Reduction of α,β unsaturated carbonyl compounds by Ni–BH4

The reduction of α,β unsaturated carbonyl compounds by sodiumborohydride is catalysed by Ni(bpy)Cl₂ (bpy=2,2′-bipyridine). Various carbonyl compounds having the general formula R₁CH=CHCRO [where R₁, R=C₆H₅, H; p-MeO---C₆H₄---,C₆H₄; p-CH₃---C₆H₄, C₆H₅; (m-OMe---)(p-OMe---)C₆H₃, C₆H₅; C₆H₅, (CH₃)₂CH---; CH₃, H; m-Br---C₆H₄---, C₆H₅] are reduced to corresponding allylicalcohol [R₁CH=CHCRHOH] at 25°C within half an hour. During these reductions the double bond is partially reduced to give saturated alcohols as minor products having the molecular formula R₁CH₂CH₂CRHOH. The reduction of trans-3-phenyl-2-propenal with NaBH₄ and catalytic amounts of Ni(bpy)Cl₂ in solvents containing active deuterium (D₂O, CD₃OD), leads to the partial incorporation of deuterium at the α and γ positions to give C---D bonded alcohols.     

Stereoisomerism of dihalodiaryl(acetylacetonato)-antimony(V) compounds

A series of dihalodiaryl(acetylacetonato)antimony(V) compounds, (p-Y-C₆H₄)₂SbX₂Acac (X=F, Cl, Br; Y=NO₂, Cl, H, CH₃, CH₃O), were prepared. All of these compounds are monomeric and exist in solution as a mixture of two isomers both with chelated hexacoordinate configurations. From the temperature- and solvent-dependent PMR spectra of these compounds, it is concluded that the two isomers are in equilibrium in solution. The assignments of the PMR signals to the isomers were made by considering the effects of solvent and the substituents X and Y on the spectra.     

Synthesis, reactions and X-ray crystal structures of metallacrown ethers with unsymmetrical bis(phosphinite) and bis(phosphite) ligands derived from 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂ (1) and 2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈) (2). These ligands react with Mo(CO)₄(nbd) to form the monomeric metallacrown ethers, cis-Mo(CO)₄{2-Ph₂PO(CH₂CH₂O)₂–C₁₂H₈-2′-OPPh₂} (cis-3) and cis-Mo(CO)₄{2-(2,2′-O₂C₁₂H₈)P(CH₂CH₂O)₂–C₁₂H₈-2′-P(2,2′-O₂C₁₂H₈)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different ¹³C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis–trans isomerization in the presence of HgCl₂. Although the cis–trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis–trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4.     

Cyclopentadienyl-ruthenium and -osmium chemistry : XXXIX. Syntheses of novel alkynyl-ruthenium complexes. X-Ray structures of two forms of {Ru(PPh3)2(η-C5H5)}2(μ-C4) and of Ru{CCC(O)Me}(PPh3)2(η-C5H5)

Reactions between [Ru(thf)(PPh₃)₂(η-C₅H₅)]⁺ and lithium acetylides have given further examples of substituted ethynylruthenium complexes that are useful precursors of allenylidene and cumulenylidene derivatives. From Li₂C₄, mono- and bi-nuclear ruthenium complexes were obtained: single-crystal X-ray studies have characterised two rotamers of {Ru(PPh₃)₂(η-C₅H₅)}₂(μ-C₄), which differ in the relative cis and trans orientations of the RuL_n groups. Protonation of Ru(CCCCH)(PPh₃)₂(η-C₅H₅) afforded the butatrienylidene cation [Ru(C=C=C=CH₂)(PPh₃)₂(η-C₅H₅)]⁺, which reacted readily with atmospheric moisture to give the acetylethynyl complex Ru{CCC(O)Me}(PPh₃)₂(η-C₅H₅), also fully characterised by an X-ray structural study.     

Nucleophilic addition of water to coordinated dipyridylethylene in rhenium(V) complexes

Complexes of general formula [ReOX₂{(C₅H₄N)CH(O)CH₂(C₅H₄N)}] (X?=?Cl,?I) were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] and trans-[ReOI₂(OEt)(PPh₃)₂] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. The coordinated DPE ligand undergoes addition of water at the ethylenic carbon atoms, and the (C₅H₄N)CH(O)CH₂(C₅H₄N) moiety acts as a uninegative terdentate N,O,N-donor ligand. X-ray crystal structures of both complexes have been determined and show distorted octahedral geometry at the rhenium(V) centre.     

Lithiated γ-O-functionalized propyl phenyl sulfides and sulfones of the type Li[CH(SOxPh)CH2CH2OR] (x = 0, 2). [Li{CH(SPh)CH2CH2Ot-Bu}(tmeda)] – A structurally characterized organolithium inner complex

Lithiation of O-functionalized alkyl phenyl sulfides PhSCH₂CH₂CH₂OR (R = Me, 1a; i-Pr, 1b; t-Bu, 1c; CPh₃, 1d) with n-BuLi/tmeda in n-pentane resulted in the formation of α- and ortho-lithiated compounds [Li{CH(SPh)CH₂CH₂OR}(tmeda)] (α-2a–d) and [Li{o-C₆H₄SCH₂CH₂CH₂OR)(tmeda)] (o-2a–d), respectively, which has been proved by subsequent reaction with n-Bu₃SnCl yielding the requisite stannylated γ-OR-functionalized propyl phenyl sulfides n-Bu₃SnCH(SPh)CH₂CH₂OR (α-3a–d) and n-Bu₃Sn(o-C₆H₄SCH₂CH₂CH₂OR) (o-3a–d). The α/ortho ratios were found to be dependent on the sterical demand of the substituent R. Stannylated alkyl phenyl sulfides α-3a–c were found to react with n-BuLi/tmeda and n-BuLi yielding the pure α-lithiated compounds α-2a–c and [Li{CH(SPh)CH₂CH₂OR}] (α-4a–b), respectively, as white to yellowish powders. Single-crystal X-ray diffraction analysis of [Li{CH(SPh)CH₂CH₂Ot-Bu}(tmeda)] (α-2c) exhibited a distorted tetrahedral coordination of lithium having a chelating tmeda ligand and a C,O coordinated organyl ligand. Thus, α-2c is a typical organolithium inner complex.Lithiation of O-functionalized alkyl phenyl sulfones PhSO₂CH₂CH₂CH₂OR (R = Me, 5a; i-Pr, 5b; CPh₃, 5c) with n-BuLi resulted in the exclusive formation of the α-lithiated products Li[CH(SO₂Ph)CH₂CH₂OR] (6a–c) that were found to react with n-Bu₃SnCl yielding the requisite α-stannylated compounds n-Bu₃SnCH(SO₂Ph)CH₂CH₂OR (7a–c). The identities of all lithium and tin compounds have been unambiguously proved by NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn).     

Trichloro-mono- β -diketonato oxorhenium(V) complexes: synthesis,characterization and crystal structure

Oxorhenium(V) complexes of β-diketonate systems have been synthesized and isolated in pure form. The red complexes n-Bu₄N[ReO(R₁COCHCOR₂)Cl₃] (acac, R₁=R₂=CH₃; bzac, R₁=CH₃ and R₂=C₆H₅; bzbz, R₁=R₂=C₆H₅) have been characterized by elemental analyses, spectroscopic and other physico-chemical tools. One complex, n-Bu₄N[ReO(bzbz)Cl₃] (1c) has been subjected to single-crystal X-ray analysis. In the structure of the anion, the metal has a six-coordinate octahedral environment in which the bidentate β-diketone ligand is cis and trans to the terminal oxygen.     

Preparation and electrochemical behaviour of dinuclear platinum complexes containing NCN ligands (NCN=[C6H3(Me2NCH2)2-2,6]). The crystal structure of [C6H3(Me2NCH2)2-1,3-(CC)-5]2

A series of homodinuclear Pt compounds containing the anionic, potentially terdentate NCN ligand (NCN=[C₆H₃(Me₂NCH₂)₂-2,6]⁻) or its 4-ethynyl derivative were prepared. The two platinum centres are linked together in two different fashions: (i) directly linked by an ethynyl or diethynylphenyl group (head-to-head) and (ii) indirectly bonded by a ethynyl- or butadiynyl-linked bis-NCN ligand (tail-to-tail). The reaction of the head-to-head σ,σ′-ethynylide complex {Pt}CC{Pt} ({Pt}=[Pt(C₆H₃{CH₂NMe₂}₂-2,6)]⁺) with [CuCl]_n yields {Pt}Cl and [Cu₂C₂]_n, while with [Cu(NCMe)₄][BF₄] a Cu(I) bridged complex was formed: [(η²-{Pt}CC{Pt})₂Cu][BF₄]. The results of cyclic voltammetry experiments reveal that both connection modes of the two platinum centres lead to electrochemically independent Pt–NCN units. The X-ray crystal structure analysis of the neutral, tail-to-tail bridging butadiyne bis-NCNH ligand [C₆H₃(CH₂NMe₂)-1,3-(CC)-5]₂ is reported.     

Reactions of nickelocene with lithium and magnesium alkyls containing β-hydrogen atoms

The reaction of nickelocene with BrMgR, where R=CH₂CH(CH₃)C₆H₅, C₂H₅, (CH₂)₇CH₃ and CH₂CH₂CH₃, have been studied. It was found that the presence of β-hydrogen in R did not cause the total splitting of the carbon–nickel bond but alkylidynetrinickel clusters were formed. It is the first example of the synthesis of alkylidynetrinickel clusters (NiCp)₃CR′ from the organonickel species possessing β-hydrogen. Besides trinickel clusters, the following compounds were always formed in all the studied reactions: (NiCp)₄H₂, (NiCp)₆, CpNi(η³-C₅H₇) and (NiCp)₂(μ-C₅H₆). The structure of (NiCp)₃CCH(CH₃)Ph has been determined by a single-crystal X-ray diffraction study.     

Unusual stabilization of cationic “M(η-allyl) (M = Pt, Pd) units by a dianionic cis-{Pt(C6F5)2(CCSiMe3)2} fragment

Chloride abstraction from [{M(η³ --- C₃H₅)Cl}_n] (M = Pt, n = 4 or M = Pd, n = 2) by (NBu₄)₂[cis-Pt(C₆F₅)₂(CCSiMe₃)₂] (1) gives rise to novel homo- and hetero-dinuclear zwitterionic derivatives (NBu₄) [{cis-Pt(C₆F₅)₂(CCSiMe₃)₂}M(η³-C₃H₅)] (M = Pt 2; M = Pd 3) which are formed by a M(η³-allyl)⁺ unit attached to both alkynyl ligands of the {cis-Pt(C₆F₅)₂(CCSiMe₃)₂}²⁻ fragment. The structure of 3 has been established by X-ray diffraction.     

The stereochemistry of the dichlorocobalt(III) complexes with (2S,5S,9S)- and (2S,5R,9S)-trimethyltriethylenetetraamines

Dichlorocobalt(III) complexes of (2S,5S,9S)-trimethyltriethylenetetraamine (L₁) and (2S,5R,9S)-trimethyltriethylenetetraamine (L₂) have been prepared. Both L₁ and L₂ coordinate to the cobalt(III) ion to give three isomers: Λ-cis-α, Δ-cis-β, trans isomers for L₁ and Δ-cis-α, Δ-cis-β, trans isomers for L₂. Each of the trans-dichloro complexes of the two ligands have been isomerized stereospecifically to the cis-α-dichloro complex in methanol, and each of the cis-α-dichloro complexes stereospecifically to the trans-diaqua complex in water. Both the geometrical and optical inversions took place at the same time in the observed stereospecific isomerizations.     

l-Hydroxo/Alkoxo-l-oxo-l-sulfonato-jO:jO'-bis[trichloroantimon(V)]Verbindungen. Zweikernige Antimon(V)-Komplexe mit Sulfonatgruppen als überbrückenden Liganden

l-Hydroxo/alkoxo-l-oxo-l-sulfonato-jO:jO'-bis[trichloroantimony(V)] Compounds. Binuclear Antimony(V) Complexes with Sulfonate Groups as bridging Ligands Sulfonic acids react with antimony(V) chloride and water and water/alcohol resp. dependent of the molar ratios yielding Cl₃SbO(OH)(O₂S(O)CH₃)SbCl₃ ( 1 ), Cl₃SbO(OH)· (O₂S(O)CF₃)SbCl₃ ( 3 ) the monohydrate Cl₃SbO(OH)· (O₂S(O)CH₃)SbCl₃·H₂O ( 2 ) and the compounds Cl₃SbO(OR')(O₂S(O)CF₃)SbCl₃ ( 4 : R'=CH₃; 5 : R'=C₂H₅) and Cl₃SbO(OCH₃)(O₂S(O)C₂H₅)SbCl₃ ( 6 ) resp. The crystal and molecular structures of 1 to 3 , 5 and 6 are determined. 1 and 3 are associated by hydrogen bonds to dimers and crystallize monoclinic ( 1 : P2₁/c; 3 : P2₁/n). 2 is a hydroxonium salt H₃O⁺[Cl₃SbO₂(O₂S(O)CH₃)SbCl₃]^– with strong hydrogen bonds between cations and anions and crystallizes triclinic (P1). 5 and 6 crystallize monoclinic ( 5 : P2₁/m; 6 : P2₁/c). In 1 and 3 to 6 there is an intramolecular reorientation or an intermolecular exchange of protons and R' groups in solution. The NMR spectra are discussed.     

Thermal isomerization of ruthenium hydride compounds containing asymmetric bidentate pyrrole‐imine ligands

A series of ruthenium hydride compounds containing substituted bidentate pyrrole‐imine ligands were synthesized and characterized. Reacting RuHCl(CO)(PPh₃)₃ with one equivalent of [C₄H₃NH(2‐CH=NR)] in ethanol in the presence of KOH gave compounds {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NR)]} where trans‐Py‐Ru‐H 1, R = CH₂CH₂C₆H₉; cis‐Py‐Ru‐H 2, R = Ph‐2‐Me; and cis‐Py‐Ru‐H 3, R = C₆H₁₁. Heating trans‐Py‐Ru‐H 1 in toluene at 70°C for 12 hr resulted a thermal conversion of the trans‐Py‐Ru‐H 1 into its cis form, {RuH(CO)(PPh₃)₂[C₄H₃N(2‐CH=NCH₂CH₂C₆H₉)]} (cis‐Py‐Ru‐H 1) in very high yield. The ¹H NMR spectra of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 2, cis‐Py‐Ru‐H 3, and cis‐Py‐Ru‐H 1 all show a typical triplet at ca. δ–11 for the hydride. The trans and cis form indicate the relative positions of pyrrole ring and hydride. The geometries of trans‐Py‐Ru‐H 1, cis‐Py‐Ru‐H 1, and cis‐Py‐Ru‐H 3 are relatively similar showing typical octahedral geometries with two PPh₃ fragments arranged in trans positions.     

Übergangsmetall-fulven-komplexe : XXVIII. Reaktionen von (fulven)Cr(CO)3-komplexen und α-ferrocenyl-carbeniumionen mit nukleophilen

Tricarbonyl(fulvene)chromium complexes react with anionic nucleophiles to give functionally substituted cyclopentadienyl derivatives. The nucleophilic attack occurs at the exocyclic carbon atom of the fulvene ligand. Addition of PPh₂⁻ to (η⁶-6,6-dimethylfulvene)Cr(CO)₃ (1) yields the novel anion [(η⁵-C₅H₄C(CH₃)₂PPh₂)Cr-(CO)₃]⁻, which can be isolated as a K⁺, (C₂H₅)₄N⁺, (C₆H₅)₄P⁺, or Tl⁺ derivative (2–5). The potassium salt of the uncoordinated C₅H₄C(CH₃)₂PPh₂⁻ anion (7) is obtained by treatment of 6,6-dimethylfulvene with KPPh₂·2C₄H₈O₂. Similarly, NaC₅H₅ reacts with 1 to give Na[(η⁵-C₅H₄C(CH₃)₂C₅H₅)Cr(CO)₃] (8). The reactions of (6-dimethylaminofulvene)Cr(CO)₃ (15) with nucleophiles are accompanied by elimination of dimethylamine. Addition of Ph₃P=CH₂ to 15 gives an unstable product, but after reaction of 6-dimethylaminofulvene with Ph₃P=CH₂, the free ligand C₅H₄=CHCH=PPh₃ (17) can be isolated in moderate yields. Deeply colored anions of the type [(η⁵:η⁵-C₅H₄C(R)=C₅H₄)Cr₂(CO)₆]⁻ (R = H, N(CH₃)₂) are synthesized by reaction of 15 or (6-dimethylamino-6-methylthiofulvene)Cr(CO)₃ with NaC₅H₅ and subsequent complexation of the mononuclear intermediate with (CH₃CN)₃Cr(CO)₃. In addition, the synthesis of the new fulvene complexes [C₅H₄=CH(CH=CH)₂N(CH₃)Ph]M(CO)₃ (23, 24; M = Cr, Mo) is described. The investigation is extended to α-ferrocenylcarbenium ions, which are isoelectronic with (fulvene)Cr(CO)₃ complexes. [(η⁵-C₅H₅)Fe(C₅H₄CPh₂)]⁺ BF₄⁻ (25) adds tertiary phosphines at the exocyclic carbon atom to give phosphonium salts of the type [(η⁵-C₅H₅)Fe(C₅H₄CPh₂PR₃)]⁺BF₄⁻. A CO-substititution product of a tricarbonyl (fulvene)chromium complex is obtained for the first time by irradiation of (η⁶-6,6-diphenylfulvene)Cr(CO)₃ in the presence of PPh₃. In addition, an improved synthesis of the (CH₃CN)₃M(CO)₃ complexes (M = Cr, Mo, W) is reported.     

Chloridobis[2‐(diphenylphosphanyl)ethanamine‐κ2P,N](triphenylphosphane‐κP)ruthenium(II) chloride toluene monosolvate

The aminophosphane ligand 1‐amino‐2‐(diphenylphosphanyl)ethane [Ph₂P(CH₂)₂NH₂] reacts with dichloridotris(triphenylphosphane)ruthenium(II), [RuCl₂(PPh₃)₃], to form chloridobis[2‐(diphenylphosphanyl)ethanamine‐κ²P,N](triphenylphosphane‐κP)ruthenium(II) chloride toluene monosolvate, [RuCl(C₁₈H₁₅P)(C₁₄H₁₆NP)₂]Cl·C₇H₈ or [RuCl(PPh₃){Ph₂P(CH₂)₂NH₂}₂]Cl·C₇H₈. The asymmetric unit of the monoclinic unit cell contains two molecules of the Ru^II cation, two chloride anions and two toluene molecules. The Ru^II cation is octahedrally coordinated by two chelating Ph₂P(CH₂)₂NH₂ ligands, a triphenylphosphane (PPh₃) ligand and a chloride ligand. The three P atoms are meridionally coordinated, with the Ph₂P– groups from the ligands being trans. The two –NH₂ groups are cis, as are the chloride and PPh₃ ligands. This chiral stereochemistry of the [RuCl(PPh₃){Ph₂P(CH₂)₂NH₂}₂]⁺ cation is unique in ruthenium–aminophosphane chemistry.     

Bis(diphenylphosphino)methane trimethylphosphine alkyl and η-cyclopentadienyl compounds of rhodium(I); P{H} two dimensional δ/J resolved and Overhauser effect nuclear magnetic resonance spectroscopy

Neutral mononuclear tertiary phosphine rhodium(I) complexes of the formula RhX(PMe₃)(dppm), X = Cl, CH₂SiMe₃, CH₂CMe₃, CH₂CMe₂Ph, η⁵-C₅H₅, DPPM = bis(diphenylphosphino)methane, RhCl(PPh₃)(dppm), RhX(dppm)₂, X = Cl, Me and Rh(η⁵-C₅H₅(dppm) have been synthesised. In Rh(η⁵-C₅H₅)(PMe₃)(dppm), the dppm ligand is unidentate according to ³¹P{¹H} NMR and X-ray data.The ³¹P{¹H} NMR spectral parameters of RhX(PR₃)(dppm) have been determined by a combination of two dimensional δ/J resolved spectroscopy and heteronuclear nuclear Overhauser effect difference spectroscopy (NOEDS) in conjunction with iterative analysis of the one dimensional spectra.     

Synthesis, structure and DNA binding studies of mononuclear copper(II) complexes with mixed donor macroacyclic ligands, 2,6-bis({N-[2&3-(phenylselenato)alkyl]}benzimidoyl)-4-methylphenol

Two new phenol based macroacyclic Schiff base ligands, 2,6-bis({N-[2-(phenylselenato)ethyl]}benzimidoyl)-4-methylphenol (bpebmpH, 1) and 2,6-bis({N-[3-(phenylselenato)propyl]}benzimidoyl)-4-methylphenol (bppbmpH, 2) of the Se₂N₂O type have been prepared by the condensation of 4-methyl-2,6-dibenzoylphenol (mdbpH) with the appropriate (for specific reactions) phenylselenato(alkyl)amine. These ligands with Cu(II) acetate monohydrate in a 2:1 molar ratio in methanol form complexes of the composition [(C₆H₂(O)(CH₃){(C₆H₅)CN(CH₂)_nSe(C₆H₅)}{(C₆H₅)CO}₂Cu] (3 (n = 2), 4 (n = 3)) with the loss of phenylselenato(alkyl)amine and acetic acid. In both these complexes, one arm of the ligand molecule undergoes hydrolysis, and links with Cu(II) in a bidentate (NO) fashion, as confirmed by single crystal X-ray crystallography of complex 3. The selenium atoms do not form part of the copper(II) distorted square planar coordination sphere which has a trans-CuN₂O₂ core. The average Cu–N and Cu–O distances are, respectively, 1.973(3) and 1.898(2) Å. The N–Cu–N and O–Cu–O angles are, respectively, 167.4(11)° and 164.5(12)°. The compounds 1–4 have been characterized by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, ¹H and ⁷⁷Se{¹H} NMR spectroscopy and cyclic voltammetry. The interaction of complex 3 with calf thymus DNA has been investigated by a spectrophotometric method and cyclic voltammetry.     

The exopolyhedral ligand orientation (ELO) in 3‐(nitrato‐κO)‐3,3‐bis(triphenylphosphane‐κP)‐3‐rhoda‐1,2‐dicarba‐closo‐dodecaborane(11) dichloromethane 2.2‐solvate

In the title compound, [Rh(C₂H₁₁B₉)(NO₃)(C₁₈H₁₅P)₂]·2.2CH₂Cl₂, studied as a 2.2‐solvate of what was assumed to be dichloromethane, the nitrate ligand lies cis with respect to both cage C atoms. Accordingly, the compound displays a pronounced preferred exopolyhedral ligand orientation (ELO) which is traced to both the greater trans influence of the cage B over the cage C atoms and the greater trans influence of the triphenylphosphane ligands over the nitrate ligand. The overall molecular architecture therefore agrees with that of a number of similar 3‐L‐3,3‐L′₂‐3,1,2‐closo‐MC₂B₉H₁₁ species in the literature.     

Complexes of di­methyl­tin dihalides with N‐methyl­pyrrolidinone,C12H24N2O2X2Sn (X = Cl,Br or I)

The single‐crystal X‐ray structure determinations of the title complexes, cis‐di­chloro‐trans‐di­methyl‐cis‐bis(N‐methyl­pyr­rolidin‐2‐one‐O)­tin(IV), [Sn(CH₃)₂Cl₂(C₅H₉NO)₂], cis‐di­bromo‐trans‐di­methyl‐cis‐bis(N‐methyl­pyrrolidin‐2‐one‐O)tin­(IV), [SnBr₂(CH₃)₂(C₅H₉NO)₂], and cis‐di­iodo‐trans‐di­methyl‐cis‐bis(N‐methyl­pyrrolidin‐2‐one‐O)­tin(IV), [Sn(CH₃)₂I₂(C₅H₉NO)₂], show that those tin complexes in which coordination of the lactam ligand to Sn^IV is realized via oxygen exhibit a distorted octahedral geometry.     

Vanadium(II) alkyls. Synthesis and X-ray crystal structures of trans-VMe2(dmpe)2 and cis-V(CH2SiMe3) 2(dmpe)2

Treatment of the vanadium(II) tetrahydroborate complex trans-V(η¹-BH₄)₂(dmpe)₂ with (trimethylsilyl) methyllithium gives the new vanadium(II) alkyl cis-V(CH₂SiMe₃)₂(dmpe)₂, where dmpe is the chelating diphosphine 1,2-bis(dimethylphosphino)ethane. Interestingly, this complex could not be prepared from the chloride starting material VCl₂(dmpe)₂. The CH₂SiMe₃ complex has a magnetic moment of 3.8 μ_B, and has been characterized by ¹H NMR and EPR spectroscopy. The cis geometry of the CH₂SiMe₃ complex is somewhat unexpected, but in fact the structure can be rationalized on steric grounds. The X-ray crystal structure of cis-V(CH₂SiMe₃)₂(dmpe)₂ is described along with that of the related vanadium(II) alkyl complex trans-VMe₂(dmpe)₂. Comparisons of the bond distances and angles for VMe₂(dmpe) ₂, V---C = 2.310(5) Å, V---P = 2.455(5) Å, and P---V---P = 83.5(2)° with those of V(CH₂SiMe₃)₂(dmpe)₂, V---C = 2.253(3) Å, V---P = 2.551(1) Å, and P ---V---P = 79.37(3)° show differences due to the differing trans influences of alkyl and phosphine ligands, and due to steric crowding in latter molecule. The V---P bond distances also suggest that metal-phosphorus π-back bonding is important in these early transition metal systems. Crystal data for VMe₂(dmpe)₂ at 25°C: space group P2₁/n, with a = 9.041(1) Å, b = 12.815(2) Å, c = 9.905(2) Å, β = 93.20(1)°, V = 1145.8(5) ų, Z = 2, R_F = 0.106, and R_wF =0.127 for 74 variables and 728 data for which I 2.58 σ(I); crystal data for V(CH₂SiMe₃)₂(dmpe)₂ at −75°C: space group C2/c, with a = 9.652(4) Å, b = 17.958(5) Å, c = 18.524(4) Å, β = 102.07(3)°, V= 3140(3) ų, Z = 4, R_F = 0.033, and R_wF = 0.032 for 231 variables and 1946 data for which I 2.58 σ(I).