CC6H4Me-4 Group Research Articles

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 100. Synthesis of mixed-metal compounds via the salts [NEt4][Rh(CO)L(η5-C2B9H9R2)](L = PPh3, R = H; L = CO, R = Me); crystal structures of the complexes [WRhAu(µ-CC6H4Me-4)(CO)3(PPh3)(η-C5H5)(η5-C2B9H11)] and [WRh2Au2(µ3-CC6H4Me-4)(CO)6(η-C5H5)(η5-C2B9H9Me2)2]·0.5CH2Cl2

The rhodacarbaborane salts [NEt4][Rh(CO)L(η5-C2B9H9R2)] have been used to prepare the mixed-metal complexes [RhAu(CO)(PPh3)L(η5-C2B9H9R2)](L = PPh3, R = L = CO, R = Me), [WRhAu(µ-CC6H4Me-4)(CO)3L(η-C5H5)(η5-C2B9H9R2)](L = PPh3, R = H; L = CO, R = Me), and [WRh2Au2(µ3-CC6H4Me-4)(CO)6(η-C5H5)(η5-C2B9H9Me2)2]. In relate studies treatment of the salt [WAuCl(µ-CC6H4Me-4)(CO)2(η-C5H5)] with Na[Mn(CO)5] or [N(PPh3)2][Co(CO)4] yields, respectively, the trimetal compounds [WMAu(µ-CC6H4Me-4)(CO)n(η-C5H5)](M = Mn, n= 7; M = Co, n= 6). The molecular structures of [WRhAu(µ-CC6H4Me-4)(CO)3(PPh3)(η-C5H5)(η5-C2B9H11)] and [WRh2Au2(µ3-CC6H4Me-4)(CO)6(η-C5H5)(η5-C2B9H9Me2)2] have been determined by single-crystal X-ray diffraction studies. In the trimetal species there is a bent [156.9(1)°] W–Au–Rh array of metal atoms [W–Au 2.732(1) and Rh–Au 2.640(1)A] with the W–Au bond asymmetrically bridged by the p-tolylmethylidyne group [µ-C–W 1.90(1) and µ-C–Au 2.13(1)A]. The W atom carries the C5H5ring and two CO groups, while the Rh atom is ligated by the η5-C2B9H11 cage, a CO group, and the PPh3 ligand [Rh–P 2.340(3)A]. The pentanuclear metal cluster has a WAu2triangular core [W–Au (average) 2.750(2) and Au ⋯ Au 2.969(2)A] capped by the CC6H4Me-4 group [µ3-C–W 2.02(2) and µ3-C–Au (average) 2.05(2)A]. The tungsten atom is co-ordinated by two CO groups and the C5H5 ring. Each gold atom is linked to a Rh(CO)2(η5-C2B9H9Me2) fragment via both a Rh–Au bond [average 2.217(2)A] and a B–H⇀Au three-centre two-electron bond. This linkage involves for each cage the unique boron atom in the face of the icosahedral C2B9H9Me2fragment which is β to the CMe groups. The spectroscopic properties (i.r., 1H, 13C-{1H}, 31P-{1H}, and 11B n.m.r.) of the new compounds are reported, and where appropriate the data are discussed in relation to their structures.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 96. Reactions with phospha-alkynes; crystal structures of [WFe{µ-C(C6H4Me-4)PC(But)(CO)5}(η-C5Me5)] and [MoFe{µ-C(C6H4Me-4)C(But)P}(µ-CO)(CO)3(PMe3)(η-C5H5)

The electronically unsaturated dimetal compound [WFe(µ-CC6H4Me-4)(CO)5(η-C5Me5)] reacts with the phospha-alkynes R′CP (R′= But or Pri) in thf (tetrahydrofuran) below room temperature to give the complexes [WFe{µ-C(C6H4Me-4)PC(R′)}(CO)5(η-C5Me5)]. The structure of the species with R′= But has been determined by X-ray diffraction. The metal–metal bond [W–Fe 2.720(2)A] is spanned by the bridging group such that all three atoms of the CPC chain are attached to the iron atom [Fe–CC6H4Me-4 2.11 (2), Fe–CBut 2.14(1), and Fe–P 2.336(5)A] but only the terminal carbons ligate the tungsten centre [W–CC6H4Me-4 2.18(2), W–CBut 2.22(1)A]. The iron carries three CO groups, and the tungsten is co-ordinated by two CO ligands and the C5Me5 ring. Reactions between the phospha-alkynes and the dimetal compounds [MFe(µ-CC6H4Me-4)(CO)4(PMe3)(η-C5H5)](M = Mo or W) in thf afford under mild conditions the complexes [MFe{µ-C(C6H4Me-4)PC(R′)}(CO)4(PMe3)(η-C5H5)](M = Mo, R′= But or Pri; M = W, R′= But), containing a similar bridge system. The two molybdenum–iron compounds readily isomerise in solution, yielding the species [MoFe{µ-C(C6H4Me-4)C(R′)P}(µ-CO)(CO)3(PMe3)(η-C5H5)]. An X-ray diffraction study on one of the isomers (R′= But) revealed an asymmetric unit containing two crystallographically independent molecules of similar geometry. The Mo(1)–Fe(1) bond [2.710(1)A] is bridged by a carbonyl ligand and by the C(C6H4Me-4)C(But)P unit. All these atoms of the CCP group are bonded to the molybdenum atom [Mo(1)–CC6H4Me-4 2.290(4), Mo(1)–CBut 2.353(5), and Mo(1)–P(1) 2.527(2)A], but only the P and CC6H4Me-4 groups are attached to the iron [Fe(1)–CC6H4Me-4 2.017(5), Fe(1)–P(1) 2.302(2)A]. The Mo atom carries the η-C5H5 ring and a CO ligand but the latter is bent [Mo(1)–C–O 168.4(4)°] towards the µ-P atom [C ⋯ P 2.380(5)A]. The Fe atom is co-ordinated by two terminally bound CO groups and the PMe3 ligand [Fe(1)–P(2) 2.246(2)A]. The n.m.r. spectra (1H, 13C-{1H}, and 31P-{1H}) of the new compounds are reported and discussed.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 77. Reactions of iron–molybdenum compounds with alkynes; crystal structures of [MoFe{µ-C(C6H4Me-4)C(CHMe)CH2C(Me)C(Me)}(CO)4(η-C5H5)], [MoFe{µ-C(C6H4Me-4)C(CHMe)CH2}(CO)5(η-C5H5)], and [MoFe{µ-C(C6H4Me-4)C(CH2PMe3)CHMe}(CO)5(η-C5H5)

The compounds [MoFe(µ-CR)(CO)6(η-C5H5)](1a) and [MoFe2(µ3-CR)(µ-CO)(CO)8(η-C5H5)](2a)(R = C6H4Me-4) react with PhCCPh to give the same molybdenum–iron complex [MoFe{µ-C(R)C(Ph)C(Ph)}(CO)5(η-C5H5)](3a). In contrast, MeCCMe reacts with (2a) to yield [MoFe{µ-C(R)C(CHMe)CH2C(Me)C(Me)}(CO)4(η-C5H5)](4), and with (1a) to yield [MoFe{µ-C(R)C(CHMe)CH2}(CO)5(η-C5H5)][two isomers, (5a) and (5b)]. The molecular structures of (4) and (5a) have been established by X-ray diffraction. In (4) the Mo–Fe bond [2.784(1)A] is bridged by the branched six-carbon atom chain of the C(R)C(CHMe)CH2C(Me)C(Me) ligand, with the C(R)C(CHMe) fragment η3 co-ordinated to the molybdenum atom. This metal centre is also σ bonded to the terminal CMe group, and co-ordinated by one carbonyl and an η-C5H5 ligand. Both CMe groups are bonded to the iron centre, as is also the CR fragment and three terminal carbonyls. In (5a) the Mo–Fe separation (4.027 A) is non-bonding, the two metal atoms being linked via a C(R)C(CHMe)CH2 unit. The molybdenum atom is η3 co-ordinated by the CC6H4Me-4 group, while the Fe(CO)3 fragment is η4 co-ordinated by four carbon atoms of the substituted trimethylenemethane moiety (η-C5H5)(OC)2MoC(R)C(CHMe)CH2. In (5a) the Mo(CO)2(η-C5H5) and CH2 groups are cisoid, whereas in (5b) they are transoid. Treatment of the isomers (5) with PMe3 yields two zwitterionic complexes [MoFe{µ-C(R)C[C(H)Me(PMe3)]CH2}(CO)5(η-C5H5)](6a) and [MoFe{µ-C(R)C(CH2PMe3)CHMe}(CO)5(η-C5H5)](6b), of which the latter isomer is the more stable, allowing an X-ray diffraction study to be made. In (6b) a long Mo–Fe [2.831(2)A] single bond is spanned by the C(R)C(CH2PMe3)CHMe group, with the Mo(CO)2(η-C5H5) fragment attached to CR[2.20(1)A] and with the Fe(CO)3 moiety η3 co-ordinated by the three atoms C(R)C(CH2PMe3)CHMe. With CO, compound (5) yields [MoFe{µ-C(O)C(R)C(CHMe)CH2}(CO)6(η-C5H5)] formed as a 1 : 1 mixture of two isomers, (7a) and (7b). In these isomers an Fe(CO)3 group is ligated by a substituted trimethylenemethane, the central carbon of which carries CH2, CHMe, and C(R)C(O)Mo(CO)3(η-C5H5) groups as substituents; there being no molybdenum–iron bond. Isomers arise according to whether the CH2 and CHMe groups are cisoid or transoid to those of R or C(O)Mo(CO)3(η-C5H5). Treatment of the dimetal compound [MoFe(µ-CR)(CO)5(PMe3)(η-C5H5)] with MeCCMe affords the complex [MoFe{µ-C(R)C(CHMe)CH2C(O)}(µ-CO)(CO)3(PMe3)(η-C5H5)]. The n.m.r. (1H and 13C-{1H}) data for the new compounds are reported and discussed in terms of the structures.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 51. Alkylidyne(carbaborane)tungsten-gold and -rhodium complexes; crystal structures of [AuW(µ-CR)(CO)2(PPh3)(η-5C2B9H9Me2)], [RhW(µ-CR)(CO)2(PPh3)2(η5-C2B9H9Me2)], and (RhW[µ-CR)(CO)2(PPh3)2{η5-C2B9(C7H9)H8Me2}](R = C6H4Me-4)

Reactions between the bromo(alkylidyne)tungsten complex [W(CR) Br(CO)4](R = C6H4Me-4) and the salts Na2[7,8-C2B9H9R′2](R′= Me or H), followed by treatment with [N(PPh3)2]Cl afford the compounds [N(PPh3)2][W(CR)(CO)2(η5-C2B9H9R′2)](1a, R′= Me; 1b, R′= H). The salt [NEt4][W(CMe)(CO)2(η5-C2B9H9Me2)](1c) was prepared from [W(CMe)Br(CO)4] and Tl2[7,8-C2B9H9Me2], with subsequent addition of [NEt4]Cl. Treatment of (1a) or (1b) with [AuCl(PPh3)], in the presence of TIPF6 yields the gold–tungsten complexes [AuW(µ-CR)(CO)2( PPh3)(η5-C2B9H9R′2)](2a, R′= Me; 2b, R′= H). Similarly, (1c) with [AuCl( PPh3)] affords [AuW(µ-CMe)(CO)2( PPh3)(η5-C2B9H9Me2)](2c). The structure of (2a) has been established by X-ray diffraction. The Au–W bond [2.780(8)A] is asymmetrically bridged by the CC6H4Me-4 group [µ-C–Au 2.19(3), µ-C–W 1.88(3)A]. Treatment of [AuCl(tht)](tht = tetrahydrothiophene) with (1a) gives the salt [N( PPh3)2][AuW2(µ-CR)2(CO)4(η5-C2B9H9Me2)2](3). The rhodium–tungsten compound [RhW(µ-CR)(CO)2(PPh3)2(η5-C2B9H9Me2)](4a) has been prepared by two routes: from the reaction between (1a) and [RhCl(PPh3)3] or from (1a) and [Rh(PPh3)2(cod)][PF6](cod = cyclo-octa-1,5-diene). The latter with (1b) yields [RhW(µ-CR)(CO)2(PPh3)2(η5-C2B9H11)](4b). Compounds (1a) and (1b) react with [Rh(PPh3)2(nbd)][PF6][nbd = norbornadiene (bicyclo[2.2.1] hepta-2,5-diene)] to give the complexes [RhW(µ-CR(CO)2(PPh3)2{η5-C2B9(C7H9)H8R′2}][5a,R′= Me; 5b, (two isomers), R′= H]. The structures of (4a) and (5a) have been established by X-ray diffraction. Both molecules have Y-shaped WRhP2 cores with the Rh–W bonds [4a, 2.681 (l), 5a, 2.662(2)A] bridged by CC6H4Me-4 groups [4a, µ-C–Rh 2.068(5), µ-C–W 1.880(6); 5a, µ-C-Rh 2.12(2), µ-C–W 1.84(2)A], and semibridged by a CO ligand [W–C-O, 4a, 160.2(5); 5a, 156( 1 )°] In (4a), the tungsten atom is ligated by a terminal CO group and the η5-C2B9H9Me2 cage. In (5a), the tungsten also carries a terminal CO group but the carbaborane ligand has a C7H9[nortricyclene (tricyclo[2.2.1.02,6] heptane)] fragment attached to the unique boron atom in the open face of the cage. Thus in the formation of (5a) an unprecedented hydroboration reaction has occurred, a cage B–H bond having added to the norbornadiene ligand with concomitant C–C bond formation. In contrast, treatment of the norbornadiene-containing salt (Rh(dppe)(nbd)[PF6](dppe = Ph2PCH2CH2PPh2) with (1a) gives [RhW(µ-CR)(CO)2(dppe)(η5-C2B9H9Me2)](4c). Reactions of (4a) with PEt3, PMe2Ph, dppe, and CO are reported. Examination of the 13C-{1H} and 31P-{1H} n.m.r. spectra of the complexes (4) and (5) reveal that they undergo dynamic behaviour in solution and possible mechanisms are described and discussed.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 66. Carbaboranetungsten–platinum complexes. Polyhedral rearrangements of a 12-vertex cage system; crystal structures of [PtW(CO)2(PEt3)2{µ6-C2B9H8(CH2C6H4Me-4)Me2}]·CH2Cl2, [PtW(µ-H){µ-σ:η5- C2B9H7(CH2C6H4-Me-4)Me2}(CO)2(PMe3)(PEt3)2], and related compounds

In acetone, the salts [N(PPh3)2][W(CC6H4Me-4)(CO)2(η5-C2B9H9Me2)] and [PtH(Me2CO)(PEt3)2][BF4] yield the dimetal compound [PtW(CO)2(PEt3)2{η6-C2B9H8(CH2C6H4Me-4)Me2}](2a), the structure of which has been established by X-ray diffraction. The very short Pt–W bond [2.602(1)A] is semi-bridged by the two carbonyl ligands [W–C–O 165(1) and 168(1)°], while a novel η6-C2B9H8(CH2C6H4Me-4)Me2 group ligates the tungsten atom. Six atoms [graphic omitted] in the face of the ligand are within bonding distance of the metal, but the C ⋯ C separation (2.88 A) within the ring is non-bonding. The CH2C6H4Me-4 substituent is attached to the central boron of the B3 unit, and is derived from the Pt–H, B–H, and CC6H4Me-4 groups present in the reactants. Treatment of [N(PPh3)2][W(CMe)(CO)2(η5-C2B9H9Me2)] with [ PtH (Me2CO)(PEt3)2][BF4] affords an inseparable 1 : 2 mixture of the two complexes [PtW(CO)2(PEt3)2{η6-C2B9H8(R)Me2}][(2b), R = H; (2c), R = Et]. Reactions between (2a) and the electron pair donor molecules L = PMe3, CO, CNBut, or PHPh2 yield the complexes [PtW(µ-H){µ-σ:η5-C2B9H7(CH2C6H4Me-4)Me2}(CO)2(L)(PEt3)2](3). The structure of (3a)(L = PMe3) was established by X-ray diffraction, confirming that the Pt–W bond [2.843(2)A] is bridged by a hydrido ligand, the presence of which was revealed in the 1H n.m.r. spectrum. The tungsten atom is ligated by two terminal CO groups, the PMe3 group, and an η5-C2B9H7(CH2C6H4Me-4)Me2 group. In the latter the central boron of the nido-C2B3 face carries the CH2C6H4Me-4 substituent, while another boron atom in the face forms an exo- polyhedral bond to the platinum [2.123(5)A]. The synthesis of (3a) from (2a) thus represents an unprecedented iso-closo(or hyper-closo) to closo transformation in a C2B9W 12-vertex framework. The mixture of compounds (2b) and (2c)(ca. 1 : 2) reacts with CO to give three complexes [PtW(µ-H){µ-σ:η5-C2B9H7(R)Me2}(CO)3(PEt3)2][(3e), R = H; (3f), R = Et] and [PtW(CO)3(PEt3)2(η5-C2B9H9Me2)](4), formed in a ratio (3e) : (3f) : (4) of ca. 1 : 4 : 1. Moreover, i.r. and n.m.r. studies showed that there was an equilibrium in solution between (3e) and (4). Column chromatography on alumina failed to separate the three complexes completely, and an X-ray study on a crystal from the mixture revealed that co-crystallisation had occurred. The asymmetric unit contains two crystallographically independent and chemically inequivalent molecules. One molecule proved to be (4), having a structure in which the Pt–W bond [2.818(1)A] is bridged by a B–H ⇀ Pt three-centre two-electron linkage. The latter involves the central boron atom in the nido face of the tungsten-ligating η5-C2B9H9Me2 group. The other unit in the crystal exhibited disorder. This arises from its correspondence to the two products (3e) and (3f), which differ only in the occupancy [R = H (20%) or Et (80%)] of the exo-polyhedral site at the central boron in the C2B3nido face of the carbaborane ligand. The structures of (3e) and (3f), with their exo-polyhedral B–Pt σ bonds and tungsten-ligated η5-C2B9H7(R)Me2 groups are thus closely related to that of (3a). Protonation (HBF4·Et2O) of the complexes (3)(L = PMe3, CO, or CNBut) affords the salts [PtW(µ-H)(CO)2(L)(PEt3)2{η5-C2B9H8(CH2C6H4Me-4)Me2}][BF4]. The n.m.r. data (1H, 13C-{1H}, 11 B-{1H}, and 31P-{1H}) for the new compounds are eported, and are discussed in relation to their structures.

Copper-tungsten complexes with bridging tolylmethylidyne ligands: Crystal structure of the compound [CuW 2(μ 3-CC 6H 4Me-4)(CO) 4(PPh 3)(η-C 5H 5) 2]·CH 2Cl 2

The complexes [W(CC 6H 4Me-4)(CO) 2(η-C 5H 5)] and [Cu(NCMe) 4][PF 6] in dichloromethane combine to form the salt [Cu&W(CC 6H 4Me-4)(CO) 2(η-C 5H 5)& 2][PF 6], but the latter very readily dissociates in solution releasing the tolylmethylidynetungsten compound. The more stable salt [CuW(μ-CC 6H 4Me-4)(CO) 2(NCMe)(PPh 3) (η-C 5H 5)][PF 6] is obtained by addition of [W(CC 6H 4Me-4)(CO) 2(η-C 5H 5)] to a dichloromethane solution of [Cu(NCMe) 4][PF 6] previously treated with 1 mol equivalent of PPh 3. In the presence of additional PPh 3, however, no copper-tungsten complex is formed. Several reactions of [CuW(μ-CC 6H 4Me-4)(CO) 2(NCMe)(PPh 3)(η-C 5H 5)][PF 6] have been studied, but these led only to release of [W(CC 6H 4Me-4)(CO) 2(η-C 5H 5)]. The compounds [&CuH(PPh 3)& 6] and [W(CC 6H 4Me-4)(CO) 2(η-C 5H 5)] react in toluene at room temperature to give [W(CO) 2(η 3-CH 2C 6H 4Me-4)(η-C 5H 5)] and the new cluster compound [CuW 2(μ 3-CC 6H 4Me-4)(CO) 4(PPh 3)(η-C 5H 5) 2]. The structure of the latter species has been established by X-ray diffraction. A CuW 2 metal triangle [CuW 2.640(2) and 2.610(2), and WW 3.064(1) Å] is asymmetrically capped by a CC 6H 4Me-4 group [μ 3-CCu 2.130(9), μ 3-CW 2.035(9) and 2.122(9) Å]. The copper atom is ligated by a PPh 3 molecule, and each tungsten by an η 5-cyclopentadienyl and two carbonyl groups. The copper atom is weakly coordinated in a semi-bridging manner by two of the CO ligands, one on each tungsten, and is also very weakly bound to a third. The molecule undergoes dynamic behaviour in solution.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 42. Synthesis of the compounds [N(PPh3)2][Fe2W(µ-CO)(µ-NO)(µ3-CR)(CO)6(η-C5H5)](R = Me or C6H4Me-4) and the X-ray crystal structure of the tolylmethylidyne complex

The compounds [Fe2W(µ3-CR)(µ-CO)(CO)8(η-C5H5)](R = Me or C6H4Me-4) and [N(PPh3)2][NO2] react in tetrahydrofuran at room temperature to afford the salts [N(PPh3)2][Fe2W(µ-CO)(µ-NO)(µ3-CR)(CO)6(η-C5H5)]. An X-ray diffraction study was carried out on the species with R= C6H4Me-4, which crystallises with a molecule of tetrahydrofuran. The anion contains an essentially isosceles triangle of metal atoms [Fe–W 2.702(2) and 2.71 6(2), Fe–Fe 2.607(3)Å], capped by the CC6H4Me-4 group [µ3-C–Fe 1.969(13) and 2.008(10), µ3-C–W 2.055(11)Å]. Each iron atom carries three terminally bound CO molecules. The tungsten atom is bonded by the cyclopentadienyl ligand, and in addition is attached to a CO and an NO group. These carbonyl and nitrosyl groups asymmetrically bridge the two Fe–W edges of the metal triangle [W–C–0160.0(9), W–N–O 157.0(10)°]. Protonation of the salt [N (PPh3)2][Fe2W(µ-CO)(µ-NO)(µ3-CC6H4Me-4)(CO)6(η-C5H5)] with HBF4·Et2O affords thedi-irontungsten complex [Fe2W(µ-CC6H4Me-4)(µ3-NOH)(CO)7(η-C5H5)]. A structurally related species [Fe2W(µ-CC6H4Me-4)(µ3-NC6H4Me-4)(CO)7(η-C5H5)] is obtained by heating a mixture of [Fe2W(µ3-CC6H4Me-4)(µ-CO)(CO)8(µ-C5H5)] with McC6H4N3–4 in tetrahydrofuran. Spectroscopic data (i.r. and n.m.r.) for the new complexes are reported and discussed.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 45. Synthesis of the pentanuclear metal complexes [M′M2Re2(µ-CC6H4Me-4)2(CO)18](M′= Ni or Pt, M = Cr or W) and related compounds; X-ray crystal structure of [ReWPt(µ-CC6H4Me-4)(CO)9(PMe3)2

The pentanuclear metal compounds [M′M2Re2(µ-CC6H4Me-4)2(CO)18](M′= Pt or Ni, M = Cr or W) have been prepared by treating the complexes [ReM(CC6H4Me-4)(CO)9] with [Pt(C2H4)3] Or [Ni(cod)2](cod = cyclo-octa-1,5-diene), respectively. Similarly, the species [ReM(CC6H4Me-4)(CO)9] react with the platinum compounds [Pt(C2H4)2{P(cyclo-C6H11)3}] and [Pt(C2H4)(PMe3)2] to afford the trimetal complexes [ReWPt(µ-CC6H4{Me-4)(CO)10{P(cyclo-C6H11)3}] and [ReMPt(µ-CC6H4Me-4)(CO)9(PMe3)2](M = Cr or W), respectively. An X-ray diffraction study on the compound [ReWPt(µ-CC6H4Me-4)(CO)9(PMe3)2] shows that the molecule has a bent Re–W–Pt [151.3(1)°] spine, with metal–metal distances Re–W 3.082(1) and W–Pt 2.771(1)A. The W–Pt bond is bridged by the CC6H4Me-4 group [µ-C–W 2.01 3(24), µ-C–Pt 1.962(23)A]. The rhenium atom is ligated by five CO groups orthogonally disposed, so that the metal is in an octahedral environment, the sixth site being occupied by the Re–W bond. The platinum atom carries the two PMe3 ligands [P–Pt–P 98.6(2)°] and the tungsten atom four CO groups. The latter are radially disposed so that the tungsten is in a distorted octahedral environment with respect to these CO ligands; the Re(CO)5 group, and the mid-point of the µ-C–Pt bond [Re–W–µ-C 163.1(6), Re–W–Pt 151.3(1)°]. The radial CO groups on rhenium and tungsten are staggered with respect to each other about the Re–W bond.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 47. Synthesis of tri-, tetra-, and penta-heteronuclear metal cluster compounds involving tungsten with platinum or nickel: crystal structures of the compounds [Pt3W2(µ3-CR)2(CO)4(cod)2(η-C5H5)2] and [Pt2W3(µ-CR)2(µ3-CR)(CO)6(η-C5H5)3](R = C6H4Me-4, cod = cyclo-octa-1,5-diene)

Tris(ethylene)platinum, prepared in situ from [Pt(cod)2](cod = cyclo-octa-1,5-diene), reacts with the compounds [W(CR)(CO)2L] to give the complexes [PtW2(µ-CR)2(CO)4L2](R = Me or Ph, L =η-C5H5; R = Me, Ph, or C6H4Me-4, L =η-C5Me5). The analogous nickel compounds [NiW2(µ-CR)2(CO)4L2] have also been prepared using [Ni(cod)2]. Treatment of the trinuclear metal species [MW2(µ-CR)2(CO)4L2] with one equivalent of [Pt(cod)2] affords the tetranuclear metal compounds [MPtW2(µ-CR)(µ3-CR)(CO)4(cod)L2](M = Ni or Pt, R = C6H4Me-4, L =η-C5H5 or η-C5Me5; M = Pt, R = Me, L =η-C5Me5), while with two equivalents of [Pt(cod)2] the pentanuclear metal complexes [Pt3W2(µ3-CR)2(CO)4(cod)2L2](R = C6H4Me-4, L =η-C5H5; R = Me, L =η-C5Me5) are obtained. These tetra- and penta-nuclear metal compounds were generally isolated as isomeric mixtures, as revealed by n.m.r. measurements (1H, 13C-{1H}, and 195Pt-{1H}). An X-ray diffraction study structurally characterised a symmetrical isomer of [Pt3W2(µ3-CC6H4Me-4)2(CO)4(cod)2(η-C5H5)2], a molecule having a crystallographic two-fold rotation axis. The structure comprises two ‘butterfly’µ3-CPt2W fragments sharing a wing-tip platinum vertex, with isosceles metal triangles [Pt–W 2.751(1) and 2.748(1), Pt ⋯ Pt 3.089(1)A] capped by the CC6H4Me-4 groups. The terminal Pt atoms each carry a cod ligand, and the four CO groups semi-bridge Pt–W bonds. The pentanuclear metal compounds [Pt2W3(µ-CR)2(µ3-CR)(CO)6L3](R = C6H4Me-4, L =η-C5H5; R = Me or C6H4Me-4, L =η-C5Me5), [Pt2W3(µ-CMe)(µ-CC6H4Me-4)(µ3-CMe)(CO)6(η-C5H5)(η-C5Me5)2], and [Pt2W3(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)(CO)6(η-C5H5)(η-C5Me5)2] have also been prepared by treating the appropriate tetranuclear metal compound [Pt2W2(µ-CR)(µ3-CR)(CO)4(cod)L2] with an alkylidynetungsten complex so as to displace the cod ligand. Again isomeric mixtures were produced, and identified by n.m.r. spectroscopy. An X-ray diffraction study established the molecular structure of one of the three isomers of [Pt2W3(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)(CO)6(η-C5H5)3]. The molecule has an essentially planar five-metal atom framework, with two edge-bridging and one triply bridging tolylmethylidyne groups. Four of the six CO ligands semi-bridge W–Pt bonds [W–C–O 163–168(2)A] and each tungsten carries an η-C5H5 group, with each terminal W atom having one linearly bound CO. The Pt ⋯ Pt separation [2.949(2)A] implies little direct metal-metal bonding between these atoms. Bond lengths to the central µ3-CC6H4Me-4 ligand are µ3-C–Pt 2.02(3) and 2.09(2), µ3-C–W 1.99(3)A, while those to the edge-bridging CC6H4Me-4 groups are µ-C–W 1.96(2)(mean) and µ-C–Pt 2.03(2)A(mean).

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 28. Synthesis and X-ray crystal structures of the compounds [MoW2(µ-CR)2(µ-CO)2(CO)4(η-C5H5)2] and [AuW2(µ-CR)2(CO)4(η-C5H5)2][PF6](R = C6H4Me-4)

The compound [W(CR)(CO)2(η-C5H5)](R = C6H4Me-4) reacts readily with the complexes [M(CO)3(NCMe)3](M = Mo or W) in hexane at reflux to afford the trimetal compounds [MW2(µ-CR)2(µ-σ:η2-CO)2(CO)4(η-C5H5)2], n.m.r. and i.r. data for which are reported. The molybdenum–ditungsten compound was fully characterised structurally by a single-crystal X-ray diffraction study. It comprises a bent W–Mo–W spine [148.2(2)°] with the Mo–W bonds [2.938(1)A] bridged by CC6H4Me-4 groups. The Mo atom carries two terminal carbonyl ligands; the bisector of the angle between these is an approximate axis of two-fold symmetry for the molecule as a whole. The two molybdenum–tungsten–carbene ring systems are not coplanar, but are twisted relative to one another so that the two planes are nearly orthogonal. The Mo–W and Mo–C(carbene) bonds do not form a pseudo-tetrahedral group, however, because of the presence of two cis carbonyl ligands on the central Mo atom. An especially interesting feature is that, of the two terminal carbonyl ligands on each tungsten atom, one is η2-bonded to the central molybdenum atom. The significance of this is discussed. Crystals are triclinic, space group P(no. 2), and the structure has been refined to R= 0.038 for 3 711 intensities measured to 2θ= 55° at 210 K. Treatment of chloro(tetrahydrothiophene)gold(I) with [W(CR)(CO)2(η-C5H5)] in tetrahydrofuran in the presence of TIPF6 affords the salt [AuW2(µ-CR)2(CO)4(η-C5H5)2][PF6], while [Ag(NCMe)4][BF4] and [W(CR)(CO)2(η-C5H5)] give [AgW2(µ-CR)2(CO)4(η-C5H5)2][BF4]. The spectroscopic data (i.r. and n.m.r.) for these gold and silver compounds are discussed, and the structure of the former has been established by X-ray diffraction. The cation has a bent W–Au–W spine [162.8(1)°] with the Au–W bonds [2.752(1)A] bridged by the CC6H4Me-4 groups. The dihedral angle between the two dimetallacyclopropene rings is 62°. The tungsten atoms carry η-C5H5 groups and two terminally bound CO ligands. Crystals are orthorhombic, space group Pnna(no. 52), and the structure has been refined to R= 0.050 for 1 654 reflections measured to 2θ= 50° at 200 K.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 20. Complexation of carbon–metal triple bonds with low-valent metal species; crystal structures of the bimetal complexes [CrW(µ-CC6H4Me-4)(CO)4(η-C5H5)(η-C6Me6)] and [CoW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η-C5Me5)

A series of bimetal complexes [MW(µ-CR)(CO)2(Ln)(η-C5H5)][R = C6H4Me-4; MLn= Cr(CO)2(η-C6Me6), Mn(CO)2(η-C5H4Me), Re(CO)2(η-C5H5), Co(CO)(η-C5Me5), Rh(CO)(η-C9H7)(C9H7= indenyl), lr(CO)(η-C9H7), and Ir(CO)(acac)(acac = acetylacetonate)] have been prepared from [W(CR)(CO)2(η-C5H5)] and [Cr(CO)2(thf)(η-C6Me6)](thf = tetrahydrofuran), [M(CO)2(thf)(C5H4R′)](M = Mn, R′= Me; M = Re, R′= H), [Co(CO)2(η-C5Me5)], [M(CO)2(η-C9H7)](M = Rh or Ir), and [Ir(acac)(CO)2], respectively. The compounds [RhW(µ-CMe)(CO)3(η-C5H5)(η-C9H7)] and [MoRh(acac)(µ-CMe)(CO)3(η-C5H5)] have also been obtained from related reactions. The spectroscopic data (i.r. and n.m.r.) for the new compounds are reported and discussed. The structures of the species [CrW(µ-CR)(CO)4(η-C5H5)(η-C6Me6)], (1) and [CoW(µ-CR)(CO)3(η-C5H5)(η-C5Me5)](4) have been established by X-ray diffraction, and reveal an interesting distinction between (1) and (4). For both structures the metal–metal bond is bridged by a CC6H4Me-4 group and is semi-bridged by a CO ligand, but whereas in (4) it is one of the CO ligands on the W atom which semi-bridges to Co, in (1) it is a CO ligand on the Cr atom which semi-bridges to W. Reasons for this are discussed. In both structures the cyclic ligands bonded to the metal atoms are in a trans configuration with respect to the [graphic omitted] plane.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 12. Reaction of the complexes [PtW(µ-CC6H4Me-4)(CO)2(PR3)2(η-C5H5)] with carbon monoxide. Crystal structure of [Pt2W(µ3-CC6H4Me-4)(CO)4(PMePh2)2(η-C5H5)

Di- and tri-metal complexes [PtW(µ-CR)(CO)3(PR′3)(η-C5H5)](R = C6H4Me-4; PR′3= PMe3, PMe2Ph, or PPh3) and [Pt2W(µ3-CR)(CO)4(PR′3)2(η-C5H5)](PR′3= PMe3, PMe2Ph, PMePh2, PPh3, or PEt3) have been isolated by treating toluene solutions of the compounds [PtW(µ-CR)(CO)2(PR′3)2(η-C5H5)] with CO gas at 1 bar and room temperature. N.m.r. data (1H, 13C-{1H},31P-{1H}, and l95Pt-{1H}) for the new compounds are reported and a single-crystal X-ray diffraction study has been carried out on the complex [Pt2W(µ3-CR)(CO)4(PMePh2)2(η-C5H5)]. The crystals are monoclinic, space group P21/c(no. 14), Z= 4, in a unit cell with a= 14.932 (13), b= 11.438(11), c= 26.394(24)Å, β= 97.42(7)°. Poor crystal quality resulted in refinement to R 0.075 (R′ O.080) for 2 488 reflections to 2θ⩽ 40° collected at ambient temperature. The study established that the molecular structure is based on a Pt2W metal triangle, having a long Pt ⋯ Pt distance [2.989(3)Å], and capped by a CC6H4Me-4 group with the ligated carbon atom equidistant from all three metals. The terminal phosphine and carbonyl ligands on each Pt atom are unsymmetrically transoid with respect to the Pt ⋯ Pt vector, and the two carbonyl ligands on the W atom are semi-bridging to the Pt atoms, again unsymmetrically. The molecule possesses no symmetry. The nature of the Pt ⋯ Pt interaction, and the relationship between the complexes [Pt2W(µ3-CR)(CO)4(PR′3)2(η-C5H5)] and previously reported di- and tri-platinum complexes with bridging alkyne ligands, are discussed.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 7. Interconversion of carbene and carbyne ligands at a dimetal centre. X-Ray crystal structures of [CrPt{µ-C(CO2Me)Ph}(CO)4(PMe3)3] and [ MnPt(µ-CC6H4Me-4)(CO)2(PMe3)2(η-C5H5)][BF4]·CH2Cl2

Reaction of the dimetal complexes [MPt{µ-C(OMe)Ph}(CO)5(PMe3)2] with [OMe3][BF4] followed by addition of Li[C6H4Me-4] or Na[OEt] afforded the compounds [MPt{µ-C(Ph)R}(CO)5(PMe3)2](M = Cr, R = C6H4Me-4 or OEt; M = W, R = OEt). Treatment of the compounds [MPt{µ-C(OMe)R}(CO)4(PMe3)3](M = Cr, R = Ph; M = W, R = C6H4Me-4) with [OMe3][BF4] allowed isolation and characterization of the salts [CrPt(µ-CPh)-(CO)4(PMe3)3][BF4] and [PtW(µ-CC6H4Me-4)(CO)4(PMe3)3][BF4] respectively. Reaction of [CrPt(µ-CPh)-(CO)4(PMe3)3][BF4] with Na[OMe] gave the alkylidene-bridged compound [CrPt{µ-C(CO2Me)Ph}(CO)4–(PMe3)3], the strucure of which was established by X-ray diffraction. Crystals are monoclinic, space group A2/a, Z= 8, in a unit cell with lattice parameters a= 18.27(3), b= 9.84(1), c= 31.93(5)A, β= 106.2(1)°. The structure has been refined to R 0.12 (R′ 0.12) for 2 292 independent absorption corrected intensities to 2.9 ⩽ 2θ⩽ 50°(Mo-KαX-radiation) collected at room temperature. The chromium–platinum bond [2.646(7)A] is bridged by the µ-C(CO2Me)Ph group [C–Pt 1.98(3), C–Cr 2.27(4)A]. One of the CO ligands is semi-bridging to the platinum [Cr–C–O 157(3)°]. Related platinum–tungsten compounds [PtW{µ-C(CO2R)Ph}(CO)4(PMe3)3](R = Me or Et) have also been prepared. The platinum–manganese and –rhenium compounds [MPt(µ-CC6H4Me-4)(CO)2(PR3)2(η-C5H5)][BF4](M = Mn, PR3= PMe3; M = Re, PR3= PMe3 or PMe2Ph) have been synthesized and an X-ray diffraction study made on the manganese compound which crystallises with a molecule of CH2Cl2 per molecule of complex in the asymmetric unit. Crystals are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 10.434(4), b= 19.334(7), c= 14.901(7)A, and β= 94.42(4)°. The structure has been refined to R 0.044 (R′ 0.046) for 4 223 independent reflections to 2.9 ⩽ 2θ⩽ 55°(Mo-KαX-radiation) collected at 300 K. In the cation the manganese–platinum bond [2.628(1)A] is bridged by the CC6H4Me-4 group [C–Pt 1.968(8), C–Mn 1.829(8)A] forming a dimetallacyclopropene ring, the C–Mn separation being indicative of a double bond. The 1H, 31P, and 13C (1H decoupled) n.m.r. spectra of the new compounds are reported and discussed.