 1.8 (2) | N2—B1—B1i—N2ii | 173.69 (16) |
Symmetry codes: (i) −x+1/2, y, −z+1/2; (ii) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···C3ii | 0.87 (1) | 2.77 (1) | 3.5631 (18) | 152 (1) |
Symmetry code: (ii) −x, −y, −z. |
(bI) 1,2-bis(dimethylamino)-1,2-bis(2,6-dimethylanilino)diborane
top
Crystal data top
C20H32B2N4 | Z = 2 |
Mr = 350.12 | F(000) = 380 |
Triclinic, P1 | Dx = 1.113 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 10.5043 (13) Å | Cell parameters from 3491 reflections |
b = 9.6449 (11) Å | θ = 2.6–27.4° |
c = 10.4428 (14) Å | µ = 0.07 mm−1 |
α = 92.69 (3)° | T = 120 K |
β = 98.29 (3)° | Plate, colourless |
γ = 87.45 (3)° | 0.52 × 0.21 × 0.02 mm |
V = 1045.0 (2) Å3 | |
Data collection top
Bruker SMART 6000 CCD area-detector diffractometer | 3693 independent reflections |
Radiation source: fine-focus sealed tube | 2774 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.027 |
Detector resolution: 5.6 pixels mm-1 | θmax = 25.0°, θmin = 2.0° |
ω scans | h = −12→12 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | k = −11→11 |
Tmin = 0.715, Tmax = 0.862 | l = −12→12 |
9870 measured reflections | |
Refinement top
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)] = 0.053 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.150 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0806P)2 + 0.3393P] where P = (Fo2 + 2Fc2)/3 |
3693 reflections | (Δ/σ)max < 0.001 |
249 parameters | Δρmax = 0.35 e Å−3 |
2 restraints | Δρmin = −0.24 e Å−3 |
Crystal data top
C20H32B2N4 | γ = 87.45 (3)° |
Mr = 350.12 | V = 1045.0 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 10.5043 (13) Å | Mo Kα radiation |
b = 9.6449 (11) Å | µ = 0.07 mm−1 |
c = 10.4428 (14) Å | T = 120 K |
α = 92.69 (3)° | 0.52 × 0.21 × 0.02 mm |
β = 98.29 (3)° | |
Data collection top
Bruker SMART 6000 CCD area-detector diffractometer | 3693 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | 2774 reflections with I > 2σ(I) |
Tmin = 0.715, Tmax = 0.862 | Rint = 0.027 |
9870 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.053 | 2 restraints |
wR(F2) = 0.150 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.35 e Å−3 |
3693 reflections | Δρmin = −0.24 e Å−3 |
249 parameters | |
Special details top
Experimental. The data collection nominally covered full sphere of reciprocal space, by a
combination of 3 runs of narrow-frame ω-scans (scan width 0.3° ω, 20 s
exposure), every run at a different ϕ angle. Crystal to detector distance
4.84 cm. Non-standard lattice setting has been chosen for compatibility with
the high-temperature (monoclinic) phase. |
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. Methyl groups
were refined as rigid bodies rotating around C—C and N—C bonds, with a
common refined U for three H atoms. Amino H atoms: All H-atom parameters
refined, other H atoms: riding model. Pseudo-monoclinic structure: can be
solved refined in the same setting in space group P2/n (unique axis x)
to R_factor_gt = 0.125 (Rint=0.255). |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.11739 (14) | 0.21129 (16) | 0.12804 (15) | 0.0268 (4) | |
H1N | 0.0330 (15) | 0.204 (2) | 0.114 (2) | 0.032* | |
N2 | 0.08770 (15) | 0.43091 (17) | 0.24840 (16) | 0.0349 (4) | |
N3 | 0.38539 (15) | 0.20932 (16) | 0.36845 (15) | 0.0271 (4) | |
H3N | 0.4688 (15) | 0.197 (2) | 0.384 (2) | 0.033* | |
N4 | 0.41607 (15) | 0.41466 (17) | 0.25001 (16) | 0.0334 (4) | |
C1 | 0.17717 (16) | 0.08764 (19) | 0.08130 (17) | 0.0246 (4) | |
C2 | 0.13456 (16) | −0.04100 (19) | 0.11355 (16) | 0.0237 (4) | |
C3 | 0.18637 (17) | −0.16287 (19) | 0.06220 (17) | 0.0272 (4) | |
H3 | 0.1579 | −0.2499 | 0.0835 | 0.033* | |
C4 | 0.27892 (18) | −0.1596 (2) | −0.01945 (18) | 0.0297 (4) | |
H4 | 0.3141 | −0.2436 | −0.0533 | 0.036* | |
C5 | 0.31965 (17) | −0.0333 (2) | −0.05121 (17) | 0.0294 (4) | |
H5 | 0.3833 | −0.0314 | −0.1071 | 0.035* | |
C6 | 0.26959 (17) | 0.0919 (2) | −0.00312 (17) | 0.0270 (4) | |
C7 | 0.03569 (17) | −0.0458 (2) | 0.20329 (17) | 0.0278 (4) | |
H7A | 0.0170 | −0.1427 | 0.2147 | 0.042* | |
H7B | −0.0433 | 0.0043 | 0.1664 | 0.042* | |
H7C | 0.0689 | −0.0022 | 0.2874 | 0.042* | |
C8 | 0.3125 (2) | 0.2270 (2) | −0.0464 (2) | 0.0361 (5) | |
H8A | 0.3837 | 0.2611 | 0.0167 | 0.054* | |
H8B | 0.2405 | 0.2957 | −0.0527 | 0.054* | |
H8C | 0.3414 | 0.2118 | −0.1312 | 0.054* | |
C9 | 0.1286 (2) | 0.5437 (2) | 0.3398 (2) | 0.0381 (5) | |
H9A | 0.2196 | 0.5283 | 0.3745 | 0.057* | |
H9B | 0.0768 | 0.5473 | 0.4109 | 0.057* | |
H9C | 0.1170 | 0.6317 | 0.2956 | 0.057* | |
C10 | −0.0482 (2) | 0.4461 (3) | 0.1969 (3) | 0.0541 (7) | |
H10A | −0.0679 | 0.3807 | 0.1227 | 0.081* | |
H10B | −0.0681 | 0.5412 | 0.1689 | 0.081* | |
H10C | −0.1003 | 0.4265 | 0.2641 | 0.081* | |
C11 | 0.32536 (16) | 0.09702 (19) | 0.41676 (16) | 0.0240 (4) | |
C12 | 0.36720 (16) | −0.03945 (19) | 0.38587 (16) | 0.0239 (4) | |
C13 | 0.31468 (17) | −0.1498 (2) | 0.43824 (17) | 0.0284 (4) | |
H13 | 0.3427 | −0.2422 | 0.4179 | 0.034* | |
C14 | 0.22198 (18) | −0.1273 (2) | 0.52044 (19) | 0.0330 (5) | |
H14 | 0.1864 | −0.2035 | 0.5554 | 0.040* | |
C15 | 0.18238 (18) | 0.0064 (2) | 0.54993 (18) | 0.0327 (5) | |
H15 | 0.1188 | 0.0218 | 0.6057 | 0.039* | |
C16 | 0.23309 (17) | 0.1209 (2) | 0.50054 (17) | 0.0286 (4) | |
C17 | 0.46603 (17) | −0.0656 (2) | 0.29656 (17) | 0.0282 (4) | |
H17A | 0.4861 | −0.1655 | 0.2883 | 0.042* | |
H17B | 0.5444 | −0.0173 | 0.3318 | 0.042* | |
H17C | 0.4322 | −0.0307 | 0.2112 | 0.042* | |
C18 | 0.1909 (2) | 0.2647 (2) | 0.5425 (2) | 0.0408 (5) | |
H18A | 0.1209 | 0.2999 | 0.4783 | 0.061* | |
H18B | 0.2636 | 0.3262 | 0.5497 | 0.061* | |
H18C | 0.1605 | 0.2619 | 0.6267 | 0.061* | |
C19 | 0.3758 (2) | 0.5234 (2) | 0.1595 (2) | 0.0381 (5) | |
H19A | 0.2850 | 0.5134 | 0.1236 | 0.057* | |
H19B | 0.4284 | 0.5156 | 0.0891 | 0.057* | |
H19C | 0.3867 | 0.6145 | 0.2045 | 0.057* | |
C20 | 0.5512 (2) | 0.4227 (3) | 0.3048 (2) | 0.0470 (6) | |
H20A | 0.6044 | 0.4156 | 0.2348 | 0.070* | |
H20B | 0.5751 | 0.3464 | 0.3633 | 0.070* | |
H20C | 0.5650 | 0.5116 | 0.3531 | 0.070* | |
B1 | 0.1714 (2) | 0.3186 (2) | 0.2162 (2) | 0.0268 (5) | |
B2 | 0.3320 (2) | 0.3137 (2) | 0.2816 (2) | 0.0262 (5) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0182 (8) | 0.0331 (9) | 0.0275 (8) | 0.0020 (6) | −0.0011 (6) | −0.0001 (7) |
N2 | 0.0275 (9) | 0.0354 (9) | 0.0375 (10) | 0.0061 (7) | −0.0048 (7) | −0.0066 (7) |
N3 | 0.0177 (8) | 0.0334 (9) | 0.0289 (8) | −0.0010 (6) | −0.0017 (6) | 0.0024 (7) |
N4 | 0.0277 (9) | 0.0345 (9) | 0.0366 (9) | −0.0036 (7) | −0.0025 (7) | 0.0076 (7) |
C1 | 0.0198 (9) | 0.0323 (10) | 0.0192 (9) | 0.0021 (7) | −0.0044 (7) | −0.0015 (7) |
C2 | 0.0176 (9) | 0.0341 (10) | 0.0174 (8) | 0.0005 (7) | −0.0047 (7) | 0.0014 (7) |
C3 | 0.0248 (9) | 0.0305 (10) | 0.0242 (9) | −0.0012 (7) | −0.0037 (8) | 0.0006 (8) |
C4 | 0.0255 (10) | 0.0378 (11) | 0.0235 (9) | 0.0060 (8) | −0.0004 (8) | −0.0040 (8) |
C5 | 0.0218 (9) | 0.0462 (12) | 0.0194 (9) | 0.0019 (8) | 0.0024 (7) | −0.0014 (8) |
C6 | 0.0216 (9) | 0.0383 (11) | 0.0191 (9) | −0.0009 (7) | −0.0036 (7) | 0.0020 (8) |
C7 | 0.0235 (9) | 0.0371 (10) | 0.0220 (9) | −0.0011 (7) | 0.0001 (7) | 0.0023 (8) |
C8 | 0.0349 (11) | 0.0426 (12) | 0.0321 (11) | −0.0022 (9) | 0.0076 (9) | 0.0051 (9) |
C9 | 0.0390 (12) | 0.0322 (11) | 0.0412 (12) | 0.0033 (8) | 0.0023 (9) | −0.0048 (9) |
C10 | 0.0324 (12) | 0.0549 (15) | 0.0668 (16) | 0.0168 (10) | −0.0092 (11) | −0.0177 (12) |
C11 | 0.0193 (9) | 0.0341 (10) | 0.0167 (8) | −0.0012 (7) | −0.0044 (7) | 0.0022 (7) |
C12 | 0.0182 (9) | 0.0347 (10) | 0.0168 (8) | −0.0026 (7) | −0.0048 (7) | 0.0012 (7) |
C13 | 0.0251 (10) | 0.0332 (10) | 0.0249 (9) | −0.0014 (8) | −0.0034 (8) | 0.0023 (8) |
C14 | 0.0278 (10) | 0.0444 (12) | 0.0266 (10) | −0.0098 (8) | −0.0018 (8) | 0.0087 (9) |
C15 | 0.0204 (9) | 0.0566 (13) | 0.0212 (9) | −0.0006 (8) | 0.0029 (7) | 0.0029 (9) |
C16 | 0.0205 (9) | 0.0422 (11) | 0.0208 (9) | 0.0021 (8) | −0.0029 (7) | 0.0002 (8) |
C17 | 0.0229 (9) | 0.0369 (11) | 0.0236 (9) | −0.0001 (8) | 0.0004 (7) | 0.0003 (8) |
C18 | 0.0378 (12) | 0.0506 (13) | 0.0336 (11) | 0.0092 (10) | 0.0092 (9) | −0.0039 (10) |
C19 | 0.0414 (12) | 0.0316 (11) | 0.0412 (12) | −0.0025 (9) | 0.0040 (10) | 0.0053 (9) |
C20 | 0.0301 (11) | 0.0531 (14) | 0.0569 (15) | −0.0127 (10) | −0.0030 (10) | 0.0121 (11) |
B1 | 0.0266 (11) | 0.0289 (11) | 0.0246 (10) | 0.0014 (8) | 0.0024 (8) | 0.0030 (9) |
B2 | 0.0262 (11) | 0.0286 (11) | 0.0227 (10) | 0.0006 (8) | 0.0022 (8) | −0.0033 (8) |
Geometric parameters (Å, º) top
N1—C1 | 1.422 (2) | C9—H9B | 0.9798 |
N1—B1 | 1.433 (3) | C9—H9C | 0.9797 |
N1—H1N | 0.883 (15) | C10—H10A | 0.9796 |
N2—B1 | 1.423 (3) | C10—H10B | 0.9801 |
N2—C9 | 1.450 (3) | C10—H10C | 0.9798 |
N2—C10 | 1.455 (3) | C11—C16 | 1.401 (3) |
N3—C11 | 1.424 (2) | C11—C12 | 1.407 (3) |
N3—B2 | 1.428 (3) | C12—C13 | 1.390 (3) |
N3—H3N | 0.871 (15) | C12—C17 | 1.498 (3) |
N4—B2 | 1.424 (3) | C13—C14 | 1.392 (3) |
N4—C19 | 1.453 (3) | C13—H13 | 0.9501 |
N4—C20 | 1.456 (3) | C14—C15 | 1.372 (3) |
C1—C6 | 1.405 (3) | C14—H14 | 0.9500 |
C1—C2 | 1.409 (3) | C15—C16 | 1.398 (3) |
C2—C3 | 1.390 (3) | C15—H15 | 0.9502 |
C2—C7 | 1.499 (3) | C16—C18 | 1.503 (3) |
C3—C4 | 1.385 (3) | C17—H17A | 0.9799 |
C3—H3 | 0.9501 | C17—H17B | 0.9799 |
C4—C5 | 1.379 (3) | C17—H17C | 0.9799 |
C4—H4 | 0.9500 | C18—H18A | 0.9802 |
C5—C6 | 1.396 (3) | C18—H18B | 0.9799 |
C5—H5 | 0.9499 | C18—H18C | 0.9802 |
C6—C8 | 1.507 (3) | C19—H19A | 0.9802 |
C7—H7A | 0.9797 | C19—H19B | 0.9800 |
C7—H7B | 0.9800 | C19—H19C | 0.9803 |
C7—H7C | 0.9802 | C20—H20A | 0.9800 |
C8—H8A | 0.9800 | C20—H20B | 0.9800 |
C8—H8B | 0.9801 | C20—H20C | 0.9800 |
C8—H8C | 0.9802 | B1—B2 | 1.726 (3) |
C9—H9A | 0.9801 | | |
| | | |
C1—N1—B1 | 129.55 (15) | N2—C10—H10C | 109.5 |
C1—N1—H1N | 109.4 (13) | H10A—C10—H10C | 109.5 |
B1—N1—H1N | 119.0 (13) | H10B—C10—H10C | 109.4 |
B1—N2—C9 | 123.34 (16) | C16—C11—C12 | 120.23 (17) |
B1—N2—C10 | 124.88 (17) | C16—C11—N3 | 121.16 (17) |
C9—N2—C10 | 111.77 (16) | C12—C11—N3 | 118.46 (16) |
C11—N3—B2 | 129.98 (16) | C13—C12—C11 | 119.12 (17) |
C11—N3—H3N | 109.8 (13) | C13—C12—C17 | 120.40 (17) |
B2—N3—H3N | 118.8 (14) | C11—C12—C17 | 120.48 (16) |
B2—N4—C19 | 123.48 (16) | C12—C13—C14 | 121.09 (18) |
B2—N4—C20 | 124.54 (17) | C12—C13—H13 | 119.5 |
C19—N4—C20 | 111.98 (17) | C14—C13—H13 | 119.4 |
C6—C1—C2 | 120.10 (17) | C15—C14—C13 | 119.12 (18) |
C6—C1—N1 | 121.36 (17) | C15—C14—H14 | 120.5 |
C2—C1—N1 | 118.36 (16) | C13—C14—H14 | 120.4 |
C3—C2—C1 | 119.14 (17) | C14—C15—C16 | 121.92 (18) |
C3—C2—C7 | 120.66 (17) | C14—C15—H15 | 119.2 |
C1—C2—C7 | 120.20 (16) | C16—C15—H15 | 118.9 |
C4—C3—C2 | 121.10 (17) | C15—C16—C11 | 118.51 (18) |
C4—C3—H3 | 119.4 | C15—C16—C18 | 119.23 (18) |
C2—C3—H3 | 119.5 | C11—C16—C18 | 122.22 (18) |
C5—C4—C3 | 119.46 (17) | C12—C17—H17A | 109.7 |
C5—C4—H4 | 120.3 | C12—C17—H17B | 109.3 |
C3—C4—H4 | 120.3 | H17A—C17—H17B | 109.5 |
C4—C5—C6 | 121.56 (18) | C12—C17—H17C | 109.4 |
C4—C5—H5 | 119.2 | H17A—C17—H17C | 109.5 |
C6—C5—H5 | 119.2 | H17B—C17—H17C | 109.5 |
C5—C6—C1 | 118.63 (17) | C16—C18—H18A | 109.5 |
C5—C6—C8 | 119.36 (17) | C16—C18—H18B | 109.5 |
C1—C6—C8 | 121.98 (17) | H18A—C18—H18B | 109.5 |
C2—C7—H7A | 109.4 | C16—C18—H18C | 109.4 |
C2—C7—H7B | 109.5 | H18A—C18—H18C | 109.5 |
H7A—C7—H7B | 109.5 | H18B—C18—H18C | 109.5 |
C2—C7—H7C | 109.4 | N4—C19—H19A | 109.5 |
H7A—C7—H7C | 109.5 | N4—C19—H19B | 109.4 |
H7B—C7—H7C | 109.5 | H19A—C19—H19B | 109.5 |
C6—C8—H8A | 109.4 | N4—C19—H19C | 109.6 |
C6—C8—H8B | 109.6 | H19A—C19—H19C | 109.5 |
H8A—C8—H8B | 109.5 | H19B—C19—H19C | 109.5 |
C6—C8—H8C | 109.3 | N4—C20—H20A | 109.5 |
H8A—C8—H8C | 109.5 | N4—C20—H20B | 109.5 |
H8B—C8—H8C | 109.5 | H20A—C20—H20B | 109.5 |
N2—C9—H9A | 109.4 | N4—C20—H20C | 109.5 |
N2—C9—H9B | 109.6 | H20A—C20—H20C | 109.5 |
H9A—C9—H9B | 109.5 | H20B—C20—H20C | 109.5 |
N2—C9—H9C | 109.4 | N2—B1—N1 | 117.63 (17) |
H9A—C9—H9C | 109.5 | N2—B1—B2 | 120.61 (16) |
H9B—C9—H9C | 109.5 | N1—B1—B2 | 121.76 (16) |
N2—C10—H10A | 109.3 | N4—B2—N3 | 117.68 (17) |
N2—C10—H10B | 109.6 | N4—B2—B1 | 120.63 (16) |
H10A—C10—H10B | 109.4 | N3—B2—B1 | 121.69 (17) |
| | | |
C2—C1—N1—B1 | 116.0 (2) | B2—N3—C11—C12 | 117.3 (2) |
C1—N1—B1—B2 | 1.3 (3) | C6—C1—N1—B1 | −68.8 (3) |
N1—B1—B2—N3 | −66.0 (2) | C16—C11—N2—B2 | 149.46 (15) |
B1—B2—N3—C11 | −0.2 (3) | N3—B1—B2—N4 | 180.0 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···C3i | 0.88 (2) | 2.76 (2) | 3.544 (2) | 148 (2) |
N3—H3N···C13ii | 0.87 (2) | 2.76 (2) | 3.528 (3) | 148 (2) |
Symmetry codes: (i) −x, −y, −z; (ii) −x+1, −y, −z+1. |
Experimental details
| (aI) | (bI) |
Crystal data |
Chemical formula | C20H32B2N4 | C20H32B2N4 |
Mr | 350.12 | 350.12 |
Crystal system, space group | Monoclinic, P2/n | Triclinic, P1 |
Temperature (K) | 200 | 120 |
a, b, c (Å) | 10.4957 (11), 9.6327 (10), 10.5554 (11) | 10.5043 (13), 9.6449 (11), 10.4428 (14) |
α, β, γ (°) | 90, 98.06 (2), 90 | 92.69 (3), 98.29 (3), 87.45 (3) |
V (Å3) | 1056.63 (19) | 1045.0 (2) |
Z | 2 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.07 | 0.07 |
Crystal size (mm) | 0.53 × 0.35 × 0.05 | 0.52 × 0.21 × 0.02 |
|
Data collection |
Diffractometer | Siemens SMART 1000 CCD area-detector diffractometer | Bruker SMART 6000 CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2006) | Multi-scan (SADABS; Sheldrick, 2006) |
Tmin, Tmax | 0.924, 1.000 | 0.715, 0.862 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10983, 2436, 1779 | 9870, 3693, 2774 |
Rint | 0.028 | 0.027 |
(sin θ/λ)max (Å−1) | 0.649 | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.128, 1.05 | 0.053, 0.150, 1.05 |
No. of reflections | 2436 | 3693 |
No. of parameters | 124 | 249 |
No. of restraints | 1 | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.28, −0.16 | 0.35, −0.24 |
Selected bond lengths (Å) for (aI) topN1—C1 | 1.4237 (16) | N2—B1 | 1.4197 (19) |
N1—B1 | 1.4290 (19) | B1—B1i | 1.727 (3) |
Symmetry code: (i) −x+1/2, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) for (aI) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···C3ii | 0.871 (12) | 2.773 (13) | 3.5631 (18) | 151.6 (13) |
Symmetry code: (ii) −x, −y, −z. |
Selected bond lengths (Å) for (bI) topN1—C1 | 1.422 (2) | N3—B2 | 1.428 (3) |
N1—B1 | 1.433 (3) | N4—B2 | 1.424 (3) |
N2—B1 | 1.423 (3) | B1—B2 | 1.726 (3) |
N3—C11 | 1.424 (2) | | |
Hydrogen-bond geometry (Å, º) for (bI) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···C3i | 0.883 (15) | 2.763 (17) | 3.544 (2) | 148.3 (17) |
N3—H3N···C13ii | 0.871 (15) | 2.757 (17) | 3.528 (3) | 148.3 (17) |
Symmetry codes: (i) −x, −y, −z; (ii) −x+1, −y, −z+1. |
Tetra(amido)diborane(4) derivatives are important as precursors in diborane(4) chemistry (Brotherton, 1964), especially since the Suzuki reaction became widely used in the synthesis of complex molecular species (Miyaura & Suzuki, 1995). The title compound, (I), was first reported by Patton et al. (2001). In the course of our studies of substitution reactions in diboranes (Baber et al., 2005), we reproduced the synthesis of (I) and structurally characterized it by X-ray diffraction, which revealed a phase transition.
Under ambient conditions, (I) is monoclinic. On slow cooling, this α form (fully studied at 200 K) persisted to 160 K, as was indicated by express lattice determinations at 292, 274, 250, 230, 200, 180 and 160 K. The phase transition was observed between 160 and 150 K, at which point the peaks of most reflections became split, but the separations between the maxima were not wide enough to index the components separately. If flash-cooled below 150 K, the crystals shattered. After several unsuccessful attempts, we obtained just one crystal of the low-temperature phase, β-(I), by annealing a crystal with three cycles of cooling–heating above the phase transition (230 to 160 K) before finally cooling it down to 120 K. On warming to 230 K, the crystal remained triclinic, but cracked on warming to room temperature. We tried the annealing procedure on other samples but without success.
The structure of β-(I), determined from the data set collected at 120 K, is triclinic, although the actual difference from α-(I) is small. To simplify the comparison, β-(I) is presented here in the (non-standard) pseudo-monoclinic lattice setting analogous to that of α-(I). Interestingly, this lattice of β-(I) can be transformed by the operation (1 0 1 / 1 0 1 / 0 1 0) to a C-centred pseudo-monoclinic lattice with a = 15.844, b = 13.702 and c = 9.645 Å, α = 89.91, β = 93.46 and γ = 89.66°, and V = 2090 Å3. However, we found no approximate structural or Laue symmetry (Rint = 0.51) associated with this cell.
The molecular structure of (I) (Fig. 1) is very similar to that of its mesityl analogue, 1,2-bis(2,4,6-trimethylanilide)-1,2-bis-(dimethylamido)diborane, (II) (Firinci et al., 2010). In the α-(I) form, the molecule possesses a crystallographic twofold axis passing through the midpoint of the B—B bond. In the β form, this twofold symmetry was noncrystallographic yet almost perfect. In fact, the structure of β-(I) can be solved and refined to R1 = 0.125 (Rint = 0.255) in the space group P2/n of the α phase, ignoring the deviation of α and γ angles from 90°.
All B and N atoms have planar–trigonal geometry. In each case, the planes of a B atom and its two adjacent N atoms coincide within experimental error, and the B—N distances indicate a degree of multiple bonding (Weber et al., 2001). On the other hand, strong twists around the B—B bond [67.6 (2)° in α-(I) and 65.9 (2)° in β-(I)] and around the N—C(Ar) bonds [69.2 (2)° in α-(I), and 67.1 (2) and 68.8 (2)° in β-(I)] preclude any π-conjugation. Thus, the B—B bond is essentially single; its length falls within the usual range of 1.69–1.75 Å for tetramido-diborane derivatives (Weber et al., 2001; Baber et al., 2005) and is practically the same as in (II) [1.735 (6) Å].
The two dimethylarene groups in molecule (I) are nearly parallel, the interplanar angle being 3.5 (1)° in both forms. These groups stack closely together in a offset face-to-face manner, with mean interplanar separations of 3.48 and 3.46 Å in the α and β forms, respectively. Similar stacking occurs between the dimethylarenes of adjacent molecules related by an inversion centre. In this case the arene planes are rigorously parallel, with interplanar separations of 3.43 Å in α-(I) and 3.39 Å in β-(I). Thus, the structure containes an infinite stacking motif, running parallel to the [011] direction.
Since the lone electron pairs of the N atoms are involved in π conjugation, the molecule of (I) contains no electronegative acceptors for strong hydrogen bonds. The N—H bonds point roughly towards the π orbitals of arene C atoms of adjacent molecules within the stack. In α-(I) there is one symmetrically independent such contact, N1—H1N···C3(-x, -y, -z), whereas in β-(I) there are two, one with the same notation and the other N3—H3N···C13(1 - x, -y, 1 - z). These H···C distances are 2.77 (1), and 2.76 (2) and 2.76 (2) Å, respectively. Rowland & Taylor (1996) estimated the standard van der Waals H···C separation as 3.02 Å, using H-atom positions normalized by moving the H atom along the observed X—H bond until this bond length matched the neutron diffraction value (0.983 Å for N—H). Applying such normalization to (I) reduces the above-mentioned H···C distances to 2.67, and 2.68 and 2.66 Å, respectively, hence these contacts can be regarded as weak hydrogen bonds (Desiraju & Steiner, 1999).