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The reaction of either the 84-electron cluster [Pt 6 (μ-CO) 6 (μ-dppm) 3 ] ( 1 ) or the 82-electron cluster [Pt 6 (CO) 6 (μ-dppm) 3 ] 2+ ( 2 ), dppm = Ph 2 PCH 2 PPh 2 , with SnX 3 − or Hg 2 X 2 gave the corresponding bicapped trigonal prismatic 86-electron clusters [Pt 6 ( μ 3 -SnX 3 ) 2 ( μ -CO) 6 ( μ -dppm) 3 ] ( 3 : X = F( 3a , Cl( 3b ), Br( 3e ) or [ Pt 6 (μ 3 - HgX ) 2 (μ- CO ) 6 (μ- dppm ) 3 ] 4 : X = Cl ( 4a ) , Br ( 4b ), l ( 4c ), respectively. The new clusters 3 and 4 have been characterized spectroscopically and 4c has also been characterized by X-ray diffraction. Crystals of 4c·CH 2 Cl 2 ·2Et 2 O are monoclinic, space group P 2 1 c , a=20.092(9), b=18.718(7), c=26.258(7) A , β=108.09(3)° V=9387(6) A 3 , Z =4. The molecular core in 4c is a Pt 6 trigonal prism with each triangular Pt 3 face capped by an Hgl fragment. The intertriangle PtPt bond distances (2.910(1)–2.948(1) A) are longer than the intratriangle PtPt distances (2.634(1)–2.687(1) A) and this is consistent with EHMO calculations. The reaction of 1 with Hg 2 X 2 to give 4 is termed a bicluster oxidative addition; according to predictions from EHMO calculations it should lead to stronger intertriangle PtPt bonding in 3 and 4 than in the precursor cluster 1 , but this is not suppored by structural data observed in 3c and 4c .

The crystal structure of the molecular salt [Pt 3 Re(CO) 2 P(OMe) 3 (μ 3 -O) 2 (μ-dppm) 3 ][AsF 6 ], dppm = Ph 2 PCH 2 PPh 2 , has been determined by X-ray diffraction. The crystals are monoclinic, space group P 2 1 / c , a = 15.614(2), b = 21.550(2), c = 24.810(2) A, β = 93.518(10)°, V = 8332.5(13) A 3 , Z = 4, R = 0.0501 for 7403 reflections with I ≥ 2 σ ( I ). The structure of the cation contains a Pt 3 Re(μ 3 -O) 2 core with a tetrahedral arrangement of the metal atoms. One Pt atom is not directly involved in metal-metal bonding, which is limited to a triangle containing one Re and two Pt atoms [Pt-Pt 2.815(1), Pt-Re 2.779(1) and 2.835(1) A]. The packing of ions in the crystal is governed by their relative size: the large cations self-assemble into one-dimensional aggregations, leaving the anions to occupy the cavities in the cationic substructure. Crystal cohesion is enhanced by hydrogen bonding of C-H ⋯ O type, involving carbonyl oxygen atoms, and by C-H ⋯ F interactions.

Undecacarbonyl[4(η5)-cyclopentadienyl]-μ3-(4,4,4-trifluorobutaneheptayl)-tetrairon(3 Fe—Fe), [{Fe(CO)3}3{μ3-CC[Fe(CO)2Cp]C(CF3)}] (Cp is η5-C5H5) contains a triangular {Fe(CO)3}3 core [Fe—Fe distances 2.482 (1), 2.663 (1) and 2.693 (1) A] linked via an unusual C3CF3 bridging unit to an Fe(CO)2Cp group.

Treatment of [PtMe2(bu2bpy)] (bu2bpy = 4,4‘-di-tert-butyl-2,2‘-bipyridine) with B(C6F5)3 in the presence of the ligand L gives, under anhydrous conditions, [PtMeL(bu2bpy)][MeB(C6F5)3] {L = CO (1a), C2H4 (2a), PPh3 (3a)}. Similar reactions performed in the presence of H2O afford [PtMeL(bu2bpy)][HOB(C6F5)3] {L = CO (1b), C2H4 (2b), PPh3 (3b)}. In the absence of L, the treatment of [PtMe2(bu2bpy)] with B(C6F5)3 and H2O gives [Pt{HOB(C6F5)3}Me(bu2bpy)] (4), the first published example of a hydroxytris(pentafluorophenyl)borate complex. All of the complexes are fully characterized by NMR and IR spectroscopy and, in the case of complex 4, by an X-ray analysis which confirms the attachment of the [HOB(C6F5)3]- ligand to the square-planar platinum atom via a Pt−O bond of 2.062(2) A. We propose that, in the presence of water, B(C6F5)3 forms an adduct [H2OB(C6F5)3] (which acts as a strong acid H[HOB(C6F5)3]) and this then protonates a Pt−Me bond of [PtMe2(bu2bpy)] forming CH4 and [PtMe(bu2bpy)]+[HOB(C6F5)3]-. This p...

The 54-electron cluster cation [Pt3{ReO3}(μ-dppm)3]+, 2, dppm = Ph2PCH2PPh2, reacts with CO, P(OMe)3, Hg, and Tl(acac), acac = MeCOCHCOMe, by addition at the Pt3 center to give the 56-electron cluster cations [Pt3{ReO3}(μ3-L)(μ-dppm)3]+, L = CO (3), Hg (6), or Tl(acac) (5), or [Pt3{ReO3}(L)(μ-dppm)3]+ (4) L = P(OMe)3. Oxidation of 6 in the presence of mercury and NH4[ReO4] gives the bis(mercury) cluster [Pt3(μ3-Hg)2(μ-dppm)3][ReO4]2, 7. The structures of 2[PF6] [cubic, space group Pa3, a = 24.495(1) A, V = 14 697(1) A3, Z = 8, R = 0.0421 for 3113 reflections with I > 2σ(I)], 6[PF6]·2Me2CO [triclinic, space group P1, a = 14.502(5) A, b = 16.712(7) A, c = 20.814(6) A, α = 70.00(3)°, β = 82.52(1)°, γ = 82.39(3)°, V = 4679(3) A3, Z = 2, R = 0.0688 for 7227 reflections with I > 2σ(I)], and 7[ReO4]2·1.5Me2CO [triclinic, space group P1, a = 16.088(5) A, b = 16.307(7) A, c = 19.390(7) A, α = 99.49(2)°, β = 93.70(1)°, γ = 117.30(2)°, V = 4401(4) A3, Z = 2, R = 0.1010 for 7931 reflections with I > 2σ(I)] have be...

The terdentate ligands C6H3-2,6-(CH(2)PCy(2))(2) (PCP: Cy = cyclohexyl) in the octahedral solvento complexes trans-[RhCl2(MeOH)(PCP)] and trans-[RhCl2(EtOH)(PCP)] adopt conformations which minimise the interactions between the sterically demanding Cy groups and the trans chlorides. Comparison of these structures with those of related molecules, including square-pyramidal and square-planar species, suggests an explanation for the different structural types obtained as products from reactions of RhCl3.3H(2)O and various ligands C6H4-1,3-(CH(2)ER(2))(2) with E = N or P.

The synthesis of a number of dimanganese complexes each containing two different bridging phosphido ligands is reported. The complex Mn2(μ-PPh2)(μ-PPhH)(CO)8 (1) is prepared by the reaction of [Mn2(CO)10] firstly with PPh2H followed by reaction with PPhH2 in decalin. The reaction of 1 with CCl4 gives Mn2(μ-PPh2)(μ-PPhCl)(CO)8 (2) and deprotonation of 1 with n-BuLi followed by reaction of the deprotonated species with RX (X  halide) or [Mn(CO)5 Br] gives the complexes [Mn2(μ-PPh2)(μ-PPhR)(CO)8 (R  Me(3a),Et(3b , CH2COMe(3c) or CO2Et(3d) and [Mn(μ-PPh2){μ-PPhMn(CO)5}(CO5(CO)8] (4). The deprotonation of [Mn2(μ-PPhH)2(Co)8] with one equivalent of n-BuLi and subsequent reaction with McCOCI gives [Mn2(μ-PPhH)(μ-PPhCOMe)(CO)8] (5) which exists in solution as a mixture of isomers. The structures of [Mn2(μ-PPh2){μ-PPhMn(CO)5}(CO)8] (4) and of trans-Mn2(μ-PPhH)(μ-PPhCOMe)(CO)8] (5) have been determined by single-crystal X-ray studies. All the complexes have been characterized spectroscopically and by elemental analysis.

The structures of [Pd(C 5 H 5 )Cl(PMe 2 Ph)] and [Pd(C 5 H 5 (dppe)]PF 6 (dppe  Ph 2 PCH 2 CH 2 PPh 2 ) have been determined by X-ray analysis. Both are μ 5 -cyclopentadienyl compounds, with the Cp ring nearly perpendicular to the PdPCl or PdP 2 plane. Comparison of their molecular geometries with those of other cyclopentadienyl-palladium complexes of the types PdCpLL′ and PdCpL 2 reveals the existence of a complete range of ring-PdLL′ or ring-PdL 2 orientations and suggests that the usual assignment of structures of these types as either staggered or eclipsed is not realistic. Likewise, the patterns of long and short CC bonds of the Cp rings do not in general follow the sequences expected for the idealized geometries, although large librational distortions of the C 5 H 5 rings in most of the compounds limit the accuracy of these determinations. The lengths of the PdC(Cp) bonds appear to be much more dependent on the relative trans influences of L and L′ than on the ring orientations.

Reduction of Re2Cl10 or NH4ReO4 by NaBH4 in the presence of Ph2PCH2PPh2, dppm, and CO provides a simple route to the complexes trans-[ReX(CO)(dppm)2], 1, X  Cl or 2, X  ReO4 respectively. Both complexes have been characterised by an X-ray diffraction study. In each complex the Ph2PCH2PPh2 ligands adopt the chelating bonding mode and the coordination geometry around the rhenium(I) centre is distorted octahedral. Complex 2 contains both rhenium(I) and rhenium(VII) centres, and a ReO ReO3 linkage with ReIO and ReVIIO distances of 2.207(3) A and 1.754(3) A, respectively.

In the crystal structure of [Pd(η 5 -C 5 H 5 )(PMe 2 Ph) 2 ]ClO 4 the asymmetric unit contains two cations and two anions, one cation adopting a nearly eclipsed, and the other a staggered orientation of the C 5 H 5 ring with respect to the perpendicular Pd(PMe 2 Ph) 2 fragment. The coordination geometry around the metal atom is distorted square planar in both rotamers. The Pd-P distances are 2.250 (2)-2.253 (2) A and the Pd-C distances vary from 2.252 (8)-2.343 (6) A

The synthesis, structure, and fluxionality of the unusual dinickel(I) complex [Ni 2 Cl 2 (μ-CO)(μ-dppm) 2 ] (1a), dppm=Ph 2 PCH 2 PPh 2 are described. Complex 1a is formed by reaction of nickel(0) with nickel(II), in particular by reaction of [Ni 2 (CO) 2 (μ-CO)(μ-dppm) 2 ] with [NiCl 2 (dppm) 2 ] or of [Ni(CO) 2 (dppm-P) 2 ] with NiCl 2 .6H 2 O

The reactions of [MoMn(µ-C5H4PPh2)(CO)7]1 with phosphines and with isonitriles have been studied. Less bulky phosphines give derivatives of 1 of the type [MoMn(µ-C5H4PPh2)(CO)6L], which are monosubstituted at the manganese atom [L = PPh2H 2a, PPh2Me 2b, PPhMe22c or P(OMe)32f] whereas more bulky phosphines substitute only at the molybdenum atom (L = PPh33a). Phosphines of intermediate bulk give both types of derivative depending on the reaction conditions (L = PPh2Et 2e or 3b, PPh2CHCH22d or 3c). Disubstituted derivatives, [MoMn(µ-C5H4PPh2)(CO)5L2][L = PPh2Me 4a, PPh2CHCH24b or P(OMe)34c], obtained by reaction of 1 with excess of the appropriate ligand, have one substituent on the manganese and one on the molybdenum atom. Isonitriles give derivatives [MoMn(µ-C5H4PPh2)(CO)6L](L = CNCH2Ph 2g or CNBut2h) which are monosubstituted at the manganese atom but in a different position to the phosphine derivatives 2a–2f. Thermolysis of the diphenylphosphine derivative 2a gives [MoMn(µ-C5H4PPh2)(µ-H)(µ-PPh2)(CO)5]5a and thermolysis of either one of the vinylphosphine derivatives 2d or 3c gives a complex [MoMn(µ-C5H4PPh2)(µ-PPh2CHCH2)(CO)5]6 in which the vinylphosphine ligand is bonded through phosphorus to manganese and through the vinyl group to the molybdenum atom. Hydrogenation of 6 gives 3b in a reaction which involves a transfer of the co-ordination of the vinylphosphine phosphorus atom from manganese to molybdenum. Addition reactions of 6 with CO and P(OMe)3 involve a similar transfer to give [MoMn(µ-C5H4PPh2)(CO)6(PPh2CHCH2)]3c and [MoMn(µ-C5H4PPh2)(CO)5(PPh2CHCH2){P(OMe)3}]7 respectively. The structures of [MoMn(µ-C5H4PPh2)(CO)6(PPh2Et)]3b and [MoMn(µ-C5H4PPh2)(µ-H)(µ-PPh2)(CO)5]5a have been determined by X-ray analysis.

The photolytic reactions of [Mn2(µ-PPh2)(µ-PPhR)(CO)8](R = Ph 1a or Me 1b) with acetylene and of 1a with allene have been studied. Although they are highly non-specific, a number of products have been isolated and characterised which contain new ligands derived from the combination of one of the bridging phosphido groups with acetylene or with allene. The reactions can involve the breaking of one or both of the bonds between the metal atoms and the bridging group. Thus the complexes [Mn2(η4-C4H4PPhR)-(µ-PPhR′)(CO)6](R = R′= Ph 2a; R = Ph, R′= Me 2b; R = Me, R′= Ph 2c), containing quaternised phosphole ligands, and [Mn2(µ-σ:η4-C4H4PPh2)(µ-PPh2)(CO)5]3 are obtained in the reaction of 1a and 1b with acetylene. The complexes [Mn2(µ-η3-C3H4PPh2)(µ-PPh2)(CO)7]4 and [Mn2(µ-η3- C6H8PPh2)(µ-PPh2)(CO)6]5, containing ligands derived respectively from the combination of one and two allene molecules with a phosphido group, are obtained in the reaction of 1a with allene. Single-crystal X-ray analyses of the molecular structures of 2c, 4 and 5 have been performed, and some reaction pathways are proposed and discussed.

The complex [Pt 3 (μ 3 -CO)(μ-dppm) 3 ] 2+ (1; dppm-Ph 2 PCH 2 PPh 2 ) adds phosphorus donors L to give the adducts [Pt 3 (μ 3 -CO)(μ-dppm) 3 L] 2+ , where L=P(OMe) 3 , P(OEt) 3 , P(OPh) 3 , PMe 2 Ph, PMePh 2 , PPh 3 , PF 3

Reactions of the diplatinum(0) complex [Pt2(µ-dppm)3](1) with H2S and RSH, R = alkyl or aryl, have been studied. With H2S the products were [Pt2H2(µ-S)(µ-dppm)2](2) and the cation [Pt3H(µ3-S)(µ-dppm)3]+, probably as the HS– salt. With RSH the products using an excess of thiol were usually [Pt(SR)2(dppm)](4; R = Me, Et, But, CH2CO2Et, Ph, 4-MeC6H4, or PhCH2). With HSCH2CH2SH the chelate complex [Pt(SCH2CH2S)(dppm)](5) was formed. Intermediate binuclear complexes were identified as [Pt2H (SR)(µ-dppm)2](7) when R = Et, and [Pt2(SR)2(µ-dppm)2](6) when R = Ph or 4-MeC6H4. With PhCH2SH, a major product was the ‘A-frame’ complex [Pt2(µ-S)(SCH2Ph)2(µ-dppm)2](8) whose structure has been determined by X-ray diffraction.

Recently, [NiCl[sub 2](dppm)[sub 2]] has been found very useful as a reagent for synthesis of homonuclear and heteronuclear dppm-bridged complexes containing nickel, as a catalyst precursor for the stereospecific cross-coupling of alkenyl halides and alkenyl Grignard reagents to give dienes or of alkyl halides with Grignard reagents in the presence of CO to give ketones, and also as a catalyst for the coupling of ethylene and butadiene to give 1,4,9-decatriene. While using [NiCl[sub 2](dppm)[sub 2]] as a precursor to dinickel complexes, it was noted that recrystallization led to partial dissociation of dppm with formation of a mixture of large crystals of [NiCl[sub 2](dppm)], which are red-brown in color, and of [NiCl[sub 2]-(dppm)[sub 2]], which are black. Since both complexes had been formulated with square planar cis-NiCl[sub 2]P[sub 2] chromophores, the great difference in appearance was surprising. The structure was therefore reinvestigated and found to be 5, in which nickel has the unexpected coordination number of 5 and in which there are both monodentate and chelate dppm ligands.

International audience; The new diamagnetic carbonyl-containing sulfido complex [Cp*2Mo2(CO)2 (μ-SMe)2(μ-S)] (8) has been obtained by the thermal reaction of the pentamethylcyclopentadienyl compound [Cp*2Mo2(CO)4] (1) with MeSSMe; the other predominant product of the reaction, [Cp*2Mo2(CO)4(μ-SMe)2] (3), results from the oxidative addition of dimethyl disulfide across the Mo2 center. Monitoring this thermal reaction by IR spectroscopy indicated that 8 arises from decarbonylative dimerization of [Cp*Mo(CO)3(SMe)] (2). Reactions with other dialkyl and diaryl chalcogenides, REER (ER = SPh, SeMe), and with thiol (HSBz) and selenol (HSePh) led only to the formation of tetracarbonyl chalcogenato-bridged derivatives [Cp*2Mo2(CO)4 (μ-ER)2] (ER = SPh (4), SBz (5), SeMe (6), SePh (7)). A thermolysis study showed the degradation of 3 to [Cp*2Mo2(μ-SMe)4] (12) via [Cp*2Mo2(CO)2(μ-SMe)2] (9); 8 was decarbonylated directly to 12. Investigation of the reaction between 8 and electrophilic reagents showed that dinuclear molybdenum(III) complexes [Cp2*Mo2(CO)2(μ-SMe)2(μ-SH)]X [X = BF4 (16), Cl (17), F(18)] were formed stereospecifically as the cis isomers. 16 has been structurally characterized by X-ray diffraction. Crystals of 16 are orthorhombic, space group Pcab, a = 15.655(5) Å, b = 16.173(3) Å, c = 23.662(5) Å, and Z = 8. The complex cation has approximate C2v symmetry and the Mo-Mo bond length is 2.772(2) Å. Complex 3 was readily oxidized by Ag[BF4] to yield the dicationic product [Cp*2Mo2(CO)4(μ-SMe)2][BF4]2 (21). All new thiolato-bridged complexes have been characterized by spectroscopic analyses. © 1995, American Chemical Society. All rights reserved.

The host t-butylcalix[4]arene, 1a, forms a 1 : 1 inclusion compound with acetonitrile as guest. The inclusion compound has been isolated and characterised by X-ray analysis of a twinned crystal at 123 K. The acetonitrile guest lies on a crystallographic four-fold symmetry axis passing through the centre of the bowl of 1a which adopts a regular cone conformation. A known tetradentate and a new tridentate phosphinitocalix[4]arene derivative, 2a and 2c respectively, have been synthesized from la and Ph2Cl. Both 2a and 2c show a strong ability to coordinate with late transition metals and new complexes of gold(I), palladium(II) and platinum(II) are reported.

The new trigold(I) triacetylide [C 6 H 3 (CCAu) 3 -1,3,5] reacts with monodentate ligands, L = isocyanide, phosphite or phosphine, to give [C 6 H 3 (CCAuL) 3 -1,3,5] complexes which form polymeric solids with intermolecular Au···Au bonding; it also reacts with bidentate ligands to give covalently linked network polymers of the formula [{C 6 H 3 (CCAu) 3 -1,3,5} 2 (µ-L–L) 3 ], L–L = diisocyanide or diphosphine.

The first complex containing the Pd4(µ4-O) linkage, previously known only in the binary oxide PdO, is prepared and characterised.

The first carbonylplatinum clusters established crystallographically to have tetrahedral Pt4 cores are [Pt4H(CO)(µ- CO)3L4]ReO42 and [Pt4(µ-CO)2L4(ReO4)2]3, L = P(C6H11)3, having 56 and 54 cluster valence electrons (CVE), respectively.

Reactions of primary amines with the perfluorovinyl complex [{Fe(CO)3}2{µ-C(SMe)(CF3)CCF2}]1 proceed with cleavage of two C–F bonds to give 2, whereas with secondary amines fluorine migration and C–F bond rupture afford the novel organometallic complex 3; both 2 and 3 have been characterized by X-ray analysis.

The ligands CO, P(OR)3, and X–(X = Cl, Br, I) add selectively to the Re Pt3 sites in the coordinatively unsaturated clusters [Pt3{Re(CO)3}(µ-dppm)3]+ and [Pt3{ReO3}(µ-dppm)3]+ respectively, dppm = Ph2PCH2PPh2: the selectivity thus displays a remarkable dependency on the oxidation state of rhenium.

η 2 -Vinyl complexes [MCl{η 2 -C(CF 3 )C(CF 3 )L} (CF 3 CCCF 3 )(η 5 -C 5 H 5 )] (M = Mo, W: L = tertiary phosphine or phosphite or pyridine) have been shown by NMR and X-ray diffraction studies to exist in two distinct isomeric forms which exhibit (a) different orientations of the η 2 -vinyl ligand (b) different configurations at the asymmetric carbon atom of the η 2 -vinyl ligand: variable temperature NMR studies reveal fluxional behaviour thought to involve reversible inversion of configuration at this carbon atom.

The crystal structure of the title compound has been determined from X-ray diffractometric data. Crystals are monoclinic, a= 8·919(4), b= 21·723(8), c= 13·865(6)A, β= 113·88(3)°, space group Cc. The structure was solved by the heavy-atom method and refined by full-matrix least squares to R 0·039 for 2573 independent reflections. The crystals contain discrete square planar [PtCl(CH2SiMe3)(PMe2Ph)2] molecules. Pt–P, is 2·293(3), Pt–Cl 2·415(5), and Pt–C 2·079(14)A.

The action of heat on [(η5-C5H5)(OC)3M(µ-SR)M′(CO)5](1)(M or M′= Cr, Mo, or W; R = Me or Ph) gives [(η5-C5H5)(OC)2[graphic omitted](CO)5](2) containing a metal–metal bond. Photolysis of (2) in the presence of carbon monoxide regenerates (1) in an example of reversible cleavage of a M–M bond by carbon monoxide. The octacarbonyls (1) react with hexafluorobut-2-yne to give products of substitution at the (η5-C5H6) M group. The spectroscopic parameters of the complexes and crystal-structure analyses of (1a; M = M′= W, R = Me), (2b; M = Mo, M′= W, R = Me), and [(η5-C5H5)(OC)(CF3C2CF3)W(µ-SMe)W(CO)5](5) are discussed in terms of the electronic properties of the bridging thiolato-group and the metal centres.

In order to determine the geometrical isomerism and absolute configuration of the ion (–)[Rh(eddda)]–(eddda = ethylenediamine-N,N′-diacetate-N,N′-di-3-propionate) and to correlate the structure with the c.d. spectrum, the X-ray crystal structure analysis of the title compound was carried out. The bright yellow crystals are orthorhombic, space group P212121, with a= 11.609(2), b= 13.309(1), c= 12.603(2)A, and Z= 4. The structure was refined on the basis of 2 883 intensities by full-matrix least-squares methods on a SEL 32/27 minicomputer. The refinement terminated at R= 0.016, Rw= 0.020. The structure of this complex is isomorphous with the chromium analogue and comprises the complex anion, lithium ions, and molecules of water. The five-membered glycinate rings are trans and the absolute configuration of the complex is Λ. The trans(O5)-(–)[Rh(eddda)]– ion has a negative sign for the lowest energy E(D4h) c.d. peak and the assignment of the absolute configuration would be reversed, based on a correlation with [Co(edta)]–(edta = ethylenediaminetetra-acetate) type complexes. The average metal–ligand distances are as follows: Rh–N 2.022(2), Rh–O(eq) 2.045(2), Rh–O(ax) 2.007(2)A. Interbond angles deviate from +4.1 to –5.1° from the ideal octahedral geometry.

The complexes cis,cis-[Pt2Cl2Me2(µ-dmpm)2](6), trans,trans-[Pt2I2Me2(µ-dmpm)2](8), and [Pt2(µ-I)Me2(µ-dmpm)2][PF6](11)(dmpm = Me2PCH2PMe2) have been prepared and characterized spectroscopically. The crystal structure of (8) was determined by X-ray diffraction techniques and refined to R= 0.036 for 2 598 unique reflections with I 3σ(I). The crystals are monoclinic, space group P21/n, a= 8.611(2), b= 16.971(3), c= 8.405(1)A, β= 102.83(2)°, Z= 2. The molecular structure shows a face-to-face geometry with crystallographically imposed Ci symmetry. It contains two square-planar metal centres [Pt ⋯ Pt 3.353 5(4)A] bridged by mutually trans dmpm ligands to afford an eight-membered Pt2P4C2 dimetallacycle with an anti configuration of the trans-PtIMe groups. Complex (8) has been shown to undergo a novel fluxional process involving overall inversion of the face-to-face structure. Differences in properties between the dmpm complexes (6), (8), and (11) and related known Ph2PCH2PPh2complexes are rationalized in terms of steric effects.

Bis-alkyne [MSR′(CF3CCCF3)2(η5-C5H5)] and η2-vinyl complexes M(η3-C(CF3)C(CF3)SR′ (CF3CCCF3)(η5-C5H5)] (M = Mo, W, R′ = alkyl, aryl or perfluoroaryl) undergo a variety of insertion and oligomerisation reactions which are promoted by coordination of a ligand, e.g. PR3, O, to the metal centre.This can be rationalised in terms of a switch in the bonding mode of the alkynes from 3- to 2-electron donation to the metal.

The synthesis of [Pt2(µ-dppm)3][dppm = bis(diphenylphosphino)methane], either by the reduction of [PtCl2(dppm)] by Na[BH4] in aqueous ethanol, in the presence of 2 mol equivalents of dppm, or by a ligand displacement from [Pt(PPh3)4] by an excess of dppm, is described, and the complex was shown to have a ‘manxane’-type (bicyclo[3.3.3] undecane-type) structure in solution by multinuclear n.m.r. studies. This novel complex forms a bis(benzene) solvate whose crystal structure was determined by X-ray diffraction [space group I2, a= 22.539(4), b= 16.878(2), c= 20.641(2)A, β= 109.82(1)°, Z= 4, R= 0.032 for 4 968 independent reflections with I > 3σ(I)]. The complex [Pt2(µ-dppm)3] has the same C3h structure in the solid state as in solution, and displays a trigonal planar co-ordination about each of the platinum atoms, which are separated by 3.023(1) A. Although it contains no formal metal–metal bond, it does exhibit a significant metal–metal interaction. Spectroscopic studies are consistent with the known complex [Pd2(µ-dppm)3] possessing the same structure.

The variable-temperature 31P-{1H} n.m.r. spectra of a series of diphosphinoamines, X2PN(R)PX2(R = H, Me, Et, or Pri, X = Ph; R = Me, But, or CH2But, X = Cl; R = Me or But, X = F; R = Et, X = NMe2) have been studied. Complementary information on these compounds has been obtained from 1H, 13C, and 19F n.m.r., including double and triple resonance experiments. The coupling constant, 2J(PNP), covers the range –23.9 to 731.9 Hz, and its magnitude and sign can be related to the proportion of molecules in which the local symmetry of the P–N–P skeleton is C2v rather than CS. Diphosphinoamine conformers of the latter type have been clearly identified for the first time both in solution (for R = Et or Pri, X = Ph, and R = But or CH2But, X = Cl) and also in the solid phase. X-Ray analysis of Ph2PN(Pri)PPh2, based on 1 269 diffractometric intensities refined to R= 0.035, shows that the symmetry of the P–N–P skeleton is close to Cs in the solid, with P–N = 1.706(4) and 1.711(4)A, and PNP = 122.8(3)°.

Le compose du titre cristallise dans le systeme orthorhombique, groupe d'espace Pna2 1 et sa structure est affinee jusqu'a R=0,040

Reaction of the ligands (RO)2PCH2P(OR)2(R = Me, Et, Ph, or C6H4Me-4) with the compounds [Pt2Me4(µ-SMe2)2] or [PtX2(SMe2)2](X = Cl, Br, or I) gives the corresponding complexes cis,cis-[Pt2Me4{µ-(RO)2PCH2P(OR)2}2](1) and cis,cis-[Pt2X4{µ-(RO)2PCH2P(OR)2}2](2). Complexes (2) with R = Me or Et were also prepared by treating [PtX2(SMe2)2] with Cl2PCH2PCl2, followed by reaction with methanol or ethanol respectively. The crystal structure of the complex cis,cis-[Pt2Me4{µ-(EtO)2PCH2P(OEt)2}2] has been determined by X-ray diffraction methods [space group P21/a, a= 28.792(8), b= 10.560(2), c= 11.660(5)A, β= 99.63(3)°, and Z= 4; R= 0.051 for 3 525 independent reflections with I 2.5σ(I)]. In the molecular structure, two cis-PtMe2 fragments are bridged by two (EtO)2PCH2P(OEt)2 ligands to form an eight-membered Pt2P4C2 ring with Cs boat–chair conformation and a Pt ⋯ Pt separation of 3.459(1)A. Studies by 1H and 31P n.m.r. spectroscopy indicate that all complexes (1) have this conformation but that complexes (2) adopt a chair conformation. The factors affecting both the formation of mononuclear or binuclear complexes with diphosphinomethane ligands and the conformations adopted by binuclear complexes are interpreted in terms of steric effects of the ligands.