[3+2] Cycloadditions of Metallo Nitrile Ylides and Metallo Nitrile Imines with Metal Carbonyl,Thiocarbonyl, and Isocyanide Complexes: Heterodimetallic Systems with Bridging Heterocycles [1]

The reactions of [Re(CO)₆]⁺, [FeCp(CO)₂CS]⁺ and [FeCp(CNPh)₃]⁺ with the metallo nitrile ylides [M^–{C⁺=N–C^–(H)CO₂Et}(CO)₅]^– (M = Cr, W) and the chromio nitrile imine [Cr^–{C⁺=N–N^–H}(CO)₅]^– (generated by mono‐α‐deprotonation of the parent isocyanide complexes) to give neutral 5‐metallated 1,3‐oxazolin‐ ( 1 ), 1,3‐thiazolin‐ ( 2 ), imidazolin‐ ( 3 , 4 ), 1,3,4‐oxdiazolin‐ ( 5 ), 1,3,4‐thiadiazolin‐ ( 6 ) and 1,3,4‐triazolin‐2‐ylidene ( 8 ) chromium and tungsten complexes represent the first all‐organometallic versions of Huisgen’s 1,3‐dipolar cycloadditions. The formation of 6 and 8 is accompanied by partial decomposition to (OC)₅Cr–C≡N–FeCpL₂ {L = CO ( 7 ), CNPh ( 9 )}. The structures of 4a and 5 have been characterized by X‐ray diffraction.     

Cobalt Carbonyls Stabilized by N,P-Ligands: Synthesis,Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation

Reactions of N,P-Ligands as Ph₂P(o-NMe₂C₆H₄) (¹L), 2,6-iPr₂C₆H₃NHC(Ph)=NC₆H₄(o-PPh₂) (²L), and Ph₂PN(R)PPh₂ (R=iPr (³L), cyclo-C₆H₁₁ (⁴L), tBu (⁵L), CH₂C₄H₇O (⁶L)) each with dicobalt octacarbonyl produced complexes [¹LCo(CO)₃]₂ ( 1 ), [²LCo(CO)(μ-CO)₂Co(CO)₃] ( 2 ), [³LCo(CO)₃]⁺[Co(CO)₄]⁻ ( 3 ), [³LCo(CO)₂]₂ ( 4 ), [⁴LCo(CO)₂]₂ ( 5 ), [⁵LCo(CO)₂]⁺[Co(CO)₄]⁻ ( 6 ), and [⁶LCo(CO)₂]⁺[Co(CO)₄]⁻ ( 7 ). Complexes 1–7 have all been structurally characterized by X-ray crystallography, IR and NMR spectroscopies, and elemental analysis. Catalytic tests on transformation of ethylene oxide (EO), CO and MeOH into methyl 3-hydroxypropionate (3-HMP) indicate that complexes 1 – 7 are active, where ion-pair complexes 3 and 6 – 7 behave more excellently (by achieving 88.4–93.6% 3-HMP yields) than the neutral species 1 – 2 and 4 – 5 (35.0–46.5% 3-HMP yields) when the reactions are all operated at 2 MPa CO pressure and 50 °C in MeOH solvent. Density functional theory (DFT) study by selecting 3 as a model suggests a cooperative catalytic reaction mechanism by [Co(CO)₄]⁻ and its counter cation [³LCo(CO)₃]⁺. The cobalt-homonuclear ion-pair catalyzed hydroalkoxycarbonylation of EO is present herein.     

Some binuclear complexes of iron and cobalt with isocyanide ligands

Whereas Co₂(CO)₈ and RNC (R= Me, Et, and Cy) react to give mixtures of [(RNC)₅Co] [Co(CO)₄] and the covalent, carbonyl-bridged [(RNC)_mCo₂(CO)_8?m] derivatives (m = 1–3), [(π-dienyl)Fe(CO)₂]₂ give only [(π-dienyl)₂Fe₂(CO)_4?n(CNR)_n] complexes (dienyl = C₅H₅, MeC₅H₄ and C₉H₇; n = 1–2) that exist in solution as mixtures of cis- and trans-CO- and RNC-bridged tautomers with the μ-RNC species decreasing in importance as the bulk of R increases.     

The reactions of [Fe(CO)5-n(CNAr)n] (n = 1 or 2; Ar = aryl) with dicyclopentadiene

Although [Fe(CO)₃(CNAr)₂] complexes fail to react with dicyclopentadiene at 140°C, under the same conditions [Fe(CO)₄(CNAr)] complexes give high yields of [Fe₂(η-C₅H₅(CO)₃(CNAr)] and [Fe₂(η-C₅H₅)₂(CO)₂-(CNAr)₂], with the product ratios depending very much on the aryl group (Ar).     

Organometallic Lewis Acids,Part LIX[1] Pentacarbonylrhenium Complexes with Phosphorus Tricyanide and Di­cyanophosphide

The addition of Re(CO)₅⁺ [as Re(CO)₅FBF₃] to P(CN)₃ and to P(CN)₂^– affords the complexes [Re(CO)₅]₃P(CN)₃(BF₄)₃ and Re(CO)₅P(CN)₂, respectively. The spectroscopic data indicate that Re(CO)₅⁺ is coordinated to each of the three cyano groups of P(CN)₃ to give {P[C≡N‐Re(CO)₅]₃}[BF₄]₃, whereas the pseudohalide P(CN)₂^– is bonded to the rhenium cation through the phosphorus atom.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe,V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V^[1]. – Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand^* The lithium and sodium salts of the [C₅H₅CH₂C₅H₄]^- anion, 1 and 2 , react with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [Ir(CO)₃Cl]n to give predominantly the mononuclear complexes [(C₅H₅-CH₂C₅H₄)M(CO)₂] ( 3, 5, 7 ) together with small amounts of the dinuclear compounds [CH₂(C₅H₄)₂][M(CO)₂]₂ ( 4, 6, 8 ). The ¹H- and ¹³C-NMR spectra of 3, 5 , and 7 prove that the CH₂C₅H₅ substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [C₅H₅TiCl₃] the heteronuclear complexes [CH₂(C₅H₄)₂][M(CO)₂][M′(CO)₂] ( 11–13 ) and [CH₂(C₅H₄)₂]-[Ir(CO)₂][C₅H₅TiCl₂] ( 17 ) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH₂(C₅H₄)₂][M(CO)(μ-CO)M′(CO)] ( 14, 15 ). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH₂(C₅H₄)₂][Rh₂(CO)₂(μ-CO)] ( 16 ).     

Reactions of [Ru(CO)3Cl2]2 with aromatic nitrogen donor ligands in alcoholic media

The reactions of mono‐ and bidentate aromatic nitrogen‐containing ligands with [Ru(CO)₃Cl₂]₂ in alcohols have been studied. In alcoholic media the nitrogen ligands act as bases promoting acidic behaviour of alcohols and the formation of alkoxy carbonyls [Ru(N–N)(CO)₂Cl(COOR)] and [Ru(N)₂(CO)₂Cl(COOR)]. Other products are monomers of type [Ru(N)(CO)₃Cl₂], bridged complexes such as [Ru(CO)₃Cl₂]₂(N), and ion pairs of the type [Ru(CO)₃Cl₃]^? [Ru(N–N)(CO)₃Cl]⁺ (N–N = chelating aromatic nitrogen ligand, N = non‐chelating or bridging ligand). The reaction and the product distribution can be controlled by adjusting the reaction stoichiometry. The reactivity of the new ruthenium complexes was tested in 1‐hexene hydroformylation. The activity can be associated with the degree of stability of the complexes and the ruthenium–ligand interaction. Chelating or bridging nitrogen ligands suppresses the activity strongly compared with the bare ruthenium carbonyl chloride, while the decrease in activity is less pronounced with monodentate ligands. A plausible catalytic cycle is proposed and discussed in terms of ligand–ruthenium interactions. The reactivity of the ligands as well as the catalytic cycle was studied in detail using the computational DFT methods. Copyright © 2005 John Wiley & Sons, Ltd.     

About the Reaction of C(PPh3)2 with [M(CO)6] (M = Cr,Mo): Unusual Formation of μ-Carbonato Complexes of Mo under Participation of THF

Attempts to synthesize complexes of group 6 carbonyl compounds [M(CO)₆] (M = Cr, Mo, W) with the carbone C(PPh₃)₂ ( 1 ) via the photo chemically created adducts [(CO)₅M(THF)] lead to quantitative formation of the salts [HC(PPh₃)₂]₂[M₂(CO)₁₀] ( 2 , Cr; 3 , Mo; 4 , W). Alternatively, a long-time thermal reaction of [Mo(CO)₆] performed with 1 in THF generates a series of products initiated by a Wittig-type reaction. In addition to 3 , minor amounts of [(CO)₅MoCCPPh₃] ( 8 ), [(CO)₅MoO₂CC{PPh₃}₂] ( 5 ), and the carbonate complexes [HC(PPh₃)₂]₂[(CO)₅Mo(CO₃)Mo(CO)₄] ( 6 ) and [HC(PPh₃)₂]₂[(CO)₄Mo(CO₃)Mo(CO)₄] ( 7 ) were found. Compounds 2 , 3 , 5 , 6 , and 7 were characterized by X-ray analyses, ³¹P NMR, and IR spectroscopy. The water, necessary for the formation of the carbonate, stems from decomposition of THF.     

Chemistry of (Carbonyl)(nitrosyl)[bis(phosphorus donor)]rhenium Complexes

The chemistry of [Re(CO)(NO)L₂] fragments (L ? phosphorus donor) was explored. Starting from [Re(CO)₅Cl] the synthesis of [Re₂Cl₂(μ-Cl)₂(CO)₄(NO)₂] ( 1 ) was accomplished via the preparation of [Et₄N]₂[Re₂Cl₂(μ-Cl)₂(CO)₆] and nitrosylation of this compound with [NO][BF₄]. Complex 1 was converted to [RecL₂(CO)(NO)L₂] complexes 2 ( a L = (MeO)₃P; b L = (EtO)₃P; c L = (i-PrO)₃P; d L ? Me₃P; e L ? Et₃P; f L ? Cy₃P) by heating with L in MeCN. In the case of the reaction of L = (MeO)₃P, a trisubstitued compound mer-{ReCl₂(NO)[P(OMe)₃]₃} 3 was also obtained. Replacement of the Cl ligands in 2a–e with Me groups was achieved by reacting them with MeLi in Et₂O yielding cis, trans-[Re(CO)(NO)Me₂L₂]complexes 4a–e . Reaction of 2a–e with Li[BHEt₃] led to substitution of one Cl by an H ligand with formation of [ReCl(CO)H(NO)L₂] compounds 5a–;e , displaying trans-H,NO geometries. The hydride-transfer agent Na[AlH₂(OCH₂CH₂OCH₃)₂] transformed 2 into the cis-dihydride systems [Re(CO)H₂(NO)L₂] 6a–f . Reductive carbonylation of 2a–d in the presence of Na/Hg and CO gave pentacoordinate [Re(CO)₂(NO)L₂] complexes 7b–d , and under comparable conditions the Cl substituents of 2b–f were replaced by tolane using Mg or t-BuLi giving trigonal bipyramidal [Re(CO)(NO)L₂(PhC?CPh)] compounds 8b–f . Complexes 5c , 6a , and 8d were characterized by X-ray crystal-structure analysis.     

Chemie polyfunktioneller Moleküle. 82. Neue Rhodium(I)-Chelatkomplexe mit N,N-Bis(diphenylphosphino)alkyl- und -arylaminen

Chemistry of Polyfunctional Molecules. 82. New Rhodium(1) Chelate Complexes with N,N-Bis(diphenylphosphino) alkyl- and -arylamines . [Rh(μ-Cl)(CO)₂]₂ ( 1 ) reacts with (Ph₂P)₂NR (2, a: R = C₆H₅, b: R = p-C₆H₄CH₃) in a molar ratio of 1:2 to give the square plane, ionic complexes [Rh{(PH₂P)₂NR}₂] [cis-Rh(CO)₂Cl₂] ( 3a, b ). By the reactions of [Rh(μ-Cl)(C₈H₁₂)]₂(C₈H₁₂ = 1.5-Cyclooctadiene) (4) with (Ph₂P)₂NR ( 2a–d ) (c: R = CH₃, d: R = C₂H₅) in the molar ratios of 1:4 the square plane 1:1 electrolytes [Rh{(Ph₂P)₂NR}₂]Cl ( 5a–d ) are obtained. Upon treatment of 5a–d in dichloromethane with CO the complexes [Rh(CO){(Ph₂P)₂NR}₂]Cl ( 6a–d ) are formed. They are only stable in solution and in CO atmosphere and were identified by infrared spectroscopy. The new complexes have been characterized, as far as possible, by conductometry, IR; FIR, Raman, ³¹P-NMR, and ¹H-NMR spectra.     

Octacarbonyl Ion Complexes of Actinides [An(CO)8]+/− (An=Th,U) and the Role of f Orbitals in Metal–Ligand Bonding

The octacarbonyl cation and anion complexes of actinide metals [An(CO)₈]^+/− (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO)₈]⁺ and [Th(CO)₈]⁻ complexes have a distorted octahedral (D_4h) equilibrium geometry and a doublet electronic ground state. Both the [U(CO)₈]⁺ cation and the [U(CO)₈]⁻ anion exhibit cubic structures (O_h) with a ⁶A_1g ground state for the cation and a ⁴A_1g ground state for the anion. The neutral species [Th(CO)₈] (O_h; ¹A_1g) and [U(CO)₈] (D_4h; ⁵B_1u) have also been calculated. Analysis of their electronic structures with the help on an energy decomposition method reveals that, along with the dominating 6d valence orbitals, there are significant 5f orbital participation in both the [An]←CO σ donation and [An]→CO π back donation interactions in the cations and anions, for which the electronic reference state of An has both occupied and vacant 5f AOs. The trend of the valence orbital contribution to the metal–CO bonds has the order of 6d≫5f>7s≈7p, with the 5f orbitals of uranium being more important than the 5f orbitals of thorium.     

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

Dimeric chlorobridge complex [Rh(CO)₂Cl]₂ reacts with two equivalents of a series of unsymmetrical phosphine–phosphine monoselenide ligands, Ph₂P(CH₂)_nP(Se)Ph₂ {n = 1( a ), 2( b ), 3( c ), 4( d )}to form chelate complex [Rh(CO)Cl(P∩Se)] ( 1a ) {P∩Se = η²‐(P,Se) coordinated} and non‐chelate complexes [Rh(CO)₂Cl(P～Se)] ( 1b–d ) {P～Se = η¹‐(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH₃I, C₂H₅I, C₆H₅CH₂Cl and I₂ to produce Rh(III) complexes of the type [Rh(COR)ClX(P∩Se)] {where R = ? C₂H₅ ( 2a ), X = I; R = ? CH₂C₆H₅ ( 3a ), X = Cl}, [Rh(CO)ClI₂(P∩Se)] ( 4a ), [Rh(CO)(COCH₃)ClI(P～Se)] ( 5b–d ), [Rh(CO)(COH₅)ClI‐(P～Se)] ( 6b–d ), [Rh(CO)(COCH₂C₆H₅)Cl₂(P～Se)] ( 7b–d ) and [Rh(CO)ClI₂(P～Se)] ( 8b–d ). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH₃I and C₂H₅I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d . The CH₃I reacts with the different complexes at a rate 10–100 times faster than the C₂H₅I. The catalytic activity of complexes 1b–d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well‐known commercial species [Rh(CO)₂I₂]^?. Copyright © 2006 John Wiley & Sons, Ltd.     

Theoretical study of electronic spectra of [Pt3(μ‐CO)3(CO)3] (n = 3–5) complexes

The platinum‐platinum attraction and the spectroscopic properties of [Pt₃(μ‐CO)₃(CO)₃] (n = 3–5) were studied at the PBE level. Theoretical calculations are in agreement with experimental geometries. The absorption spectra of these platinum complexes were calculated by the single excitation time‐dependent (TD) density functional method. All complexes showed MLCT transitions interrelated with the intertriangular complexes. The values obtained at the PBE level are in agreement with the experimental color range. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

New Routes to a Series of σ‐Borane/Borate Complexes of Molybdenum and Ruthenium

A series of agostic σ‐borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room‐temperature reaction of [Cp*Mo(CO)₃Me], 1 with Li[BH₃(EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)₂(μ‐H)BH₂EPh] in good yields. With 2‐mercapto‐benzothiazole, an N,S‐carbene‐anchored σ‐borate complex [Cp*Mo(CO)₂BH₃(1‐benzothiazol‐2‐ylidene)] ( 5 ) was isolated. Further, a transmetalation of the B‐agostic ruthenium complex [Cp*Ru(μ‐H)BHL₂] ( 6 , L=C₇H₄NS₂) with [Mn₂(CO)₁₀] affords a new B‐agostic complex, [Mn(CO)₃(μ‐H)BHL₂] ( 7 ) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)₃] unit. Natural‐bond‐orbital analyses of 5–7 indicate significant delocalization of the electron density from the filled σ_B?H orbital to the vacant metal orbital.     

Übergangsmetallphosphidokomplexe. XIII. P-funktionelle phosphidoverbrückte Heterozweikernkomplexe mit und ohne Metall-Metall-Bindung; P(SiMe3)2-verbrückte cp(CO)xFe-Derivate

Transition Metal Phosphido Complexes. XIII. P-functional Phosphido-Bridged Heterobimetallic Complexes with and without a Metal-Metal Bond; P(SiMe₃)₂-Bridged cp(CO)_xFe Derivatives cp(CO)₂FeP(SiMe₃)₂ 1 reacts with the carbonyl nitrosyl complexes Co(CO)₃(NO), Fe(CO)₂(NO)₂,Mn(CO)(NO)₃ substituting a CO ligand and with the THF complexes M′(CO)₅THF(M′ = Cr, Mo, W), Mncp(CO)₂THF MnMecp(CO)₂ which can be obtained in solution substituting the THF ligand to give the phosphido-bridged bimetallic complexes cp(CO)₂Fe[μ-P(SiMe₃)₂]M′L_m 2 (M′L_m = Co(CO)₂(NO) b , Fe(CO)(NO)₂ c , Mn(NO)₃ d , Cr(CO)₅ f , Mo(CO)₅ g , W(CO)₅ h , Mncp(CO)₂ i , MnMecp(CO)₂ j ). Solutions of Li(Me₃Si)₂PM′L_m 4e–l (M′L_m = Fe(CO)₄ e , Crcp(CO)(NO) k , Vcp(CO)₃ l ) are available by a selective cleavage reaction of a Si? P bond in the complexes (Me₃Si)₃PM′L_m 3e–l using n-BuLi. Reactions of cp(CO)₂FeBr with 4e–l give the bimetallic complexes 2e–l . The open-chain complexes 2c, 2f, 2h–k undergo a photochemical decarbonylation reaction to form the phosphido-bridged bimetallic complexes cp(CO)Fe[μ-CO, μ-P(SiMe₃)₂]M′L_m?1(Fe-M′) 5 (M′L_m?1 = Fe(NO)₂ c , Cr(CO)₄ f , W(CO)₄ h , Mncp(CO) i , MnMecp(CO) j , Crcp(NO) k ) containing a metal-metal bond. Equilibria between various isomers can partially be observed in solutions of the complexes 5. I.R., N.M.R., and mass spectral data are reported.     

Reaction Behavior of Decacarbonyldimetalates(2‐) (M = Cr and Mo) towards the Nitrosyl Carbonyls of Iron and Cobalt

The reaction of the nitrosyl carbonyl complexes [Fe(NO)₂(CO)₂] and [Co(NO)(CO)₃] with the decacarbonyldimetalates [M₂(CO)₁₀]^2– (M = Cr and Mo) in THF as the solvent at room temperature was investigated. Thereby a substitution of one nitrosyl ligand towards carbon monoxide was observed in each case. Both reactions afforded the known metalate complexes [Fe(NO)(CO)₃]^– and [Co(CO)₄]^–, respectively. These species were isolated as their corresponding PPN salts [PPN⁺ = bis(triphenylphosphane)iminium cation] in nearly quantitative yields. The products were unambiguously identified by their IR spectroscopic and elemental analytic data as well as by their characteristic colors and melting points.     

Dimerisation of Dipiperidinoacetylene: Convenient Access to Tetraamino-1,3-Cyclobutadiene and Tetraamino-1,2-Cyclobutadiene Metal Complexes

The reaction of 1,2-dipiperidinoacetylene ( 1 ) with 0.5 equivalents of SnCl₂ or GeCl₂⋅dioxane afforded the 1,2,3,4-tetrapiperidino-1,3-cyclobutadiene tin and germanium dichloride complexes 2 a and 2 b , respectively. A competing redox reaction was observed with excess amounts of SnCl₂, which produced a tetrapiperidinocyclobutadiene dication with two trichlorostannate(II) counterions. Heating neat 1 to 110 °C for 16 h cleanly produced the dimer 1,3,4,4-tetrapiperidino-3-buten-1-yne ( 3 ); its reaction with stoichiometric amounts of SnCl₂ or GeCl₂⋅dioxane furnished the 1,3,4,4-tetrapiperidino-1,2-cyclobutadiene tin and germanium dichloride complexes 4 a and 4 b , respectively. Transition-metal complexes containing this novel four-membered cyclic bent allene (CBA) ligand were prepared by reaction of 3 with [(tht)AuCl], [RhCl(CO)₂]₂, and [(Me₃N)W(CO)₅] to form [(CBA)AuCl] ( 5 ), [(CBA)RhCl(CO)₂] ( 6 ), and [(CBA)W(CO)₅] ( 7 ). The molecular structures of all compounds 2 – 7 were determined by X-ray diffraction analyses, and density functional theory (DFT) calculations were carried out to rationalise the formation of 3 and 4 a .     

Reactions of RSe− (R = Me,Ph) Groups in [RSeFe(CO)4I and [RSeCr(CO)5−]

The anionic [MeSeFe(CO)₄] and [MeSeCr(CO)₅] complexes were synthesized by reaction of [PPN][HFe(CO)₄] and [PPN][HCr(CO)₅] with MeSeSeMe respectively via nucleophilic cleavage of the Se-Se bond. The ease of cleavage of the Se-Se bond follows the nucleophilic strength of metal-hydride complexes. Methylation of [RSeCr(CO)₅^?] by the soft alkylating agent MeI resulted in the formation of neutral (MeSeMe)Cr(CO)₅ in THF at 0°C. In contrast, the [ICr(CO)₅^?] was isolated at ambient temperature. Reaction of [MeSeFe(CO)₄^?] or [MeSeCr(CO)₅^?] with HBF₄ yielded (CO)₃Fc(μ-SeMe)₂Fe(CO)₃ dimer and anionic [(CO )₅Cr (μ-SeMe)Cr(CO)₅^?] respectively, and no neutral (HSeMe)Fe(CO)₄ and (HSeMe)Cr(CO)₅ were detected spectrally (IR) even at low temperature. Reaction of NOBF₄ or [Ph₃C][BF₄] and [MeSeCr(CO)₅^?] resulted in the neutral monodentate (MeSeSeMe)Cr(CO)₅ complex. Addition of 1 equiv CpFe(CO)₂I to 2 equiv [MeSeCr(CO)₅^?] gave CpFe(CO)₂(SeMe) and the anionic [(CO)₅Cr(μ-SeMe)Cr(CO)₅^?] in THF at ambient temperature.     

Reactions of Tri‐tert‐butylazadiboriridine NB2R3 with Carbonyl and Similar Species

The carbonyl group of X(R')CO is added to the B—B bond of the three‐membered ring compound NB₂R₃ ( 1 ; R = tBu) to give the five‐membered rings [—BR—NR—BR—X(Rapos;)C—O—] ( 2a — d ; Rapos;/X = tBu/H, Ph/Ph, H/OMe, H/NMe₂). The tetraazoniatetraboratatricyclo[6.2.0.0^{3, 6}]deca‐2, 4, 7, 9‐tetraenes N₄B₄C₂R₆Rapos;₂ ( 4a , b ; Rapos; = Me, Et), known products from the reaction of 1 with isonitriles CNRapos;, undergo a rearrangement to give the corresponding deca‐1, 4, 6, 9‐tetraenes 6a , b by the migration of two tBu groups from boron to carbon on photolysis; the structure of 6a is confirmed by X‐ray analysis. The reaction of CO, generated from carbonylmetal complexes (photolytically from [Cr(CO)₆] or [Cp₂Fe₂(CO)₄]; thermally from [Fe₂(CO)₉] or [Co₂(CO)₈]), with 1 gives the 3, 7‐dioxonia‐1, 5‐diazonia‐2, 4, 6, 8‐tetraboratanaphtalene O₂N₂C₂B₄R₆ ( 7 ), as has been known from the reaction of [Fe(CO)₅] and 1 . The product 7 is also obtained from the isomeric dispiro compound 5 , the known product from the reaction of 1 with gaseous CO at —78 °C, by standing in solution at room temperature. Surprisingly, the reaction of 1 with CO from the photolysis of [CpMn(CO)₃] gives a naphthalene‐type isomer of 7 , the 1, 5‐dioxonia‐3, 7‐diazonia species 8 , the crystal structure of which is reported.     

Studies of chelation IV. Steric influences on the chelation of ditertiary phosphine complexes of group VI metal carbonyls

The preparation of the complexes [M(CO)_n(dcpe)] [M  Cr, Mo, W; n  4, 5; dcpe is ((cyclo-C₆H₁₁)₂PCH₂)₂] is reported. Attempts to prepare [M(CO)₂(dcpe)₂] by many different methods gave only cis-[M(CO)₄(dcpe)] and [M(CO)₅(dcpe)]. Heating cis-[M(CO)₄(dcpe)] with (Me₂PCH₂)₂(dmpe) gives cis-[M(CO)₂(dmpe)₂] only. These observations are explained in terms of unfavourable intramolecular non-bonded interactions between substituents at phosphorus. The rate of chelation of [M(CO)₅(dcpe)] to give cis-[M(CO)₄(dcpe)] has been measured at various temperatures in the range 360–420 K. The activation parameters indicate the dominance of a dissociative process leading to the observed steric acceleration in the chelation step. The rate of chelation is correlated satisfactorily with the ligand cone angle; the operation of an apparent saturation effect is noted.