Please use this identifier to cite or link to this item: http://hdl.handle.net/1783.1/2032

Synthesis, chemical and catalytic properties of transition metal complexes with polydentate phosphine ligands

Authors Lee, Hon-man
Issue Date 1997
Summary The linear chiral triphosphine ligand (S,S)-PhP(CH2C*HMeCH2PPh2)2, ttp*, was synthesized by the reaction of (S)-Ph2PCH2CHMeCH2Cl and PhPH2 in the presence of LDA. Treatment of [RhCl(COD)]2 with ttp* produced RhCl(ttp*). Reaction of RuCl2(PPh3)3 or RuCl2(DMSO)4 with ttp* gave RuCl,(ttp*). Reaction of CoCl2 with ttp* in methanol gave CoCl2(ttp*). Treatment of RhCl(ttp*) and RuCl2(ttp*) with NaBH4 led to Rh(BH4)(ttp*) and RuH(η2-BH4)(ttp*) respectively. The tripodal chiral triphosphine ligand (R)-Ph2PCH2CH(PPh2)CH2CH2PPh2, etp* was synthesized by the reaction of (S)-MsOCH2CH(OMs)CH2CH2OMs with KPPh2. Reaction of RuCl2(DMSO)4 and etp* gave RuCl(etp*). A series of ruthenium complexes with the orthometallated ligand [2,6- (PhP2CH2)2C6H3]- (PCP) were synthesized. Reaction of RuCl2(PPh3)3 with 1,3-(Ph2PCH2)2C6H4 produced the coordinatively unsaturated complex RuCl(PPh3)(PCP), which was characterized by X-ray crystallography. Treatment of RuCl(PPh3)(PCP) with 4-phenylpyridine (pyph) yielded RuCl(pyph)(PPh3)(PCP). Treatment of RuCl(PPh3)(PCP) with PMe3 and CO generated RuCl(PMe3)2(PCP) and RuCl(CO)2(PCP), respectively. Reactions of RuCl(PPh3)(PCP) with NaH in THF and NaBH4 in methanol gave RuH(PPh3)(PCP) and RuH(CO)(PPh3)(PCP), respectively. The hydride complex RuH(PMe3)2(PCP) was prepared by the reaction of RuCl(PMe3)2(PCP) with NaBH4. Reaction of RuCl(PPh3)(PCP) with NaBH4 in THF produced an orange compound which can be formulated as a BH3 complex RuH(BH3)(PPh3)(PCP) (A). RuH(BH3)(PPh3)(PCP) (A) isomerized to RuH(BH3)(PPh3)(PCP) (B) in solution. Treatment of RuH(BH3)(PPh3)(PCP) (A) with CO produced a mixture of RuH(CO)(PPh3)(PCP) and RuH(CO)2(PCP). Reaction of RuH(BH3)(PPh3)(PCP) (A) with PMe3 gave RuH(PMe3)(PPh3)(PCP). Treatment of RuH(BH3)(PPh3)(PCP) (B) with CO and PMe3 led to RuH(CO)(PPh3)(PCP) and RuH(PMe3)(PPh3)(PCP) respectively. Reactions of RuCl(PPh3)(PCP) (PCP = 2,6-(PPh2CH2)2C6H3) with PhC[is equivalent to]CH and HC[is equivalent to]CC(OH)Ph2 gave the unusual coupling products RuCl(PPh3)(η4-PhCH=C-2,6-(PPh2CH2)2C6H3) and RuCl(PPh3)(η4- Ph2C(OH)CH=C-2,6-(PPh2CH2)2C6H3), respectively. RuCl(PPh3)(η4-PhCH=C-2,6-( PPh2CH2)2C6H3) was characterized by X-ray crystallography. Dehydration was observed in the coupling reactions of RuCl(PPh3)(PCP) with HC[is equivalent to]CC(OH)PhMe and HC[is equivalent to]C-cyclo-C6H10(OH). Thus the coupling products RuCl(PPh3)(η4-CH2=CPhCH=C-2,6-(PPh2CH2)2C6H3) and RuCl(PPh3)(η4-cyclo-C6H9-CH=C-2,6-(PPh2CH2)2C6H3) were obtained from the reactions of RuCl(PPh3)(PCP) with HC[is equivalent to]CC(OH)PhMe and HC[is equivalent to]C-cyclo-C6H10( OH), respectively. Treatment of [Ru(PMe3)2(PCP)]BF4 with PhC[is equivalent to]CH produced [Ru(PMe3)2(η4-PhCH=C-2,6-(PPh2CH2)2C6H3)]BF4. Reaction of RuCl(PPh3)(PCP) with PhC[is equivalent to]CLi gave Ru(C[is equivalent to]CPh)(PPh3)(PCP). Protonation of this acetylide complex in the presence of Cl- produced the coupling product RuCl(PPh3)(η4-PhCH=C-2,6-(PPh2CH2)2C6H3) along with some uncharacterized species. Treatment of RuCl2(PPh3)3 with PMP (PMP=2,6-(Ph2PCH2)2C5H3N) in acetone produced RuCl2(PPh3)(PMP) which has been characterized by X-ray diffraction. Treatment of RuCl2(PPh3)(PMP) with NaBH4 in methanol gave RuHCl(PPh3)(PMP), acidification of which with HBF4.Et2O produced the molecular dihydrogen complex [RuCl(H2)(PPh3)(PMP)]BF4. Treatment of RuHCl(CO)(PPh3)3 with PMP in benzene produced RuHCl(CO)(PMP) which reacted with HBF4.Et2O to give the molecular dihydrogen complex [RuCl(H2)(CO)(PMP)]BF4. The osmium molecular dihydrogen complex [OsCl(H2)(PPh3)(PMP)]BF4 was prepared by protonation of OsHCl(PPh3)(PMP) with HBF4.Et2O. Relative acidities of the dihydrogen complexes were investigated by NMR spectroscopy of equilibration reactions conducted in CD2Cl2.[RuCl(H2)(CO)(PMP)]BF4 is more acidic than [RuCl(H2)(PPh3)(PMP)]BF4 which is in turn more acidic than its osmium analog [OsCl(H2)(PPh3)(PMP)]BF4. The catalytic properties of RuH(η2-BH4)(ttp), RuCl2(ttp), RhCl(ttp*), RuCl(PPh3)(PCP) and RuCl2(PPh3)(PMP) for hydrogenation of styrene have been tested. RuH(η2-BH4)(ttp) and RuCl(PPh3)(PCP) are very efficient catalysts and quantitative yield of ethylbenzene was obtained in 20 min. RuCl2(PPh3)(PMP) has a relatively poor activity. The catalytic properties of RuCl2(ttp*), RhCl(ttp*), Rh(BH4)(ttp*), RuH(η2-BH4)(ttp*) and RuCl2(etp*) for the asymmetric hydrogenation of α-acetamidocinnamic acid have been tested. RuCl2(ttp*), RhCl(ttp*), Rh(BH4)(ttp*) and RuH(η2-BH4)(ttp*) are efficient catalysts and quantitative production of N-acetyl-(S)-phenylalanine could be obtained after 24 hrs. However, the optical yield is moderate and in the range of 2-50%. The catalytic properties of RuCl2(ttp*), RuCl2(etp*), RuCl2(pigiphos), RuCl2(PPh3)3 and RuCl(PPh3)(PCP) for cyclopropanation were investigated using styrene and ethyl diazoacetate as the substrates. The yields for cyclopropanation products are relatively low and the major products are diethyl fumarate and diethyl maleate. The cis/trans ratio for the cyclopropanation product is moderate and the optical yields for the reactions are low. Reaction of RuCl2(ttp*) with ethyl diazoacetate produced RuCl2(ttp*)(=CHCO2Et), which in reactions with ethyl diazoacetate and styrene produced the dimerization and cyclopropanation products respectively.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 1997
Subjects
Language English
Format Thesis
Access
Files in this item:
File Description Size Format
th_redirect.html 339 B HTML