Photochemical reactions of group VIB metal carbonyls with heterocyclic Schiff bases derived from 4-amino -3-hydrazino-5-mercapto-1,2,4-triazole

The new complexes, M(CO)₅(Schiff base) [M?=?Cr; 1, Mo; 2, W; 3, Schiff base?=?4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole, SAHMT, a; 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 2HNAHMT, b; 4-(3-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 3HBAHMT, c; 4-(4-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 4HBAHMT, d; 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 5BrSAHMT, e; were synthesized by photochemical reaction of metal carbonyls M(CO)₆ (M?=?Cr, Mo, W) with new heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a–e. The ligands and complexes have been characterized by elemental analysis, EI-mass spectrometry, FT-IR, ¹H and ¹³C-{¹H}-NMR spectroscopy. The spectroscopic studies show that Schiff bases, a–e, are monodentate and coordinate via azomethine N donor to the central metal atom in M(CO)₅(Schiff base) (M?=?Cr, Mo, W).     

Reaction of metal carbonyls with 2-hydroxy-1-naphthaldeyde methanesulfonylhydrazone and characterization of the substitution products

Five new complexes, [M(CO)₅(nafmsh)] [M?=?Cr, 1; Mo, 2; W, 3], [Re(CO)₄Br(nafmsh)], 4 and [Mn(CO)₃(nafmsh)], 5 have been synthesized by the photochemical reaction of metal carbonyls [M(CO)₆] (M?=?Cr, Mo, W), [Re(CO)₅Br], and [Mn(CO)₃Cp] with 2-hydroxy-1-naphthaldehyde methanesulfonylhydrazone (nafmsh). The complexes have been characterized by elemental analysis, EI mass spectrometry, FT-IR, and ¹H NMR spectroscopy. The spectroscopic studies show nafmsh is a monodentate ligand coordinating via the imine N donor atom in 1–4 and as a tridentate ligand in 5.     

Synthese,Charakterisierung und Kristallstrukturen der Pseudohalogen‐Kronenether‐Komplexe [K([18]krone‐6)(X)(OPPh3)] (X = N3–, OCN– und SCN–)

Preparation, Characterisation, and Crystal Structures of the Pseudohalogen Crown Ether Complexes [K([18]crown‐6)(X)(OPPh₃)] (X = N₃^–, OCN^– and SCN^–) The potassium crown ether complexes [K([18]Crown‐6)(X)(OPPh₃)] (with X = N₃^–, OCN^– and SCN^–) can be obtained by reaction of KX with 18‐crown‐6 (1, 4, 7, 10, 13, 16‐hexaoxacyclooctadecane and triphenylphosphane in THF exposed to UV light. All crown ether complexes were characterized by means of vibrational spectroscopy and X‐ray diffraction. They crystallize in the rhombic pointgroup R3m with three molecules in the unit cell: [K([18]crown‐6) (N₃)(OPPh₃)] ( 1 ): lattice constants at 293 K: a = b = 14.213(2) Å; c = 13.951(2) Å; R₁ = 0.0249. [K([18]crown‐6)(OCN)(OPPh₃)] ( 2 ): a = b = 14.239(2) Å; c = 13.8927(14) Å; R₁ = 0.0257. [K([18]crown‐6)(NCS)(OPPh₃)] ( 3 ): a = b = 14.339(2) Å; c = 14.266(2) Å; R₁ = 0.0264.     

Group 6 metal carbonyl complexes of 3′H-spiro[indole-3,2′-[1,3]benzothiazole-2(1H)]-one

The spiro-compound 3′H-spiro[indole-3,2′-[1,3]benzothiazole-2(1H)-one (IBTH₂) was synthesized and its structure was determined using spectroscopic techniques (FTIR, ¹H NMR and mass) and X-ray crystallography. This ligand possesses different centers for coordination. Reactions of [M(CO)₆], M = Cr, Mo or W with IBTH₂ in THF under reduced pressure were studied. For chromium a complex with molecular formula [Cr(ITP)₂] was isolated; where ITP is the opened form of the ligand which occurred through C_spiro–S bond, while [Mo(CO)₅(IBTH₂)] and [W(CO)₅(IBTH₂)] were isolated from the reaction of IBTH₂ with molybdenum and tungsten carbonyls, respectively. All complexes were characterized by elemental analysis, IR, mass and ¹H NMR spectroscopy. The biological activity of the ligand and its complexes were studied and compared with the parent compound isatin.     

Tricarbonylrhenium(I) and manganese(I) complexes of 2-(pyrazolyl)-4-toluidine

A series of tricarbonyl rhenium(I) and manganese(I) complexes of the electroactive 2-(pyrazolyl)-4-toluidine ligand, H(pzAn^Me), has been prepared and characterized including by single crystal X-ray diffraction studies. The reactions between H(pzAn^Me) and M(CO)₅Br afford fac-MBr(CO)₃[H(pzAn^Me)] (M = Mn, 1a; Re, 1b) complexes. The ionic species {fac-M(CH₃CN)(CO)₃[H(pzAn^Me)]}(PF₆) (M = Mn, 2a; Re, 2b) were prepared by metathesis of 1a or 1b with TlPF₆ in acetonitrile. Complexes 1a and 1b partly ionize to {M(CH₃CN)(CO)₃[H(pzAn^Me)]⁺}(Br⁻) in CH₃CN but retain their integrity in less donating solvents such as acetone or CH₂Cl₂. Each of the four metal complexes reacts with (NEt₄)(OH) in CH₃CN to give poorly-soluble crystalline [fac-M(CO)₃(μ-pzAn^Me)]₂ (M = Mn, 3a; Re, 3b). The solid state structures of 3a and 3b are of centrosymmetric dimeric species with bridging amido nitrogens and with pyrazolyls disposed trans- to the central planar M₂N₂ metallacycle. In stark contrast to the diphenylboryl derivatives, Ph₂B(pzAn^Me), none of the tricarbonyl group 7 metal complexes are luminescent.     

Synthesis,structural characterisation and reactivity of molybdenum half-sandwich complexes containing keto- and amido-phosphines

The keto-functionalised N-pyrrolyl phosphine ligand PPh₂NC₄H₃{C(O)CH₃-2} L¹ reacts with [MoCl(CO)₃(η⁵-C₅R₅)] (R=H, Me) to give [MoCl(CO)₂(L¹-κ¹P)(η⁵-C₅R₅)] (R=H 1a; Me 1b). The phosphine ligands PPh₂CH₂C(O)Ph (L²) and PPh₂CH₂C(O)NPh₂ (L³) react with [MoCl(CO)₃(η⁵-C₅R₅)] in an analogous manner to give the compounds [MoCl(CO)₂(L-κ¹P)(η⁵-C₅R₅)] (L=L², R=H 2a, Me 2b; L=L³, R=H 3a, Me 3b). Compounds 1–3 react with AgBF₄ to give [Mo(CO)₂(L-κ²P,O)(η⁵-C₅R₅)]BF₄ (L=L¹, R=H 4a, Me 4b; L=L², R=H 5a, Me 5b; L=L³, R=H 6a, Me 6b) following displacement of chloride. The X-ray crystal structure of 4a revealed a lengthening of both Mo–P and CO bonds on co-ordination of the keto group. The lability of the co-ordinated keto or amido group has been assessed by addition of a range of phosphines to compounds 4–6. Compound 4a reacts with PMe₃, PMe₂Ph and PMePh₂ to give [Mo(CO)₂(L¹-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 7a; PMe₂Ph 7b; PMePh₂ 7c) but does not react with PPh₃, 5a reacts with PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L²-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₂Ph 8b; PMePh₂ 8c; PPh₃ 8d), and 6a reacts with PMe₃, PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L³-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 10a; PMe₂Ph 10b; PMePh₂ 10c; PPh₃ 10d). No reaction was observed for the pentamethylcyclopentadienyl compounds 4b–6b with PMe₃, PMe₂Ph, PMePh₂ or PPh₃. These results are consistent with the displacement of the co-ordinated oxygen atom being influenced by the steric properties of the P,O-ligand, with PPh₃ displacing the keto group from L² but not from the bulkier L¹. In the reaction of [Mo(CO)₂(L²-κ²P,O)(η⁵-C₅H₅)]BF₄ (5a) with PMe₃ the phosphine does not displace the keto group, instead it acts as a base, with the only observed molybdenum-containing product being the enolate compound [Mo(CO)₂{PPh₂CHC(O)Ph-κ²P,O}(η⁵-C₅H₅)] 9. Compound 9 can also be formed from the reaction of 2a with BuLi or NEt₃, and a single crystal X-ray analysis has confirmed the enolate structure.     

Photochemical reactions of metal carbonyls [M(CO)6 (M=Cr,Mo, W)] with N,N′ -bis(salicylidene)-1,2-bis- ( o -aminophenoxy)ethane

The complexes [M(CO)₄(η²-H₂L)] [M?=?Cr; 1, Mo; 2, W; 3] have been synthesized by photochemical reactions of VIB metal carbonyls [M(CO)₆] [M?=?Cr,?Mo,?W] with N,N′-bis(salicylidene)-1,2-bis-(o-aminophenoxy)ethane (H₂L) in THF and characterized by elemental analyses, FTIR, ¹H?NMR and mass spectra. The H₂L ligand is coordinated to the central metal as a bidentate ligand via the central azomethine nitrogen atoms in 1–3.     

Chemie polyfunktioneller Moleküle, 94 Chrom- und Wolfram-pentacarbonylderivate des 4-Methyl-1,2,6-triphosphatricyclo[2.2.1.02,6]heptans (P3-Nortricyclans)

The P₃-nortricyclane 4-methyl-1,2,6-triphosphatricyclo[2.2.1.0^2,6]heptane, CH₃C(CH₂P)₃, (1), is synthesized in a better yield than earlier described from P₄, a Na/K alloy, and CH₃C(CH₂Br)₃ in boiling 1,2-dimethoxyethane. It reacts withM(CO)₅ thf (M=Cr, W) in the molar ratios of 1:1, 1:2, and 1:3 to form the pentacarbonylmetal complexes CH₃C(CH₂P)₃[M(CO)₅] _n [n=1, 2, 3;M=Cr (a), W (b)], (2 a, b–4 a, b).1 gives with Mo(CO)₅ thf only mixtures of CH₃C(CH₂P)₃[Mo(CO)₅] _n andcis-Mo(CO)₄ derivatives, which were identified by their infrared active A₁ v(CO) modes at 2075 and 2025 cm^–1.All the new compounds have been characterized also by their¹H{³¹P},³¹P{¹H} NMR, IR,Raman, and mass spectra.

     

Ruthenium(II) carbonyl complexes of P,P and P,O donor diphosphine ligands,Ph2P(CH2)nPPh2 and Ph2P(CH2)nP(O)Ph2, n = 2, 3 and their activities in catalytic transfer hydrogenation reactions

The polymeric precursor [RuCl₂(CO)₂]_n reacts with the ligands, P∩P (a, b) and P∩O (c, d), in 1:1 M ratio to generate six-coordinate complexes [RuCl₂(CO)₂(?²-P∩P)] (1a, 1b) and [RuCl₂(CO)₂(?²-P∩O)] (1c, 1d), where P∩P: Ph₂P(CH₂)_nPPh₂, n = 2(a), 3(b); P∩O: Ph₂P(CH₂)_nP(O)Ph₂, n = 2(c), 3(d). The complexes are characterized by elemental analyses, mass spectrometry, thermal studies, IR, and NMR spectroscopy. 1a–1d are active in catalyzed transfer hydrogenation of acetophenone and its derivatives to corresponding alcohols with turnover frequency (TOF) of 75–290 h^?1. The complexes exhibit higher yield of hydrogenation products than catalyzed by RuCl₃ itself. Among 1a–1d, the Ru(II) complexes of bidentate phosphine (1a, 1b) show higher efficiency than their monoxide analogs (1c, 1d). However, the recycling experiments with the catalysts for hydrogenation of 4-nitroacetophenone exhibit a different trend in which the catalytic activities of 1a, 1b, and 1d decrease considerably, while 1c shows similar activity during the second run.     

The Enhancement of the Formation of Wells–Dawson-Type Polyoxometalates by the Addition of High Concentrations of LiCl

Wells–Dawson-type polyoxometalates are formed by heating an acidic Mo(VI) or W(VI) solution containing significantly higher concentrations of hetero ions, P(V) or As(V), than the ideal molar ratio [M]/[X] = 1/9 (M = Mo, W; X = P, As). Most of the phosphate and arsenate remains unreacted in the reaction mixture. These reaction conditions are unusual, even though more reagents than the stoichiometric amounts are frequently needed to obtain complete reactions. In the present study, the replacement of a large amount of unreacted hetero ions containing salts by normal ions (salts) was investigated. The formation of Wells–Dawson-type polyoxometalates, [X₂M₁₈O₆₂]^6? (X = P, As; M = Mo, W), in the presence of LiCl and NaCl was investigated by Raman spectroscopy and ³¹P NMR in aqueous solution. The addition of LiCl enhanced the formation of Wells–Dawson-type polyoxometalates, which formed under solution conditions close to the ideal molar ratio [M]/[X] = 1/9.     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

X-ray crystallographic studies of tricarbonylchromium complexes of calix[4]arene conformers: On an unusual conformation which appears in cone conformers

The structures of three arene-tricarbonylchromium complexes prepared from cone and 1,3-alternate-25, 26,27,28-tetrapropoxycalix[4]arene(1) and Cr(CO)₆ were determined by single crystal X-ray studies. Crystal data for 1,3-alternate-1·Cr(CO)₃ are space groupP2₁/a,a=19.496(3)Å,b=11.118(2)Å,c=19.121(2)Å, =109.95°(1) andV=3895ų. The structure was refined toRw=0.068. Crystal data for cone-1·Cr(CO)₃ are space groupP2₁/a,a=21.457(4)Å,b=12.184(1)Å,c=14.816(2)Å, =91.61°(1) andV=3872ų. The structure was refined toRw=0.077. Crystal data for cone-1·2Cr(CO)₃ are space groupP2₁/a,a=18.019(3)Å,b=41.347(4)Å,c=11.743(2)Å, =97.39°(1) andV=8676ų. The single crystal included two similar but slightly different structures but the data were successfully refined toRw=0.092. The structure of 1,3-alternate-1·Cr(CO)₃ differs only slightly from that of the regular 1,3-alternate calix[4]arene. In contrast, cone-1·Cr(CO)₃ and cone-1·2Cr(CO)₃ show an unusual conformation with a pair of faced gablelike roofs, which is considerbly distorted from the regular cone calix[4]arene. The origin of this distortion is discussed in combination with the spectral studies.This paper is dedicated to the commemorative issue of the 50th anniversary of calixarenes.     

Synthesis and Crystal Structures of Four Novel Mo(W)/Cu/S Polymers Containing Thiolato Bridging Ligands

Four novel M/Cu/S polymers [Et₄N][MS₄Cu₃(S₂COEt)₂] (1a: M=Mo; 1b: M=W) and Et₄N][MS₄Cu₂SEt] (2a: M=Mo; 2b: M=W) have been prepared by reactions of [Et₄N]₂[MS₄] with CuS₂COEt and CuSEt. X-ray crystal structure determinations reveal that the polymeric anions of complexes 1a and 1b both consist of MS₄Cu₃ building blocks linked via bidentate [S₂COEt]⁻ bridging ligands to form 1D polymeric chains. The anion structures of the polymeric compounds 2a and 2b contain MS₄Cu₂ repeating units which are connected via μ-SEt⁻ ligands forming a zigzag chain running down the crystallographic b axis.     

Alkynylcarbyne complexes containing various tri- and bidentate ligands such as cyclopentadienide,tris(pyrazolyl)borate,bis(pyrazolyl)acetate and tmeda: synthesis and spectroscopic properties

The (alkynylcarbyne)tungsten complexes [L₃(CO)₂WCCCR] (3a,b–6a,b) [L₃=hydro[tris(3,5-dimethylpyrazol-1-yl)]borato (Tp′, 3), hydro[tris(pyrazol-1-yl)]borato (Tp, 4), cyclopentadienyl (Cp, 5), bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza, 6); R=SiMe₃ (a), Ph (b)] were prepared in a stepwise fashion from [W(CO)₆] and Li[CCR], (CF₃CO)₂O and M[L₃] (M=Na, K). The formation of 6a,b was highly selective, only complexes with a trans arrangement of the carboxylate group of bdmpza and the alkynylcarbyne ligand were detected. The reaction of [W(CO)₆] with Li[CCR], C₂O₂Cl₂ and tmeda afforded trans-[Cl(CO)₂(tmeda)WCCCR] (7a,b). The electron-donating potential of the different tripodal ligands L₃ was studied by IR- and ¹³C-NMR spectroscopy and compared to that of the ligand combination Cl/tmeda. The IR data suggest that in these complexes bdmpza is a weaker electron donor than Tp′ and Tp but displays stronger electron-donating abilities than Cp. The structures of 6b and 7b were established by X-ray structural analyses.     

Density functional theory prediction of cobalt pincer complexes for catalytic dehydrogenation of ethanol

A density functional theory (DFT) study reveals that dehydrogenation of ethanol catalyzed by aliphatic PNP pincer cobalt complexes, [(PNP^Et)Co(H)(OMe)] (1a) and [(PNP^Et)Co(H)(CH₂SiMe₃)] (1b) (PNP^Et = bis(2-(diethylphosphino)ethyl)amine), undergoes a self-promoted mechanism, in which an ethanol assists the formation of H₂ as a bridge for proton transfer. The calculated total free energy barriers of ethanol dehydrogenation catalyzed by 1a and 1b are 23.9 and 22.2 kcal mol^?1, respectively, which indicate that 1b is a promising catalyst for the dehydrogenation of ethanol under mild conditions.     

Di- and tri-nuclear molybdenum-palladium complexes bearing strong π-acceptor “P-N-P” ligands, MeN{P(OR)2}2 (R = CH2CF3 or Ph)

The dipalladium complexes, [PdCl(μ-MeN{P(OR)₂}₂)]₂ (R = CH₂CF₃, 1a; Ph, 1b) react with [Mo₂(η⁵-C₅H₅)₂(CO)₆] in boiling benzene to afford the molybdenum-palladium heterometallic complexes, [(η⁵-C₅H₅)(CO)Mo(μ-MeN{P(OR)₂}₂)₂PdCl] (R = CH₂CF₃, 3a; Ph, 3b), [(η⁵-C₅H₅)Mo(μ₃-CO)₂(μ-MeN{P(OR)₂}₂)₂Pd₂Cl], (R = CH₂CF₃, 5a; Ph, 5b), [(η⁵-C₅H₅)(Cl)Mo(μ₂-CO)(μ₂-Cl)(μ-MeN{P(OR)₂}₂)PdCl], (R = CH₂CF₃, 6a; Ph, 6b) and also the mononuclear complex [Mo(CO)Cl(η⁵-C₅H₅)(κ²-MeN{P(OR)₂}₂)], (R = Ph, 4b). These complexes have been separated by column chromatography and are characterised by elemental analysis, IR, ¹H, ³¹P{¹H} NMR data. The structures of 1a, 3a, 4b, 5b and 6a have been confirmed by single crystal X-ray diffraction. The CO ligands in 5b and 6a adopt a semi-bridging mode of bonding; the Mo-CO distances (1.95-1.97 Å) are shorter than the Pd-CO distances (2.40-2.48 Å). The Pd-Mo distances fall in the range, 2.63-2.86 Å. The reaction of [Mo₂(η⁵-C₅H₅)₂(CO)₆] with MeN{P(OPh)₂}₂ in toluene gives [Mo₂(CO)₄(η⁵-C₅H₅)₂(κ¹-MeN{P(OPh)₂}₂)₂] (2) in which the diphosphazane acts as a monodentate ligand.     

The Butterfly Complex [{Cp*Cr(CO)3}2(μ,η1:1-P4)] as a Versatile Ligand and Its Unexpected P1/P3 Fragmentation

The versatile coordination behavior of the P₄ butterfly complex [{Cp*Cr(CO)₃}₂(μ,η^1:1-P₄)] ( 1 ) towards Lewis acidic pentacarbonyl compounds of Cr, Mo and W is reported. The reaction of 1 with [W(CO)₄(nbd)] (nbd=norbornadiene) yields the complex [{Cp*Cr(CO)₃}₂(μ₃,η^1:1:1:1-P₄){W(CO)₄}] ( 2 ) in which 1 serves as a chelating P₄ butterfly ligand. In contrast, reactions of 1 with [M(CO)₄(nbd)] (M=Cr ( a ), Mo ( b )) result in the step-wise formation of [{Cp*Cr(CO)₂}₂(μ₃,η^3:1:1-P₄){M(CO)₅}] ( 3 a,b ) and [{Cp*Cr(CO)₂}₂-(μ₄,η^3:1:1:1-P₄){M(CO)₅}₂] ( 4 a,b ) which contain a folded cyclo-P₄ unit. Complex 4 a undergoes an unprecedented P₁/P₃-fragmentation yielding the cyclo-P₃ complex [Cp*Cr(CO)₂(η³-P₃)] ( 5 ) and the as yet unknown phosphinidene complex [Cp*Cr(CO)₂{Cr(CO)₅}₂(μ₃-P)] ( 6 ). The identity of 6 is confirmed by spectroscopic methods and by the in situ formation of [{Cp*Cr(CO)₂(tBuNC)}P{Cr(CO)₅}₂(tBuNC)] ( 7 ). DFT calculations throw light on the bonding situation of the reported products.     

Perfluormethyl-Element-Liganden. XVIII. Darstellung und spektroskopische Untersuchung von M(CO)5L und M(CO)4L2-Komplexen [L = MenP(CF3)3−n; n = 0–3; M = Cr,Mo, W]

Perfluoromethyl-Element-Ligands. XVIII. Preparation and Spectroscopic Investigation of M(CO)₅L and M(CO)₄L₂ Complexes [L = Me_nP(CF₃)_3?n; n = 0–3; M = Cr, Mo, W] M(CO)₅L and cis-M(CO)₄L₂ complexes, respectively [M = Cr, Mo, W; L = Me_nP(CF₃)_3?n; n = 0–3] are prepared reacting M(CO)₅ · THF or M(CO)₄norbor with L at room temperature. The cis-compounds isomerize above 50°C yielding the trans-complexes; the rate of isomerization increases with increasing number of CF₃ groups. Thermal reaction of M(CO)₆ (M = Cr, Mo, W) with P(CF₃)₃ yields M(CO)₅P(CF₃)₃ and trans-M(CO)₄[P(CF₃)₃]₂. Introduction of three P(CF₃)₃ ligands by reaction with M(CO)₃(cycloheptatriene) (M = Cr, Mo) proves unsuccessful; besides little M(CO)₅P(CF₃)₃ trans-M(CO)₄[P(CF₃)₃]₂ is formed. The new compounds are characterized by analytical and spectroscopic (n.m.r., i.r., MS) methods.     

Reactions of chromium,molybdenum and tungsten carbonyls with a tetradentate schiff base

Interaction of metal carbonyls M(CO)₆ (M?=?Cr, Mo and W) with the tetradentate Schiff base bis(salicylaldehyde)phenylenediimine (salphenH₂) was studied in THF. Under reduced pressure, reaction of salphenH₂ with M(CO)₆ (M?=?Cr, Mo) yielded Cr(CO)₂(salphen) 1 and MoO(CO)(salphen) 2. The complexes MoO₂(salphenH)₂ 3 and W₂O₆(salphenH₂) 4 were isolated from reactions in air. All the complexes were characterized by elemental analysis, mass spectrometry and IR and ¹H?NMR spectroscopy. Spectroscopic studies of the reported complexes revealed the proposed structures. The UV-vis spectra of the complexes in different solvents showed bands due to either metal-to-ligand or ligand-to-metal charge transfer. Thermal properties of the chromium and molybdenum complexes were investigated by thermogravimetric techniques.     

Chiral functionalized bisphosphine ligands: Transition metal complexes of 1,2-bis(tert-Butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12)

When rac- or meso-1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12) (1a or 1b) is reacted with [M(CO)₄(NBD)] (M = Cr, Mo, NBD = norbornadiene), [Mo(CO)₄(EtCN)₂] or [W(CO)₆], rac-[Cr(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (2), rac- or meso-[Mo(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (3a or 3b) and rac-[W(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (4) could be isolated as pure diastereomers. UV irradiation of 1 with [Cr(CO)₆] in moist THF proceeds with hydrolysis and formation of [Cr(CO)₄{1,2-(P(OH)^tBu)₂C₂B₁₀H₁₀}] (5) which contains the metal complex-stabilized phosphinous acid. Compounds 2–5 were characterized spectroscopically (¹H, ³¹P, ¹¹B, ¹³C NMR), by mass spectrometry and by X-ray structure determination.