A monometallic Rh(III) tetraphosphine complex: reductive activation of CH2Cl2 and selective meso to racemic tetraphosphine ligand isomerization

The first Rh complex with an eta(4)-coordinated rac-et,ph-P4 ligand [et,ph-P4 = (Et2PCH2CH2)(Ph)PCH2P(Ph)(CH2CH2PEt2)] has been synthesized by reacting [Rh(nbd)2]BF4 with meso- or rac-et,ph-P4 in dichloromethane. The reaction occurs fairly rapidly at room temperature to form [rac-RhCl2(eta(4)-et,ph-P4)](+) in high yields, regardless of whether one starts with mixed or even pure meso-et,ph-P4 ligand. This unusual and highly selective metal assisted isomerization of the meso-et,ph-P4 ligand to its rac-et,ph-P4 disastereomer will be discussed.     

Synthesis of beta-P,N aminophosphines and coordination chemistry to Pd(II). X-ray structures of [PdCl2(Ph2PCH(Ph)NHPh-kappaP,kappaN)] and PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)

The reaction of the C=N bond in PhCH=NPh with the carbanionic species Ph2PCH2-, leading to the N-phenyl beta-aminophosphine Ph2PCH2CH(Ph)NHPh, L1, is described. This molecule reacts with different organic electrophiles to afford related compounds Ph2PCH2CH(Ph)NPhX (X = SiMe3, L2; COPh, L4), [Ph2MePCH2CH(Ph)NHPh]+(I-), L3, and [Ph2PCH2CH(Ph)N(Ph)CO]2, L5, containing two amido and two phosphino functions. The coordination properties of L1, L2, and L4 have been studied in palladium chemistry. The X-ray structure of [PdCl2(Ph2PCH2CH(Ph)NHPh-kappaP,kappaN)] shows the bidentate coordination mode for the L1 ligand with equatorial C(Ph)-N(Ph) phenyl groups. [PdCl2(Ph2PCH2CH(Ph)NHPh-kappaP,kappaN)] crystallizes at 298 K in the space group P2(1)/n with cell parameters a = 10.689(2) A, b = 21.345(3) A, c = 12.282(2) A, beta = 90.294(12) degrees, Z = 4, D(calcd) = 1.526. The reaction between 2 equiv of L1 and [PdCl(eta3-C3H5)]2 affords the [PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)] complex in which an unexpected N-H.Cl intramolecular interaction has been observed by an X-ray diffraction analysis. [PdCl(eta3-C3H5)(Ph2PCH2CH(Ph)NHPh-kappaP)] crystallizes at 298 K in the monoclinic space group Cc with cell parameters a = 10.912(1) A, b = 17.194(2) A, c = 14.169(2) A, beta = 100.651(9) degrees, Z = 4, D(calcd) = 1.435. Neutral and cationic alkyl or allyl palladium chloride complexes containing L1 are also reported as well as a neutral allyl palladium chloride complex containing L4. Variable-temperature 31P[1H] NMR studies on the allyl complexes show that the eta3/eta1 allyl interconversion is enhanced by a positive charge and also by a N-H.Cl intramolecular interaction.     

Ruthenium(II) and ruthenium(IV) complexes containing kappa1-P-, kappa2-P,O-, and kappa3-P,N,O-iminophosphorane-phosphine ligands Ph2PCH2P[=NP(=O)(OR)2]Ph2 (R = Et,Ph): synthesis,reactivity, theoretical studies,and catalytic activity in transfer hydrogenation of cyclohexanone

[(Ru(eta(6)-p-cymene)(mu-Cl)Cl)(2)] and [(Ru(eta(3):eta(3)-C(10)H(16))(mu-Cl)Cl)(2)] react with Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2) (R = Et (1a), Ph (1b)) affording complexes [Ru(eta(6)-p-cymene)Cl(2)(kappa(1)-P-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))] (R = Et (2a), Ph (2b)) and [Ru(eta(3):eta(3)-C(10)H(16))Cl(2)(kappa(1)-P-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))] (R = Et (6a), Ph (6b)). While treatment of 2a with 1 equiv of AgSbF(6) yields a mixture of [Ru(eta(6)-p-cymene)Cl(kappa(2)-P,O-Ph(2)PCH(2)P[=NP(=O)(OEt)(2)]Ph(2))][SbF(6)] (3a) and [Ru(eta(6)-p-cymene)Cl(kappa(2)-P,N-Ph(2)PCH(2)P[=NP(=O)(OEt)(2)]Ph(2))][SbF(6)] (4a), [Ru(eta(6)-p-cymene)Cl(kappa(2)-P,O-Ph(2)PCH(2)P[=NP(=O)(OPh)(2)]Ph(2))][SbF(6)] (3b) and [Ru(eta(3):eta(3)-C(10)H(16))Cl(kappa(2)-P,O-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))][SbF(6)] (R = Et (7a), Ph (7b)) are selectively formed from 2b and 6a,b. Complexes [Ru(eta(6)-p-cymene)(kappa(3)-P,N,O-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))][SbF(6)](2) (R = Et (5a), Ph (5b)) and [Ru(eta(3):eta(3)-C(10)H(16))(kappa(3)-P,N,O-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))][SbF(6)](2) (R = Et (8a), Ph (8b)) have been prepared using 2 equiv of AgSbF(6). The reactivity of 3-5a,b has been explored allowing the synthesis of [Ru(eta(6)-p-cymene)X(2)(kappa(1)-P-Ph(2)PCH(2)P[=NP(=O)(OR)(2)]Ph(2))] (R = Et, Ph; X = Br, I, N(3), NCO (9-12a,b)). The catalytic activity of 2-8a,b in transfer hydrogenation of cyclohexanone, as well as theoretical calculations on the models [Ru(eta(6)-C(6)H(6))Cl(kappa(2)-P,N-H(2)PCH(2)P[=NP(=O)(OH)(2)]H(2))]+ and [Ru(eta(6)-C(6)H(6))Cl(kappa(2)-P,O-H(2)PCH(2)P[=NP(=O)(OH)(2)]H(2))]+, has been also studied.     

Synthesis and structure of CpMo(CO)(dppe)H and its oxidation by Ph3C+

The reaction of CpMo(CO)(dppe)Cl (dppe = Ph2PCH2CH2PPh2) with Na+[AlH2(OCH2CH2OCH3)2]- gives the molybdenum hydride complex CpMo(CO)(dppe)H, the structure of which was determined by X-ray crystallography. Electrochemical oxidation of CpMo(CO)(dppe)H in CH3CN is quasi-reversible, with the peak potential at -0.15 V (vs Fc/Fc+). The reaction of CpMo(CO)(dppe)H with 1 equiv of Ph3C+BF4- in CD3CN gives [CpMo(CO)(dppe)(NCCD3)]+ as the organometallic product, along with dihydrogen and Gomberg's dimer (which is formed by dimerization of Ph3C.). The proposed mechanism involves one-electron oxidation of CpMo(CO)(dppe)H by Ph3C+ to give the radical-cation complex [CpMo(CO)(dppe)H].+. Proton transfer from [CpMo(CO)(dppe)H].+ to CpMo(CO)(dppe)H, loss of dihydrogen from [CpMo(CO)(dppe)(H)2]+, and oxidation of Cp(CO)(dppe)Mo. by Ph3C+ lead to the observed products. In the presence of an amine base, the stoichiometry changes, with 2 equiv of Ph3C+ being required for each 1 equiv of CpMo(CO)(dppe)H because of deprotonation of [CpMo(CO)(dppe)H].+ by the amine. Protonation of CpMo(CO)(dppe)H by HOTf provides the dihydride complex [CpMo(CO)(dppe)(H)2]+OTf-, which loses dihydrogen to generate CpMo(CO)(dppe)(OTf).     

Formation of P-C bonds under unexpectedly mild conditions. Phosphoryl migration and metal coordination of diphenylphosphinomethyl-oxazolines and -thiazolines

The heterocycles 2-methyl-2-oxazoline (mox) and 2-methyl-2-thiazoline (mth) react with Ph2PCl under mild conditions, in the presence of NEt3 which promotes their phosphorylation by stabilization of their enamino tautomers mox(e) and mth(e), respectively, and which also behaves as HCl scavenger. Depending on the reaction conditions, three different phosphine ligands were obtained in good yields from mox: the monophosphine Ph2PCH2C=NCH2CH2O (1ox) and the isomeric diphosphines Ph2PCH=COCH2CH2NPPh2 (2ox) (X-ray structure) and (Ph2P)2CHC=NCH2CH2O (3ox). The formation of these ligands involves phosphoryl migration reactions, which were studied by NMR spectroscopy. The synthesis and the X-ray structures of the corresponding diphenylphosphinothiazolines Ph2PCH2C=NCH2CH2S (1th) and Ph2CH=CSCH2CH2NPPh2 (2th) are also reported but the thiazoline analog of the geminal diphosphine 3ox was not observed. The metal complexes [Pt(3ox-H)2] x 4 CH2Cl2 (4 x 4 CH2Cl2), [Pt(Me)I(1ox)] (5), [Pt(Me)2(1ox)] (7), [Pd(dmba-C,N)(1th)]OTf x 0.25 Et2O (8 x 0.25 Et2O), [Pd(dmba-C,N)(1th-H)] (9), and [9 x {Pd(dmba-C,N)Cl}] x 2.5 C6H6 (10 x 2.5 C6H6) have been prepared and structurally characterized by X-ray diffraction.     

Phosphaallyl complexes of Ru(II) derived from dicyclohexylvinylphosphine (DCVP)

The complexes [(eta5-RC5H4)Ru(CH3CN)3]PF6(R = H, CH3) react with DCVP (DCVP = Cy2PCH=CH2) at room temperature to produce the phosphaallyl complexes [(eta5-C5H5)Ru(eta1-DCVP)(eta3-DCVP)]PF6 and [(eta5-MeC5H4)Ru(eta1-DCVP)(eta3-DCVP)]PF6. Both compounds react with a variety of two-electron donor ligands displacing the coordinated vinyl moiety. In contrast, we failed to prepare the phosphaallyl complexes [(eta5-C5Me5)Ru(eta1-DCVP)(eta3-DCVP)]PF6, [(eta5-MeC5H4)Ru(CO)(eta3-DCVP)]PF6 and [(eta5-C5Me5)Ru(CO)(eta3-DPVP)]PF6(DPVP = Ph2PCH=CH2).The compounds [(eta5-MeC5H4)Ru(CO)(CH3CN)(DPVP)]PF6 and [(eta5-C5Me5)Ru(CO)(CH3CN)(DPVP)]PF6 react with DMPP (3,4-dimethyl-1-phenylphosphole) to undergo [4 + 2] Diels-Alder cycloaddition reactions at elevated temperature. Attempts at ruthenium catalyzed hydration of phenylacetylene produced neither acetophenone nor phenylacetaldehyde but rather dimers and trimers of phenylacetylene. The structures of the complexes described herein have been deduced from elemental analyses, infrared spectroscopy, 1H, 13C{1H}, 31P{1H} NMR spectroscopy and in several cases by X-ray crystallography.     

Complexation of the triply-bonded dirhenium(II) complex Re(2)Cl(4)(mu-dppm)(2) (dppm = Ph(2)PCH(2)PPh(2)) by up to three acetylene molecules

The triply bonded dirhenium(II) synthons Re(2)X(4)(mu-dppm)(2) (X = Cl, Br; dppm = Ph(2)PCH(2)PPh(2)) react with acetylene at room temperature in CH(2)Cl(2) and acetone to afford the bis(acetylene) complexes Re(2)X(4)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH) (X = Cl (3), Br(4)). Compound 3 has been derivatized by reaction with RNC ligands in the presence of TlPF(6) to give unsymmetrical complexes of the type [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH)(CNR)]PF(6) (R = Xyl (5), Mes (6), t-Bu (7)), in which the RCN ligand has displaced the chloride ligand cis to the eta(2)-HCCH ligand. The reaction of 3 with an additional 1 equiv of acetylene in the presence of TlPF(6) gives the symmetrical all-cis isomer of [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH)(2)]PF(6) (8). The two terminal eta(2)-HCCH ligands in 8 are very labile and can be displaced by CO and XylNC to give the complexes [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(L)(2)]Y (L = CO when Y = PF(6) (9); L = CO when Y = (PF(6))(0.5)/(H(2)PO(4))(0.5) (10); L = XylNC when Y = PF(6) (11)). These substitution reactions proceed with retention of the all-cis stereochemistry. Single-crystal X-ray structure determinations have been carried out on complexes 3, 5, 8, 10, and 11. In no instance have we found that the acetylene ligands undergo reductive coupling reactions.     

Spontaneous formation of heteroligated PtII complexes with chelating hemilabile ligands

The spontaneous formation of the heteroligated complex [PtCl(kappa(2)-Ph(2)PCH(2)CH(2)SMe)(Ph(2)PCH(2)CH(2)SPh)]Cl (8 a) by a novel ligand rearrangement process has been observed. By using the weak-link approach, the relative arrangement of the alkyl and aryl groups can be controlled by abstraction of chloride from 8 a to form the closed complex [Pt(kappa(2)-Ph(2)PCH(2)CH(2)SMe)(kappa(2)-Ph(2)PCH(2)CH(2)SPh)][BF(4)](2) (5) and reopening using halide ions to form semi-open complexes [PtX(kappa(2)-Ph(2)PCH(2)CH(2)SMe)(Ph(2)PCH(2)CH(2)SPh)]BF(4) (8 b; X=Cl(-)) and (8 c; X=I(-)). Analogous procedures using Ph(2)PCH(2)CH(2)SMe and 1,4-(Ph(2)PCH(2)CH(2)S)(2)C(6)H(4) lead to heteroligated bimetallic complexes 7 and 9, illustrating that this ligand rearrangement process can be used as a tool for the assembly of complementary metallosupramolecular structures.     

New mode of coordination for the dinitrogen ligand: formation, bonding, and reactivity of a tantalum complex with a bridging N(2) unit that is both side-on and end-on.

The reaction of a mixture of 1 equiv of PhPH(2) and 2 equiv of PhNHSiMe(2)CH(2)Cl with 4 equiv of Bu(n)Li followed by the addition of THF generates the lithiated ligand precursor [NPN]Li(2).(THF)(2) (where [NPN] = PhP(CH(2)SiMe(2)NPh)(2)). The reaction of [NPN]Li(2).(THF)(2) with TaMe(3)Cl(2) produces [NPN]TaMe(3), which reacts under H(2) to yield the diamagnetic dinuclear Ta(IV) tetrahydride ([NPN]Ta)(2)(mu-H)(4). This hydride reacts with N(2) with the loss of H(2) to produce ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)), which was characterized both in solution and in the solid state, and contains strongly activated N(2) bound in the unprecedented side-on end-on dinuclear bonding mode. A density functional theory calculation on the model complex [(H(3)P)(H(2)N)(2)Ta(mu-H)](2)(mu-eta(1):eta(2)-N(2)) provides insight into the molecular orbital interactions involved in the side-on end-on bonding mode of dinitrogen. The reaction of ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)) with propene generates the end-on bound dinitrogen complex ([NPN]Ta(CH(2)CH(2)CH(3)))(2)(mu-eta(1):eta(1)-N(2)), and the reaction of [NPN]Li(2).(THF)(2) with NbCl(3)(DME) generates the end-on bound dinitrogen complex ([NPN]NbCl)(2)(mu-eta(1):eta(1)-N(2)). These two end-on bound dinitrogen complexes provide evidence that the bridging hydride ligands are responsible for the unusual bonding mode of dinitrogen in ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)). The dinitrogen moiety in the side-on end-on mode is amenable to functionalization; the reaction of ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)) with PhCH(2)Br results in C-N bond formation to yield [NPN]Ta(mu-eta(1):eta(2)-N(2)CH(2)Ph)(mu-H)(2)TaBr[NPN]. Nitrogen-15 NMR spectral data are provided for all the tantalum-dinitrogen complexes and derivatives described.     

Preparation and characterization of diarylphosphazene and diarylphosphinohydrazide complexes of titanium, tungsten and ruthenium and phosphorylketimido complexes of rhenium

Reaction of the proligand Ph2PN(SiMe3)2 (L1) with WCl6 gives the oligomeric phosphazene complex [WCl4(NPPh2)]n, 1 and subsequent reaction with PMe2Ph or NBu4Cl gives [WCl4(NPPh2)(PMe2Ph)] (2) or [WCl5(NPPh2)][NBu4] (3), respectively. DF calculations on [WCl5(NPPh2)][NBu4] show a W=N double bond (1.756 A) and a P-N bond distance of 1.701 A, which combined with the geometry about the P atom suggests, there is no P-N multiple bonding. Reaction of L1 with [ReOX3(PPh3)2] in MeCN (X = Cl or Br) gives [ReX2(NC(CH3)P(O)Ph2)(MeCN)(PPh3)](X = Cl, 4, X = Br, 5) which contains the new phosphorylketimido ligand. It is bound to the rhenium centre with a virtually linear Re-N-C arrangement (Re-N-C angle = 176.6 degrees, when X = Cl) and there is multiple bonding between Re and N (Re-N = 1.809(7) A when X = Cl). The proligand Ph2PNHNMe2(L2H) reacts with [(C5H5)TiCl3] to give [(C5H5)TiCl2(Me2NNPPh2)] (6). An X-ray crystal structure of the complex shows the ligand (L2) is bound by both nitrogen atoms. Reaction of the proligands Ph2PNHNR2[R2 = Me2 (L2H), -(CH2CH2)2NCH3 (L3H), (CH2CH2)2CH2 (L4H)] with [{RuCl(mu-Cl)(eta6-p-MeC6H4iPr)}2] gave [RuCl2(eta6-p-MeC6H4iPr)L] {L = L2H (7), L3H (8), L4H (9)}. The X-ray crystal structures of 7-9 confirmed that the phosphinohydrazine ligand is neutral and bound via the phosphorus only. Reaction of complexes 7-9 with AgBF4 resulted in chloride ion abstraction and the formation of the cationic species [RuCl(6-p-MeC6H4iPr)(L)]+ BF4- {(L = L2H (10), L3H (11), L4H (12)}. Finally, reaction of complex 6 with [{RuCl(mu-Cl)(eta6-p-MeC6H4iPr)}2] gave the binuclear species [(eta6-p-MeC6H4iPr)Cl2Ru(mu2,eta3-Ph2PNNMe2)TiCl2(C5H5)], 13.     

Unexpected metal-induced isomerisms and phosphoryl migrations in Pt(II) and Pd(II) complexes of the functional phosphine 2-(bis(diphenylphosphino)methyl)-oxazoline

The reaction of the functional diphosphine 1 [1 = 2-(bis(diphenylphosphino)methyl-oxazoline] with [PtCl(2)(NCPh)(2)] or [PdCl(2)(NCPh)(2)], in the presence of excess NEt(3), affords [Pt{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}(2)] ([Pt(1(-H)-P,P)(2)], 3a) and [Pd{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}(2)] ([Pd(1(-H)-P,P)(2)], 3b), respectively, in which 1(-H) is (oxazoline-2-yl)bis(diphenylphosphino)methanide. The reaction of 3b with 2 equiv of [AuCl(tht)] (tht = tetrahydrothiophene) afforded [Pd(1(-H)-P,N)(2)(AuCl)(2)] (4), as a result of the opening of the four-membered metal chelate since ligand 1(-H), which was P,P-chelating in 3b, behaves as a P,N-chelate toward the Pd(II) center in 4 and coordinates to Au(I) through the other P donor. In the absence of a base, the reaction of ligand 1 with [PtCl(2)(NCPh)(2)] in MeCN or CH(2)Cl(2) afforded the isomers [Pt{(Ph(2)P)(2)C═C(OCH(2)CH(2)NH)}(2)]Cl(2) ([Pt(1'-P,P)(2)]Cl(2) (5), 1' = 2-(bis(diphenylphosphino)methylene)-oxazolidine) and [Pt{(Ph(2)P)(2)C═C(OCH(2)CH(2)NH)}{Ph(2)PCH═C(OCH(2)CH(2)N(PPh(2))}]Cl(2) ([Pt(1'-P,P)(2'-P,P)]Cl(2) (6), 2' = (E)-3-(diphenylphosphino)-2-((diphenylphosphino)methylene)oxazolidine]. The P,P-chelating ligands in 5 result from a tautomeric shift of the C-H proton of 1 to the nitrogen atom, whereas the formation of one of the P,P-chelates in 6 involves a carbon to nitrogen phosphoryl migration. The reaction of 5 and 6 with a base occurred by deprotonation at the nitrogen to afford 3a and [Pt{(Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}{Ph(2)PCH═COCH(2)CH(2)N(PPh(2))}]Cl ([Pt(1(-H)-P,P)(2'-P,P)]Cl (7)], respectively. In CH(2)Cl(2), an isomer of 3a, [Pt{Ph(2)P)(2)C···C(···NCH(2)CH(2)O)}{Ph(2)PC(PPh(2))═COCH(2)CH(2)N}] ([Pt(1(-H)-P,P)(1(-H)-P,N)] (8)), was obtained as a side product which contains ligand 1(-H) in two different coordination modes. Complexes 3b·4CH(2)Cl(2), 4·CHCl(3), 6·2.5CH(2)Cl(2), and 8·CH(2)Cl(2) have been structurally characterized by X-ray diffraction.     

Pendant bases as proton relays in iron hydride and dihydrogen complexes

The complex trans-[HFe(PNP)(dmpm)(CH(3)CN)]BPh(4), 3, (where PNP is Et(2)PCH(2)N(CH(3))CH(2)PEt(2) and dmpm is Me(2)PCH(2)PMe(2)) can be successively protonated in two steps using increasingly strong acids. Protonation with 1 equiv of p-cyanoanilinium tetrafluoroborate in acetone-d(6) at -80 degrees C results in ligand protonation and the formation of endo (4a) and exo (4b) isomers of trans-[HFe(PNHP)(dmpm)(CH(3)CN)](BPh(4))(2). The endo isomer undergoes rapid intramolecular proton/hydride exchange with an activation barrier of 12 kcal/mol. The exo isomer does not exchange. Studies of the reaction of 3 with a weaker acid (anisidinium tetrafluoroborate) in acetonitrile indicate that a rapid intermolecular proton exchange interconverts isomers 4a and 4b, and a pK(a) value of 12 was determined for these two isomers. Protonation of 3 with 2 equiv of triflic acid results in the protonation of both the PNP ligand and the metal hydride to form the dihydrogen complex [(H(2))Fe(PNHP)(dmpm)(CH(3)CN)](3+), 11. Studies of related complexes [HFe(PNP)(dmpm)(CO)](+) (12) and [HFe(depp)(dmpm)(CH(3)CN)](+) (10) (where depp is bis(diethylphosphino)propane) confirm the important roles of the pendant base and the ligand trans to the hydride ligand in the rapid intra- and intermolecular hydride/proton exchange reactions observed for 4. Features required for an effective proton relay and their potential relevance to the iron-only hydrogenase enzymes are discussed.     

Evidence for the formation of terminal hydrides by protonation of an asymmetric iron hydrogenase active site mimic

Treatment of [Fe2(mu-pdt)(CO)6] [pdt=S(CH2)3S] with dppe (Ph2PCH2CH2PPh2) in refluxing toluene affords the asymmetric complex [Fe2(mu-pdt)(CO)4(dppe)] (1). Protonation of 1 with HBF4-Et2O in CH2Cl2 gives at room temperature the mu-hydrido derivative [Fe2(mu-pdt)(CO)4(dppe)(mu-H)](BF4) (2). Monitoring the reaction by 1H, 31P, and 13C NMR at low temperature reveals unambiguously that the process of the protonation of 1 implies terminal hydride intermediates.     

Synthesis and structural investigation of N,N',N' '-trialkylguanidinato-supported zirconium(IV) complexes

The addition of 2 equiv of N,N',N' '-triisopropylguanidine (guanH(2)) to Zr(CH(2)Ph)(4) produced the bis(guanidinato)bis(benzyl)zirconium complex [((i)PrNH)C(N(i)Pr)(2)](2)Zr(CH(2)Ph)(2) (1). The mono(guanidinato) complex [((i)PrN)(2)C(NH(i)Pr)]ZrCl(3) (2) was accessible by the reaction of 2 equiv of guanH(2) with ZrCl(4). Guanidinium hydrochloride, [C(NH(i)Pr)(3)]Cl, is a byproduct of this reaction. When crystallized from THF, complex 2 was isolated as the THF adduct [((i)PrNH)C(N(i)Pr)(2)]ZrCl(3)(THF) (2-THF). The mixed cyclopentadienyl guanidinato complex [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrCl(2) (3) was prepared by treatment of [1,3-(Me(3)Si)(2)C(5)H(3)]ZrCl(3) with the in situ generated lithium triisopropylguanidinate salt. The reaction of guanH(2) with [1,3-(Me(3)Si)(2)C(5)H(3)]ZrMe(3) affords the dimethyl derivative [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrMe(2) (4). Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray characterization of 1, 2-THF, and 3, which are presented. The extent of pi delocalization within the guanidinato ligand is discussed in the context of the metrical parameters obtained from these structural studies.     

Synthesis of Polysiloxane-Bound (Ether-phosphine)palladium Complexes. Stoichiometric and Catalytic Reactions in Interphases(1)

The reaction of two equiv of the monomeric ether-phosphine O,P ligand (MeO)(3)Si(CH(2))(3)(Ph)PCH(2)-Do [1a(T(0)()), 1b(T(0)())] {Do = CH(2)OCH(3) [1a(T(0)())], CHCH(2)CH(2)CH(2)O [1b(T(0)())]} with PdCl(2)(COD) yields the monomeric palladium(II) complexes Cl(2)Pd(P approximately O)(2) [2a(T(0)())(2)(), 2b(T(0)())(2)()]. The compounds 2a(T(0)())(2)() and 2b(T(0)())(2)() are sol-gel processed with variable amounts (y) of Si(OEt)(4) (Q(0)()) to give the polysiloxane-bound complexes 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() (Table 1) {P approximately O = eta(1)-P-coordinated ether-phosphine ligand; for T(n)() and Q(k)(), y = number of condensed T type (three oxygen neighbors), Q type (four oxygen neighbors) silicon atoms; n and k = number of Si-O-Si bonds; n = 0-3; k = 0-4; 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() = {[M]-SiO(n)()(/2)(OX)(3)(-)(n)()}(2)[SiO(k)()(/2)(OX)(4)(-)(k)()](y)(), [M] = (Cl(2)Pd)(1/2)(Ph)P(CH(2)Do)(CH(2))(3)-, X = H, Me, Et}. The complexes 2b(T(n)())(2)()(Q(k)())(y)() (y = 4, 12, 36) show high activity and selectivity in the hydrogenation of 1-hexyne and tolan. The dicationic complexes [Pd(P&arcraise;O)(2)][SbF(6)](2) [3a(T(0)())(2)(), 3b(T(0)())(2)()] are formed by reacting Cl(2)Pd(P approximately O)(2) with 2 equiv of a silver salt {P&arcraise;O = eta(2)-O&arcraise;P-coordinated ether-phosphine ligand; 3a(T(0)())(2)(), 3b(T(0)())(2)() = [M]-SiOMe(3); [M] = {[Pd(2+)](1/)(2)P(Ph)(CH(2)CH(2)OCH(3))(CH(2))(3)-}{SbF(6)} (a), {[Pd(2+)](1/)(2)P(Ph)(CH(2)CHCH(2)CH(2)CH(2)O)(CH(2))(3)-}{SbF(6)} (b)}. Their polysiloxane-bound congeners 3a(T(n)())(2)(), 3b(T(n)())(2)() {[M]-SiO(n)()(/2)(OX)(3)(-)(n)} are obtained if a volatile, reversible bound ligand like acetonitrile is employed during the sol-gel process. The bis(chelate)palladium(II) complexes 3a(T(n)())(2)(), 3b(T(n)())(2)() are catalytic active in the solvent-free CO-ethene copolymerization, producing polyketones with chain lengths comparable to those obtained with chelating diphosphine ligands. The polysiloxane-bound palladium(0) complexes 5a(T(n)())(2)()(Q(k)())(4)(), 5b(T(n)())(2)()(Q(k)())(4)() {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)}(2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [(dba)Pd](1/)(2)P(Ph)(CH(2)Do)(CH(2))(3)-} undergo an oxidative addition reaction with iodobenzene in an interphase with formation of the complexes PhPd(I)(P approximately O)(2).4SiO(2) [6a(T(n)())(2)()(Q(k)())(4)(), 6b(T(n)())(2)()(Q(k)())(4)()] {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)](2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [PhPd(I)](1/2)P(Ph)(CH(2)Do)(CH(2))(3)-}, which insert carbon monoxide into the palladium-aryl bond even in the solid state.     

Coupling of an aldehyde or ketone to pyridine mediated by a tungsten imido complex

The reactivity of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2C6H4)(pic)2 (py=pyridine; pic=4-picoline) with unsaturated substrates has been investigated. Treatment of W(NPh)(o-(Me3SiN)2C6H4)(py)2 with diphenylacetylene or 2,3-dimethyl-1,3-butadiene generates W(NPh)(o-(Me3SiN)2C6H4)(eta2-PhCCPh) and W(NPh)(o-(Me3SiN)2C6H4)(eta4-CH2=C(Me)C(Me)=CH2), respectively, while the addition of ethylene to W(NPh)(o-(Me3SiN)2C6H4)(py)2 generates the known metallacycle W(NPh)(o-(Me3SiN)2C6H4)(CH2CH2CH2CH2). The addition of 2 equiv of acetone to W(NPh)(o-(Me3SiN)2C6H4)(pic)2 provides the azaoxymetallacycle W(NPh)(o-(Me3SiN)2C6H4)(OCH(Me)2)(OC(Me)2-o-C5H3N-p-Me), the result of acetone insertion into the ortho C-H bond of picoline. Similarily, the addition of 2 equiv of RC(O)H [R=Ph, tBu] to W(NPh)(o-(Me3SiN)2C6H4)(py)2 generates W(NPh)(o-(Me3SiN)2C6H4)(OCH2R)(OCHR-o-C5H4N) [R=Ph, tBu,]. In contrast, reaction between W(NPh)(o-(Me3SiN)2C6H4)(py)2 and 2-pyridine carboxaldehyde yields the diolate W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)CH(C5H4N)O). The synthesis of W(NPh)(o-(Me3SiN)2C6H4)(PMe3)(py)(eta2-OC(H)C6H4-p-Me), formed by the addition of p-tolualdehyde to a mixture of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and PMe3, suggests that an eta2-aldehyde intermediate is involved in the formation of the azaoxymetallacycle, while the isolation of W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)(CMe3)-o-C5H4N), formed by the reaction of pinacolone with W(NPh)(o-(Me3SiN)2C6H4)(py)2, in the presence of adventitious CH2Cl2, suggests that the reaction proceeds via the hydride W(NPh)(o-(Me3SiN)2C6H4)(H)(OC(Me)(CMe3)-o-C5H4N).     

Utilization of CS2 as a source of C1 synthetic units for the preparation of bis(alkylthio)methanes and alkyl dithioformates

Double insertion of CS2 into two Ru-H bonds of [(dppm)2Ru(H)2] (dppm = Ph2PCH2PPh2) affords the methanedithiolate complex [(dppm)2Ru(eta2-S2CH2)]. The methanedithiolate moiety has been functionalized using 2 equiv of RX resulting in bis(alkylthio)methane derivatives [(dppm)2Ru(RSCH2SR)][X]2. The bis(alkylthio)methane complex loses the bis(alkylthio)methane moiety under very mild conditions and in turn affords the [(dppm)2RuX2] complex from which the starting dihydride [(dppm)2Ru(H)2] has been regenerated via reaction with KOH/EtOH. On the other hand, insertion of CS2 into one Ru-H bond of [(dppe)2Ru(H)2] (dppe = Ph2PCH2CH2PPh2) followed by functionalization using RX results in alkyl dithioformate complex trans-[(dppe)2Ru(H)(SC(SR)H)][X]. In this case also, the alkyl dithioformate moiety gets eliminated under very mild conditions to afford the [(dppe)2Ru(H)(X)] derivative from which the starting dihydride has been regenerated via reaction with NaBH4. The reactions presented here constitute utilization of CS2 as a C1 synthetic source for the generation of useful organic compounds.     

Alkyl-eta2-alkene niobocene and tantalocene complexes with the allyldimethylsilyl-eta5-cyclopentadienyl ligand: synthesis, NMR studies and DFT calculations

Group 5 metal complexes [M(eta5-C5H5)[eta5-C5H4SiMe2(CH2-eta]2-CH=CH2)]X] (M = Nb, X = Me, CH2Ph, CH2SiMe3; M = Ta, X = Me, CH2Ph) and [Ta(eta5-C5Me5)[eta5-C5H4SiMe2(CH2-eta2-CH=CH2)]X] (X = Cl, Me, CH2Ph, CH2SiMe3) containing a chelating alkene ligand tethered to a cyclopentadienyl ring have been synthesized in high yields by reduction with Na/Hg (X = Cl) and alkylation with reductive elimination (X = alkyl) of the corresponding metal(iv) dichlorides [M(eta5-Cp)[eta5-C5H4SiMe2(CH2CH=CH2)]Cl2] (Cp = C5H5, M = Nb, Ta, Cp = C5Me5, M = Ta). These chloro- and alkyl-alkene coordinated complexes react with CO and isocyanides [CNtBu, CN(2,6-Me2C6H3)] to give the ligand-substituted metal(III) compounds [M(eta5-Cp)[eta5-C5H4SiMe2(CH2CH=CH2)]XL] (X = Cl, Me, CH2Ph, CH2SiMe3). Reaction of the chloro-alkene tantalum complex with LiNHtBu results in formation of the imido hydride derivative [Ta(eta5-C5Me5)[eta5-C5H4SiMe2(CH2CH=CH2)]H(NtBu)]. NMR studies for all of the new compounds and DFT calculations for the alkene-coordinated metal complexes are compared with those known for related group 4 metal cations.     

Reactions of the dirhenium(II) complex Re2Cl4(mu-dppm)2 with pyridinecarboxylic acids. Examples of bidentate O,O versus N,O coordination and tridentate O,N,O coordination and structural isomers that contain the pyridine-2,6-dicarboxylate ligand

Pyridine-2-carboxylic acid, pyridine-2,3-dicarboxylic acid, and pyridine-2,4-dicarboxylic acid or their [(Ph(3)P)(2)N](+) salts react with the triply bonded dirhenium(II) complex Re(2)Cl(4)(mu-dppm)(2) (dppm = Ph(2)PCH(2)PPh(2)) in refluxing ethanol to afford unsymmetrical substitution products of the type Re(2)(eta(2)-N,O)Cl(3)(mu-dppm)(2), where N,O represents a chelating pyridine-2-carboxylate ligand (N,O = O(2)C-2-C(5)H(4)N (1), O(2)C-2-C(5)H(3)N(-3-CO(2)Et) (3), or O(2)C-2-C(5)H(3)N(-4-CO(2)H) (4)). The carboxylate groups in the 3- and 4- positions are not bound to the metal centers; in the case of 3 this group undergoes esterification in the refluxing ethanol solvent. Structure determinations have shown that 1, 3, and 4 possess similar structures in which there is an axial Re-O (carboxylate) bond (collinear with the Re(triple bond)Re bond) and the mu-dppm ligands are bound in a trans,cis fashion to the two Re atoms which have the ligand atom arrangement [P(2)NOClReReCl(2)P(2)]. The tridentate dianionic pyridine-2,6-dicarboxylate ligand (dipic) reacts with Re(2)Cl(4)(mu-dppm)(2) in ethanol at room temperature to give a compound Re(2)(dipic)Cl(2)(mu-dppm)(2) (6) in which the dipic ligand is bound in a symmetrical eta(3)-(O,N,O) fashion to one Re atom, with the N atom in an axial position (collinear with the Re(triple bond)Re bond) and with preservation of the same trans,trans coordination of the mu-dppm ligands that is present in Re(2)Cl(4)(mu-dppm)(2). Under reflux conditions, this kinetic product isomerizes to the thermodynamically favored isomer 5 with an unsymmetrical structure in which the dipic ligand chelates to one Re atom (as in 1, 3, and 4) and uses its other carboxylate group to bridge to the second Re atom. The isomerization of 6 to 5, which also results in a change in the coordination of the pair of mu-dppm ligand to trans,cis, is believed to occur by a partial "merry-go-round" process, a mechanism that probably explains the structures of the thermodynamic products 1, 3, and 4. The reaction of Re(2)Cl(4)(mu-dppm)(2) with pyridine-3-carboxylate gives the trans isomer of Re(2)(mu:eta(2)-O(2)C-3-C(5)H(4)N)(2)Cl(2)(mu-dppm)(2) (2) in which a pair of carboxylate bridges are present and the pyridine N atom is not coordinated. Single-crystal X-ray structural details are reported for 1-6.     

Synthetic and structural studies of the coordination behavior of 2-pyridylbis(diphenylphosphino)methane

The coordination chemistry of the potentially semilabile tridentate ligand 2-pyridylbis(diphenylphosphino)methane (NPP) has been investigated. Bidentate (N, P) coordination occurs in CoCl(2)(NPP) (1) and [CdX(mu-X)(NPP)](2) (X = Cl (2); OAc (3)), prepared from the corresponding metal salts, in fac-Re(CO)(3)Br(NPP) (4) and in Fe(CO)(2)(MA)(NPP) (6). The last is one of three products from the reaction of Fe(CO)(4)(MA) (MA = maleic anhydride) with NPP, the other two being Fe(CO)(3)(NPP) (7; P, P coordinated) and the unusual cyclic ylid Ph2PC(2-C5H4N)PPh2C(CH2CO2H)C(=O)(5). The ligand shows tridentate coordination in Cr(CO)(3)(NPP) (9), RuCl(2)(PPh(3))(NPP) (10), and possibly in PtCl(2)(NPP) (8). Carbon monoxide displaces one phosphorus arm of the ligand in 10. Anhydrous NiCl(2) and NPP react in the presence of methanol to give NiCl(2)(P(OMe)Ph(2))(Ph(2)PCH(2)py) (12) in which the NPP ligand has been cleaved. This in turn reacts with O(2) to form trans-NiCl(2)(Ph(2)P(O)CH(2)py)(2) (13). The methine proton of NPP is transferred to the metal on reaction with Pt(C(2)H(4))(PPh(3))(2) and [Ir(COD)(NPP)]BF(4) to form the hydride complexes Pt(H)(PPh(3))(NPP-H) (14) and [Ir(H)(NPP)(NPP-H)]BF(4) (15). In 15 the intact NPP ligand is tridentate. The structures of 1 - 7 and 12 - 15 have been determined.