Cationic Rh complexes with novel spiro tetraarylpentaborate anions prepared from arylboronic acids and aryloxorhodium complexes

Ar-B(OH)2 (1a: Ar = C6H4OMe-4, 1b: Ar = C6H3Me2-2,6) react immediately with Rh(OC6H4Me-4)(PMe3)3 (2) in 5 : 1 molar ratio at room temperature to generate [Rh(PMe3)4]+[B5O6Ar4]- (3a: Ar = C6H4OMe-4, 3b: Ar = C6H3Me2-2,6). p-Cresol (92%/Rh), anisole (80%/Rh) and H2O (364%/Rh) are formed from 1a and 2. The reaction of 1a with 2 for 24 h produces [Rh(PMe3)4]+[B5O6(OH)4]- (4) as a yellow solid. This is attributed to hydrolytic dearylation of once formed 3a because the direct reaction of 3a with excess H2O forms 4. An equimolar reaction of 2 with phenylboroxine (PhBO)3 causes transfer of the 4-methylphenoxo ligand from rhodium to boron to produce [Rh(PMe3)4]+[B3O3Ph3(OC6H4Me-4)]- (5). Arylboronic acids 1a and 1b react with Rh(OC6H4Me-4)(PR3)3 (6: R = Et, 8: R = Ph) and with Rh(OC6H4Me-4)(cod)(PR3) (11: R = iPr, 12: R = Ph) to form [Rh(PR3)4]+[B5O6Ar4]- (7a: R = Et, Ar = C6H4OMe-4, 7b: R = Et, Ar = C6H3Me2-2,6, 9a: R = Ph, Ar = C6H3Me2-2,6) and [Rh(cod)(PR3)(L)]+[B5O6Ar4]- (13b: R = iPr, L = acetone, Ar = C6H3Me2-2,6, 14a: R = Ph, L = PPh3, Ar = C6H4OMe-4, 14b: R = Ph, L = PPh3, Ar = C6H3Me2-2,6), respectively. Hydrolysis of 14a yields [Rh(cod)(PPh3)2]+[B5O6(OH)4]- (15) quantitatively.     

Synthons for coordinatively unsaturated complexes of tungsten, and their use for the synthesis of high oxidation-state silylene complexes

Reduction of Cp*WCl4 afforded the metalated complex (eta6-C5Me4CH2)(dmpe)W(H)Cl (1) (Cp* = C5Me5, dmpe = 1,2-bis(dimethylphosphino)ethane). Reactions with CO and H(2) suggested that 1 is in equilibrium with the 16-electron species [Cp(dmpe)WCl], and 1 was also shown to react with silanes R2SiH2 (R2 = Ph2 and PhMe) to give the tungsten(IV) silyl complexes Cp*(dmpe)(H)(Cl)W(SiHR2) (6a, R2 = Ph2; 6b, R2 = PhMe). Abstraction of the chloride ligand in 1 with LiB(C6F5)4 gave a reactive species that features a doubly metalated Cp ligand, [(eta7-C5Me3(CH2)2)(dmpe)W(H)2][B(C6F5)4] (4). In its reaction with dinitrogen, 4 behaves as a synthon for the 14-electron fragment [Cp*(dmpe)W]+, to give the dinuclear dinitrogen complex ([Cp*(dmpe)W]2(micro-N2)) [B(C6F5)4]2 (5). Hydrosilanes R2SiH2 (R2 = Ph2, PhMe, Me2, Dipp(H); Dipp = 2,6-diisopropylphenyl) were shown to react with 4 in double Si-H bond activation reactions to give the silylene complexes [Cp*(dmpe)H2W = SiR2][B(C6F5)4] (8a-d). Compounds 8a,b (R2 = Ph2 and PhMe, respectively) were also synthesized by abstraction of the chloride ligands from silyl complexes 6a,b. Dimethylsilylene complex 8c was found to react with chloroalkanes RCl (R = Me, Et) to liberate trialkylchlorosilanes RMe2SiCl. This reaction is discussed in the context of its relevance to the mechanism of the direct synthesis for the industrial production of alkylchlorosilanes.     

Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.     

Cycloaromatization Reaction of 4‐Alkoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,6‐Diaminotoluene: The Unexpected Regioselective Synthesis of 2,4,7,8‐Tetrasubstituted Quinolines

This article reports a convenient and general method for the regioselective synthesis of a new series of 2‐alkyl(aryl)‐8‐methyl‐4‐trifluoromethyl‐7‐aminoquinolines in 86–93% yields, from cycloaromatization reactions of N‐(oxotrifluoroalkenyl)‐2,6‐diaminotoluenes in a strongly acidic medium polyphosphoric acid and absence of solvent. The enaminoketone intermediates were easily isolated from the reaction of 4‐alkoxy‐4‐alkyl(aryl)‐1,1,1‐trifluoroalk‐3‐en‐2‐ones [CF₃C(O)CH═C(R)OR¹, where R = H, Me, Ph, 4‐FPh, 4‐BrPh, 4‐MePh, and R¹ = Me, Et] with 2,6‐diaminotoluene (2,6‐DAT) in methanol under mild conditions, in 46–70% yields. Another synthetic route also allowed the regioselective synthesis of 2‐aryl(heteroaryl)‐4‐methyl‐4‐trifluoromethyl‐7‐aminoquinolines from direct cyclocondensation reactions of 4‐alkoxy‐4‐aryl(heteroaryl)‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,6‐diaminotoluene in methanol under mild conditions, in 21–36% yields.     

Synthesis and structures of bis(dithiolene)molybdenum complexes related to the active sites of the DMSO reductase enzyme family

Structural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes are sought. These sites usually contain two pterin-dithiolene cofactor ligands and one protein-based ligand. Reaction of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R = Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum-(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to [MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes [Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- affordthe trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1- (Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]- (9, 10). In contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1-(14, 15), which have not been successfully decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(mu-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(mu-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3-5, 7-10, 12-14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations. Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)     

Mixed-ligand uranyl(V) beta-diketiminate/beta-diketonate complexes: synthesis and characterization

The reaction of [UO 2(Ar 2nacnac)Cl] 2 [Ar 2nacnac = (2,6- (i)Pr 2C 6H 3)NC(Me)CHC(Me)N(2,6- (i)Pr 2C 6H 3)] with Na(RC(O)CHC(O)R) (R = Me, Ph, CF 3) in tetrahydrofuran results in the formation of UO 2(Ar 2nacnac)(RC(O)CHC(O)R) (R = Me, 1; Ph, 2; CF 3, 3), which can be isolated in moderate yields. The structures of 1 and 2 have been confirmed by X-ray crystallography, while the solution redox properties of 1- 3 have been measured by cyclic voltammetry. Complexes 1- 3 exhibit reduction features at -1.82, -1.59, and -1.39 V (vs Fc/Fc (+)), respectively, at a scan rate of 100 mV.s (-1). The decrease in the reduction potential follows the electron-withdrawing ability of each beta-diketonate ligand. Chemical reduction of 1 and 2 with Cp* 2Co in toluene yields [Cp* 2Co][UO 2(Ar 2nacnac)(RC(O)CHC(O)R)] (R = Me, 4; Ph, 5), while reduction of 3 with Cp 2Co provides [Cp 2Co][UO 2(Ar 2nacnac)(CF 3C(O)CHC(O)CF 3)] ( 6). Complexes 4- 6 have been fully characterized, while the solid-state molecular structure of 5 has also been determined. In contrast to the clean reduction that occurs with Cp* 2Co, reduction of 1 with sodium ribbon, followed by cation exchange with [NEt 4]Cl, produces [NEt 4][UO 2(Ar 2nacnac)(H 2CC(O)CH(O)CMe)] ( 7) in modest yield. This product results from the formal loss of H (*) from a methyl group of the acetylacetonate ligand. Alternately, complex 7 can be synthesized by deprotonation of 1 with NaNTMS 2 in good yield.     

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.     

Synthesis and characterisation of mixed ligand Pt(II) and Pt(IV) oxadiazoline complexes

The nitrile ligands in trans-[PtX2(PhCN)2] (X = Cl, Br, I) undergo sequential 1,3 dipolar cycloadditions with nitrones R1R2C=N+(Me)-O(-) (R1 = H, R2 = Ph; R1 = CO2Et, R2 = CH2CO2Et) to selectively form the Delta4-1,2,4-oxadiazoline complexes trans-[PtX2(PhCN) (N=C(Ph)-O-N(Me)-CR1R2)] or trans-[PtX2(N=C(Ph)-O-N(Me)-CR1R2)2] in high yields. The reactivity of the mixed ligand complexes trans-[PtX2(PhCN)(N=C(Ph)-O-N(Me)-CR1R2)] towards oxidation and ligand substitution was studied in more detail. Oxidation with Cl2 or Br2 provides the Pt(IV) species trans-[PtX2Y2(PhCN)(N=C(Ph)-O-N(Me)-CH(Ph))] (X, Y = Cl, Br). The mixed halide complex (X = Cl, Y = Br) undergoes halide scrambling in solution to form trans-[PtX(4-n)Yn(PhCN)(N=C(Ph)-O-N(Me)-CH(Ph))] as a statistical mixture. Ligand substitution in trans-[PtCl2(PhCN)(N=C(Ph)-O-N(Me)-CR1R2)] allows for selective replacement of the coordinated nitrile by nitrogen heterocycles such as pyridine, DMAP or 1-benzyl-2-methylimidazole to produce mixed ligand Pt(II) complexes of the type trans- [PtX2(heterocycle)(N=C(Ph)-O-N(Me)-CR1R2)]. All compounds were characterised by elemental analysis, mass spectrometry, IR and 1H, 13C and 195Pt NMR spectroscopy. Single-crystal X-ray structural analysis of (R,S)-trans-[PtBr2(N=C(Ph)-O-N(Me)-CH(Ph))2] and trans-[PtCl2(C5H5N)(N=C(Ph)-O-N(Me)-CH(Ph))] confirms the molecular structure and the trans configuration of the heterocycles relative to each other.     

Reactions of amides with organoaluminum compounds: factors affecting the coordination mode of aluminum amidates

Factors affecting the coordination mode of an amidato group on aluminum will be presented. The reaction of N-tert-butylalkylacetamide ((t)BuNHCR([double bond]O)) with 1.1 molar equiv of Me(3)Al in refluxing hexane affords a pentacoordinated, dimeric compound [Me(2)Al[eta(2)-(t)BuNC(R)(mu(2)-O)]](2) (3, R = p-(t)Bu-C(6)H(4); 4, R = 2,6-F,F-C(6)H(3); 5, R = Me; 6, R = CF(3); 7, R = p-F(3)C-C(6)H(4)). However, in the presence of 2.2 molar equiv of Me(3)Al, N-tert-butyl-4-tert-butylbenzamide ((t)BuNHC(p-(t)Bu-C(6)H(4))([double bond]O in refluxing hexane gives [Me(2)Al[eta(2)-(t)BuNC(p-(t)Bu-C(6)H(4))(mu(2)-O)]AlMe(3)], 8. In contrast, the reaction of R'NHCR' '([double bond]O) with 1 molar equiv of R(3)Al at room temperature produces tetracoordinated, dimeric, eight-membered ring aluminum compounds [R(2)Al[mu,eta(2)-R'NC(R' ')O]](2) (9, R = Me, R' = 2,6-(i)Pr, (i)()Pr-C(6)H(3), R' ' = Ph; 10, R = Me, R' = (i)Bu, R' ' = Ph; 11, R = Et, R' = Bn, R' ' = Ph; 12, R = Me, R' = Ph, R' ' = CF(3); 13, R = Me, R' = Bn, R' ' = CF(3)). On the other hand, 4'-chlorobenzanilide ((p-Cl-C(6)H(4))NHCPh([double bond]O)) reacts with R(3)Al to produce trimeric, twelve-membered ring aluminum compounds [R(2)Al[mu, eta(2)-(p-Cl-C(6)H(4))NC(Ph)O]](3) (14, R = Me; 15, R = Et). Furthermore, the reaction of 2'-methoxybenzanilide with 1 molar equiv of Me(3)Al in hexane yields a dinuclear aluminum complex [Me(2)Al(o-OMe-Ph)NC(Ph)(O)AlMe(3)], 16.     

PtII-mediated 1,3-dipolar cycloaddition of oxazoline N-oxides to nitriles as a key step to dihydrooxazolo-1,2,4-oxadiazoles

A novel type of heterocycle, viz., 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3,2-b][1,2,4]oxadiazoles, was generated by an intermolecular PtII-mediated 1,3-dipolar cycloaddition (1,3-DCA) between the oxazoline N-oxide C(Me)2CH2OC(R)=N+(O-) (R = Me, Et) and coordinated nitriles in the complexes trans/cis-[PtCl2(R'CN)2] [R' = Me, Et, CH2Ph, Ph, N(C5H10)]. The reaction is unknown for free RCN and oxazoline N-oxides, but under PtII-mediated conditions, it proceeds smoothly (CH2Cl2, 20-25 degrees C, 18-20 h) and gives pure complexes [PtCl2{N=C(R')ONC(R)OCH2CMe2}2] [R/R' = Me/Me, 1; Me/Et, 2; Me/CH2Ph, 3; Me/Ph, 4; Me/N(C5H10), 5; Et/Me, 6; Et/Et, 7; Et/CH2Ph, 8; Et/Ph, 9; Et/N(C5H10), 10] in 42-84% yields after column chromatography. Compounds 1-10 were characterized by elemental analyses (C, H, N), FAB+-MS, IR, and 1H and 13C{1H} NMR spectroscopies, and X-ray diffraction (for 1, 2, 5, and 9). With the exception of benzonitrile complexes, 1,3-DCA of oxazoline N-oxides to the PtII-ligated nitriles occurred diastereoselectively and afforded mixtures of enantiomers. Depending on the substituents on nitriles, asymmetric atoms in both of the formed heterocyclic ligands have the same (SS/RR) or different (SR/RS) configurations. The heterocyclic ligands were liberated from 1-4 and 6-9 by treatment with excess ethane-1,2-diamine (en) in CH2Cl2 for 1 day at 20-25 degrees C (for R' = Me, Et, CH2Ph) and at 50 degrees C (for R' = Ph) to achieve the free organic species and the well-known [Pt(en)2](Cl)2; the products were separated, and 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3,2-b][1,2,4]oxadiazoles (11-18) were characterized by ESI+-MS and 1H and 13C{1H} NMR spectroscopies.     

Cationic diiron and diruthenium μ-allenyl complexes: synthesis, X-ray structures and cyclization reactions with ethyldiazoacetate/amine affording unprecedented butenolide- and furaniminium-substituted bridging carbene ligands

The novel cationic diiron μ-allenyl complexes [Fe(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe(2)Cp(2)(CO)(4)]. The solid state structures of [4a][CF(3)SO(3)] and of the diruthenium analogues [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}][BPh(4)] (R = Me, [2a][BPh(4)]; R = Ph, [2c][BPh(4)]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Br?nsted bases result in formation of the μ-allenylidene compound [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(1)-C(α)=C(β)=C(γ)(Ph)(2)}] (5) and of the dimetallacyclopentenone [Fe(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)=C(β)(C(γ)(Me)CH(2))C(=O)}] (6), respectively. The nitrile adducts [Ru(2)Cp(2)(CO)(NCMe)(μ-CO){μ-η(1):η(2)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me(3)NO, react with N(2)CHCO(2)Et/NEt(3) at room temperature, affording the butenolide-substituted carbene complexes [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(R)(2)OC(=O)C[upper bond 1 end](H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (9) has been detected in the course of the reaction leading to 10a. The addition of N(2)CHCO(2)Et/NHEt(2) to 7a gives the 2-furaniminium-carbene [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (11). The X-ray structures of 10a, 10b and [11][BF(4)] have been determined. The reactions of 4a,b with MeCN/Me(3)NO result in prevalent decomposition to mononuclear iron species.     

2 + 3] cycloaddition of nitrones to platinum-bound organonitriles: effect of metal oxidation state and of nitrile substituent

The ligated benzonitriles in the platinum(II) complex [PtCl2(PhCN)2] undergo metal-mediated [2 + 3] cycloaddition with nitrones -ON+(R3)=C(R1)(R2) [R1/R2/R3 = H/Ph/Me, H/p-MeC6H4/Me, H/Ph/CH2Ph] to give delta 4-1,2,4-oxadiazoline complexes, [PtCl2(N=C(Ph)O-N(R3)-C(R1)(R2))2] (2a, 4a, 6a), as a 1:1 mixture of two diastereoisomers, in 60-75% yields, while [PtCl2(MeCN)2] is inactive toward the addition. However, a strong activation of acetonitrile was reached by application of the platinum(IV) complex [PtCl4(MeCN)2] and both [PtCl4(RCN)2] (R = Me, Ph) react smoothly with various nitrones to give [PtCl4(N=C(R)O-N(R3)-C(R1)(R2))2] (1b-6b). The latter were reduced to the corresponding platinum(II) complexes [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) by treatment with PhCH2NHOH, while the reverse reaction, i.e. conversion of 1a-6a to 1b-6b, was achieved by chlorination with Cl2. The diastereoisomers of [PtCl2(N=C(R)O-N(R3)-C(R1)(R2))2] (1a-6a) exhibit different kinetic labilities, and liberation of the delta 4-1,2,4-oxadiazolines by substitution with 1,2-bis(diphenylphosphino)ethane (dppe) in CDCl3 proceeds at different reaction rates to give free N=C(R)O-N(R3)-C(R1)(R2) and [PtCl2(dppe)] in almost quantitative NMR yield. All prepared compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and 1H, 13C(1H), and 195Pt (metal complexes) NMR spectroscopies; X-ray structure determination of the first (delta 4-1,2,4-oxadiazoline)Pt(II) complexes was performed for (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)Ph)2] (1a) (a = 9.3562(4), b = 9.8046(3), c = 13.1146(5) A; alpha = 76.155(2), beta = 83.421(2), gamma = 73.285(2) degrees; V = 1117.39(7) A3; triclinic, P1, Z = 2), (R,S)-meso-[PtCl2(N=C(Ph)O-N(Me)-C(H)Ph)2] (2a) (a = 8.9689(9), b = 9.1365(5), c = 10.1846(10) A; alpha = 64.328(6), beta = 72.532(4), gamma = 67.744(6) degrees; V = 686.82(11) A3; triclinic, P1, Z = 1), (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(Me)-C(H)(p-C6H4Me))2] (3a) (a = 11.6378(2), b = 19.0767(7), c = 11.5782(4) A; beta = 111.062(2) degrees; V = 2398.76(13) A3; monoclinic, P2(1)/c, Z = 4), and (S,S)/(R,R)-rac-[PtCl2(N=C(Me)O-N(CH2Ph)-C(H)Ph2] (5a) (a = 10.664(2), b = 10.879(2), c = 14.388(3) A; alpha = 73.11(3), beta = 78.30(3), gamma = 88.88(3) degrees; V = 1562.6(6) A3; triclinic, P1, Z = 2).     

Kinetic and thermodynamic aspects of the regioselective addition of bifunctional hydroxylaminooxime-type HO-nucleophiles to Pt-complexed nitriles

The coupling between coordinated propiononitriles in trans-[PtCln(EtCN)2] (n = 2, 4) and the 1,2-hydroxylaminooximes HON(H)CMe2C(R)=NOH (R = Ph 1, Me 2) proceeds smoothly in CHCl(3) at ca. 40-45 degrees C and gives trans-[PtCln{NH=C(Et)ON(H)CMe2C(R)=NOH}2] (n = 2, R = Ph 5, Me 6; n = 4, R = Ph 7, Me 8) in 80-85% isolated yields. The reaction is highly regioselective, and both spectroscopic (IR; FAB+-MS; 1D 1H, 13C{1H}, and 195Pt NMR; and 2D 1H,13C HMQC, 1H,13C HMBC, and 1H,15N HMQC NMR) and X-ray data for 6-8 suggest that the addition proceeds exclusively via the hydroxylamine moiety of the 1,2-hydroxylaminooxime species; the existence of an oxime group remote from the nucleophile was also confirmed. Heating of 6 in air leads to its conversion to the unusual nitrosoalkane complex [PtCl2{HON=C(Me)C(Me)2N=O}] (9), whereas in the case of 5, only the metal-free salt [H3NC(Me)2C(Ph)=NOH]2(NO3)Cl.H2O (10) was isolated. To compare the kinetic aspects and trends in the addition of both types of nucleophiles (oximes and hydroxylamines; for the latter, see our recent work: Inorg. Chem. 2005, 44, 2944) to coordinated nitriles, a kinetic study of the addition of HON=C(CH2Ph)2 to [Ph3PCH2Ph][PtCl5(EtCN)] (11) to give [Ph(3)PCH(2)Ph][PtCl(5){NH=C(Et)ON=C(CH2Ph)2}] (12) was performed. The calculated rate constant k2 of 3.9 x 10(-6) M(-1) s(-1) at -20 degrees C for the addition of the oxime indicates that the hydroxylamine is, by a factor 1.7 x 10(4), more reactive toward the addition to nitriles than the oxime. Results of the synthetic, kinetic, and theoretical (at the B3LYP level of theory) studies have demonstrated that the high regioselectivity of the reactions of the 1,2-hydroxylaminooximes with ligated nitriles is both kinetically and thermodynamically controlled.     

Reaction of the stable silylene Si[(NCH2But)2C6H4-1,2] with lithium amides

The thermally stable silylene Si[(NCH2But)2C6H4-1,2] 1 undergoes oxidative addition reactions with the lithium amides LiNRR'(R = SiMe3, R' = But; R = SiMe3, R' = C6H3Me2-2,6; R = R' = Me or R = R' = Pri) to afford the new lithium amides Li(THF)2[N(R)Si(SiMe3){(NCH2But)2C6H4-1,2}][R = But2 or R = C6H3Me2-2,6 (3a)] or the new tris(amino)functionalised silyllithiums Li(THF)x[Si{(NCH2But)2C6H4-1,2}NRR'][R = SiMe3, R' = C6H3Me2-2,6, x = 2 (3); R = R'= Me, x = 3 (4) or R = R' = Pri, x = 3 (5)]. Compounds 4 and 5 are stable at ambient temperature but compound 3 is thermally labile and converts into 3a upon heating. The pathway for the formation of 2 and 3 is discussed and the X-ray structures of 2-5 are presented.     

X-ray crystallographic and Mössbauer spectroscopic applications in dependence of partial quadrupole splitting, [R], on the C-Sn-C angle in seven-coordinated diorganotin(IV) complexes

The synthesis and the IR, NMR (1H, 13C, and 119Sn), and M?ssbauer spectroscopies and single-crystal X-ray diffraction studies of seven-coordinated diorganotin(IV) complexes, namely, [Ph2Sn(Hdapsc)]Cl.H2O.DMF [7; H(2)dapsc = 2,6-diacetylpyridine bis(semicarbazone)], [Me(2)Sn(H2,6Achexim)]Br.H2O [8; H(2)2,6Achexim = 2,6-diacetylpyridine bis(3-hexamethyleneiminylthiosemicarbazone)], [Me(2)Sn(dapmts)] [9; H(2)dapmts = 2,6-diacetylpyridine bis(4-methythiosemicarbazone)], and [nBu2Sn(dapmdtc)] [10; H(2)dapmdtc = 2,6-diacetylpyridine bis(S-methydithiocarbazate)], were done. The determination of the structures of [Ph(2)Sn(Hdapsc)]+, [Me2Sn(H2,6Achexim)]+ and [Me2Sn(dapmts)], [nBu2Sn(dapmdtc)] revealed the presence of monocationic and neutral complexes, respectively. The structures consist of monomeric units in which the Sn(IV) ions exhibit distorted pentagonal-bipyramidal geometries, with the X,N,N,N,X-donor (X = O, S) systems of the ligands lying in the equatorial plane and the organic groups in the apical positions. The C-Sn-C angle in the seven-coordinated diorganotin(IV) complexes was estimated using a correlation between M?ssbauer and X-ray data based on the point-charge model and using new values obtained in this work for [alkyl] = -1.00 mm s(-1) and [aryl] = -0.80 mm s(-1) for complexes containing O,N,N,N,O-pentadentate ligands and new values for [alkyl] = -0.87 mm s(-1) and [aryl] = -0.75 mm s(-1) for complexes containing S,N,N,N,S-pentadentate ligands.     

Synthesis and structures of a 3-sila-beta-diketiminatomagnesium bromide, ketenimide and triflate

The crystalline compounds [Mg(Br)(L)(thf)].0.5Et2O [L = {N(R)C(C6H3Me2-2,6)}2SiR, R = SiMe3] (1), [Mg(L){N=C=C(C(Me)=CH)2CH2}(D)2] [D = NCC6H3Me2-2,6 (2), thf (3)] and [{Mg(L)}2{mu-OSO(CF3)O-[mu}2] (4) were prepared from (a) Si(Br)(R){C(C6H3Me2-2,6)=NR}2 and Mg for (1), (b) [Mg(SiR3)2(thf)2] and 2,6-Me2C6H3CN (5 mol for (2), 3 mol for (3)), and (c) (2) + Me3SiOS(O)2CF3 for (4); a coproduct from (c) is believed to have been the trimethylsilyl ketenimide Me3SiN=C=C{C(Me)=CH}2CH2 (5).     

Chemistry of the phosphinidene oxide ligand

Reaction of [Mo2Cp2(mu-H)(mu-PHR*)(CO)4] with DBU followed by O2 gives the first anionic phosphinidene oxide complex (H-DBU)[MoCp{P(O)R*}(CO)2] (1) (DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene; R* = 2,4,6-C6H2tBu3). This anion displays three different nucleophilic sites located at the O, P, and Mo atoms, as illustrated by the reactions reported. Thus, reaction of 1 with excess HBF4.OEt2 gave the fluorophosphide complex [MoCp(PFR*)(CO)2] via the hidroxophosphide intermediate [MoCp{PR*(OH)}(CO)2]. Related alkoxyphosphide compounds [MoCp{P(OR)R*}(CO)2] (R = Me, C(O)Ph) were prepared by reaction of 1 with [Me3O]BF4 and PhC(O)Cl, respectively, whereas reaction of 1 with MeI or C3H5Br gave the P,O-bound phosphinite complexes [MoCp(kappa2-OPRR*)(CO)2] (R = Me, C3H5). Metal-based electrophiles were found to bind at either O or Mo positions. Thus, reaction of 1 with [ZrCl2Cp2] gave the phosphinidene oxide bridged [MoCp{P(OZrClCp2)R*}(CO)2], whereas reaction with SnPh3Cl gave trans-[MoCp{P(O)R*}(CO)2(SnPh3)], an heterometallic complex having an intact terminal P(O)R* ligand.     

Synthesis, structures, and reactivity of yttrium alkyl and alkynyl complexes with mixed Tp(Me2)/Cp ligands

The structurally characterized Tp(Me2)-supported rare earth metal monoalkyl complex (Tp(Me2))CpYCH(2)Ph(THF) (1) was synthesized via the salt-metathesis reaction of (Tp(Me2))CpYCl(THF) with KCH(2)Ph in THF at room temperature. Treatment of 1 with 1 equiv of PhC≡CH under the same conditions afforded the corresponding alkynyl complex (Tp(Me2))CpYC≡CPh(THF) (2). Complex 1 exhibits high activity toward carbodiimides, isocyanate, isothiocyanate, and CS(2); treatment of 1 with such substrates led to the formation of a series of the corresponding Y-C(benzyl) σ-bond insertion products (Tp(Me2))CpY[(RN)(2)CCH(2)Ph] (R = (i)Pr(3a), Cy(3b), 2,6-(i)Pr-C(6)H(3)(3c)), (Tp(Me2))CpY[SC(CH(2)Ph)NPh] (4), (Tp(Me2))CpY[OC(CH(2)Ph)NPh] (5), and (Tp(Me2))CpY(S(2)CCH(2)Ph) (6) in 40-70% isolated yields. Carbodiimides and isothiocyanate can also insert into the Y-C(alkynyl) σ bond of 2 to yield complexes (Tp(Me2))CpY[(RN)(2)CC≡CPh] (R = (i)Pr(7a), Cy(7b)) and (Tp(Me2))CpY[SC(C≡CPh)NPh] (9). Further investigation results indicated that 1 can effectively catalyze the cross-coupling reactions of phenylacetylene with carbodiimides. However, treatment of o-allylaniline with a catalytic amount of 1 gave only the benzyl abstraction product (Tp(Me2))CpY(NHC(6)H(4)CH(2)CH═CH(2)-o)(THF) (10), without observation of the expected organic hydroamination/cyclization product. All of these new complexes were characterized by elemental analysis and spectroscopic properties, and their solid-state structures were also confirmed by single-crystal X-ray diffraction analysis.     

Amidoximes provide facile platinum(II)-mediated oxime-nitrile coupling

The nucleophilic addition of amidoximes R'C(NH(2))═NOH [R' = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) complexes trans-[PtCl(2)(RCN)(2)] [R = Et (1t.Et), Ph (1t.Ph), NMe(2) (1t.NMe(2))] and cis-[PtCl(2)(RCN)(2)] [R = Et (1c.Et), Ph (1c.Ph), NMe(2) (1c.NMe(2))] proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN){HN═C(R)ONC(R')NH(2)}]Cl [R = NMe(2); R' = Me ([3a]Cl), Ph ([3b]Cl)], cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}] [R = NMe(2); R' = Me (4a), Ph (4b)], and trans/cis-[PtCl(2)(RCN){HN═C(R)ONC(R')NH(2)}] [R = Et; R' = Me (5a, 6a), Ph (5b, 6b); R = Ph; R' = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition species trans/cis-[Pt{HN═C(R)ONC(R')NH(2)}(2)]Cl(2) [R = NMe(2); R' = Me ([7a]Cl(2), [8a]Cl(2)), Ph ([7b]Cl(2), [8b]Cl(2))] and trans/cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}(2)] [R = Et; R' = Me (10a), Ph (9b, 10b); R = Ph; R' = Me (9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b-5d, and 6a-6d leads to [7a]Cl(2), [7b]Cl(2), 9b-9d, and 10a-10d. Open-chain bisaddition species 9b-9d and 10a-10d were transformed to corresponding chelated bisaddition complexes [7d](2+)-[7f](2+) and [8c](2+)-[8f](2+) by the addition of 2 equiv AgNO(3). All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes were characterized by elemental analyses, high-resolution ESI-MS, IR, and (1)H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)(2), [7d](SO(3)CF(3))(2), [8b](Cl)(2), [8f](NO(3))(2), 9b, and 10b were also characterized by single-crystal X-ray diffraction.     

Primary and secondary phosphine complexes of iron porphyrins and ruthenium phthalocyanine: synthesis, structure, and P-H bond functionalization

Reduction of [Fe(III)(Por)Cl] (Por = porphyrinato dianion) with Na2S2O4 followed by reaction with excess PH2Ph, PH2Ad, or PHPh2 afforded [Fe(II)(F20-TPP)(PH2Ph)2] (1a), [Fe(II)(F20-TPP)(PH2Ad)2] (1b), [Fe(II)(F20-TPP)(PHPh2)2] (2a), and [Fe(II)(2,6-Cl2TPP)(PHPh2)2] (2b). Reaction of [Ru(II)(Pc)(DMSO)2] (Pc = phthalocyaninato dianion) with PH2Ph or PHPh2 gave [Ru(II)(Pc)(PH2Ph)2] (3a) and [Ru(II)(Pc)(PHPh2)2] (4). [Ru(II)(Pc)(PH2Ad)2] (3b) and [Ru(II)(Pc)(PH2Bu(t))2] (3c) were isolated by treating a mixture of [Ru(II)(Pc)(DMSO)2] and O=PCl2Ad or PCl2Bu(t) with LiAlH4. Hydrophosphination of CH2=CHR (R = CO2Et, CN) with [Ru(II)(F20-TPP)(PH2Ph)2] or [Ru(II)(F20-TPP)(PHPh2)2] in the presence of (t)BuOK led to the isolation of [Ru(II)(F20-TPP)(P(CH2CH2R)2Ph)2] (R = CO2Et, 5a; CN, 5b) and [Ru(II)(F20-TPP)(P(CH2CH2R)Ph2)2] (R = CO2Et, 6a; CN, 6b). Similar reaction of 3a with CH2=CHCN or MeI gave [Ru(II)(Pc)(P(CH2CH2CN)2Ph)2] (7) or [Ru(II)(Pc)(PMe2Ph)2] (8). The reactions of 4 with CH2=CHR (R = CO2Et, CN, C(O)Me, P(O)(OEt)2, S(O)2Ph), CH2=C(Me)CO2Me, CH(CO2Me)=CHCO2Me, MeI, BnCl, and RBr (R = (n)Bu, CH2=CHCH2, MeC[triple bond]CCH2, HC[triple bond]CCH2) in the presence of (t)BuOK afforded [Ru(II)(Pc)(P(CH2CH2R)Ph2)2] (R = CO2Et, 9a; CN, 9b; C(O)Me, 9c; P(O)(OEt)2, 9d; S(O)2Ph, 9e), [Ru(II)(Pc)(P(CH2CH(Me)CO2Me)Ph2)2] (9f), [Ru(II)(Pc)(P(CH(CO2Me)CH2CO2Me)Ph2)2] (9g), and [Ru(II)(Pc)(PRPh2)2] (R = Me, 10a; Bu(n), 10b; Bn, 10c; CH2CH=CH2, 10d; CH2C[triple bond]CMe, 10e; CH=C=CH2, 10f). X-ray crystal structure determinations revealed Fe-P distances of 2.2597(9) (1a) and 2.309(2) A (2bx 2 CH2Cl2) and Ru-P distances of 2.3707(13) (3b), 2.373(2) (3c), 2.3478(11) (4), and 2.3754(10) A (5b x 2 CH2Cl2). Both the crystal structures of 3b and 4 feature intermolecular C-H...pi interactions, which link the molecules into 3D and 2D networks, respectively.