2.1 ESTUDIOS TOPOGRÁFICOS
2.1.1. Trabajos de Campo
5.4.1 Preparation of 1,2,4,5-tetrakis(dipheny!phosphino)benzene (TPPB)^^®.
Lithium shavings (5.29 g, 760 mmol) were added to a stirred solution of PPhg (100 g, 380 mmol) in THF (400 ml) at room temperature. This mixture was stirred overnight , after which the lithium shavings had dissolved completely to give a deep re solution. A water - cooled reflux condenser was fitted to the apparatus , and 1,2,4,5-Tetrafluorobenzene (14.3 g, 95 mmol) added to the mixture. A rapid decolouration occurred, with evolution of heat. The mixture was left to stir overnight. H^O (150 ml) was added, the resultant white solid was collected by filtration and was with H^O (2 x 100 ml) Recrystallisation from CHjClj / MeOH yielded TPPB as a white crystalline solid (41.80 g, 54%).
Anal, found: 0: 79.60; H: 5.20; P: 15.20
Calc, for C5 2H4 2P4: C: 79.35; H: 5.27; P: 15.13 %
^'P nmr (C D C y ô 1 4 .2 (s)
IR (KBr) (cm-') Ar-H: 3067 (s),3047 (s), 3013 (m), 2999 (m); Ar: 1583(s); 5adj Ar-H 743 (s), 694 (s); P-Ph: 1436 (s), 1432 (s); other bands: 1570 (m), 1480 (s), 1384 (m), 1326 (m), 1306 (m). 1271 (m), 1180 (m), 1090 (s). 1026 (s), 999 (s), 916 (m), 910 (m), 853 (m), 842 (m)
5.4.2 Synthesis of Transition Metai Dimers Bridged by TPPB.
[{Cr(C0)J}2{p-n'-n'-TPPB}] (4.1)
[Cr(CO)gCI][Et^N] (1.05g, 2.9 mmol) and TPPB (1.18g, 1.45 mmol) were stirred in THF (50ml) for 12 hours. Volatiles were removed under reduced pressure the mixture was washed with petrols (3 x 30 ml), yielding a yellow solid. Recrystallisation by slow diffusion of methanol in a CH2CI2 solution gave 4.1 as
yellow octahedral crystals (1.65g, 58%).
Anal. Found: C, 64.95; H, 4.14; P, 10.54 Calc, for: C, 65.16; H, 3.70; P, 10.84% 'H nmr (C D C y Ô 7.81 - 6.52 (m, 42H, Ph)
Chapter 5: Experimental
’ ’P nmr (C D C y 6 83.0 (s)
IR (v(CO) (C H jC y (cm-’) 2010 (m), 1927 (w), 1899 (s), 1895 (s)
[{M o (C O )jy n -ii*-ri*-T P P B }] (4.2)
TPPB (0.76g, 1.0 mmol) and [Mo(CO).,(pip)j] (0.79g, 2.0 mmol) were refluxed in THF for 30 minutes. The resultant orange solution was filtered to yield a yellow solid, which was washed with petrols (3 x 30 ml) to give 4.2 (0.87g,
68
%).Reaction of the same reactant mixture at room temperature goes to completion after 6 hours.
Anal.Found: C, 59.94; H, 3.50; P,10.43.
Calc, for CgjH^jOjP^Mo: C, 60.50; H, 3.44; P, 10.33%. ’ H nmr (CDCI3) 5 7.29-7.03 (bm)
*’P nm r(CDCy 5 58.03(s)
IR; v(CO) (C H jC y (cm’’) 20 23,1 9 3 2 ,1 9 0 6
UVA/is (C H jC y (A,^(nm).e (dm^moMcm ')) 714, e 60; 337, e 1900; 232, e 1730
Ep,=+1.09V
i m C O ) M ^ - n W - T P P B } ] (4.3)
[W(CO)Xpiperidine)j (1.0g, 0.2 mmol) and TPPB (0.87g, 0.1 mmol) were stirred in THF (60ml) for 12 hours at ambient temperature (20°C).Volatiles were removed under reduced pressure and the mixture was washed with petrols (3 x 30 ml) to give 4.3 as a yellow solid (0.92g, 61%). Recrystallisation from THF yielded yellow octahedral crystals suitable for X-ray diffraction study.
The same procedure was carried out in refluxing THF, and an IR kinetic study carried out. It was found that the reaction had gone to completion after 30 mins. Yield 0.98g, 65%. Anal. found:C, 46.77; H, 3.21; P, 8.21 Calc, for Cg2H,2 0 gP,W2'3 CH2Cl2: C, 46.99; H, 2.91; P, 7.46 'H nmr (CDCyS 7.34 - 7.06 (bm, 42H, Ph) " V nmr (C D C y Ô 43.6 (s. Jp^ = 238.5 Hz) IR v(CO) (C H jC y (cm-') 2019 (m), 1925 (m), 1901 (s)
Chapter S: Experimental
UVA/is (CH,CL) ( W n m ) ) 774, e 90; 728, e 90; 335, e 810; 233, e 8170 Ep,=+1.14V
[{IVIo(CO)4)}2{|i-Ti^-T]^-TPPB}] (4.2): Preparation by Microwave Reflux
[Mo(CO)J (1.00 g, 3.8 mmol) and TPPB (1.54 g, 1.9 mmol) in diglyme (10 ml) and THF (10 ml) were heated under reflux in a microwave oven for 30 minutes, the mixture being found to be yellow in colour. Volatiles were removed under reduced pressure, and the mixture was washed with petrols (2 x 1 2 ml).
Recrystallisation from CHgCI^ / petrol yielded 4.2 (1.01 g, 43 %).
5.4.3 fac, fac-[{M o(CO)3(PPhJ}2- p - n W - T P P B } ] (4.4)
4.2 (0.50g, 0.4 mmol) was stirred under reflux in MeCN (50 ml) for 3 days, after which IR v(CO) confirmed the presence of
[{Mo(CO)3(MeCN)}2{ii-T|^-r|^-TPPB}]. PPh^ (0.58 g, 2.2 mmol) was added and
the mixture stirred for a further 17 hours. Volatiles were removed under reduced pressure and the residue washed with petrols (2 x 30 ml). Recrystallisation from CHgClg / MeOH gave 4.4 as an orange / yellow solid (0.19 g, 28%).
Anal, found: 0, 64.60; H, 4.56; P, 10.19
Calc, for C9gH2 2 0 6PgM0 2'C H2Cl2: C, 65.30; H, 4.18; P, 10.42 %
^'P nmr (C D C y Ô 60.8 (d, Jpp 30Hz), 59.0 (d, Jpp 30Hz) Ratio 1:2 IR (v(CO)) (CH2CI2) (cm*') 1946 (s), 1859 (m)
5.4.4. Reactions o f TPPB Dimers with DPPE.
[{Cr(COXp-n^-n'-TPPB}] (4.1) with DPPE
4.1 (0.31 g, 0.27 mmol) and DPPE (0.23g, 0.58 mmol) were heated under reflux in n-decane (50 ml) for 4 hours, the mixture went orange after only 45
minutes. Volatiles were removed under reduced pressure.Recrystallisation was unsuccessful from: THF, THF / Petrol, CH2CI2 / MeOH, CHgClg / petrol, toluene,
toluene / petrol. However, the orange solid obtained was identified tentatively as [{Cr(CO)j(Ti^-DPPE)},{u-TiV-TPPB}]
Chapter 5: Experimental
" Y nmr (CDCI3) Ô 80.8 (t. Jpp 29 Hz, PPh/ir), 29.6 (t. Jpp 29 Hz,
PhzPCH^CH^PPhJ
IR: v(CO) (CH2CI2) (cm-') 1849(w), 1797(s)
[{Mo(CO)2(ti^-DPPE)}2{u-ti^-ti^-TPPB }](4.5)
4.2 (0.32g, 0.81 mmol) and DPPE (0.5g, 0.40 mmol) were heated under reflux in n-decane (150 ml) for 12 hours (the mixture went orange after only 30 mins). After allowing to cool slowly to room temperature (over 3 hours) followed by cooling in an ice bath (0°C), a filtration was carried out. The pale yellow solution was discarded, the orange solid washed with petrols (3 x 50 ml) and volatiles removed under reduced pressure. The resultant orange powder was dissolved in THF (100ml) at 50°C and allowed to cool slowly to room temperature (over 3 hours). Left at 0°C overnight, an orange microcrystalline solid was obtained, 4.5 (0.34g, 45%). The IR (CH2CI2), IR (n-decane) and ^'P nmr
suggested that a mixture of cis and trans isomers was formed. No separation was effected by column chromatography on an alumina column.
Anal, found: C, 68.34; H, 5.19; P, 12.69
Calc, for C,ioHgoO,PglVI0 2; C, 68.97; H, 4.74, P, 12.93
'H nmr (C D C y 5 7.4 - 6 . 6 (m, 82H, Ph), 2.2-2.1 (m, 8 H, CH2CH2) ^'P nmr
(CDCy 5 78.5 (dd,
p -n V -T P P B ,Jpp=
19,88
Hz),68.8 (d,
^-tiV - T P P B ,Jpp=
19 Hz), 66.0 (m, p -n W -T P P B ),55.5 (dd,
ti^-DPPE,Jpp=
19,88
Hz),55.3 (dd,
f-D P P E ,Jpp=
19 Hz),45.7
(m, ti^-DPPE) IR: v(CO) (CH2CI2) (cm-') 1854(w), 1819(s), 1800(m, sh) (n-decane) (cm ') 1873(m), 1826(s), 1816(s) [{W(CO)2(ti"-DPPE)}2{p-ti^-t1^-TPPB}](4.6)4.3 (0.55g, 0.29 mmol) and DPPE (0.24g, 0.60 mmol) were heated under reflux in n-decane (100 ml) for 3 days, the mixture went dark orange. After allowing to cool slowly to room temperature (over 3 hours) followed by cooling in an ice bath (0 °C), a filtration was carried out. The pale yellow solution was discarded, the orange / red solid washed with petrols (3 x 50 ml) and volatiles
Chapter 5: Experimental
dissolved in THF (100 ml) at 50 °C and allowed to cool slowly to room temperature (over 3 hours). Left at 0 °C overnight, an orange / red solid was obtained, 4.6 (0.48g, 39%). IR (CH^Cy and nmr suggested that a mixture of c/s and trans isomers was formed. No separation was effected by column chromatography on an alumina column. No X-ray diffraction quality crystals were obtained from: THF, CH^CIg / MeOH or CHgCI^ / petrol.
Anal, found: C, 63.71; H, 4.45, P, 12.84
Calc, for Ci.oHgqO.PgWg: C, 63.17; H, 4.34; P, 11.85
'H nmr
(CDCy
Ô 8.0 - 5.8 (m, 82H, Ph), 2.2-2.0 (m, 8 H, CH^CH^) "'P nmr (C D C y Ô 58.7 (dd, p -n '-f-T P P B , Jpp=17, 85 Hz; Jp^=239 Hz), 51.2 (dd, p-tiV - T P P B , Jpp=17 Hz; Jp^=239 Hz), 50.0 (m, p -n W -T P P B ), 43.5 (dd, ti^-DPPE, Jpp=17, 85 Hz; Jp^=239 Hz), 42.7 (d, n'-DPPE, Jpp=17 Hz; Jpw=239 Hz), 42.0 (m, q^-DPPE). IR: v(CO) (C H jC y (cm*'') 1860(s), 1820 (w), 1793(m)Microwave Reflux of 4.2 with DPPE (1:2 ratio)
4.2 (0.1 Og, 0.08 mmol) and DPPE (0.1 Og, 0.24 mmol) were heated under microwave reflux in 7 ml diglyme / 7 ml THF. After 6 hours volatiles were
removed under reduced pressure to give an orange solid. IR v(CO) and ^^P nmr reveal no [{Mo(CO)2(Ti^-DPPE)}2{|i-Y-Y-TPPB }] (4.5), no product was identified.
Recrystallisation was unsuccessful from: THF, THF / Petrol, CH^CIg / MeOH, CHjClj / petrol, toluene, toluene / petrol.
^'P
nmr(CDCy
5 54.4 (s), 43.9 (s), 37.2 (s), 33.9 (s), -11.9 - (-13.9) (m) IR :v(C O ) (CH^Cy (cm*') 2 0 2 2 (m), 1956(w), 1909 (s), 1883(s),Chapter 5: Experimental
Microwave Reflux of [{W(COXn-n^-n'-TPPB)] (4.3) with DPPE (1:2 ratio)
4.3 (0.15g, 0.08 mmol) and DPPE (0.07g, 0.16 mmol) were heated under microwave reflux in 7 ml diglyme / 7 ml THF. There was no change in IR; v(CO)
after 4 hours. The procedure was repeated using a 9 ml diglyme / 3 ml THF