Straightforward Solvent‐Free Synthesis of Tertiary Phosphine Chalcogenides from Secondary Phosphines,Electron‐Rich Alkenes,and Elemental Sulfur or Selenium

A series of tertiary phosphine sulfides and selenides have been synthesized in excellent yields (88‐99%) via a three‐component reaction between secondary phosphines, electron‐rich alkenes (styrene, vinyl chalcogenides), and elemental sulfur or selenium, proceeding under solvent‐free conditions (80‐82°C, 4–44 h). The interaction occurs via initial oxidation of secondary phosphines with elemental sulfur or selenium followed by noncatalyzed anti‐Markovnikov addition of the generated R₂P(E)H (E = S, Se) species to alkenes to afford the corresponding adducts with high chemo‐ and regioselectivity.     

A cyclic selenium‐based reversible addition‐fragmentation chain transfer agent mediated polymerization of vinyl acetate

A cyclic selenium‐based reversible addition‐fragmentation chain transfer (RAFT) agent, 5,5‐dimethyl‐3‐phenyl‐2‐selenoxo‐1,3‐selenazolidin‐4‐one (RAFT‐Se), was synthesized and utilized in the RAFT polymerizations of vinyl acetate (VAc). Its analog, 5,5‐dimethyl‐3‐phenyl‐2‐thioxothiazolidin‐4‐one (RAFT‐S), was also used in RAFT polymerizations for comparison under identical conditions. The RAFT polymerizations of VAc with RAFT‐Se were moderately controlled evidenced by the increase of molecular weights with conversion, despite the slightly high M_w/M_n (less than 1.90), whereas the molecular weights were poorly controlled in the presence of RAFT‐S (2.00 < M_w/M_n < 2.30). Thanks to its unusual cyclic structure of RAFT‐Se, one or more RAFT‐Se species was incorporated into the resultant poly(VAc) as revealed by the results of cleavage of polymer and atomic absorption spectroscopy. Considering the biorelated functions of both poly(VAc) and Se element, this work undoubtedly provided a successful methodology of how to incorporate high content of Se into a molecular weight controlled poly(VAc). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Simultaneous arsenic‐ and selenium‐specific detection of the dimethyldiselenoarsinate anion by high‐performance liquid chromatography–inductively coupled plasma atomic emission spectrometry

The seleno‐bis (S‐glutathionyl) arsinium ion, [(GS)₂AsSe]^?, which can be synthesized from arsenite, selenite and glutathione (GSH) at physiological pH, fundamentally links the mammalian metabolism of arsenite with that of selenite and is potentially involved in the chronic toxicity/carcinogenicity of inorganic arsenic. A mammalian metabolite of inorganic arsenic, dimethylarsinic acid, reacts with selenite and GSH in a similar manner to form the dimethyldiselenoarsinate anion, [(CH₃)₂As(Se)₂]^?. Since dimethylarsinic acid is an environmentally abundant arsenic compound that could interfere with the mammalian metabolism of the essential trace element selenium via the in vivo formation of [(CH₃)₂As(Se)₂]^?, a chromatographic method was developed to rapidly identify this compound in aqueous samples. Using an inductively coupled plasma atomic emission spectrometer (ICP‐AES) as the simultaneous arsenic‐ and selenium‐specific detector, the chromatographic retention behaviour of [(CH₃)₂As(Se)₂]^? was investigated on styrene–divinylbenzene‐based high‐performance liquid chromatography (HPLC) columns. With a Hamilton PRP‐1 column as the stationary phase (250 × 4.1 mm ID, equipped with a guard column) and a phosphate‐buffered saline buffer (0.01 mol dm^?3, pH 7.4) as the mobile phase, [(CH₃)₂As(Se)₂]^? was identified in the column effluent according to its arsenic:selenium molar ratio of 1 : 2. With this stationary phase/mobile phase combination, [(CH₃)₂As(Se)₂]^? was baseline‐separated from arsenite, selenite, dimethylarsinate, methylarsonate and low molecular weight thiols (GSH, oxidized GSH) that are frequently encountered in biological samples. Thus, the HPLC–ICP‐AES method developed should be useful for rapid identification and quantification of [(CH₃)₂As(Se)₂]^? in biological fluids. Copyright © 2003 John Wiley & Sons, Ltd.     

P‐Aminophosphaalkenes with C‐Isopropyldimethylsilyl Groups

Amination of the C‐isopropyldimethylsilyl P‐chlorophosphaalkene (iPrMe₂Si)₂C=PCl ( 1 ) leads to the P‐aminophosphaalkenes (iPrMe₂Si)₂C=PN(R)R′ (R, R′ = Me ( 2 ), R = H, R′ = nPr ( 3 ), R = H, R′ = iPr ( 4 ), R = H, R′ = tBu ( 5 ), R = H, R′ = 1‐Ada ( 6 ), R = H, R′ = CPh₃ ( 7 ), R = H, R′ = Ph ( 8 ), R = H, RR′ = 2,6‐iPr₂Ph (= DIP) ( 10 ), R = H, R′ = 2,4,6‐Me₃Ph (= Mes) ( 11 ), R = H, R′ = 2,4,6‐tBu₃Ph (= Mes*)] ( 12 ), R = H, R′ = SiMe₃ ( 13 ), and R, R′ = SiMe₂Ph (1 4 ). ³¹P‐NMR spectra confirm that phosphaalkenes 2 – 7 and 10 – 14 are monomeric in solution; the structures of 7 , 10 , and 12 were determined by X‐ray crystallography. Freshly prepared (iPrMe₂Si)₂C=PN(H)Ph ( 8 ) is a monomer that dimerizes with (N→C) proton migration within several hours to the stable diazadiphosphetidine [(iPrMe₂Si)₂CHPNPh]₂ ( 9 ). NMR‐scale reactions of deprotonated 5 and 13 with tBuiPrPCl provide by P–P bond formation the P‐phosphanyl iminophosphoranes [(iPrMe₂Si)₂C=](RN=)PPtBu(iPr) [R = tBu ( 15 ), R = Me₃Si ( 17 )]. Deprotonated 5 and Me₃GeCl deliver by N–Ge bond formation the aminophosphaalkene (iPrMe₂Si)₂C=PN(tBu)GeMe₃ ( 20 ), which with elemental selenium 5 undergoes (N→C) proton migration to form the alkyl(imino)(seleno)phosphorane [(iPrMe₂Si)₂CH](tBuN=)P=Se ( 21 ), which is a selenium‐bridged cyclic dimer in the solid state.     

Intermolecular Se···I Interactions Identified in Cu11(μ9‐Se)(μ3‐I)3[Se2P(OEt)2]6 Form a One Dimensional Polymeric Chain

The undecanuclear copper cluster Cu₁₁(μ9‐Se)(μ₃‐I)₃[Se₂P(OEt)₂]₆ 1 , has been isolated along with Cu₈(μ₈‐Se)[Se₂P(OEt)₂]₆ 2 , from the reaction of NH₄Se₂P(OEt)₂, Cu(CH₃CN)₄PF₆, and Bu₄NI in a molar ratio of 3:2:2 in diethyl ether. The molecular formulation of 1 was confirmed by elemental analysis, positive FAB mass spectrometry, multinuclear NMR (¹H, ³¹P, and ⁷⁷Se), and X‐ray diffraction. In cluster 1 eleven copper atoms adopt the geometry of a 3,3,4,4,4‐pentacapped trigonal prism with a selenium atom in the center. The coordination geometry for the central, nonacoordinated selenium atom is tricapped trigonal prismatic. In addition, the central core Cu₁₁Se is further stabilized by three iodides and six dsep ligands. Besides, weak inter‐molecular Se···I interactions (3.949–3.972 Å) are uncovered and form a one dimensional polymeric chain.     

Phenylselenenylalkanes,their adducts with the dirhodium complex Rh2(MTPA)4 and ligand exchange mechanisms in solution as studied by 1H, 13C and 77Se NMR spectroscopy

Twelve secondary phenylselenenylalkanes and ‐cycloalkanes were studied by ¹H, ¹³C and ⁷⁷Se NMR spectroscopy in the presence of the chiral dirhodium complex Rh₂[(R)‐MTPA]₄ [Rh–Rh; MTPA‐H = (R)‐(+)‐methoxytrifluoromethylphenylacetic acid, Mosher's acid]. The 1 : 1 and 2 : 1 adducts were identified in solution at low temperatures. Two different mechanisms of ligand exchange, ‘switch’ and ‘replacement,’ were characterized and their energy barriers estimated and steric congestion during the exchange transitions is discussed. Coordination‐induced shifts Δδ(⁷⁷Se) are generally negative (shielding). For menthone bis(phenylselenoacetal) (7), these values indicate that a selection of the two selenium atoms occurs showing that 7 prefers complexation at the equatorial selenium atom whereas the axial selenium atom is hardly involved. Copyright © 2003 John Wiley & Sons, Ltd.     

Major Distinctions in the Molecular and Supramolecular Structures of Selenium‐containing Organotins, (o‐MeSe‐C6H4CH2)SnPh3–nCln (n = 0, 1, 2)

The synthesis and characterization of selenium‐containing stannanes, (o‐MeSeC₆H₄CH₂)Sn(Ph)_3–nCl_n [n = 0 ( 1Se ); 1 ( 2Se ); 2 ( 3Se )], is presented. The increasing Lewis acidity at tin in the series 1Se → 2Se → 3Se is reflected in their respective solid state arrangements and supramolecular architecture by interactions of the type Se ··· Se, Sn ··· Se, and Cl ··· H–C. Overall the capacity of the selenium atom to form bidentate interactions creates geometric assemblies distinctly different to those of the oxygen and sulfur analogs.     

Intra‐ and intermolecular Se...X (X = Se,O) interactions in selenium‐containing heterocycles: 3‐benzoylimino‐5‐(morpholin‐4‐yl)‐1,2,4‐diselenazole

In the selenium‐containing heterocyclic title compound {systematic name: N‐[5‐(morpholin‐4‐yl)‐3H‐1,2,4‐diselenazol‐3‐ylidene]benzamide}, C₁₃H₁₃N₃O₂Se₂, the five‐membered 1,2,4‐diselenazole ring and the amide group form a planar unit, but the phenyl ring plane is twisted by 22.12 (19)° relative to this plane. The five consecutive N—C bond lengths are all of similar lengths [1.316 (6)–1.358 (6) Å], indicating substantial delocalization along these bonds. The Se...O distance of 2.302 (3) Å, combined with a longer than usual amide C=O bond of 2.252 (5) Å, suggest a significant interaction between the amide O atom and its adjacent Se atom. An analysis of related structures containing an Se—Se...X unit (X = Se, S, O) shows a strong correlation between the Se—Se bond length and the strength of the Se...X interaction. When X = O, the strength of the Se...O interaction also correlates with the carbonyl C=O bond length. Weak intermolecular Se...Se, Se...O, C—H...O, C—H...π and π–π interactions each serve to link the molecules into ribbons or chains, with the C—H...O motif being a double helix, while the combination of all interactions generates the overall three‐dimensional supramolecular framework.     

Metal‐induced B–H Activation. Addition of Methyl Acetylene Carboxylates to Cp*Rh‐ and Cp*Ir 16 e Halfsandwich Complexes containing a Chelating 1,2‐Dicarba‐closo‐dodecaborane‐1,2‐diselenolato Ligand

Reactions of the 16e halfsandwich complexes Cp*M[Se₂C₂(B₁₀H₁₀)] ( 5 M = Rh, 6 M = Ir) with both methyl acetylene monocarboxylate and dimethyl acetylene dicarboxylate were studied in order to obtain information on the influence of the chalcogen (selenium versus sulfur), as well as further evidence for B–H activation, ortho‐metalation and substitution of the carborane. In the case of the rhodium‐selenium complex 5 , the reaction with methyl acetylene monocarboxylate gave products which were all structurally different compared to those of the sulfur analogue of 5 : a polycyclic derivative 12 with a B(6)‐substituted carborane cage was obtained as one of the final products; in addition, both geometrical isomers containing a Rh–B bond ( 10 , 11 ) and isomers without a Rh–B bond ( 8 , 9 ) were isolated, the latter being the result of twofold insertion into one of the Rh–Se bonds. In the case of the iridium‐selenium complex 6 , the reaction with methyl acetylene monocarboxylate led to the geometrical isomers 13 and 14 (similar to 10 and 11 ) with structures possessing an Ir–B bond. Both 5 and 6 reacted with dimethyl acetylene dicarboxylate at room temperature to give the complexes 15 and 16 which are formed by addition of the C≡C unit to the metal center and insertion into one of the metal‐selenium bonds. The proposed structures in solution were deduced from NMR data (¹H, ¹¹B, ¹³C, ⁷⁷Se, ¹⁰³Rh NMR), and an X‐ray structural analysis was carried out for the rhodium complex 12 .     

Der Einfluß von Phosphoryl‐Substituenten auf die Eigenschaften P‐substituierter 2‐Methylimidazolium‐Ionen und 2‐Methylenimidazoline [1]

The Influence of Phosphoryl Substituents on the Properties of P‐Substituted 2‐Methylimidazolium Ions and 2‐Methyleneimidazolines [1] The imidazolines ImCHP(E)Ph₂ [ 6 , E = S ( a ), Se ( b )] are obtained from ImCHPPh₂ ( 4 ) and sulfur or selenium. HBF₄ reaction yields the corresponding imidazolium salts [ImCH₂P(E)Ph₂][BF₄] [ 5 , E = S ( a ), Se ( b )]. 1, 3, 4, 5‐Tetramethyl‐2‐methylenimidazoline ( 1 , ImCH₂) reacts with Ph₂P(O)Cl to give the corresponding phosphane salt [ImCH₂P(O)Ph₂]Cl ( 7 ) from which the vinyl compound ImCHP(O)Ph₂ ( 8 ) is formed through deprotonation. 8 reacts with excess HBF₄ to give the phosphine oxide BF₃ adduct [ImCH₂P(O)Ph₂ · BF₃][BF₄] ( 9 ). The crystal structures of 5a , 5b , 6b , 7 · CH₂Cl₂ and 9 · H₂O as well as preliminary data of 8 are reported and discussed on comparison with the phosphanes [ImCH₂PPh₂][BF₄] ( 3b ) and ImCHPPh₂ ( 4 ). From structural data, π‐electron delocalisation is concluded for 6b and 8 .     

Chiral‐Substrate‐Assisted Stereoselective Epoxidation Catalyzed by H2O2‐Dependent Cytochrome P450SPα

The stereoselective epoxidation of styrene was catalyzed by H₂O₂‐dependent cytochrome P450_SPα in the presence of carboxylic acids as decoy molecules. The stereoselectivity of styrene oxide could be altered by the nature of the decoy molecules. In particular, the chirality at the α‐positions of the decoy molecules induced a clear difference in the chirality of the product: (R)‐ibuprofen enhanced the formation of (S)‐styrene oxide, whereas (S)‐ibuprofen preferentially afforded (R)‐styrene oxide. The crystal structure of an (R)‐ibuprofen‐bound cytochrome P450_SPα (resolution 1.9 Å) revealed that the carboxylate group of (R)‐ibuprofen served as an acid–base catalyst to initiate the epoxidation. A docking simulation of the binding of styrene in the active site of the (R)‐ibuprofen‐bound form suggested that the orientation of the vinyl group of styrene in the active site agreed with the formation of (S)‐styrene oxide.     

1‐Phosphabicyclo[3.2.1]octane

1‐Phosphabicyclo[3.2.1]octanes 1‐Phosphabicyclo[3.2.1]octane has been obtained by free‐radical cyclization of (2‐vinyl‐4‐pentenyl)‐phosphane in the presence of AIBN. Another approach to 1‐phosphabicyclo[3.2.1]octanes involves free‐radical cyclization of 2‐methyl‐4‐(2‐propenyl)‐phospholane synthesized by the reaction of [2‐(2‐propenyl)‐4‐pentenyl]‐phosphane with KPH₂/[18]crown‐6 in THF. The bicyclic phosphanes are characterized by reactions with CS₂, selenium, sulfur, NO, CH₃I, and HSO₃F, respectively, structural and analytical data as well as ¹H, ¹³C, ³¹P, ⁷⁷Se NMR spectral measurements. The steric crowding of the phosphanes as complex ligands has been estimated from ³¹P–¹H coupling constants according to the Tolman model. The configuration of the methyl substituents as well as the conformation of the six‐membered ring were determined by NMR parameters (coupling constants, noe's) and proved by X‐ray crystal structure analysis.     

Nanometer‐sized alumina packed microcolumn solid‐phase extraction combined with field‐amplified sample stacking‐capillary electrophoresis for the speciation analysis of inorganic selenium in environmental water samples

In this paper, a new method of nanometer‐sized alumina packed microcolumn SPE combined with field‐amplified sample stacking (FASS)–CE‐UV detection was developed for the speciation analysis of inorganic selenium in environmental water samples. Self‐synthesized nanometer‐sized alumina was packed in a microcolumn as the SPE adsorbent to retain Se(IV) and Se(VI) simultaneously at pH 6 and the retained inorganic selenium was eluted by concentrated ammonia. The eluent was used for FASS–CE–UV analysis after NH₃ evaporation. The factors affecting the preconcentration of both Se(IV) and Se(VI) by SPE and FASS were studied and the optimal CE separation conditions for Se(IV) and Se(VI) were obtained. Under the optimal conditions, the LODs of 57 ng L^?1 (Se(IV)) and 71 ng L^?1 (Se(VI)) were obtained, respectively. The developed method was validated by the analysis of a certified reference material of GBW(E)080395 environmental water and the determined value was in a good agreement with the certified value. It was also successfully applied to the speciation analysis of inorganic selenium in environmental water samples, including Yangtze River water, spring water, and tap water.     

Diselenadiphosphetandiselenide und Triselenadiphospholandiselenide – Synthese und Charakterisierung mittels 31P‐ und 77Se‐Festkörper‐NMRSpektroskopie

Diselenadiphosphetane Diselenides and Triselenadiphospholane Diselenides – Synthesis and Characterization by ³¹P and ⁷⁷Se Solid‐State NMR Spectroscopy 1,3‐Diselena‐2,4‐diphosphetane‐2,4‐diselenides (RPSe₂)₂ with R = Me, Et, t‐Bu, Ph, 4‐Me₂NC₆H₄, 4‐MeOC₆H₄ have been synthesized by different methods. The insoluble compounds were investigated by ³¹P and ⁷⁷Se solid‐state NMR and the purity of the compounds has been checked by their CP MAS sideband NMR spectra. The structure of the investigated compounds has been confirmed by the isotropic and anisotropic values of the chemical shifts and the ¹J_P–Se coupling constants. In addition, two new 1,2,4‐triselena‐3,5‐diphospholane‐3,5‐diselenides, (RPSe₂)₂Se (R = Me, Et), formed under similar synthesis conditions, were investigated. Their structure was derived from the ⁷⁷Se satellites of ³¹P solution spectra and from solid‐state spectra. For (t‐BuPSe₂)₂ the experimentally obtained principal values of phosphorus and selenium shielding tensors are compared with values from IGLO calculations (HF und SOS DFPT). The calculated orientations of the principal axes are discussed.     

Synthesis,Structures, and Light‐Induced Transformation of Keto‐Functionalized Selenidogermanate Complexes

A double‐decker (DD) type selenidogermanate complex with C=O functionalized organic decoration, [(R¹Ge₄)Se₆] ( 1 , R¹ = CMe₂CH₂COMe), was synthesized by reaction of R¹GeCl₃ with Na₂Se, and subsequently underwent a light‐induced transformation reaction to yield [Na(thf)₂][(RGe^IV)₂(RGe^III)(Ge^IIISe)Se₅] ( 2 ). Similar to the observations reported previously for the Sn/S homologue of 1 , the product comprises a mixed‐valence complex with a newly formed Ge–Ge bond. However, different from the transformation of the tin sulfide complex, the selenidogermanate precursor did not produce a paddle‐wheel‐like dimer of the DD type structure, but led to the formation of a noradamantane (NA) type architecture, which has so far been restricted to the Si/Se and Ge/Te elemental combination.     

Monoxidised Sulfur and Selenium Derivatives of 1,8‐Bis(diphenylphosphino)naphthalene: Synthesis and Coordination Chemistry

Treatment of 1,8‐bis(diphenylphosphino)naphthalene (dppn, 1 ) with stoichiometric amounts of sulfur or selenium in toluene at 80 °C selectively afforded the diphosphine monochalcogenides 1‐Ph₂P(C₁₀H₆)‐8‐P(:S)Ph₂ (dppnS, 2 a ) and 1‐Ph₂P(C₁₀H₆)‐8‐P(:Se)Ph₂ (dppnSe, 2 b ). The ³¹P{¹H} NMR spectrum of 2 b showed an unusually large ⁵J(P–Se) value, which indicates a significant through‐space coupling component. The monosulfide acted as a bidentate P,S‐ligand towards platinum(II) ( 3 a ), whereas the corresponding monoselenide complex ( 3 b ′) lost elemental selenium with formation of the previously reported complex [PtCl₂(dppn)‐P,P′] ( 3 ). Treatment of dppnSe with [(nor)Mo(CO)₄] (nor = norbornadiene) led to formation of [(dppnSe)Mo(CO)₄‐P,Se] ( 3 b ). Solutions of the latter slowly deposited Se with formation of [(dppn)Mo(CO)₄‐P,P′] ( 4 ) which was also obtained by independent synthesis from 1 and [(nor)Mo(CO)₄]. All isolated new compounds were characterised by a combination of ³¹P, ¹H, ¹³C and ⁷⁷Se ( 2 b ) NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Single‐crystal X‐ray structure determinations were performed for dppnSe ( 2 b ), [PtCl₂(dppnS)‐P,S] ( 3 a ), [(dppnSe)Mo(CO)₄‐P,Se] ( 3 b ) and [(dppn)Mo(CO)₄‐P,P′] ( 4 ). In 2 b steric effects cause the naphthalene ring to be distorted and force the phosphorus atoms by 65 and 59 pm to opposite sides of the best naphthalene plane. In the metal complexes 3 a , 3 b and 4 the phosphino‐phosphinochalcogenyl systems act as bidentate ligands through the P and the chalcogen atoms. The naphthalene systems are again distorted. The two independent molecules of 4 differ in their conformations.     

Conformational analysis and stereochemical dependences of 31P–1H spin–spin coupling constants of bis(2‐phenethyl)vinylphosphine and related phosphine chalcogenides

Theoretical energy‐based conformational analysis of bis(2‐phenethyl)vinylphosphine and related phosphine oxide, sulfide and selenide synthesized from available secondary phosphine chalcogenides and vinyl sulfoxides is performed at the MP2/6‐311G** level to study stereochemical behavior of their ³¹P–¹H spin–spin coupling constants measured experimentally and calculated at different levels of theory. All four title compounds are shown to exist in the equilibrium mixture of two conformers: major planar s‐cis and minor orthogonal ones, while ³¹P–¹ H spin–spin coupling constants under study are found to demonstrate marked stereochemical dependences with respect to the geometry of the coupling pathways, and to the internal rotation of the vinyl group around the P(X)‐C bonds (X = LP, O, S and Se), opening a new guide in the conformational studies of unsaturated phosphines and phosphine chalcogenides. Copyright © 2009 John Wiley & Sons, Ltd.     

ZnCl2‐Promoted Asymmetric Hydrogenation of β‐Secondary‐Amino Ketones Catalyzed by a P‐Chiral Rh–Bisphosphine Complex

A new catalytic system has been developed for the asymmetric hydrogenation of β‐secondary‐amino ketones using a highly efficient P‐chiral bisphosphine–rhodium complex in combination with ZnCl₂ as the activator of the catalyst. The chiral γ‐secondary‐amino alcohols were obtained in 90–94 % yields, 90–99 % enantioselectivities, and with high turnover numbers (up to 2000 S/C; S/C=substrate/catalyst ratio). A mechanism for the promoting effect of ZnCl₂ on the catalytic system has been proposed on the basis of NMR spectroscopy and HRMS studies. This method was successfully applied to the asymmetric syntheses of three important drugs, (S)‐duloxetine, (R)‐fluoxetine, and (R)‐atomoxetine, in high yields and with excellent enantioselectivities.     

Steric and electronic evaluations of P(o‐tol)R2, where R is phenyl or cyclohexyl: crystal structures of SeP(o‐tol)R2

The crystal structures of SeP(o‐tol)R₂, where o‐tol is ortho‐tolyl (2‐methylphenyl) and R is Ph (phenyl), namely (2‐methylphenyl)diphenylphosphane selenide, C₁₉H₁₇PSe, or Cy (cyclohexyl), namely dicyclohexyl(2‐methylphenyl)phosphane selenide, C₁₉H₂₉PSe, were determined to aid in the evaluation of the steric and electronic behaviour of these analogous phosphane compounds. The compounds crystallized in similar monoclinic crystal systems, but are differentiated in their unit cells by a doubling of the number of independent molecules for R = Cy (Z′ = 2) and the choice of glide plane by convention. The preferred orientation for the o‐tolyl substituent obtained from the X‐ray structural analysis is gauche for R = Ph and anti for R = Cy (using the Se—P—C_ipso—C_ortho torsion angles as reference). Density functional theory (DFT) calculations showed both conformations to be equally probable and indicate that the preferred solid‐state conformer is probably due to the minimization of repulsion energies, resulting in a packing arrangement primarily featuring weak C—H…Se interactions and additional C—H…π interactions in the R = Ph structure. A detailed electronic and steric analysis was conducted on both phosphanes using Se—P bond lengths, multinuclear NMR ¹J_Se–P coupling constants, theoretical topological evaluation and crystallographic and solid‐angle calculations, and compared to selected literature examples. The results indicate that the use of the o‐tolyl substituent increases both the electron‐donating capability and the steric size, but is also dependent on whether the o‐tolyl group adopts a gauche or anti conformation. The single‐crystal geometrical data are unable to detect electronic differences between these two structures due to the somewhat large displacement parameters observed for the Se atom in the R = Cy structure.     

A T‐shaped selenenyl halide

The title selenenyl halide complex, 3‐iodo‐2‐phenyl‐3H‐3‐selenaindazole, C₁₂H₉IN₂Se, has an almost planar conformation and a nearly ideal T‐shape for the Se(INC) moiety [Se—I 2.8122 (12), Se—C 1.881 (7) and Se—N2 2.051 (6) Å; C—Se—N 79.6 (3), C—Se—I 96.8 (2) and N—Se—I 176.17 (17)°]. This arrangement, together with the two selenium lone pairs, leads to a distorted trigonal‐bipyrimidal geometry about the Se atom. Intermolecular interactions are largely limited to stacking forces.