Spezielle Aspekte der Hauptgruppenelementchemie VO CHE.361 Spezielle Aspekte der Hauptgruppenelementchemie Teil 1: Ao.-Univ.Prof. Dr. Ferdinand Belaj Teil 2:Ao.-Univ.Prof. Dr. Harald Stüger

Teil 1: Niedervalente Hauptgruppenelementverbindungen Diskussion am Beispiel der 4. Hauptgruppe: R2Si: R2Ge: R2Sn: R2Pb: höhere Carbenanaloge (Heterocarbene) Silylen Germylen Stannylen Plumbylen "nicht klassische" Mehrfachbindungssysteme R2Si=CR2 R2Si=SiR2 RSiSiR X=SiR2 Silene Disilene Disilyne Heterosilene Polysilylene -(R2Si)n- Polysilane

Heterocarbene Heterocarbene EH2 mit einem Zentralatom E aus der dritten oder einer höheren Periode (n > 2) liegen in einem Singulett-Grundzustand vor. pz pz py 90° s 120° sp2 px

Voraussetzungen für das Entstehen von Hybridorbitalen: • Eine niedrige Promotionsenergie, die durch den Energieunterschied Es-Ep der Valenzorbitale angenähert werden kann. • Eine vergleichbare räumliche Ausdehnung der mischenden Orbitale  Die Elemente höherer Perioden (n > 2) sind hybridisierungsunwillig

-Donorsubstituenten -Akzeptorsubstituenten NR2; OR, Cl -Akzeptorsubstituenten aryl, vinyl, ethinyl

-Donorsubstituenten -Akzeptorsubstituenten R3Si, R3Ge... -Akzeptorsubstituenten F, CF3...

Darstellung

SiCl4 + Si  2 SiCl2

250°C oder X = H, Cl, NR2, SR

Additionsreaktionen Elektrophil Nucleophil

Me2Si: + Ph-CC-Ph Me3SiCCSiMe3

29

Insertionsreaktionen H2Si > ClH2Si > FHSi > Cl2Si > F2Si Elektrophil Nucleophil (MeO)2Si: π-Donorwirkung verringert Reaktivität (pz nicht elektrophil genug; keine Reaktion mit R3SiH F2Si: σ-Akzeptorwirkung verringert Reaktivität (3s nicht nucleophil genug; unreaktiv H2Si > ClH2Si > FHSi > Cl2Si > F2Si

Komplexbildung mit n-Donoren

Dimerisierung/Polymerisation

T = 300 K T = 120 K: R2Si=SiR2 T = 77 K: R2Si:

Stabilisierung

tris(trimethylsilyl)silyl hypersilyl supersilyl Si tris(trimethylsilyl)silyl hypersilyl

Stabile Silylene cp*2SiCl2 1-cp*2SiI2 1-cp*SiBr3 farbloser Feststoff; thermisch stabil (FP = 171°C) cp*2SiCl2 LiC10H8/THF δ29Si = - 397 ppm Jutzi et al. 1986 erste stabile Si(II)-Verbindung R-CC-R I2 Br2 1-cp*2SiI2 1-cp*SiBr3

Arduengo et al. 1991 West et al. 1994 farbloser Feststoff; bei 90°C (0.01 mbar) destillierbar; bei 150 °C über Monate stabil; Zerfall erst beim FP (220°C) keine Insertion in Si-H keine Addition an PhC≡CPh keine Komplexe mit R3N δ29Si = 78 ppm

HOMO HOMO

stabil bis -20°C: Zerfall bei Raumtemperatur West et al. 2003 stabil bis -20°C: Zerfall bei Raumtemperatur

West et al. 2003 farbloser Feststoff; in Lösung langsamer Zerfall bei 25°C innerhalb mehrerer Stunden δ29Si = 119 ppm

farbloser Feststoff; in Lösung langsamer Zerfall bei 25°C (t1/2 = 31h) Kira et al. 1999 δ29Si = 567,4 ppm farbloser Feststoff; in Lösung langsamer Zerfall bei 25°C (t1/2 = 31h)

langsamer Zerfall bei 25°C (t1/2 = 20min) stabil bei -60°C; langsamer Zerfall bei 25°C (t1/2 = 20min) stabil bei -20°C; langsamer Zerfall bei 25°C (t1/2 = 3h)

Kira et al. 2007 Kira et al. 2003

West et al. 1994 4 δ29Si = 97,5 ppm δ29Si = 448 ppm Kira et al. 2008

stable at room temperature δ29Si = 19,6 ppm Roesky et al. 2009 stable at room temperature δ29Si = 19,6 ppm Roesky et al. 2010 δ29Si = 43,2 ppm

Silylenkomplexe Fischer 1964 Zybill 1987 Si tetraedrisch koordiniert d(Fe-Si) relativ lang Fe-Si Bindung frei drehbar

(CN) rel. hoch d(Ru-Si) leicht verkürzt Si tetraedrisch koordiniert Tilley 1987 29Si = 95,75 ppm Tilley 1990 29Si = 250,6 ppm Tilley 1994 d(Ru-Si) = 223,8 pm Si trigonal planar 29Si = 299 ppm

d(Pt-Si) = 221 pm Si trigonal planar 29Si = 360 ppm 29Si = 338,5 ppm

Mehrfachbindungen von Elementen n  3 Geschichtliches Köhler, Michaelis, Ber. Dtsch. Chem. Ges. 1877, 10, 807 Kuchen, Buchwald, Chem. Ber. 1958, 2296 Ehrlich, Bertheim, Ber. Dtsch. Chem. Ges. 1912, 45, 756. Lloyd, Morgan, Nicholson, Ronimus, Angew. Chem. (Int. Ed.) 2005, 44, 941. Kipping, J. Chem. Soc. 1911, 27, 143 Kipping, Murray, Maltby, J. Chem. Soc., 1229, 1180

Doppelbindungs Regel: Elemente jenseits der zweiten Periode des PSE bilden keine Mehrfachbindungen mit sich oder anderen Elementen. Yoshifuji 1981 Niecke 1973 Becker 1976 meanwhile..... Lappert, 1986 Lappert, 1973/1986 Cowley, 1983 West, 1981 Brook, 1981 Sekiguchi, 2004 Bickelhaupt, 1984 Appel, 1983 Pietschnig, 2004 and many more.....

Si=C Doppelbindungen Synthese instabiler Zwischenstufen: thermisch 254 nm  CH2=CH2 photolytisch (CH3)3Si-OR thermisch 20K 300nm; 4K (Argon)

Synthese stabiler Systeme: 1) Photolyse von Acylsilanen Brook 1982

Synthese stabiler Systeme: Wiberg 1983 2) Intramolekulare Salzeliminierung

3) Sila-Peterson-Reaktion Apeloig 1996

4) Aus Acylsilanen und Basen

planar 120° 170,2 pm 176,4 pm um 16° verdrillt  360° 29Si = 144 ppm

Si=Si Doppelbindungen anthracene Peddle and Roark 1972 West 1981 Synthese stabiler Systeme: Methode 1: Photolyse von Trisilanen T > 175°C Mes O2

R = -CH(SiMe3)2; -Si(i-pr3); SiMe(i-pr)2 Methode 2: Photolyse von Cyclotrisilanen (t-Bu)2SiCl2 Li/C10H8 Methode 3: Reduktion von 1,2-Dihalogendisilanen R = -CH(SiMe3)2; -Si(i-pr3); SiMe(i-pr)2 Methode 4: Aufbau aus Monosilanen durch „klassische“ Salzeliminierung

Tokitoh 2008 ΔE1/2 = 0.19 V indicates significant coupling between the two ferrocenylgroups through the Si=Si π bond

„Klassische“ Mehrfachbindungen

d(SiSi) = 247.2 pm;  = 42.6° NPr-i2 i-Pr2N  = 18° d(SiSi) = 214.3 pm  "Nicht klassische" Doppelbindung: Wechselwirkung zweier Singulettbausteine; 2 σ Donorbindungen anstatt σ und π Bindung

CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell Es+p CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell

CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell Es+p 2 DES-T - 2EST< E+ CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell

CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell Es+p 2 DES-T + 2EST< E+ 2EST> E+ CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell

CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell Es+p 2 DES-T + 2EST< E+ 2EST> E+ EST> E+ CMGT (Carter-Goddard-Malrieu-Trinquier)-Modell

leuchtend gelb 29Si = 63.7 ppm blassgelb 29Si = 90 ppm leuchtend gelb 29Si = 63.7 ppm N(SiMe3)2 (SiMe3)2N orange-rot 29Si = 49.4 ppm 29Si = 90 ppm 29Si = 94.7 ppm

außerdem: therm. Spaltung Oxidation E/Z-Isomerisierung

O d(SiSi) = 222.7 pm; Si = 360°

Weidenbruch 1997 Kira 1996, 1999

rot (max= 584nm) 29Si = 157ppm (Si2); 195 ppm (Si1,3) Kira 2003 rot (max= 584nm) 29Si = 157ppm (Si2); 195 ppm (Si1,3)

Wiberg 1985 Bickelhaupt 1984

29Si = 167 ppm 29Si = 216 ppm 29Si = 227 ppm Okazaki 1994 Kira 2007

Wiberg 2002 Sekiguchi 2006

Kira 2009 Scheschkewitz 2004 d(Si=Si = 219.2pm; C1Si1Si2 = 107.6°; Li1Si1Si2 = 131.7°; C1Si1Li1 = 119.0°; d29Si = 100.5, 94.5 ppm

Scheschkewitz 2010 ΔE1/2 = 0.21 V

Sekiguchi 2011 Sekiguchi 2011

29Si = 170 ppm ν(Si-O) = 1157 cm-1 Filipou 2014

POLYSILYLENE (POLYSILANE)  Organopolysilanes  linear und branched chains SinR2n+2 n < ~ 40000  monocyclic systems (SiR2)n n = 3 - ~ 40  polycyclic systems, cages functional groups  Higher silicon halides und higher silicon hydrides  SinX2n+2 n = 3 - 6; cyclo-(SiX2)n n = 4 - 6; high polymers (SiX2)n; (SiX)n  SinH2n+2 n = 3 - 15; cyclo-(SiH2)n n = 5, 6; high polymers (SiH2)n; (SiH)n organopolysilane backbone polysilanes are compounds containing the silicon-silicon bond

Metallorganische Chemie der 4. Hauptgruppe Elektronegativitätsdifferenz E-C energetisch passende leere Orbitale verfügbar

Si-C- Bindungsspaltung Si-C-Bindungen sind nucleophil und elektrophil spaltbar Reaktivität hängt vom Substrat und von den Substituenten am Si ab

Elektrophile Substitution von ungesättigten organischen Gruppen an Si - Et3SiNu

Elektrophile Substitution von gesättigten organischen Gruppen

Si-X- Bindungsspaltung hypervalent transition states  silicon is coordinatively unsaturated  nucleophilic substitution at Si occurs much more facile Chlorosilanes are valuable precursors Chlorosilanes, aminosilanes and silyl ethers hydrolytically unstable Polysilanes unstable under basic conditions

HOW DIFFERENT ARE SILICON AND CARBON?  Si-Si- and Si-H-bonds are weak   D0 (kJ·mol-1) d (pm) C-H 411 109 Si-H 318 148 C-C 346 154 Si-Si 222 235 higher silicon hydrides thermodynamically unstable

HOW DIFFERENT ARE SILICON AND CARBON?  the polarity of the Si-H bond is reversed  H is a good leaving group  silicon hydrides are easily oxidized and often pyrophoric in air   Electro- negativity (Pauling) H 2.2 C 2.55 Si 1.9 silanes react readily with H2O and O2 silicon hydrides are pyrophoric in air and unstable upon storage in glass vessels

HOW DIFFERENT ARE SILICON AND CARBON?  multiple bonds to silicon are weak, while certain single bonds Si-X (X = O, Cl, F...) are unusually strong

BONDING IN POLYSILANES bprim bvic bgem sp3-hybrid orbitals s-delocalization H. A. Fogarty, D. L. Casher, R. Imhof, T. Schepers, D. W. Rooklin, J.Michl, Pure Appl. Chem. 75 (2003), 999-1020

  polysilanes exhibit absorption maxima in the near UV 50 100 150 200 1350 225 275 300 250 chain length n max  linear compounds somehow behave like polyenes Me(SiMe2)nMe max [nm] n = 2 198 n = 3 215 n = 4 235 n = 5 250 n = 6 260 n = 7 266 n = 8 272 n =  310

• = SiMe2  cyclopolysilanes resemble aromatic hydrocarbons * transition * transition • = SiMe2 R. West, E. Carberry, Science 189 (1975), 179

R. West et.al., J. Am. Chem. Soc. 95 (1973) 6824 charge-transfer complex purple, max = 507nm R. West et.al., J. Am. Chem. Soc. 95 (1973) 6824 blue radical anion, electron delocalization over the whole polysilane ring radical cation, electron delocalization over the whole polysilane ring R. West et. al., J. Am. Chem. Soc. 91 (1969) 5446 J. Am. Chem. Soc. 101 (1979) 7667

ionization energy [eV] polysilanes exhibit pronounced substituent effects (--hyperconjugation) max [nm] () Me3SiSiMe3 198 (8000) PhMe2SiSiMe3 231 (11000) PhMe2SiSiMe2Ph 236 (18000) Ph3SiSiPh3 246 (32000) 8.35 s + (Si-Si) 8.69 (Si-Si) 9.07 as ionization energy [eV] 9.25 (e1g) SiMe2  SiMe3 s- hyper-conjugation 10.03 s - (Si-Si) SiMe2  SiMe3 X s-n hyper-conjugation

polysilanes exhibit pronounced substituent effects (-n-hyperconjugation) max [nm] () Si4Me8 302 (250) Si4Cl8 394 (50) Si4Br8 403 (50) Si4I8 424 (75) 300 400 500 absorption wavelength [nm] 394 303 E. Hengge, H. Stüger, Mh. Chem. 119 (1988) 873 R. West et.al., Angew. Chem. Int. Ed. 37 (1998) 1441 photochemical activity

256 nm 269 nm 290 nm  (SiSi)  n (O) conjugation First absorption maxima are red shifted in siloxy derivatives 290 nm solvent: C6H12; c = 1104 M H. Stüger, G. Fürpass, K. Renger, Organometallics 24 (2005) 6374

bright yellow luminescent solid  some polysilanes exhibit room temperature photoluminescence 465 (C6H14) 520 (CH2Cl2) 530 (C3H7OH) c = 105 M; ex = 350 nm bright yellow luminescent solid H. Stüger, K. Renger, unpublished results Me11Si6-Ph: em (C6H12)= 340 nm Ph-CH=C(CN)2: non luminecent

 polysilanes exhibit properties with technological potential starting materials for Si/N-, Si/C- or metal silicide ceramics or fibers; near UV photoresists; photo and charge conducting materials, emissive layers in integrated circuits etc.  properties may be tuned by variation of backbone structure and/or substituents Yajima et.al., (1976) -silicon carbide (PhMeSi)n; (hexylMeSi)n are soluble, meltable; can be used without prepyrolysis West et.al., (1982)

(Si-Si-bond formation) POLYSILANE SYNTHESIS (Si-Si-bond formation)  Reductive coupling of halosilanes (Wurtz type coupling)  Dehydropolymerisation Kat = cp2MCl2/BuLi (M = Ti, Zr)

(Si-Si-bond formation) POLYSILANE SYNTHESIS (Si-Si-bond formation)  Salt elimination  only applicable to the synthesis of organopolysilanes; very poor tolerance to functional groups

POLYSILANE SYNTHESIS (Functionalization)  Halogenation of Organopolysilanes e. g. by electrophilic cleavage of Si-aryl or Si-alkyl-bonds  Nucleophilic substitution of Si-X (Cl) bonds  functional polysilane derivatives

Me2SiCl2 +

Higher Silicon Hydrides | Synthesis Hydrolysis of Metal Silicides reasonable yield in a semi-technical scale (80 kg Mg2Si afford 2.8 l crude silane / day) large amounts of salt (200 kg MgCl2 from 80 kg Mg2Si) complex product mixtures tedious synthetic procedure Fehér, F.; Schinkitz, F. D.; Schaaf, J. Z. anorg. allgem. Chem. 1971, 383, 303 Universität Frankfurt, 11. November 2015

Silicon Hydrides | Synthesis Hydrolysis of Metal Silicides identified by GC up to n = 15 separated by distillation and prep. GC up to n = 8 isolated and characterized by NMR up to n = 7 Hahn, J. Z. Naturforsch. 1980, 35b, 282 Universität Frankfurt, 11. November 2015

Silicon Hydrides | Synthesis gas in/out electrode cooling fluid from Monosilane technical production of di- and trisilane problem: formation of considerable amounts of solid SinHm Spanier, E. J.; MacDiarmid, A. G. Inorg. Chem. 1962, 1, 432 Gokhale, S. D.; Drake, J. E.; Jolly, W. L. J. Inorg. Nucl. Chem. 1965, 27, 1911 Akhtar, M. Synth. React. Inorg. Metal-Org. Chem. 1986, 16, 729 Universität Frankfurt, 11. November 2015

colorless pyrophoric liquid; overall yield < 50% Silicon Hydrides | Synthesis CPS colorless pyrophoric liquid; overall yield < 50% Hengge, E.; Bauer, G. Angew. Chem. 1973, 85, 304

colorless pyrophoric liquid; overall yield up to 80% Silicon Hydrides | Synthesis CHS colorless pyrophoric liquid; overall yield up to 80% Choi, S. B;. Kim, B. K.; Boudjouk, P.; Grier, D. G. J. Am. Chem. Soc. 2001, 123, 8117. Elangoyan, A.; Anderson, K.; Boudjouk, P.; Schulz, D. L. 2011 WO 2011/094191 Tillmann, J.; Meyer, L.; Schweizer, J. I.; Bolte, M.; Lerner, H.- W.; Wagner, M.; Holthausen, M. C. Chem. Eur. J. 2014, 20, 9234. Tillmann, J.; Moxter, M.; Bolte, M.; Lerner, H. W.; Wagner, M. Inorg. Chem. 2015, 54, 9611

CPS, CHS and NPS easily available in large quantities Silicon Hydrides | Synthesis NPS colorless pyrophoric liquid; overall yield < 10% Kaczmarczyk, A.; Millard, M.; Nuss, J.W.; Urry, G. J. Inorg. Nucl. Chem., 1964, 26, 421 Höfler, F.; Jannach, R. Inorg. Nucl. Chem. Letters 1973, 9, 723 Cannady, J. P.; Zhou, X. 2008, WO/2008/051328 Wieber, S.; Trocha, M.; Patz, M.; Rauleder, H.; Müh, E.; Stüger, H.; Walkner, C. 2009 DE 10 2009 053804 CPS, CHS and NPS easily available in large quantities

Silicon Hydrides | Functionalization H.Stüger, J. Organomet. Chem. 1992, 433,11 H.Stüger, P.Lassacher, Mh. Chem. 1994, 125, 615 H.Stüger, P.Lassacher, Organosilicon Chem.2, Verlag Chemie 1998, 121

Silicon Hydrides | Functionalization formation of mono- and dichlorotrisilane no decomposition products such as SiH4, SiH3CI, Si2H6 or Si2H5CI E.A.V. Ebsworth et. al., Inorg. Nucl. Chem. Lett. 1971, 7, 1077 J.E.Drake et. al., J. Chem. Soc. A 1971, 3305

Silicon Hydrides | Functionalization colorless liquid; b.p. = 36 - 38°C (0.01 mbar) 1H: 4.85 ppm (s, ClH2Si). 29Si:  24.61 ppm (ClH2Si), 1JHSi = 239.6 Hz;  124.91 (Si4Si), 2JHSi = 12.6 Hz chlorination of Si5H12 with 4 equivalents of SnCl4 affords (ClH2Si)4Si 1H-NMR-spectrum of (H3Si)4Si + 4 SnCl4 after 48 h crystal structure of (ClH2Si)4Si at 150 K d(Si-Si) = 234.6pm; d(Si-Cl) = 207.4pm (Si-Si-Si) = 109.4°; (Cl-Si-Si) = 108.7°

Silicon Hydrides | Functionalization C. Marschner, Eur. J. Inorg. Chem. 1998, 221. F. Feher, M. Krancher, Z. Naturforsch. B, 1985, 1301.

Silicon Hydrides | Functionalization yellow-orange solution; decomposes at r.t. within several hours NMR data consistent with literature S. Wieber, H. Stueger, C. Walkner, DE 102010028170.0-44 no detectable side products works also with LiOtBu, LiN(iPr2)2 and MeLi works also in Et2O, DME, Diglyme

facile synthesis of NPS derivatives in multigram quantities Silicon Hydrides | Functionalization F. Feher, R. Freund, Inorg. Nucl. Chem. Lett., 1973, 9, 937. W. Sundermeyer, H. Oberhammer et al., Z. Naturforsch. B, 1985, 1301. facile synthesis of NPS derivatives in multigram quantities

Silicon Hydrides | Application application of higher silanes as precursor materials for liquid phase Si-film deposition in electronics industry ("printed electronics") (thin film transistor, flexible large area displays, photovoltaics etc.) processing from liquid sources desired property: decomposition prior to evaporation Shimoda, T.; Matsuki, Y.; Furusawa, M.; Aoki, T.; Yudasaka, I.; Tanaka, H.; Iwasawa, H.; Wang, D.; Miyasaka, M.; Takeuchi, Y. Nature 2006, 440, 783 Han, S.; Dai, X.; Loy, P.; Lovaasen, J.; Huether, J.; Hoey, J. M.; Wagner, A.; Sandstrom, J.; Bunzow, D.; Swenson, O. F.; Akhatov, I. S.; Schulz, D. L. J. Non-Cryst. Solids 2008, 354, 2623. Sontheimer, T.; Amkreutz, D.; Schulz, K.; Wöbkenberg, P. H.; Guenther, C.; Bakumov, V.; Erz, J.; Mader, C.; Traut, S.; Ruske, F.; Moshe Weizman, M.; Schnegg, A.; Patz, M.; Trocha, M.; Wunnicke, O.; Rech, B. Adv. Mater. Interfaces 2014, 1300046.