Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

Coordinating properties of [M(CO)5(CN)] [M=Cr; Mo; W] ligands: formation of ion pairs or dinuclear cyanide-bridged complexes, spectroscopic and X-ray diffraction studies

The reaction of sodium cyanopentacarbonylmetalates Na[M(CO)₅(CN)] (M=Cr; Mo; W) with cationic Fe(II) complexes [Cp(CO)(L)Fe(thf)][O₃SCF₃], [L=PPh₃ (1a), CN-Benzyl (1b), CN-2,6-Me₂C₆H₃ (1c); CN-Bu^t (1d), P(OMe)₃ (1e), P(Me)₂Ph (1f)] in acetonitrile solution, yielded the metathesis products [Cp(CO)(L)Fe(NCCH₃)][NCM(CO)₅] [M=W, L=PPh₃ (2a), CN-Benzyl (2b), CN-2,6-Me₂C₆H₃ (2c); CN-Bu^t (2d), P(OMe)₃ (2e), P(Me)₂Ph (2f); M=Cr, L=(PPh₃) (3a), CN-2,6-Me₂C₆H₃ (3c); M=Mo, L=(PPh₃) (4a), CN-2,6-Me₂C₆H₃ (4c)]. The ionic nature of such complexes was suggested by conductivity measurements and their main structural features were determined by X-ray diffraction studies. Well-resolved signals relative to the [M(CO)₅(CN)] moieties could be distinguished only when ¹³C NMR experiments were performed at low temperature (from −30 to −50 °C), as in the case of [Cp(CO)(PPh₃)Fe(NCCH₃)][NCW(CO)₅] (2a) and [Cp(CO)(Benzyl-NC)Fe(NCCH₃)][NCW(CO)₅] (2b). When the same reaction was carried out in dichloromethane solution, neutral cyanide-bridged dinuclear complexes [Cp(CO)(L)FeNCM(CO)₅] [M=W, L=PPh₃ (5a), CN-Benzyl (5b); M=Cr, L=(PPh₃) (6a), CN-2,6-Me₂C₆H₃ (6c), CO (6g); M=Mo, L=CN-2,6-Me₂C₆H₃ (7c), CO (7g)] were obtained and characterized by infrared and NMR spectroscopy. In all cases, the room temperature ¹³C NMR measurements showed no broadening of cyano pentacarbonyl signals and, relative to tungsten complexes [Cp(CO)(PPh₃)FeNCW(CO)₅] (5a) and [Cp(CO)(CN-Benzyl)FeNCW(CO)₅] (5b), the presence of ¹⁸³W satellites of the ¹³CN resonances (J_CW ∼ 95 Hz) at room temperature confirmed the formation of stable neutral species. The main ¹³C NMR spectroscopic properties of the latter compounds were compared to those of the linkage isomers [Cp(CO)(PPh₃)FeCNW(CO)₅] (8a) and [Cp(CO)(CN-Benzyl)FeCNW(CO)₅] (8b). The characterization of the isomeric couples 5a-8a and 5b-8b was completed by the analyses of their main IR spectroscopic properties. The crystal structures determined for 2a, 5a, 8a and 8b allowed to investigate the geometrical and electronic differences between such complexes. Finally, the study was completed by extended Hückel calculations of the charge distribution among the relevant atoms for complexes 2a, 5a and 8a.     

Syntheses, crystal structures and DFT studies of [Me3EM(CO)5] (E = Sb, Bi; M = Cr, W), cis-[(Me3Sb)2Mo(CO)4], and [Bu3BiFe(CO)4]

Syntheses of [Me₃SbM(CO)₅] [M = Cr (1), W (2)], [Me₃BiM(CO)₅] [M = Cr (3), W (4)], cis-[(Me₃Sb)₂Mo(CO)₄] (5), [^tBu₃BiFe(CO)₄] (6), crystal structures of 1-6 and DFT studies of 1-4 are reported.     

New organobimetallic compounds containing catecholate and o-semiquinolate ligands

New organobimetallic compounds CatSn[CpM(CO)_n]₂ (2-4) were obtained by the insertion of CatSn(II) (1) into the metal-metal bond of [CpM(CO)_n]₂ (Cat - 3,6-di-tert-butylcatecholate dianion; M = Fe (2), n = 2; M = Mo (3), W (4), n = 3). The structure of CatSn[CpMo(CO)₃]₂ was determined by X-ray analysis. The oxidation of compounds 2-4 with silver(I) triflate was found to produce stable paramagnetic o-semiquinolate derivatives which keep both Sn-M bonds. New paramagnetic tin(IV) complexes were investigated by EPR spectroscopy.     

Alkyne oligomerization catalyzed by molybdenum(0) complexes

Three new molybdenum(0) complexes, [Mo(CO)₃(Hpz)₃] (1), [Mo(CO)₂(Hpz)₂(DMAD)₂] (2), (DMAD=dimethyl acetylenedicarboxylate) and [Mo(CO)₃(1-Me-imidazole)₃] (3) were synthesized and characterized. Their activity and selectivity in alkyne cyclotrimerization and co-trimerization reactions was investigated. The molecular structures of 1 and 2 have been determined by unconventional powder and standard single-crystal diffraction methods, respectively. 1 consists of a pseudo-octahedral complex of C₃ symmetry, with the ligands in fac disposition; complex 2, of idealized C₂ symmetry, is obtained by substitution of one CO and one pyrazole in 1 by two DMAD ligands, and shows the rare trans configuration of π-bound acetylenic moieties.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(L-L)(NCBH3) (M = Mo, W; L-L = dppe, bipy, en)

Compounds M(CO)₂(η³-C₃H₅)(L-L)(NCBH₃) (L-L = dppe, M = Mo(1), W(2); L-L = bipy, M = Mo(3), W(4); L-L = en, M = Mo(5), W(6)) were prepared and characterized. The single crystal X-ray analyses of 2-6 revealed that the cyanotrihydroborate anion bonds to the metal through a nitrogen atom, the open face of the allyl group being pointed toward the two carbonyls (endo-isomer). In compounds 2, 5, and 6, the two donor atoms of the bidentate ligand occupy equatorial and axial positions, respectively. In the solid state structures of compounds 3 and 4 both nitrogen atoms of the bipy ligand occupy equatorial positions. The NMR spectroscopy reveals a fluxional behavior of compounds 1, 2, 5, and 6 in solution. Although the fluxional behavior of compounds 5 and 6 ceased at about −40 °C, that of compound 1 could not be stopped even at −90 °C. Their low temperature conformations are consistent with their solid state structures. Both the endo- and exo-isomers coexist in solution for compounds 3 and 4.     

The effect of titanium alkoxides in the synthesis of heterobimetallic complexes by titanocene(III) alkoxide-induced metal-metal bond cleavage of metal carbonyl dimers

A series of titanocene(III) alkoxides L₂Ti(III)OR where L = Cp, R = Et(1b), ^tBu(1a), 2,6-Me₂C₆H₃(1c), 2,6-^tBu₂-4-Me-C₆H₂(1d), or L = Cp*, R = Me(2e), ^tBu(2a), Ph(2f) was synthesized and subjected to reaction with [CpM(CO)₃]₂ [M = Mo, W], [CpRu(CO)₂]₂, and Co₂(CO)₈. The Ti(III) precursors 1a, 1c, 2a, 2e, and 2f reacted with [CpM(CO)₃]₂ [M = Mo, W] to form heterobimetallic complexes L₂Ti(OR)(μ-OC)(CO)₂MCp [M = Mo, W], of which Ti and M are linked by an isocarbonyl bridge. Reactions of these Ti(III) complexes with Co₂(CO)₈ resulted in formation of Ti-Co₁ heterobimetallic complexes, from 2a, 2e, or 2f, or Ti-Co₃ tetrametallic complexes, Cp₂Ti(O^tBu)(μ-OC)Co₃(CO)₉ from 1a, 1b, or 1c. The products were characterized by NMR, IR, and X-ray crystallography. Reaction mechanisms were proposed from these results, in particular, from steric/electronic effects of titanium alkoxides.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(en)(X) (M = Mo, W; X = Br, N3, CN) and [(en)(η-C3H5)(CO)2M(μ-CN)M(CO)2(η-C3H5)(en)]Br (M = Mo, W)

Mononuclear compounds M(CO)₂(η³-C₃H₅)(en)(X) (X = Br, M = Mo(1), W(2); X = N₃, M = Mo(3), W(4); X = CN, M = Mo(5), W(6)) and cyanide-bridged bimetallic compounds [(en)(η³-C₃H₅)(CO)₂M(μ-CN)M(CO)₂(η³-C₃H₅)(en)]Br (M = Mo (7), W(8)) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1-6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1-4 adopt an asymmetric endo-conformation, while those of 5 and 6 were both found to possess a symmetric endo-conformation. The single crystal X-ray structures of 1-6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo-conformation in the solid state.     

Synthesis and selective silylation of ω-hydroxy functionalized (η-alkenyl)carbene complexes of chromium(0) and tungsten(0) Part 11. The chemistry of metallacyclic alkenylcarbene complexes

Tungsten(0) carbene complexes of the type (OC)₅WC(NMeCH₂CHCHCH₂OH)R 2 (R=Me: 2a; R=Ph: 2b) were generated by aminolysis of (OC)₅WC(OMe)R with cis-NHMeCH₂CHCHCH₂OH. Like their Cr-congeners 1, complexes 2 exist at room temperature as mixtures of Z- and E-isomers with regard to the C-N bond. The metallacyclic complexes (OC)₄WC(η²-NMeCH₂CHCHCH₂OH)R (4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)Me (M=Cr: 3a; M=W: 4a) with one equivalent of ⁿBuLi/Me₃SiCl gave (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₃ (M=Cr: 5; M=W: 6), whereas with two equivalents of ⁿBuLi/Me₃SiCl complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₂SiMe₃ (M=Cr: 7; M=W: 8) were formed. Hydrolysis of the latter yielded selectively (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)CH₂SiMe₃ (M=Cr: 9; M=W: 10). The complexes 1-10 were analyzed in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹H/¹H COSY, ¹H/¹H NOESY, ¹³C/¹H HETCOR).     

Syntheses and structures of molybdenum and tungsten pentabenzylcyclopentadienyl complexes: new chlorination reactions

[M(CpBz)(CO)₃CH₃] (M=Mo, 2a, W, 2b; CpBz=C₅(CH₂Ph)₅) have been prepared and reacted with PCl₅ and PhI · Cl₂. Depending on the metal and on the chlorinating reagent used [Mo(CpBz)(η²-COCH₃)Cl₃], 3, [W(CpBz)Cl₄], 4, [Mo(CpBz)(CO)₃Cl], 5 and [Mo(CpBz)Cl₄], 6 have been obtained. The molecular structures of all compounds are reported and two conformations have been characterised for the benzyl substituents. In complexes 2a, 2b and 5 one phenyl ring bends towards the metals while in 3 and 4 the five phenyls point opposite to the metals.     

Syntheses of new Mo(II) and W(II) mono(hydrosulfido) complexes and their conversion into di- and tetranuclear sulfido-bridged heterobimetallic complexes

Treatment of [Cp′MH(CO)₃] (M = Mo, W; Cp′ = η⁵-C₅H₅ (Cp), η⁵-C₅Me₅ (Cp*)) with 1/8 equiv of S₈ in THF, followed by the reaction with dppe under UV irradiation, gave new mono(hydrosulfido) complexes [Cp′M(SH)(CO)(dppe)] (Cp′ = Cp: M = Mo (5), W (6); Cp′ = Cp*: M = Mo (7), W (8); dppe = Ph₂PCH₂CH₂PPh₂). When 5 and 6 dissolved in THF were allowed to react with [RhCl(PPh₃)₃] in the presence of base, heterodinuclear complexes with bridging S and dppe ligands [CpM(CO)(μ-S)(μ-dppe)Rh(PPh₃)] (M = Mo (9), W(10)) were obtained. Semi-bridging feature of the CO ligands were also demonstrated. Upon standing in CH₂Cl₂ solutions, 9 and 10 were converted further to the dimerization products [(CpM)₂{Rh(dppe)}₂(μ₂-CO)₂(μ₃-S)₂] (M = Mo (13), W). Detailed structures of mononuclear 7 and 8, dinuclear 9 and tetranuclear 13 have been determined by the X-ray diffraction.     

Synthesis and structures of dinuclear iron, molybdenum and tungsten complexes derived from (PhCHCHPh)-coupled bis(cyclopentadiene)

Reductive coupling of phenylfulvene with amalgamated calcium metal followed by hydrolysis yields CpPhCHCHPhCp (1) in high yield. Refluxing ligand 1 and Fe(CO)₅ in xylene produces (PhCHCHPh)-coupled bis(cyclopentadienyl) tetracarbonyl diiron (PhCHCHPh)[(η⁵-C₅H₄)Fe(CO)₂]₂ (2) as a mixture of meso (2-meso) and racemic isomers (2-rac). The pure racemic isomers of the Mo and W analogues (3-rac and 4-rac) have been synthesized by lithiation of ligand 1 and addition of (MeCN)₃M(CO)₃ (M = Mo, W) followed by oxidation with 2 equiv. of ferrocenium tetrafluoroborate. All the new complexes have been fully characterized. The molecular structures of 1-meso, 2-meso, 2-rac, 3-rac, and 4-rac have been determined by X-ray diffraction analysis.     

Studies of metal exchange reactions: the synthesis and structures of heteronuclear metal clusters containing the indenyl ligand (μ3-CR)Co2M(CO)8(η- Ind)(R=H,CH3,C6H5,COOC2H5; M=Mo,W)

The novel tetrahedral clusters (μ₃-CR)Co₂M(CO)₈(η⁵-Ind) (M=Mo,W; R=H, CH₃, C₆H₅, COOC₂H₅) 5-12 containing the indenyl ligand were isolated from reactions of tricobalt clusters (μ₃-CR)Co₃(CO)₉ (R=H, CH₃, C₆H₅, COOC₂H₅) and K(η⁵-Ind)M(CO)₃ (M=Mo,W) under mild conditions. The cluster complex (μ₃-CC₆H₅)CoMo₂(CO)₇(η⁵-Ind)(η⁵-Cp (Cp*=C₅H₄C(O)CH₃) 16 was obtained via the stepwise metal exchange reaction of complex (μ₃-CC₆H₅)Co₂Mo(CO)₈(η⁵-Ind) 9 with Na(η⁵-CpMo(CO)₃, but the reaction of (μ₃-CC₆H₅)Co₂Mo(CO)₈(η⁵-Cp*) 15 with K(η⁵-Ind)Mo(CO)₃ yielded only 9. The crystal structures of compounds 7, 9 and 13 were established by single crystal X-ray diffraction methods and show structural evidence for “slippage” of the indenyl ring.     

Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E = Ge, Sn; M = Cr, Mo, W, n = 4 or 5; M = Fe, n = 4). Synthesis, spectroscopic and theoretical study

A series of germylene and stannylene (Me₂NCH₂CH₂O)₂E (E = Ge, 1; E = Sn, 2) complexes of group 6 metals and iron carbonyls L·M(CO)_n (M = Cr, Mo, W, n = 5 (3-8), n = 4 (9, 10); M = Fe, n = 4 (11, 12)) were prepared. These complexes were characterized by ¹H, ¹³C NMR, FTIR and elemental analysis. Ligand properties of 1 and 2 were compared to PPh₃ and dmiy (N,N′-dimethylimidazolin-2-ylidene) using theoretical calculations (PBE/TZ2P) and FTIR. Ligand dissociation energies increase in the order Ph₃P < 2∼1 < dmiy, while donor strength rise in the order PPh₃ < dmiy < 2 < 1.     

Preparation and characterization of molybdenum and tungsten compounds with diazabutadiene ligands constructed from amino esters and glyoxal: Crystal structures of meso and C2-symmetric isomers of Mo(CO)4(dab-asp(OMe)-OMe)

The title compounds were prepared by heating solutions of ester protected amino acids (H-l-Ala-OEt, H-β-Ala-OEt, H-l-Val-OMe, GABA-OMe, H-l-Asp(OMe)-OMe) and glyoxal in the presence of M(CO)₄(pip)₂ (M=Mo, W). The resulting novel complexes, M(CO)₄(dab-xxx-OR) (dab=diazabutadiene), contain an N,N′-diimine ligand and were characterized by ¹H- and ¹³C-NMR, IR, and UV-vis measurements. The low energy band in the visible portion of the electronic spectrum is assigned to a MLCT transition and exhibits solvatochromism. The valine, alanine and aspartic ester derivatives have C₂ symmetry resulting from the C₂ symmetry of the ligand. The reaction of the alanine and aspartic amino esters in the presence of NEt₃ produces diastereomeric mixtures caused by racemization at the amino acid α-carbon. Racemization is not observed during the formation of the valine derivatives. The crystal structures of (R,S)-Mo(CO)₄(dab-asp(OMe)-OMe) (5-RS), and (S,S)-Mo(CO)₄(dab-asp(OMe)-OMe) (5-SS), were determined. The structure of 5-RS confirms that racemization at the α-carbon occurred. 5-SS has C₂ symmetry.     

Synthesis and properties of new Mo(II) complexes with N-heterocyclic and ferrocenyl ligands

New Mo(II) complexes with 2,2′-dipyridylamine (L1), [Mo(CH₃CN)(η³-C₃H₅)(CO)₂(L1)]OTf (C1a) and [{MoBr(η³-C₃H₅)(CO)₂(L1)}₂(4,4′-bipy)](PF₆)₂ (C1b), with {[bis(2-pyridyl)amino]carbonyl}ferrocene (L2), [MoBr(η³-C₃H₅)(CO)₂(L2)] (C2), and with the new ligand N,N-bis(ferrocenecarbonyl)-2-aminopyridine (L3), [MoBr(η³-C₃H₅)(CO)₂(L3)] (C3), were prepared and characterized by FTIR and ¹H and ¹³C NMR spectroscopy. C1a, C1b, L3, and C2 were also structurally characterized by single crystal X-ray diffraction. The Mo(II) coordination sphere in all complexes features the facial arrangement of allyl and carbonyl ligands, with the axial isomer present in C1a and C2, and the equatorial in the binuclear C1b. In both C1a and C1b complexes, the L1 ligand is bonded to Mo(II) through the nitrogen atoms and the NH group is involved in hydrogen bonds. The X-ray single crystal structure of C2 shows that L2 is coordinated in a κ²-N,N-bidentate chelating fashion. Complex C3 was characterized as [MoBr(η³-C₃H₅)(CO)₂(L3)] with L3 acting as a κ²-N,O-bidentate ligand, based on the spectroscopic data, complemented by DFT calculations.The electrochemical behavior of the monoferrocenyl and diferrocenyl ligands L2 and L3 has been studied together with that of their Mo(II) complexes C2 and C3. As much as possible, the nature of the different redox changes has been confirmed by spectrophotometric measurements. The nature of the frontier orbitals, namely the localization of the HOMO in Mo for both in C2 and C3, was determined by DFT studies.     

Liquid Injection Field Desorption Ionization Mass Spectrometry of Cyclic Metal Carbonyl Complexes with Tetra-Antimony Ligands

Reactions of (norbornadiene)Cr(CO)₄ or cis-(piperidine)₂Mo(CO)₄ with R₂Sb-SbR₂, and cyclo-(R′Sb)_n (R′ = Et, n-Pr; n = 4, 5) give the complexes cyclo-[M(CO)₄(R₂Sb-SbR′- SbR′-SbR₂)] (1: M = Cr, R = Me, R′= Et; 2: M = Mo, R = Et, R′ = Et; 3: M = Mo, R = Et, R′ = n-Pr). Not accessible to established characterization methods, the oily, extremely reactive unpurified mixture of 3 with scrambled ligands was characterized by mass spectrometry using liquid injection field desorption ionization (LIFDI).      

Discovering the chemical reactivity of the molecular oxonitride [{Ti(η-C5Me5)(μ-O)}3(μ3-N)]

The ability of the oxonitride [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-CH)] and [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO)₃(1,3,5-Me₃C₆H₃)] or AlEt₃ have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO)₃Mo}(μ₃-O)₃{Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (2) and [{Et₃Al}(μ₃-O){(μ-O)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO)₆] (M = Cr, Mo, W) complexes led to activate the μ₃-N unit in 1 to afford the new compounds [Ti₃(η⁵-C₅Me₅)₃(μ-O)₄{(NC)M(CO)₅}]₂ [M = Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2-6 have been established by single crystal X-ray analysis.     

Synthesis and characterization of the first transition-metal fullerene complexes containing bis(η-benzene)chromium moieties

While photochemical reaction of C₆₀ with an equimolar amount of Mo(CO)₄(η⁶-Ph₂PC₆H₅)₂Cr (1) in toluene at room temperature produced bimetallic Mo/Cr fullerene complex fac/mer-(η²-C₆₀)Mo(CO)₃[(η⁶-Ph₂PC₆H₅)₂Cr] (2) in 87% yield, the thermal reaction of an equimolar mixture of C₆₀, M(dba)₂ (M = Pd, Pt; dba = dibenzylideneacetone) and (η⁶-Ph₂PC₆H₅)₂Cr (3) in toluene at room temperature afforded bimetallic M/Cr fullerene complexes (η²-C₆₀)M[(η⁶-Ph₂PC₆H₅)₂Cr] (4, M = Pd; 5, M = Pt) in 88% and 92% yields, respectively. Products 2, 4 and 5 are the first transition-metal fullerene complexes containing bis(η⁶-benzene)chromium moieties. While 2, 4 and 5 were characterized by elemental analysis and spectroscopy, the crystal molecular structures of 4 along with the starting materials 1 and 3 have been determined by X-ray diffraction techniques.     

Some complexes containing carbon chains end-capped by M(CO)2Tp′ [M = Mo, W; Tp′ = HB(pz)3, HB(dmpz)3] groups

Complexes M(CCCSiMe₃)(CO)₂Tp′ (Tp′ = Tp [HB(pz)₃], M = Mo 2, W 4; Tp′ = Tp^∗ [HB(dmpz)₃], M = Mo 3) are obtained from M(CCCSiMe₃)(O₂CCF₃)(CO)₂(tmeda) (1) and K[Tp′].Reactions of 2 or 4 with AuCl(PPh₃)/K₂CO₃ in MeOH afforded M{CCCAu(PPh₃)}(CO)₂Tp′ (M = Mo 5, W 6) containing C₃ chains linking the Group 6 metal and gold centres.In turn, the gold complexes react with Co₃(μ₃-CBr)(μ-dppm)(CO)₇ to give the C₄-bridged {Tp(OC)₂M}CCCC{Co₃(μ-dppm)(CO)₇} (M = Mo 7, W 8), while Mo(CBr)(CO)₂Tp^∗ and Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ give {Tp^∗(OC)₂Mo}C(CC)₂C{Co₃(μ-dppm)(CO)₇} (9) via a phosphine-gold(I) halide elimination reaction. The C₃ complexes Tp′(OC)₂MCCCRu(dppe)Cp^∗ (Tp′ = Tp, M = Mo 10, W 11; Tp′ = Tp^∗, M = Mo 12) were obtained from 2-4 and RuCl(dppe)Cp^∗ via KF-induced metalla-desilylation reactions. Reactions between Mo(CBr)(CO)₂Tp^∗ and Ru{(CC)_nAu(PPh₃)}(dppe)Cp^∗ (n = 2, 3) afforded {Tp^∗(OC)₂Mo}C(CC)_n{Ru(dppe)Cp^∗} (n = 2 13, 3 14), containing C₅ and C₇ chains, respectively. Single-crystal X-ray structure determinations of 1, 2, 7, 8, 9 and 12 are reported.