Heavier Gp 13 and 14 Multiple Bonded Species Have ʻStrainedʼ … Oulu... · 2012. 8. 29. ·...

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Heavier Gp 13 and 14 Multiple Bonded Species Have ‘Strained’ Geometries and Quasi Open-Shell Configurations.

The Isolation of Boron-Boron Multiple Bonds in Molecules Generally requires the Addition of Electrons. �

B covalent radius a = 0.85 Å ➞ B-‐B single bond = 1.70 Å B-‐B bonds ≈ 1.6 Å known for metal borides.b

1.636(7) Å(Berndt,c Power, Structure d)

1.636(10) Å (Power e)

1.561(18) Å (Robinson f)

1.449(3) Å (Braunschweig g)

a. Pykkö, P.; Atsumi, M. Chem. Eur. J. 2009, 15, 186. b. Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford University Press: Oxford, 1984. pp. 1052. c. Klusik, H.; Berndt, A. Angew. Chem. Int. Ed. 1981, 20, 870. d. Grigsby, W. G.; Power, P. P. Chem. Commun. 1996, 2235. e. Moezzi, A.; Bartle`, R. A.; Power, P. P. Angew. Chem. Int. Ed. 1992, 31, 1082-‐1083. f. Wang, Y.; Quillian, B.; Wei, P.; Wannere, C. S.; Xie, Y.; King, R. B.; Schaeffer, H. F.; von Schleyer, P. R.; Robinson, G. H. J. Am. Chem. Soc. 2007, 129, 13380. g H. Braunschweig, R.D. Dewhurst, K. Hammond, J. Mies, K. Radacki, A. Vargas Science 2012, 336, 1420.

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Multiple Bonds in the Heavier Group 13 Metals also Require Added El. Density�Covalent Radius Al = 1.25 Å, Ga = 1.20 Å, In = 1.40 Å, Tl = 1.45 Åa

Single bonds R2Al–AlR2 (R = CH(SiMe3)2); Al—Al = 2.660(1) Å (Uhl, 1988)b

(trivalent) R2Ga–GaR2 (R = CH(SiMe3)2); Ga–Ga = 2.541(1) Å (Uhl, 1989)c

R2In–InR2 In–In = 2.828(1) Å (Uhl, 1989)c

Single bonds (AlCp*)4 (Al–Al) = 2.773(4) Å) (Schnöckel, 1991)d

(monovalent) (GaC(SiMe3)3)4 (Ga–Ga) = 2.69 Å (avg.) (Uhl, 1992)e (InC(SiMe3)3)4 (In–In) = 2.84 Å (avg.) (Cowley, 1993)f (TlC(SiMe3)3)4 (Tl–Tl) = 3.33-‐3.64 Å (Uhl, 1997)g

Al–Al = 2.53(1) Å (Porschke, Uhl, 1993)h

Ga–Ga = 2.343(2) Å (Power, 1993)i

Double Bonds

M = Ga, 2.6268(7) Å (Power, 2002)j In, 2.9786(5) Å (Power, 2002)k

Tl, 3.0936(8) Å (Power, 2005)l

Triple Bonds

Ga–Ga = 2.319(2) Å (Robinson, 1997)m

Al–Al = 2.428(1) Å (Power, 2006)n

a. Huheey, J. E. Inorganic Chemistry, 3rd ed.; Harper and Row: New York, 1983. pp. 258. b. Uhl, W. Z. Naturforsch. 1988, 43B, 1113. c. Uhl et al. J. Organomet. Chem. 1989, 364, 289. d. Schnöckel et al. Angew. Chem. Int. Ed. 1991, 30, 564. e. Uhl et al. Angew. Chem. Int. Ed. 1992, 31, 1364. f. Cowley et al. J. Coord. Chem. 1993, 30, 25. g. Uhl et al. Angew. Chem. Int. Ed. 1997, 36, 64. h. Porschke, K. Angew. Chem. Int. Ed. 1993, 32, 388. i. Power et al. Angew. Chem. Int. Ed. 1993, 32, 717. j. Power et al. Angew. Chem. Int. Ed. 2002, 41, 2842. k. Power et al. J. Am. Chem. Soc. 2002, 124, 8538. l. Power et al. J. Am. Chem. Soc. 2005, 127, 4794. m. Uhl et al. J. Am. Chem. Soc. 1997, 119, 5741. n. Power et al. Angew. Chem. Int. Ed. 2006, 45, 5953. 14

Sesqui Bonds

4

13! 14!B! C!Al! Si!Ga! Ge!In! Sn!Tl! Pb!

E EAriPr4

AriPr4E E

AriPr4

AriPr4Ar'AriPr4!

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Frontier Molecular Orbital Comparison

Group 13 vs. Heavy Group 14 vs. Alkene Molecules

Differences in reactivity observed. Are they a result of steric or electronic effects or both?

Various Structural Mopfs of (RM)n Clusters and Monomers

n = 9 n = 6 n = 4, R = C(SiMe3)3

n = 2 n = 1

Structures of the Three Heaviest Dimetallenes

Dimetallene M-M distance (Å) 2(Covalent Radius) (Å) Ar'-M-M (deg)

AriPr4GaGaAriPr4 2.6268(7) 2(1.25 Å) = 2.5 123.16(7)

AriPr4InInAriPr4 2.9786(5) 2(1.42 Å) = 2.84 121.23(6)

AriPr4TlTlAriPr4 3.0936(8) 2(1.49 Å) = 2.98 119.7(1)

Angew. Chem. Int. Ed. Engl. 2002, 41, 2842; J. Am. Chem. Soc. 2003, 125, 2669

J. Am. Chem. Soc. 2002, 124, 8538 J. Am. Chem. Soc. 2005, 127, 4794

Å

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Synthesis of the Dialuminene and its Oxidation and Reduction

J. Am. Chem. Soc., 2003, 125, 10784

Angew. Chem. Int.Ed. 2006, 45, 5953

Al-Al= 2.428(1)Å Al-Al= 2.5828(7)Å

J.Moilanen, P. P. Power, H. M. Tounonen, Inorg. Chem. 2010, 49, 10992.

Molecular Orbitals in Heavier Group 13 Dimetallenes

LUMO

HOMO

σ*(bu)

π* (bg)

n+ (ag)

π (au)

n-‐ (bu)

σ (ag)

Triplet Ground State

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Singlet Ground State

(out of phase π)

(in phase π)

10

σ (Ga-‐Ga) 247

HOMO 248 πin or n_

LUMO 249 πout

250 πin* or n+

AriPr4GaGaAriPr4

Orbital No.

344.65 nm f=0.0436, 247 -‐> 249, 0.58563, σ → πout 248 -‐> 252,-‐0.22450 248 -‐> 253, -‐0.19586 486.67 nm f=0.2874, 248 -‐> 250, 0.59676, πin → πin*or n+ 685.80 nm f=0.0001, 248 -‐> 249, 0.65428, πin → πout or n_

Note: all dimers have same order of energy levels: σ, πin , πout , πin*.

Predicted Electronic Spectra of Dimerized Species

Zhu, Z., Fischer, R.C., Ellis, B.D., Rivard, E., Merrill, W.A., Olmstead, M.M., Guo, J.-D., Nagase, S., Power, P.P., Pu, L. Chem. Eur. J., 2009, 15, 5263.!

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Group 13: Weak Ga-Ga Bonds Dissociate to Monomers in Hydrocarbon Solution

Centroid-‐C(1)-‐Centroid Angles:

Ar’ = 158.1° 3, 5-‐PriAr' = 150.3 °

Increasing Steric Bulk

AriPr4

AriPr6

AriPr8

AriPr8

AriPr4


Dimerization is Seen Even with Six i-Pr Substituted Ligands as in (p-tBuAriPr6Ga)2 and (p-CF3AriPr6Ga)2 �

UV/vis (hexanes) λmax nm (ε mol L-1 cm-1)

354 (4600), 442 (2900) 344 (3000), 442 (160)


Monomeric Structures if i-Pr Groups are Included on the Central Aryl Ring, as in AriPr6,2Ga and AriPr4,2Ga

UV/vis (hexanes) λmax nm (ε mol L-1 cm-1): AriPr6,2Ga, 350(1600), 437(520); AriPr4,2Ga, 352(3200), 436(1400).


14

Ga(1)

C(1)

UV-Vis λmax (ε) 351 nm (1120) 437 nm (460)

Ga(1)-C(1) 2.034(6) Å

Group 13: FMOs of Ga Monomers and a Solid State Structure

AriPr8GaGaAriPr8 2 AriPr8Ga:

πout

πin

LUMO

HOMO n All monomers calculated to have the same energy levels: n, πout*, πin*.


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Cal. Exp.

λ (nm) f transition λ (nm) ε

monomers

iPr4ArGa: 352 448

0.0479 0.0167

n → πin n → πout

352 436

3200 1400

iPr6ArGa: 354 450

0.0712 0.0164


350 436

1900 700

iPr8ArGa: 351 449

0.0579 0.0158


350 437

1600 520

dimers

(4-tBuiPr6ArGa)2 <C1>

382 448 821

0.0056 0.3329 0.0058

σ → πout πin → πin* πin → πout

(4-CF3iPr6ArGa)2

<C1> 381 460 807

0.0051 0.2269 0.0097

σ → πout πin → πin* πin → πout

monomers

4-tBuiPr6ArGa: 357 447

0.0707 0.0169


354 442

4600 2900

4-CF3iPr6ArGa: 347

457 0.0722 0.0136


344 442

3000 160

Experimental and Calculated Electronic Spectra Of Aryl Gallium Species�

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Group 13: Reaction of AriPr4GaGaAriPr4 with Ethylene

R1 = 6.1 % P21/n

2

Ga(1)-C(1) 1.964(3) Å

Ga(1)-C(62) 1.971(3) Å

Ga(1)-C(64) 1.968(4) Å

C(61)-C(62) 1.544(5) Å

C(63)-C(64) 1.546(5) Å

∑ angles Ga 359.8º

[2+2+2]

Caputo, C.A., Zhu, Z., Brown, Z.D., Fettinger, J.C., Power, P.P. Chem. Commun. 2011, 47, 7506.

colourless m.p. 281 ºC

AriPr4Ga GaAriPr4AriPr4GaGaAriPr4

Heavier Gp 13 and 14 Multiple Bonded Species Have ʻStrainedʼ … Oulu... · 2012. 8. 29. ·...

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