Dinuclear sulfide–thiolate complexes [Pt2(μ-S)(μ-SR)(PPh3)4] as cationic metalloligands

The cationic monoalkylated derivatives of the well-known metalloligand [Pt₂(μ-S)₂(PPh₃)₄], viz. [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ (R = n-Bu, CH₂Ph) are themselves able to act as metalloligands towards the Ph₃PAu⁺ and R′Hg⁺ (R′ = Ph or ferrocenyl) fragments, by reaction with Ph₃PAuCl or R′HgCl, respectively. The resulting dicationic products [Pt₂(μ-SR)(μ-SAuPPh₃)(PPh₃)₄]²⁺ and [Pt₂(μ-SR)(μ-SHgR′)(PPh₃)₄]²⁺ are readily isolated as their hexafluorophosphate salts, and have been fully characterised by spectroscopic techniques and an X-ray structure determination on [Pt₂(μ-SR)(μ-SHgFc)(PPh₃)₄](PF₆)₂.     

The synthesis of the tripodal phosphine CH3C{CH2P(m-CF3C6H4)2}3 and its rhodium coordination chemistry

The new tripodal phosphine CH₃C{CH₂P(m-CF₃C₆H₄)₂}₃, CF₃PPP, was prepared by reacting CH₃C(CH₂Br)₃ with Li⁺P(m-CF₃C₆H₄)₂⁻, the latter being best obtained by adding Li⁺NⁱPr₂⁻ to PH(m-CF₃C₆H₄)₂. The rhodium complexes [RhCl(CO)(CF₃PPP)], [Rh(LL)(CF₃PPP)](CF₃SO₃) (LL = 2 CO or NBD), [RhX₃(CF₃PPP)], [RhX(MeCN)₃(CF₃PPP)](CF₃SO₃)₂ (X = H and Cl), [RhCl₂(MeCN)(CF₃PPP)](CF₃SO₃) and [Rh(MeCN)₃(CF₃PPP)](CF₃SO₃)₃ were prepared and characterized. The X-ray crystal structure of [Rh(NBD)(CF₃PPP)](CF₃SO₃) is reported. The lower oxygen sensitivity of the CF₃PPP rhodium(I) complexes, relative to the corresponding species with the parent ligand CH₃C(CH₂PPh₂)₃, is attributed to the higher effective nuclear charge on the metal centers caused by the presence of the six CF₃ substituents on the terdentate phosphine. A similar effect may be responsible for the easier hydrolysis of the CF₃PPP-containing, cationic rhodium(III) complexes relative to the corresponding compounds of the parent ligand.     

Hetero-polynuclear complexes containing bridging diphenylphosphino-alkenes and -alkynes. The crystal structure of an Rh2{μ−ν:ν−P(Ph2) (CH2)3C≡CR}Co2 complex

The phosphinoalkenes Ph₂P(CH₂)_nCH=CH₂ (n= 1, 2, 3) and phosphinoalkynes Ph₂P(CH₂)_n C≡CR (R = H, N = 2, 3; R = CH₃, N = 1) have been prepared and reacted with the dirhodium complex (η−C₅H₅)₂Rh₂(μ−CO) (μ−η²−CF₃C₂CF₃). Six new complexes of the type (ν−C₅H₅)₂(Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH₃C₅H₄)Mn(CO)₂thf resulted in coordination of the manganese to the alkene function. The Rh₂---Mn complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂P(CH₂)₃CH=CH₂} (η−CH₃C₅H₄)Mn(CO)₂] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co₂(CO)₈ resulted in the coordination of Co₂(CO)₆ to the alkyne function. The Rh₂---Co₂ complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂PCH₂C≡CCH₃}Co₂(CO)₂], C₃₇H₂₅Co₂F₆O₇PRh₂, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group (C_i¹, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on |F| was 0.052 fo observed (I > 3σ(I)) reflections. The Rh₂ and Co₂ parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh₂ and perpendicular for Co₂. Attempts to induce Rh₂Co₂ cluster formation were unsuccessful.     

Slippage of η-allenyl/propargyl to an η structure and tautomerization of η-propargyl to η-allenyl in ligand addition and substitution reactions of platinum(II) complexes

Reactions of [(PPh₃)₂Pt(η³-CH₂CCPh)]OTf with each of PMe₃, CO and Br⁻ result in the addition of these species to the metal and a change in hapticity of the η³-CH₂CCPh to η¹-CH₂CCPh or η¹-C(Ph)=C=CH₂. Thus, PMe₃ affords [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺, CO gives both [trans-(PPh₃)₂Pt(CO)(η¹-CH₂CCPh)]⁺ and [trans-(PPh₃)₂Pt(CO)(η¹-C(Ph)=C=CH₂)]⁺, and LiBr yields cis-(PPh₃)₂PtBr(η¹-CH₂CCPh), which undergoes isomerization to trans-(PPh₃)₂PtBr(η¹-CH₂CCPh). Substitution reactions of cis- and trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) each lead to tautomerization of η¹-CH₂CCPh to η¹-C(Ph)=C=CH₂, with trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) affording [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺ at ambient temperature and the slower reacting cis isomer giving [trans-(PPh₃)(PMe₃)₂Pt(η¹-C(Ph)=C=CH₂)]⁺ at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) spectroscopy. The structure of [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]BPh₄·0.5MeOH was determined by single-crystal X-ray diffraction analysis.     

Alkene rotation in [Ru(η-C5H5) (L2) (η-alkene][CF3SO3] with L2 = iPr- or pTol-diazabutadiene. X-ray crystal structure of [Ru(η-C5H5(pTol-DAB) (η-ethene][CF3SO3]

Reaction of RuCl(η⁵-C₅H₅(pTol-DAB) with AgOTf (OTf = CF₃SO₃) in CH₂Cl₂ or THF and subsequent addition of L′ (L′ = ethene (a), dimethyl fumarate (b), fumaronitrile (c) or CO (d) led to the ionic complexes [Ru(η⁵-C₅H₅)(pTol-DAB)(L′)][OTf] 2a, 2b and 2d and [Ru(η⁵-C₅H₅)(pTol-DAB)(fumarontrile-N)][OTf] 5c. With the use of resonance Raman spectroscopy, the intense absorption bands of the complexes have been assigned to MLCT transitions to the iPr-DAB ligand. The X-ray structure determination of [Ru(η⁵-C₅H₅)(pTol-DAB)(η²-ethene)][CF₃SO₃] (2a) has been carried out. Crystal data for 2a: monoclinic, space group P2₁/n with A = 10.840(1), b = 16.639(1), C = 14.463(2) Å, β = 109.6(1)°, V = 2465.6(5) ų, Z = 4. Complex 2a has a piano stool structure, with the Cp ring η⁵-bonded, the pTol-DAB ligand σN, σN′ bonded (Ru-N distances 2.052(4) and 2.055(4) Å), and the ethene η²-bonded to the ruthenium center (Ru-C distances 2.217(9) and 2.206(8) Å). The C = C bond of the ethene is almost coplanar with the plane of the Cp ring, and the angle between the plane of the Cp ring and the double of the ethene is 1.8(0.2)°. The reaction of [RuCl(η⁵-C₅H₅)(PPh)₃ with AgOTf and ligands L′ = a and d led to [Ru(η⁵-C₅H₅)(PPh₃)₂(L′)]OTf] (3a) and (3d), respectively. By variable temperature NMR spectroscopy the rottional barrier of ethene (a), dimethyl fumarate (b and fumaronitrile (c) in complexes [Ru(η⁵-C₅H₅)(L₂)(η²-alkene][OTf] with L₂ = iPr-DAB (a, 1b, 1c), pTol-DAB (2a, 2b) and L = PPh₃ (3a) was determined. For 1a, 1b and 2b the barrier is 41.5±0.5, 62±1 and 59±1 kJ mol⁻¹, respectively. The intermediate exchange could not be reached for 1c, and the ΔG^# was estimated to be at least 61 kJ mol⁻. For 2a and 3a the slow exchange could not be reached. The rotational barrier for 2a was estimated to be 40 kJ mol⁻. The rotational barier for methyl propiolate (HC≡CC(O)OCH₃) (k) in complex [Ru(η⁵-C₅H₅)(iPr-DAB) η²-HC≡CC(O)OCH₃)][OTf] (1k) is 45.3±0.2 kJ mol⁻¹. The collected data show that the barrier of rotational of the alkene in complexes 1a, 2a, 1b, 2b and 1c does not correlate with the strength of the metal-alkene interaction in the ground state.     

Palladium complexes with PCP ligands.: Preparation and structural studies of two forms of [(PCP)Pd(OH2)]BF4

Abstraction of chloride from the Pd complex {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]PdCl with AgBF₄ in THF gives {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(THF)}⁺BF₄ ⁻. Attemped crystallization of this THF complex produced the aqua complex {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺BF₄ ⁻. Crystal structures of two crystalline forms of this compound are reported. In {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺BF₄ ⁻·THF, one hydrogen of the water is hydrogen bonded to the oxygen of the THF, and the other hydrogen is hydrogen bonded to an F of the BF₄ ⁻ anion. Another crystalline form has no THF, but has both of the hydrogens of water hydrogen bonded to different BF₄ ⁻ anions, such that two different BF₄ ⁻ anions bridge two {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺ cations. A crystal structure is also reported for the palladium chloride complex [η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]PdCl.     

Reactivity of {(Ph3P)Pt[μ-η-H---SiH(Ar)]}2 (Ar=2-isopropyl-6-methylphenyl) with phosphines. X-ray crystal structure of trans-{(dppe)Pt[μ-SiH(Ar)]}2

The dinuclear Pt---Si complex {(Ph₃P)Pt{μ-η²-H---SiH(IMP)]}₂ (trans-1a–cis-1b=3:1; IMP=2-isopropyl-6-methylphenyl) reacted with basic phosphines such as 1,2-bis(diphenylphosphino)ethane (dppe) and dimethylphenylphosphine (PMe₂Ph) to afford different dinuclear Pt---Si complexes with loss of H₂, {(P)₂Pt[μ-SiH(IMP)]}₂ [P=dppe, trans-2a (major), cis-2b (trace); PMe₂Ph, 3 (trans only)]. Complexes 2 and 3 were characterized by multinuclear NMR spectroscopy and X-ray crystallography (2a). In contrast, the reaction of 1a,b with the sterically demanding tricyclohexylphosphine (PCy₃) afforded {(Cy₃P)Pt{μ-η²-H---SiH(IMP)]}₂ (trans-4a–cis-4b 2:1) analogous to 1a,b where the central Pt₂Si₂(μ-H)₂ core remains intact but the PPh₃ ligands have been replaced by PCy₃. Complexes 4a and 4b was characterized by multinuclear NMR and IR spectroscopies.     

Mixed-metal butterfly acetamidediato clusters derived from a highly reactive ruthenium oxo cluster: synthesis and characterization of [(PPh3)2N][MRu3(CO)12(η-μ3-NC(μ-O)CH3)], (M = Mn or Re)

Analogy with the isolable oxo cluster [Fe₃(CO)₉(μ₃-O)]²⁻, which is structurally interesting and synthetically useful, prompted the present attempt to synthesize its ruthenium analog. Although the high reactivity of [Ru₃(CO)₉(μ₃-O)]²⁻ (I) prevented its isolation, the reaction of this species with [M(CO)₃(NCCH₃)]⁺, where M = Mn or Re, yields [PPN][MRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃]⁻. The high nucleophilicity of the oxo ligand in [Ru₃(CO)₉(μ₃-O)]²⁻ (I) appears to be responsible for the conversion of acetonitrile to an acetamidediato ligand and for the instability of I. The crystal structure of [PPN][MnRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃)]] reveals a hinged butterfly array of metal atoms in which the acetamidediato ligand bridges the two wings with μ₃-N bonding to an Mn and two Ru atoms, and μ-O bonding to an Ru atom.     

Heterobimetallic chloro bridgedcomplexes of (η:η−C10H16)-ruthenium(IV) with palladium(II), platinum(II), rhodium(III), iridium(III), copper(I) and rhodium(I)

Metathesis of [(η³:η³−C₁₀H₁₆)Ru(Cl) (μ−Cl)]₂ (1) with [R₃P) (Cl)M(μ-Cl)]₂ (M = Pd, Pt), [Me₂NCH₂C₆H₄Pd(μ-Cl)]₂ and [(OC)₂Rh(μ-Cl)]₂ affords the heterobimetallic chloro bridged complexes (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂M(PR₃)(Cl) (M = Pd, Pt), (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂PdC₆H₄CH₂NMe₂ and (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂Rh(CO)₂, respectively. Complex 1 reacts with [Cp^*M(Cl) (μ-Cl)]₂ (M = Rh, Ir), [p-cymene Ru(Cl) (μ-Cl]₂ and [(Cy₃P)Cu(μ-Cl)]₂ to give an equilibrium of the heterobimetallic complexes and of educts. The structures of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂Pd(PR₃) (Cl) (R = Et, Bu) and of one diastereoisomer of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂IrCp^*(Cl) were determined by X-ray diffraction.     

Cis- and trans-titanium complexes with doubly silyl-bridged dicyclopentadienyl ligands: molecular structure of [(TiCl)2(μ-O){(SiMe2)2(η-C5H3)2}]2(μ-O)2

The reaction of TiCl₄ with Li₂[(SiMe₂)₂(η⁵-C₅H₃)₂] in toluene at room temperature afforded a mixture of cis- and trans-[(TiCl₃)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] in a molar ratio of 1/2 after recrystallization. The complex trans-[(TiCl₃)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] was hydrolyzed immediately by the addition of water to THF solutions to give trans-[(TiCl₂)₂(μ-O){(SiMe₂)₂(η⁵-C₅H₃)₂}] as a solid insoluble in all organic solvents, whereas hydrolysis of cis-[(TiCl₃)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] under different conditions led to the dinuclear μ-oxo complex cis-[(TiCl₂)₂)(μ-O){(SiMe₂)₂(η⁵-C₅H₃)₂}] and two oxo complexes of the same stoichiometry [(TiCl)₂(μ-O){(SiMe₂)₂(η⁵-C₅H₃)₂}]₂(μ-O)₂ as crystalline solids. Alkylation of cis- and trans-[(TiCl₃)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] with MgCIMe led respectively to the partially alkylated cis-[(TiMe₂Cl)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] and the totally alkylated trans-[(TiMe₃)₂{(SiMe₂)₂(η⁵-C₅H₃)₂}] compounds. The crystal and molecular structure of the tetranuclear oxo complex [(TiCl)₂(μ-O){(SiMe₂)₂(η⁵-C₅H₃)₂}]₂(μ-O)₂ was determined by X-ray diffraction.     

Synthesis and properties of the dichloro [tetramethyl (trifluoromethyl)cyclopentadienyl]ruthenium dimer: X-ray structure of [M2(η-C5Me4CF3)2Cl2(μ-Cl)2] (M=Ru, Rh)

The reaction of RuCl₃(H₂O), with C₅Me₄CF₃J in refluxing EtOH gives [Ru₂(η⁵-C₅Me₁CF₂)₂ (μ-Cl₂] (20 in 44% yield. Dimer 2 antiferromagnetic (−2J=200 cm¹). The crystal structures of 2 (rhombohedral system, R3 space group, Z=9, R=0.0589) and [Rh₂(η⁵-C₅Me₄CF₃(₂Cl₂(μ-Cl)₂] (3) (rhombohedral system. space group, Z = 9, R = 0.0641) were solved; both complexes have dimeric structures with a trans arrangement of the η⁵-C₅Me₄CF₄ rings. Comparison of the geometry of 2 and 3 with those of the corresponding η⁵-C₅Me₅ complexes shows that lowering the ring symmetry causes significant distortion of the M₂(μ-Cl)₂ moiety. The analysis of the MCl₃ fragment conformations in 2 and 3 and in the η⁵-C₅ME₅ analogues shows that they are correlated with the M---M distances. The Cl atoms are displaced by Br on reaction of 2 with KBr in MeOH to give the diamagnetic dimer [Ru₂(η⁵-C₅Me₄CF₃)₂Br₂ (μ-Br₂] (4). Complex 2 reacts with O₂ in CH₂Cl₂ solution at ambient temperature to form a mixture of isomeric η⁶-fulvene dimers [Ru₂(η⁶-C₅Me₃CF₃ = CH₂)₂Cl₂(μ-Cl)₂] (5). Reactions of 5 with CO and allyl chloride give Ru(η⁵-C₅Me₃CF₃CH₂Cl)(CO)₂Cl (6) and Ru(η⁵-C₅Me₃CF₃CF₃CH₂Cl)(η³-C₃H₅)Cl₂ (7) respectively.     

Comparison in halide binding ability between the unsaturated clusters [Pd3(μ-dppm)3(CO)] and [PdPtCo(μ-dppm)2(CO)3(CNBu)] (dppm = Ph2PCH2PPh2)

The trinuclear clusters [Pd₃(μ-dppm)₃(CO)]²⁺ and [PtPdCo(μ-dppm)₂(CO)₃(CN^tBu)]⁺ exhibit a large and a small cavity, respectively, formed by the phenyl rings of the bridging diphosphine ligands. Their binding constants (K₁₁) with halide ions (X⁻) were obtained by UV-Vis spectroscopy. The binding ability varies as I⁻ > Br⁻ > Cl⁻, and [Pd₃(μ-dppm)₃(CO)]²⁺ > [ptPdCo(μ-dppm)₂-(CO)₃(CN^tBu)]⁺. The MO diagram for the related cluster [Pd₂Co(μ-dppm)₂(CO)₄]⁺ has been addressed theoretically in order to predict the nature of the lowest energy electronic bands. For this class of compounds, the lowest energy bands are assigned to charge transfers from the Co center to the Pd₂ centers.     

Kinetics and mechanisms of ligand substitution reactions of molybdenum SO2 complexes. Synthesis and X-ray structure of trans-Mo(CO)2 (dmpe) (PPh3) (SO2)

Kinetic results are reported for intramolecular PPh₃ substitution reactions of Mo(CO)₂(η¹-L)(PPh₃)₂(SO₂) to form Mo(CO)₂(η²-L)(PPh₃)(SO₂) (L = DMPE = (Me)₂PC₂H₄P(Me)₂ and dppe=Ph₂PC₂H₄PPh₂) in THF solvent, and for intermolecular SO₂ substitutions in Mo(CO)₃(η²-L)(η²-SO₂) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH₂Cl₂ solvent. Activation parameters for intramolecular PPh₃ substitution reactions: ΔH^≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; ΔS^≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO₂ in MO(CO)₃(η²-L)(η²-SO₂) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO₂ to accept a pair of electrons from the metal, with its bonding transformations of η²-SO₂ to η¹-pyramidal SO₂, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO)₂(dmpe)(PPh₃)(SO₂) was determined crystallographically: P2₁/c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) ų, Z=4, R(F)=3.49%.     

Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2

A series of cationic nickel complexes [(η³-methally)Ni(PP(O))]SbF₆ (1–4) [PP(O) = Ph₂P(CH₂)P(O)Ph₂ (dppmO) (1), Ph₂P(CH₂)₂P(O)Ph₂ (dppeO) (2), Ph₂P(CH₂)₃P(O)Ph₂ (dpppO) (3), pTol₂P(CH₂)P(O)pTol₂ (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η³-methally)NiBr]₂ with biphosphine monoxides and AgSbF₆. The ligands are coordinated in a bidentate way. Starting from [(η³-all)PdI]₂ the cationic complexes [(η³-all)PP(O))]Y (8–14). [PP(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF₄, SbF₆, CF₃SO₃, pTolSO₃] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η³-all)Pd(I)(PP(O)-κ¹-P)] (5–7) [PP(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(PP(O))] (15–18). [PP(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl₂]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph₂P(CH₂-P(O)Ph₂-κ²-P,O};] · CH₂Cl₂ (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction.     

The interaction of Lewis acidic boron derivatives with Re(CO)5−nH(PMe3)n complexes

Lewis acid adducts of the hydrides cis- and trans-Re(CO)(PMe₃)₄H (1) and (2), mer-Re(CO)₂(PMe₃)₃H (3), fac-Re(CO)₂(PMe₃)₃H (4) and trans-Re(CO)₃(PMe₃)₂H (5) were studied with BH₃ and 9-borabicyclo[3,3,1] norbonane (BBNH). Using BH₃·THF and (BBNH)₂ 1 and 2 afforded Re(CO)(PMe₃)₃(η²-BH₄) (6) and Re(CO)(PMe₃)₃(η²-BBNH₂) (7) as stable and isolable products. VT IR studies established for the reaction to 7 that BBNH first attaches in a pre-equilibrium to the O_CO atom of 1 or 2. At higher temperatures ReH adduct formation occurs with instantaneous transformation to 7 and elimination of PMe₃·BBNH. In a similar way, the hydrides 3 and 4 were converted with BH₃·THF and (BBNH)₂ to yield the stable complexes Re(CO)₂(PMe₃)₂(η²-BH₄) (8) and Re(CO)₂(PMe₃)₂(η²-BBNH₂) (9). The intermediacy of the η¹-BH₄ adducts mer-/fac-Re(CO)₂(PMe₃)₃(η¹-BH₄) was confirmed by VT ¹H, ³¹P NMR and VT IR experiments. The conversion of 5 with BH₃·THF led to equilibria with adducts at the O_CO terminus in trans position to H and with H_Re as revealed by VT IR studies. Temperature dependent ³¹P equilibrium studies allowed to calculate ΔH=−4.9 kcal mol⁻¹ and ΔS=+0.034 e.u. for this reaction. These adducts could not be isolated. Compound 5 does not react with (BBNH)₂ even at elevated temperatures. DFT calculations were carried out to support the structures of the BH₃ adducts of 5. In addition a vibrational analysis helped to unravel the IR band assignments of the involved compounds. DFT calculations on 8 confirmed its C_2v structure. X-ray diffraction studies were carried out on single crystals of 6 and 7.     

Structure of [Ni(dippe)(μ-S)]2 and its reaction products. The nucleophilicity of the Ni2S2 fragment

The dimer [(dippe)Ni(μ-S)]₂ reacts with organic electrophiles to give the alkylated species [(dippe)₂Ni₂(μ-S)(μ-SR)]⁺. Stronger alkylating agents lead to double alkylation and cleavage of the dimer. Protonation similarly occurs with strong acids. The structures of several of these species have been determined.     

Mechanistic details for metathetical exchange between XCO (X = O and RN) and the tin(II) dimer, {Sn[N(SiMe3)2] (μ-OBu)}2

Metathetical exchange between carbon dioxide and the tin(II) dimer, {Sn[N(SiMe₃)₂](μ-OBu¹)}₂ (3) has been observed to cleanly produce the two new heteroleptic tin(II) dimers, Sn[N(SiMe₃)₂](μ-OBu^t)₂Sn(OSiMe₃) (6) and [Sn(OSiMe₃)](μ-OBu^t)]₂ (7]). In addition, reaction of 3 with I equiv, of tert-butylisocyanate (8), at 25°C, quantitatively provides 6, and with 2 equiv., quantitatively provides 7. Likewise 6 reacts with 1 equiv, of 8 to quantitatively provide 7. The mechanism for these latter processes has been investigated by low temperature ¹H NMR spectroscopy which reveals that metathetical exchange does not involve the tri-coordinate tin(II) centers of the dimeric structures, but rather, it occurs, in each case, via the transient monomeric tin(II) species, Sn[N(SiMe₃)₂](μ-OBu^t) (4), that undergoes metathesis to produce, initially the open dimer intermediate, Sn(OCNBu^t)(OSiMe₃)(μ-OBu^t)Sn(OBu^t) (OSiMe₃) (12), that is observed at −10°C. Subsequent redistribution reactions then generate the final products that are observed. Together, these mechanistic details provide additional support for the ‘monomeric tin(II)’ hypothesis proposed earlier for metathetical exchange between XCO and Sn[N (SiMe₃)₂]₂ (1).     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

In situ IR and NMR study of the interactions between proton donors and the Re(I) hydride complex [{MeC(CH2PPh2)3}Re (CO)2H]. ReH…H bonding and proton-transfer pathways

The reactions of various proton donors (phenol, hexafluoro-2-propanol, perfluoro-2-methyl-2-propanol, monochloroacetic acid, and tetrafluoroboric acid) with the rhenium (I) hydride complex [(triphos)Re(CO)₂H] (1) have been studied in dichloromethane solution by in situ IR and NMR spectroscopy. The proton donors from [(triphos)Re(CO)₂H…HOR] adducts exhibiting rather strong H…H interactions. The enthalpy variations associated with the formation of the H-bonds (−ΔH = 4.4–6.0 kcal mol⁻¹) have been determined by IR spectroscopy, while the H…H distance in the adduct [(triphos)Re(CO)₂H…HOC(CF₃)₃] (1.83 Å) has been calculated by NMR spectroscopy through the determination of the T_1min relaxation time of the Re---H proton. It has been shown that the [(triphos)Re(CO)₂H…HOR] adducts are in equilibrium with the dihydrogen complex [(triphos)Re(CO)₂(η²-H₂)]⁺, which is thermodynamically more stable than any H-bond adduct.     

Dissolution of [RhCl(PPh3)3] in the ionic liquid, 1-ethyl-3-methyl imidazolium chloroaluminate(III), and its reaction with H2. The stabilization of Rh(I) species in an ionic liquid

The solution of [RhCl(PPh₃)₃] in acidic 1-ethyl-3-methylimidazolium chloroaluminate(III) ionic liquid (AlCl₃ molar fraction, x_AlCl3=0.67) was investigated by ¹H and ³¹P{¹H} NMR. One triphenyl phosphine is lost from the complex and is protonated in the acidic media, and cis-[Rh(PPh₃)₂ClX], (2), where X is probably [AlCl₄]⁻, is formed. On, standing, 2 is converted to trans-[Rh(H)(PPh₃)₂X], (3). The reaction of 2 and H₂ also produces trans-[Rh(H)(PPh₃)₂X], (3). ¹H and ³¹P{¹H} NMR support the suggestion that a weak ligand such as [AlCl₄]⁻, present in solution may interact with the metal centre. When [RhCl(PPh₃)₃] is dissolved in CH₂Cl₂/AlCl₃/HCl for comparison, two exchanging isomers of what is probably [RhH{(μ-Cl)₂AlCl₂}{(μ-Cl)AlCl₃}(PPh₃)₂], (6) and (7), are formed.