Coordination complexes of 2‐thienyl‐ and 2‐furyl‐mercurials

The reactions of di(2‐thienyl)mercury, 2‐thienylmercury chloride and 2‐furylmercury chloride with a variety of nitrogen‐ and phosphorus‐containing ligands have been studied. The presence of the electron‐withdrawing heteroatoms results in these mercurials being stronger acceptors than the corresponding phenylmercury compounds. The complexes have been characterized by elemental analysis, melting points, infrared, and ¹⁹⁹Hg NMR spectroscopy. 2,9‐Dimethyl‐ and 3,4,7,8‐tetramethyl‐phenanthroline form 1:1 chelate complexes, as does 1,2‐bis(diphenylphosphino)ethane, whereas ethylenediamine and 2,2′‐bipyridyl do not form complexes. Though non‐chelating ligands such as 2,4′‐ and 4,4′‐bipyridyl do not form complexes, bis(diphenylphosphino)methane forms 1:2 complexes in which the ligand bridges two mercury atoms. Monodentate ligands, such as triphenylphosphine, cause disproportionation of the organomercury chloride. 2‐Thienylmercury chloride forms a 4:1 complex with 4,4′‐dipyridyl disulfide in which it is believed that a molecule of the organomercurial is coordinated to both of the nitrogen and both of the sulfur atoms. Copyright © 2004 John Wiley & Sons, Ltd.     

1,3‐Bis(ethylamino)‐2‐nitrobenzene, 1,3‐bis(n‐octylamino)‐2‐nitrobenzene and 4‐ethylamino‐2‐methyl‐1H‐benzimidazole

1,3‐Bis(ethylamino)‐2‐nitrobenzene, C₁₀H₁₅N₃O₂, (I), and 1,3‐bis(n‐octylamino)‐2‐nitrobenzene, C₂₂H₃₉N₃O₂, (II), are the first structurally characterized 1,3‐bis(n‐alkylamino)‐2‐nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2‐C and 5‐C atoms of the ring by twofold rotation axes. Both display intramolecular N—H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4 Å apart that interact by hydrophobic interactions involving the n‐alkyl groups rather than by π–π interactions between the rings. The intra‐ and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4‐ethylamino‐2‐methyl‐1H‐benzimidazole, C₁₀H₁₃N₃, (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N—H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4‐amino and 2‐alkyl substituents.     

Reactive EC(p‐p)π‐systems 53 [1]: Reactivity studies on perfluoro‐2‐arsapropene: [2+2]‐cycloaddition reactions and quantum chemical calculations

The extremely labile perfluoro‐2‐arsapropene F₃CAsCF₂ ( 1 ) has been generated by an improved pyrolysis process of Me₃SnAs(CF₃)₂ and found to be stabilized by the presence of hexamethyldisiloxane and tert‐butylphosphaethyne, thus allowing (i) reactivity studies with alkyne derivatives like tBuCP, (iPr)₂NCP, MeCCN(iPr)₂, HCCOEt and (ii) a full NMR investigation of 1 (¹⁹F, ¹³C). Due to the instability of 1 and some of the products, the [2+2]‐cycloaddition reactions gave the expected arsaphospha‐ and arsa‐cyclobutene derivatives, respectively, in moderate to good yields, but in some cases contaminated with side and/or decomposition products. Unequivocal characterization of the novel compounds was accomplished by spectroscopic in‐ vestigations (¹H, ¹³C, ¹⁹F, ³¹P NMR, IR, MS) supported by comparison with the data of the more stable phosphorus analogues. An interesting isomerization was observed for the 2‐dialkylamino‐4,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐3‐phospha‐2‐cyclobutenes yielding the more stable 3‐dialkylamino‐2,4‐difluoro‐ 1‐trifluoromethyl‐1‐arsa‐2‐phospha‐3‐cyclobutenes. Quantum chemical calculations [B3LYP/6‐311+ G(d,p)] of HAsCH₂, F₃CAsCF₂, and F₃CPCF₂ were carried out to compare the length of the AsC double bond with the literature data and to elucidate substituent effects on its electronic structure. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:406–419, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20118     

2‐(2′‐Pyridyl)‐4,6‐diphenylphosphinine versus 2‐(2′‐Pyridyl)‐4,6‐diphenylpyridine: Synthesis,Characterization, and Reactivity of Cationic RhIII and IrIII Complexes Based on Aromatic Phosphorus Heterocycles

The bidentate P,N hybrid ligand 1 allows access for the first time to novel cationic phosphinine‐based Rh^III and Ir^III complexes, broadening significantly the scope of low‐coordinate aromatic phosphorus heterocycles for potential applications. The coordination chemistry of 1 towards Rh^III and Ir^III was investigated and compared with the analogous 2,2′‐bipyridine derivative, 2‐(2′‐pyridyl)‐4,6‐diphenylpyridine ( 2 ), which showed significant differences. The molecular structures of [RhCl(Cp*)( 1 )]Cl and [IrCl(Cp*)( 1 )]Cl (Cp*=pentamethylcyclopentadienyl) were determined by means of X‐ray diffraction and confirm the mononuclear nature of the λ³‐phosphinine–Rh^III and Ir^III complexes. In contrast, a different reactivity and coordination behavior was found for the nitrogen analogue 2 , especially towards Rh^III as a bimetallic ion pair [RhCl(Cp*)( 2 )]⁺[RhCl₃(Cp*)]^? is formed rather than a mononuclear coordination compound. [RhCl(Cp*)( 1 )]Cl and [IrCl(Cp*)( 1 )]Cl react with water regio‐ and diastereoselectively at the external P?C double bond, leading exclusively to the anti‐addition products [MCl(Cp*)( 1 H ? OH)]Cl as confirmed by X‐ray crystal‐structure determination.     

Synthesis,one‐ and two‐photon properties of poly[9,10‐bis(3,4‐bis(2‐ethylhexyl‐oxy)phenyl)‐2,6‐anthracenevinylene‐alt‐N‐octyl‐3,6‐/2,7‐carbazolevinylene]

The synthesis, one‐ and two‐photon absorption (TPA) and emission properties of two novel 2,6‐anthracenevinylene‐based copolymers, poly[9,10‐bis(3,4‐bis(2‐ethylhexyloxy)phenyl)‐2,6‐anthracenevinylene‐alt‐N‐octyl‐3,6‐carbazolevinyl‐ene] ( P1 ) and poly[9,10‐bis(3,4‐bis(2‐ethylhexyloxy)phenyl)‐2,6‐anthracenevinyl‐ene‐alt‐N‐octyl‐2,7‐carbazolevinylene] ( P2 ) were reported. The as‐synthesized polymers have the number‐average molecular weights of 1.56 × 10⁴ for P1 and 1.85 × 10⁴ g mol^?1 for P2 and are readily soluble in common organic solvents. They emit strong bluish‐green one‐ and two‐photon excitation fluorescence in dilute toluene solution (? _P1 = 0.85, ? _P2 = 0.78, λ_em( P1 ) = 491 nm, λ_em( P2 ) = 483 nm). The maximal TPA cross‐sections of P1 and P2 measured by the two‐photon‐induced fluorescence method using femtosecond laser pulses in toluene are 840 and 490 GM per repeating unit, respectively, which are obviously larger than that (210 GM) of poly[9,10‐bis‐(3,4‐bis(2‐ethylhexyloxy) phenyl)‐2,6‐anthracenevinylene], indicating that the poly(2,6‐anthracenevinylene) derivatives with large TPA cross‐sections can be obtained by inserting electron‐donating moieties into the polymer backbone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 463–470, 2010     

Fragmentation‐related phosphinylations using 2‐aryl‐2‐phosphabicyclo[2.2.2]oct‐ 5‐ene‐ and ‐octa‐5,7‐diene 2‐oxides

A series of new P‐methylphenyl P‐heterocycles are introduced. The para and ortho substituted 2,5‐dihydro‐1H‐phosphole oxides ( 1a and 1b ) were converted to the double‐bond isomers ( A and B ) of 1,2‐dihydrophosphinine oxides ( 3a and 3b ) via the corresponding phosphabicyclo[3.1.0]hexane oxides ( 2a or 2b ). Isomeric mixture ( A and B ) of the dihydrophosphinine oxides ( 3a and 3b ) gave, in turn, the isomers ( A and B ) of phosphabicyclo[2.2.2]oct‐5‐enes ( 4a and 4b ) or a phosphabicyclo[2.2.2]octa‐5,7‐diene ( 5 ) in Diels‐Alder reaction with dienophiles. The bridged P‐heterocycles ( 4 and 5 ) were useful in the photo‐ or thermoinduced fragmentation‐related phosphinylation of hydroxy compounds and amines. The new precursors ( 4a and 4b ) were applied in mechanistic investigations. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:443–451, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10176     

π‐stacking and C—X...D (X = H,NO2; D = O, π) interactions in the crystal network of both C—H...N and π‐stacked dimers of 1,2‐bis(4‐bromophenyl)‐1H‐benzimidazole and 2‐(4‐bromophenyl)‐1‐(4‐nitrophenyl)‐1H‐benzimidazole

Molecules of 1,2‐bis(4‐bromophenyl)‐1H‐benzimidazole, C₁₉H₁₂Br₂N₂, (I), and 2‐(4‐bromophenyl)‐1‐(4‐nitrophenyl)‐1H‐benzimidazole, C₁₉H₁₂BrN₃O₂, (II), are arranged in dimeric units through C—H...N and parallel‐displaced π‐stacking interactions favoured by the appropriate disposition of N‐ and C‐bonded phenyl rings with respect to the mean benzimidazole plane. The molecular packing of the dimers of (I) and (II) arises by the concurrence of a diverse set of weak intermolecular C—X...D (X = H, NO₂; D = O, π) interactions.     

Synthesis of 4‐amino‐3‐cyano‐2‐ methylsulfanyl‐1H‐[1,5]benzodiazepine,benzo[1,3]azole,and pyrazolobenzo[1,3]azole derivatives via a new utility of bis(methylsulfanyl)methylene derivatives

Novel polysubstituted 1,5‐benzodiazepine 5 , 2,2‐bis(methylthio)benzoxazoles 8a–d , 2,2‐bis‐ (acetyl)benzoxazole 8e , 2‐(3‐methyl‐1‐phenylpyrazolo‐ 4‐yl)benzoazole derivatives 16a–c , as well as the previously reported 2‐di[cyano(acetyl)‐methylene]benzothiazoles 7a,b have been obtained via a new utility of ketene dithioacetals 1a,b and 12 with aniline derivatives 2 . Rationales for the reactions pathways are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:407–412, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20031     

Facile synthesis of 2‐alkylthio‐3‐amino‐4 H‐imidazol‐4‐ones and 2H‐imidazo[2,1‐b]‐1,3,4‐thiadiazin‐6(7H)‐ones via N‐vinylic iminophosphorane

2‐Alkylthio‐3‐amino‐4H‐imidazol‐4‐ ones 5 were synthesized by S‐alkylation of 2‐thioxo‐3‐amino‐4‐imidazolidinones 4 , which were obtained via cyclization of isothiocyanates 2 with hydrazine hydrate. 5l–n reacted with Ph₃P, C₂Cl₆, and NEt₃ to give 2H‐imidazo[2,1‐b]‐1,3,4‐thiadiazin‐ 6(7H)‐ones 7a–c in good yields. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:76–80, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20069     

Reactions of 2‐(1,3‐Dithiolan‐2‐ylidene)malononitrile with Amino‐ and Hydrazinophosphorus Compounds: A Facile Route to Functionalized Phosphorus Heterocycles

A facile and efficient route to functionalized phosphorus heterocycles was achieved by treatment of 2‐(1,3‐dithiolan‐2‐ylidene)malononitrile with amino‐ and hydrazinophosphorus compounds in the presence of a strong base via fragmentation of 1,3‐dithiolane ring.     

2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimidazole derivatives. Part II,lH nmr characterization

A selected series of 2‐(4‐methylpyridin‐2‐yl)‐1H‐benzimidazole derivatives, bases and cyclic mono‐ and bis‐salts, were synthesized. Complete ^'1H nmr characterization is reported. Ambiguous assignments were solved using ¹H‐¹H NOESY analysis. Significant ir and ¹H nmr data are presented concerning: i) tautomeric equilibrium of imidazole hydrogen; ii) hydrogen bonds; iii) conformational inversion of partially saturated rings.     

New 7‐phosphanorbornenes derived from 2‐methyl‐1‐phenyl‐ and 1‐cyclohexyl‐3‐ methyl‐2,5‐dihydro‐1H‐phosphole 1‐oxides

Novel 7‐phosphanorbornene derivatives, such as 4, 5, 10 , and 11 were synthesized utilizing 1‐phenyl‐2‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) and 1‐cyclohexyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 7 ) as the starting materials. Products 4 and 10 were prepared by trapping the corresponding phosphole oxide intermediates ( 3 and 9 , respectively) by N‐phenylmaleimide, while 5 and 11 were obtained by the dimerization of 3 and 9 , respectively. The trapping reaction was studied in details; on one hand, bromo‐2,3‐dihydro‐1H‐phosphole oxides ( 6‐1 and 6‐2 ) were pointed out as the intermediates, on the other hand, the trapping reaction was optimized. Bri‐ dged P‐heterocycles 4, 5, 10 , and 11 were tested in the fragmentation‐related phosphorylation of methanol. Hydrogenation of phosphanorbornenes 4 and 5 led to the corresponding phosphanorbornanes ( 12 and 14 , respectively) and to a reductive type of retro cycloaddition. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:320–326, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20097     

Preparation of Optically Active Six‐Membered P‐Heterocycles: A 3‐Phosphabicyclo[3.1.0] hexane 3‐oxide,a 1,2‐Dihydrophosphinine 1‐oxide,and a 1,2,3,6‐Tetrahydrophosphinine 1‐oxide

The earlier described a 3‐methyl‐1‐phenyl‐3‐phospholene 1‐oxide ( 1 ) → 6,6‐dichloro‐1‐methyl‐3‐phenyl‐3‐phosphabicyclo[3.1.0]hexane 3‐oxide ( 2 ) → 4‐chloro‐1‐phenyl‐1,2‐dihydrophosphinine 1‐oxide ( 3 ) → 4‐chloro‐5‐methyl‐1‐phenyl‐1,2,3,6‐tetrahydrophosphinine 1‐oxide ( 4 ) reaction sequence was investigated from the point of view of preparing optically active intermediates/products ( 2–4 ). In principle, both the resolution of the corresponding racemic products and the transformation of the optically active starting materials are suitable approaches for the preparation of optically active six‐membered P‐heterocycles ( 2–4 ). Racemization occurred during the dichlorocyclopropanation reaction of (S)‐3‐methyl‐1‐phenyl‐3‐phospholene 1‐oxide ((S)‐ 1 ), but the thermolytic ring opening of (−)‐ 2, and the selective reduction of α,β‐double bond of (−)‐ 3 did not cause the loss of optical activity. First in the literature, the resolution of a 3‐phosphabicyclo[3.1.0]hexane 3‐oxide ( 2 ) and a 1,2,3,6‐tetrahydrophosphinine 1‐oxide ( 4 ) was elaborated. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:179–186, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21080     

Synthesis and antimicrobial activity of 8‐alkylcarbamato‐16H‐dinaphtho [2,1‐d:1′,2′‐g] 1,3,2‐dioxaphosphocin 8‐oxides

A new family of phosphorus heterocycles, namely 8‐alkylcarbamato‐16H‐dinaphtho‐[2,1‐d: 1′,2′‐g] 1,3,2‐dioxaphosphocin 8‐oxides ( 4a–j ) has been obtained by reaction of bis(2‐hydroxy‐1‐naphthyl)methane ( 3 ) with a series of dichlorophosphosphinyl carbamates ( 2a–j ) in dry toluene in the presence of triethylamine at 40–45°C. The intermediates 2a–j were obtained by the addition of alcohols/thiol to isocyanatophosphonic dichloride ( 1 ) at −10°C in dry toluene. The structures of the title compounds were confirmed by the elemental analyses, IR, ¹H, ¹³C, and ³¹P NMR spectra. The FAB mass spectrum of one member of the family is discussed. These compounds were found to possess good antimicrobial activity. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:16–20, 2001     

Mono‐ and Binuclear Rhodium and Platinum Complexes of 1, 3, 5‐Trimethyl‐1, 3, 5‐triaza‐2σ3λ3‐phosphorin‐4, 6‐dionyloxy‐substituted Calix[4]arenes

The reaction behaviour of 1, 3, 5‐triaza‐2σ³λ³‐phosphorin‐4, 6‐dionyloxy‐substituted calix[4]arenes towards mono‐ and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)‐substituted calix[4]arene ( 4 ) and its tert‐butyl‐derivative ( 1 ) with [(cod)RhCl]₂ yielded the mono‐ and disubstituted binuclear rhodium complexes 2 , 3 , and 5 . In all cases, a C₂‐symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3‐alternating conformation. The X‐ray crystal structure determination of 5 confirmed [(calixarene)RhCl]₂‐coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh₂Cl₂ core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)‐bis(methoxy)‐substituted tert‐butyl‐calix‐[4]arene ( 7 ) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF₄ led to the expected cationic monorhodium complexes 5 and 8 , involving 1, 3‐alternating P‐Rh‐P‐coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the ¹J(PRh) coupling constants in the ³¹P‐NMR‐spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF₄, to the corresponding mononuclear cationic complexes 9 and 10 . Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta‐1, 5‐diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy. Reaction of 4 with (cod)PtCl₂ led to the PtCl₂‐complex ( 11 ). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ³¹P and characteristic values of ¹J(PPt)). NMR‐spectroscopic evidence was found for the existence of the cone conformation in the cis‐configuration of 11 .     

Intramolecular cyclization of N‐hetarylphosphinimidic isocyanates in the synthesis of 1,7‐dihydro‐4H‐imidazo[4,5‐d][1,3,2]diazaphosphinin‐4‐one (2‐phosphapurine)

It has been found that N‐(4‐imidazolyl)phosphinimidic isocyanates obtained by the reaction of the corresponding chlorophosphine N‐hetarylimide with alkali metal cyanates can undergo intramolecular heterocyclization to yield previously unknown phosphapurine derivatives containing an endocyclic PN double bond. This radically novel approach to building the 2‐phosphapurine system shows promise for the synthesis of related phosphorus‐containing fused heterocycles. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:453–455, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20617     

A challenging synthesis of new 1,3,4‐thiadiazole derivatives starting from 2‐acylamino‐3,3‐dichloroacrylonitriles

Available 2‐acylamino‐3,3‐dichloroacrylonitriles, when treated with hydrazine hydrate, provide 2‐alkyl‐ or 2‐aryl‐5‐hydrazino‐1,3‐oxazole‐4‐carbonitriles that readily add alkyl or aryl isothiocyanates and the adducts formed recyclize on heating. Finally, the synthesis results in 5‐alkyl(aryl)amino‐1,3,4‐thiadiazol‐2‐yl(acylamino)acetonitriles or the products of their further cyclization, 2‐(5‐amino‐1,3‐ oxazol‐2‐yl)‐1,3,4‐thiadiazole derivatives. The structures of the novel substituted 1,3,4‐thiadiazoles are corroborated spectroscopically as well as by X‐ray diffraction method. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:454–458, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20041     

Chiral NMR discrimination of the diastereoisomeric salts of the H3‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole

Diastereomeric salts with optically pure (S)‐α‐methoxy‐α‐(trifluoromethyl)phenylacetic acid (MTPA) were used to discriminate the enantiomers of the chiral H₃‐antagonist 2‐[3‐(1H‐imidazol‐4‐ylmethyl)piperidin‐1‐yl]‐1H‐benzimidazole. Chemical‐shift differences (Δδ) in NMR spectra strongly depend on solvent and stoichiometric ratio. The better observable differentiation occurred for the proton at the 2‐position of the imidazole ring. Copyright © 2009 John Wiley & Sons, Ltd.     

A Zwitterionic Phosphonio‐1, 2, 4‐Diazaphospholide and Neutral 1, 2, 4‐Diazaphosphole — A Comparative Study of Molecular Structures and Co‐ordination Properties

The bis‐phosphonio‐1, 2, 4‐diazaphospholide salt ( 1 [Cl]) reacts with complex boron hydrides under selective extrusion of one PPh₃ moiety to give borane adducts of a novel zwitterionic phosphonio‐1, 2, 4‐diazaphospholide. Both the Et₃B adduct 2b and the free zwitterionic heterocycle 3 , which was liberated by further reaction of 2b with NEt₃, were characterized by spectroscopic data and 2b , as well, by a single crystal X‐ray diffraction study. The comparison of the structural data with those of a neutral 1, 2, 4‐diazaphosphole and a lithium‐1, 2, 4‐diazaphospholide which was formed by deprotonation of the parent 1, 2, 4‐diazaphosphole 4a discloses trends in endocyclic bonding distances which can be rationalized in terms of a charge dependent shift in the π‐electron distribution. First studies of the co‐ordination properties reveal for both 2b and 4a a marked preference to bind two M(CO)₅‐fragments (M = Cr, W) via the lone‐pairs of the phosphorus and one nitrogen atom; mononuclear complexes with P‐co‐ordinated heterocycles are formed as intermediates. A single crystal X‐ray diffraction study of the dinuclear complex [Cr₂(CO)₁₀(μ₂‐C₂H₃N₂P‐κP, κN)] ( 10a ) together with spectroscopic studies (including ¹⁸³W NMR studies of tungsten complexes) suggests that M→L back donation is more efficient for P‐ than for N‐bound metal fragments. No evidence for π‐co‐ordination of the 1, 2, 4‐diazaphosphole ring to a Cr(CO)₃ fragment was obtained.     

1,8‐Bis[(dimethoxy)phosphino]naphthalene: A New Bis‐phosphonite Ligand with a Rigid C3‐Backbone and Unexpected Reaction Chemistry

1,8‐Bis[(diethylamino)phosphino]naphthalene ( 1 ) reacted with dry methanol in dichloromethane to form the new bis‐phosphonite ligand 1,8‐bis[(dimethoxy)phosphino]naphthalene (dmeopn, 2 ). By oxidation of 2 with H₂O₂ · (H₂N)₂C(:O) the corresponding bis‐phosphonate, 1,8‐bis[(dimethoxy)phosphoryl]naphthalene ( 3 ), was obtained quantitatively. Reaction of 3 with phosphorus trichloride unexpectedly furnished a 2.4 : 1 mixture of the bis‐phosphonate anhydrides rac‐ and meso‐1,3‐dimethoxy‐1,3‐dioxo‐2,3‐dihydro‐1,3‐diphospha‐2‐oxaphenalene (rac‐ 4 and meso‐ 4 ) from which rac‐ 4 could be fractionally crystallised. The bis‐phosphonite 2 behaved as a normal bidentate chelate ligand towards Mo⁰ and Pd^II, and furnished the complexes [(dmeopn)Mo(CO)₄] ( 5 ) and [(dmeopn)PdCl₂] ( 6 ) when treated with [(nor)Mo(CO)₄] or [(cod)PdCl₂] (nor = norbornadiene, cod = cycloocta‐1,8‐diene). Attempts to prepare 1,8‐diphosphinonaphthalene ( 7 ) by reducing 2 or 3 with LiAlH₄ or LiAlH₄/TMSCl (1 : 1) (TMSCl = trimethyl chlorosilane) in THF led to inseparable mixtures of phosphorus‐containing products. Compounds 2 – 6 were characterised by ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. X‐ray crystal structure analyses were carried out for the bis‐phosphonate anhydride rac‐ 4 and the palladium(II) complex 6 . The geometry of compound rac‐ 4 , in which the phosphorus atoms are connected by an oxygen atom, reveals a relief of strain from the bis‐phosphine 1 , whereas the 1,8‐P,P′‐naphthalenediyl group in 6 is surprisingly distorted; the P atoms are displaced from the naphthalene best plane by –46.7 and 54.5 pm.