Metallacyclic Ring Research Articles

Unprecedented Two-Dimensional Polymers of Mn(II) with TCNQ-• (TCNQ = 7,7,8,8-Tetracyanoquinodimethane)

The concept of combining in one “hybrid” the special properties of individual inorganic and organic components is a topic of major interest in the materials community.1 In one approach, researchers are coassembling transition metal spin centers and organonitrile radicals into covalent networks,2,3 efforts that have unearthed extraordinary materials including highly metallic polymers of Cu with DCNQI (DCNQI ) N,N′-dicyanoquinonediimine),4 an electrically bistable material of Cu with TCNQ (TCNQ ) 7,7,8,8-tetracyanoquinodimethane),5 and a bulk ferromagnet of V with TCNE (TCNE ) tetracyanoethylene).6 With the exception of the DCNQI systems, however, X-ray structures of these intriguing compounds have not been obtained. Clearly, the main obstacle to be overcome in this chemistry is rapid precipitation of the products, which are typically far too insoluble to allow for recrystallization. As part of our investigation into the use of homoleptic acetonitrile cations as precursors for new materials, we discovered that the compounds [M(CH3CN)6][BF4]2 (M ) Fe, Mn, Co, and Ni) react with 2 equiv of [Bu4N][TCNQ] in CH3CN to yield microcrystalline products.7 While attempting to grow single crystals of the Mn compound, it was found that two entirely different products are formed in the presence of MeOH. Herein we report the X-ray structures, infrared spectra, and magnetism of two novel metallopolymers in which manganese ions are involved in unprecedented arrangements with ligands derived from [TCNQ]-•. Rapid mixing of methanolic solutions of [Mn(MeCN)4][BF4]2 and [Bu4N][TCNQ] instantaneously yields a purple microcrystalline solid formulated as Mn(TCNQ)2(MeOH)2. Slow diffusion of the parent compounds in MeOH leads to blue triclinic parallelepipeds of [Mn(TCNQ-TCNQ)(MeOH)2‚MeOH]∞ (1) (TCNQ-TCNQ ) σ-dimerized [TCNQ]-•) are formed.9a A crystallographic study revealed that 1 is composed of a 2-D network of six-coordinate Mn(II) ions equatorially bound to the four outer nitrile groups of the unusual [TCNQTCNQ]2ligand (Figure 1). The tetradentate dianion is nonplanar which leads to a staircase motif, with each “step” consisting of infinite chains of Mn(II) ions joined by 12membered metallacyclic rings involving cis-nitriles that lie in the same plane. A labeled diagram of a portion of 1 is given in Figure 2a, and a packing diagram of the layers is depicted in Figure 2b. The novel 2-D structure is stabilized by extensive interlayer hydrogen bonding that involves axial MeOH ligands and interstitial MeOH molecules situated between the layers (linear O1‚‚‚O2 ) 2.629 A and bent O1‚‚‚O2′ ) 2.983 A). Purple monoclinic needles of [Mn(TCNQ)(TCNQ-TCNQ)0.5(MeOH)2]∞ (2) are formed by slow diffusion of the reactants in a MeOH/MeCN mixture.10a Crystals of 2 also exhibit a 2-D structure, but in this case the Mn(II) centers are coordinated to tetradentate [TCNQ-TCNQ]2and bidentate [TCNQ]-• ligands (Figure 3a); the latter act as bridging ligands through the 1,2dicyano positions with the two unligated NtCgroups pointing outward from the edges of the zig-zag layers towards axial MeOH ligands in the adjacent layers (N3‚‚‚O2A ) 2.834 (8) A and N4‚‚‚O1A ) 2.846 (8) A). These hydrogen bonds serve to stabilize a densely packed, interdigitated arrangement of layers as shown in Figure 3b. The importance of the current X-ray structures lies in the fact that they are only the second and third crystallographically determined binary materials of TCNQ since their discovery in 1962.11a Prior to the present results, the only related structurally characterized example is [Ag(μ4-TCNQ)]∞, which consists of tetrahedral Ag(I) ions bridged by spiral columns of μ4-[TCNQ] groups that stack at ∼3.5 A along the a axis.12a There are several known complexes of Mn(II) with TCNQ behaving as a ligand,13,14 but the only extended structure is a 1-D polymer of Mn with [TCNQ]2bridges and Schiff base coligands.12b To our knowledge, however, there are no structures of coordination compounds with [TCNQ-TCNQ]2ligands. In fact, that [TCNQ-TCNQ]2entity has only been documented three previous times and in these instances it behaves as an outersphere anion.14 The C-C bonds of 1.659(10) and 1.635(10) A (f-f′ in Figure 1) that join the [TCNQ]-• units in 1 and 2 are long, but obviously significant since the C atoms involved are

XIII. Synthese und Eigenschaften von [Li(TMEDA)] 2Pt(CH 2CMe 2CMe 2CH 2 ) 2( 1) ; Vergleich der Zersetzungstemperaturen von Metallacyclopentan-Komplexen des Pt(II) und Ni(II) des Typs ( 1) mit und ohne β-Wasserstoff; Kristallstruktur von (COD) PtCH 2SiMe 2SiMe 2CH 2 ( 8)

The air-sensitive complex [Li(TMEDA)] 2 Pt(CH 2CMe 2CMe 2C H 2 (1) was synthesized in 50% yield by treatment of (COD)PtCl 2 with LiCH 2CMe 2CMe 2CH 2 Li. This “at-complex” was characterized by elementary analysis as well as by 1H and 13C NMR spectroscopy. DTA investigations showed the following thermal decomposition temperature: T dec. = 163° C. This decomposition temperature is significantly lower than those of the complexes [Li(TMEDA)] 2 Pt(CH 2CHRCHRC H 2) 2 (R=H ( 5), (R = HT dec. = 249°C; R = CH 3 ( 6), [Li(TMEDA)] 2 Ni(CH 2CMe 2CMe 2C H 2) 2 (R = H ( 3), T dec. = 182°C; R = CH 3 ( 4), T dec. = 172°C). Attempts to prepare an “at-complex” containing heteroatoms in the metallacyclic ring adding diethyl ether solution of LiCh 2SMe 2SMe 2CH 2Li ( 7) to CODPtCl 2 unsuccessful. The reaction gave (COD) PtCH 2SiMe 2PtCH 2SiMe 2C 2 ( 8) (yield: 80%). The complex was characterized by mass spectroscopy and X-ray diffraction. The crystal data and the final R values are as follows: crystal system: monoclinic, space group P2 1/ n with cell parameters a = 6.369(1) A ̊ , b = 20.016(2) A ̊ , c = 12.913(2) A ̊ , β = 94.42(1)°, Z = 4, R = 0.039, R w = 0.047. The average distance PtC (in the 1-platina-3,4-disilacyclopentane ring) is 2.063(7) Å and the angle CH 2PtCH 2 is 86.2(3)°.

Reaction of [Os3(µ-H)2(CO)9(µ3-CNC5H4CHCH2)] with phenylacetylene. A novel type of alkylidyne–alkyne coupling in a triosmium alkylidyne cluster

Reaction of the alkylidyne cluster [Os3(µ-H)2(CO)9(µ3-CNC5H4CHCH2)]1 with the unsymmetrical alkyne PhCCH occurred under thermal conditions affording two pairs of geometrical isomers [Os3(µ-H)(CO)9{µ3-η3-PhCCHC(CHCHPh)}]2a(30%), [Os3(CO)9(µ3-η1,η2,η2,η1-PhCHCHCH-CHCPh)]2b(24%), [Os3(CO)7{µ-η2,η3-CH2CHC(Ph)CHCPh}{µ3-η2-C(O)C(Ph)CH}]3a(8%), [Os3(CO)7{µ-η2,η3-PhCHCHC(Ph)CHCH}{µ3-η2-C(O)C(Ph)CH}]3b(6%) and the known cluster [Os3(µ-H)(CO)9{µ-C(H)NC5H4(η2-CHCH2)}]4(7%). The same reaction, carried out at room temperature in acetone, yielded another new cluster [Os3(CO)8(µ-η2-PhCCH2)(µ3-η2-CHCPhCH)]5 as a major product (34%). All the compounds have been fully characterised by spectroscopic and X-ray diffraction methods. The structure of 2a reveals that the methylidyne carbon in the ‘Os3C’ core couples with two phenylacetylene molecules to form a novel C5 hydrocarbyl co-ordinated in an allyl fashion on the trimetallic surface. Cluster 2b, an isomer of 2a, contains a cis,cis-1,5-diphenylpenta-1,3-diene ligand on a triangular array of Os atoms which, together with one of the osmium atoms forms an osmacyclohexa-2,4-diene ring with two localised double bonds. The structures of both 3a and 3b show the coupling of three alkyne molecules with 1, resulting in the formation of two discrete organic fragments. An interesting feature in both compounds is the formation of a keto ligand with a µ3-η2-co-ordination mode, which is derived from the coupling of one carbonyl ligand and a phenylacetylene molecule. The other fragment adopts a µ-η2,η3-co-ordination mode with a π and a η3-allyl bond to give a metallacyclic ring system. The two complexes are isomeric and differ only in the spatial positions of the phenyl substituents in the C5 hydrocarbyl fragments. The structure of 5 contains a σ,π-vinyl group with a µ-η2-bonding mode and an allyl fragment with a µ3-η3-co-ordination mode. A proposed mechanism which involves the cleavage of the N–C(alkylidyne) bond in 1, resulting in the formation of a µ3-carbido species ‘[Os3(µ-H)2(CO)9(µ3-C)]’ or a µ-alkylidene fragment ‘[Os3(µ-H)(CO)9(µ-CH)]’ as the intermediate is put forward to explain the unusual coupling reaction sequence. The reaction of 1 with p-tolylacetylene in refluxing n-hexane was studied to support the suggested mechanism and another two pairs of geometrical isomers were fully characterised with the crystal structure of [Os3(CO)9(µ3-η1,η2,η2,η1-MeC6H4CHCHCHCHCC6H4Me)]6b determined. The basic hydrocarbyl skeleton on the Os3 triangle in 6b is essentially the same as in the analogous compound 2b except for the presence of two methyl groups on the phenyl rings. This precludes the existence of the original pyridine ring in the newly formed clusters.

Nucleophilic additions to palladium(II)-activated CC bonds: Synthesis of cyclopalladated 8-substituted quinoline derivatives

8-Vinylquinoline and α-methyl-8-vinylquinoline have been prepared in 40–67% overall yield from 8-methyl- and 8-ethyl quinoline, respectively. These unsaturated compounds undergo nucleophilic addition with carbon and oxygen nucleophiles at the terminal vinyl carbon atom in the presence of Pd 11 compounds affording, exclusively, five-membered metallacyclic rings.

Stereoselective alkyne insertion into a bridging hydride at a diiron centre: cis–trans isomerisation and metallacycle formation

Addition of the activated alkyne dimethyl acetylenedicarboxylate (dmad) to [Fe2(CO)4(µ-H)(µ-CO)(µ-PPh2)(µ-dppm)]1(dppm = Ph2PCH2PPh2) afforded the σ-η vinyl complex cis-[Fe2(CO)4{µ-C(CO2Me)CH(CO2Me)}(µ-PPh2)µ-dppm)]2. Crystallography showed that the insertion is stereo-selectively cis, with the phosphorus-containing ligands also adopting a cis configuration. Ultraviolet irradiation of 2 resulted in slow conversion into a second isomer, trans-[Fe2(CO)4{µ-C(CO2Me)CH-(CO2Me)}(µ-PPh2)(µ-dppm)]3, which still retains the cis arrangement of phosphines as shown by 31P NMR spectroscopy. This transformation is reversible, 3 slowly converting back into 2 at room temperature, a process which is accelerated upon heating. At temperatures of 80 °C, 2(and 3) was converted irreversibly into a third isomer [Fe2(CO4{C(CO2Me)CHC(OMe)O}(µ-PPh2)(µ-dppm)]4, containing a metallacyclic ring by virtue of metal co-ordination of an ester carbonyl. X-Ray crystallography revealed a trans vinyl orientation and a trans disposition of the phosphorus-containing groups.

New coordination environments for yttrium formed in situ by heterometallic bridging: Crystal structures of (C 5H 4SiMe 3)Y[(μ-OCMe 3)(μ-Me)AlMe 2] 2 and (Me 3SiCH 2)Y[(μ-CH 2) 2 SiMe 2][(μ-OR)Li(THF) 2] 2

The bimetallic yttrium complexes [(C 5 R 5)Y(μ-OCMe 3)(OCMe 3)] 2 react with aluminum and lithium organometallic reagents to give complexes containing new combinations of ligands held together by heterometallic bridging atoms. [(C 5H 4SiMe 3)Y(μ-OCMe 3)(OCMe 3) (OCMe 3)] 2, 1, reacts with AlMe 3 to form the mixed-metal mixed-ligand complex (C 5H 4SiMe 3)Y(μ-OCMe 3)(μ-Me)AlMe 2 ] 2, 2, which contains a formally seven-coordinate yttrium linked to two four-coordinate aluminum atoms by bridging methyl and tert-butoxide ligands. Complex 2 contains two four-membered YOAlM e rings. [(C 9H 7)Y(μ-OR)(OR)] 2, 3, reacts with LiCH 2SiMe 3 to give a mixture of products from which (Me 3SiCH 2)Y[(μ-CH 2) 2SiMe 2][(μ-OR)Li(THF) 2] 2, 4, can be isolated by crystallization from hexane/THF. Complex 4 contains a pentacoordinate yttrium atom ligated by a terminal CH 2SiMe 3 group two bridging tert-butoxide ligands, and the two bridging methylene moieties of a (μ-CH 2) 2SiMe 2 group. Each lithium atom is coordinated to two molecules of THF and the alkoxide and methylene bridges. The bridging groups combine to make three fused four-membered metallacyclic rings, two YOLiC rings and one YCSiC ring. The structures of 2 and 4 were determined by single crystal X-ray diffraction studies.

Metallacycle formation through the linking of an alkyne with phosphido and acetyl groups at an iron centre: X-ray structure of [Cp [formula omitted]}] (Cp =η 5-C 5H 5)

The diphenylphosphine ligand of [CpFe(CO)(PPh 2H)(COMe)] (Cp  η 5-C 5H 5) can be deprotonated with DBU (DBU = 1, 8-diazabicyclo[5.4.0]undec-7-ene) or n-butyllithium; subsequent alkylation with RI (R  Me, Et) gives the complexes [CpFe(CO)(PPh 2R)COMe)]. Reaction of the anionic phosphido complex with the electrophilic alkyne methyl propiolate (HOCCO 2Me) followed by reprotonation with CH 3COOH gives the vinylphosphine complex [CpFe(CO)(PPh 2CHCHCO 2Me) (COMe)], whereas a similar reaction sequence with dimethyl acetylenedicarboxylate (DMAD, MeO 2CCCCO 2Me) produces two isomers of the complex [Cp Fe(CO){Ph 2PCH(CO 2Me)C(CO 2Me)C(Me)O }], in which linking of the alkyne with both the phosphido and acetyl ligands has occurred to form a six-membered metallacycle. The structure of one of the two isomers has been determined by X-ray diffraction and shows that the metallacyclic ring is bound to the iron atom through the phosphorus and the carbonyl oxygen of the acetyl group, and adopts a boat conformation in the solid state.

Alkyne and carbonyl coupling reactions in dimanganese carbonyl complexes. The reactions of Mn2(CO)9(NCMe) with HC.tplbond.CCO2Me

Four compounds Mn[sub 2](CO)[sub 8][[mu]-O=C[C(H)=C(CO[sub 2]Me)][sub 2]], 2, 35%, (OC)[sub 4]Mn[trans-[mu]-HC=C(CO[sub 2]Me)]Mn(CO)[sub 5], 3, 3%, (OC)[sub 4]Mn[C(CO[sub 2]Me)=C(H)C(=O)C(H)=C(CO[sub 2] Me)C(H)=C(CO[sub 2]Me)]Mn(CO)[sub 4], 4, 20%, and (OC)[sub 4]Mn[C(CO[sub 2]Me)-C(H)C(=O)C(H)=C(CO[sub 2]Me) C(H) =CH(CO[sub 2]Me)], 5, 5% yield, were obtained from the reaction of Mn[sub 2](CO)[sub 9](MeCN), 1, with HC[triple bond]CCO[sub 2]Me in hexane solvent at 25[degrees]C. Compounds 3-5 are new. Compound 3 is a dimetalated olefin complex formed by the insertion of the alkyne into the metal-metal bond of 1. Compounds 4 and 5 were characterized by a single-crystal X-ray diffraction analysis. Compound 4 contains two metallacyclic rings (one five membered and one six membered) formed by the coupling of three alkynes to one CO ligand. In the five membered ring the oxygen atom of the CO-derived carbonyl group is coordinated to one of the metal atoms. The six membered ring was formed by one of the alkynes and a coordinated carboxylate group from one of the alkynes coupled to it. 9 refs., 2 figs., 7 tabs.

Niobium 1,4-diazabutadiene derivatives. Structure of (η5-Cp)NbCl2(tBuNCHCHNtBu)

Crystals of dichloro(η 5 -cyclopentadienyl)(N,N'-di-tert-butyl-1,2-ethanediimine-N,N')niobium were obtained by ligand exchange reaction between CpNbCl 2 (PMe 3 ) 3 and t BuN=CH-CH=N t Bu. The structure shows pseudo-octahedral coordination around the metal, with the chlorine ligands in cis positions relative to each other. The diimine ligand has an η 2 -coordination mode with the five-membered metallacyclic ring adopting an envelope conformation. The long C-N distance together with the short C-C one imply electronic delocalization over the chelate

A group 4 metallocene template synthesis of β,γ‐unsaturated ε‐hydroxy carboxylic acids

AbstractThe reaction of (butadiene)zirconocene with hexacarbonyltungsten gives the metallacyclic [(π‐allyl)zirconoxy]carbene complex 7. This reagent adds to a variety of ketones to yield chiral nine‐membered metallacyclic ring systems (8). These systems are thus formed by means of 1,4‐selective coupling reactions of 1,3‐butadiene with W(CO)6 and an organic carbonyl compound at the zirconocene template. The ketones subjected to react with 7 include benzophenone, methyl vinyl ketone, cyclopentanone, and 3‐methoxyestra‐1,3,5(10)‐trien‐17‐one (12). The coupling products of 7 with cyclopentanone (8c) and 12 (8d‐A) were characterized by X‐ray crystal structure analyses. Of the four possible diastereomeric nine‐membered metallacyclic coupling products of 7 with 12 a single isomer [8d‐A with (13'S,17'R,2,3,4‐pS) configuration] was formed with ≥98% selectivity and isolated in 95% yield. Treatment of the complexes 8 in tetrahydrofuran with water and pyridine N‐oxide very effectively removed both transition metals with the formation of the corresponding β,γ‐unsaturated ε‐hydroxy carboxylic acids. The overall reaction sequence has thus converted the steroid ketone 12 very selectively to 5‐[3‐methoxy‐17β‐hydroxyestra‐1,3,5(10)‐trien‐17α‐yl]‐(E)‐pent‐3‐enoic acid (10d)

Coupling of carbonyl to HC.tplbond.COEt in dimanganese carbonyl complexes

Three new compounds (OC)[sub 4]Mn[C(OEt)=C(H)C(=O)]Mn(CO)[sub 6], 1, Mn[sub 2](CO)[sub 8][[mu]-0=C(H)C(OEt)=O], 2, and Mn[sub 2](CO)[sub 8][[mu]-O=C[C(H)=C(OEt)][sub 2]], 3, were obtained in low yields when solutions of Mn[sub 2](CO)[sub 10]/ and HC[triple bond]COEt were irradiated (UV). The yield of 3 was significantly larger in the thermal reaction of Mn[sub 2](CO)[sub 9](NCMe) with HC[triple bond]COEt, but 1 was not formed. Compound 1 was characterized by a single-crystal X-ray diffraction analysis. The molecule contains a metallacyclic ring formed by the coupling of one molecule of HC[triple bond]COEt to one CO ligand. The oxygen atom of the CO group is coordinated to the metal atom. Compound 3 was converted to its bis-PMe[sub 2]Ph derivative Mn[sub 2](CO)[sub 6](PMe[sub 2]Ph)[sub 2] [C[mu]-O=C[C(H)=C(OEt)][sub 2]], 4, which was then characterized by a single-crystal X-ray diffraction analysis. Compound 4 contains two metallacyclic rings formed by the coupling of two HC[triple bond]COEt alkynes to one CO ligand. The oxygen atom of the carbonyl group is coordinated as a bridge between the two metal atoms. 15 refs., 4 figs., 13 tabs.

Facile alkyne coupling reactions in dirhenium carbonyl complexes

The complex (OC)[sub 4]Re[trans-[mu]-HC=C(CO[sub 2]Me)]Re(CO)[sub 5] (1) was converted to the reactive acetonitrile complex (OC)[sub 4]Re[trans-[mu]-HC=C(CO[sub 2]Me)]Re(CO)[sub 4](NCMe) (2) by reaction with Me[sub 3]NO in acetonitrile. Under an atmosphere of CO, complex 2 reacts with HC[triple bond]CO[sub 2]Me in refluxing CH[sub 2]Cl[sub 2] to yield the new complexes (OC)[sub 4]Re[[mu]-C(H)=C(CO[sub 2]Me)C(H)=C(CO[sub 2]Me)]-Re(CO)[sub 5] (3; 11%) and (OC)[sub 4]Re[C(H)=C(CO[sub 2]Me)C(H)=C(CO[sub 2]Me)C(H)= C(CO[sub 2]Me)]Re(CO)[sub 4] (4a,b; 49%, existing in solution as a mixture of isomers) by the head-to-tail coupling of two and three HC[equivalent to]CCO[sub 2]Me molecules, respectively. In the absence of CO only compound 4 and a small amount of the new compound [ovr Re(CO)[sub 4][C[sup 6]H[sub 2](CO][sub 2]Me)(CO[sub 2]Me)[sub 2]] (5;6%) were obtained. Complex 3 was converted into 4 by reaction with additional HC[equivalent to]CCO[sub 2]Me in the presence of Me[sub 3]NO. When heated to 98[degrees]C, 4 was transformed into 5 in 22% yield. Three of the products, 3, 4a, and 5 were characterized crystallographically. In complex 3 the two linked HC[equivalent to]CCO[sub 2]Me groups form a four-carbon chain between the metal-containing groups. One of the carboxylate substituents is also coordinated to form a five-membered metallacyclic ring. In complex 4a the metal-containing groups are joined by a six-carbon chain formedmore » from the three alkynes, and two of the carboxylate groups are coordinated to form five- and six-membered metallacyclic rings. The six-carbon chain in 4 was transformed into a 2,4,6-tris(methoxycarbonyl)phenyl group that is [sigma]-coordinated to the metal atom and also has one of its carboxylate groups coordinated. 10 refs., 3 figs., 6 tabs.« less

Synthesis and characterization of thiolato- and selenolato-platinum(II) complexes with bis(diphenylphosphino)alkanes

The complexes [Pt(ER)2(L–L)[ER = SPri, SPh, C6H4Me-p or SePh; L–L = Ph2P(Ch2)nPPh2(n= 1–3)] have been prepared and their ability to act as bidentate ligands towards other metal species demonstrated. Proton, 31P and 195Pt NMR spectroscopy have been employed to ascertain their structures. A single-crystal X-ray structure determination of [Pt(SePh)2(Ph2PCH2PPh2)] has established the mononuclear nature of the complex. The platinum atom is in a distorted square-planar environment with the selenium atoms and the chelating diphosphine ligand in a cis configuration. The four-membered PtPCP metallacyclic ring is non-planar.

The reaction of diphenylphosphine, PPh 2H, with an alkyne-bridged dicobalt carbonyl complex; the synthesis crystal structure and reactivity of the complex [CO 2{μ-C(CO 2Me)CHCO 2Me}(μ-PPh 2)(CO) 4

The reaction between [Co 2(μ-C 2(CO 2Me) 2)(CO) 6] and diphenylphosphine gives the mono- and di-substituted complexes [Co 2{μ-C 2}(CO 2Me) 2 (CO) 6- n (PPh 2H) n ] [ n = 1 ( 1), 2 ( 2)]. Thermolysis of ( 1) leads to phosphorus-hydrogen bond cleavage and formation of the phosphido-, vinyl-bridged complex [Co 2{μ-C(CO 2Me)CHCO 2Me}(μ-PPh 2(CO) 4] ( 3) together with the trinuclear cobalt complex [Co 3{μ-C 2(CO 2Me) 2}(μ-PPh 2(CO) 7 ( 4). An X-ray diffraction study of 3 reveals that one of the methylcarboxylate substituents of the vinyl ligand is coordinated via oxygen to cobalt, forming an almost planar M-C-C-C-O five-membered metallacyclic ring. The reactions of ( 3) with a tertiary phosphine and with phenylacetylene are described.

Synthesis and reactivity of phosphonato, phosphato and arsonato complexes of platinum(II)

Treatment of the complexes cis-[PtCl2L2](L = donor ligand) with phenylphosphonic acid, methylphosphonic acid, phenyl dihydrogenphosphate or phenylarsonic acid in the presence of an excess of silver(I) oxide in refluxing dichloromethane yielded the new metallacycles [[graphic omitted]}L2], [[graphic omitted]}L2], [[graphic omitted]}L2] or [[graphic omitted]}L2] respectively. The X-ray crystal structure of [[graphic omitted]}(PMePh2)2] showed the presence of a slightly puckered metallacyclic ring with the phosphoryl oxygen adopting an equatorial position. A decomposition product of the complex [[graphic omitted]}{P(CH2Ph)Ph2}2] in solution was shown, via an X-ray crystal structure determination, to be the diorthometallated complex cis-[[graphic omitted]Ph2)2].

Reactions of P2Ph4with alkyne-bridged dicobalt carbonyl complexes; crystal structures of [Co2{µ-C2(CO2Me)2}(µ-P2Ph4)(CO)4], [Co2{µ-PPh2CHCPhC(O)}(µ-PPh2)(CO)4] and [Co2{µ-PPh2C(O)CHCH}(µ-PPh2)(CO)3(PPh3)

The reactions of P2Ph4 with a variety of substituted alkyne complexes [Co2(µ-RCCR′)(CO)6] in toluene give the complexes [Co2(µ-RCCR′)(CO)5(P2Ph4)]1(R = R′= CO2Me 1a or Ph 1b; R = Ph, R′= H 1c and [Co2(µ-RCCR′)(µ-P2Ph4)(CO)4]2(R = R′= Ph 2b; R = Ph, R′= H 2c. All three derivatives of type 1 are cleanly converted into 2 on thermolysis. An X-ray diffraction study of 2a reveals a square-planar Co2P2 core with the symmetrical alkyne perpendicular to the Co–Co bond. Further thermolysis of complexes 2 produces [Co2(µ-PPh2CRCR′)(µ-PPh2)(CO)4]3(R = R′= CO2Me 3a or Ph 3b and [Co2{µ-PPh2CRCR′C(O)}(µ-PPh2)(CO)4]4c(R = H, R′= Ph). The structure of 4c has been determined by X-ray analysis. The PPh2CHCPhC(O) ligand forms a five-membered metallacyclic ring incorporating one Co atom and is π-bonded to the other Co atom. Complexes 3a and 3b are partially converted into 4a(R = R′= CO2Me) and 4b(R = R′= Ph) on treatment with CO. This reaction is reversed by heating 4a and 4b in solution or, more slowly, on standing at room temperature. The parent acetylene complex [Co2(µ-HCCH)(CO)6] reacts with P2Ph4 differently from the substituted derivatives to give as the principal product [Co2{µ-PPh2C(O)CHCH}(µ-PPh2)(CO)4]5b. The structure of the PPh3 derivative of this complex, [Co2{µ-PPh2C(O)CHCH}(µ-PPh2)(CO)3(PPh3)]6d, has been determined by X-ray diffraction.

Carbene ligand insertion into a metallacycle ring: a metallacyclopentadiene to metallacyclobutene conversion

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbene ligand insertion into a metallacycle ring: a metallacyclopentadiene to metallacyclobutene conversionJoseph M. O'Connor, Lin Pu, Susan Woolard, and Raj K. ChadhaCite this: J. Am. Chem. Soc. 1990, 112, 18, 6731–6732Publication Date (Print):August 1, 1990Publication History Published online1 May 2002Published inissue 1 August 1990https://doi.org/10.1021/ja00174a054RIGHTS & PERMISSIONSArticle Views233Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (313 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Stereochemische Aspekte bei metallacyclischen Neunring‐Zirconoxycarbenkomplexen aus (Butadien)zirconocen, Hexacarbonylwolfram und Ketonen oder Aldehyden

Stereochemical Aspects with Metallacyclic Nine‐Membered Zirconoxycarbene Complexes from Coupling (Butadiene)‐zirconocene, Hexacarbonyltungsten, and Ketones or AldehydesReaction of (butadiene)zirconocene complexes with M(CO)6 (M =Cr, W) and subsequently with ketones or aldehydes O=CR1R2 (R1, R2 = H, alkyl, alkenyl, or aryl) produces the metallacyclic nine‐membered zirconoxycarbene complexes (7a‐r. The complexes trans‐7 contain chiral metallacyclic ring systems. Starting from many ketones two diastereomeric compounds trans‐7 and trans‐7′ are obtained. From the dynamic 1H‐NMR spectra an activation barrier of ΔG(317K)=16.5 ± 0.4 kcal/mol has been estimated fro the trans‐7k [(2R*)(4,5,6‐pS*)] → trans‐7k′ [(2R*)(4,5,6‐pR*)] rearrangement. For the tert‐alkyl‐substituted nine‐membered metalacycles trans‐7f‐h only the respective (2R*)(4,5,6‐pS*) isomers have been found Starting from aldehydes with less sterically demanding alkyl groups mixtures of the trans‐7 [(2R*)(4,5,6‐pS*)] compounds and their cis‐7 isomers are obtained. Using the more bulky bis(tert‐butylcyclopentadienyl)zirconium moiety for coupling butadiene and W(CO)6 with simple aldehydes leads to a large excess of the trans‐isomers (e. g. R1 = H, R2 = i‐C3H7: trans‐7q: Cis7q = 90: 10).

Insertion and alkyne coupling reactions on early-transition-metal centers. Structures of CpTa(Me)(.sigma.2-ArCCAr)(.sigma.2-MeCNCMe3), CpMeTaC(Ph)C(Ph)C(Me)NCMe3, CpClMo(CPh)4 (Ar = p-tolyl)

CpTaCl{sub 2}({eta}{sup 2}-ArCCAr) (Ar = phenyl, p-tolyl) reacts with MeLi to give a CpTaMe{sub 2}({eta}{sup 2}-ArCCAr) (1) in high yield. Compound 1 reacts with {sup t}BuNC to give the {eta}{sup 2}-acetimidoyl derivatives CpTaMe({eta}{sup 2}-ArCCAr)({eta}{sup 2}-MeCN{sup t}Bu) (4) from the insertion of the isocyanide into one of the Ta-Me bonds. Gentle heating causes a quantitative conversion of 4 into metallacyclopentatriene derivatives, CpMeTaC(Ar)C(Ar)C(Me)N({sup t}Bu) (5), in which the alkyne has coupled to the acetimidoyl ligand with the formation of a new C-C bond. A similar coupling reaction is observed when CpMoCl(ArCCAr){sub 2} is heated in toluene; one of the products of this reaction is the metallacyclopentatriene CpClMo(CAr){sub 4} (7). The metallacyclic ring in 7 features two Mo=C double bonds (d = 1.94 {angstrom}) and the ring is folded (dihedral angle {approx equal}117{degree}). The crystal structures of 4b (Ar = p-tolyl), 5a (Ar = phenyl), and 7a{center dot}CH{sub 2}Cl{sub 2} (Ar = phenyl) have been determined: 4b, a = 10.518 (3) {angstrom}, b = 12.782 (3) {angstrom}, c = 18.816 (6) {angstrom}, {alpha} = {beta} = {gamma} = 90{degree}, V = 2,530 (1) {angstrom}{sup 3}, Z = 4, {rho}{sub c} =1.48 g/mL, space group P2{sub 1}2{sub 1}2{sub 1}, R = 0.027, R{sub w}more » = 0.026; for 5a, a = 9.540 (3) {angstrom}, b = 10.830 (4) {angstrom}, c = 11.932 (3) {angstrom}, {alpha} = 114.77 (2){degree}, {beta} = 91.47 (2){degree}, {gamma} = 91.68 (3){degree}, V = 1117.8 (6) {angstrom}{sup 3}, Z = 2, {rho}{sub c} = 1.59 g/mL, space group P{bar 1}, R = 0.045, R{sub w} = 0.044; 7a{center dot}CH{sub 2}Cl{sub 2} a = 10.039 (4) {angstrom}, b = 11.760 (3) {angstrom}, c = 12.674 (8) {angstrom}, {alpha} = 92.21 (4){degree}, {beta} = 87.35 (4){degree}, {gamma} = 104.05 (3){degree}, V = 1,449 (1) {angstrom}{sup 3}, Z = 2, {rho}{sub c} = 1.46 g/mL, space group P{bar 1}, R = 0.038, R{sub w} = 0.038.« less

Synthesis and conformation of 9,10-dihydroplatina-anthracenes: nuclear magnetic resonance and X-ray crystal structure studies

The platinacycles [Pt(C6H4CH2C6H4)L2](1a)–(1h)[L = PEt3, PMe3, PMe2Ph, PMePh2, or PPh3; L2= cyclo-octa-1,5-diene(cod), Ph2PCH2CH2PPh2, or Ph2PCH2PPh2] have been made and characterised by 1H, 13C, 31P, and 195Pt n.m.r. spectroscopy. The crystal structure of (1a; L = PEt3) has been determined, showing that the platinacycle has a boat conformation with a substantial dihedral angle (105.3°) between the aromatic rings. The boat conformation metallacyclic ring in complex (1a) is rigid on the n.m.r. time-scale up to at least 100 °C in dimethyl sulphoxide. The platinum(IV) complex [Pt(C6H4CH2C6H4)I2(PEt3)2](2) has been made by oxidative addition of I2 to (1a). Its crystal structure also shows a boat conformation, but the ring is very much flatter (dihedral angle 151.2°), and the octahedral geometry at Pt causes one PEt3 group to lie beneath the platinacycle. Complex (2) is fluxional at ambient temperatures due to rapid ring inversion but this can be frozen out at low temperatures and ΔG‡ of 41 kJ mol–1 estimated for the inversion process at Tc. Mean bond distances are: Pt–P 2.323(10)(1a), 2.386(3)(2), Pt–l 2.785(20)(2), Pt–C 2.05(1)(1a), 2.08(1)Å(2). Both crystals are monoclinic, space groups P21/n and P21/c: (1a), a= 10.748(2), b= 15.259(4), c= 14.885(4)Å, and β= 90.77(2)°; (2), a= 17.375(5), b= 9.681 (3), c= 19.192(5)Å, and β= 120.72(2)°. For (1a), R= 0.048 for 2.725 observed diffractometer collected reflections [I/σ(I) > 3.0], and for (2), R= 0.053 for 3 311 observed reflections.