Platinum(II) hydrazido complexes

Reaction of 1,2-dimethylhydrazine with the platinum hydroxo complex [(dppp)Pt(mu-OH)](2)(BF(4))(2) gives the bridging 1,2-dimethylhydrazido(-2) product [(dppp)(2)Pt(2)(mu-eta(2):eta(2)-MeNNMe)](BF(4))(2) 1. Crystals of 1.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are monoclinic (C/2) with a = 19.690(1), b = 18.886(1), c = 17.170 (1) A, and beta = 92.111(1) degrees. Treatment of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1,1-dimethylhydrazine gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNMe(2))](OTf)(2) 2. Crystals of 2.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are triclinic (P-1) with a = 12.910 (3), b = 13.927(3), c = 17.5872 (3) A, alpha = 87.121(3), beta = 89.997(4), and gamma = 84.728(3) degrees. Reaction of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1 equiv of phenylhydrazine in CH(2)Cl(2) gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNHPh)](OTf)(2) 3. Two equivalents of phenylhydrazine with [(dppp)Pt(mu-OH)](2)(X)(2) gives [(dppp)Pt(mu-NHNHPh)](2)(X)(2) 4 (X = BF(4), OTf). Crystals of 3.ClCH(2)CH(2)Cl from ClCH(2)CH(2)Cl/(i)()Pr(2)O are monoclinic (P2(1)/n) with a = 20.990(2), b = 13.098(1), c = 25.773 (2) A, and beta = 112.944(2) degrees. Crystals of 4(X = BF(4)).ClCH(2)CH(2)Cl(.)()2((t)()BuOMe) from ClCH(2)CH(2)Cl/(t)()BuOMe are monoclinic (C2/m) with a = 30.508(1), b = 15.203(1), c = 19.049 (1) A, and beta = 118.505(2) degrees.     

Ni(Et2PCH2NMeCH2PEt2)2]2+ as a functional model for hydrogenases

The reaction of Et(2)PCH(2)N(Me)CH(2)PEt(2) (PNP) with [Ni(CH(3)CN)(6)](BF(4))(2) results in the formation of [Ni(PNP)(2)](BF(4))(2), which possesses both hydride- and proton-acceptor sites. This complex is an electrocatalyst for the oxidation of hydrogen to protons, and stoichiometric reaction with hydrogen forms [HNi(PNP)(PNHP)](BF(4))(2), in which a hydride ligand is bound to Ni and a proton is bound to a pendant N atom of one PNP ligand. The free energy associated with this reaction has been calculated to be -5 kcal/mol using a thermodynamic cycle. The hydride ligand and the NH proton undergo rapid intramolecular exchange with each other and intermolecular exchange with protons in solution. [HNi(PNP)(PNHP)](BF(4))(2) undergoes reversible deprotonation to form [HNi(PNP)(2)](BF(4)) in acetonitrile solutions (pK(a) = 10.6). A convenient synthetic route to the PF(6)(-) salt of this hydride involves the reaction of PNP with Ni(COD)(2) to form Ni(PNP)(2), followed by protonation with NH(4)PF(6). A pK(a) of value of 22.2 was measured for this hydride. This value, together with the half-wave potentials of [Ni(PNP)(2)](BF(4))(2), was used to calculate homolytic and heterolytic Ni-H bond dissociation free energies of 55 and 66 kcal/mol, respectively, for [HNi(PNP)(2)](PF(6)). Oxidation of [HNi(PNP)(2)](PF(6)) has been studied by cyclic voltammetry, and the results are consistent with a rapid migration of the proton from the Ni atom of the resulting [HNi(PNP)(2)](2+) cation to the N atom to form [Ni(PNP)(PNHP)](2+). Estimates of the pK(a) values of the NiH and NH protons of these two isomers indicate that proton migration from Ni to N should be favorable by 1-2 pK(a) units. Cyclic voltammetry and proton exchange studies of [HNi(depp)(2)](PF(6)) (where depp is Et(2)PCH(2)CH(2)CH(2)PEt(2)) are also presented as control experiments that support the important role of the bridging N atom of the PNP ligand in the proton exchange reactions observed for the various Ni complexes containing the PNP ligand. Similarly, structural studies of [Ni(PNBuP)(2)](BF(4))(2) and [Ni(PNP)(dmpm)](BF(4))(2) (where PNBuP is Et(2)PCH(2)N(Bu)CH(2)PEt(2) and dmpm is Me(2)PCH(2)PMe(2)) illustrate the importance of tetrahedral distortions about Ni in determining the hydride acceptor ability of Ni(II) complexes.     

Azametallacycles from Ag(I)- or Cu(II)-promoted coupling reactions of dialkylcyanamides with oximes at Pt(II)

The dialkylcyanamide complexes cis-[PtCl(NCNR(2))(PPh(3))(2)][BF(4)] 1 and cis-[Pt(NCNR(2))(2)(PPh(3))(2)][BF(4)](2) 2 (R = Me or Et) have been prepared by treatment of a CH(2)Cl(2) solution of cis-[PtCl(2)(PPh(3))(2)] with the appropriate dialkylcyanamide and one or two equivalents of Ag[BF(4)], respectively. Compounds 2 can also be obtained from 1 by a similar procedure. Their reaction with oximes, HON=CR'R' ' (R'R' ' = Me(2) or C(4)H(8)), in CH(2)Cl(2) and in the presence of Ag[BF(4)] or Cu(CH(3)COO)(2), leads to the novel type of azametallacycles cis-[Pt(NH=C(ON=CR'R")-NR2)(PPh3)2][BF4]2 4 upon an unprecedented coupling of the organocyanamides with oximes, in a process that proceeds via the mixed oxime-organocyanamide species cis-[Pt(NCNR(2))(HON=CR'R' ')(PPh(3))(2)][BF(4)](2) 3, and is catalyzed by either Ag(+) or Cu(2+) which activate the ligating organocyanamide by Lewis acid addition to the amide group. In contrast, in the organonitrile complexes cis-[Pt(NCR)(2)(PPh(3))(2)][BF(4)](2) 5 (R = C(6)H(4)OMe-4 or Et), obtained in a similar way as 2 (but by using NCR instead of the cyanamide), the ligating NCR is not activated by the Lewis acid and does not couple with the oximes. The spectroscopic properties of those complexes are reported along with the molecular structures of 2b (R = Et), 4a1 (R = Me, R'R' ' = Me(2)), and 4b1 (R = Et, R'R' ' = Me(2)), as established by X-ray crystallography which indicates that in the former complex the amide-N-atoms are trigonal planar, whereas in the latter (4a1 and 4b1) the five-membered rings are planar with a localized N=C double bond (imine group derived from the cyanamide) and the exocyclic amide and alkylidene groups (in 4b1) are involved in two intramolecular H-bonds to the oxygen atom of the ring.     

Synthesis, structures and photophysical properties of luminescent copper(I) and platinum(II) complexes with a flexible naphthyridine-phosphine ligand

Condensation of Ph(2)PH and paraformaldehyde with 2-amino-7-methyl-1,8-naphthyridine gave the new flexible tridentate ligand 2-[N-(diphenylphosphino)methyl]amino-7-methyl-1,8-naphthyridine (L). Reaction of L with [Cu(CH(3)CN)(4)]BF(4) and/or different ancillary ligands in dichloromethane afforded N,P chelating or bridging luminescent complexes [(L)(2)Cu(2)](BF(4))(2), [(micro-L)(2)Cu(2)(PPh(3))(2)](BF(4))(2) and [(L)Cu(CNN)]BF(4) (CNN = 6-phenyl-2,2'-bipyridine), respectively. Complexes [(L)(2)Pt]Cl(2), [(L)(2)Pt](ClO(4))(2) and [(L)Pt(CNC)]Cl (CNC = 2,6-biphenylpyridine) were obtained from the reactions of Pt(SMe(2))(2)Cl(2) or (CNC)Pt(DMSO)Cl with L. The crystal structures and photophysical properties of the complexes are presented.     

Alkene oxidation by a platinum oxo complex and isolation of a platinaoxetane

Oxo complex [(1,5-COD)4Pt4(mu3-O)2Cl2](BF4)2 (1) reacts readily with ethylene and norbornylene. The ethylene reaction yields acetaldehyde and a 1:1 mixture of (1,5-COD)Pt(Cl)(CH2CH3) (2) and [(1,5-COD)Pt4(eta3-CH2CHCH(CH3))](BF4) (3), while the norbornylene reaction yields a platinaoxetane complex, the first metallaoxetane to be obtained from the reaction of an oxo complex and an alkene.     

Brønsted acidic ionic liquids and their zwitterions: synthesis, characterization and pKa determination

Imidazolium chlorides with one or two carboxylic acid substituent groups, 1-methyl-3-alkylcarboxylic acid imidazolium chloride, [Me[(CH2)nCOOH]im]Cl (n=1, 3), and 1,3-dialkylcarboxylic acid imidazolium chloride, [[(CH2)nCOOH]2im]Cl (n=1, 3), have been synthesized via their corresponding acid esters. Deprotonation of the carboxylic acid functionalized imidazolium chlorides with triethylamine affords the corresponding zwitterions [Me[(CH2)nCOO]im] (n=1, 3) and [[(CH2)nCOOH][(CH2)nCOO]im] (n=1, 3). Subsequent reaction of the zwitterions with strong acids gives the new imidazolium salts [Me[(CH2)nCOOH]im]X (n=1, 3; X=BF4, CF3SO3) and [[(CH2)nCOOH]2im]X (n=1, 3; X=BF4, CF3SO3), which exhibit melting points as low as -61 degrees C. The solid-state structures of two of the carboxylic acid functionalized imidazolium salts have been determined by single-crystal X-ray diffraction analysis. Extensive hydrogen bonding is present between the chloride and the imidazolium, with eight Cl.H interactions below 3 A. The pK(a) values of all the salts, determined by potentiometric titration, lie between 1.33 and 4.59 at 25 degrees C.     

Preparation, properties and structures of the first series of organometallic Pt(II) and Pt(IV) complexes with stibine co-ligands

The planar Pt(II) monomers [PtMe2(L-L)] and [(PtMe2)2(L'-L')2] dimers (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2; L'-L' = R2SbCH2SbR2; R = Me or Ph) are obtained in good yield via reaction of [PtMe2(SMe2)2] with L-L or L'-L' in benzene. The Pt(iv) stibines, [PtMe3(L-L)I] (L-L = R2Sb(CH2)3SbR2, o-C6H4(CH2SbMe2)2 or 2 x SbPh3, SbMePh2 or SbMe2Ph) are obtained by treatment of [PtMe3I] with L-L in chloroform. These represent the first series of stable Pt(IV) stibine complexes. All of the products have been characterised by 1H, 13C{1H}, 195Pt NMR spectroscopy, electrospray mass spectrometry and analysis. Crystal structure determinations on [PtMe3{R2Sb(CH2)3SbR2}I], [PtMe3{o-C6H4(CH2SbMe2)2}I] and [PtMe3(SbPh3)2I] confirm the distorted octahedral environment at Pt, with fac Me groups and mutually cis Sb donor atoms. The Sb-Pt-Sb angle in the seven-membered chelate ring of the o-C6H4(CH2SbMe2)2 complex is ca. 96 degrees , compared to <90 degrees in the complexes with six-membered chelates. The C1-distibines R2SbCH2SbR2 afford only the dinuclear [(PtMe3)2(mu-R2SbCH2SbR2)(mu-I)2] in which the stibine ligand and two I atoms bridge two Pt atoms giving an edge sharing bioctahedral geometry which has been confirmed by a crystal structure analysis. The Pt(II) species undergo oxidative addition with MeI to give the corresponding Pt(IV) species, while the Pt(IV) species reductively eliminate ethane upon thermolysis.     

Double geminal C-H activation and reversible alpha-elimination in 2-aminopyridine iridium(III) complexes: the role of hydrides and solvent in flattening the free energy surface

[H2Ir(OCMe2)2L2]BF4 (1) (L = PPh3), a preferred catalyst for tritiation of pharmaceuticals, reacts with model substrate 2-(dimethylamino)pyridine (py-NMe2; py = 2-pyridyl) to give chelate carbene [H2Ir(py-N(Me)CH=)L2]BF4 (2a) via cyclometalation, H2 loss, and reversible alpha-elimination. Agostic intermediate [H2Ir(py-N(Me)CH2-H)L2]BF4) (4a), seen by NMR, is predicted (DFT(B3PW91) computations) to give C-H oxidative addition to form the alkyl intermediate [(H)(eta2-H2)Ir(py-N(Me)CH2-)L2]BF4. Loss of H2 leads to the fully characterized alkyl [HIr(OCMe2)(py-N(Me)CH2-)L2]BF4 (3a(Me2CO)), which loses acetone to give alkylidene hydride 2a by rapid reversible alpha-elimination. 2a rapidly reacts with excess H2 in d6-acetone to generate [H2Ir(OC(CD3)2)2L2]BF4 (1-d12), 3a((CD3)2CO), and py-NMe2 in a 1:1:1 ratio, showing reversibility and accounting for the selective isotope exchange catalyzed by 1. Reaction of 1 with py-N(CH2)4 gives the fully characterized carbene 2c. A cis-L(2) carbene intermediate, cis-2c, observed by NMR, reacts with CO via retro alpha-elimination to give the alkyl 3cCO, while the trans isomer, 2c, does not react; retro alpha-elimination thus requires the Ir-H bond to be orthogonal to the carbene plane. Consistent with experiment, computational studies show a particularly flat PE surface with activation of the agostic C-H bond giving a less stable H2 complex, then formation of a kinetic carbene complex with cis-L, only seen experimentally for py-N(CH2)4. Hydrides at key positions, together with gain or loss of solvent and H2, flatten the PE (DeltaG) surfaces to allow fast catalysis.     

Studies of structural effects on the half-wave potentials of mononuclear and dinuclear nickel(II) diphosphine/dithiolate complexes

Two series of mononuclear Ni(II) complexes of the formula (PNP)Ni(dithiolate) where PNP = R2PCH2N(CH3)CH2PR2, R = Et and Ph, have been synthesized containing dithiolate ligands that vary from five- to seven-membered chelate rings. Two series of dinuclear Ni(II) complexes of the formula {[(diphosphine)Ni]2(dithiolate)}(X)2 (X = BF4 or PF6) have been synthesized in which the chelate ring size of the dithiolate and diphosphine ligands have been systematically varied. The structures of the alkylated mononuclear complex, [(PNPEt)Ni(SC2H4SMe)]OTf, and the dinuclear complex, [(dppeNi)2(SC3H6S)](BF4)2, have been determined by X-ray diffraction studies. The complexes have been studied by cyclic voltammetry to determine how the half-wave potentials of the Ni(II/I) couples vary with chelate ring size of the ligands. For the mononuclear complexes, this potential becomes more positive as the natural bite angle of the dithiolate ligand increases. However, the potentials of the Ni(II/I) couples of the dinuclear complexes do not show a dependence on the chelate ring size of the ligands. Other aspects of the reduction chemistry of these complexes have been explored.     

Synthesis and platinum coordination chemistry of the perfluoroalkyl acceptor pincer ligand, 1,3-(CH(2)P(CF(3))(2))(2)C(6)H(4)

The synthesis of perfluoroalkyl-substituted "pincer"-type PCP ligands, 1,3-C6H4(CH2P(Rf)2)2 (Rf = CF3, C2F5), and platinum coordination studies (Rf = CF3) are reported. 1,3-C6H4(CH2P(CF3)2)2 (CF3PCPH) reacts at ambient temperatures with (cod)Pt(Me)Cl (cod = 1,5-cyclooctadiene) and (cod)PtMe2 to afford unmetalated PCPH-bridged products [(CF3PCPH)Pt(Me)Cl]x and cis-[(CF3PCPH)PtMe2]2, respectively. cis-[(CF3PCPH)PtMe2]2 is soluble and has been spectroscopically and crystallographically characterized. Thermolysis of these compounds results in the loss of methane and the formation of metalated complexes (CF3PCP)PtCl and (CF3PCP)PtMe. Treatment of (CF3PCP)PtCl with MeMgBr provides an alternative route to (CF3PCP)PtMe. The carbonyl cation (CF3PCP)Pt(CO)+SbF6- (nu(CO) = 2143 cm(-1)) was readily prepared by chloride abstraction with AgSbF6 under 1 atm CO. nu(CO) data indicates that RfPCP ligands are electronically analogous to trans acceptor phosphine complexes such as trans-((C2F5)2PMe)2Pt(Me)(CO)+ (nu(CO) = 2149 cm-1).     

Tuning the strain and polymerizability of organometallic rings: the synthesis, structure, and ring-opening polymerization behavior of [2]ferrocenophanes with C-SI, C-P, and C-S bridges.

A series of novel [2]ferrocenophanes with unsymmetrical C-E bridges has been prepared in which the covalent radius of the second-row element, E, and hence the ring strain present is varied. Species [Fe(eta-C(5)Me(4))(eta-C(5)H(4))CH(2)ER(x)] (7, ER(x) = SiMe(2); 8a, ER(x) = PPh; 8b, ER(x) = PMes; 9, ER(x) = S) were synthesized via reaction of the PMDETA (N,N,N',N' ',N' '-pentamethyldiethylenetriamine) adduct of [(eta-C(5)H(4)Li)Fe(eta-C(5)Me(4))CH(2)Li] with Cl(2)ER(x) (E = Si or P) or S(SO(2)Ph)(2). Studies of 7-9 by single-crystal X-ray diffraction confirmed the presence of ring-tilted structures: for 7, alpha (angle between the planes of the Cp rings) = 11.8(1) degrees; for 8a, alpha(average) = 14.9(3) degrees; for 8b, alpha(average) = 18.2(2) degrees; and for 9, alpha = 18.5(1) degrees. The least tilted compound, 7, was found to be resistant to thermal, anionic, and transition metal catalyzed ROP. In contrast, the significantly more tilted compounds 8a, 8b, and 9 were all found to polymerize thermally with small negative values of DeltaH(ROP) of ca. 10-20 kJ.mol(-1) determined by DSC. Whereas thermal ROP of 8a yielded the soluble high molecular weight polycarbophosphaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PPh](n) (11), species 9 formed the insoluble polycarbothiaferrocene [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n) (14). Attempted anionic ROP of 8a and 9 with (n)BuLi was unsuccessful and treatment of 8a with CF(3)SO(3)Me resulted in the formation of the novel phosphonium salt [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PMePh][CF(3)SO(3)] (13), which was found to be resistant to thermal ROP as a result of its less strained structure (for 13, alpha = 11.4(7) degrees ). Treatment of 9 with CF(3)SO(3)Me or BF(3).Et(2)O resulted in the first example of cationic ROP for a transition metal-containing heterocycle to yield polycarbothiaferrocene 14. In the presence of excess 2,6-di-tert-butylpyridine as a selective proton trap, ROP of 9 was only observed with CF(3)SO(3)Me, and not BF(3).Et(2)O, which indicated that Me(+) and H(+) are the probable cationic initiators, respectively. Thermal copolymerization of 9 with trimethylene sulfide resulted in the isolation of the soluble, high molecular weight, random copolymer [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S](n)[(CH(2))(3)S](m), 15.     

Olefin metatheses in metal coordination spheres: versatile new strategies for the construction of novel monohapto or polyhapto cyclic, macrocyclic, polymacrocyclic, and bridging ligands

The broad applicability of the title reaction is established through studies of neutral and charged, coordinatively saturated and unsaturated, octahedral and square planar rhenium, platinum, rhodium, and tungsten complexes with cyclopentadienyl, phosphine, and thioether ligands which contain terminal olefins. Grubbs' catalyst, [Ru(=CHPh)(PCy3)2(Cl)2], is used at 2-9 mol% levels (0.0095-0.00042 M, CH2-Cl2). Key data are as follows: [(eta5-C5H4(CH2)6CH=CH2)Re(NO)(PPh3)-(CH3)], intermolecular metathesis (95 %); [(eta5-C5H5)Re(NO)(PPh3)(E(CH2CH=CH2)2)]+ TfO (E=S, PMe, PPh), formation of five-membered heterocycles (96-64%; crystal structure E = PMe); [(eta5-C5Me5)Re(NO)(PPh((CH2)6CH=CH2)2)(L)]n+ nBF4-(L/n = CO/1, Cl/0), intramolecular macrocyclization (94-89%; crystal structure L= Cl); fac-[(CO)3Re(Br)(PPh2(CH2)6CH=CH2)2] and cis-[(Cl)2Pt(PPh2(CH2)6CH=CH2)2], intramolecular macrocyclizations (80-71%; crystal structures of each and a hydrogenation product); cis-[(Cl)2Pt(S(R)(CH2)6CH= CH2)2], intra-/intermolecular macrocyclization (R=Et, 55%/24%; tBu, 72%/ <4%); trans-[(Cl)(L)M(PPh2(CH2)6CH=CH2)2] (M/L = Rh/CO, Pt/C6F5) intramolecular macrocyclization (90-83%; crystal structure of hydrogenation product, M=Pt); fac-[W(CO)3(PPh((CH2)6CH=CH2)2)3], intramolecular trimacrocyclization (83 %) to a complex mixture of triphosphine, diphosphine/ monophosphine, and tris(monophosphine) complexes, from which two isomers of the first type are crystallized. The macrocycle conformations, and basis for the high yields, are analyzed.     

Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides

A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3P=CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4[NH=C(Me)ON=CR1R2]2] [R1R2 = Me2, (CH2)4, (CH2)5, (Me)C(Me)=NOH], [PtCl4[NH=C(Me)ONR2]2] (R = Me, Et, CH2Ph), (R1 = H; R2 = Ph or C6H4Me; R3 = Me) as well as anionic-type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5[NH=C(Me)ON=CR2]] [R2 = Me2, (CH2)4, (CH2)5] and 1 equiv of Ph3P=CHCO2R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Delta4-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and 1H, 13C[1H], 31P[1H] and 195Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2[NH=C(Me)ON=CMe2]2] [crystal system tetragonal, space group P4(2)/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph3PCH2CO2Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna2(1) (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph3P=CHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.     

New family of lithium salts for highly conductive nonaqueous electrolytes

New lithium salts of weakly coordinating anions were prepared by treating lithium imidazolates or LiN(CH3)2 with 2 equiv of BF(3). They are LiIm(BF3)2, Li 2-MeIm(BF3)2, Li 4-MeIm(BF3)2, LiBenzIm(BF3)2, Li 2-iPrIm(BF3)2, and LiN(CH3)2(BF3)2 (Im=imidazolate, Me=methyl, iPr=isopropyl, BenzIm=benzoimidazolate). The salts were characterized by NMR spectroscopy and mass spectrometry. The structure of LiBenzIm(BF3)2 consists of a dimeric centrosymmetric unit with each lithium atom forming a bridge between the two anions through one fluorine contact to each anion. The structure of a hydrate of LiN(CH3)2(BF3)2 consists of an infinite chain in which each anion chelates two different lithium atoms through Li-F bonds. The conductivities of electrolyte solutions of these salts were measured and are discussed in terms of different ion-pairing modes determined from the solid-state structures, the anion's ability to distribute charge, and solution viscosity. Organic carbonate solutions of LiIm(BF3)2 partially disproportionate at 85 degrees C forming LiBF4, LiBF2[Im(BF3)]2, and Li[(BF3)ImBF2ImBF2Im(BF3)], reaching equilibrium by 3 months at 85 degrees C but not disproportionating at room temperature after 9 months. A mechanism for the formation of these disproportionation products is proposed. The lower conductivity of the 1 M LiIm(BF3)2 solution that has undergone disproportionation is attributed to the formation LiBF4, which is less conductive, and LiBF2[Im(BF3)]2 and Li[(BF3)ImBF2ImBF2Im(BF3)], which increase solution viscosity.     

An unprecedented process involving normal and redox transmetallation reactions between Hg and Pt affording the unexpected K[Pt2[CH2C(O)Me]6(mu-Cl)3] complex: the key role of X-ray powder diffraction in unravelling its nature and structure

[Hg{CH2C(O)Me}2] reacts with K[PtCl3(CH2=CH2)](2 : 1 molar ratio) to give K[Pt2{CH2C(O)Me}6(mu-Cl)3] (1); the intermediate [Pt{CH2C(O)Me}Cl2(CH2=CH2)]- has been detected in solution and isolated as a Me4N+ salt; the process occurs through successive normal and redox transmetallation reactions and an ab initio X-ray powder diffraction study of has proven to be essential to establish its nature.     

Synthesis of carbaalane halogen derivatives

The carbaalane halogen derivatives [(AlX)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (X = F (9), Cl (7), Br (10), I (11)) were prepared in toluene from [(AlH)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (6) and BF(3).OEt(2), BX(3) (X = Br, I), Me(3)SnF, and Me(3)SiX (X = Cl, Br, I), respectively. A partially halogenated product [(AlH)(2)(AlX)(4)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (12) (X = Cl (approximately 40%), Br (approximately 60%)) was obtained from 5 and impure BBr(3). [(AlH)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (5) was converted to [(AlX)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (X = F (13), Cl (14), Br (15), I (16)) using BF(3).OEt(2) and Me(3)SiX (X = Cl, Br, I), respectively. The X-ray single-crystal structures of 11.C(6)H(6), 12.3C(7)H(8), 13.6C(7)H(8), and 15.4C(7)H(8) were determined. Compounds 7 and 9-11 are soluble in benzene/toluene and could be well characterized by NMR spectroscopy and MS (EI) spectrometry. The results demonstrate the facile substitution of the hydridic hydrogen atoms in 5 and 6 by the halides with different reagents.     

cyclo-CH2[Sn(CI2)CH2Si(Me2)]2O]: synthesis and complexation behaviour of a novel, cyclic, bidentate Lewis acid and its conversion into a tin-containing fluorosilane with intermolecular Si-F...Sn bridges

Acid-catalysed hydrolysis of [CH2[(Sn(Ph2)CH2Si(OiPr)Me2]2] followed by subsequent reaction with mercuric chloride in acetone afforded the novel silicon- and tin-containing eight-membered ring [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] in good yield, the crystal structure of which is reported. 119Sn NMR and X-ray studies indicate that [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] acts as a bidentate Lewis acid towards chloride ions exclusively forming the 1:1 complex [(Ph3P)2N]+[cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2OCl]- upon addition of [(Ph3P)2N]+Cl- . Also reported are the synthesis and structure of [K(dibenzo[18]crown-6)]+[cyclo-CH2(Sn(Cl2)CH2Si(Me2)]2OF]-, the first completely characterised organostannate with a C2SnCl2F- substituent pattern. No ring-opening polymerisation could be achieved for [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] or for its perphenylated derivative [cyclo-CH2[Sn(Ph2)CH2Si(Me2)]2O]. The reaction of [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] with Me3O+BF4- gave the tin-containing fluorosilane [CH2[Sn(Cl2)CH2Si(F)Me2]2], in which the Si-F bond is activated by intermolecular Si-F...Sn interactions in the solid state.     

Reductive elimination/oxidative addition of carbon-hydrogen bonds at Pt(IV)/Pt(II) centers: mechanistic studies of the solution thermolyses of Tp(Me2)Pt(CH3)2H

Reductive elimination of methane occurs upon solution thermolysis of kappa(3)-Tp(Me)2Pt(IV)(CH(3))(2)H (1, Tp(Me)2 = hydridotris(3,5-dimethylpyrazolyl)borate). The platinum product of this reaction is determined by the solvent. C-D bond activation occurs after methane elimination in benzene-d(6), to yield kappa(3)-Tp(Me)2Pt(IV)(CH(3))(C(6)D(5))D (2-d(6)), which undergoes a second reductive elimination/oxidative addition reaction to yield isotopically labeled methane and kappa(3)-Tp(Me)2Pt(IV)(C(6)D(5))(2)D (3-d(11)). In contrast, kappa(2)-Tp(Me)2Pt(II)(CH(3))(NCCD(3)) (4) was obtained in the presence of acetonitrile-d(3), after elimination of methane from 1. Reductive elimination of methane from these Pt(IV) complexes follows first-order kinetics, and the observed reaction rates are nearly independent of solvent. Virtually identical activation parameters (DeltaH(++)(obs) = 35.0 +/- 1.1 kcal/mol, DeltaS(++)(obs) = 13 +/- 3 eu) were measured for the reductive elimination of methane from 1 in both benzene-d(6) and toluene-d(8). A lower energy process (DeltaH(++)(scr) = 26 +/- 1 kcal/mol, DeltaS(++)(scr) = 1 +/- 4 eu) scrambles hydrogen atoms of 1 between the methyl and hydride positions, as confirmed by monitoring the equilibration of kappa(3)-Tp(Me)()2Pt(IV)(CH(3))(2)D (1-d(1)()) with its scrambled isotopomer, kappa(3)-Tp(Me)2Pt(IV)(CH(3))(CH(2)D)H (1-d(1'). The sigma-methane complex kappa(2)-Tp(Me)2Pt(II)(CH(3))(CH(4)) is proposed as a common intermediate in both the scrambling and reductive elimination processes. Kinetic results are consistent with rate-determining dissociative loss of methane from this intermediate to produce the coordinatively unsaturated intermediate [Tp(Me)2Pt(II)(CH(3))], which reacts rapidly with solvent. The difference in activation enthalpies for the H/D scrambling and C-H reductive elimination provides a lower limit for the binding enthalpy of methane to [Tp(Me)2Pt(II)(CH(3))] of 9 +/- 2 kcal/mol.     

Early-late heterobimetallic Rh-Ti and Rh-Zr complexes via addition of early metal chlorides to mono- and divalent rhodium

Addition of TiCl(4) or ZrCl(4) to (PNP)Rh(CH(2)==CH(t)Bu) (1) rapidly gives complexes (PNP)Rh(MCl(3))(Cl) (M = Ti, 2; Zr, 3) in 75-77% yield (PNP = (4-Me-2-((i)Pr(2)P)-C(6)H(3))(2)N). Compound 2 can also be synthesized via a reaction of (PNP)RhCl with TiCl(3) or of (PNP)TiCl(3) with 1/2 [(cod)RhCl](2).     

Ligand cleavage put into reverse: P--C bond breaking and remaking in an alkylphosphane iron complex

Complex formation between FeX(2)6 H(2)O (X=BF(4) or ClO(4)) and the pyridine-derived tetrapodal tetraphosphane C(5)H(3)N[CMe(CH(2)PMe(2))(2)](2) (1) in methanol proceeds with solvent-induced cleavage of one PMe(2) group. Depending on the reaction temperature and the nature of the counterion, iron(II) is coordinated, in distorted square-pyramidal fashion, by the anionic remainder of the chelating ligand, C(5)H(3)N[CMe(CH(2)PMe(2))(2)][CMe(CH(2)PMe(2))(CH(2) (-))] (NP(3)C(-) donor set: X=BF(4), -50 degrees C: 2; X=ClO(4), RT: 4) or its protonated form C(5)H(3)N[CMe(CH(2)PMe(2))(2)][CMe(CH(2)PMe(2))(CH(3))], in which the methyl group is in agostic interaction with the metal centre (X=BF(4), RT: 3; X=ClO(4), +50 degrees C: 5). A monodentate phosphinite ligand Me(2)POMe, formed from the cleaved PMe(2) group and methanol, completes the coordination octahedron in both cases. Working in CD(3)OD (X=BF(4), RT) gives the deuterium-substituted analogue of 3, with ligands L(CH(2)D) (L=residual chelating ligand) and Me(2)POCD(3). A mechanism for the observed phosphorus-carbon bond cleavage is suggested. Complex 2, when isolated at -50 degrees C, is stable in the solid state even at room temperature. The reaction of 2 in methanol with carbon monoxide (10.5 bar) at elevated temperature forms, in addition to as yet unidentified side products, the carbonyl complex [(1)Fe(CO)](BF(4))(2) (7), in which the previous P--C bond cleavage has been reversed, reforming the original tetrapodal pentadentate NP(4) ligand 1. All compounds have been fully characterised, including X-ray structure analyses in most cases.