PMe2 Ph Research Articles

Palladium(II), platinum(II), and platinum(IV) complexes containing trans-1,2-bis(diphenylphosphino)ethene or cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane: complete X-ray structural characterization of binuclear compounds

Several novel binuclear Pd II, Pt II, and Pt IV complexes of trans-1,2-bis(diphenylphosphino)ethene ( trans-dppen) or cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) have been prepared and characterized by X-ray diffraction methods, 195Pt{ 1H} and 31P{ 1H} NMR spectroscopy, FAB mass spectrometry, IR spectroscopy, elemental analyses and melting points. The X-ray structure and NMR parameters of [Pt 2I 4( trans-dppen) 2] ( 1) confirm that homobimetallic complexes of the type [M 2L 4( trans-dppen) 2] (M=Ni, Pd, Pt; L=Cl −, I −, CN −) contain two square planar coordination units joined by two trans-dppen bridges in the solid as well as in the solution state. An analogous structure type is retained in the Pt IV compound [Pt 2Cl 8( trans-dppen) 2] ( 2). In contrast to the corresponding Pt II complex of the new tetradentate phosphine dppcb, the X-ray structure of [Pd 2Cl 4(dppcb)] ( 3) reveals only one conformation. This can be explained by the longer Pd–P bonds compared with the Pt–P bonds and the weaker square planar stabilization energy in 3. In 3 dppcb acts as a binuclear tetraligate single-bridging ligand combining two square planar coordination centres. The reaction of Pd(CN) 2 with dppcb leads to [Pd 2(CN) 4(dppcb)] ( 4). The removal of the coordinated chlorides in 3 by AgBF 4 followed by subsequent treatment with NaNO 2 produces [Pd 2(NO 2) 4(dppcb)] ( 5). In an analogous reaction with 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy), [Pd 2(dppcb)(phen) 2](BF 4) 4 ( 6) and [Pd 2(dppcb)(bipy) 2](BF 4) 4 ( 7) are formed. The complexes 4– 7 show structure types corresponding to the X-ray structure of 3. The same is true for the treatment of 3 with PMePh 2 or PMe 2Ph, where [Pd 2(dppcb)(PMePh 2) 4](BF 4) 2Cl 2 ( 8) and [Pd 2(dppcb)(PMe 2Ph) 4](BF 4) 4 ( 9) are obtained. However, the X-ray structure of 8 reveals that the chlorides are coordinated in the solid state, and the crystal structure consists of trans-[Pd 2Cl 2(dppcb)(PMePh 2) 2](BF 4) 2 ( 10). The flexibility and stereochemical demands of dppcb in the compounds 3– 10 and related species are discussed in view of the possible application of Pd II complexes containing bidentate tertiary phosphine ligands as catalysts for the alternating copolymerization of ethene and carbon monoxide. In this respect dppcb can be regarded as a combination of two bidentate phosphines, where the cyclobutane ring corresponds to a relatively rigid ligand backbone. This produces strain in the five-membered rings of 3– 10 which is released by ‘envelope’-folding in the X-ray structures of 3 and 10.

Synthesis and characterisation of E,O-mixed donor (E=P, S or Se) ligand complexes of palladium(II) and platinum(II)

New palladium(II) and platinum(II) complexes with the hybrid ligands Ph 2PNHP(O)Ph 2, [Ph 2PNP(O)Ph 2] − or [Ph 2P(E)NP(O)Ph 2] − (E=S or Se) have been prepared and characterised. Hence reaction of the cyclometallated dimers [{Pd(μ-Cl)(C∼N)} 2] [C∼N=C 12H 9N 2 or C 13H 8N] with Ph 2PNHP(O)Ph 2 gave the mononuclear compounds [PdCl(C∼N){Ph 2PNHP(O)Ph 2- P}]. Chloride abstraction, or amine deprotonation, afforded [Pd(C∼N){Ph 2PNHP(O)Ph 2- P, O}][BF 4] or [Pd(C∼N){Ph 2PNP(O)Ph 2- P, O}] bearing a neutral or anionic P,O-chelating ligand, respectively. Reaction of [{Pd(μ-Cl)(C 9H 12N)} 2] with Ph 2PNHP(O)Ph 2 in CDCl 3 solution gave the known, rather unstable compound, [PdCl(C 9H 12N){Ph 2PNHP(O)Ph 2- P}]. Spectroscopic and analytical evidence presented here suggest that [PdCl(C 9H 12N){Ph 2PNHP(O)Ph 2- P}] undergoes amine deprotonation/PdC bond rupture to give an isomeric compound, tentatively assigned as [PdCl{Ph 2PNP(O)Ph 2- P, O}(NMe 2CH 2Ph)]. Bridge cleavage of [{Pd(μ-Cl)(C 12H 9N 2)} 2] with the unsymmetrical anions [Ph 2P(E)NP(O)Ph 2] − (E=S or Se) gave the square–planar complexes [Pd(C 12H 9N 2){Ph 2P(E)NP(O)Ph 2- E, O}] exclusively as one isomer (E trans to N). In a similar manner the new metal(II) compounds [PtCl{Ph 2P(E)NP(O)Ph 2- E, O}(PMe 2Ph)] (E trans to Cl) and [Pd(C 9H 15O){Ph 2P(E)NP(O)Ph 2- E, O}] (E trans to olefin double bond) were synthesised. All compounds were characterised by a combination of multinuclear NMR [ 1H, 31P{ 1H}, 195Pt{ 1H}], IR spectroscopy and elemental analyses. Furthermore, the X-ray structures of [Pd(C 12H 12N){Ph 2PNHP(O)Ph 2- P, O}][BF 4] and [Pd(C 12H 12N){Ph 2PNP(O)Ph 2- P, O}] are reported and reveal, upon amine deprotonation, π-delocalisation within the PNPO backbone of the anionic P,O-chelating ligand.

Organopalladium(IV) complexes containing phosphine ligands, and the structure of the platinum(IV) complex [PtMe 3(bpy)(PPh 3)][O 3SCF 3] (bpy=2,2′-bipyridine)

Solutions containing unstable organopalladium(IV) complexes of phosphines, [PdMe 3(bpy)(L)] + (L=PMePh 2, PMe 2Ph, PPh 3), are generated on reaction of PdIMe 3(bpy) with the phosphines in dichloromethane- d 2. The complex [PdMe 3(bpy)(PPh 3)] + may also be formed quantitatively on the reaction of PdMe 2(bpy) with methyl triflate and triphenylphosphine in acetone- d 6. A solution of the platinum(IV) analogue [PtMe 3(bpy)(PPh 3)][O 3SCF 3] is formed following a similar procedure and isolated as crystals on reaction of PtIMe 3(bpy) with silver triflate followed by PPh 3. An X-ray structure determination of the platinum(IV) complex shows the fac-PtMe 3 configuration for octahedral [PtMe 3(bpy)(PPh 3)] +, and supports the assignment of identical structures for the unstable palladium(IV) complexes from comparison of 1H- and 13P-NMR spectra of palladium(IV) and platinum(IV) complexes.

The preparation and characterisation of platinum and palladium phosphine thiocarbonate complexes M(PR 3) 2(CS 3) and Pt(PR 3) 2(CSeS 2)

Reaction of CS 2 with NH 3(liq) gives the (CS 3) 2− dianion which undergoes in situ reaction with MCl 2(PR 3) 2 to give M(PR 3) 2(CS 3). X-ray analysis of four examples (M=Pt, PR 3=PMe 3, PMe 2Ph, PPh 3, dppp) reveals square planar coordination with the [CS 3] 2− dianion being effectively in the same plane as the coordination sphere. The first example of a [CSeS 2] 2− complex is also reported.

Syntheses and structures of di- and trinuclear heterometallic complexes with nitrido bridges between rhenium and titanium

[TiCl 4(MeCN)] 2 ( 1) is obtained from a gas phase reaction of TiCl 4 and MeCN. It crystallizes in the orthorhombic space group Cmca with the cell constants a=961.8(2), b=984.0(5), c=1637.0(4) pm, and Z=4. The symmetry of the dinuclear complex is C 2 h . The Ti atoms are connected with symmetrical chloro bridges, and the octahedral coordination is completed by one acetonitrile ligand coordinated to each Ti atom. [TiCl 4(MeCN)] 2 reacts with ReNCl 2(PMe 2Ph) 3 in CH 2Cl 2 to form the dinuclear complex (Me 2PhP) 3(MeCN)ClReNTiCl 5 ( 2). It crystallizes as 2·CH 2Cl 2 in the monoclinic space group P2 1/ n with the cell constants a=982.0(2), b=1245.3(2), c=3088.1(5) pm, β=92.44(2)°, and Z=4. The linear nitrido bridge (ReNTi=167.7(4)°) is characterized by distances ReN=167.6(8) pm and TiN=223.9(9) pm. By using a fourfold excess of ReNCl 2(PMe 2Ph) 3 in toluene, the trinuclear complex [(Me 2PhP) 3Cl 2ReN] 2TiCl 4 ( 3) is obtained in form of crystals 3·2 toluene: P1̄, a=1070.4(2), b=1283.2(5), c=1300.0(3) pm, α=85.21(2)°, β=80.57(2)°, γ=86.19(3)°, Z=1. The centrosymmetric complex 3 contains a linear axis ReNTiNRe with a ReN distance of 168.5(9) pm and a TiN distance of 215.7(9) pm.

Catalytic and stoichiometric reactions of tertiary silanes with [Ir(Me) 2Cp*L] (Cp*=η 5-C 5Me 5; L=PMe 3, PMe 2Ph, PMePh 2, PPh 3) in the presence of one-electron oxidants. A unique case of SiH, SiC, IrC and PF bonds one-step activation: crystal structure of [Ir(Ph)(SiPh 2F)Cp*(PMe 3)

The iridium(III) dimethyl derivatives [Ir(Me) 2Cp*L] (Cp*=η 5-C 5Me 5; L=PMe 3 1a, PPh 3 1d) catalyze the dehydrogenative coupling of dimethylphenylsilane in the presence of one-electron oxidants to yield Me 2PhSiSiPhMe 2. Compounds 1a– d react with triphenylsilane in the presence of [FeCp 2]PF 6 to give methane and [Ir(Ph)(SiFPh 2)Cp*L] (L=PMe 3 ( 2a), PMe 2Ph ( 2b), PMePh 2 ( 2c), PPh 3 ( 2d)). 2a was structurally characterized by single-crystal X-ray diffraction experiments. The ‘three-legged piano stool’ coordination polyhedron is slightly deformed.

Group 4 and 5 metal derivatives of 2,2′-methylene-bis(6-phenylphenoxide)

Addition of the phenol 2,2′-methylene-bis(6-phenylphenol) [(HOC 6H 3Ph) 2CH 2] ( 1) (1 equiv. per Ti) to hydrocarbon solutions of [TiCl 4] or [Ti(OPr i) 4] leads to dimeric products [Ti{(OC 6H 3Ph) 2CH 2}Cl 2] 2 ( 2) and [Ti{(OC 6H 3Ph) 2CH 2}(μ-OPr i)(OPr i)] 2 ( 3). Structural studies show 2 (CHCl 3 solvate) to consist in the solid state of two tetrahedral titanium centers linked by one end of two di-aryloxide ligands. In contrast, 3 contains five-coordinate titanium atoms linked directly by two bridging isopropoxide ligands. Treatment of [MCl 5] (M=Nb, Ta) with 1 equiv. of 1 leads to sparingly soluble trichlorides 4 and 5 which react with pyridine to form soluble adducts [M{(OC 6H 3Ph) 2CH 2}Cl 3(py)] (M=Nb, 6; M=Ta, 7). Compounds 6 and 7 are isostructural in the solid state (benzene solvates) with a mer arrangement of chloride groups and the pyridine trans to one of the di-aryloxide oxygen atoms. Treatment of 7 with PMe 2Ph leads to the products [Ta{(OC 6H 3Ph) 2CH 2}Cl 3(PMe 2Ph)] ( 8) and [HPMe 2Ph][Ta{(OC 6H 3Ph) 2CH 2}Cl 4] ( 9). Structurally characterized 9 (benzene solvate) presumably arises via the presence of trace amounts of water during workup. Reaction of 1 with [Ta(NMe 2) 5] allows isolation of derivatives [Ta{(OC 6H 3Ph) 2CH 2} 2(NMe 2)(HNMe 2)] ( 10) ( cis-nitrogen atoms by NMR) and [H 2NMe 2][Ta{(OC 6H 3Ph) 2CH 2} 3] ( 11) depending on the stoichiometry. The anion in 11 was shown by crystallography to contain an octahedral arrangement of oxygen atoms about the tantalum metal center. The crystallographic study of 11 is complicated by a disorder of the cation and partial occupancies for the three types of benzene solvate molecule. The niobium trichloride 4 acts as a catalyst precursor for benzene hydrogenation although with lower activity than reported for monodentate aryloxide precursors. During the catalysis the ortho-phenyl rings of the di-aryloxide ligand are not hydrogenated.

Reactions of bis(silyl)palladium(II) complexes with allyl halides. Synthesis of mono(silyl)palladium(II) halides and X-ray structure of trans-PdCl(SiF 2Ph)(PMe 2Ph) 2

Reactions of trans-Pd(SiF 2Ph) 2L 2 (L=PMe 3 ( 1a), PMe 2Ph ( 1b), PMePh 2 ( 1c)) with allyl bromide readily proceeded in CH 2Cl 2 at −20°C to form CH 2CHCH 2SiF 2Ph and the corresponding bromo(silyl)palladium complexes, trans-PdBr(SiF 2Ph)L 2 ( 2a– 2c) in high selectivities. Treatment of 1a– 1c with dry HCl in CH 2Cl 2 at −20°C gave silyl chloride complexes, trans-PdCl(SiF 2Ph)L 2 ( 3a– 3c), respectively. Complexes 2a– 2c and 3a– 3c were isolated and characterized by NMR spectroscopy and/or elemental analysis. One of the complexes, trans-PdCl(SiF 2Ph)(PMe 2Ph) 2 ( 3b), was identified also by X-ray diffraction study. Relevance of bis-silyl complexes to catalytic silylation of allylic compounds with disilanes is discussed.

Synthesis and some reactivity of cationic alkyl nitrosyl iridium(III) derivatives

The iridium(III) dimethyl derivatives [Ir(Me) 2Cp*(L)] (Cp*=η 5-C 5Me 5; L=PPh 3 ( 1a), PMePh 2 ( 1b), PMe 2Ph ( 1c), PMe 3 ( 1d)) react with NOBF 4 in CH 2Cl 2 to give the iridium(III) cationic alkylnitrosyl derivatives [Ir(Me) 2Cp*(NO)]BF 4 ( 2), and [Ir(Me)Cp*(NO)(L)](BF 4) 2 (L=PMePh 2 4b, PMe 2Ph 4c, PMe 3 4d). EPR spectroscopy shows that the reaction proceeds through the iridium(IV) intermediates 1a + – 1d +. Treatment of 1d with NOBF 4 in acetonitrile gives, in addition to 4d, the acetonitrile substitution products [Ir(Me)Cp*(CH 3CN)(PMe 3)]BF 4 ( 5d) and [IrCp*(CH 3CN) 2(PMe 3)](BF 4) 2 ( 6d). Electrochemical and chemical reduction of 4b– 4d afford the corresponding [Ir(Me)Cp*(NO)(L)](BF 4) 7b– 7d, which have been studied by EPR spectroscopy. Reaction of 2 with PPh 3 gives [Ir(Me) 2Cp*(PPh 3)]; treatment of 4b and 4c with the appropriate phosphine gives [Ir(Me)Cp*(L) 2](BF 4) (L=PMePh 2, PMe 2Ph), respectively.

Synthesis, platinum(II) complexes and structural aspects of the new tetradentate phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane

Several novel dimers of the composition [M 2Cl 4( trans-dppen) 2] (M=Ni ( 1), Pd ( 2), Pt ( 3)) containing trans-1,2-bis(diphenylphosphino)ethene ( trans-dppen) have been prepared and characterized by X-ray diffraction methods, NMR spectroscopy ( 195Pt{ 1H}, 31P{ 1H}), elemental analyses, and melting points. The intramolecular [2+2] photocycloaddition of the two diphosphine-bridges in 3 produces [Pt 2Cl 4(dppcb)] ( 4), where dppcb is the new tetradentate phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane. Neither 1 nor the free diphosphine trans-dppen shows this reaction. In the case of 2 the photocycloaddition is slower than in 3. This difference can be explained by the shorter distance between the two aliphatic double bonds in 3 than in 2, but also different transition probabilities within ground and excited states of the used metals could be involved. Furthermore, variable-temperature 31P{ 1H} NMR spectroscopy of 2 or 3 reveals a negative activation entropy of 2 for the [2+2] photocycloaddition, but a positive of 3. The removal of chloride from 4 by precipitating AgCl with AgBF 4, and subsequent treatment with 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) leads to [Pt 2(dppcb)(bipy) 2](BF 4) 4 ( 5) and [Pt 2(dppcb)(phen) 2](BF 4) 4 ( 6), respectively. In an analogous reaction of 4 with PMe 2Ph or PMePh 2, [Pt 2(dppcb)(PMe 2Ph) 4](BF 4) 4 ( 7) and [Pt 2(dppcb)(PMePh 2) 4](BF 4) 4 ( 8) are formed. Complexes 1– 8 show square–planar coordinations, where the compounds 4– 8 have also been characterized by the above mentioned methods together with fast atom bombardment mass spectrometry ( 7, 8). The crystal structure of 4 reveals two conformations, which arise from an energetic competition between the sterical demands of dppcb and an ideal square–planar environment of Pt(II). The free tetraphosphine dppcb can be obtained easily from 4 by treatment with NaCN. It has been characterized fully by the above methods including 13C{ 1H} and 1H NMR spectroscopy. The X-ray structure analysis shows the pure MMMP-enantiomer in the solid crystal, which is therefore optically active. This chirality is induced by a conformation of dppcb, where all four PPh 2 groups are non-equivalent. Variable-temperature 31P{ 1H} NMR spectroscopy of dppcb confirms this explanation, since the single signal at room temperature is split into two doublets at 183 K. The goal of this article is to demonstrate the facile production of a new tetradentate phosphine from a diphosphine precursor via Pt(II) used as a template.

An approach to megalo-boranes. Mixed and multiple cluster fusions involving iridaborane and platinaborane cluster compounds. Crystal structure determinations by conventional and synchrotron methods

Several new macropolyhedral metallaboranes have been isolated from thermolytic mixed cluster fusion reactions involving metallaboranes and molten B 10H 14 as solvent. Co-thermolysis of B 10H 14 with nine-vertex [(CO)(PMe 3) 2HIrB 8H 12] ( 1) engenders 18-vertex [(CO)(PMe 3) 2IrB 17H 20] ( 3), via double cluster fusion; this has the 18-vertex configuration of syn-B 18H 22, but with a metal atom in the 10-position. From the same reaction, triple cluster fusion engenders 28-vertex [(PMe 3) 2IrB 26H 24Ir(CO)(PMe 3) 2] ( 4), which structurally is based on an intimate interfusion of closed 10-vertex and 12-vertex subclusters, to generate a tetrahedral tetraboron core that also has a more open commo one-boron linkage to a nido nine-vertex {IrB 8} subcluster. Compound 4 exhibits interesting consequences of cluster-crevice formation and introduces the concept of globular megalo-borane structures that have borons-only cores surrounded by boron-hydride sheaths. Examination for incipient megalo-borane globular behaviour in another system, viz. [IrCl(PPh 3) 3] ( 7) with anti-B 18H 22, reveals a four-atom core feature in 19-vertex [(PPh 3)HIrB 18H 18(PPh 3)] ( 6), which has a closo-type {IrB 10} 11-vertex subcluster fused to a nido 10-vertex {B 10} subcluster to generate a four-atom {IrB 3} tetrahedron. Examination for mixed cluster fusion in other systems reveals the generation of [(PMe 2Ph) 2Pt- anti-B 18H 20] ( 8), from the co-thermolysis of [(PMe 2Ph) 2PtB 8H 12] ( 2) and B 10H 14, and examination for multiple cluster fusion reveals the formation of 30-vertex [(PMe 2Ph) 2(PMe 2C 6H 4) 2Pt 2B 28H 32] ( 10), 29-vertex [(PMe 2Ph) 2PtB 28H 32] ( 11) and 27-vertex [(PMe 2Ph) 2PtB 26H 26(PMe 2Ph)] ( 12) from the same reaction. Structurally, compound 10 is based on a 10-vertex arachno-{6,9-Pt 2B 8} unit linked, via one B–B two-electron two-centre bond each, to two 10-vertex nido-{B 10} units; it also exhibits molecular condensation in the form of two P-phenylene ortho-cycloboronations. Compound 11 is based on the 19-vertex [(PMe 2Ph) 2Pt-η 4- anti-B 18H 22] configuration with an additional 10-vertex nido-{B 10H 13} moiety bound to the non-platinated subcluster via one B–B two-electron two-centre bond. Compound 12 is based on two nido 11-vertex {PtB 10} units joined by a single commo Pt vertex, with one of these units conjoined to an arachno eight-boron unit via a two-boron common edge and an open bridging {B–H( exo)–Pt–μ-B 2} link. Thermolysis of [(PMe 2Ph) 2PtB 8H 12] ( 2) with the pre-formed double-cluster compound anti-B 18H 22 generates triple-contiguity 27-vertex [(PMe 2Ph)PtB 26H 26(PMe 2Ph)] ( 13) which, structurally, consists of a nido 11-vertex {PtB 10} unit that is fused to a second 11-vertex nido {PtB 10} unit with a triangular {PtB 2} face in common, and also fused to a 10-vertex nido {B 10} unit with a {B 2} edge in common. The sequence 12→ 11→ 10→ 13→ 4 represents a progression of increasing intimacy of cluster fusion. Small crystals of compounds 3, 11 and 12 necessitated synchrotron X-radiation for sufficient diffraction intensity.

Metal–metal multiply-bonded complexes of technetium.: Part 8. Synthesis and characterization of the α- and β-isomers of Tc 2Cl 4(dppe) 2

The α- (chelated) and β- (bridged) isomers of Tc 2Cl 4(dppe) 2 (dppe=Ph 2PCH 2CH 2PPh 2) have been prepared and characterized. The reaction of Tc 2Cl 4(PEt 3) 4 or Tc 2Cl 4(PMe 2Ph) 4 with dppe in refluxing toluene affords the pale pink β-isomer, isostructural with both the analogous Mo and Re compounds. When Tc 2Cl 4(PMePh 2) 4 is refluxed in toluene with a large excess of dppe, the mauve α-isomer is produced. Spectral and electrochemical properties as well as reactivity of each isomer are reported. For each the X-ray crystal structure is also reported. The α-isomer has average Tc–Tc=2.15[1] Å and an eclipsed conformation. For the β-isomer there is a twist angle of 35(2)° and a Tc–Tc distance of 2.117(1) Å.

Condensation of triketones with tungsten hydrazido(2-) complexes derived from a dinitrogen complex: formation of mononuclear or dinuclear diazoalkane complexes

The tungsten hydrazido(2-) complex cis,mer-[WCl 2(NNH 2)(PMe 2Ph) 3], readily derived from a dinitrogen complex cis-[W(N 2) 2(PMe 2Ph) 4], reacted with 1,3,5-triketones RCOCH 2COCH 2COPh (R=Me, Ph) to give the diazoalkane complexes cis,mer-[WCl 2(NNCRCH 2COCH 2COPh)(PMe 2Ph) 3] (R=Me ( 3), Ph) via the condensation between the hydrazido(2-) ligand and one terminal carbonyl group in the triketone. By contrast, the reaction of the hydrazido(2-) complex cis,trans-[WCl 2(NNH 2)(CO)(PMe 2Ph) 2] with PhCOCH 2COCH 2COPh resulted in the formation of a dinuclear μ-bis(diazoalkane) complex [WCl 2(CO)(PMe 2Ph) 2(NNCPhCH 2COCH 2CPhNN)WCl 2(CO)(PMe 2Ph) 2] ( 5). The structures of 3 and 5 in the solid state have been determined unequivocally by X-ray analysis.

Synthesis and structures of tungsten ferrocenyldiazoalkane complexes derived from a dinitrogen complex.: Part 58. Preparation and properties of molybdenum and tungsten dinitrogen complexes

Reaction of the hydrazido(2-) complex cis, mer-[WCl 2(NNH 2)(PMe 2Ph) 3], derived from a dinitrogen complex cis-[W(N 2) 2(PMe 2Ph) 4], with formylferrocene or acetylferrocene gave ferrocenyldiazoalkane complexes cis, mer-[WCl 2(NNCRFc)(PMe 2Ph) 3] ( 2: R = H, Me; Fc = (η 5-C 5H 4)Fe(η 5-C 5H 5)). Treatment of 2 with π-acceptor ligands L such as CO, CH 2CH 2, p-MeC 6H 4CHO, p-MeC 6H 4CCH and Bu tNC afforded a series of ferrocenyldiazoalkane complexes cis, trans-[WCl 2(NNCRFc)(L)(PMe 2Ph) 2] ( 4), while upon treatment with CH 2Cl 2 2 gave the W(V) complexes mer, trans-[WCl 3(NNCRFc)(PMe 2Ph) 2] ( 5). The X-ray analyses have been undertaken to determine the detailed structures for 2a (R = H) and 5b (R = Me).

B-frame-supported bimetallics. Isoelectronic arachno-structured [(PMe 2Ph) 4Pd 2B 8H 10] and closo-structured [(PMe 3) 4(CO) 2Ir 2B 8H 8

Reaction of [IrCl(CO)(PMe 3) 2] with [NEt 4][ nido-B 9H 12] gives the ten-vertex eight-boron cluster species [(PMe 3) 4(CO) 2Ir 2B 8H 8]. This formally has a closo cluster electron count compatible with its closo structure. By contrast, ten-vertex eight-boron [(PMe 2Ph) 4Pd 2B 8H 10], isolated from [4-(NH 2Ph)- arachno-B 9H 13] and [PdCl 2(PMe 2Ph) 2], has a closo electron count but an arachno structure. The origins of this apparent anomaly are briefly addressed and enunciated.

Macropolyhedral boron-containing cluster chemistry. Isolation and characterisation of the 27-vertex contiguous triple-cluster species [(PMe 2Ph)PtB 26H 26(PMe 2Ph)

Reaction between [(PMe 2Ph) 2PtB 8H 12] and anti-B 18H 22 in benzene results in intimate cluster fusion to generate [(PMe 2Ph)PtB 26H 26-(PMe 2Ph)] which consists of a nido eleven-vertex {PtB 10} subcluster fused, with a {PtB 2} triangular face in common, to a second nido eleven-vertex {PtB 10} subcluster, which is fused in turn to a nido ten-vertex {B 10} subcluster with a {B 2} edge in common.

N-bonded enolatorhenium(I) complexes having dimethylphenylphosphine ligands as active key intermediates in catalytic Knoevenagel and Michael reactions

Enolatorhenium(I) complexes cis-Re(NCCRCO 2R′)(NCCHRCO 2R′)(PMe 2Ph) 4 (R=H, R′=Me ( 2a); R=H, R′=Et ( 2b); R=H, R′= n-Bu ( 2c); R=Me, R′=Et ( 2d)) are prepared by the reaction of ReH(N 2)(PMe 2Ph) 4 ( 1) with alkyl cyanoalkyl carboxylate. X-ray structure analysis of 2b shows that it has an octahedral Re geometry, where mutually cis enolato and ester ligands bind to the rhenium via cyano groups. Reaction of 2b with benzaldehyde gives Re(NCCHCO 2Et)[NC(EtO 2C)CCHPh]–(PMe 2Ph) 4 ( 4), which is also derived from the ligand exchange reaction of 2b with ethyl ( E)-2-cyano-3-phenylpropenoate. These rhenium(I) complexes 1, 2, and 4 catalyze Knoevenagel and Michael reactions under neutral and mild conditions. A possible mechanism for the Knoevenagel reaction has been proposed.

Cis/ trans influences in platinum(II) complexes. X-ray crystal structures of cis-dichloro(dimethyl sulfide)(dimethyl sulfoxide)platinum(II) and cis-dichloro(dimethyl sulfide)(dimethyl phenyl phosphine)platinum(II)

Cis-[PtCl 2 (dms)(dmso)] and cis-[PtCl 2(dms)(PMe 2Ph)] (dms, dimethyl sulfide; dmso, dimethyl sulfoxide) were prepared by bridge-splitting reactions. The structures have been determined from X-ray crystal data. Both compounds crystallize in space group P2 1/c with Z=4. Cis-[PtCl 2(dms)(dmso)] has unit cell dimensions of: a=8.377(2), b=8.469(2) and c=14.747(2) Å, and β=90.34(2)°. The refinement resulted in R=0.042 with Pt–Cl 2.320(4) ( trans to S in dmso), 2.299(3) ( trans to S in dms), Pt–S 2.211(4) (dmso) and 2.294(3) Å (dms). Cis-[PtCl 2(dms)(PMe2Ph)] has unit cell dimensions a=13.710(6), b=8.987(1) and c=13.770(1) Å, and β=114.38(2)°. The refinement resulted in R=0.028 with Pt–Cl 2.299(3) ( trans to S in dms), 2.367(3) ( trans to P in PMe 2Ph), Pt–S 2.270(3) and Pt–P 2.224(3) Å. A comparison of the bonds Pt–S (dms) and Pt–S(dmso) in cis-[PtCl 2 (dms)(dmso)] at the extended Hückel level revealed that a stronger covalent bond to dmso is not only an effect of the shorter distance, but also an effect of larger orbital overlap. A literature survey of related compounds gave a trans-influence order of N<S<P on the Pt–Cl bond. The cis-influence on the Pt–Cl bond distance seems to oppose the trans-influence in most cases, but the differences are small and may not be significant. The cis-influence on Pt–S and Pt–P bond distances follows, on the other hand, the trans-influence series.

Amidinato- and triazenido-bridged binuclear complexes of palladium and platinum

The reaction of [M 2Cl 2( μ-Cl) 2(PR 3) 2] (M=Pd or Pt; PR 3=PEt 3, PBu 3, PMe 2Ph, PMePh 2) with lithium amidinate or sodium triazenide gave binuclear complexes containing amidinato- or triazenido-bridges, [M 2Cl 2( μ-ArNENAr) 2(PR 3) 2] (E=CH, CMe or N). These complexes were characterized by elemental analysis and NMR ( 1H, 31P or 19;Pt) data. The structures of two complexes, [Pd 2Cl 2{ μ-PhNC(Me)NPh} 2(PMe 2Ph) 2] (10) and [Pt 2Cl 2( μ-PhNNNPh) 2(PEt 3) 2] (11) were established by single crystal X-ray structural analyses. The 19;Pt NMR data show coupling between two metal centers in the cis triazenido-bridged complex. The corresponding amidinate bridged complex does not show coupling. The role of the bridging ligand in mediating interaction between the metal centers is probed through Extended Huckel Theory (EHT) calculations. It is suggested that M–M interactions are primarily affected by the bridging ligands.

Mixed-metal cluster chemistry IX : alkylarylphosphine derivatives of [CpWIr 3(CO) 11] and X-ray crystal structure of [CpWIr 3( μ-CO) 3(CO) 7(PMe 2Ph)

Reactions of [CpWIr 3(CO) 11] ( 1) with equimolar amounts of the bidentate alkylarylphosphines bis(diphenylphosphino)ethane (dppe) and bis(diphenylphosphino)methane (dppm) afford the substitution products [CpWIr 3( μ-L)( μ-CO) 3(CO) 6] [L=dppe ( 2), dppm ( 3)]. Reactions of 1 with stoichiometric amounts of the monodentate alkylarylphosphines PMePh 2 and PMe 2Ph afford the substitution products [CpWIr 3( μ-CO) 3(CO) 8- n (L) n ] [L=PMePh 2, n=1 ( 4), 2 ( 5), 3 ( 6); L=PMe 2Ph, n=1 ( 7), 2 ( 8), 3 ( 9)]. The clusters 2–8 are fluxional in solution, with the interconverting isomers resolvable at low temperatures. Variable temperature 31P- and 13C-NMR spectra for 2 and 3 enable structural assignment of the isomers, revealing a triiridium face spanned by bridging carbonyls, a diaxially-ligated diphosphine with (in the case of dppe) a flexible backbone, and an apical tungsten-coordinated cyclopentadienyl (Cp) ligand situated over differing WIr 2 faces in the configurations. 13C-NMR exchange spectroscopy (EXSY) spectra reveal that these isomers interconvert by tripodal rotation at the apical CpW(CO) 2, resolvable (in the case of 3) into a ‘waggling’ of the CpW(CO) 2 group over the non-diphosphine ligated WIr 2 faces before the onset of complete tripodal rotation. A ‘merry-go-round’ of carbonyl ligands in the basal Ir( μ-CO) 3(CO) 3 plane occurs at a similar temperature to that of tripodal rotation for 3, but at a higher temperature for 2. For 2, flexing of the diphosphine backbone is the highest energy process observed. A structural study of one isomer of 7, namely 7a, reveals that the three edges of the triiridium face of the tetrahedral core are spanned by bridging carbonyls, and that the iridium-bound PMe 2Ph ligates axially and the tungsten-bound Cp coordinates apically with respect to the triiridium face. Information from this crystal structure, 31P-NMR data, and comparison with analogous PPh 3- and PMe 3-ligated tungsten–triiridium clusters have been employed to suggest coordination geometries for the other isomers of 4–9. The geometries of the PMePh 2- and PMe 2Ph-derivatives 4-9 follow those of the previously reported PMe 3-derivatives, with the exception of the minor isomer [CpWIr 3( μ-CO) 3(CO) 5(PMePh 2) 3] ( 6b) which has an unprecedented triradial, apical substitution geometry.