Evaluation of dipolar shifts and paramagnetic anisotropy in penta coordinated cobalt(II) complexes

The isotropic proton shifts for the pyridine N-oxide and γ-picoline N-oxide protons have been observed in the penta coordinated adducts of these bases with bis[di(p-tolyl)dithiophosphinato] cobalt(II). The contribution to the observed shifts due to dipolar interaction has been calculated. From the dipolar shifts, it was ascertained that the pyridine N-oxide complexes have a bent structure in solution with a Co-O-N angle of 125°. An estimate of the paramagnetic anisotropy of the cobalt complex yields K_?-K_⊥ = 4244 × 10^?6 cm³/mole.     

Homoleptic phenyl isocyanide complexes of molybdenum and tungsten: zerovalent six-coordinate versus divalent seven-coordinate

Electrochemical and chemical oxidations of Mo(CNPh)₆ and W(CNPh)₆ have been shown to yield seven-coordinate [M(CNPh)₇]²⁺. These catons, stabilized as their PF₆^? salts, can be obtained in yields of 80%. The redox and substitution chemistry of these new complexes have been explored. A convenient synthesis of W(CNPh)₆ has been devised starting from W₂(dmhp)₄ (dmhp is the anion of 2,4-dimethyl-6-hydroxypyrimidine).     

Hydroformylation activity of multinuclear rhodium complexes coordinated to dendritic iminopyridyl and iminophosphine scaffolds

The synthesis of poly(propyleneimine)-iminopyridyl and iminophosphine rhodium(I) metallodendrimers, with rhodium coordinated to monodentate (N-donor) and chelating, heterobidentate (P,N) moieties respectively located on the periphery, has been accomplished in order to evaluate their potential as hydroformylation catalysts. Related mononuclear complexes were obtained in a similar manner to model the multinuclear complexes. The multinuclear rhodium(I) complexes were found to be effective catalyst precursors in the hydroformylation of 1-octene, achieving higher conversions, faster reaction rates and slightly enhanced catalytic activity when compared with analogous mononuclear rhodium complexes. Hydroformylation reactions using the tetra- and octanuclear rhodium complexes generally show a chemoselective formation of aldehydes, together with a small amount of isomerisation products.     

Homoleptic Cu-phosphorus and Cu-ethene complexes

Stable salts of the first homoleptic Cu-phosphorus and Cu-ethene complexes, [Cu(eta2-P4)2]+ and [Cu(eta2-C2H4)3]+, isolated by the aid of the weakly coordinating anion (WCA) [Al(OC(CF3)3)4]-, were obtained.     

Reactions of ytterbium and magnesium gallylene complexes with carbon dioxide and diphenylketene

Reactivity of ytterbium and magnesium complexes of gallylenes against carbon dioxide and diphenylketene has been assessed. Ytterbium complex of redox-active gallylene [{(dpp-bian)Ga}₂Yb(DME)₂] (dpp-bian = 1,2-bis[(2,6-diiso-propylphenyl)imino]acenaphthene) on treatment with CO₂ gives complex [(dpp-bian)Ga(DME)Me], while the treatment of magnesium-stabilized gallylene[{(dpp-bian)Ga}₂Mg(DME)₂] with Ph₂CCO affords cycloadduct [(dpp-bian)(Ph₂CCO)GaMe].     

Cyclotrimerization of monosubstituted alkynes in the presence of rhodium,molybdenum, and tungsten complexes

Conclusions Hydroxyquinoline complexes of rhodium in an alcoholic medium, as well as bis(ethylbenzene)molybdenum and nonacarbonylnitrosylhydrideditungsten catalyze the trimerization of phenylacetylene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 534–536, March, 1985.The authors wish to express their gratitude to Yu. S. Varshavskii and T. G. Cherkasova for providing the rhodium complexes, also to N. A. Ustynyuk for providing molybdenum and tungsten carbonyl derivatives.     

The formation of thioamide complexes of manganese,molybdenum and rhodium from organosilicon and organotin intermediates

The interaction of N-trimethylsilylthioacetanilide and N-phenyl-S-trimethyl- tinthioacetimidate, with carbonyl halides of molybdenum, manganese and rhodium afforded a range of N-phenylthioacetamido metal carbonyl complexes in which the group behaves as a chelating ligand, and also in two different ways as a bridging group in binuclear products.     

Intramolecular substitutions of square planar rhodium(I) cationic complexes of cis-dicarbonyl nitrogen coordinated tridentate

Four kinds of square planar cis-dicarbonyl-N, N-bis(2-pyridylethy1)-p-substituted-phenylarnino rhodium(I) are reported. The changes of their structures were analyzed by XPS, IR and NMR spectroscopy. The results show that the weak N→Rh coordinated bond can replace very soon the strong Rh-Cπ back donation bond to form tris-nitrogen coordinated complexes due to the steric effect when the temperature is over 50°C. This reaction is reversible. The bis-nitrogen coordinated structure of the complex recovered when put under the atmosphere of CO.     

Homoleptic 2-mercapto benzothiazolate uranium and lanthanide complexes

Treatment of [Ln(BH 4) 3(THF) 3] (Ln = Ce, Nd) with 3 and 4 mol equiv of KSBT in tetrahydrofuran (THF) led to the formation of [Ln(SBT) 3(THF)] and [K(THF)Ln(SBT) 4], respectively. The uranium(IV) compound [U(SBT) 4(THF) 2] was obtained from U(BH 4) 4 and was reversibly reduced by sodium amalgam into the corresponding anionic uranium(III) complex. The crystal structures of [Ln(SBT) 3(THF) 2] (Ln = Ce, Nd), [K(15-crown-5) 2][Nd(SBT) 4], [U(SBT) 4(THF)], and [K(15-crown-5) 2][U(SBT) 4(py)] show the bidentate coordination mode and the thionate character of the SBT ligand.     

Homoleptic tetranuclear complexes of divalent tin and lead tetraolates

Homoleptic tetranuclear complexes of divalent tin and lead tetraolates, M(4)(hfpt)(2) [M = Sn (1) and Pb (2); hfpt(4-) is an anion of 1,1,1,5,5,5-hexafluoropentane-2,2,4,4-tetraol], have been obtained in high yield from the corresponding (trimethylsilyl)amides. The solid-state structures of 1 and 2 contain discrete molecules in which a butterfly tetrahedron of metal atoms is sandwiched between two tetraolate ligands acting in tetradentate mode. The lone-pair Sn(2+) and Pb(2+) cations exhibit pyramidal coordination of four ligand oxygen atoms. A multinuclear NMR study unambiguously confirmed that metal tetraolates retain their polynuclear structure in solution of even coordinating solvents. An interesting example of the strong through-space coupling between (19)F of the tetraolate trifluoromethyl groups and (117/119)Sn or (207)Pb nuclei was found. Both compounds were shown to have clean, low-temperature decomposition that results in crystalline oxides SnO(2) and PbO, respectively, for 1 and 2. This work demonstrates the remarkable coordination properties of the tetraolate ligand that can be utilized for the preparation of a wide variety of poly- and heterometallic complexes. Decomposition studies revealed a great potential of metal tetraolate complexes as prospective molecular precursors for the soft chemistry approach to oxide materials.     

Intramolecular reaction of polymer coordinated cationic rhodium complex

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Trinuclear rhodium hydride complexes

Three novel trinuclear rhodium hydride complexes of the type {[Rh(PP*)H](3)(μ(2)-H)(3)(μ(3)-H)}[BF(4)](2) containing diphosphines Tangphos, t-Bu-BisP* and Me-DuPHOS have been synthesised. The new compounds are very stable. Their structures have been characterized by X-ray analysis in the solid state and by NMR-spectroscopic investigations in solution.     

Dihydrogen complexes of iridium and rhodium

A series of iridium and rhodium pincer complexes have been synthesized and characterized: [(POCOP)Ir(H)(H(2))] [BAr(f)(4)] (1-H(3)), (POCOP)Rh(H(2)) (2-H(2)), [(PONOP)Ir(C(2)H(4))] [BAr(f)(4)] (3-C(2)H(4)), [(PONOP)Ir(H)(2))] [BAr(f)(4)] (3-H(2)), [(PONOP)Rh(C(2)H(4))] [BAr(f)(4)] (4-C(2)H(4)) and [(PONOP)Rh(H(2))] [BAr(f)(4)] (4-H(2)) (POCOP = κ(3)-C(6)H(3)-2,6-[OP(tBu)(2)](2); PONOP = 2,6-(tBu(2)PO)(2)C(5)H(3)N; BAr(f)(4) = tetrakis(3,5-trifluoromethylphenyl)borate). The nature of the dihydrogen-metal interaction was probed using NMR spectroscopic studies. Complexes 1-H(3), 2-H(2), and 4-H(2) retain the H-H bond and are classified as η(2)-dihydrogen adducts. In contrast, complex 3-H(2) is best described as a classical dihydride system. The presence of bound dihydrogen was determined using both T(1) and (1)J(HD) coupling values: T(1) = 14 ms, (1)J(HD) = 33 Hz for the dihydrogen ligand in 1-H(3), T(1)(min) = 23 ms, (1)J(HD) = 32 Hz for 2-H(2), T(1)(min) = 873 ms for 3-H(2), T(1)(min) = 33 ms, (1)J(HD) = 30.1 Hz for 4-H(2).     

N-fused pentaphyrins and their rhodium complexes: oxidation-induced rhodium rearrangement

meso-Aryl-substituted pentaphyrins were isolated in the modified Rothemund-Lindsey porphyrin synthesis as a 22-pi-electron N-fused pentaphyrin ([22]NFP5) and a 24-pi-electron N-fused pentaphyrin ([24]NFP5), which were reversibly interconvertible by means of two-electron reduction with NaBH4 or two-electron oxidation with dichlorodicyanobenzoquinone (DDQ). Judging from 1H NMR data, [22]NFP5 is aromatic and possesses a diatropic ring current, while [24]NFP5 exhibits partial anti-aromatic character. Metalation of [22]NFP5 1 with a rhodium(I) salt led to isolation of rhodium complexes 9 and 10, whose structures were unambiguously characterized by X-ray diffraction analyses and were assigned as conjugated 24-pi and 22-pi electronic systems, respectively. In the rhodium(I) metalation of 1, the complex 9 was a major product at 20 degrees C, but the complex 10 became preferential at 55 degrees C. Upon treatment with DDQ, compound 9 was converted to 10 with an unprecedented rearrangement of the rhodium atom.     

Dicarbollide complexes of rhodium and ruthenium

The 7,8-B₉C₂H₁₁^2- ion reacts with (Ph₃P)₂Rh(CO)Cl to form (B₉C₂H₁₁)-Rh(Cl)(Ph₃P)₂. This rhodacarborane reacts with NaBPh₄ to produce (B₉C₂H₁₁-Rh(Ph₃P)(Ph₄B). The new metallocarboranes [(B₉C₂H₁₁)Rh(Ph₃P)(C₆H₆)]₂ and (B₉C₂H₁₁)Rh(H)(Ph₃P) were obtained from the reaction of B₉C₂H₁₁^2- and (Ph₃P)₃RhCl. The ruthenacarboranes (B₉C₂H₁₁)Ru(CO)(Ph₃P)₂ and (B₉C₂H₁₁-Ru(CO)₃ · 0.5C₆H₆ were prepared from (Ph₃P)Ru(CO)₂Cl₂ and [Ru(CO)₃Cl₂]₂ respectively.     

Acetyl substitution of the cyclopentadienyl ligand in molybdenum complexes; nucleophilic additions to coordinated allyl groups

An unusual acetyl substitution of the cyclopentadienyl ligand is observed during the synthesis of allyl(η⁵-Cp)Mo(CO)₂ (I) be nucleophilic displacement on Cl(allyl)Mo(CO)₂(NCMe)₂ with lithiocyclopentadiene according to Hayter. The origin of the acetyl group is established by deuterium labelling studies, and it is rationalized in terms of the activation of the coordinated acetonitrile to nucleophilic addition with LiCp. The X-ray crystal structure of (η⁵-AcCp)Mo(CO)₂(η³-allyl) (II) reveals a slightly distorted cyclopentadienyl ring and an effective enlargement (i.e., expanded locus) of the ligand as a result of acetyl substitution. The stereoelectronic consequences of the substituted cyclopentadienyl ligand (η⁵-AcCp) are found in the relative populations of the exo- and endo-conformations of the coordinated allyl ligands in both II as well as in its derived cation IV (η⁵-AcCp)Mo(CO)(NO)(η³-allyl)⁺ by comparison with their unsubstituted analogues I and III, respectively. The stereochemistry resulting from this steric change is also examined in the course of nucleophilic additions to the cationic allyl complexes IV with hydride, thiolate anions and carbanions.     

α-Pyridinecarboxylate complexes of rhodium

The complex Rh(pyc)(NBD) (pyc = α-pyridinecarboxylate anion, NBD = 2,5-norbornadiene) reacts with carbon monoxide with displacement of the diolefin and formation of Rh(pyc)(CO)₂. Addition of triarylphosphines to the latter compound causes the formation of complexes of the type Rh(pyc)(CO)[P(p-RC₆H₄)₃] (R = F, Cl, Me, MeO). The addition of iodine, bromine or methyl iodide to solutions of the monocarbonyl derivatives leads to the formation of RhX₂(pyc)(CO)[P(p-RC₆H₄)₃] (X = I, Br) and RhMeI(pyc)(CO)[P(p-RC₆H₄)₃] complexes.