The phosphoryl compound (O:)P(TMG) 3 (TMG = N’,N’,N”,N”-tetramethylguanidyl) (6) was synthesized during attempts to obtain the potentially very basic (but still unknown) compound P(TMG) 3 (1). Its reaction with HCl resulted in the triply protonated species 7. The crystal structure of compound 7 was determined; it crystallizes as a bis-dichloromethane solvate. Each protonated nitrogen forms a hydrogen bond to one chloride. A series of protonation experiments was conducted in order to test the behaviour of 6 towards weak acids.

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The nature of the products from the reaction of TrtPH(2) (1) with an equimolar amount of phosgene strongly depends on the solvent. The initial intermediate 2 was isolated from toluene, but lost CO in dichloromethane, and HCl in diethyl ether, yielding TrtP(H)Cl (3), and (TrtPCO)(2) (4b), respectively. TrtP(H)CI (3) was found to be a halophosphine of amazing stability. Treatment of 3 with excess phosgene led to partial substitution of the P-bonded proton for C(:O)Cl with formation of 5, which did not eliminate CO to give TrtPCl(2). Substitution of chlorine in TrtP(H)CI (3) for fluorine or bromine furnished the halophosphines, 6 and 7. Minute quantities of the diphosphene 8 were formed upon treatment of 3 with NEt3 or DBU. The course of the reaction between the secondary phosphines Trt(R)PH and phosgene depends on the group R. If R was t-Bu, formation of a mixture of Trt(t-Bu)PCl (10), and t-BuPCl2 (resulting from partial cleavage of the P-C-bond) was observed. Although in the case of R = Ph, the intermediate 12 could be isolated, at elevated temperature HCl was eliminated from 12, giving Trt(Ph)PCl (13). The diphosphine (TrtPH)(2) (14) is inert towards HCl-free phosgene. In the presence of HCl the P-P-bond in 14 was cleaved, and upon chlorination of the resulting TrtPH(2) (1) by phosgene, TrtP(H)Cl (3) was obtained as the only phosphorus-containing product.

Treatment of solutions of the halophosphines TrtP(H)F (Trt = trityl, Ph3C) 1a and TrtP(H)Cl 1b with equimolar amounts of TOB (tetrachloro-orthobenzoquinone) led to the formation of mixtures of products. They contained the phosphoranes 2a and 2b, which were formed by oxidation with TOB and are in equilibrium with the phosphines 3a and 3b. Moreover, the trityl phosphonite 4, which was formed by dehydrohalogenation of 2a, 2b and 3a, 3b, was observed in both mixtures. The dehydrohalogenation was found to be reversible in the case of HF. The pure compounds 4 and 5 were obtained from the reaction of TrtPCl2 with tetrachlorocatechol 4 and by the oxidation of 1a and 1b with two equivalents of TOB. Because of its importance in this reaction sequence, an X-ray crystal structure determination was carried out on 4. The P–O bond lengths of 168.4(2) and 167.7(2) pm are probably to be attributed to a bond-lengthening effect of the chlorine atoms of the quinone. As a comparison with analogous systems reveals, the phosphorane 5 is an example of a σ5λ5(P) species in which the phosphorus atom exhibits square-pyramidal coordination. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 277–280, 1999

The trifluorophosphoranes TrtRPF(3) (R = tert.-Bu (1), Ph (2), NEt2 (3)) were obtained by the oxidative addition of TrtF (Trt = triphenylmethyl) to the difluorophosphines RPF2. At room temperature only 1 exhibited dynamic behaviour in solution, but at -5 degrees C the pseudorotation was slow enough to permit the differentiation of (1)J(PFax) and (1)J(PFeq) by P-31 NMR spectroscopy. X-ray structure analyses of 1, 2, and 3 confirm the expected trigonal bipyramidal geometry at phosphorus, with axial fluorine substituents. The trifluorophosphorane 1-3 are of such stability towards water that hydrolysis was effected only under vigorous, basic conditions. The action of HCl or HBr on Trt(NEt2)PF3 (3) led, in a complex reaction, to the formation of TrtPF(4) (5), besides 3 and PF3. As first observed for 1 by NMR spectroscopy at elevated temperature, in the case of 1 and 2 an equilibrium exists between TrtRPF(3) and TrtF/RPF2. Accordingly, it was possible to trap TrtF or RPF2 by addition of I-2, PCl3, AlCl3, and tetrachloro-o-benzoquinone (TOB) to Solutions of 1 or 2. 3 was unreactive towards I-2 and PCl3, whereas treatment with AlCl3 caused formation of (Et2N)PCl2 by cleavage of the P-C bond, and halogen exchange. If a mixture of toluene and ether was used, LiAlH4 reduced 1 and 2 to the corresponding secondary phosphines 8 and 9, while if only diethyl ether was employed under the same conditions, P-C bond rupture occurred in 2, and a mixture of PhPH2 and TrtH was obtained.

As the first diphospha-urea with P-bonded protons, [TrtP(H)](2)C = O (3) was found to be of amazing stability, which is thought to be due to the presence of the triphenylmethyl groups. Unlike known cyclic or non-cyclic analogues, 3 showed next to no tendency to eliminate carbon monoxide. 3 was obtained by reaction of the dimeric phospha-isocyanate (TrtPCO)(2) (1) with LiAlH4, in which the intermediary phosphaalkene 2 was observed. Caused by its two asymmetric phosphorus atoms, 3 appeared as a mixture of two isomers, meso-3 and rac-3 (ratio: 20:1). Theoretical considerations, and the analysis of the proton-coupled P-31 NMR spectrum (spin system: AA'XX'), allowed the assignment of the signals to the two isomers. The action of anhydrous hydrogen chloride on 3 led to the cleavage of one P-C(:O)-bond, and formation of an equimolar mixture of TrtPH(2) (5) and TrtP(H)C(:O)Cl (6). Cleavage of a P-C(:O)-bond in 3 was also observed in its reaction with tetramethylguanidine (TMG) or ammonia. As proved by P-31 NMR spectroscopy in the case of TMG, the reaction proceeded via the phosphaalkene intermediate 8. Acting as nucleophiles, TMG and ammonia substituted TrtP(H) in 3, and the P,N-ureas 9 and 10, with TrtPH(2) (5) as a side product, were obtained.

The products formed in the systems Ph3CPH(:O)X/Ph3CP(Y)Cl/NEt3 with X = F, H, OH and Y = Cl, H, TMG (= N,N,N',N'-tetramethylguanidinyl) are discussed. Ln the case of the systems X=F/Y=Cl, X=F/Y=H, and X=Y=H the diphosphine monoxides 4a, 5a and 13a were formed, while in the case of X=H/Y=Cl, instead of the expected diphosphine monoxide 14, a mixture of 13 a and of the POP compound 16 (molar ratio ca. 2:1) was observed. Treatment of 4 a with N,N,N',N'-tetramethylguanidine (= HTMG) led to the diphosphine monoxide, 7a whereas its tautomer 7b was formed, when Ph3CP(TMG)Cl 6 reacted with Ph3CPH(:O)F 1. The conversion of one tautomer, 7a or 7b, into the other was not observed. On the other hand Cl2P-PCPh3(:O)F 8 a, formed as an intermediate in the reaction of 4a with PCl5, spontaneously rearranged to give Ph3CPClF 9 and P(:O)Cl-3 as the final products. Surprisingly, oxidation of the sigma(3)(P)-atom in 4a, 5a and 13a was impossible with H2O2.(O:)C(NH2)(2) as the oxidizing agent. The diphosphite 19 showed no rearrangement to the tautomeric diphosphine dioxide 18, but oxidation to 20 was possible. All the products containing two asymmetrically substituted phosphorus atoms were obtained as diastereomeric mixtures of the meso and racemic form, as proved by P-31 NMR spectroscopy.

The phosphorus-carbon bond in various P-triphenylmethyl-substituted phosphorus compounds of simple as well as more complex structure can be cleaved selectively by treatment with Lewis acids, halogens (or halogen transfer agents), and hydrogen halides. The course of the reaction can be followed easily by NMR spectroscopy, in certain cases this P-C-bond cleavage can be used as a synthetic principle for phosphorus difluorohalides, F(2)PHal (Hal = Cl, Br, Fl. In the presence of the appropiate structural elements, cleavage of P-P-bonds or rearrangements are observed.

Triphenylmethyl fluoride 1 will effect chlorine–fluorine exchange in certain phosphorus chlorides. Exchange of chlorine for fluorine was observed only in σ3λ3 (P)- and σ5λ5 (P)-compounds, while phosphorus oxychloride as an example of a σ4λ5 (P)-compound was unreactive towards 1.

The E- and Z-isomers (1a,1b) of 1,2-bis(fluorodimethylsilyl)-1,2-diphenylethene have been investigated by 1H, 13C and 19F NMR spectroscopy, mass spectrometry and single crystal X-ray structure analysis. The NMR spectra of both compounds were markedly different, caused by the non-equivalence of all methyl groups and through non-bonding F–F interactions (through-space coupling) in isomer 1b. X-ray investigations reveal a widening of the CC-Si angles at the expense of Si–C–Ph; the CC bond of the Z-isomer is lengthened to 135.4(2) pm.

Treatment of triphenylmethyldichlorophosphine 1 with aluminium trichloride in the presence of tert-buty1 chloride leads, after hydrolysis, with high selectivity to di-tert-butylphosphinic chloride 5. The reaction is suggested to proceed via a chlorophosphinidene intermediate which is trapped by the alkyl chloride.

The dependence of the protolytic decomposition rate of phosphorus amides on the substituents at phosphorus is decribed. On treatment with HCl, the N',N',N",N"-tetramethylguanidine(= TMG)-substituted sigma(4)(P) compounds 5 and 9 formed salts that were protonated at the imino nitrogen atoms and were completely stable in the solid state, and surprisingly stable in solution. Even with a large excess of HCl, only the imino nitrogen atom underwent protonation, with formation of HCl2- as a counter anion, without cleavage of the P-N bond. The basicity of the imino nitrogen atom also protected sigma(3)(P) species from electrophilic attack, and the ionic compounds 12, 14, and 20c were formed, providing examples of the first stable sigma(3)(P) amides with one or two protonated P-N bonds. Such unusual stability is associated with steric protection by the Ph3C (= trityl) group and charge delocalization over the TMG-moiety. In contrast, MeP(TMG)(2) was unstable towards HCl, whereas treatment with HSbF6 led to the phosphonium salt 24, where protonation had occurred at phosphorus. The same result was obtained when triphenylmethylphosphonous dichloride 1 was allowed to react with 3 equivalents of HTMG, forming the stable phosphonium salt 19, soluble in water, which was converted to the bicationic species 20c upon treatment with HCl. - The basicity of the tritylated phosphorus compounds was found to increase in the order 5 < 2 < 19 < 13 < HTMG < 21; the basic centre is the phosphorus atom in 21 and the imino nitrogen atom in all other compounds. The fluorinating agent Et3N . 3 HF caused rapid conversion of compound 6 to 25, the nucleophilic attack of fluoride ion at phosphorus could not be prevented by the stabilizing effects mentioned. - All compounds were investigated by H-1- and P-31-NMR spectroscopy. The crystal structures of compounds 5, Ph3CP(=O)-(H)TMG,and 6, [5 . 2 HCl], were determined; 6 is protonated at the imino nitrogen, leading to a longer P-N bond [5: 161.6(2), 6: 168.7(2) pm], and the counterion is HCl2-. In the structure of 20c, [Ph3CP(TMG)(2)] . 3 HCl, the cation is protonated at both imino N atoms and the counterions are Cl- and HCl2- (one of each).

While the secondary phosphines (1-Ad) 2 PH (1) (l-Ad = adamantyl) and Trt(Ph)PH (2) (Trt = triphenylmethyl) reacted readily with trifluoroacetic anhydride (TFAA) to give the trifluoroacetylphosphines 7 and 8 . (1-Ad) 2 P(:O)H (6) could not be converted into the corresponding trifluoroacetylphosphine oxide 10 by treatment with TFAA. Compound 10 was observed by 19 F and 31 P NMR spectroscopy in the reaction of (1-Ad) 2 PC(:O)CF 3 (7) with (H 2 N) 2 C(:O) · H 2 O 2 . Two pathways were observed for the reaction of 1 with excess hexa-fluoroacetone (HFA), starting from the primary HFA adduct (1-Ad) 2 PC(CF 3 ) 2 OH (13) . Oxidation of 13 led to the tertiary phosphine oxide 14 which was also available from (1-Ad) 2 P(:O)H (6) and HFA. Isomerization of 13 gave (1-Ad) 2 POCH(CF 3 ) 2 (15) whose oxidation with excess HFA furnished the phosphorane 16 . Hydrolysis of 16 led to the phosphinic ester 17 . As is known for Ph 2 PH (3) , Ph(C 6 F 5 )PH (4) reacted with HFA to give the α-hydroxyphosphine 19 . No reaction was observed when Trt(Ph)PH (2) and (C 6 F 5 ) 2 PH (5) were treated with HFA.

The dihalophosphines TrtPX(2) (X = Cl:2, Br:3) were obtained in the reaction of TrtP(:O)(H)OH 1 with PCl3 and PBr3, respectively. 2 could also be synthesized from TrtMgCl and PCL(3), 3 from 2/Me(3)SiBr. TrtPF(2) 4 was prepared by the fluorination of 2 with NaF or from TrtLi/PF2Cl. The reduction of 2 with LiAlH4 or HSiCl3/NaOH(aq) yielded TrtPH(2) 6, the reaction with NaF/H2O led to TrtP(:O)(H)F 9. (TrtPCl(2))(2)Mo(CO)(4) 10 was observed in the system 2/(NOR)Mo(CO)(4) by P-31-NMR-spektroscopy. 4 was oxidized with TrtN(3) or sulfur to give the lambda(4)P(V)-compounds TrtP(:NTrt)F-2 11 and TrtP(:S)F-2 12 respectively. Whereas the oxidation of 4 and (1)BuPF(2) with tetrachloro-o-benzoquinone (TOB) led to the corresponding difluorophosphoranes 13 and 14, no reaction could be observed when 4 was treated with hexafluoroacetone (HFA) at elevated temperatures. In a fashion typical of difluorophosphines, 4 reacted with (COD)MCl(2) (M = Pd, Pt) or (NOR)Mo(CO)(4) to give the co-ordination compounds 15, 16 and 18a. Upon heating cis(TrtPF(2))(2)Mo(CO)(4) 18a isomerized to give the thermodynamically favoured trans-complex 18 b. The reaction of 4 with Fe-3(CO)(1) led to (TrtPF(2))Fe(CO)(4) 17 as the only phosphorus-containing product, instead of the phosphinidene complex TrtP(mu-F)(2)Fe-3(CO)(9). X-ray structure analyses of compounds 2 and 12 were carried out. The P-C bond in 2 is unusually long (193.3 pm). The F-P-F angle in 12 is narrow (98.14 degrees).

The synthesis of the triphenylmethyl-phosphonic and -phosphonothioic dihalides Ph3CP(:X)Y2 (X = O, S; Y = F, Cl) is described. The NMR parameters of these compounds are discussed and compared to these of other phosphonic and thiophosphonic dihalides. Single crystal X-ray analysis was used to confirm the structure of Ph3CP(:O)F2 2 [C2/c, a = 1599.6(4), b = 1096.3(3), c = 1863.1(7) pm, beta = 109.11(2)-degrees, T = 178 K, R = 0.0341. The geometry at the phosphorus atom is approximately tetrahedral. The bonds between phosphorus and fluorine are extremely short [P-F 153.1(1) and 153.3(1) pm]. Bond distances and angles for this compound are compared to those of methylphosphonic difluoride which were obtained from microwave spectra.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The synthesis of the triphenylmethyl-phosphonic and -phosphonothioic dihalides Ph 3 CP(:X)Y 2 (X=O, S; Y=F, Cl) is described. The NMR parameters of these compounds are discussed and compared to these of other phosphonic and thiophosphonic dihalides. Single crystal X-ray analysis was used to confirm the structure of Ph 3 CP(:O)F 2 2 [C2/c, a=1599.6(4), b=1096,3(3), c=1863.1(7) pm, β=109.1 1(2) o , T=178 K, R=0.034]. The geometry at the phosphorus atom is approximately tetrahedral. The bonds between phosphorus and fluorine are extremely short [P-F 153.1(1) and 153.3(1) pm]

The synthesis of the triphenylmethyl-phosphonic and -phosphonothioic dihalides Ph3CP(:X)Y2 (X = O, S; Y = F, Cl) is described. The NMR parameters of these compounds are discussed and compared to these of other phosphonic and thiophosphonic dihalides. Single crystal X-ray analysis was used to confirm the structure of Ph3CP(:O)F2 2 [C2/c, a = 1599.6(4), b = 1096.3(3), c = 1863.1(7) pm, ß = 109.11(2)°, T = 178 K, R = 0.034]. The geometry at the phosphorus atom is approximately tetrahedral. The bonds between phosphorus and fluorine are extremely short [P— F 153.1(1) and 153.3(1) pm]. Bond distances and angles for this compound are compared to those of methylphosphonic difluoride which were obtained from microwave spectra.