Four-membered Metallocycle Research Articles

Unusual Four-Membered Metallocycles in Complexes of Main Group III Metals

Unusual Four-Membered Metallocycles in Complexes of Main Group III Metals

Mononuclear transition metal adamantane-1-carboxylates

A procedure was developed for the synthesis of mononuclear first row transition metal coordination compounds with adamantane-1-carboxylate (AdCO2), which allowed the synthesis of complexes NBu4[M(AdCO2)3], where MII = Mn, Ni, Co, Zn. The X-ray diffraction study showed that all AdCO2 act as chelating ligands, which is the main distinguishing structural feature of the synthesized compounds. The formation of four-membered metallocycles leads to a small O—M—O angle (58.4–63.0°), resulting in the distorted trigonal-prismatic environment of the central atom in the coordination anions [M(AdCO2)3]−. Under similar conditions of the synthesis, CuII forms the complex (NBu4)2[Cu(AdCO2)2(SO4)] existing in two differently colored modifications (green and light blue), which is due to a small difference in the environment of CuII in the solid state. Upon heating above 150°C, the light blue modification is transformed into the green modification. Using 1,3-diphenyltriazene (HL), it was demonstrated that the developed synthetic approach is applicable to the preparation of compounds, in which the coordination anions [ML3]− also contain only four-membered chelate metallocycles with the N—M—N angle tightened at the metal atom. The compounds NBu4[ML3], where MII = Co and Ni, were isolated in individual state and were structurally characterized.

Crystal-chemical role of malonate ions in the structure of coordination polymers

In the crystal structures of the malonate-containing compounds of d- or f-metals, the C3H2O 4 2− anions were found to exhibit 17 topologically different types of coordination to the metal atoms A, playing the role of mono-, bi-, tri-, or tetradentate ligands and forming one to seven O-A bonds. The C-C-C bond angle in the malonate ions changed from 103° to 126° and depended linearly on the dihedral angle (φCOO) between the planes of the two carboxyl groups of the anion. At φCOO 67°, they can form only four-membered metallocycles. The factors that influence the conformation of malonate ions in the structures of coordination polymers were discussed.

Structural diversity of four novel cadmium coordination polymers constructed by 1,4-bis(imidazol-1-yl)butane and anion ligands

The reaction of the flexible bis(imidazole) ligand 1,4-bis(imidazol-1-yl)butane (bimb) with corresponding Cd(II) salts (NCS −, dicyanamide (dca), N 3 - , ClO 4 - ) yields four new coordination polymers, from 1D to 3D networks, namely [Cd(bimb) 2(NCS) 2] n ( 1), [Cd(bimb)(dca) 2] n ( 2), [Cd(bimb)(N 3) 2] n ( 3) and {[Cd(bimb) 3](ClO 4) 2} n ( 4). In 1, each Cd(II) atom links two Cd(II) atoms by double bimb ligands and extends to form an one-dimensional chain structure containing the Cd 2(bimb) 2 22-membered metallocycle. In 2, double μ 1,5-dca bridges connect the Cd(II) atoms to form the zigzag [Cd(dca) 2] n chains and extend through bimb long bridges in four different directions alternatively to construct a novel three-dimensional network. In 3, double end-to-end (EE) and double end-on (EO) azide short bridges alternatively link Cd(II) atoms to form the [Cd(N 3) 2] n chains containing both eight- and four-membered metallocycles which further extend via bimb long bridges in four different directions alternatively to result a three-dimensional network. Compound 4 comprises two equivalent, mutually interpenetrating three-dimensional networks.

Adjusting the frameworks of polymeric silver(i) complexes with 2-aminopyrimidyl ligands by changing the counterions

The complexes [Ag2(L)2(SO4)]∞, (L = 2-aminopyrimidine) 1, [Ag(L)1.5(ClO4)]∞, 2, and [Ag(L)(OAc)·2H2O]∞, 3, were prepared by layering the aqueous solution of the corresponding Ag(I) salt with L in ethanol, while [Ag(L′)(NO3)]∞, 4, and [Ag(L′)(ClO4)·H2O]∞, 5, were prepared by refluxing AgNO3 and AgClO4, respectively, with 2-amino-4,6-dimethylpyrimidine (L′) in H2O. Reaction of Ag2SO4 with L′ in methanol afforded the complex [Ag4(L′)2(SO4)2(H2O)4]∞, 6. In complex 1, the L ligands are coordinated to the Ag(I) metal centers in new tridentate fashions, forming 2-D pleated molecular sheets which are interlinked by the SO42− anions to form a 3-D layer structure. Complex 2 forms a pleated molecular sheet consisting of twenty four-membered metallocycles, involving six Ag ions which are bridged by six L ligands through the pyrimidyl nitrogen atoms. Complex 3 forms linear chains with sinusoidal geometry, which are interlinked through extensive Ag⋯Ag interactions (Ag⋯Ag = 3.102 A) to form 2-D wavy rectangular grids. Complex 4 forms single-strained helical coordination polymers, which are interlinked through a series of Ag⋯O interactions (2.667 and 2.699 A) to form 2-D chair like grids. The silver atoms of 5 are bound to the nitrogen atoms of two symmetry-related L′ ligands in a distinctly non-linear geometry, forming zigzag chains. The structure of 6 consists of clusters of the formula [Ag8(L′)4(SO4)4(H2O)8], which are interlinked through L′ ligands to form 2-D sheets. The μ1-O, μ2-O′- bonding mode of the SO42− anion in complex 6 is unique for Ag(I) complexes. Their thermal properties have been investigated by using differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA)

New stable cyclopentadienyl iron(II) complexes containing 3,5-dimethylpyrazolyl phosphine: X-ray structure of [FeCp(CO) 2PPh 2(Me 2Pz)]BF 4

Very stable complexes of general formula [FeCp(CO) x Ph 2P(Me 2Pz)]BF 4, where x=1( 1)–2( 2) were prepared by room temperature reaction of the 3,5-dimethylpyrazolylphosphine ligand with [Fe 2(CO) 2(C 5H 5) 2]. When [FeCp(CO) 2Ph 2P(Me 2Pz)]BF 4 ( 1) was treated with (CH 3) 3NO·2H 2O, one coordinated CO was lost and complex 2 was formed. 1H-, 13C- and 31P-NMR spectra supported a structure of 2 with pyrazolyl ligand chelated to iron forming a four-membered metallocycle.

Formation of various polymeric frameworks by dicarboxylate-like ligands: Synthesis and crystal structures of polymeric complexes of sodium perchlorate with flexible double betaines

Three crystalline complexes of sodium perchlorate with different flexible double betaines [Na2(L1)(ClO4)(H2O)n](ClO4)n (1), [Na3(L2)(ClO4)3(H2O)2n] (2), and [Na(L3)(CH3OH)n]-(ClO4)n·xnH2O (x=0.25) (3) [−O2CCH2N+Me2−(CH2)n-N+Me2CH2CO2−,n=2 L1;n=3 L2;n=4 L3] have been synthesized and characterized by single-crystal X-ray structure analysis. Complex (1) comprises tetranuclear sodium units consolidated by betaine and aqua ligands, which are bridged by half of the ClO4− anions to form layers matching the (200) planes, the remaining uncoordinated ClO4− anions being accommodated between adjacent layers. Complex (2) possesses a double-layer polymeric structure with the sodium atoms bridged by ligand oxygen atoms to form columns running parallel to thea axis, which are interconnected by double-betaine ligands lying parallel to theac plane. All of the ClO4− groups and water molecules are coordinated to the metal atoms. In complex (3) the chains composed of alternating eight-membered and four-membered metallocycles are cross-linked by the betaine ligands, which lie in the (020) and (01/1) families of planes, to yield a three-dimensional network. All of the ClO4− groups and water molcules fill the resulting infinite channels running parallel to thea axis. Two unusual carboxylate coordination modes are identified, namelyμ3-O andhapto-3-O plushapto-2-O′ in (1) and (2), respectively.

Bidentate cyclic imido complexes of molybdenum(II). Preparation, solution behaviour and X-ray crystal structure

The complex [MoH4(dppe)2]1(dppe = Ph2PCH2CH2PPh2) in benzene or toluene reacted photochemically or thermally with organic cyclic imides, H[graphic omitted](O)[E = CH2CH2a, [graphic omitted]H b, [graphic omitted]H c, C6H4-1,2 d] to afford [[graphic omitted](O)}(dppe)2]2. NMR spectral study of the seven-co-ordinate complexes 2 showed that they have a fluxional pentagonal-bipyramidal structure in solution. The X-ray crystal structure of 2a[monoclinic, space group P21/a with a= 14.949(3), b= 28.691(13), c= 12.503(3)A, β= 103.22(17)°, Z= 4 and R= 0.0615] showed that the succinimido ligand is co-ordinated to the metal in a bidentate manner via nitrogen and oxygen atoms yielding a four-membered metallocycle.

Catalytic co-oxygenation of alkenes and other ligands by molecular oxygen at rhodium centres

Evidence from many facets of the catalytic co-oxygenation of terminal and cyclic alkenes under aprotic conditions at near ambient temperatures leads to mechanistic proposals for this process which takes place at some rhodium centres. Discussion is focused particularly on RhCl(Ph 3P) 3 (III) as the catalyst and on reactions in which the co-substrate is either Ph 3 or a second alkene residue. The proposals encompass the formation and expansion of a peroxy-metallocyclic intermediate formed from a Rh(III)peroxo complex, followed by contraction to give a four-membered metallocycle; it is suggested that these transitions are confined to three facially disposed centres. The apparently anomalous co-oxygenation of cyclic alkenes is explained by conformational features associated with the metallocycle contraction step. The basic mechanism may also apply to catalytic oxygenations of substrates other than alkenes by dioxygen at Group VIII transitionmetal centres.

Die Reaktion der unbeständigen Schwefeldiimide S(NR)(NH) (R = H, C(CH3)3, Si(CH3)3) mit den Halbsandwich-Komplexen CpW(CO)3H und Cp*W(CO)3H / The Reaction of the Unstable Sulfur Diimides S(NR)(NH) (R = H, C(CH3)3, Si(CH3)3) with the Halfsandwich Complexes CpW(CO)3H and CpsW(CO)3H

The unstable parent compound of the sulfur diim ides, S(NH)2 (1 ), and the labile monosubstituted sulfur diimides, S(NR)(NH) (R = tert-butyl (2) and trimethylsilyl (3)) react with the halfsandwich com plexes CpW (CO)3H (a) and Cp*W (CO)3H (b) under insertion into the W-H bond. The structures of the addition products (1a -3a, 1b -3b) are interpreted on the basis of a central four-membered metallocycle into which an acyl group and one of the N = S bonds are incorporated. The observation of two species in the 1H and 13C NMR spectra of 1a -3a and 2b, 3b is ascribed to interactions with the solvent.

Die Addukte von Bis(di-tert-butylphosphino)- und Bis(di-tertJ-butylarsino)schwefeldiimid mit Cyclopentadienyl-hydridometall- Komplexen CpM(CO)3H (M = Cr, Mo, W) / The Adducts of Bis(di-tert-butylphosphino)- and Bis(di-tert-butylarsino) Sulfur Diimides with Cyclopentadienyl Hydridometal Complexes CpM(CO)3H (M = Cr, Mo, W)

The new sulfur diimides S(NPBut 2)2 (a) and S(NAsBut 2)2 (b) react with the hydrido- metal complexes CpM(CO)3H (M = Cr (1), Mo (2), and W (3)) to give 1:1 adducts which contain a three-electron acyl-chelate ligand. Only one of the two PBut 2 and AsBut 2 sub­stituents, respectively, becomes coordinated to the metal; the hydrido ligand of the starting complex (CpM(CO)3H (1-3) is transfered to a N atom of the sulfur diimide system. The structures of the adducts (1a-3a and 1b-3b) are discussed on the basis of their infrared and 1H, 13C, and 31P NMR spectra. The X-ray analysis of 3a confirms the presence of a four-membered metallocycle containing W, C(acyl), N, and P.**

A four-membered osmium metallocycle from inter-ligand reaction between thiocarboxamido- and thiocarbonyl ligands. Structure of [formula omitted]NMe ptolyl)H(CO) (PPh 3) 2.

The thiocarboxamido-thiocarbonyl cation, [Os(n 2-SCNMeptolyl)(CS)(CO)(PPh 3) 2] +, upon reaction with NaBH 4, forms Os(CS 2C NMeptolyl)H(CO)(PPh 3) 2 through an inter-ligand reaction; x-ray crystal structure analysis of Os(CS 2C NMeptolyl)H(CO)(PPh 3) 2 confirms the presence of a four-membered metallocycle and further reaction with MeI produces what is formally a chelate di-carbene ligand in [ Os(C(SMe)SC NMeptolyl)H(CO)(PPh 3) 2] +.

Intramolecular metalation with methylmanganese and methylrhenium carbonyl complexes. Crystal and molecular structure of tetracarbonyl-2-bis(p-tolylphosphino)-5-methylphenylmanganese, (CH3C6H4)2PC6H3(CH3)Mn(CO)4, internal aromatic metalation product involving a four-membered metallocycle

Intramolecular metalation with methylmanganese and methylrhenium carbonyl complexes. Crystal and molecular structure of tetracarbonyl-2-bis(p-tolylphosphino)-5-methylphenylmanganese, (CH3C6H4)2PC6H3(CH3)Mn(CO)4, internal aromatic metalation product involving a four-membered metallocycle