Studies on Selenium – Iodine Halogen Bonding

Melina Raymundo, Will Lynch, and Clifford Padgett

Armstrong Student Scholars DayApril 21, 2016

Halogen Bonding• Halogen bonding: donor / acceptor interactions that involve a halogen

atom• Little information is available on factors that influence the selenium /

iodine halogen bond• Standard convention in our study is the electron acceptor is the iodine

whereas the donor atom is the selenide

History of Halogen Bonding• 1814: Gay-Lussac and Colin described I2

…NH3

• 1819: Pelletier described I3-

• 1863: Guthrie described the composition of I2…NH3

• 1896: Remsen described the composition Br2/Cl2 amine complexes

• 1948: Hildebrand/Benesi first described as donor/acceptor interactions

• 1966/69: Hassel and Mulliken (Nobel Laureates) described in ground

breaking chemical bonding discussions

• Current uses and areas of interest:

Soft Supramolecular Gels, Liquid Crystals, Porous Membranes, Pharmaceuticals, Catalysis, Light Emitting and Optical Materials

Synthesis and Crystallization of Tris(p-methoxyphenyl)phosphine selenide (p-MeOPh)3PSe

• 0.20 g (p-MeOPh)3P (0.57 mmol) is dissolved in minimal MeOH

• 0.045 g of Se metal (0.57 mmol) is also dissolved in minimal MeOH

• Combined in one portion and stirred for 10 minutes.

• X-ray quality crystals were grown by slow evaporation of the solvent.

(p-MeOPh)3PSe X-ray DataCollection

• Colorless Crystal 0.400 x 0.200 x 0.200 mm

• Reflections: 10421

• Unique Reflections: 4535

• Space Group: Monoclinic, Cc

• Formula: C21H21O3PSe

• FW= 431.33 g/mole

• D= 1.427 g/cm3

• Z= 4

• R= 0.032

Cell Parameters

• a = 16.442(11) Å

• b = 10.991(7) Å

• c = 11.722(8) Å

• V = 2008(3) Å3

(p-MeOPh)3PSe Asymmetric Unit

Atoms Bond Length

P1—Se1 2.12 (12)Å

Unit Cell of (p-MeOPh)3PSe

(p-MeOPh)3P=Se and DITFB Reaction

Synthesis and Crystallization of 1:1 Ratio of (p-methoxy)3PSe and 1,4-Diiodotetrafluorobenzene

• 0.168 g (p-MeOPh)3PSe (0.390 mmol) is dissolved in minimal methylene chloride

• 0.157 g of DITFB (0.390 mmol) is also dissolved in minimal methylene chloride

• The solutions are combined and stirred for 10 min

• X-ray quality crystals were grown by slow evaporation of the solvent

X-ray Data for (p-MeOPh)3PSe : C6F4I2

Collection

• Colorless Crystal 0.400 x 0.400 x 0.200 mm

• Reflections: 17666

• Unique Reflections: 7557

• Space Group:

• Formula: C27H21F4I2O3PSe

• FW= 833.20 g/mole

• D= 1.678 g/cm3

• Z= 2

• R= 0.045

Cell Parameters

• a = 11.581(4) Å

• b = 12.274(5) Å

• c = 14.084(4) Å

• V = 1649.1(11) Å3

Asymmetric Unit for (p-MeOPh)3PSe : C6F4I2

Atoms Bond Length

P1—Se1 2.139 (2) Å

Se1—I1 3.37 (2) Å

Unit Cell for (p-MeOPh)3PSe : C6F4I2

(o-tolyl)3PSe and DITFB Reaction

X-ray Data(o-tolyl)3PSe : C6F4I2

Collection

• Colorless Crystal 0.400 x 0.300 x 0.200 mm

• Reflections: 27255

• Unique Reflections: 6202

• Space Group: Monoclinic, P2(1)/c

• Formula: C27H21F4I2PSe

• FW= 785.1389 g/mole

• D= 7.985 g/cm3

• Z= 2

• R= 0.040

Cell Parameters

• a = 12.846(8) Å

• b = 26.35(2) Å

• c = 8.034(5) Å

• V = 2712(3) Å3

(o-tolyl)3PSe : C6F4I2 Asymmetric Unit

Atoms Bond Length

P1—Se1 2.140(2) Å

Se1—I1 3.505(3) Å

(o-tolyl)3PSe : C6F4I2 Unit Cell

(p-tolyl)3PSe and DITFB Reaction

X-ray Data for (p-tolyl)3PSe : C6F4I2

Collection• Colorless Crystal • 0.400 x 0.200 x 0.200 mm• Reflections: 24412 • Unique Reflections: 5368 • Space Group: Monoclinic, P2(1)/c

• Formula: C27H21F4I2PSe • FW= 785.1389 g/mole• D= 1.661 g/cm3

• Z= 4• R= 0.0525

Cell Parameters

• a = 13.422(6) Å

• b = 12.148(5) Å

• c = 14.773(7) Å

• V = 2336(2) Å3

(p-tolyl)3PSe : C6F4I2 Asymmetric Unit

Atoms Bond Length

P1—Se1 2.116 (1) Å

Se1—I1 3.317(2) Å

(p-tolyl)3PSe: C6F4I2 Unit Cell

(p-FPh)3PSe and DITFB Reaction

X-ray Data(p-FPh)3PSe : C6F4I2

Collection• Colorless Crystal • 0.500 x 0.200 x 0.200 mm• Reflections: 18213• Unique Reflections: 7777• Space Group: Triclinic, P-1

• Formula: C24H12F7I2PSe• FW= 797.08 g/mole• D= 1.546 g/cm3

• Z= 2• R= 0.0538

Cell Parameters

• a = 8.461(6) Å

• b = 11.993(8) Å

• c = 17.202(12) Å

• V = 1712(2) Å3

(p-FPh)3PSe : C6F4I2 Asymmetric Unit

Atoms Bond Length

P1—Se1 2.133 Å

Se1—I1 3.408 Å

(p-FPh)3PSe: C6F4I2 Unit Cell

Table of Data Parameters

Complex P=Se (Å) 31P=Se (δδδδ)NMR (ppm)

Hammett(σσσσ)

P=79Se (δδδδ)NMR (ppm)

P=Se…I (Å) Se…I (Å) P=Se…I (⁰)

PPh3 2.110* 35.3 0.00* -266.2 2.127* 3.494* 113.01*

P(p-MeOPh)3 2.12 31.7 -0.27* -249.9 2.139 3.37 103.39

P(p-tolyl)3 2.112* 34.3 -0.17* -261.0 2.116 3.317 98.41

P(o-tolyl)3 Lit. data XXX XXX 2.140 3.505 103.32

P(p-FPh)3 2.114* 32.3 +0.06* -250.4 2.133 3.408 92.85

* Literature value

Conclusions

• Standard parameters do not predict bond length of P-Se or Se…I interactions

• Calculated bond orders are 1.45+0.01* may give insight

• Charge distribution calculations are 0.86+0.01* for P and -0.47+0.01* for Se in these compounds

• Sterics may be the largest factor in determining halogen bond lengths

* Alvarado, S. R., et. al. Organometallics, 2015, 4023-4031.

Acknowledgement

• Dr. Will Lynch, Dr. Clifford Padgett, Department of Chemistry and Physics, Armstrong State University