Maria J. Rosales

Alkyne-substituted transition metal clusters

Publisher Summary This chapter focuses on the specific aspect of cluster organometallic chemistry, and describes the synthesis, characterization, structure, and reactivity of transition metal clusters containing alkyne, or alkyne-derived ligands. Alkynes display a diverse reactivity in their reactions with carbonyl clusters, and exhibit a wider range of coordination modes than any other simple, unsaturated molecule. Several factors affect the nature of the products in a reaction between a transition metal cluster and an alkyne or alkene. The chapter presents the various synthetic routes to alkyne or alkene-substituted clusters to analyze the changes in reactivity of the cluster systems when one or more of the important reaction parameters are altered. Tri-, tetra-, and higher nuclearity clusters are discussed separately in the chapter. The chapter presents a brief description of the chemistry of alkylidyne-substituted clusters. The main difference between the reactions of high-nuclearity clusters with alkynes and alkenes and those of the smaller clusters is that the addition of the organic fragment can produce the rupture of metal-metal bonds without cluster breakdown. One of the most important links between alkylidyne and alkyne compounds is that one of the first synthetic routes for cobalt alkylidynes involved alkynes as reagents. Alkyne-substituted cluster compounds are amenable to and, indeed, have been subjected to all of the standard techniques for structural characterization.

The synthesis of [Ru5C(CO)15] by the carbonylation of [Ru6C(CO)17] and the reactions of the pentanuclear cluster with a variety of small molecules: the X-ray structure analyses of [Ru5C(CO)15], [Ru5C(CO)15(MeCN)], [Ru5C(CO)14(PPh3)], [Ru5C(CO)13(PPh3)2], and [Ru5(µ-H)2C(CO)12{Ph2P(CH2)2PPh2}]

The hexaruthenium cluster [Ru6C(CO)17] reacts with CO at 70 °C and 80 atm to produce [Ru5C(CO)15](1) and [Ru(CO)5]. Complex (1) crystallises in space group P21/c with a= 16.448(3), b= 14.274(2), c= 20.834(4)A, β= 91.36(2)°, and Z= 8. The structure was found to be isomorphous with the analogue [Os5C(CO)15], and was refined to R= 0.051 for 3 256 diffractometer data. The five Ru atoms adopt a square-pyramidal geometry with an exposed carbido-atom lying 0.11 (2)A beneath the basal plane. Reaction of complex (1) with the nitrogen-donor ligand MeCN yields the adduct [Ru5C(CO)15(MeCN)](2) which exhibits a bridged butterfly arrangement of metal atoms with a central carbido-atom. The complex crystallises in space group P21/n with a= 14.116(6), b= 18.167(7), c= 10.276(4)A, β= 95.14(3)°, and Z= 4; the structure was solved by direct methods and difference techniques and refined to R= 0.047 for 1 604 diffractometer data. Reactions of complex (1) with tertiary phosphine ligands PR3[R = Ph (3) or MePh2(4)] or Ph2P(CH2)nPPh2[n= 1 (5) or 2 (6)] produce the substituted complexes [Ru5C(CO)15-m(PR3)m][m= 1 (3a, 4a), 2 (3b, 4b), or 3 (3c, 4c)] or [Ru5C(CO)13{Ph2P(CH2)nPPh2}][n= 1 (5) or 2 (6)]. The structures of these complexes are closely related to that of (1). Complex (3a) crystallises in space group Pn with a= 9.953(2), b= 12.247(2), c= 14.703(3)A, β= 91.23(2)°, and Z= 2, (3b) in space group P21/c with a= 15.923(4), b= 12.494(3), c= 25.210(7)A, β= 93.28(2)°, and Z= 4. Both structures were solved by a combination of direct methods and Fourier techniques and were refined to R= 0.021 for 3 305 reflections (3a) and R= 0.039 for 4 127 reflections (3b), respectively. Hydrogenation of (6) gives the dihydro-complex [Ru5(µ-H)2C(CO)12{Ph2P(CH2)2Ph2}] which crystallises in space group P21 with a= 12.210(4), b= 18.602(6), c= 18.409(6)A, β= 97.63(2)°, and Z= 4. The structure was solved using the same techniques as the other complexes and refined to R= 0.064 for 3 510 diffractometer data. Treatment of complex (1) with halide ions gives the anionic clusters [Ru5C(CO)15X]–(X = F, Cl, Br, or I) whose structures are similar to that of (2). Protonation of these anions gives the monohydrido-clusters [Ru5H(C)(CO)15X]. With Cl2 and Br2 complex (1) undergoes fragmentation to give dimers [Ru2(CO)6X4](X = Cl or Br); in contrast, reaction with I2 gives [Ru5C(CO)15I2].

Syntheses and structural characterisations of some novel mixed-metal iron-gold carbido clusters; X-ray crystal structures of Fe4AuC(η-H)(CO)12(PPh3) and Fe4Au2C(CO)12(PEt3)2

Abstract The reaction of the anion [Fe4(CO)13]− with AuClPR3 (R = Et, Ph) yields an anion which upon protonation gives the cluster Fe4AuC(H)(CO)12(PR3). This complex is reversibly deprotonated in the presence of base and the resultant anion upon treatment with AuClPR3 (R = Et, Ph) gives Fe4Au2C(CO)12(PR3)2; the formation of the latter involves attack at the carbido centre by the gold phosphine group. Both neutral carbido species were characterised by single-crystal X-ray analyses.

Synthesis and structural characterisation of the mixed-metal carbido cluster Fe5C(μ2-CO)3(CO)11(μ2-AuPEt3)-(μ4-AuPEt3) and the oxidation of FeAu clusters

Abstract Reaction of [Fe 5 C(CO) 14 ] 2− with excess (PEt 3 )AuCl/Tl(PF 6 ) affords the mixed-metal cluster Fe 5 (μ 2 -CO) 3 (CO) 11 (μ 2 -AuPEt 3 )(μ 4 -AuPEt 3 ) which has been shown by an X-ray structural analysis to exhibit a novel coordination for one of the AuPEt 3 groups. This and another FeAu cluster, Fe 4 H(CO) 12 C(AuPEt 3 ) undergo unusual oxidative rearrangements.

The reductive activation of [M5C(CO)15](M=Ru or Os) and subsequent reactions of the dianion [Os5C(CO)14)2−, carbonylation of [M5C(CO)15](M=Ru or Os) and the crystal structures of [Os5C(CO)16], [N(PPh3)2]2[Os5C(CO)14], and [Os5C(CO)14{Au(PPh3)}2]

High pressure infrared (h.p.i.r.) studies indicate that the cluster [Ru5C(CO)15](1) adds carbon monoxide under relatively mild conditions (20 °C, 80 atm) to give [Ru5C(CO)16](2), while under more forcing conditions (90 °C, 80 atm) the cluster (2) reverts back to (1). The osmium analogue, [Os5C(CO)15](3), gives [Os5C(CO)16](4) at 70 °C and 50 atm but may be obtained in quantitative yield from an autoclave reaction in the absence of solvent. Complex (4) crystallises in space group P with a= 10.017(3), b= 15.823(5), c= 16.507(8)A, α= 96.78(3), β= 103.20(3), γ= 93.41(2)°, and Z= 4. The structure was solved by a combination of direct methods and Fourier-difference techniques and refined by blocked full-matrix least squares to R= 0.073 for 6 120 reflections. The five Os atoms define a ‘bridged-butterfly’ configuration with a carbide at the centre. There are four terminal carbonyl groups bound to the bridging metal atom and three to each of the other four metal atoms. A h.p.i.r. study of the reaction of (4) with H2 has shown that at a pressure of 75 atm and at temperatures around 90 °C the cluster [Os5H2(C)(CO)15](5) is produced. The electrochemical or chemical reduction of [M5C(CO)15][M = Ru (1) or Os (3)] produces the corresponding dianion [M5C(CO)14]2–[M = Ru (6) or Os (7)]. An X-ray analysis of the [N(PPh3)2]+ salt of (7) shows that the squarepyramidal Os5C core geometry of (3) is retained. One of the Os–Os bonds in the basal plane is symmetrically bridged by a carbonyl group. The remaining 13 carbonyl ligands are co-ordinated terminally, two each to the carbonyl-bridged metal atoms, and three each to the other three metal atoms. The salt crystallises in space group P with a= 13.244(6), b= 14.648(9), c= 21.963(14)A, α= 86.78(5), β= 85.54(5), γ= 81.22(5)°, and Z= 2. The structure was solved using the same techniques as for (4) and refined by blocked-cascade least squares to R= 0.065 for 5 780 observed diffractometer data. The dianion (7) reacts with two equivalents of [Au(PPh3)Cl] to give the neutral complex [Os5C(CO)14{Au(PPh3)}2](10) which has also been characterised crystallographically. In (10) the Os5C core shows significant distortions from square-pyramidal geometry. Two opposite Os(basal)–Os(apical) bonds are bridged by the Au atoms of the Au(PPh3) ligands and these two bonds are significantly longer than the other two unbridged Os(basal)–Os(apical) bonds. Two carbonyl groups are bonded terminally to the apical Os atom, and three each to the four basal Os atoms. This complex crystallises in space group P21/c with a= 20.307(4), b= 9.843(2), c= 27.980(6)A, β= 100.53(2)°, and Z= 4. The structure was solved and refined as for (7) to R= 0.060 for 7 013 observed diffractometer data.

Reactions of [Ru5C(CO)15], involving bridging ligands : crystal and molecular structures of the complexes [Ru5(H)C(CO)14(SEt)], [Ru5(H)C(CO)13(PPh3)(SEt)], [Ru5(H)C(CO)12(PPh3)(SEt)], and [Ru5C(CO)13(PPh3){µ-Au(PPh3)}(µ-I)]

The cluster [Ru5C(CO)15] reacts with H2S, H2Se, and HSR (R = Me or Et) to give [Ru5(H)C(CO)14(SH)], [Ru5(H)C(CO)14(SeH)], and [Ru5(H)C(CO)14(SR)], respectively. The complex [Ru5(H)C(CO)14(SEt)] crystallises in space group P21/n with a= 15.315(3), b= 16.739(4), c= 10.286(3)A, β= 89.31(2)°, and Z= 4. The structure was solved by a combination of direct methods and Fourier-difference techniques, and refined by blocked-cascade least squares to R= 0.032 for 4134 observed diffractometer data. The Ru5 metal arrangement is intermediate between a square-based pyramid and a bridged ‘butterfly’ with a carbido-carbon at the centre of the cluster. The sulphur atom of the SEt group bridges one edge of the square pyramid where the Ru ⋯ Ru separation is 3.410(1)A. In the reaction of [Ru5C(CO)15] with HSEt the postulated intermediate [Ru5(H)C(CO)15(SEt)] was not isolated. The first product was [Ru5(H)C(CO)14(SEt)](4). When (4) is heated to 81 °C a further molecule of CO is lost and the complex [Ru5(H)C(CO)13(SEt)] isolated. A phosphine derivative of this complex was also prepared and characterised crystallographically; [Ru5(H)C(CO)13(PPh3)(SEt)](6) crystallises in space group P21/c with a= 15.892(2), b= 11.474(1), c= 21.387(2)A, β= 92.50(1)°, and Z= 4. The structure was solved and refined using the same techniques as for (4) to R= 0.036 for 5 861 reflections. The structure resembles that of (4) with the SEt group bridging a long Ru ⋯ Ru edge [3.438(1)A] but with one of the carbonyl groups on a Ru atom associated with the SEt bridge replaced by a phosphine ligand. An analogous reaction occurs when [Ru5C(CO)14{µ-Au(PPh3)}(µ-I)] is heated in heptane to give [Ru5C(CO)13{µ-Au(PPh3)}(µ-I)]. This complex also readily takes up phosphine to give [Ru5C(CO)13(PPh3){µ-Au(PPh3)}(µ-I)](12), which has been characterised crystallographically, crystallising in space group P with a= 9.899(3), b= 14.628(6), c= 18.788(7)A, α= 100.29(3), β= 91.31(3), γ= 93.69(3)°, and Z= 2. The structure was solved and refined as described above to R= 0.042 for 6 075 reflections. The general geometry of the Ru5C core observed in (6) is retained and the iodine ligand bridges a long Ru ⋯ Ru edge [3.526(1)A], and the Au(PPh3) group replaces the bridging hydride. Further heating of the cluster (6) results in the loss of a further CO ligand to give [Ru5(H)C(CO)12(PPh3)(SEt)](7) which may exist in two isomeric forms. The structure of one of the isomers shows that Ru–Ru bond formation has occurred and the geometry of the Ru5C core may be described as a centred, square-based pyramid. The SEt group now bridges a basal Ru–Ru edge [2.698(1)A] and the phosphine ligand is co-ordinated to a basal Ru atom. The complex (7) crystallises in space group P with a= 10.162(2), b= 13.807(4), c= 14.660(4)A, α= 78.20(2), β= 74.12(2), γ= 87.38(2)°, and Z= 2. This converged to R = 0.041 for 4 050 reflections. The adducts [Ru5C(CO)15{µ-Au(PPh3)}X](X =Cl or Br) and their derivatives [Ru5C(CO)14{µ-Au(PPh3)}X] react with PPh3 to eliminate‘ Au(PPh3)X ’ and produce [Ru5C(CO)14(PPh3)].

Phosphorus donor ligand substitution in pentanuclear osmium cluster carbonyls: crystal and molecular structures of [Os5H2(CO)14(PEt3)] and [Os5H2(CO)13(PEt3)(PEt3)P(OMe)3]

Abstract The complexes [Os 5 H 2 (CO) 15 L] (L = PPh 3 , PEt 3 , P(OMe) 3 ) undergo decarbonylation at 120°C to give compounds with the general formula [Os 5 H 2 (CO) 14 L], which adopt a trigonal bipyramidal arrangement of metal atoms with the phosphorus donor group bonded to one of the equatorial Os atoms. These clusters will also undergo further substitution to give [Os 5 H 2 (CO) 13 LL′] in which the trigonal bipyramidal metal arrangement is retained.

Copper(II) and nickel(II) complexes with a linear pentadentate ligand. The x-ray crystal structure of [CuL][CuCl4] (L = 1,9-bis-(2-pyridyl)-2,5,8-triazanonane)

Abstract Reactions between CuII and NiII salts and the ligand 1,9-bis-(2-pyridyl)-2,5,8-triazanonane at different stoichiometric relations produced two different complexes in the case of CuII and only one with NiII. The spectral properties of these complexes are discussed and the X-ray crystal structure of one of the CuII products is described. The compound consists of a CuII pentacoordinated complex cation (all the donor atoms in L are coordinated) and a tetrahedral [CuCl4]2− group. The coordination geometry of the cation can be described as a distorted square-based pyramid.

The reactivity of [Os3(CO)10(C2Ph2)] towards phenyl mercury halides

Abstract The reaction of Os3(CO)10(C2Ph2) with PhHgCl in benzene yields [Os3(CO)9 (μ3-C2Ph2)(μ2-Cl)(HgCl)] 2. The complex has been characterized by the usual spectroscopic methods and by an X-ray crystal, structure determination. The compound crystallizes in the triclinic space group P 1 , cell dimensions a = 9.727(3), b = 12.590(4), c = 14.863(7) A, α = 96.75(3), β = 109.02(3), γ = 99.58(2)°, V = 1667.8(8) A3, Z = 1. The three osmium atoms form a bent arrangement with the diphenyl acetylene and a chloride ion bridging the non-bonded (Os—Os distance of 3.768 A) osmium-osmium edge, a mercury atom bridges a metal-metal bond and is also bound, in an unsymmetrical fashion to two chlorine atoms which act as bridges to an identical triosmium-mercury unit. A toluene molecule is also present in the asymmetric unit.

Preparation and structural study of monocyclopentadienylalkoxoniobium(V) derivatives. Crystal structure of {[Nb(η5-C5H4SiMe3)Cl]2(μ-O)(μ-OOC6H4)2}

Abstract Alcoholysis with catechol or substitution reactions with NaOPh on Nb(η 5 -C 5 H 4 R)Cl 4 (R  H, SiMe 3 ) have given new alkoxoniobium(V) derivatives of the type Nb(η 5 -C 5 H 4 R)Cl 3 (OPh) (R  H, SiMe 3 ) Nb(η 5 -C 6 H 5 )Cl 2 (O 2 C 6 H 4 ) and {[Nb(η 5 -C 5 H 4 SiMe 3 )Cl] 2 (μ-O)(μ-O 2 C 6 H 4 ) 2 }. The crystal structure of the last species has been studied. The two metal atoms, 3.079(1) A apart, are symmetrically bridged by the oxo and the two catechol ligands. The two oxygen atoms of each catecholate group are coordinated to the metal atoms, one of them to one Nb atom and the other bridging the two Nb atoms. Chloride and CpSiMe 3 ligands complete the coordination sphere of both metal atoms.