Molecular Structures Of 2b Research Articles

Synthesis and Reactivity of “Bismuthinidene” Compounds and the Formation of Bi1 Chelate Complexes

Treatment of [Cp′Mn(CO)2THF] (Cp′C5H4Me) with BiCl3 at 20°C affords the “bismuthinidene” species [Cp′‐ (CO)2Mn]2BiCl (1b) and very small amounts of the “star‐type” compound [Cp′(CO)2Mn]3Bi2 (2). Higher yields of both compounds are obtained from the reaction of BiCl3 with [Na] [Cp′(CO)2MnSi(C6H5)3‐]. The molecular structure of 1b has been determined by an X‐ray diffraction study, which shows that the bismuth atom, having a trigonal‐planar coordination geometry, is bonded to two manganese atoms and one chlorine atom. There are weak interactions between the molecules of 1b in the solid state thus forming infinite spiral chains of “inidene” complexes. Compound 1b reacts with NaI to afford the iodine‐substituted species [Cp′(CO)2Mn]2BiI (3). Displacement of the chloride substituent from 1b by anionic chelating ligands AB− is also possible; 1b reacts with tropolonate, 8‐oxoquinolate, or 8‐mercaptoquinolate to form the bismuth(I) chelate compounds [CP′(CO)2Mn]Bi − AB (5a–c). The molecular structure of 5b has been determined by X‐ray crystallography which shows the bismuth atom in a pseudo trigonalbipyramidal geometry with the nitrogen atom lying above the plane defined by the two manganese and the oxygen atoms in an apical position. The molecular structure of 5c has also been determined, and although the numerical values are not very accurate, the coordination geometry of the bismuth atom is seen to be intermediate between pseudo trigonalbipyramidal and distorted tetrahedral. Abstraction of a chloride ligand from 1b by Me3SiOSO2CF3 affords the cationic cumulene‐type complex [Cp′(CO)2MnBiMn(CO)2Cp][CF3SO3] (6a). Dichloromethane solutions of 6a are not stable at room temperature but may be treated with 2,−2′‐bipyridine (bpy) to afford the stable adduct [{CP′(CO)2Mn}2Bi(bpy)][CF3SO3](7). The molecular structure of 7 has been determined by X‐ray analysis, and – similarly to 5c, although the numerical values are not very accurate – the overall geometry has been determined unequivocally. The bismuth atom is shown to have a distorted tetrahedral geometry, thus being ligated by two manganese atoms and the two nitrogen atoms of the bpy ligands.

Reaction of Ru 3{μ-H, μ-OCNMe 2}(CO) 10 with diarylacetylenes; synthesis and subsequent reaction of a {μ-carboxamido, μ-σ,π-vinyl}-hexacarbonyl diruthenium complex with propyne. Crystal and molecular structures of Ru 2{μ-OCNMe 2,μ-σ,π-C( p-tol)CH( p-tol)}(CO) 6, and of Ru 2{μ-OCNMe 2,μ-σ,π-C(CH 3)C(H)C( p-tolyl)CH( p-tolyl)}(CO) 6 ( p-tol = p-CH 3C 6H 4)

The complex Ru 3{μ-OCNMe 2,μ-H}(CO) 10 ( 1) is observed to react with diphenylacetylene ( 2a), di( p-tolyl)acetylene ( 2b), or di( p-anisyl)acetylene ( 2c), at 23° C in hexane solution over a period of 12 h to give Ru 2{μ-OCNMe 2,μ-σ,π-C(Ar)CH(Ar)}(CO) 6, Ar = Ph ( 3a), p-CH 3C 6H 4 ( 3b), or p-CH 3OC 6H 4 ( 3c). Principal by-products are Ru 3(CO) 12 and the acetylene oligomerization complexes {η 5-(OC) 3 RuC(Ar)C(Ar)C(Ar)C (Ar)}Ru(CO) 3, Ar = C 6H 5 ( 4a), Ar = p-tolyl, CH 3C 6H 4 ( 4b), Ar = p-anisyl, CH 3OC 6H 4 ( 4c). Variable temperature 13C NMR of 3a, 3b, and 3c indicates the presence of two rapidly interconverting isomers in solution, one with geminal and the other with vicinal bridging groups. Complex 3b is observed to react with propyne at 23° C in hexane over a period of 4 h giving as principal product Ru 2{μ-OCNMe 2,μ-σ,π-C(CH 3)C(H)C( p-tolyl)CH( p-tolyl)}(CO) 6, 5. The crystal and molecular structures of 3b and 5 have been determined using graphite-monochromatized Mo- K α radiation on a Huber four circle diffractometer under control of a VAX 11/750 computer. Complex 3b crystallizes in the monoclinic space group P2 1/ a; cell dimensions a = 20.1744(23), b = 7.3166(8), c = 18.9413(22) Å, and β = 93.2730(31)° and Z = 4, V = 2786.12 Å 3; ρ(calc.) = 1.55 g cm −3. A total of 3923 unique reflections with I > 3σ( I) were used in the refinement; final discrepancy indices, R = 0.057 and R w = 0.071. The crystal consists of discrete molecules of the complex in which the metal-metal separation Ru(1)Ru(2) = 2.739(1) Å. The two bridging groups, namely {μ-σ,π-C(50)(Ar)C(40)H(Ar)} and {O(30)C(30)NMe 2}, are seen to be attached to the two metal centers in a vicinal arrangement with a near octahedral arrangement of σ-bonded atoms around each metal. Bond distance parameters for the bridging groups are (Å): Ru(2)O(30) = 2.117(5); O(30)C(30) = 1.283(8); Ru(1)C(30) = 2.106(7); Ru(1)C(50) = 2.324(7); Ru(1)C(40) = 1.410(9); Ru(2)C(50) = 2.081(7); C(40)C(50) = 1.410(9). Complex 5 crystallizes in the monoclinic space group P2 1/ c with cell dimensions: a = 10.421(4), b = 33.157(10), c = 8.896(3) Å, β = 90.34(3)° and Z = 4, V = 3078 Å 3; ρ(calc.) = 1.49 g cm −3. The structure was solved by the heavy atom method. A total of 3159 unique reflections with I > 3σ( I) were used in the refinement; final discrepancy indices, R F = 0.085 and R wF = 0.110. Complex 5 consists of two tricarbonyl ruthenium fragments joined by a strong RuRu bond, 2.726(2) Å, accompanied by a bridging carboxamido group and a bridging σ,π-group (C(CH 3)C(H)R (R = C( p-tolyl)C(H) p-tolyl) in a sigma-geminal arrangement. This type of complex is perceived as a common intermediate to the oligomerization products 4a, 4b, 4c observed in the present and previous studies, and the complex Ru 2{μ-OCNMe 2, μ-OCC(Me)CMe(η 2-CMeCHMe)}(CO) 5, observed in a previous study.

Preparation, crystal structure and reactions of a new spin-labelling reagent, cis-3,5-dibromo-4-oxo-2,2,6,6- tetramethylpiperidin-1-yloxy : Crystal structure of a derived bis-nitroxide

Methods for the preparation of cis - 3,5 - dibromo - 4 - oxo - 2,2,6,6 - tetramethylpiperidin -1 - yloxy ( 2b) and its use as a convenient, selective spin-labelling reagent for amino functions, are described. The crystal and molecular structures of 2b and the bis-nitroxide 4 - [(2',2',5',5' - tetramethylpyrrolin -1 - yloxy) - 3' - carbonyloxy] - 2, 2,6,6 - tetramethyl - 3,5 - dibromo - 3,4 - dehydropiperidin - 1 - yloxy ( 3) [obtained on treatment of 2b with triethylamine] have been determined by conventional heavy-atom techniques. In 2b the individual molecules have mirror symmetry with the bromine atoms equatorial. The N-O bond length is 1.278(5) Å, CN̂C is 125.1(3)° and the N-O bond makes an angle of 24.2° with the CN̂C plane. In 3 there are two different nitroxide groups. The pyrrolinyloxy ring is virtually planar with a N-O bond length of 1.252(13) Å and CN̂C of 113.1(10)°. The 6 -membered ring exists in a sofa conformation with a pseudoaxial Br atom. Its nitroxide group is tetrahedrally distorted. The N-O bond length is 1.268(15) Å, CN̂C is 121.7(10)° and the N-O bond makes an angle of 16.0° with the CN̂C plane. The packing of 3 is dictated by a short Br... .O secondary bond of 3.09(1) Å, 0.28 Å less than the sum of the van der Waal's radii resulting in dimeric units related by a centre of symmetry.