Thermodynamic hydride donor abilities of [HW(CO)4L]- complexes (L = PPh3, P(OMe)3, CO) and their reactions with [C5Me5Re(PMe3)(NO)(CO)]+

The thermodynamic hydride donor abilities of [HW(CO)(5)](-) (40 kcal/mol), [HW(CO)(4)P(OMe(3))](-) (37 kcal/mol), and [HW(CO)(4)(PPh(3))](-) (36 kcal/mol) have been measured in acetonitrile by either equilibrium or calorimetric methods. The hydride donor abilities of these complexes are compared with other complexes for which similar thermodynamic measurements have been made. [HW(CO)(5)](-), [HW(CO)(4)P(OMe(3))](-), and [HW(CO)(4)(PPh(3))](-) all react rapidly with [CpRe(PMe(3))(NO)(CO)](+) to form dinuclear intermediates with bridging formyl ligands. These intermediates slowly form [CpRe(PMe(3))(NO)(CHO)] and [W(CO)(4)(L)(CH(3)CN)]. The structure of cis-[HW(CO)(4)(PPh(3))](-) has been determined and has the expected octahedral structure. The hydride ligand bends away from the CO ligand trans to PPh(3) and toward PPh(3).     

B(C6F5)3 adducts of transition metal acyl compounds

The transition metal acyl compounds [Co(L)(CO)3(COMe)] (L = PMe3, PPhMe2, P(4-Me-C6H4)3, PPh3 and P(4-F-C6H4)3), [Mn(CO)5(COMe)] and [Mo(PPh3)(eta(5)-C5H5)(CO)2(COMe)] react with B(C6F5)3 to form the adducts [Co(L)(CO)3(C{OB(C6F5)3}Me)] (L = PMe3, 1, PPhMe2, 2, P(4-Me-C6H4)3, 3, PPh3, 4, P(4-F-C6H4)3), 5, [Mn(CO)5(C{OB(C6F5)3}Me)] 6 and [Mo(eta(5)-C5H5)(PPh3)(CO)2(C{OB(C6F5)3}Me)], 7. Addition of B(C6F5)3 to a cooled solution of [Mo(eta(5)-C5H5)(CO)3(Me)], under an atmosphere of CO gave [Mo(eta(5)-C5H5)(CO)3(C{OB(C6F5)3}Me)] 8. In the presence of adventitious water, the compound [Co{HOB(C6F5)3}2{OP(4-F-C6H4)3}2] 9, was formed from [Co(P(4-F-C6H4)3)(CO)3(C{OB(C6F5)3}Me)]. The compounds 4 and 9 have been structurally characterised. The use of B(C6F5)3 as a catalyst for the CO-induced migratory-insertion reaction in the transition metal alkyl compounds [Co(PPh3)(CO)3(Me)], [Mn(CO)5(Me)], [Mo(eta(5)-C5H5)(CO)3(Me)] and [Fe(eta(5)-C5H5)(CO)2(Me)] has been investigated.     

Mixed phosphine and group-13 metal ligator complexes [(PR3)(a)M(ECp*)b] (M = Mo, Ni; E = Ga, Al; R = C6H5, cyclo-C6H11, CH3)

Treatment of [Mo(N(2))(PMe(3))(5)] with two equivalents GaCp* (Cp* = η(5)-C(5)(CH(3))(5)) leads to the formation of cis-[Mo(GaCp*)(2)(PMe(3))(4)] (1), while AlCp* did not react with this precursor. In addition, [Ni(GaCp*)(2)(PPh(3))(2)] (2a), [Ni(AlCp*)(2)(PPh(3))(2)] (2b), [Ni(GaCp*)(2)(PCy(3))(2)] (3a), [Ni(GaCp*)(2)(PMe(3))(2)] (3b), [Ni(GaCp*)(3)(PCy(3))] (4) and [Ni(GaCp*)(PMe(3))(3)] (5) have been prepared in high yields by a direct synthesis from [Ni(COD)(2)] and stoichiometric amounts of the ligands PR(3) and ECp* (E = Al, Ga), respectively. All compounds have been fully characterized by (1)H, (13)C, and (31)P NMR spectroscopy, elemental analysis and single crystal X-ray diffraction studies.     

Trans --> cis isomerization of trans-[(dppm)2Ru(H)(L)][BF4] (L = P(OR)3) complexes: preparation of cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)(2)Ru(eta(2)-H(2))(L)][BF(4)](2) (dppm = Ph(2)PCH(2)PPh(2); L = P(OMe)(3), P(OEt)(3), PF(O(i)Pr)(2)) have been prepared by protonating the precursor hydride complexes cis-[(dppm)(2)Ru(H)(L)][BF(4)] (L = P(OMe)(3), P(OEt)(3), P(O(i)Pr)(3)) using HBF(4).Et(2)O. The cis-[(dppm)(2)Ru(H)(L)][BF(4)] complexes were obtained from the trans hydrides via an isomerization reaction that is acid-accelerated. This isomerization reaction gives mixtures of cis and trans hydride complexes, the ratios of which depend on the cone angles of the phosphite ligands: the greater the cone angle, the greater is the amount of the cis isomer. The eta(2)-H(2) ligand in the dihydrogen complexes is labile, and the loss of H(2) was found to be reversible. The protonation reactions of the starting hydrides with trans PMe(3) or PMe(2)Ph yield mixtures of the cis and the trans hydride complexes; further addition of the acid, however, give trans-[(dppm)(2)Ru(BF(4))Cl]. The roles of the bite angles of the dppm ligand as well as the steric and the electronic properties of the monodentate phosphorus ligands in this series of complexes are discussed. X-ray crystal structures of trans-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], cis-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], and cis-[(dppm)(2)Ru(H)(P(O(i)Pr)(3))][BF(4)] complexes have been determined.     

Coordination chemistry of 4-methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane: preparation and characterization of Ru(II) complexes

The complexes TpRu[P(OCH(2))(2)(OCCH(3)](PPh(3))Cl (2) [Tp = hydridotris(pyrazolyl)borate; P(OCH(2))(2)(OCCH(3)) (1) = (4-methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane] and TpRu(L)(PPh(3))Cl [L = P(OCH(2))(3)CEt (3), PMe(3) (4) or P(OMe)(3) (5)], (η(6)-C(6)H(6))Ru(L)Cl(2) [L = PPh(3) (6), P(OMe)(3) (7), PMe(3) (8), P(OCH(2))(3)CEt (9), CO (10) or P(OCH(2))(2)(OCCH(3)) (11)] and (η(6)-p-cymene)Ru(L)Cl(2) [L = P(OCH(2))(3)CEt (12), P(OCH(2))(2)(OCCH(3))P(OCH(2))(2)(OCCH(3)) (13), P(OMe)(3) (14) or PPh(3) (15)] have been synthesized, isolated, and characterized by NMR spectroscopy, cyclic voltammetry, mass spectrometry, and, for some complexes, single crystal X-ray diffraction. Data from cyclic voltammetry and solid-state structures have been used to compare the properties of (1) with other phosphorus-based ligands as well as carbon monoxide. Data from the solid-state structures of Ru(II) complexes show that P(OCH(2))(2)(OCCH(3)) has a cone angle of 104°. Cyclic voltammetry data reveal that the Ru(II) complexes bearing P(OCH(2))(2)(OCCH(3)) have more positive Ru(III/II) redox potentials than analogous complexes with the other phosphorus ligands; however, the Ru(III/II) potential for (η(6)-C(6)H(6))Ru[P(OCH(2))(2)(OCCH(3))]Cl(2) is more negative compared to the Ru(III/II) potential for the CO complex (η(6)-C(6)H(6))Ru(CO)Cl(2). For the Ru(II) complexes studied herein, these data are consistent with the overall donor ability of 1 being less than other common phosphines (e.g., PMe(3) or PPh(3)) or phosphites [e.g., P(OCH(2))(3)CEt or P(OMe)(3)] but greater than carbon monoxide.     

Effects of Cyclopentadienyl and Phosphine Ligands on the Basicities and Nucleophilicities of Cp'Ir(CO)(PR(3)) Complexes

Basicities of the series of complexes CpIr(CO)(PR(3)) [PR(3) = P(p-C(6)H(4)CF(3))(3), P(p-C(6)H(4)F)(3), P(p-C(6)H(4)Cl)(3), PPh(3), P(p-C(6)H(4)CH(3))(3), P(p-C(6)H(4)OCH(3))(3), PPh(2)Me, PPhMe(2), PMe(3), PEt(3), PCy(3)] have been measured by the heat evolved (DeltaH(HM)) when the complex is protonated by CF(3)SO(3)H in 1,2-dichloroethane (DCE) at 25.0 degrees C. The -DeltaH(HM) values range from 28.0 kcal/mol for CpIr(CO)[P(p-C(6)H(4)CF(3))(3)] to 33.2 kcal/mol for CpIr(CO)(PMe(3)) and are directly related to the basicities of the PR(3) ligands in the complexes. For the more basic pentamethylcyclopentadienyl analogs, the -DeltaH(HM) values range from 33.8 kcal/mol for the weakest base CpIr(CO)[P(p-C(6)H(4)CF(3))(3)] to 38.0 kcal/mol for the strongest CpIr(CO)(PMe(3)). The nucleophilicities of the Cp'Ir(CO)(PR(3)) complexes were established from second-order rate constants (k) for their reactions with CH(3)I to give [Cp'Ir(CO)(PR(3))(CH(3))](+)I(-) in CD(2)Cl(2) at 25.0 degrees C. There is an excellent linear correlation between the basicities (DeltaH(HM)) and nucleophilicities (log k) of the CpIr(CO)(PR(3)) complexes. Only the complex CpIr(CO)(PCy(3)) with the bulky tricyclohexylphosphine ligand deviates dramatically from the trend. In general, the pentamethylcyclopentadienyl complexes react 40 times faster than the cyclopentadienyl analogs. However, they do not react as fast as predicted from electronic properties of the complexes, which suggests that the steric size of the Cp ligand reduces the nucleophilicities of the CpIr(CO)(PR(3)) complexes. In addition, heats of protonation (DeltaH(HP)) of tris(2-methoxyphenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, and tris(2,4,6-trimethylphenyl)phosphine were measured and used to estimate pK(a) values for these highly basic phosphines.     

Synthesis and characterisation of triselenocarbonate [CSe3]2- complexes

[Pt(CSe3)(PR3)2] (PR3= PMe3, PMe2Ph, PPh3, P(p-tol)3, 1/2 dppp, 1/2 dppf) were all obtained by the reaction of the appropriate metal halide containing complex with carbon diselenide in liquid ammonia. Similar reaction with [Pt(Cl)2(dppe)] gave a mixture of triselenocarbonate and perselenocarbonate complexes. [{Pt(mu-CSe3)(PEt3)}4] was formed when the analogous procedure was carried out using [Pt(Cl)2(PEt3)2]. Further reaction of [Pt(CSe3)(PMe2Ph)2] with [M(CO)6] (M = Cr, W, Mo) yielded bimetallic species of the type [Pt(PMe2Ph)2(CSe3)M(CO)5] (M = Cr, W, Mo). The dimeric triselenocarbonate complexes [M{(CSe3)(eta5-C5Me5)}2] (M = Rh, Ir) and [{M(CSe3)(eta6-p-MeC6H4(i)Pr)}2] (M = Ru, Os) have been synthesised from the appropriate transition metal dimer starting material. The triselenocarbonate ligand is Se,Se' bidentate in the monomeric complexes. In the tetrameric structure the exocyclic selenium atoms link the four platinum centres together.     

Ruthenium(II) complexes containing bis(2-(diphenylphosphino)phenyl) ether and their catalytic activity in hydrogenation reactions

The half-sandwich complexes [(eta5-C5H5)RuCl(DPEphos)] (1) and [{(eta6-p-cymene)RuCl2}2(mu-DPEphos)] (2) were synthesized by the reaction of bis(2-(diphenylphosphino)phenyl) ether (DPEphos) with a mixture of ruthenium trichloride trihydrate and cyclopentadiene and with [(eta6-p-cymene)RuCl2]2, respectively. Treatment of DPEphos with cis-[RuCl2(dmso)4] afforded fac-[RuCl2(kappa3-P,O,P-DPEphos)(dmso)] (3). The dmso ligand in 3 can be substituted by pyridine, 2,2'-bipyridine, 4,4'-bipyridine, and PPh3 to yield trans,cis-[RuCl2(DPEphos)(C5H5N)2] (4), cis,cis-[RuCl2(DPEphos)(2,2'-bipyridine)] (5), trans,cis-[RuCl2(DPEphos)(mu-4,4'-bipyridine)]n (6), and mer,trans-[RuCl2(kappa3-P,P,O-DPEphos)(PPh3)] (7), respectively. Refluxing [(eta6-p-cymene)RuCl2]2 with DPEphos in moist acetonitrile leads to the elimination of the p-cymene group and the formation of the octahedral complex cis,cis-[RuCl2(DPEphos)(H2O)(CH3CN)] (8). The structures of the complexes 1-5, 7, and 8 are confirmed by X-ray crystallography. The catalytic activity of these complexes for the hydrogenation of styrene is studied.     

Octahedral Ru(II) amido complexes TpRu(L)(L')(NHR) (Tp = hydridotris(pyrazolyl)borate; L = L' = P(OMe)3 or PMe3 or L = CO and L' = PPh3; R = H,Ph, or tBu): synthesis,characterization, and reactions with weakly acidic C-H bonds

The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH(2)R)][OTf] (L = L' = PMe(3), P(OMe)(3) or L = CO and L' = PPh(3); R = H or (t)Bu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH(3))][OTf] or [TpRu(PMe(3))(2)(NH(2)(t)Bu)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH(2)) and TpRu(PMe(3))(2)(NH(t)Bu). Reactions of the parent amido complexes or TpRu(PMe(3))(2)(NH(t)Bu) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe(3))(2)(C[triple bond]CPh) in >90% yield. The observation that [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH(3))][PhC(2)] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe(3))(2)(NH(2)R)][OTf] (R = H or (t)Bu) with acetonitrile. The previously reported phenyl amido complexes TpRuL(2)(NHPh) [L = PMe(3) or P(OMe)(3)] react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(C[triple bond]CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe(3))(2)(NHPh) with phenylacetylene occurs via a pathway that involves TpRu(PMe(3))(2)(OTf) or [TpRu(PMe(3))(2)(NH(2)Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L)(L')(NH(2)) (L = L' = PMe(3) or L = CO and L' = PPh(3)) or TpRu(PMe(3))(2)(NH(t)Bu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe(3))(2)(H), [Tp(PMe(3))(2)Ru[double bond]C[double bond]C(H)Ph][OTf], [Tp(PMe(3))(2)Ru=C(CH(2)Ph)[N(H)Ph]][OTf], and [TpRu(PMe(3))(3)][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh(3))(NH(3))][OTf], [TpRu(PMe(3))(2)(NH(3))][OTf], and TpRu(CO)(PPh(3))(C[triple bond]CPh) are reported.     

Electron-rich diferrous-phosphane-thiolates relevant to Fe-only hydrogenase: is cyanide "nature's trimethylphosphane"?

The two-step one-pot oxidative decarbonylation of [Fe2(S2C2H4)(CO)4(PMe3)2] (1) with [FeCp2]PF6, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2-6, containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1(2+) as the initial intermediate of the oxidation of 1, even when a deficiency of the oxidant was employed. Subsequent addition of PR3 gave rise to [Fe2(S2C2H4)(mu-CO)(CO)3(PMe3)3]2+ (2) and [Fe2(S2C2H4)(mu-CO)(CO)2(PMe3)2(PR3)2]2+ (R = Me 3, OMe 4) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe2(S2C2H4)(mu-CO)(CO)2(PMe3)3(MeCN)]2+ (5) and [Fe2(S2C2H4)(mu-CO)(CO)(PMe3)4(MeCN)]2+ (6) were fully characterized. Relevant to the H(red) state of the active site of Fe-only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.     

ortho-Metallated complexes of platinum(II) and diplatinum(I) containing the carbanions (2-diphenylphosphino)phenyl and (2-diphenylphosphino)-n-tolyl (n = 5, 6)

When the ortho-metallated complexes cis-[Pt(kappa(2)-C6H3-5-R-2-PPh2)2] (R = H 1, Me 2) are either heated in toluene or treated with CO at room temperature, one of the four-membered chelate rings is opened irreversibly to give dinuclear isomers [Pt2(kappa(2)-C6H3-5-R-2-PPh2)2(mu-C6H3-5-R-2-PPh2)2] (R = H 10, Me 11). A single-crystal X-ray diffraction study shows the Pt...Pt separation in 10 to be 3.3875(4) A. By-products of the reactions of 1 and 2 with CO are polymeric isomers (R = H 13, Me 14) in which one of the P-C ligands is believed to bridge adjacent platinum atoms intermolecularly. In contrast to the behaviour of 1 and 2, when cis-[Pt(kappa(2)-C6H3-6-Me-2-PPh2)2] (cis-3) is heated in toluene, the main product is trans-3, and reaction of cis-3 with CO gives a carbonyl complex [Pt(CO)(kappa(1)-C-C6H3-6-Me-2-PPh2)(2-C6H3-6-Me-2-PPh2)] 15, in which one of the carbanions is coordinated only through the carbon. Formation of a dimer analogous to 10 or 11 is sterically hindered by the 6-methyl substituent. Comproportionation of 1 or 2 with [Pt(PPh3)2L] (L = PPh3, C2H4) gives diplatinum(I) complexes [Pt2(mu-C6H3-5-R-2-PPh2)2(PPh3)2] (R = H 16, Me 17). An X-ray diffraction study shows that 17 contains a pair of planar-coordinated metal atoms separated by 2.61762(16) A. There is no evidence for the formation of an analogue containing mu-C6H3-6-Me-2-PPh2. The axial PPh3 ligands of 16 are readily replaced by ButNC giving [Pt2(mu-2-C6H4PPh2)2(CNBut)2] 18, which is protonated by HBF4 to form a mu-hydridodiplatinum(II) salt [Pt2(mu-H)(mu-2-C6H4PPh2)2(CNBut)2]BF4 [21]BF4. The J(PtPt) values in [21]BF4 and 18, 2700 Hz and 4421 Hz, respectively, reflect the weakening of the Pt-Pt interaction caused by protonation. Similarly, 16 and 17 react with the electrophiles iodine and strong acids to give salts of general formula [Pt2(mu-Z)(mu-C6H3-5-R-2-PPh2)2(PPh3)2]Y (Y = Z = I, R = H 19+, Me 20+; Z = H, Y = BF4, PF6, OTf, R = H 22+; Z = H, Y = PF6, R = Me 23+). A single-crystal X-ray diffraction study of [23]PF6 shows that the cation has an approximately A-frame geometry, with a Pt-Pt separation of 2.7888(3) A and a Pt-H bond length of 1.62(1) A, and that the 5-methyl substituents have undergone partial exchange with the 4-hydrogen atoms of the PPh2 groups of the bridging carbanion. The latter observation indicates that the added proton of [23]+ undergoes a reversible reductive elimination-oxidative addition sequence with the Pt-C(aryl) bonds.     

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).     

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.     

Electronic structures of ruthenium and osmium complexes of 9,10-phenanthrenequinone

The reaction of 9,10-phenanthrenequinone (PQ) with [M(II)(H)(CO)(X)(PPh(3))(3)] in boiling toluene leads to the homolytic cleavage of the M(II)-H bond, affording the paramagnetic trans-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2·toluene, and 4·CH(2)Cl(2), EPR spectra, and density functional theory (DFT) calculations have substantiated that 1-4 are 9,10-phenanthrenesemiquinone radical (PQ(?-)) complexes of ruthenium(II) and osmium(II) and are defined as trans-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (1), cis-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (2), trans-[Os(II)(PQ(?-))(PPh(3))(2)(CO) Br] (3), and cis-[Os(II)(PQ(?-))(PPh(3))(2)(CO)Br] (4). Two comparatively longer C-O [average lengths: 1, 1.291(3) ?; 2·toluene, 1.281(5) ?; 4·CH(2)Cl(2), 1.300(8) ?] and shorter C-C lengths [1, 1.418(5) ?; 2·toluene, 1.439(6) ?; 4·CH(2)Cl(2), 1.434(9) ?] of the OO chelates are consistent with the presence of a reduced PQ(?-) ligand in 1-4. A minor contribution of the alternate resonance form, trans- or cis-[M(I)(PQ)(PPh(3))(2)(CO)X], of 1-4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe(3))(2)(CO)Cl] (5), cis-[Ru(PQ)(PMe(3))(2)(CO)Cl] (6), and cis-[Os(PQ)(PMe(3))(2)(CO)Br] (7). However, no thermodynamic equilibria between [M(II)(PQ(?-))(PPh(3))(2)(CO)X] and [M(I)(PQ)(PPh(3))(2)(CO)X] tautomers have been detected. 1-4 undergo one-electron oxidation at -0.06, -0.05, 0.03, and -0.03 V versus a ferrocenium/ferrocene, Fc(+)/Fc, couple because of the formation of PQ complexes as trans-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (1(+)), cis-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (2(+)), trans-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (3(+)), and cis-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (4(+)). The trans isomers 1 and 3 also undergo one-electron reduction at -1.11 and -0.96 V, forming PQ(2-) complexes trans-[Ru(II)(PQ(2-))(PPh(3))(2)(CO)Cl](-) (1(-)) and trans-[Os(II)(PQ(2-))(PPh(3))(2)(CO)Br](-) (3(-)). Oxidation of 1 by I(2) affords diamagnetic 1(+)I(3)(-) in low yields. Bond parameters of 1(+)I(3)(-) [C-O, 1.256(3) and 1.258(3) ?; C-C, 1.482(3) ?] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV-vis/near-IR absorption features of 1-4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5(+), and 5(-).     

Synthesis of acetimino complexes of Pt(II) and Pt(IV) and the first heteronuclear mu-acetimido complexes

The reactions of [Ag(NH=CMe2)2]ClO4 with cis-[PtCl2L2] in a 1:1 molar ratio give cis-[PtCl(NH=CMe2)(PPh3)2]ClO4 (1cis) or cis-[PtCl(NH=CMe2)2(dmso)]ClO4 (2), and in 2:1 molar ratio, they produce [Pt(NH=CMe2)2L2](ClO4)2 [L = PPh3 (3), L2= tbbpy = 4,4'-di-tert-butyl-2,2'-dipyridyl (4)]. Complex 2 reacts with PPh3 (1:2) to give trans-[PtCl(NH=CMe2)(PPh3)2]ClO(4) (1trans). The two-step reaction of cis-[PtCl2(dmso)2], [Au(NH=CMe2)(PPh3)]ClO4, and PPh3 (1:1:1) gives [SP-4-3]-[PtCl(NH=CMe2)(dmso)(PPh3)]ClO4 (5). The reactions of complexes 2 and 4 with PhICl2 give the Pt(IV) derivatives [OC-6-13]-[PtCl3(NH=CMe2)(2)(dmso)]ClO4 (6) and [OC-6-13]-[PtCl2(NH=CMe2)2(dtbbpy)](ClO4)2 (7), respectively. Complexes 1cis and 1trans react with NaH and [AuCl(PPh3)] (1:10:1.2) to give cis- and trans-[PtCl{mu-N(AuPPh3)=CMe2}(PPh3)2]ClO4 (8cis and 8trans), respectively. The crystal structures of 4.0.5Et2O.0.5Me2CO and 6 have been determined; both exhibit pseudosymmetry.     

Synthesis, structure and DFT study of dinuclear iron, cobalt and nickel complexes with cyclopentadienyl-metal moieties

Reactions of 1,1'-bis(dipheny1phosphino)cobaltocene with Co(PMe(3))(4), Ni(PMe(3))(4), Fe(PMe(3))(4), Ni(COD)(2), FeMe(2)(PMe(3))(4) or NiMe(2)(PMe(3))(3) afford a series of novel dinuclear complexes [((Me(3)P)[lower bond 1 start]Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)M[upper bond 1 end](η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (M = Co(1), Ni(2) and Fe(3)) [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](COD)](4), [Co(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)Ni[upper bond 1 end](PMe(3))(2)] (5) and [((Me(3)P)[lower bond 1 start]Co(Me)(η(5)-C(5)H(4)[upper bond 1 start]PPh(2)))((Me(3)P)Fe[upper bond 1 end](Me)(η(5)-C(5)H(4)P[lower bond 1 end]Ph(2)))] (6). Reactions of 1,1'-bis(dipheny1phosphino)ferrocene with Ni(PMe(3))(4), NiMe(2)(PMe(3))(3), or Co(PMe(3))(4) gives rise to complexes [Fe(η(5)-C(5)H(4)[upper bond 1 start]PPh(2))(2)M[upper bond 1 end](PMe(3))(2)] (M = Ni (7), Co (8)). The complexes 1-8 were spectroscopically investigated and studied by X-ray single crystal diffraction. The possible reaction mechanisms and structural characteristics are discussed. Density functional theory (DFT) calculations strongly support the deductions.     

Generation and reactions of ruthenium phosphido complexes [(eta5-C5H5)Ru(PR'3)2(PR2)]: remarkably high phosphorus basicities and applications as ligands for palladium-catalyzed Suzuki cross-coupling reactions

Reactions of [(eta5-C5H5)Ru(PR'3)2(Cl)] with NaBAr(F) [BAr(F)-=B{3,5-[C6H3(CF3)2]}4-; PR'3=PEt3 or 1/2Et2PCH2CH2PEt2) (depe)] and PR2H (R=Ph, a; tBu, b; Cy, c) in C6H5F, or of related cationic Ru(N2) complexes with PR2H in C6H5F, gave the secondary phosphine complexes [(eta5-C5H5)Ru(PR'3)2(PR2H)]+ BAr(F)- (PR'3=PEt3, 3 a-c; 1/2depe, 4 a,b) in 65-91 % yields. Additions of tBuOK (3 a, 4 a; [D6]acetone) or NaN(SiMe3)2 (3 b,c, 4 b; [D8]THF) gave the title complexes [(eta5-C5H5)Ru(PEt3)2(PR2)] (5 a-c) and [(eta5-C5H5)Ru(depe)(PR2)] (6 a,b) in high spectroscopic yields. These complexes were rapidly oxidized in air; with 5 a, [(eta5-C5H5)Ru(PEt3)2{P(=O)Ph2}] was isolated (>99 %). The reaction of 5 a and elemental selenium yielded [(eta5-C5H5)Ru(PEt3)2{P(=Se)Ph2}] (70 %); selenides from 5 c and 6 a were characterized in situ. Competitive deprotonation reactions showed that 5 a is more basic than the rhenium analog [(eta5-C5H5)Re(NO)(PPh3)(PPh2)], and that 6 b is more basic than PtBu3 and P(iPrNCH2CH2)3N. The latter is one of the most basic trivalent phosphorus compounds [pK(a)(acetonitrile) 33.6]. Complexes 5 a-c and 6 b are effective ligands for Pd(OAc)2-catalyzed Suzuki coupling reactions: 6 b gave a catalyst nearly as active as the benchmark organophosphine PtBu3; 5 a, with a less bulky and electron-rich PR2 moiety, gave a less active catalyst. The reaction of 5 a and [(eta3-C3H5)Pd(NCPh)2]+ BF4- gave the bridging phosphido complex [(eta5-C5H5)Ru(PEt3)2(PPh2)Pd(NCPh)(eta3-C3H5)]+ BAr(F)- in approximately 90 % purity. The crystal structure of 4 a is described, as well as substitution reactions of 3 b and 4 b.     

New chiral ruthenium(II) catalysts containing 2,6-bis(4'-(R)-phenyloxazolin-2'-yl)pyridine (Ph-pybox) ligands for highly enantioselective transfer hydrogenation of ketones

Treatment of complex trans-[RuCl(2)(eta(2)-C(2)H(4))[kappa(3)-N,N,N-(R,R)-Ph-pybox]] [(R,R)-Ph-pybox = 2,6-bis[4'-(R)-phenyloxazolin-2'-yl]pyridine] with phosphines or phosphites in dichloromethane at 50 degrees C leads to the formation of novel ruthenium(II)-pybox complexes trans-[RuCl(2)(L)[kappa(3)-N,N,N-(R,R)-Ph-pybox]] [L = PPh(3) (1 a), PPh(2)Me (2 a), PPh(2)(C(3)H(5)) (3 a), PPh(2)(C(4)H(7)) (4 a), PMe(3) (5 a), PiPr(3) (6 a), P(OMe)(3) (7 a) and P(OPh)(3) (8 a)]. Likewise, reaction of trans-[RuCl(2)(eta(2)-C(2)H(4))[kappa(3)-N,N,N-(R,R)-Ph-pybox]] with PPh(3) or PiPr(3) in refluxing methanol leads to the complexes cis-[RuCl(2)(L)(kappa(3)-N,N,N-(R,R)-Ph-pybox] [L = PPh(3) (1 b), PiPr(3) (6 b)]. No trans-cis isomerisation of complexes 1 a-8 a has been observed. Complexes 1 a-8 a, 1 b, 6 b together with the analogous trans-[RuCl(2)[P(OMe)(3)][kappa(3)-N,N,N-(S,S)-iPr-pybox]] (10 a) and the previously reported trans- and cis-[RuCl(2)(PPh(3))[kappa(3)-N,N,N-(S,S)-iPr-pybox]] (9 a and 9 b, respectively) are active catalysts for the transfer hydrogenation of acetophenone in 2-propanol in the presence of NaOH (ketone/cat/NaOH 500:1:6). cis-Ph-pybox derivatives are the most active catalysts. In particular, cis complexes 1 b and 6 b led to almost quantitative conversions in less than 5 min with a high enantioselectivity (up to 95 %). A variety of aromatic ketones have also been reduced to the corresponding secondary alcohols with very high TOF and ee up to 94 %. The overall catalytic performance seems to be a subtle combination of the steric and/or electronic properties both the phosphines and the ketones. A high TOF (27 300 h(-1)) and excellent ee (94 %) have been found for the reduction of 3-bromoacetophenone with catalyst 6 b. Reductions of alkyl ketones also proceed with high and rapid conversions but low enantioselectivities are achieved.     

Cycloheptatrienyl zirconium sandwich complexes with lewis basic phospholyl ligands (phosphatrozircenes): synthesis, structure, bonding and coordination chemistry

The transmetalation reaction between [(η(7) -C(7) H(7) )ZrCl(tmeda)] (1; tmeda=N,N,N',N'-tetramethylethylenediamine) and various phospholide anions leads to a new class of mixed sandwich complexes: [(η(7)-C(7)H(7))Zr(η(5)-C(4)PMe(4))] (2), [(η(7)-C(7)H(7))Zr(η(5)-C(4)PH(2)Me(2))] (3) and [(η(7)-C(7)H(7))Zr(η(5)-C(4)PPhHMe(2))] (4). The presence of Lewis basic phosphorus atoms and Lewis acidic zirconium atoms allows ambiphilic behaviour to be observed, and X-ray diffraction analysis reveals dimeric arrangements for 2 and 3 with long intermolecular Zr-P bonds, whereas 4 remains monomeric in the solid state. DFT calculations indicate that the metal-phosphorus interaction is weak, and accordingly, complexes 2-4 act as monodentate ligands upon reaction with [W(CO)(5)(thf)]. The resulting complexes [W(CO)(5)(L)] 5-7 (L=2-4) were studied by IR spectroscopy and compared with the [W(CO)(5) ] complex 9, containing the phosphane-functionalised trozircene [(η(7)-C(7)H(7))Zr(η(5)-C(5)H(4)PPh(2))] (8). They all show a close resemblance to simple phosphanes, such as PMe(3) , although molecular orbital analysis of 2 reveals that the free electron pair in the phosphatrozircenes is not the HOMO. Four equivalents of 2 can replace 1,4-cyclooctadiene (COD) in [Ni(cod)(2)] to form the homoleptic, distorted tetrahedral complex [Ni{2}(4)] (10).     

Reaction of nido-7,8-C(2)B(9)H(13) with Dicobalt Octacarbonyl: Crystal Structures of the Complexes [Co(2)(CO)(2)(eta(5)-7,8-C(2)B(9)H(11))(2)], [Co(2)(CO)(PMe(2)Ph)(eta(5)-7,8-C(2)B(9)H(11))(2)], and [CoCl(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))

The compounds [Co(2)(CO)(8)] and nido-7,8-C(2)B(9)H(13) react in CH(2)Cl(2) to give a complex mixture of products consisting primarily of two isomers of the dicobalt species [Co(2)(CO)(2)(eta(5)-7,8-C(2)B(9)H(11))(2)] (1), together with small amounts of a mononuclear cobalt compound [Co(CO)(2)(eta(5)-10-CO-7,8-C(2)B(9)H(10))] (5) and a charge-compensated carborane nido-9-CO-7,8-C(2)B(9)H(11) (6). In solution, isomers 1a and 1b slowly equilibrate. However, column chromatography allows a clean separation of 1a from the mixture, and a single-crystal X-ray diffraction study revealed that each metal atom is ligated by a terminal CO molecule and in a pentahapto manner by a nido-C(2)B(9)H(11) cage framework. The two Co(CO)(eta(5)-7,8-C(2)B(9)H(11)) units are linked by a Co-Co bond [2.503(2) ?], which is supported by two three-center two-electron B-H right harpoon-up Co bonds. The latter employ B-H vertices in each cage which lie in alpha-sites with respect to the carbons in the CCBBB rings bonded to cobalt. Addition of PMe(2)Ph to a CH(2)Cl(2) solution of a mixture of the isomers 1, enriched in 1b, gave isomers of formulation [Co(2)(CO)(PMe(2)Ph)(eta(5)-7,8-C(2)B(9)H(11))(2)] (2). Crystals of one isomer were suitable for X-ray diffraction. The molecule 2a has a structure similar to that of 1a but differs in that whereas one B-H right harpoon-up Co bridge involves a boron atom in an alpha-site of a CCBBB ring coordinated to cobalt, the other uses a boron atom in the beta-site. Reaction between 1b and an excess of PMe(2)Ph in CH(2)Cl(2) gave the complex [CoCl(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))] (3), the structure of which was established by X-ray diffraction. Experiments indicated that 3 was formed through a paramagnetic Co(II) species of formulation [Co(PMe(2)Ph)(2)(eta(5)-7,8-C(2)B(9)H(11))]. Addition of 2 molar equiv of CNBu(t) to solutions of either 1a or 1b gave a mixture of two isomers of the complex [Co(2)(CNBu(t))(2)(eta(5)-7,8-C(2)B(9)H(11))(2)] (4). NMR data for the new compounds are reported and discussed.