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.     

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.     

Organonitrile complexes of iron(II) and Ruthenium(II): X-ray crystal structure of trans-[Fe(NCMe)2(dmpe)2](BPh4)2

The interaction of FeCl₂(dmpe)₂ [dmpe = 1,2-bis(dimethylphosphino)ethane] with RCN (R = Me or Et) gives the partially substituted complex trans-[FeCl(NCR)(dmpe)₂]Cl at room temperature, but in refluxing RCN in the presence of NaBPh₄ the product is trans-[Fe(NCR)₂(dmpe)₂](BPh₄)₂. The X-ray crystal structure of the acetonitrile complex has been determined. No reaction is observed between RuCl₂(dmpe)₂ and MeCN, although the disubstituted complex can be made in a similar way to the iron analogue. The interaction of trans-[M(NCMe)₂(dmpe)₂][BPh₄)₂ (M = Fe or Ru) with H₂ leads to the amine complexes trans-[M(H₂NEt)₂(dmpe)₂](BPh₄)₂. Although the ethylamine can be removed on refluxing in MeCN the complexes do not act as catalysts. Addition of MeCN to FeCl₂(PMe₃)₂ yields only the complex [FeCl(NCMe)(PMe₃)₂]Cl; RuCl₂(PMe₃)₄ reacts in refluxing MeCN in the presence of NaBPh₄ to give trans-[Ru(NCMe)₂(PMe₃)₄](BPh₄)₂.     

Preparation and characterization of some mixed ligand complexes of platinum(II)

The mixed ligand complexes PtX₂(ER₃)L and PtXY(ER₃)L (where ER₃ = PR₃ or AsMe₃; L = phosphine, arsine; X = Cl; Y = Cl, H or Me) have been prepared and characterized. Reaction of PtMe₂(ER₃)L with HCl yields PtMeCl(ER₃)L, in exclusively one of three possible isomeric forms. Excess tetramethyltin reacts with Pt₂Cl₂(μ-Cl)₂(PMe₂Ph)₂ giving both cis and trans Pt₂(μ-Cl)₂(PMe₂Ph)₂, as identified from the NMR spectra. Cleavage of Pt₂(μ-Cl)₂Me₂(PMe₂Ph)₂ with donor ligands such as AsPh₃, PMe₂ or pyridine, was useful as a synthetic route to the unsymmetrical methylchloro Pt^II derivatives. The reaction of cis-[PtMe₂(PPh₃)(AsPh₃)] with excess dimethylacetylenedicarboxylate (DMA) yielded only one product, which was of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PPh₃)(AsPh₃)], with the alkenyl groups having the same geometry about the CC bond. The use of diethylacetylene-dicarboxylate (DEA) rather than DMA gave a similar product. However, when cis-[PtMe₂(PEt₃)(AsPh₃)] was allowed to react with DMA, two products of the formula trans-[Pt{C(COOCH₃)C(COOCH₃)CH₃}₂(PEt₃)(AsPh₃)] were obtained, with the stereochemistry of both alkenyl groups being either cis or trans.     

Reactions of cis-[dicarbonylbis(1,2-bis(dimethylphosphino)ethane)metal] compounds of chromium and molybdenum with organic electron acceptors; Tetracyanoethene, 1,2,4,5-tetracyanobenzene and 1,3,5-trinitrobenzene

Reaction between cis-[Mo(CO)₂(dmpe)₂] (dmpe =Me₂PCH₂CH₂PMe₂) and organic π-acids tetracyanoethene (TCNE), 1,2,4,5-tetracyanobenzene (TCNB) and 1,3,5-trinitrobenzene (TNB) proceeds via electron transfer from the metal complex, which is oxidised to the 17-electron trans-[Mo(CO)₂(dmpe)₂]⁺ ion, to the organic acceptor which is reduced to the radical anion. The final products of the reactions are characterised ascis-[Mo{C₂(CN)₃} (CO)₂(dmpe)₂] [CN], cis-[Mo{C₆H₂(CN)₄} (CO)₂(dmpe)₂] [C₆H₂(CN)₄]₈ and [Mo(CO)₂(dmpe)₂ · 2 C₆H₃(NO₂)₃] by analysis and spectroscopic (IR, NMR, ESR) measurements which are compared with those of cis-[MoX(CO)₂(dmpe)₂]X (X = Cl, Br, I) and fac, fac-[Mo₂Cl₄(CO)₄(dmpe)₃]. The reaction of cis-[Cr(CO)₂(dmpe)₂] with TCNE gives trans-[Cr(CO)₂(dmpe)₂]⁺ [TCNE]^? only.     

The interaction of vinyl acetate and allyl acetate with chloro-bridged platinum(II) complexes [Pt2Cl4(PR3)2]: Crystal structure of cis-[PtCl2(PMe2Ph2)(CH2=CHOCOCH3)]

Five complexes of type cis-[PtCl₂(PR₃)Q] (PR₃ =PMe₃, PMe₂Ph, PEt₃; Q = CH₂ CHOCOCH₃ or CH₂=CHCH₂OCOCH₃) have been prepared. The crystal structure of cis-[PtCl₂[PME₂Ph)(CH₂=CHOCOCH₃)] is described. Crystals of cis-[PtCl₂(PME₂Ph)(CH₂-CHOCOCH₃)] are triclinic, with a 8.441(4), b 13.660(5), c 7.697(3) Å, a 101.61(3)°, β 111.85(3)° γ 95.22(3)°, pP1, Z = 2. The structure was determined from 2011 reflections I σ 3σ (I) and refined to R = 0.037. The CH₃COO grouping is syn to the cis-PMe₂Ph ligand, with bond lengths of PtCl (trans to P) 2.367(3), PtCl (trans to olefin) 2.314(3), PtP 2.264(2), and PtC of 2.147(12) and 2.168(11) Å. The complexes cis-[PtCl₂- (PR₃)Q] were studied by variable temperature ¹H and ³¹P NMR spectroscopy. Spectra of the vinyl acetate complexes were temperature dependent as a result of rotation about the platinum—olefin bond. The rotation was “frozen out” at ca. 240 K; for cis-[PtCl₂(PME₂Ph)(CH₂=CHOCOCH₃] ΔG≠ (rotation) 15.0 ± 0.2 kcal mol^-1. NMR parameters for the rotamers are reported. NMR studies of the interaction between chloro-bridged complexes of type [Pt₂Cl₂(PR₃)₂] (PR₃ = P-N-Pr₃ or PMe₂Ph) and vinyl acetate shows that even at low temperatures (213 K) equilibrium favours the bridged complex and the proportion of trans-[PtCl₂(PR₃)CH₂=CHOCOCH₃)] is very small e.g. 2%. The allyl acetate complexes cis-[PtCl₂(PR₃)(CH₂₌CHCH₂OCOCH₃)] showed only one rotamer over the range 333–213 K. Reversible dissociation of cis-[PtCl₂(PMe₂Ph)- (CH₂=CHCH₂OCOCH₃)] to [Pt₂Cl₄(PMe₂Ph)₂] + allyl acetate was studied at ambient temperature. At low temperatures e.g. 213–190 K addition of allyl acetate to a CDCl₃ solution of [Pt₂Cl₂(P-n-Pr₃)₂] reversibly gave some olefin complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)] and some O-bonded complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)].     

Oxo-molybdenum(IV) and tungsten(IV) complexes with phosphine and isocyanide ligands

The complexes [MOCl₂(dmpe)(PMe₃)] and [MOCl₂(dmpe)₂]Cl (M = Mo, W; dmpe = Me₂PCH₂CH₂PMe₂) have been prepared by reaction of the oxo compounds [MOCl₂(PMe₃)₃] with equivalent amounts of the dmpe ligand under appropriate conditions. The dark blue tungsten species [WOCl₂(dmpe)(PMe₃)] forms only slowly but reacts readily with more dmpe to afford [WOCl(dmpe)₂]Cl. This prevents isolation of the former in a pure form. The related isocyanide derivatives [MOCl₂(CNR)(PMe₃)₂], (M = Mo; R = CMe₃ and C₆H₁₁; M = W, R = CMe₃) have been obtained similarly by reaction of the [MOCl₂(PMe₃)₃] complexes with the stoichiometric amount of the isocyanide ligand, but attempts to prepare the carbonyl analogues, [MOCl₂(CO)(PMe₃)₂], have proved unsuccessful. The new compounds have been characterized by analytical and spectroscopic methods (IR, ¹H, ¹³C and ¹³P NMR spectroscopy).     

Basische metalle: LIII. Ruthenium- und osmium-komplexe mit dem dimethylphosphinomethanid-anion als liganden

The reduction of trans-RuCl₂(PMe₃)₄ with Na/Hg and of trans-OsCl₂(PMe₃)₄ with sodium in the presence of catalytic amounts of naphthalene gives the complexes RuH(η²-CH₂PMe₂)(PMe₃)₃ (III) and OsH(η²-CH₂PMe₂PMe₂), (IV) in good yields. An equilibrium with the metal(0) isomers [M(PMe₃)₄] cannot be detected by NMR spectroscopy. III and IV react with dihalomethanes CH₂X₂ (X = Cl, Br, I) and CH₃I to form mixtures of the dimethylphosphinomethanide complexes MX(η²-CH₂PMe₂)(PMe₃)₃ and the compounds MX₂(PMe₃)₄. The reactions of III and IV with the Brönsted acids HCl, HBr, CF₃CO₂H and HC₂Ph lead (with exception of M = Ru and X = C₂Ph) to the complexes cis-MX₂(PMe₃)₄. The hydrolysis of IV gives the hydrido(hydroxy) compound cis-OsH(OH)(PMe₃)₄, which has been characterized by ¹H, ³¹P NMR and mass spectroscopy. The synthesis of the complex cis-Os(CH₃)₂(PMe₃)₄ is also described; the conversion into the ethylene(hydrido)metal cation [OsH(C₂H₄)(PMe₃)₄]⁺ failed.     

Synthesis and reactions of trans-dicarbonyl bis-[1,2-bis(dimethylphosphino)ethane] vanadium(O): X-ray crystal structures of trans-V(CO)2(dmpe)2 [cis-V(CO)2(dmpe)2(CH3CN)]BPh4 and cis-V(CO)2(dmpe)2(O2CEt)

Interaction of trans-VCl₂(dmpe)₂ with sodium amalgam in tetrahydrofuran under CO gives trans-V(CO)₂(dmpe)₂. The latter is oxidized by Ag⁺ in acetonitrile to give [cis-V(CO)₂(dmpe)₂(CH₃CN)]⁺, isolated as the tetraphenylborate. Interactions with acids (HX) gives neutral complexes of the type V(CO)₂(dmpe)₂X (X = Cl, MeCO₂, EtCO₂, CF₃CO₂, PhPO₂H or NH₂SO₃); the chloride can be exchanged with N₃⁻ or CN⁻ in methanol. X-ray structural studies confirm the trans stereochemistry for V(CO)₂(dmpe)₂ and the seven-coordination of V^I in both [V(CO)₂(dmpe)₂(CH₃CN)][BPh₄] and V(CO)₂(dmpe)₂(O₂CEt), which have a pseudo octahedral geometry with the two carbonyls occupying a “split” axial site. ⁵¹V NMR and other spectra are reported.     

Preparation and properties of dinitrogen complexes of molybdenum and tungsten with trimethylphosphine as coligand : III. Synthesis and properties of cis-[W(N2)2(PMe3)4], trans-[W(C2H4)2(PMe3)4] and [M(N2)(PMe3)5] (M = Mo,W). The crystal and molecular structure of [Mo(N2)(PMe3)5]

The reduction of [WCl₄(PMe₃)₃] with dispersed sodium, under dinitrogen, gives cis-[W(N₂)₂(PMe₃)₄], while under ethylene trans-[W(C₂H₄)₂(PMe₃)₄] is obtained. The ethylene complex can also be prepared by displacement of the dinitrogen molecules in cis-[W(N₂)₂(PMe₃)₄] by ethylene at room temperature and pressure. Interaction of cis-[M(N₂)₂(PMe₃)₄] complexes (M = Mo, W), with PMe₃, under helium or argon, yields [M(N₂)(PMe₃)₅]. The molybdenum complex crystallizes in the orthorhombic space group Pnma, with a 22.063(6), b 12.106(4), c 9.745(4) Å. The Mo—P distance trans to the dinitrogen ligand (2.483(7) Å) is slightly longer than the average of the other four Mo—P bonds (2.460(5) Å).     

Reactivity of cyclopalladated compounds: VIII. Synthesis of cyclometallated compounds with an oxygen as the donor atom. Crystal and molecular structure of (8-methylquinoline-C,N)-(1-methoxynaphthalene-8-C,O)palladium(II)

Treatment of 1-methoxynaphthalene (MXNH) with n-butyllithium in a diethyl ether/n-hexane solution gives 1-methoxynaphthalene-8-lithium (MXNLi) in 30% yield as an insoluble material. This compound reacts with PdCl₂(SEt₂)₂ to give bis(1-methoxynaphthalene-8-C,O)palladium(II) (I)_and with PtCl₂(SEt₂)₂ to give cis- and trans-(1-methoxynaphthalene-8-C,O)(1-methoxynaphthalene-8-C)(diethylsulfide)platinum(II) (II), which are non-rigid molecules in solution. With the cyclopalladated dimers [{$\text{Pd(CN}$)Cl₂}₂], MXNLi gives the palladobicyclic compounds: ($\text{N∩C)P}$$\text{d(C∩O}$) (III). An X-ray diffraction study of compound IIIa where N∩N = 8-methylquinoline-C,N reveals the planarity of the molecule, shows that it has a cis configuration with respect to the PdC bonds, and confirms that the oxygen atom of MXN is bonded to palladium: PdO 2.236(4) Å. The geometry of IIIa is maintained in solution, whereas the corresponding compounds IIIb and IIIc in which N∩C is benzo[h]quinoline-9-C,N and N,N-dimethyl-1-naphthylamine-8-C,N, respectively, appear to be mixtures of cis and trans isomers in solution. With PMe₂Ph I and II give trans-Pd(MXN)₂(PMe₂Ph)₂ and cis-Pt(MNX)₂(PMe₂Ph)₂, respectively, in which the methoxynaphthalene is bound to the metals via the 8-carbon of the naphthalene ring. Only one phosphine ligand adds to compounds IIIb and IIIc with displacement of the O → Pd bond. One carbon monoxide ligand can be added to the platinum compound II to give Pt(MXN)₂(SEt₂)CO which in solution exists as two isomers in equilibrium.     

Preparation of Ru(CO)3(PMe3)MeI and its acetyl derivatives

[Ru(CO)₄PMe₃] reacts with MeI to give fac-[Ru(CO)₃(PMe₃)(Me)I]. The latter reacts with PMe₃ to give a mixture of the three isomers of cis-bis(trimethylphosphine)-cis-dicarbonyl acetyl iodide [Ru(CO)₂(PMe₃)₂(COMe)I]. Decarbonylation of the mixture gives only the trans-bis(trimethylphosphine)-cis-dicarbonyl methyl iodide complex [Ru(CO)₂(PMe₃)₂MeI], which was also prepared by oxidative addition of MeI to [Ru(CO)₃(PMe₃)₂].     

Studien zur CH-aktivierung: II. Der einfluss der liganden auf die bildung von aryl(hydrido)ruthenium(II)- und -osmium(II)-komplexen aus aromaten

The complexes trans-MCl₂(PMe₃)₄ (M = Ru, Os) react with CO and P(OMe)₃ to give the mono- and disubstituted derivatives trans,mer-MCl₂(PMe₃)₃L (L = CO, P(OMe)₃) and all-trans-MCl₂(PMe₃)₂[P(OMe)₃]₂, respectively. On reaction of trans-RuCl₂[P(OMe)₃]₄ with CO and PMe₃, the compounds trans,mer-RuCl₂[P(OMe)₃]₃(CO) and trans,cis,cis-RuCl₂(PMe₃)₂[P(OMe)₃]₂ are synthesized. The reduction of MCl₂(PMe₃)₂[P(OMe)₃]₂ with Na/Hg in benzene or toluene via {M(PMe₃)₂[P(OMe)₃]₂} as an intermediate leads to subsequent intermolecular addition of the arene and to the aryl(hydrido)metal complexes cis,trans,cis-MH(C₆H₅)(PMe₃)₂[P(OMe)₃]₂ (M = Ru, Os) and MH(C₆H₄CH₃)(PMe₃)₂[P(OMe)₃)₂ (M = Os). For M = Ru, in the presence of P(OMe)₃, the ruthenium(0) compound Ru(PMe₃)₂(P(OMe)₃]₃ is formed. The hydrido(phenyl) complexes react with equimolar amounts of Br₂ or I₂ by elimination of benzene to produce the dihalogenometal compounds cis,trans,cis-MX₂(PMe₃)₂[P(OMe)₃]₂. The reaction of trans-RuCl₂(PMe₃)₄ with Na/Hg in the presence of PPh₃ leads to the ortho-metallated complex fac-RuH(η²-C₆H₄PPh₂)(PMe₃)₃, which reacts with CH₃I, CS₂, COS and HCl to give the compounds mer-RuI(η²-C₆H₄PPh₂)(PMe₃)₃, fac-Ru(SCHS)(η²-C₆H₄PPh₂)(PMe₃)₃, fac-Ru(S₂CO)(CO)(PMe₃)₃ and RuCl₂(PMe₃)₃, respectively. The paramagnetic 17-electron complexes [MCl₂(PMe₃)_nL_4-n]PF₆ are obtained on oxidation of MCl₂(PMe₃)_nL_4-n with AgPF₆. Their UV spectra exhibit a characteristic CT band. [RuCl₂(PMe₃)₄]PF₆ and [OsCl₂(PMe₃)₄]PF₆ react with CO and P(OMe)₃ by reduction to form the corresponding ruthenium(II) and osmium(II) compounds MCl₂(PMe₃)_nL_4-n.     

A cyclometallated iridium(III) dimethylphenylphosphine complex

[Ir(cod)Cl]₂ (cod = 1,5-cyclooctadiene) reacts with PMe₂Ph in CH₃CN to give the red cation [Ir(PMe₂Ph)₄]⁺. This complex in CH₃CN reacts with H₂ to give cis-[IrH₂(PMe₂Ph)₄]⁺, but on reflux for 6 h in the absence of H₂, it gives the first example of a cyclometallated PMe₂Ph complex fac-[IrH(PMe₂C₆H₄)(PMe₂Ph)₃]⁺, as shown by PMR spectroscopy and preliminary X-ray crystallographic data.     

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).     

The preparation and molecular structure oftrans-[MoCl2(PMe2Ph)4]

Summary The compoundtrans-[MoCl₂(PMe₂Ph)₄] has been prepared by the reduction of MoCl₅ (by Mg) or of [MoCl₃(PMe₂Ph)₃] (by LiBuⁿ) in the presence of PMe₂Ph in tetrahydrofuran (THF). It has _eff=2.84 B.M. and crystallises in space group P1 witha=11.591(3),b=12.931(3),c=12.703(3) Å, = 95.28(2), =105.97(2), =103.54(2)°. Refinement of the structure gave R=0.036. The Mo-Cl and Mo-P distances average 2.443(6) and 2.534(8) Å, respectively.Low-valent phosphine complexes of the Group VI metals continue to attract much attention because of their involvement in studies of the catalytic activation of dinitrogen⁽¹⁾, dihydrogen(^{2, 3}), alkenes and alkynes(⁴). As a by-product during our studies of dinitrogen(¹) and hydride(²) complexes of molybdenum and tungsten, we obtainedtrans-[MoCl_2- (PMe₂Ph)₄] as yellow, paramagnetic crystals (_eff= 2.84 B.M.). We first obtained the compound during the attempted synthesis ofcis-[Mo(N₂)₂(PMe₂Ph)₄] by reduction of MoCl₅ with Mg in the presence of PMe₂Ph (see Experimental). Upon identification of the compound we found that it could be readily synthesised by treatment of [MoCl₃(PMe₂Ph)₃]⁽⁵⁾ with LiBuⁿ in THF in the presence of PMe₂Ph (experimental).The complex was shown to have thetrans structure by x-ray analysis (Figure). Analogues oftrans-[MoCl₂(PMe₂Ph)₄] have been prepared, namely [CrCl₂(Me₂PCH₂CH₂PMe₂)₂]⁽⁶⁾,trans- [MoCl₂(PMe₃)₄]⁽⁷⁾, [WCl₂(PMe₂Ph)₄]⁽⁸⁾ and [WCl₂(PMe₃)₄]⁽⁴⁾, of which onlytrans-[MoCl₂(PMe₃)₄] has been examined by X-rays⁽⁷⁾. Its principal structural parametersi.e. d(Mo-Cl)= 2.420(6), d(Mo-P)_av=2.496(3) Å⁽⁶⁾ are close to those found here fortrans-[MoCl₂(PMe₂Ph)₄].     

Phosphine carbonyl-technetium(I) and -technetium(III) complexes

Treatment of trans-[TcX₄L₂] (X Cl, Br and L PPH₃, PMe₂Ph) with carbon monoxide (1 atm) in boiling ethyleneglycol methyl ether, gives trans-[TcX-(CO)₃L₂]. Under these conditions the mer-[TcX₃(PMe₂Ph)₃] (X Cl, Br) gives a mixture of the trans-[TcX(CO)₃(PMe₂Ph)₂] and cis-[TcX(CO)₂(PMe₂Ph)₃] complexes, but when added free dimethylphenylphosphine is present only the second product is obtained. Carbon monoxide reacts with mer-[TcCl₃(PMe₂Ph)₃] in refluxing ethanol to give [TcCl₃(CO)(PMe₂Ph)₃] a C_{3 v} seven-coordinate technetium(III) complex.The stereochemistry of the complexes was determined from their IR and¹H NMR spectra.     

Studies of chelation : II. Phosphine complexes of molybdenum and manganese

Activation parameters have been obtained for the chelation of Mo(CO)₅dpe (dpe = Ph₂PCH₂CH₂PPh₂) and of Mo(CO)₅dmpe (dmpe = Me₂PCH₂CH₂PMe₂) to give cis-Mo(CO)₄dpe and cis-Mo(CO)₄dmpe respectively. The results are compared with those for the analogous chromium complexes and show that the enthalpy contribution determines the more rapid chelation in the molybdenum complexes. The preparation and properties of the chelate-bridged hetero-metallic complex (CO)₅ModmpeMn(CO)₄Br are reported. The reaction between Et₄N[Mn(CO)₄X₂] (X = Cl, Br) and bidentate ligands dpe, dmpe and ape (ape = Ph₂PCH₂CH₂AsPh₂) in the presence of either silver(I) tetrafluoroborate or Et₃OBF₄ produces cis-Mn(CO)₄X(bidentate) which is identified by infrared and mass spectrometry. At room temperature the Mn(CO)₄X(bidentate) complex is rapidly converted to the chelated fac-Mn(CO)₃X(bidentate) complex. The chelation process is approximately 10⁴ times more rapid than in the isoelectronic chromium(O) complexes. The preparation and characterisation of fac-Mn(CO)₃Br(dmpe), cis-Mn(CO)₄Br(PMe₃) and fac-Mn(CO)₃Br(PMe₃)₂ are reported.     

Hydrocarbon chemistry : by G.A. Olah (C. Eaborn). J. Organomet. Chem., 334 (1987) C49-C50.

Sequential displacement of both N₂ ligands from cis-[Mo(N₂)₂(PMe₂Ph)₄] by CNMe occurs by a dissociative (I_d) mechanism (k₂/k₁～5,k₁ 0.020 min^?1 at 273 K) via the intermediate cis-[Mo(N₂)(CNMe)(PMe)₂Ph)₄] For t-BuNC substitution, the only detected intermediate appears to be [Mo(CNBu-t)(PMe₂Ph)₄] and no intermediate was detected in reactions of trans-[Mo(N₂)₂(Ph₂PCH₂CH₂PPh₂)₂] with CNMe. N₂ appears to be labilised by cis-ligands in the order t-BuNC > CNMe > N₂ > NCR.     

Thermal reactivity of cis- and trans-bis(triphenylgermyl)bis(tertiary phosphine)platinum(II)

The complex cis-Pt(Ph₃Ge)₂(PMe₂Ph)₂ underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, ΔH^# = 105 kJ mol⁻¹, ΔS^# = 12.5 J mol⁻¹ K⁻¹, and Ea = 107 kJ mol⁻¹, respectively. Heating of trans-Pt(Ph₃Ge)₂(PMe₂Ph)₂ at 50 °C for 36 days produced trans-PtPh(Ph₃Ge)(PMe₂Ph)₂ followed by the formation of trans-PtPh₂(PMe₂Ph)₂, Pt(PMe₂Ph)₄, and Ph₄Ge finally via elimination of the phenyl group from Ph₃Ge ligand with liberation of the Ph₂Ge unit and subsequent reductive elimination of the remaining Ph₃Ge ligand at 80 °C for 1 month.