Preparation and Structures

Preparation and Structure.—A study of the reaction of phosphorinans (75) with elemental halogens has revealed the formation of three types of product in solution. For the phosphonium salt species (76), the counterion is sometimes a tri- 

1-Adamantyltetrafluorophosphorane (23) cannot be prepared from the phos-phonyl difluoride (77) by treatment with sulphur tetrafluoride. Instead, it has been prepared in good yield by Lewis-acid-induced cleavage of 1-fluoroadamantane the first time this has been achieved with an alkyl fluoride.  

Preparative uses of the reactions of phosphorus pentachloride (78) with simple phosphines have been investigated. Thus tertiary phosphines give mainly the chlorophosphonium salts (79), whilst chlorophosphines give chlorophosphoranes (80 = 1 or 2). An impressive combination of n.m.r. and C1 n.q.r. spectroscopy has revealed that the phosphoranes (80) are molecular in the solid state, and that the phosphoranes (81) and (82) are ionic in the solid state.  

Two recent papers have been devoted to studies of perfluoropinacolylphosphor-anes. Thus details of further methods of preparation of the phosphoranes (83) have appeared, and AG for positional exchange has been found to be greater for 

R = H than for = alkyl or silyl. The conclusions reached as a result of earlier studies of intramolecular exchanges in the phosphoranes (84) have been confirmed by a study of n.m.r. spectra of (84). ° 

Preparation and Structure.—Two new routes to the relatively rare tetra-alkylfluorophosphoranes (50) from salt-free ylides have been reported. These phosphoranes all have considerable fluoride character (no HCPF coupling), although the tributyl derivative (50 R = Bu) is quite stable and definitely monomeric. Difluorophosphorane (51) has been prepared from excess hydrogen fluoride and diphosphine, and found to disproportionate readily to trifluorophosphorane (52). The infrared spectrum of (51) indicates symmetry, which is accounted for by a 

An elegant and stimulating MO analysis of the problems of bonding and structure in phosphoranes has appeared. Of particular relevance to the current topic is a discussion of the interactions of the lone pairs of donor substituents with the orbitals on phosphorus. The authors conclude that donor substituents will prefer equatorial sites (except where electronegativity becomes the dominating influence, as with fluorine), and moreover, that the highest occupied donor orbital will prefer to lie in the equatorial plane of the phosphorane, rather than in the axial plane, i.e. (65) is preferred over (66). Although only limited experimental data are available, it would appear that these predictions are fully supported, e.g. the preferred conformation of (67) and the features of the phosphoranes (59) and (61), 

Sokal skii, O. G. Strukov, and S. Z. Ivin, Zhur. obshchei Khim., 

Bis(trifluoromethyl) peroxide and disulphide have been used in a novel preparation of the difluorophosphoranes (68) from tertiary phosphines. The phosphetan derivative (69), prepared by this route, has been shown to exist as a mixture of two isomers at —100 °C, one of which has a 

The exchange reactions between fluorophosphoranes and silane derivatives have been utilized for the fluorination of alcohols, via their trimethylsilyl ethers (89). According to one of these reports, the alkyl fluoride is generally accompanied by olefin. Phosphorus penta-fluoride similarly fluorinates siloxanes such as (90).  

1 Preparation and Structure. - The structure of triphenylphosphine benzyli-dene 1 has been reported. The PhaP CHPh molecules associate as pairs through the formation of weak intermolecular C-H. .. C hydrogen bonds between the ortho-H atom of the benzylidene group of one molecule and the carbanion-carbon of the other. 

Organophosphorus Chemistry, Volume 29 The Royal Society of Chemistry, 1999 

Density functional theory has been used to calculate the P-E bond energies and orbital populations of trimethylphosphine chalcogenides and related compounds. The results indicate that Me3P=CH2 has a 7i-bond order of 0.5. The equilibrium acidities in DMSO solution and gas-phase homolytic bond dissociation energies of tributylphosphonium ylide precursors have also been determined.  

High-spin cation radicals 2 and 3 can be obtained by oxidation of the parent methylene phosphoranes. Dication radical 2 has a triplet state as evidenced from a AMs = 2 ESR transition exhibiting hyperfine coupling to two identical phosphorus nuclei. The trication radical 3 possesses a quartet state with D - 262 MHz and E = 0 MHz and exhibits a AA/s = 3 ESR transition. The archetypal methylene phosphorane H3P CH2 has been investigated in the gas phase using ion cyclotron resonance mass spectrometry.  

A new route to so-called instant ylides has been reported. These are obtained from powder mixtures of alkyltriphenylphosphonium salts and potassium hydride in a 1 1 mole ratio. Addition of tert-butylmethyl ether results in the generation of the triphenylphosphino-alkanide. These simple phosphonium salt/ KH mixtures are said to offer little advantage over sodium amide based instant ylides. However, those containing hetero-substituted phosphonium salts have a much longer shelf life than their sodium amide counterparts. 

1 Preparation and Structure. - The equilibrium acidities and homolytic bond dissociation energies of a number of alkyltriphenylphosphonium salts (1) and the oxidation potentials of the corresponding ylides have been determined. The triphenylphosphonium substituent lowers the pKa value of the a-hydrogens by approximately 25 units (142 kJmol ) while the effect of the corresponding triphenylarsonium substituent is some 4 pKa units less. 

The unstable triethoxyphosphoranes (2) have been generated by the reaction of oxalylcarbamates with triethyl phosphite. Reaction of (2) in situ with bromo-trimethylsilane or hydrogen bromide in acetic acid gave the corresponding phosphonates (3) in high yield and so provides a new and most convenient route to the synthetically useful amino(diethoxyphosphoryl)-acetic esters (4) (Schone 

Trimethoxyphosphoranes (6) are among the products reported in new examples of reactions of the carbene intermediates (5). A re-investigation of the reaction of triphenylphosphine with isatin (7) has shown the previous reports to be incorrect and that the products are in fact the new phosphonium ylide (8) and isoindigo (9).  

A variety of cyclic phosphonium ylide structures have been reported. Hetero-cyclic and -bicyclic structures, including the ylide (11) and a variety of iminophosphoranes, are the products of the reaction of the 1,2-dihydro-1,3,2-diazaphosphinine (10) with dimethyl acetylenedicarboxylate. Attempts to prepare a simple adduct of DBN with the (phosphino)(P-chlorophosphonio) carbene (12) led instead to formation of the unsaturated tricyclic adduct (13). The diphosphete structure (14) is the product of a simple two component reaction of dichloro(bis(trimethylsilyl)methylphosphine) with DBU. Details of the synthesis, chemistry and structure of X -phosphetes (15), benzo-X, -phosphetes (16), and naphtho-X -phosphetes (17) have been reported. 2,4-Diphosphoniodihydro-phosphetide cations (19) have been prepared by condensation of the 

Lithiated iminophosphoranes, e.g. (39) and (40), have been prepared by the reaction of N-silyliminophosphoranes with n-butyllithium. In several cases the structures have been determined by X-ray analysis. 

A variety of ylides (e.g. 5) of arsenic, antimony and bismuth have been prepared under mild conditions via the reaction of diazo compounds with the appropriate three valent organometalloid. Schmidbaur s group continues to produce new ylide structures, for example (6).5 The lithiated aza-ylide (8) has been prepared directly from the parent 

1 Aldehydes.- The reactions of phosphorus ylides, PO-activated carbanions and iminophosphoranes have been incorporated into CAMEO, an interactive computer program for the mechanistic evaluation of organic reactions.8 The chemistry and synthetic applications of phosphorus and arsenic ylides and PO-stabilised carbanions have been reviewed.  

Sato has reported a new route to allylic sulphides through the reaction of a-sulphenyl aldehydes (35) with phosphonium ylides or phosphonate carbanions.25 Similar reactions have been used to achieve a two-carbon 

The new ylides (12), which decompose at room temperature, have been prepared by the reaction of fluorophosphaalkenes (11) with trimethy Iphosphine Continuing studies of ylides derived from bisphosphinomethanes have provided a variety of IX. , 3X5-diphosphole derivatives, e.g. (13)7 

The structures of a number of stabilized ylides have been studied by l C, iH, and 3ip n.m.r.H and by X-ray crystallography. 12 The X-ray crystal structures of (24) and (27) were compared to those previously determined for (25) and (26) and this data, together with that obtained from Raman and infrared studies on these and related compounds, was used to determine the extent and nature of hydrogen bonding in these systems. 

Bis(diphenylsilylated) ylides (28) 1 and the borylated phosphonium ylides (29)1 1 have been synthesized and their molecular structures determined by X-ray crystallography and, in the case of (29), these structures used to fully interpret llB, l C, and iH n.m.r. spectra. The structural parameters determined by X-ray analysis for the P-chloro ylide (30) provide convincing support for negative hyperconjugation in ylides 5 that is stabilization by the P-Cl o orbital accepting electron density from the ylide carbanion. 

A number of structural studies of iminophosphoranes have been reported. These include the product obtained from the reaction of phosphine (bisphosphine sulphide) (31) with p-tolyl azide which on the basis of its iH and iP n.m.r. exists in the C-ylide form (32) rather than as an iminophosphorane.16 Treatment of (32) with base gave the relatively stable iminophosphorane anion (33) which was isolated as a Rh(l) complex. The molecular structures of the iminophosphoranes (34),17 (35),1 and (36)19 have been determined by X-ray crystallography and their structural parameters compared with those determined for l,8-bis(dimethylamino)- 

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Co(II), Ni(n), Cu(n), and Zn(II) complexes of Schiff bases derived from 4-aryl-2-aminothiazoles and salicylaldehyde have been prepared, and structure 276 (Scheme 170) was established by magnetic susceptibility measurements and by infrared, electronic, and mass spectra (512). 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

P. F. Kelly and J. D. Woollins, The Preparation and Structure of Complexes Containing Simple Inorganic Sulfur-Nitrogen Ligands, Polyhedron, 5, 607 (1986). 

Tellurium nitride was first obtained by the reaction of TeBt4 with liquid ammonia more than 100 years ago. The empirical formula TeN was assigned to this yellow, highly insoluble and explosive substance. However, subsequent analytical data indicated the composition is Tc3N4 which, in contrast to 5.6a and 5.6b, would involve tetravalent tellurium. This conclusion is supported by the recent preparation and structural determination of Te6N8(TeCl4)4 from tellurium tetrachloride and tris(trimethylsilyl)amine (Eq. 5.5). The TceNs molecule (5.12), which is a dimer of Tc3N4, forms a rhombic dodecahedron in which the... 

The thiotrithiazyl cation in [S4N3]C1 was one of the first S-N heterocycles to be prepared and structurally characterized. It is obtained as a reasonably air-stable, yellow solid by the reaction of S4N4 or [SsNaClJCl with S2CI2 in CCI4 (Eq. 5.12)." ... 

A variety of complexes of the thionyl imide anion [NSO] with both early and late transition-metal complexes have been prepared and structurally characterized. Since both ionic and covalent derivatives of this anion are readily prepared, e.g., K[NSO], McsMNSO (M = Si, Sn) or Hg(NSO)2, metathetical reactions of these reagents with transition-metal halide complexes represent the most general synthetic method for the preparation of these complexes (Eq. 7.10 and 7.11). ... 

S3N2 2] (Fig. 15.39b)) and the cyclic anion S3N3O4 , i.e. [02SNSNS(0)2b] .<27 Numerous other cyclic- and polycyclic-N/S/0 species have recently been prepared and structurally characterized. ... 

The preparation and structural characterization of the ions HX2 has been an important feature of such work/ As expected, these H-bonded ions are much less stable than Hp2 though crystalline salts of all three anions and of the mixed anions HXY (except HBrI ) have been isolated by use of large counter cations, typically Cs+ and NR4+ (R = Me, Et, Bu") — see pp. 1313-21, of ref. 23 for further details. Neutron and X-ray diffraction studies suggest that [C1-H - C1] can be either centrosymmetric or non-centrosymmetric depending on the crystalline environment. An example of the latter mode involves interatomic distances of 145 and 178 pm respectively and a bond angle of -168 (Cl- -Cl 321.2pm).( >... 

Dithiiranethione is an isomer of CS3 and its preparation and structure have been drawing much attention [75JCS(P2)559]. In the chemiionization process of CS + CS2 using the molecular beam photoionrzation method, the photoionization efficiency curve of CS3 was observed (80JCP4242). 

There is an extensive literature devoted to the preparation and structure determination of coordination compounds. Thermal analysis (Chap. 2, Sect. 4) has been widely and successfully applied in determinations [1113, 1114] of the stoichiometry and thermochemistry of the rate processes which contribute to the decompositions of these compounds. These stages may overlap and may be reversible, making non-isothermal kinetic data of dubious value (Chap. 3, Sect. 6). There is, however, a comparatively small number of detailed isothermal kinetic investigations, together with supporting microscopic and other studies, of the decomposition of coordination compounds which yields valuable mechanistic information. 

There is a wealth of information concerning preparative and structural aspects of the fluoro- and oxyfluorocomplexes of... 

Klanberg, F., Askew, W. B. Guggenberger, L. J. (1968) Preparation and structure of Co3(CO)ioBH2N(C2H5)3, a new tricobalt enneacarbonyl carbon cluster, Inorg. Chem. 7, 2265-2271. 

The synthesis, structures, and reactivity of neutral and cationic mono- and bis(guanidinato)zirconium(rV) complexes have been studied in detail. Either salt-metathesis using preformed lithium guanidinates or carbodiimide insertion of zirconium amides can be employed. Typical examples for these two main synthetic routes are illustrated in Schemes 73 and 74. Various cr-alkyl complexes and cationic species derived from these precursors have been prepared and structurally characterized. 

A unique pair of stereoisomeric dimolybdenum amidinate complexes has been prepared and structurally characterized. The reaction of Li[PhC(NSiMe3)2] with dimolybdenum tetraacetate afforded trans- and ds-Mo2(02CMe)2[PhC (NSiMe3)2]2- While the acetates coordinate to the M02 core via a bridging mode in both compounds, the benzamidinates are bridging in the trans complex and... 

Consequently, sulfur dissolves in polysulfide solutions much faster than in equimolar monosulfide solutions [73]. In this context it is of interest that the analogous decaselenium dianion Scio has been prepared and structurally characterized in solid [PPN]2Seio [74]. This anion is however bi-cyclic. 

The BaBPOs compound was first prepared and structurally characterized by Bauer [12]. Figure 21.2 shows the crystal structure of BaBPOs. Its structure is similar to all stillwellite-like compounds with the space group P322. Its main structural elements are spiral tetrahedral chains [001] built of three-membered rings. The contact between the BO4 tetrahedra that form the central part of these chains are reinforced by PO4 tetrahedra and thus [BPO5] heterotetrahedral chain complexes are produced. 

A. Preparation and Structure.—-A study of the i.r. and Raman spectra of t-butyltetrafluorophosphorane (34 n = 1) has indicated that it is a trigonal bipyramid with the t-butyl group equatorial. The preparation... 

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