Search

A novel catalytic dehydrocoupling route for the synthesis of linear, cyclic, and polymeric phosphinoboranes has been developed. The dehydrocoupling of neat Ph2PH·BH3, which is otherwise very slow below 170 °C, is catalyzed by [{Rh(μ-Cl)(1,5-cod)}2] or [Rh(1,5-cod)2][OTf] (0.5−1 mol % Rh) to give the linear compound Ph2PH−BH2−PPh2−BH3 (1) at 90 °C, and a mixture of the cyclic trimer [Ph2P−BH2]3 (2a) and tetramer [Ph2P−BH2]4 (2b) at 120 °C. In addition, the catalytic potential of other (e.g., Ti, Ru, Rh, Ir, Pd, Pt) complexes toward the dehydrocoupling of Ph2PH·BH3 was investigated and was in many cases demonstrated. The molecular structures of 1 and 2b, and of the primary phosphine−borane adduct PhPH2·BH3, were determined by single-crystal X-ray analysis. The dehydrogenative coupling of PhPH2·BH3 gave low-molecular-weight poly(phenylphosphinoborane) [PhPH−BH2]n (3) when performed in toluene (110 °C) with ca. 0.5 mol % [Rh(1,5-cod)2][OTf] as catalyst. The absolute weight-average molecular weight was determi...

An advanced process for the synthesis of polyphosphazenes with controlled architectures has been investigated. By this method, a wide range of well-defined phosphazene di- and triblock copolymers with controlled molecular weights and narrow polydispersities have been synthesized (Mn up to 4.8 × 104 with polydispersities of 1.06−1.39). The diblock copolymers, {[NPCl2]n[NPR(R‘)]m}, were synthesized by the cationic condensation polymerization of the phosphoranimines, PhCl2PNSiMe3, Me(Et)ClPNSiMe3, Me2ClPNSiMe3, Ph2ClPNSiMe3, and PhF2PNSiMe3, at 35 °C initiated from the “living” end unit of poly(dichlorophosphazene), [Cl−(PCl2N)n-PCl3+PCl6-] which was itself formed by the polymerization of Cl3PNSiMe3 with small amounts of PCl5 initiator in CH2Cl2 at 25 °C. Halogen replacement reactions through the use of NaOCH2CF3 and/or NaOCH2CH2OCH2CH2OCH3 on the diblock copolymers yielded fully organo-substituted macromolecules. In addition, the diblock copolymer {[NPMe(Et)]n[NPMe(Ph)]m} was formed by the block copolymeriz...

A new polyphosphazene, [N=PPh(CF 3 )] n , has been prepared via the PCl 5 -induced cationic polymerization of Me 3 SiN=P(CF 3 )(Ph)Br. In addition, the cationic route has been used to produce [N= PPh(Me)] n with controlled molecular weights and narrow polydispersities. By contrast, the new monomer Me 3 SiN=P(t-Bu)(Ph)F failed to polymerize under any conditions but was used as an initiator and terminator to prepare both mono- and ditelechelic polymers. This monomer was also used to prepare [F(Ph)(t-Bu)P=N(PCl 2 =N)P(t-Bu)(Ph)F] + , which was used as a substrate for reactions with alkoxy and aryloxy groups to yield the hydrolytically stable materials, [R(Ph)(t-Bu)P=N(PR 2 =N)P(t-Bu)(Ph)R 2 ].

Three types of polyphosphazenes with different architectures have been synthesized and characterized. The influence of the polymer architecture on solid ionic conductivity was of particular interest. The first type includes linear oligo- and polyphosphazenes with the general formula [NP(OCH2CH2OCH2CH2OCH3)2]n (MEEP) with different chain lengths. The second type consists of a series of triarmed star-branched polyphosphazenes with the general formula N{CH2CH2NH(CF3CH2O)2P[NP(OCH2CH2OCH2CH2OCH3)2]n}3 with different arm lengths. These were synthesized via the reaction of the tridentate initiator [N{CH2CH2NH(CF3CH2O)2PN−PCl3+}3][PCl6-]3 with the phosphoranimine Cl3PNSiMe3 in CH2Cl2 followed by halogen replacement with sodium (methoxyethoxy)ethoxide. The molecular weights in this system were carefully controlled by variation of the monomer-to-initiator ratios, and the effect of polymer molecular weight on solid ionic conductivity was examined. The third polymer system was designed to examine the effect of compl...

A new, ambient-temperature method for the direct synthesis of organo-substituted polyphosphazenes is described. It involves the initiation of a series of organophosphoranimines R(R‘)XPNSiMe3 (3, R = Ph, R‘ = X = Cl; 5, R = R‘ = Ph, X = Cl; 7, R = Me, R‘ = Et, X = Cl; 9, R = R‘ = CF3CH2O, X = Br) with catalytic amounts of PCl5 in CH2Cl2 to yield (after treatment with NaOCH2CF3 in the case of 3) the corresponding polyphosphazene species (NPRR‘)n (4, R = Ph, R‘ = OCH2CF3; 6, R = R‘ = Ph; 8, R = Me, R‘ = Et; 10, R = R‘ = OCH2CF3) with narrow polydispersities. The molecular weights of the polyphosphazenes were controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. For monomers 7 and 9 optimum polymerization behavior was found to occur at 35 °C in the absence of solvent in the presence of catalytic quantities of PCl5. These reactions proceeded to 1...

A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described. It involves the initiation of Cl3PNSiMe3 with small amounts of PCl5 in CH2Cl2 to yield poly(dichlorophosphazene), (NPCl2)n, with narrow polydispersities. The molecular weight of poly(dichlorophosphazene) was controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. Integration of 1H and 31P NMR spectra of these reactions revealed that the polymerization follows first-order reaction kinetics with respect to monomer concentration. Active polymer chains may be quenched or end-capped by the addition of trace quantities of Me2(CF3CH2O)PNSiMe3 or (CF3CH2O)3PNSiMe3. Furthermore, PBr5, SbCl5, and Ph3C[PF6] were also found to be effective initiators in CH2Cl2 at room temperature.

A tetramethylethylene bridged ferrocene 1 and cobaltocene 3 are synthesised in two steps from 2-tert-butyl-6,6-dimethylfluvene. Both can be oxidised to the corresponding cations, 2 and 4, the single-crystal X-ray structures of which have been determined.

A series of novel [2]ferrocenophanes with unsymmetrical C-E bridges has been prepared in which the covalent radius of the second-row element, E, and hence the ring strain present is varied. Species [Fe(eta-C(5)Me(4))(eta-C(5)H(4))CH(2)ER(x)] (7, ER(x) = SiMe(2); 8a, ER(x) = PPh; 8b, ER(x) = PMes; 9, ER(x) = S) were synthesized via reaction of the PMDETA (N,N,N',N' ',N' '-pentamethyldiethylenetriamine) adduct of [(eta-C(5)H(4)Li)Fe(eta-C(5)Me(4))CH(2)Li] with Cl(2)ER(x) (E = Si or P) or S(SO(2)Ph)(2). Studies of 7-9 by single-crystal X-ray diffraction confirmed the presence of ring-tilted structures: for 7, alpha (angle between the planes of the Cp rings) = 11.8(1) degrees; for 8a, alpha(average) = 14.9(3) degrees; for 8b, alpha(average) = 18.2(2) degrees; and for 9, alpha = 18.5(1) degrees. The least tilted compound, 7, was found to be resistant to thermal, anionic, and transition metal catalyzed ROP. In contrast, the significantly more tilted compounds 8a, 8b, and 9 were all found to polymerize thermally with small negative values of DeltaH(ROP) of ca. 10-20 kJ.mol(-1) determined by DSC. Whereas thermal ROP of 8a yielded the soluble high molecular weight polycarbophosphaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PPh](n) (11), species 9 formed the insoluble polycarbothiaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n) (14). Attempted anionic ROP of 8a and 9 with (n)BuLi was unsuccessful and treatment of 8a with CF(3)SO(3)Me resulted in the formation of the novel phosphonium salt [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PMePh][CF(3)SO(3)] (13), which was found to be resistant to thermal ROP as a result of its less strained structure (for 13, alpha = 11.4(7) degrees ). Treatment of 9 with CF(3)SO(3)Me or BF(3).Et(2)O resulted in the first example of cationic ROP for a transition metal-containing heterocycle to yield polycarbothiaferrocene 14. In the presence of excess 2,6-di-tert-butylpyridine as a selective proton trap, ROP of 9 was only observed with CF(3)SO(3)Me, and not BF(3).Et(2)O, which indicated that Me(+) and H(+) are the probable cationic initiators, respectively. Thermal copolymerization of 9 with trimethylene sulfide resulted in the isolation of the soluble, high molecular weight, random copolymer [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n)[(CH(2))(3)S](m), 15.

The ring-opening polymerization of strained, ring-tilted [n]ferrocenophanes (n = 1, 2) represents a new and versatile route to well-defined, soluble and high molecular weight polymers containing skeletal iron atoms. This paper will focus on our efforts to extend this work to species containing different transition metals such as ruthenium.