Synthesis of rhodium(II) pyrazolate complexes: Crystal structure of tetra-μ-3,5-dimethylpyrazolato dirhodium(II) bis-acetonitrile, (Rh-Rh)

The reaction of Rh₂(O₂CMe)₄ with the sodium salt of 3,5-dimethylpyrazole (3,5-Me₂pzH) in acetonitrile gives Rh₂(3,5-Me₂pz)₄ · 2MeCN. This yellow diamagnetic compound on heating gives Rh(3,5-Me₂pz)₄ which in turn forms adducts with different unidentate ligands, L, to give Rh₂(3,5-Me₂pz)₄ · 2L. The binuclear tetra bridged structure has been established for the acetonitrile complex by X-ray diffraction. The Rh-Rh distance is 2.353(3) Å and the Rh-N (acetonitrile) distance is 2.202(5) Å. Some unsubstituted pyrazolates have been made.     

Studies in the flexibility of macrocyclic ligands. Crystal and molecular structure of 2,13-dimethy1-3,6,9,12,18-pentaazabicyclo (12.3.1) octadeca-(18),14,16-triene-dichloroion (III) hexafluorophosphate

The crystal structure of the title compound [FeL²Cl₂] [PF₆] is reported. Crystals are monoclinic with a = 11.747(9), b = 16.051(11), c = 11.964(10)Å, β = 98.1(1)°, Z = 4, Spacegroup P2₁/n. 1173 independent reflections above background have been refined to R 0.09. The coordination geometry around the Fe(III) ion is pentagonal bipyramidal with the two chlorine atoms in axial positions [Fe-Cl 2.348(7), 2.354(7)Å]. The five donor nitrogen atoms of the macrocycle form a pentagonal girdle with lengths in the range 2.20(2)–2.25(2)Å. The macrocycle conformation is compared to that found in [CuL²]²⁺ and [CoL²Cl]²⁺ where the 5N donor set provides respectively trigonal bipyramidal and square pyramidal environments and also to that found in the comparable 7-coordinate [FeL¹(NCS)₂]⁺ where L¹ is the related pentaene.     

Trimethylphosphine complexes of tungsten(O) and (IV). X-ray crystal structures of trimethylphosphine tris (phenylacetylene) tungsten(O); bis(trimethylphosphine) tetrakis (methylisocyanide) tungsten(O), and oxodichlorotris (trimethylphosphine) tungsten (IV)

The reduction of WCl₄(PMe₃)₃ by sodium amalgam in presence of phenylacetylene gives W(PMe₃)(PhCCH)₃ (A). Reduction in presence of methylisocyanide gives W(PMe₃)₂(MeNC)₄ (B), while in presence of excess PMe₃ in tetrahydrofuran under hydrogen, WH₂Cl₂(PMe₃)₄ (C) is formed. The reaction of WCl₂(PMe₃)₄ with methanol in tetrahydrofuran gives mixtures of WH₂Cl₂(PMe₃)₄ and WOC1₂(PMe₃)₃ (D).The structures of A, B, and D have been determined by X-ray diffraction.     

Stereospecific functionalisations of iron carbonyl complexes of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe2(CO)6

When the reaction between an excess of Fe₂(CO)₉ and the pentaene 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene(I) is carried out in hexane/methanol the endo,exo-bis(tetrahaptotricarbonyliron) isomer (C₁₂H₁₂)Fe₂(CO)₆(IIa)is the major product. The structure of this complex has been determined by X-ray diffraction.The asymmetric positions of the two Fe(CO)₃ groups with respect to the roof-shaped organic skeleton was used to induce either stereo-specific functionalisation of the uncoordianted endocyclic CC double bond or stereo-and regiospecific functionalisation of one of the two coordinated s-cis-butadiene groups of the pentaene. Thus, hydroboration/oxidation of Ila gave the endo-exo-bis(tetrahaptotricarbonyliron)isomer of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]octane-2-ol (IV). cis deuteration of the exocyclic double bond was achieved by treating IIa with D₂/PtO₂ in n-hexane.Protonation of IIa by HCl/AlCl₃/CH₂Cl₂ to give the η⁴-diene : η²-ene : η³-dienyl cationic complex Va, followed by quenching of Va with NaHCO₃/CH₃OH, resulted in a 1,4-addition of methanol to one coordinated s-cis-butadiene system. In contrast, quenching with NaOCH₃/CH₃OH resulted in the corresponding 1,2-addition of methanol. This gave the η⁴-1,3-diene : η⁴-1,4-diene complex VIIIa in which, suprisingly, one Fe(CO)₃ group is coordinated to two CC double bonds in gauche positions with respect to each other.     

Bis(dimethylphosphino)methane (dmpm) complexes of iron,molybdenum and chromium: X-ray crystal structures of FeCr(CO)6(μ-dmpm)2 and Fe2(CO)4(μ-CO)(μ-dmpm)2

The photolysis of Fe(η¹-dmpm)(dmpm)₂ [dmpm = bis(dimethylphosphino) methane) with Cr(CO)₆ and Fe(CO)₅ under UV irradiation produces FeCr(CO)₆(μ-dmpm)₂, Fe₂(CO)₆(μ-CO)(μ-dmpm) and Fe₂(CO)₄(μ-CO)(μ-dmpm)₂ respectively. The interaction of Mo(CO)₃(MeCN)₃ and (C₇H₈)Cr(CO)₃ with dmpm produces Mo₂(CO)₆(μ-dmpm)₃ and cis-Cr(CO)₂(dmpm)₂ respectively. The X-ray crystal structure of FeCr(CO)₆(μ-dmpm)₂ shows the molecule to contain a trigonal bipyramidal Fe(CO)₃P₂ unit plus a square pyramidal Cr(CO)₃P₂ unit held closely together by the methylene bridges of the dmpm ligands with steric compression between the CO groups causing distortions from ideal geometry in each case. The Cr … Fe distance is 3.111(6) Å and there seems to be little structural evidence of any form of interaction between the 16e Cr(O) centre and the Fe-containing unit. The structure of Fe₂(CO)₄(μ-CO)(μ-dmpm)₂ contains a symmetrical μ₂-carbonyl and a single bond between the two symmetry related (m) iron atoms. The Fe … Fe distance is 2.719(4) Å.     

Preparation and properties of dinitrogen trimethylphosphine complexes of molybdenum and tungsten—II: Synthesis and crystal structures of [MCl(N2)(PMe3)4] (M = Mo,W) and trans-[MoCl2(PMe3)4]

Sodium amalgam reduction of the complexes [MCl₃(PMe₃)₃] (M = Mo, W) in tetrahydrofuran, under dinitrogen, yields dark red-brown suspensions from which red-orange crystals of composition trans-[MCl(N₂)· (PMe₃)₄] can be collected. Spectroscopic and chemical evidence indicate the compounds are best formulated as mixtures of trans-[M(N₂)₂(PMe₃)₄] and trans-[MCl₂(PMe₃)₄] species, but attempts to isolate the pure bis(dinitro derivatives have proved unsuccessful. Single crystals of analytical composition [MCl(N₂)(PMe₃)₄] have been studied by X-ray crystallography, and the structure of trans-[MoCl₂(PMe₃)₄] has been determined for comparison. trans-[MCl(N₂)(PMe₃)₄] (M = Mo, W) and trans-[MoCl₂(PMe₃)₄] are all isostructural, crystallizing in the tetragonal space group I$\text{4}$2 trans-[MoCl(N₂)(PMe₃)₄] has a = 9.597(5), b = 12.294(6) Å, D_c = 1.36g cm^?3 Z = 2 and was refined to a final R value of 0.021 based on 319 independent observed reflections. The tungsten analogue has a = 9.573(4), b = 12.278(5) Å, D_c = 1.63g cm^?3 for Z = 2 and was refined to R = 0.19 with 322 independent observed reflections. trans-[MoCl₂(PMe₃)₄] has cell parameters a = 9.675(5), b = 12.311(6) Å D_c = 1.36 g cm^?3 for Z = 2 and was refined to R = 0.043 with 316 independent observed reflections. In each case the metal atom resides on a crystallographic $\text{4}$2m position. For trans-[MoCl(N₂)(PMe₃)₄] (M = Mo, W) the chlorine and dinitrogen ligands are disordered. M-N distances of 2.08(1) ? (M = Mo) and 2.04(2) ? (M = W) and M-Cl bond lengths of 2.415(8) Å (M = Mo) and 2.46(1) Å (M = W) are observed. In trans-[MoCl₂(PMe₃)₄], where there is no disorder, the Mo-Cl distance is 2.420(6) Å.     

Synthesis and x-ray crystal structure of OsBr2(CNBut)4·2CH2Cl2

Reaction of (NH₄)₂OsBr₆ with excess Na/Hg in THF in the presence of excess ^tBuNC yields trans-OsBr₂(CNBu^t)₄ in high yield. The bis-dichloromethane solvate crystallises from CH₂Cl₂ solutions and its X-ray crystal structure has been determined. Crystal data: C₂₂H₄₀Br₂Cl₄N₄Os, M = 852.40, monoclinic, space group P2₁/c, a = 9.702(3) Å, b = 10.143(5) Å, c = 18.497(5) Å, β = 104.28(3)°, U = 1764(1) ų, Z = 2 for D_c = 1.60 gcm^?3. λ(MoK_α) = 0.71069 Å (graphite monochromator), μ(MoK_α) = 65.44 cm^?1, final R = 0.044, R_w = 0.056 from 1105 observed reflections (1777 measured).     

Iron carbonyl complexes of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane. Crystal and molecular structure of (C10H10O)Fe(CO)3 and (C9H10CO)Fe2(CO)6

The reaction of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane (I) with iron carbonyls in various solvents yields the (η⁴-1,3-diene)Fe(CO)₃ isomers (II: exo; III: endo) and the bimetallic isomers bis[(η⁴-1,3-diene)Fe(CO)₃] (IV: bis(exo); V: endo,exo). In weakly coordinating solvents, a parallel rearrangement of I occurs through CO bond cleavage of the allylic ether by Fe₂(CO)₉ yielding an unsaturated ketone (VI) bonded to two Fe(CO)₃ groups through a trimethylenemethane and a 1,3-diene system, respectively. The geometries of III and VI have been ascertained by X-ray crystal structure determinations.     

Interaction of organic azides with methyl compounds of cobalt,rhodium, iridium,ruthenium and zirconium to give azido or 1,3-triazenido complexes. The crystal structures of tris-trimethylphosphineazido-dimethylcobalt(III) and bis(carbonyl)trimethylphosphineazidocobalt(I)

The interaction of azidotrimethylsilane with mer-CoMe₃(PMe₃)₃, fac-RhMe₃(PMe₃)₃, fac-IrMe₃(PMe₂Ph)₃, cis-RuMe₂(PMe₃)₄ and (η⁵-C₅H₅)₂ZrMe₂ gives tetramethylsilane and, respectively, the azido compounds MMe₂(N₃)(PMe₃)₃, M = Co, Rh, IrMe₂(N₃)(PMe₂Ph)₃, cis-Ru(N₃)₂(PMe₃)₄ and (η⁵-C₅H₅)₂ZrMe(N₃). The crystal structures of CoMe₂(N₃)(PMe₃)₃ and of the derived complex Co(N₃(CO)₂(PMe₃)₂ have been determined by X-ray diffraction.The dimethyl cobalt(III) compound has an octahedral structure with a mer arrangement of the three PMe₃ groups. The Co^III-N distance is rather long, at 2.071(4) Å. The cobalt(I) carbonyl compound has a trigonal bypyramidal structure with the two phosphines occupying the axial sites. The Co^I-N distance is 2.03(1) Å.The interaction of PhN₃ with (η⁵-C₅H₅)₂ZrR₂, R = Me, Ph, gives the 1,3-triazenido complexes (η⁵-C₅H₅)₂ZrR(RNNNPh) while mer-CoMe₃(PMe₃)₃ and p-MeC₆H₄N₃ react to give CoMe₂(MeNNNp-tol)(PMe₃)₂. In all three cases the triazenido group appears to be bidentate.     

Homogeneous palladium-catalysed arylation of activated alkenes with aryl chlorides

A study has been made of arylation of activated alkenes with aryl chlorides homogeneously catalysed by palladium acetate in the presence of triphenylphosphine or tri-p-tolylphosphine. Electron-withdrawing substituents in the aryl chloride favour the reaction. Only moderate yields could be obtained, and the maximum turnover number was 51, mainly because of precipitation of palladium metal. The probable mechanism of the reaction is discussed.     

Transition-metal complexes of two valence tautomers of a bulky phenoxide, 2,6-Bu-t2-4-MeC6H2O− (ArO−); preparation and crystal and molecular structure of a phenoxytitanium(III) and a cyclohexadienonylrhodium(I) complex, [Ti(η-C5H5)2 OAr] and [Rh(ArO-η5)(PPh3)2]

The 2,6-di-t-butyl-4-methylphenoxo ligand (ArO^?) is ambidentate, giving rise to the O-bonded 15-electron d¹ [Ti(η-C₅H₅)₂OAr] and the η⁵ -[C(2)-C(6)]-bonded 18-electron d⁸ complex [Rh(ArO-η⁵)(PPh₃)₂], obtained from [{Ti(η-C₅H₅)₂Cl}₂]-LiO Ar and [Rh{N(SiMe₃)₂}(PPh₃)₂]-ArOH, respectively; the average TiC(η) distance is 2.362(10) Å, TiO 1.892(2) Å, and O:C(of Ar) 1.352(3) Å, and TiOC 142.3(2)°; in the Rh^I complex, C(2)C(6) are coplanar (with CC(av.) 1.38(2) Å). C(1)O 1.28 Å, and Rh to C(2) C(6) bond lengthsare in the range 2.19–2.65 Å.     

Regioselective addition of protic acids to tricarbonyliron complexes of 2,3,5,6-tetrakis(methylene)-7-oxabicyclo[2.2.1]heptane. Crystal structure of (C10H10O)Fe2(CO)6

The main product of the thermal reaction between the title oxatetraene (I) and Fe₂(CO)₉ in ether/pentane is the bimetallic complex (C₁₀H₁₀O)Fe₂(CO)₆-diexo (II), which has C_2υ symmetry both in the solid state (X-ray analysis) and in solution. Whereas the protonation of the free ligand leads usually to polymerisation, the addition of a protic acid such as CF₃CO₂H to II proceeds cleanly at 0°C giving first a (η 3-allyl)Fe(CO)₃O₂CCF₃ complex (III). The intermediate III adds a second equivalent of acid in a slower step (k₂/k₁ = 0.1, CF₃CO₂D/CHCl₃, 0°C) giving the trans-bis(η³-allyl) isomer IV with high regioselectivity. The addition of CF₃CO₂D yields the corresponding deuteriomethylallyliron tricarbonyl trifluoroacetates III′ and IV′. No further deuterium incorporation is observed at 0°C, thus confirming the kinetic control of the regioselective double addition of protic acid to II.     

Organo-imido alkoxides of tungsten(VI). The crystal and molecular structures of [W(NPh)(μ-OMe)(OMe)3]2 and [W(NPh)(OCMe3)3Cl(NH2CMe3)]

Reaction of phenylimido tungsten tetrachloride with MeOH and t-butylamine gave the dimeric complexes [W(NPh)(μ-OMe)(OMe)₃]₂ and [W(NPh)(μ-OMe)(OMe)₂Cl]₂. With ethanol [W(NPh)(μ-OEt)(OEt)₂Cl]₂ was formed whereas isopropyl and neopentyl alcohols gave the monomeric complexes [W(NPh)(OR)₄(NH₂CMe₃)](R = CHMe₂, CH₂CMe₃); t-butanol gave [W(NPh)(OCMe₃)3Cl(NH₂CMe₃)] which could not be converted to [W(NPh) (OCMe₃)₄]. Further reaction of [W(NPh)(μ-OMe)(OMe)₃]₂ with o-HOC₆H₄CH = NC₆H₃Me₂(salim-H) gave the salicylaldimine complex [W(NPh)(OMC)₃(salim)]. The products were characterised by analytical data, IR, ¹H NMR, ¹³C NMR and mass spectroscopy. The crystal and molecular structures of the title complexes have been determined from single crystal X-ray diffractometer data. Crystals of [W(NPh)(μ-OMe)(OMe)₃]₂are triclinic with a = 8.473(7), b = 10.776(5), c = 7.683(Å, α = 102.26(3), β = 102.68(4), γ = 71.13(6)°, space group P$\text{1}$ Crystals of 3) [W(NPh)(OCMe₃)₃Cl(NH₂CMe₃) are monoclinic with a = 9.341(2), b = 29.608(7), c = 10.257(2) Å, β = 106.28(2)°, space group, P2₁/c. Both structures were solved by Patterson and Fourier methods and refined to R = 0.075 for the 1022 observed data of [W(NPh) (μ-OMe)(OMe)₃]₂ and to R = 0.074. For the 2033 observed data of [W(NPh)(OCMe₃)₃Cl(NH₂CMe₃). The former molecule is shown to be a dimer, the two halves of the molecule being related by a centre of symmetry. Both W atoms adopt a distorted octahedral coordination geometry and they are linked by two methoxy bridges. Trans to one of the bridging donors is the phenyl imido group with a WN bond length of 1.61(4) Å; the remaining coordination sites are filled with methoxy groups. The structure of W(NPh)(OCMe₃)₃ Cl(NH₂CMe₃) is monomeric with the phenylimido group trans to the NH₂CMe₃ ligand in a distorted octahedral coordination geometry. Remaining sites are filled with the chloride and 3 OCMe₃ ligands. The WN (imido) bond length is 1.71(2) Å, whilst WN(amine) is 2.40(2) Å     

Alkyl,hydrido and related compounds of ruthenium with trimethylphosphine and bis(1,2-dimethylphosphino)ethane. X-ray crystal structures of cis-hydridoethyltetrakis(trimethylphosphine)-ruthenium(II) and ethylene tetrakis-(trimethylphosphine)ruthenium(0)

The interaction of trans-RuCl₂(PMe₃)₄ with R₂Mg, depending on the reaction conditions and the alkyl groups gives either (C₂H₄)Ru(PMe₃)₄ or cis-Ru(H)(C₂H₅)(PMe₃)₄ for R = ethyl, and cis-Ru(H)(ⁿC₃H₇(PMe₃)₄ for R = n-propyl. The interaction of Et₂Mg with trans-RuX₂(dmpe)₂ (X = Cl, CO₂Me) gives either cis-Ru(Et₂)dmpe)₂ for X = Cl or trans-Ru(Et)₂(dmpe)₂ for X = CO₂Me. NMR data for (C₂H₄)Ru(PMe₃)₄ suggest that ethylene is bound in the η² or metallocyclopropane form, which is confirmed by a single-crystal X-ray diffraction study. This shows a relatively long carbon-carbon bond distance of 1.44(1)Å between the “ethylene” carbons. The structure of cis-Ru(H)(C₂H₅)(PMe₃)₄ has also been confirmed by a single-crystal X-ray diffraction study. Possible mechanisms for the observed reactivities are considered.     

An examination of the relationship between the x-ray diffraction-derived molecular structure of chloro (1,11-diamino-3,6,9-trithiaundecane)cobalt(III) cation and its inner sphere reduction by iron(II)

The crystal structure of racemic [Co(NSSSN)Cl](ClO₄)Cl was determined by X-ray diffraction methods. It crystallizes in the monoclinic system, space group P2₁/c, with cell constants of a = 9.795(3), b = 10.412(3) and c = 16.323(8) Å, and β = 93.87(4)°; V = 1661 ųd (meas.; flotation) = 1.85 gm-cm^?3, d (calc.; Z = 4 molecules/unit cell) = 1.88 gm-cm^?3. The molecules, a racemic mixture, have the absolute configurations λλδλ or δδλδ at each of the four five-membered rings and resemble, in general, the so called αα conformer already described by Snow¹ in his study of the Co(tetraen)Cl²⁺ cation. However, the torsional angles at C2, C3 and C8, C9 in the two terminal C-C-NH₂ fragments are quite different in the two systems. For Co(tetraen)Cl²⁺ they are 44.7° and ?20.2° respectively, whereas for Co(NSSSN)C²⁺ the values –52.3° and –44.6° obtain. Also, the ring Co-S1-C3-C2-N1 does not have the classical, low energy conformation found in Co(tetraen)Cl²⁺. The presence of the larger Co-S bonds causes the two terminal -NH₂ groups to be pushed toward each other, and to minimize steric hindrance between adjacent -NH₂ hydrogens and ligand twists C2 down and staggers the terminal hydrogens. We visualize the propagation of these distortion effects in solution as being transferred from one side to the other across the entire ligand chain with concomittant effects on the activation of the precursor complex in electron transfer reactions, resulting in ~10⁷ rate enhancement over the Co(tetraen)Cl² system. Kinetic data for the reduction of Co(NSSSN)X²⁺ and Co(NSNSN)X²⁺ (X = Cl^?, Br^?) by Fe(II) is also presented and discussed.     

Allyldifluorophosphite-metal chemistry: Ru complexes of F2POC3H5 and the crystal structure of (Ph3P)2(F2POC3H5)Ru(CO)(Cl)H

With several chloro ruthenium phosphine complexes, allyldifluorophosphite, F₂POC₃H₅, displaces triphenylphosphine to form new compounds in which it acts as a phosphorus donor ligand. The new complexes [PPh₃]₂[F₂POC₃H₅]Ru[CO][Cl][H], I, and [(PPh₃)₂(F₂POC₃H₅)₂RuCl₂]_nII, hav characterized by chemical, spectroscopic, and, in the case of I, crystallographic means. This behaviour of F₂POC₃H₅ contrasts to its reactions with several platinum and palladium chloro complexes where it undergoes Arbuzov-type rearrangements.     

Homogeneous catalysis: VI. Hydrosilylation using tris(pentanedionato)rhodium(III) or tetrakis(μ-acetato)dirhodium(II) as catalyst

The catalytic activity of tris(pentanedionato)rhodium(III), (or rhodium(III) acetylacetonate) (I) has been investigated for the hydrosilylation of a variety of organic substrates: alkenes, terminal or internal acetylenes, conjugated dienes, or α,β-unsaturated carbonyls or nitriles. With PhCHCH₂ or PhCH₂CHCH₂, ω-substitution was unexpectedly observed, as well as addition. Compound I is an active hydrosilylation catalyst in the absence of any added reducing agent, as is tetrakis(μ-acetato)dirhodium(II) (II) which does not, however, show any unusual catalytic activity due to the two metal atom cluster. Possible mechanisms are suggested.     

Tris(difluoro and trifluorobutane-2,4-dionato) gallium(III) and indium(III) complexes

Eight tris(β-diketonate)gallium(III) and seven tris(β-diketonate)-indium(III) complexes M(RCOCH-COR′)₃, with R′being difluoromethyl and trifluoromethyl substituents and R′ being methyl, phenyl, aryl, 2′-naphthyl and 2′-thienyl substituents have been studied by nuclear magnetic resonance spectroscopy. The complexes are all nonrigid (fluxional) and their ¹⁹F NMR spectra show four resonances in the nonexchanging regions due to cis and trans isomers. A variable low temperature study of these complexes was done for the gallium chelates and activation parameters are calculated. The indium complexes all have nonexchanging regions below ?100°C. The ¹³C NMR data on the complexes are also reported.     

Complexes of lanthanide nitrates with 4n-(2′-hydroxy benzylidene)-aminoantipyrine

New complexes of lanthanide nitrates with 4N-(2′-hydroxy benzylidene)-aminoantipyrine (HBAAP) having the general formula [Ln(HBAAP)₂(NO₃)₃] (where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y) have been prepared and characterized. Conductance studies indicate non-electrolytic behaviour for these complexes. Their infrared spectra show that both the ligand and the nitrate group are bound to the metal ion in a bidentate fashion. Electronic spectra indicate weak covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to ～200°C and undergo complete decomposition in the range 200–550° resulting in the formation of the stable lanthanide oxides.     

Further studies on organonickel compounds: the synthesis of some new alkyl-, acyl- and cyclopentadienyl-derivatives and the crystal structure of trans-[Ni(CH2SiMe3)2(PMe3)2]

The complex [NiCl₂(PMe₃)₂] reacts with one equivalent of mg(CH₂CMe₃)Cl to yield the monoalkyl derivative trans-[Ni(CH₂CMe₃)Cl(PMe₃)₂], which can be carbonylated at room temperature and pressure to afford the acyl [Ni(COCH₂CMe₃)Cl(PMe₃)₂]. Other related alkyl and acyl complexes of composition [Ni(R)(NCS)(PMe₃)₂] (R = CH₂CMe₃, COCH₂CMe₃) and [Ni(R)(η-C₅H₅)L] (L = PMe₃, R = CH₂CMe₃, COCH₂CMe₃; L = PPh₃, R = CH₂CMe₂Ph) have been similarly prepared. Dialkyl derivatives [NiR₂(dmpe)] (R = CH₂SiMe₃, CH₂CMe₂Ph; dmpe = 1,2-bis(dimethylphosphine)ethane, Me₂PCH₂ CH₂PMe₂) have been obtained by phosphine replacement of the labile pyridine and NNN′N′-tetramethylethylenediamine ligands in the corresponding [Ni(CH₂SiMe₃)₂(py)₂] and [Ni(CH₂CMe₂Ph)₂(tmen)] complexes. A single-crystal X-ray determination carried out on the previously reported trimethylphosphine derivative [Ni(CH₂SiMe₃)₂(PMe₃)₂] shows the complex belongs to the orthorhombic space group Pbcn, with a = 14.345(4), b = 12.656(3), c = 12.815(3) Å, Z = 4 and R 0.077 for 535 independent observed reflections. The phosphine ligands occupy mutually trans positions P-Ni-P 146.9(3)° in a distorted square-planar arrangement.