Versatile reactivity of half-sandwich Ir and Rh complexes toward carboranylamidinates and their derivatives: synthesis, structure, and catalytic activity for norbornene polymerization

Synthesis, structure, and reactivity of carboranylamidinate‐based half‐sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(μ‐Cl)Cl}₂] (M=Ir, Rh; Cp*=η⁵‐C₅Me₅) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18‐electron complexes [Cp*IrCl(Cab^N‐DIC)] ( 1 a ; Cab^N‐DIC=[iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHiPr)]), [Cp*RhCl(Cab^N‐DIC)] ( 1 b ), and [Cp*RhCl(Cab^N‐DCC)] ( 1 c ; Cab^N‐DCC=[CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHCy)]). A series of 16‐electron half‐sandwich Ir and Rh complexes [Cp*Ir(Cab^N′‐DIC)] ( 2 a ; Cab^N′‐DIC=[iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NiPr)]), [Cp*Ir(Cab^N′‐DCC)] ( 2 b , Cab^N′‐DCC=[CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NCy)]), and [Cp*Rh(Cab^N′‐DIC)] ( 2 c ) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab^N,S‐DIC)], [Cp*M(Cab^N,S‐DCC)] (M=Ir 3 a , 3 b ; Rh 3 c , 3 d ), formed through BH activation, are obtained by reaction of [{Cp*MCl₂}₂] with carboranylamidinate sulfides [RN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHR)]S^? (R=iPr, Cy), which can be prepared by inserting sulfur into the C? Li bond of lithium carboranylamidinates. Iridium complex 1 a shows catalytic activities of up to 2.69×10⁶ g_PNB ${{\rm{mol}}_{{\rm{Ir}}}^{ - {\rm{1}}} }Synthesis, structure, and reactivity of carboranylamidinate-based half-sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(μ-Cl)Cl}(2)] (M = Ir, Rh; Cp* = η(5)-C(5)Me(5)) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18-electron complexes [Cp*IrCl(Cab(N)-DIC)] (1?a; Cab(N)-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NHiPr)]), [Cp*RhCl(Cab(N)-DIC)] (1?b), and [Cp*RhCl(Cab(N)-DCC)] (1?c; Cab(N)-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10))(NHCy)]). A series of 16-electron half-sandwich Ir and Rh complexes [Cp*Ir(Cab(N')-DIC)] (2?a; Cab(N')-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NiPr)]), [Cp*Ir(Cab(N')-DCC)] (2?b, Cab(N')-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10)(NCy)]), and [Cp*Rh(Cab(N')-DIC)] (2?c) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab(N,S)-DIC)], [Cp*M(Cab(N,S)-DCC)] (M = Ir 3?a, 3?b; Rh 3?c, 3?d), formed through BH activation, are obtained by reaction of [{Cp*MCl(2)}(2)] with carboranylamidinate sulfides [RN=C(closo-1,2-C(2)B(10)H(10))(NHR)]S(-) (R = iPr, Cy), which can be prepared by inserting sulfur into the C-Li bond of lithium carboranylamidinates. Iridium complex 1?a shows catalytic activities of up to 2.69×10(6) g(PNB) mol(Ir)(-1) h(-1) for the polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities and the molecular weight of polynorbornene (PNB) were investigated under various reaction conditions. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopy; the structures of 1?a-c, 2?a, b; and 3?a, b, d were further confirmed by single crystal X-ray diffraction.     

Metalloradicals Supported by a meta‐Carborane Ligand

In this work, a pincer‐type complex [Cp*Ir‐(SNPh)(SNHPh)(C₂B₁₀H₉)] ( 2 ) was synthesized and its reactivity studied in detail. Interestingly, molecular hydrogen can induce the transformation between the metalloradical [Cp*Ir‐(SNPh)₂(C₂B₁₀H₉)] ( 5 ^.) and 2 . A mixed‐valence complex, [(Cp*Ir)₂‐(SNPh)₂(C₂B₁₀H₈)] ( 7 ^.+), was also synthesized by one‐electron oxidation. Studies show that 7 ^.+ is fully delocalized, possessing a four‐centered‐one‐electron (S‐Ir‐Ir‐S) bonding interaction. DFT calculations were also in good agreement with the experimental results.     

η4‐HBCC‐σ,π‐Borataallyl Complexes of Ruthenium Comprising an Agostic Interaction

Thermolysis of [Cp*Ru(PPh₂(CH₂)PPh₂)BH₂(L₂)] 1 (Cp*=η⁵‐C₅Me₅; L=C₇H₄NS₂), with terminal alkynes led to the formation of η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)B{R‐C=CH₂}(L)₂] ( 2 a – c ) and η²‐vinylborane complexes [Cp*Ru(R‐C=CH₂)BH(L)₂] ( 3 a – c ) ( 2 a , 3 a : R=Ph; 2 b , 3 b : R=COOCH₃; 2 c , 3 c : R=p‐CH₃‐C₆H₄; L=C₇H₄NS₂) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a – c are linked by a unique η⁴‐interaction. Conversions of 1 into 3 a – c proceed through the formation of intermediates 2 a – c . Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ‐borane complex [Cp*RuCO(μ‐H)BH₂L] 4 (L=C₇H₄NS₂) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η⁴‐σ,π‐borataallyl complexes [Cp*Ru(μ‐H)BH{R‐C=CH₂}(L)] 5 and [Cp*Ru(μ‐H)BH{HC=CH‐R}(L)] 6 (R=COOCH₃; L=C₇H₄NS₂) by Markovnikov and anti‐Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η⁴‐σ,π‐borataallyl complex [Cp*Ru(μ‐H)BH{R‐C=CH‐R}(L)] 7 (R=COOCH₃; L=C₇H₄NS₂). An agostic interaction was also found to be present in 2 a – c and 5 – 7 , which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b , 3 a – c and 5 – 7 . DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.     

Construction of tetranuclear macrocycles through C-H activation and structural transformation induced by [2+2] photocycloaddition reaction

A series of binuclear complexes [{Cp*Ir(OOCCH₂COO)}₂(pyrazine)] ( 1 b ), [{Cp*Ir(OOCCH₂COO)}₂(bpy)] ( 2 b ; bpy=4,4′‐bipyridine), [{Cp*Ir(OOCCH₂COO)}₂(bpe)] ( 3 b ; bpe=trans‐1,2‐bis(4‐pyridyl)ethylene) and tetranuclear metallamacrocycles [{(Cp*Ir)₂(OOC‐C?C‐COO)(pyrazine)}₂] ( 1 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpy)}₂] ( 2 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpe)}₂] ( 3 c ), and [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](pyrazine)}₂] ( 1 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpy)}₂] ( 2 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpe)}₂] ( 3 d ) were formed by reactions of 1 a – 3 a {[(Cp*Ir)₂(pyrazine)Cl₂] ( 1 a ), [(Cp*Ir)₂(bpy)Cl₂] ( 2 a ), and [(Cp*Ir)₂(bpe)Cl₂] ( 3 a )} with malonic acid, fumaric acid, or H₂ADB (azobenzene‐4,4′‐chcarboxylic acid), respectively, under mild conditions. The metallamacrocycles were directly self‐assembled by activation of C? H bonds from dicarboxylic acids. Interestingly, after exposure to UV/Vis light, 3 c was converted to [2+2] cycloaddition complex 4 . The molecular structures of 2 b , 1 c , 1 d , and 4 were characterized by single‐crystal x‐ray crystallography. Nanosized tubular channels, which may play important roles for their stability, were also observed in 1 c , 1 d , and 4 . All complexes were well characterized by ¹H NMR and IR spectroscopy, as well as elemental analysis.     

Half‐Sandwich Iridium Complexes Bearing a Diprotic Glyoxime Ligand: Structural Diversity Induced by Reversible Deprotonation

Synthesis and deprotonation reactions of half‐sandwich iridium complexes bearing a vicinal dioxime ligand were studied. Treatment of [{Cp*IrCl(μ‐Cl)}₂] (Cp*=η⁵‐C₅Me₅) with dimethylglyoxime (LH₂) at an Ir:LH₂ ratio of 1:1 afforded the cationic dioxime iridium complex [Cp*IrCl(LH₂)]Cl ( 1 ). The chlorido complex 1 undergoes stepwise and reversible deprotonation with potassium carbonate to give the oxime–oximato complex [Cp*IrCl(LH)] ( 2 ) and the anionic dioximato(2?) complex K[Cp*IrCl(L)] ( 3 ) sequentially. Meanwhile, twofold deprotonation of the sulfato complex [Cp*Ir(SO₄)(LH₂)] ( 4 ) resulted in the formation of the oximato‐bridged dinuclear complex [{Cp*Ir(μ‐L)}₂] ( 5 ). X‐ray analyses disclosed their supramolecular structures with one‐dimensional infinite chain ( 1 and 2 ), hexagonal open channels ( 3 ), and a tetrameric rhomboid ( 4 ) featuring multiple intermolecular hydrogen bonds and electrostatic interactions.     

The Versatile Coordination Modes of Monophosphine‐o‐Carborane in the Formation of Iridium and Rhodium Complexes: Synthesis,Reactivity, and Characterization

Monophosphine‐o‐carborane has four competitive coordination modes when it coordinates to metal centers. To explore the structural transitions driven by these competitive coordination modes, a series of monophosphine‐o‐carborane Ir,Rh complexes were synthesized and characterized. [Cp*M(Cl)₂{1‐(PPh₂)‐1,2‐C₂B₁₀H₁₁}] (M=Ir ( 1 a ), Rh ( 1 b ); Cp*=η⁵‐C₅Me₅), [Cp*Ir(H){7‐(PPh₂)‐7,8‐C₂B₉H₁₁}] ( 2 a ), and [1‐(PPh₂)‐3‐(η⁵‐Cp*)‐3,1,2‐MC₂B₉H₁₀] (M=Ir ( 3 a ), Rh ( 3 b )) can be all prepared directly by the reaction of 1‐(PPh₂)‐1,2‐C₂B₁₀H₁₁ with dimeric complexes [(Cp*MCl₂)₂] (M=Ir, Rh) under different conditions. Compound 3 b was treated with AgOTf (OTf=CF₃SO₃^?) to afford the tetranuclear metallacarborane [Ag₂(thf)₂(OTf)₂{1‐(PPh₂)‐3‐(η⁵‐Cp*)‐3,1,2‐RhC₂B₉H₁₀}₂] ( 4 b ). The arylphosphine group in 3 a and 3 b was functionalized by elemental sulfur (1 equiv) in the presence of Et₃N to afford [1‐{(S)PPh₂}‐3‐(η⁵‐Cp*)‐3,1,2‐MC₂B₉H₁₀] (M=Ir ( 5 a ), Rh ( 5 b )). Additionally, the 1‐(PPh₂)‐1,2‐C₂B₁₀H₁₁ ligand was functionalized by elemental sulfur (2 equiv) and then treated with [(Cp*IrCl₂)₂], thus resulting in two 16‐electron complexes [Cp*Ir(7‐{(S)PPh₂}‐8‐S‐7,8‐C₂B₉H₉)] ( 6 a ) and [Cp*Ir(7‐{(S)PPh₂}‐8‐S‐9‐OCH₃‐7,8‐C₂B₉H₉)] ( 7 a ). Compound 6 a further reacted with nBuPPh₂, thereby leading to 18‐electron complex [Cp*Ir(nBuPPh₂)(7‐{(S)PPh₂}‐8‐S‐7,8‐C₂B₉H₁₀)] ( 8 a ). The influences of other factors on structural transitions or the formation of targeted compounds, including reaction temperature and solvent, were also explored.     

Activation and Coordination of Ammonia at [Cp*Ir(H)2]: NMR and Matrix Isolation Studies

¹H NMR exchange spectroscopy of a reaction mixture of [Cp*Ir(H)₄] ( 1 ; Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) and ammonia suggests an exchange of hydrogen atoms between the hydrido ligands and ammonia. Treatment of 1 with ND₃ led to an H/D exchange between ND₃ and the hydrido ligands of 1 . Subsequent studies showed that photolysis of 1 isolated in frozen argon matrices leads to the formation of the iridium compounds [Cp*Ir(H)₂] ( 2 ) and [Cp*Ir(H)₃] ( 4 ), as it was confirmed by IR spectroscopy. In the presence of water the aqua complex [Cp*Ir(H)₂(OH₂)] ( 3 ) was generated simultaneously. Accordingly, photolysis of 1 in an argon matrix doped with ammonia gave rise to the ammine complex [Cp*Ir(H)₂(NH₃)] ( 5 ). IR assignments were supported by calculations of the gas‐phase IR spectra of 1 – 5 by DFT methods.     

Study of the Bonding Modes of Di‐2‐pyridyl ketoxime Ligand towards Ruthenium,Rhodium and Iridium Half Sandwich Complexes

The bonding modes of the ligand di‐2‐pyridyl ketoxime towards half‐sandwich arene ruthenium, Cp*Rh and Cp*Ir complexes were investigated. Di‐2‐pyridyl ketoxime {pyC(py)NOH} react with metal precursor [Cp*IrCl₂]₂ to give cationic oxime complexes of the general formula [Cp*Ir{pyC(py)NOH}Cl]PF₆ ( 1a ) and [Cp*Ir{pyC(py)NOH}Cl]PF₆ ( 1b ), for which two coordination isomers were observed by NMR spectroscopy. The molecular structures of the complexes revealed that in the major isomer the oxime nitrogen and one of the pyridine nitrogen atoms are coordinated to the central iridium atom forming a five membered metallocycle, whereas in the minor isomer both the pyridine nitrogen atoms are coordinated to the iridium atom forming a six membered metallacyclic ring. Di‐2‐pyridyl ketoxime react with [(arene)MCl₂]₂ to form complexes bearing formula [(p‐cymene)Ru{pyC(py)NOH}Cl]PF₆ ( 2 ); [(benzene)Ru{pyC(py)NOH}Cl]PF₆ ( 3 ), and [Cp*Rh{pyC(py)NOH}Cl]PF₆ ( 4 ). In case of complex 3 the ligand coordinates to the metal by using oxime nitrogen and one of the pyridine nitrogen atoms, whereas in complex 4 both the pyridine nitrogen atoms are coordinated to the metal ion. The complexes were fully characterized by spectroscopic techniques.     

Chemistry of N,S‐Heterocyclic Carbene and Metallaboratrane Complexes: A New η3‐BCC‐Borataallyl Complex

A high‐yielding synthetic route for the preparation of group 9 metallaboratrane complexes [Cp*MBH(L)₂], 1 and 2 ( 1 , M=Rh, 2 , M=Ir; L=C₇H₄NS₂) has been developed using [{Cp*MCl₂}₂] as precursor. This method also permitted the synthesis of an Rh–N,S‐heterocyclic carbene complex, [(Cp*Rh)(L₂)(1‐benzothiazol‐2‐ylidene)] ( 3 ; L=C₇H₄NS₂) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)₂B{CH₂C(CO₂Me)}] ( 4 ; L=C₇H₄NS₂). Compound 4 features a rare η³‐interaction between rhodium and the B‐C‐C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda‐ and irida‐boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed‐metal complexes [{Cp*Rh}{Re(CO)₃}(C₇H₄NS₂)₃] ( 5 ), [Cp*Rh{Fe₂(CO)₆}(μ‐CO)S] ( 6 ), and [Cp*RhBH(L)₂W(CO)₅] ( 7 ; L=C₇H₄NS₂) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and ¹H, ¹¹B, and ¹³C NMR spectroscopies, and the structural types of 4 – 7 have been unequivocally established by crystallographic analysis.     

Kinetic analyses of biomass tar pyrolysis using the distributed activation energy model by TG/DTA technique

Volatile compounds of iridium(I): (acetylacetonato)(1,5-cyclooctadiene)iridium(I) Ir(acac)(cod), (methylcyclopentadienyl) (1,5-cyclooctadiene)iridium(I) Ir(Cp’)(cod), (pentamethylcyclopentadienyl)(dicarbonyl) iridium(I) Ir(Cp*)(CO)₂ and (acetylacetonato)(dicarbonyl)iridium(I) Ir(acac)(CO)₂ were synthesized and identified by means of element analysis, NMR-spectroscopy, mass spectrometry. Thermal properties in solid phase for synthesized iridium(I) complexes were studied by means of thermogravimetric analysis in inert atmosphere (He). By effusion Knudsen method with mass spectrometric registration of gas phase composition the temperature dependencies of saturated vapor pressure were measured for iridium(I) compounds and the thermodynamic characteristics of vaporization processes enthalpy ΔH _T* and entropy ΔS _T⁰ were determined. The energy of intermolecular interaction in the crystals of complexes was calculated.     

Molekül‐ und Kristallstruktur von Bis[chloro(μ‐phenylimido)(η5‐pentamethylcyclopentadienyl)tantal(IV)](Ta–Ta), [{TaCl(μ‐NPh)Cp*}2]

Molecular and Crystal Structure of Bis[chloro(μ‐phenylimido)(η⁵‐pentamethylcyclopentadienyl)tantalum(IV)](Ta–Ta), [{TaCl(μ‐NPh)Cp*}₂] Despite the steric hindrance of the central atom in [TaCl₂(NPh)Cp*] (Ph = C₆H₅, Cp* = η⁵‐C₅(CH₃)₅), caused by the Cp* ligand, the imido‐ligand takes a change in bond structure when this educt is reduced to the binuclear complex [{TaCl(μ‐NPh)Cp*}₂] in which tantalum is stabilized in the unusual oxidation state +4.     

Coordination of a closo‐Cluster at Rhodium and Iridium

Stanna‐closo‐dodecaborate [Bu₃MeN]₂[SnB₁₁H₁₁] reacts as a nucleophile with the rhodium and iridium electrophiles of type [Cp*M(bipy′)Cl][BF₄] under formation of a transition metal tin bond. The zwitterionic molecules [Cp*M(bipy′)(SnB₁₁H₁₁)] (with M = Rh, Ir) were characterized by NMR spectroscopy, elemental analyses and X‐ray crystal structure analyses. A high dipole moment of 25.67 D was calculated by DFT methods in the case of the rhodium derivative.     

Redox Non‐Innocent Behavior of a Terminal Iridium Hydrazido(2−) Triple Bond

The synthesis of the first terminal Group 9 hydrazido(2‐) complex, Cp*IrN(TMP) ( 6 ) (TMP=2,2,6,6‐tetramethylpiperidine) is reported. Electronic structure and X‐ray diffraction analysis indicate that this complex contains an Ir?N triple bond, similar to Bergman's seminal Cp*Ir(N^tBu) imido complex. However, in sharp contrast to Bergman's imido, 6 displays remarkable redox non‐innocent reactivity owing to the presence of the N_β lone pair. Treatment of 6 with MeI results in electron transfer from N_β to Ir prior to oxidative addition of MeI to the iridium center. This behavior opens the possibility of carrying out facile oxidative reactions at a formally Ir^III metal center through a hydrazido(2?)/isodiazene valence tautomerization.     

Iridium(III) molecular catalysts for water oxidation: the simpler the faster

We report on three Ir(iii) molecular catalysts for water oxidation: 1, [Cp*Ir(ppy)Cl]; 2, [Cp*Ir(bzpy)NO(3)]; 3, [Cp*Ir(H(2)O)(3)](NO(3))(2). 2 and 3 are water-soluble and show a long-term activity ca. 2 and 3 times higher than 1. It is remarkable that 3, having the simplest structure, is the catalyst with the highest activity.     

Zur Reaktivität von Titanocenkomplexen [Ti(Cp′)2(η2‐Me3SiC≡CSiMe3)] (Cp′ = Cp,Cp*) gegenüber Benzoldicarbonsäuren

On the Reactivity of Titanocene Complexes [Ti(Cp′)₂(η²‐Me₃SiC≡CSiMe₃)] (Cp′ = Cp, Cp*) towards Benzenedicarboxylic Acids Titanocene complexes [Ti(Cp′)₂(BTMSA)] ( 1a , Cp′ = Cp = η⁵‐C₅H₅; 1b , Cp′ = Cp* = η⁵‐C₅Me₅; BTMSA = Me₃SiC≡CSiMe₃) were found to react with iodine and methyl iodide yielding [Ti(Cp′)₂(μ‐I)₂] ( 2a / b ; a refers to Cp′ = Cp and b to Cp′ = Cp*), [Ti(Cp′)₂I₂] ( 3a / b ) and [Ti(Cp′)₂(Me)I] ( 4a / b ), respectively. In contrast to 2a , complex 2b proved to be highly moisture sensitive yielding with cleavage of HCp* [{Ti(Cp*)I}₂(μ‐O)] ( 7 ). The corresponding reactions of 1a / b with p‐cresol and thiophenol resulted in the formation of [Ti(Cp′)₂{O(p‐Tol)}₂] ( 5a / b ) and [Ti(Cp′)₂(SPh)₂] ( 6a / b ), respectively. Reactions of 1a and 1b with 1,n‐benzenedicarboxylic acids (n = 2–4) resulted in the formation of dinuclear titanium(III) complexes of the type [{Ti(Cp′)₂}₂{μ‐1,n‐(O₂C)₂C₆H₄}] (n = 2, 8a / b ; n = 3, 9a / b ; n = 4, 10a / b ). All complexes were fully characterized analytically and spectroscopically. Furthermore, complexes 7 , 8b , 9a ·THF, 10a / b were also be characterized by single‐crystal X‐ray diffraction analyses.     

Secondary Interactions or Ligand Scrambling? Subtle Steric Effects Govern the Iridium(I) Coordination Chemistry of Phosphoramidite Ligands

The like and unlike isomers of phosphoramidite (P*) ligands are found to react differently with iridium(I), which is a key to explaining the apparently inconsistent results obtained by us and other research groups in a variety of catalytic reactions. Thus, the unlike diastereoisomer (aR,S,S)‐[IrCl(cod)( 1 a )] ( 2 a ; cod=1,5‐cyclooctadiene, 1 a =(aR,S,S)‐(1,1′‐binaphthalene)‐2,2′‐diyl bis(1‐phenylethyl)phosphoramidite) forms, upon chloride abstraction, the monosubstituted complex (aR,S,S)‐[Ir(cod)(1,2‐η‐ 1 a ,κP)]⁺ ( 3 a ), which contains a chelating P* ligand that features an η² interaction between a dangling phenyl group and iridium. Under analogous conditions, the like analogue (aR,R,R)‐ 1 a′ gives the disubstituted species (aR,R,R)‐[Ir(cod)( 1 a′ ,κP)₂]⁺ ( 4 a′ ) with monodentate P* ligands. The structure of 3 a was assessed by a combination of X‐ray and NMR spectroscopic studies, which indicate that it is the configuration of the binaphthol moiety (and not that of the dangling benzyl N groups) that determines the configuration of the complex. The effect of the relative configuration of the P* ligand on its iridium(I) coordination chemistry is discussed in the context of our preliminary catalytic results and of apparently random results obtained by other groups in the iridium(I)‐catalyzed asymmetric allylic alkylation of allylic acetates and in rhodium(I)‐catalyzed asymmetric cycloaddition reactions. Further studies with the unlike ligand (aS,R,R)‐(1,1′‐binaphthalene)‐2,2′‐diyl bis{[1‐(1‐naphthalene‐1‐yl)ethyl]phosphoramidite} ( 1 b ) showed a yet different coordination mode, that is, the η⁴‐arene–metal interaction in (aS,R,R)‐[Ir(cod)(1,2,3,4‐η‐ 1 b ,κP)]⁺ ( 3 b ).     

Halfsandwich Complexes Containing the Tetrathiotungstate Chelate Ligand. Crystal and Molecular Structure of Cp*Rh(PMe3)[(μ‐S)2WS2] (Cp* = η5‐Pentamethylcyclopentadienyl)

The reactions of Cp*M(PMe₃)Cl₂ (M = Rh ( 1a ), Ir ( 1b )) with (NEt₄)₂[WS₄] led to the heterodimetallic sulfido‐bridged complexes Cp*M(PMe₃)[(μ‐S)₂WS₂] (M = Rh ( 2a ), Ir ( 2b )), whereas the dimers [Cp*MCl(μ‐Cl)]₂ (M = Rh ( 4a ), Ir ( 4b )) reacted with (NEt₄)₂[WS₄) to give the known trinuclear compounds [Cp*M(Cl)]₂(μ‐WS₄) (M = Rh ( 5a ), Ir ( 5b )). Hydrolysis of the terminal W=S bonds converts 2a, b into Cp*M(PMe₃)[(μ‐S)₂WO₂] (M = Rh ( 3a ), Ir ( 3b )). Salts of a heterodimetallic anion, A[CpMo(I)(NO)(WS₄)] ( 6 ) (A⁺ = NEt₄⁺, NPh₄⁺) were obtained by reactions of [CpMo(NO)I₂]₂ with tetrathiotungstates, A₂[WS₄]. The complexes were characterized by IR and NMR (¹H, ¹³C, ³¹P) spectroscopy, and the X‐ray crystallographic structure of Cp*Rh(PMe₃)[(μ‐S)₂WS₂] ( 2a ) has been determined. The bond lengths and angles in the coordinations spheres of Rh and W in 2a (Rh···W 288.5(1) pm) are compared with related complexes containing terminal [WS₄^2—] chelate ligands.     

The use of half-sandwich iridium dithiolate and diselenolate complexes, Cp*Ir(L)(ER)2 (L=CO, PMe3, PPh3; ER=SPh, SePh, SeMe), for the synthesis of heterodimetallic compounds. The molecular structure of Cp*Ir(CO)(μ-SePh)2[Mo(CO)4]

Carbonyl–iridium half-sandwich compounds, Cp*Ir(CO)(EPh)₂ (E=S, Se), were prepared by the photo-induced reaction of Cp*Ir(CO)₂ with the diphenyl dichalcogenides, E₂Ph₂, and used as neutral chelating ligands in carbonylmetal complexes such as Cp*Ir(CO)(μ-EPh)₂[Cr(CO)₄], Cp*Ir(CO)(μ-EPh)₂[Mo(CO)₄] and Cp*Ir(CO)(μ-EPh)₂[Fe(CO)₃], respectively. A trimethylphosphane–iridium analogue, Cp*Ir(PMe₃)(μ-SeMe)₂[Cr(CO)₄], was also obtained. The new heterodimetallic complexes were characterized by IR and NMR spectroscopy, and the molecular geometry of Cp*Ir(CO)(μ-SePh)₂[Mo(CO)₄] has been determined by a single crystal X-ray structure analysis. According to the long Ir…Mo distance (395.3(1) Å), direct metal–metal interactions appear to be absent.     

Reactions of [Cp*Ru(H2O)(NBD)]+ with alkynes

Formal [2 + 2 + 2] addition reactions of [Cp*Ru(H₂O)(NBD)]BF₄ (NBD = norbornadiene) with PhC?CR (R = H, COOEt) give [Cp*Ru(η⁶‐C₆H₅? C₉H₈R)] BF₄ (1a, R = H; 2a, R = COOEt). Treatment of [Cp*Ru(H₂O)(NBD)]BF₄ with PhC?C? C?CPh does not give [2 + 2 + 2] addition product, but [Cp*Ru(η⁶‐C₆H₅? C?C? C?CPh)] BF₄(3a). Treatment of 1a, 2a, 3a with NaBPh₄ affords [Cp*Ru(η⁶‐C₆H₅? C₉H₈R)] BPh₄ (1b, R = H; 2b, R = COOEt) and [Cp*Ru(η⁶‐C₆H₅? C?C? C?CPh)] BPh₄(3b). The structures of 1b, 2b and 3b were determined by X‐ray crystallography. Copyright © 2007 John Wiley & Sons, Ltd.     

Chemistry of Diruthenium and Dirhodium Analogues of Pentaborane(9): Synthesis and Characterization of Metal N,S‐Heterocyclic Carbene and B‐Agostic Complexes

Building upon our earlier results on the synthesis of electron‐precise transition‐metal–boron complexes, we continue to investigate the reactivity of pentaborane(9) and tetraborane(10) analogues of ruthenium and rhodium towards thiazolyl and oxazolyl ligands. Thus, mild thermolysis of nido‐[(Cp*RuH)₂B₃H₇] ( 1 ) with 2‐mercaptobenzothiazole (2‐mbtz) and 2‐mercaptobenzoxazole (2‐mboz) led to the isolation of Cp*‐based (Cp*=η⁵‐C₅Me₅) borate complexes 5 a , b [Cp*RuBH₃L] ( 5 a : L=C₇H₄NS₂; 5 b : L=C₇H₄NOS)) and agostic complexes 7 a , b [Cp*RuBH₂(L)₂], ( 7 a : L=C₇H₄NS₂; 7 b : L=C₇H₄NOS). In a similar fashion, a rhodium analogue of pentaborane(9), nido‐[(Cp*Rh)₂B₃H₇] ( 2 ) yielded rhodaboratrane [Cp*RhBH(L)₂], 10 (L=C₇H₄NS₂). Interestingly, when the reaction was performed with an excess of 2‐mbtz, it led to the formation of the first structurally characterized N,S‐heterocyclic rhodium‐carbene complex [(Cp*Rh)(L₂)(1‐benzothiazol‐2‐ylidene)] ( 11 ) (L=C₇H₄NS₂). Furthermore, to evaluate the scope of this new route, we extended this chemistry towards the diruthenium analogue of tetraborane(10), arachno‐[(Cp*RuCO)₂B₂H₆] ( 3 ), in which the metal center possesses different ancillary ligands.