Synthesis and characterisation of the platinum complexes [PtCl(CClPAr)(PPh3)2] and [PtCl(CClPAr′)(PPh3)2] as potential intermediates in the preparation of phosphaalkynes
“…The molecular structures of phosphaalkenes 1b , E - 1e , and E - 1f are shown in Figures − 3, respectively. Important metricalparameters for 1b , E - 1e , and E - 1f are tabulated in Table and, for comparison, the metrical parameters are also provided for the closely related phosphaalkenes 1a , 11h, E -MesPCPh(2- i PrC 6 H 4 ), MesPC(4-BrC 6 H 4 )(4-MeOC 6 H 4 ), and 1d 1 Molecular structure of MesPC(4-FC 6 H 4 ) 2 ( 1b ).…”
Section: Resultsmentioning
confidence: 99%
“…Several important methods for preparing isolable acyclic phosphaalkenes are shown in Scheme . A considerable amount of research has led to the development of the following general synthetic routes to compounds with PC bonds: the Becker condensation followed by 1,3-silatropic rearrangement ( A ), base- or thermally induced 1,2-elimination ( B ), , condensation followed by elimination ( C 12 and D 13 ), phospha-Wittig reactions ( E ), R−P transfer from metal−phosphinidenes ( F ), , and double-bond migration reactions ( G ). , 1 Examples of Synthetic Methods Developed for the Preparation of Acyclic Phosphaalkenes…”
Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.
“…The molecular structures of phosphaalkenes 1b , E - 1e , and E - 1f are shown in Figures − 3, respectively. Important metricalparameters for 1b , E - 1e , and E - 1f are tabulated in Table and, for comparison, the metrical parameters are also provided for the closely related phosphaalkenes 1a , 11h, E -MesPCPh(2- i PrC 6 H 4 ), MesPC(4-BrC 6 H 4 )(4-MeOC 6 H 4 ), and 1d 1 Molecular structure of MesPC(4-FC 6 H 4 ) 2 ( 1b ).…”
Section: Resultsmentioning
confidence: 99%
“…Several important methods for preparing isolable acyclic phosphaalkenes are shown in Scheme . A considerable amount of research has led to the development of the following general synthetic routes to compounds with PC bonds: the Becker condensation followed by 1,3-silatropic rearrangement ( A ), base- or thermally induced 1,2-elimination ( B ), , condensation followed by elimination ( C 12 and D 13 ), phospha-Wittig reactions ( E ), R−P transfer from metal−phosphinidenes ( F ), , and double-bond migration reactions ( G ). , 1 Examples of Synthetic Methods Developed for the Preparation of Acyclic Phosphaalkenes…”
Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.
“…106 The synthesis of the phosphaalkenes ArPQCCl 2 (Ar = 2,6-CF 3 -4-R-C 6 H 2 ; R = H or CF 3 ) has been described. 107 Reaction of these species with Pt(PPh 3 ) 4 resulted in a C-Cl activation reaction and the formation of cis-[PtCl(ClCQPAr)(PPh 3 ) 2 ]. The synthesis of the first examples of Z 3 -1,2-diphosphaallyl complexes has been reported.…”
Section: Reaction Of the Terminal Phosphido Complex [Na(thf)mentioning
This chapter reviews the literature reported during 2005 on the chemistry of nitrogen, phosphorus, arsenic, antimony and bismuth.
PreambleOnce again the study of the chemistry of the pnictogens has provided considerable challenges to both synthetic and theoretical chemists. Significant new advances and insights into have been made, of particular note are the developments in the areas of activation of dinitrogen, such as the work of Schrock on molybdenum complexes 1,2 and the discovery of an amido-hydride complex from activation of ammonia. 3 Further highlights include the continued expansion of the use of metal phosphinidene complexes as synthetic reagents for the production of novel phosphoruscontaining materials and the synthesis of several new cationic arsenic-containing species.As in previous years and due to space restrictions this review will not, in general, consider the use of the trivalent elements as ligands, however reviews on ''user friendly'' primary phosphines 4 and how to evaluate the net donor abilities of phosphines 5 have appeared.
NitrogenThe activation of dinitrogen remains a major area of interest. The molybdenumcentred reduction of dinitrogen to ammonia remains one of the most impressive methods of nitrogen fixation and a review on this subject has appeared 1 as has a comprehensive study into several aspects of this chemistry. 2 It has been shown that under an atmosphere of N 2 , the dimer [Ta(Z 5 -C 5 Me 4 R)] 2 (m-Cl) 4 (R = Me, Et) disproportionates to give [Ta(Z 5 -C 5 Me 4 R)] 2 (m-Z 1 ,Z 1 -N 2 ) as the nitrogen-containing product. 6 The dinitrogen may be considered to have undergone a four-electron reduction with the tantalum now existing in the (V) oxidation state. In a similar fashion, reduction of [Ti(Z 5 -C 5 Me 5 )Cl 3 ] in the presence of substituted fulvene gives rise to dinuclear species containing a (m-Z 1 , Z 1 -N 2 ) ligand. 7 The reduction of the zirconium complex [NPN]ZrCl 2 (thf) [NPN = PhP(CH 2 SiMe 2 NPh) 2 ] under nitrogen results in the formation of [NPN]Zr(m-Z 2 , Z 2 -N 2 )(thf). 8 A similar reaction with the titanium analogue results in the insertion of dinitrogen into the Ti-PPh bond and formation of 1. Using a related ligand set within the coordination sphere of tantalum, Fryzuk has also shown that it is possible to convert hydrazine to bridging Ta-NH-Ta groups. 9 A reaction of the same precursor with Me 2 NNH 2 results in the formation of a complex containing a bridging nitride ligand. The oxidative addition
“…Once considered exotic, phosphaalkenes now constitute a widely studied branch of phosphorus chemistry. A wide variety of synthetic methods are available to make P=C bonds, including: (a) the phospha‐Wittig reaction, (b) phospha‐variants of Peterson olefination, (c) 1,2‐elimination reactions,, (d) the Becker condensation reaction, and others. [4b]…”
A facile synthetic methodology is reported that permits access to the backbone (Et 2 N) 2 P-substituted thiazol-2-thione 2 [(Et 2 N) 2 P-THS Me ; THS Me = 3-methylthiazol-2-thione-5-yl]. Starting from 2, Et 2 N(Cl)P-substituted thiazol-2-thione 3 [Et 2 N(Cl)P-THS Me ] was formed using chloride scrambling with PCl 3 . Subsequently, nucleophilic substitution using Ph 2 CHLi afforded [Et 2 N(Ph 2 CH)P-THS Me ] (4) which, via reaction with PCl 3 , afforded [Ph 2 CHP(Cl)THS Me ] (5). Conversion of 4 into phosphaalkene [Ph 2 C=P-THS Me ] (6) was achieved, but its thermal instability precluded isolation. Complex [κP-W(CO) 5 {Ph 2 CH(Cl)P}-THS Me ] (7) was then synthesized and used to access end-on [a] 1697 Scheme 1. Synthetic methodology designed for the synthesis of phosphaalkene 6 starting from C 5 -phosphanyl-thiazol-2-thione 2.
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