A biphasic displacement of [60]fullerene from fac-(dihapto-[60]fullerene)(dihapto-1,10-phenanthroline) tricarbonyl molybdenum (0)

The Lewis bases (=L) triphenylphosphine (PPh₃) and tricyclohexyl phosphine (P(Cy)₃) displace [60]fullerene (C₆₀) from the complex fac-(η²-C₆₀)(η²-phen)Mo(CO)₃ (phen = 1,10-phenanthroline). The progress of the reactions was followed observing the decrease of the absorbance values at 440 nm and by monitoring the stretching carbonyl region from 1700 to 2100 cm⁻¹. The plots of absorbance vs. time were biexponential, indicative of a biphasic behavior, for reactions under flooding conditions where [L] ? [fac-(η²-C₆₀)(η²-phen)Mo(CO)₃]. The plot of absorbance vs. time consisted of two consecutive segments: the first segment of the plot was a decrease of absorbance with time followed by a second segment where the absorbance increased with time. The first segment of the biphasic plot was ascribed to the solvent-assisted displacement of C₆₀ from fac-(η²-C₆₀)(η²-phen)Mo(CO)₃ and the second segment to decomposition of the complex fac-(η¹-L)(η²-phen)Mo(CO)₃ produced in the first of the two consecutive reactions. The rate constant values corresponding to the first segment of the biphasic plot are independent of the chemical nature of L, the molar concentration of L, and the molar concentration of C₆₀ but dependent on the chemical nature of the solvent.     

η-Cycloheptatrienyl-molybdenum chemistry: Tertiary phosphine,alkyl, hydrido,halogeno and related derivatives

The preparation and properties of the compounds [Mo(η-C₇H₇)(dppe)Y] (Y = Cl, I, Me, H), [Mo(η-C₇H₇)(dppe)Cl]⁺A^? (A = PF₆, Br or I), {[Mo(η-C₇H₇)(dppe) Br]PF₆}, {[Mo(η-C₇H₇)(dppe)I]PF₆} and {[Mo(η-C₇H₇)(dppe)L]PF₆} (L = CO, MeCN, or dppe) are described.     

Reactivity modes of bridged bimetallic [(η5-C5H5)Fe(CO)]2-μ-dppe with electrophiles. Preparation and reactions of bimetallic hydride complexes

The complex [(η⁵-C₅H₅)Fe(CO)]₂-μ-dppe (dppe = ethane-1,2-bisdiphenylphosphide) (I) reacts with electrophiles through a η-CO and forms Lewis acid O-Adducts with alkylating reagents (giving cationic μ₂-alkoxycarbyne compounds) or with alkulaluminum compounds. Treatment of I with acid affords a stable μ₂-hydride salt (IV), [CpFe(CO)]₂(μ₂-dppe)⁺, which serves as an intermediate in the stepwise hydrogenation (reversibly) of I to a bridged bimetallic dihydride, [CpFe(CO)H]₂-μ₂-dppe. This dihydride serves as a hydride donor, regenerating IV, towards Ph₃c⁺ or CpFe(CO)₂(η²-CH₂CH₂)⁺ hydride acceptors. The necessity of the μ₂-dppe as a “mechanical linkage” in facilitating some bimetalic reactions is also established.     

Synthesis and spectra of bis(tertiaryphosphine) derivatives of cycloheptatrienyltungsten complexes

Reaction of [WI(CO)₂(η⁷-C₇H₇)] with dppm (dppm = Ph₂PCH₂PPh₂) or dppe (dppe = Ph₂PCH₂CH₂PPh₂) gives the trihaptocycloheptatrienyl complexes [WI(CO)₂(L-L)(η³-C₇H₇)] [L-L = dppm, (A₁); L-L = dppe (A₂)]. The complex A₁ reacts with NH₄PF₆ to give the unidentate biphosphine complex [W(CO)₂(dppm-P)(η⁷-C₇H₇)][PF₆] (B) which yields [W(CO)(dppm)(η⁷-C₇H₇)][PF₆] (C) on reaction with Me₃NO·2H₂O. Substitution of a carbonyl ligand in [W(CO)₃(η⁷-C₇H₇)][PF₆] with the organometallic phosphine ligand [Mo(CO)₂(dppe-P)(η⁷-C₇H₇)][PF₆] yields the heterobimetallic [{W(CO)₂(η⁷-C₇H₇)}(μ-dppe){Mo(CO)₂(η⁷-C₇H₇)}x][PF₆]₂ (D).     

Regiospecificity in the reaction of [Fe2(η-C5H5)2(CO)4-n(CNMe)n] (n  02) with mercury(II) halides

The reactions of [Fe₂(η-C₅H₅)₂(CO)₂(L)(CNMe)] (L  CO or CNME) with HgX₂ (X  Cl, Br or I) give [Fe(η-C₅H₅)(CO)₂HgX] and [Fe(η-C₅H₅)(L)-(CNMe)X] as the sole products in ca. quantitative yields; this is consistent with the previously proposed mechanism for the reactions of electrophiles with polynuclear metal carbonyl derivatives.     

Reaktionen des [η2-{P–PtBu2}Pt(PPh3)2] und [η2-{P–PtBu2}Pt(dppe)] mit Metallcarbonylen. Bildung von [η2-{(CO)5M · PPtBu2}Pt(PPh3)2] (M = Cr,W) und [η2-{(CO)5Cr · PPtBu2}Pt(dppe)]

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XVI [1] Reactions of [g²-{P–P^tBu₂}Pt(PPh₃)₂] and [g²-{P–P^tBu₂}Pt(dppe)] with Metal Carbonyls. Formation of [g²-{(CO)₅M · PP^tBu₂}Pt(PPh₃)₂] (M = Cr, W) and [g²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] [η²-{P–P^tBu₂}Pt(PPh₃)₂] 4 reacts with M(CO)₅ · THF (M = Cr, W) by adding the M(CO)₅ group to the phosphinophosphinidene ligand yielding [η²-{(CO)₅Cr · PP^tBu₂}Pt(PPh₃)₂] 1 , or [η²-{(CO)₅W · PP^tBu₂}Pt(PPh₃)₂] 2 , respectively. Similarly, [η²-{P–P^tBu₂}Pt(dppe)] 5 yields [η²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] 3 . Compounds 1 , 2 and 3 are characterized by their ¹H- and ³¹P-NMR spectra, for 2 and 3 also crystal structure determinations were performed. 2 crystallizes in the monoclinic space group P2₁/n (no. 14) with a = 1422.7(1) pm, b = 1509.3(1) pm, c = 2262.4(2) pm, β = 103.669(9)°. 3 crystallizes in the triclinic space group P1 (no. 2) with a = 1064.55(9) pm, b = 1149.9(1) pm, c = 1693.2(1) pm, α = 88.020(8)°, β = 72.524(7)°, γ = 85.850(8)°.     

Dithiocarbamate complexes of cyclopentadienylcobalt(III), [Co(η-C5H5)(L)(S2CNR2)] (L = ligand)

The reactions of [Co(η-C₅H₅)(L)I₂] with Na[S₂CNR₂] (R = alkyl or phenyl) give [Co(η-C₅H₅)(I)(S₂CNR₂)] (I) when L = CO and [Co(η-C₅H₅)(L)(S₂CNR₂)]I (II) when L is a tertiary phosphine, phosphite or stibine, or organo-isocyanide ligand. In similar reactions [Co(η-C₅H₅)(CO)(C₃F₇)I] gives [Co(η-C₅H₅)(C₃F₇)(S₂CNMe₂)] and [Mn(η-MeC₅H₄)(CO)₂(NO)]PF₆ forms [Mn(η-MeC₅H₄)(NO)(S₂CNR₂)]. The iodide ligands in I may be displaced by L, to give II, or by other ligands such as [CN]^?, [NCS]^?, H₂O or pyridine whilst SnCl₂ converts it to SnCl₂I. The iodide counter-anion in II may be replaced by others to give [BPh₄]^?, [Co(CO)₄]^? or [NO₃]^? salts. However [CN]^? acts differently and displaces (PhO)₃P from [Co(η-C₅H₅){P(OPh)₃}(S₂CNMe)]I to give [Co(η-C₅H₅)(CN)(S₂CNMe₂)] which may be alkylated reversibly by MeI and irreversibly by MeSO₃F to [Co(η-C₅H₅)(CNMe)(S₂CNMe₂)]⁺ salts. Conductivity measurements suggest that solutions of I in donor solvents are partially ionized with the formation of [Co(η-C₅H₅)(solvent)(S₂CNR₂)]⁺ I^? species. The IR and ¹H NMR spectra of the various complexes are reported. They are consistent with pseudo-octahedral “pianostool” molecular structures in which the bidentate dithiocarbamate ligands are coordinated to the metal atoms through both sulphur atoms.     

Synthesis of Cationic 2,4-Dimethylpenta-2,4-dienylruthenium Complexes. Crystal Structure of Carbonyl(η4-cyclohexa-1,3-diene)-(η5-2,4-dimethylpenta-2,4-dienyl)ruthenium Tetrafluoroborate

The complex [Ru(η⁵-C₇H₁₁)₂H]BF₄ (C₇H₁₁ = 2,4-dimethylpenta-2,4-dienyl) is highly reactive towards two- and six-electron ligands. e.g. giving with CO complex [RuCO(η⁴-C₇H₁₂)(η⁵-C₇H₁₁)]BF₄. The 2,4-dimethylpenta-1,3-diene ligand (C₇H₁₂) of the latter complex is readily displaced giving, e.g. with excess cyclohexa-1,3-diene (C₆H₈) complex [RuCO(η⁴-C₆H₈)(η⁵-C₇H₁₁)]BF₄. These reactions provide a convenient entry into monopentadienylruthenium chemistry.     

Structural characterization of the anionic halfsandwich complex [Li(TMEDA)2][Mo(η5-C5H5)(CO)3] and its reactivity towards stannanes and distannanes

The crystal structure of the molybdenum half sandwich alkali salt [Li(TMEDA)₂][Mo(η⁵-C₅H₅)(CO)₃] shows the occurrence of a separated ion pair in the solid state. Furthermore, the crystal structures of the long known organotin complexes [Mo(η⁵-C₅H₅)(SnMe₃)(CO)₃], [{Mo(η⁵-C₅H₅)(CO)₃}₂SnMe₂] and [Mo(η⁵-C₅H₅)(SnMeCl₂)(CO)₃] have been recorded. The chlorination of [Mo(η⁵-C₅H₅)(SnMe₃)(CO)₃] with SnCl₄ is presented as an improved synthetic access to [Mo(η⁵-C₅H₅)(SnMeCl₂)(CO)₃]. Finally, the reaction of Li[Mo(η⁵-C₅H₅)(CO)₃] with ^tBu₂(Cl)Sn–Sn(Cl)^tBu₂ leads to the novel molybdenum distannane complex [Mo(η⁵-C₅H₅){Sn^tBu₂-Sn(Cl)^tBu₂}(CO)₃], which is fully characterized by NMR, elemental and X-ray analysis.     

C2-Bridged sandwich and half-sandwich entities with Ti(IV) and Cr(0) centers

The intense purple colored bi- and trimetallic complexes {Ti}(CH₂SiMe₃)[CC(η⁶-C₆H₅)Cr(CO)₃] (3) ({Ti}=(η⁵-C₅H₅)₂Ti) and [Ti][CC(η⁶-C₆H₅)Cr(CO)₃]₂ (5) {[Ti]=(η⁵-C₅H₄SiMe₃)₂Ti}, in which next to a Ti(IV) center a Cr(0) atom is present, are accessible by the reaction of Li[CC(η⁶-C₆H₅)Cr(CO)₃] (2) with {Ti}(CH₂SiMe₃)Cl (1) or [Ti]Cl₂ (4) in a 1:1 or 2:1 molar ratio. The chemical and electrochemical properties of 3, 5, {Ti}(CH₂SiMe₃)(CCFc) [Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄)] and [Ti][(CC)_nMc][(CC)_mM′c] [n, m=1, 2; n=m; n≠m; Mc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); M′c=(η⁵-C₅H₅)Ru(η⁵-C₅H₄); Mc=M′c; Mc≠M′c] will be comparatively discussed.     

Heterometallische Clusterkomplexe der Typen Re2(μ-PR2)(CO)8(HgY) und ReMo(μ-PR2)(η5-C5H5)(CO)6(HgY) (R = Ph,Cy; Y = Cl,W(η5-C5H5)(CO)3)

Heterometallic Cluster Complexes of the Types Re₂(μ-PR₂)(CO)₈(HgY) and ReMo(μ-PR₂)(η⁵-C₅H₅)(CO)₆(HgY) (R = Ph, Cy; Y = Cl, W(η⁵-C₅H₅)(CO)₃) Dinuclear complexes Re₂(μ-H)(μ-PR₂)(CO)₈ and ReMo(μ-H)(μ-PR₂)(η⁵-C₅H₅)(CO)₆ (R = phenyl, cyclohexyl) were deprotonated and reacted as anions with HgCl₂ to compounds of the both types Re₂(μ-PR₂)(CO)₈HgCl) and ReMo(μ-PR₂)(η⁵-C₅H₅)(CO)₆(HgCl). The heterometallic three-membered cluster complexes correspond to an isolobal exchange of a proton against a cationic HgCl⁺ group. For one of the products ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgCl) has been shown its conversion with NaW(η⁵-C₅H₅)(CO)₃ to ReMo(μ-PCy₂)(η⁵-C₅H₅)(HgW(η⁵-C₅H₅)(CO)₃) under substitution of the chloro ligand, par example. The newly prepared compounds were characterized by means of IR, UV/VIS and ³¹P NMR data. A complete determination of the molecular structure by single crystal analyses was done in the case of Re₂(μ-PCy₂)(CO)₈(HgCl) and of ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgCl) which both are dimer because of the presence of an asymmetric dichloro bridge, and of ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgW(η⁵-C₅H₅)(CO)₃). The structural study illustrates through comparison the influence of various metal types on an interaction between centric and edge-bridged frontier orbitals in three-membered metal rings.     

Reassessment of the electronic absorption spectra of Cr(η6-C6H6)2, Cr(CO)6 and Cr(η6-C6H6)(CO)3

The UV absorption bands between approximately 330 and 200 nm have been assigned to Rydberg transitions for the d⁶ complexes Cr(η⁶-C₆H₆)₂, Cr(CO)₆ and Cr(η⁶-C₆H₆)(CO)₃     

Zur Reaktivität von Disilylphosphidokomplexen des Eisens und Rutheniums gegenüber 2,4,6-t-Bu3C6H2AsCl2. Bildung und Struktur von Arsaphosphenylkomplexen,Diphosphaarsiranen, Phosphadiarsiranen und 1,2-Diphospha-3,4-diarsetanen

On the Reactivity of Disilylphosphido Complexes of Iron and Ruthenium towards 2,4,6-t-Bu₃C₆H₂AsCl₂. Generation and Structures of Arsaphosphenyl Complexes, Diphospha-ariranes, Phosphadiarsiranes, and 1,2-Diphospha-3,4-diarsetanes The reaction of (η⁵-C₅Me₅)(CO)₂Fe? P(SiMe₃)₂ ( 1a ) with 2,4,6-t-Bu₃C₆H₂AsCl₂ (= Aryl AsCl₂) ( 6 ) leads to the formation of the heterocycles [(η⁵-C₅Me₅)(CO)₂Fe? P]₂As-Aryl ( 7a ), (η⁵-C₅Me₅)(CO)₂Fe? P(As-Aryl)₂ ( 8a ), and [(η⁵-C₅Me₅)(CO)₂Fe? P-As-Aryl]₂( 9a ). The instable arsaphosphenyl complex [(η⁵-C₅Me₅)(CO)₂Fe? P?As-Aryl] can be intercepted as its Cr(CO)₅-adduct 13a . Analogously the ring compounds (η⁵-C₅Me₅)(CO)₂Ru? P]₂(As-Aryl)( 7b ) and (η⁵-C₅Me₅)(CO)₂Ru? P(As-Aryl)₂ ( 8b ) are obtained by treatment of (η⁵-C₅Me₅)(CO)₂Ru? P(SiMe₃)₂ ( 1b ) with 6 . Here again the primarily generated arsaphosphene has to be stabilized by coordination to Cr(CO)₅ which gave E-(η⁵-C₅Me₅)(CO)₂Ru? P[Cr(CO)₅ = As-Aryl ( E-13b ) and its Z-isomer ( Z-13b ). A comparable reaction sequence furnished the phosphaarsenyl complex (η⁵-C₅Me₅)(CO)(PPh)₃Fe? P[Cr(CO)₅] = As-Aryl ( 13c ). The molecular structures of 7a and 9a were elucidated by x-ray diffraction analysis. The most interesting feature of 7a is the AsP₂-triangle, in which the As? P(2) bond length (235,0(2) pm) is slightly elongated with respect to the As? P(1) distance (231,6(1) pm). This effect is presumably due to severe steric interactions at the cis-substituted As? P(2) bond. Molecule 9a displays the picture of a bended 1,2-diphospha-3,4-diarsetane (interplanar angle 137.6°) with its substituents in the all trans-orientation. The As? P and P? P separations are normal whereas the As? As bond (249,7(4) pm) is slightly widened with respect to the calculated value for a single bond (ca 244 pm).     

Ein Beitrag zur Reaktivität von (η5-C5Me5)(CO)2FeP(SiMe3)2 gegenüber P-Chlormethylenphosphanen

On the Reactivity of (η⁵-C₅Me₅)(CO)₂FeP(SiMe₃)₂ Toward P-Chloromethylene phosphanes The reaction of (η⁵-C₅Me₅)(CO)₂FeP(SiMe₃)₂ ( 2 ) with three equivalents of Cl? P?C(SiMe₃)₂ ( 3a ) afforded the 3-methanediyl-1,3,5,6-tetraphosphabicyclo[3.1.0]hex-2-ene (η⁵-C₅Me₅)(CO)₂Fe? ( 6a ). In contrast, 2 reacts with two equivalents of Cl? P?C(Ph)SiMe₃ ( 3b ) to give the thermolabile (η⁵-C₅Me₅) · (CO)₂Fe? P[P?C(Ph)SiMe₃]₂ ( 4b ) which decomposed during the reaction with further 3b. 4 b was also obtained from (η⁵-C₅Me₅)(CO)₂Fe? P(SiMe₃)? P?C(SiMe₃)₂ ( 1a ) and two equivalents of 3b .     

(n-C5H5) (CO)2W{n3-C5H5[(n-C5H4)2Fe]} - ein neuer Fe und N enthaltender Zweikernkomplex

(η-C₅H₅)(CO)₂W[(η³-C₅H₅)(C₅H₅)₂], I, containing two tilted five-membered rings, is converted into the bridged ferrocene derivative (η-C₅H₅)(CO)₂W{(η³-C₅H₅)}[(η-C₅ H₄)₂Fe]} II by successive reaction with Na and FeCl₂.     

New C2-Chiral Bidentate Ligands Bridging the gap between donor phosphine and acceptor carbonyl ligands

Two new C₂ chiral bidentate phosphorous ligands have been prepared in enantiomerically pure form. The two phosphorous centers bear electron-withdrawing groups ((CF₃)₂CH? O, C₆F₅) and are linked by a trans-cyclopentane-1,2-diol-derived bridge. Photolysis of [Cr(η⁶-C₆H₆)(CO)₃] in the presence of these two new ligands and of two previously reported bidentate phosphites, and fluorophosphinites (L) afforded [Cr(η⁶-C₆H₆)(CO)L] complexes. IR Spectral comparison of the complexes shows the new ligands to be intermediate in their bonding properties between alkyl phosphites and CO.     

New η-allyl η-cyclopentadienylcobalt cations

[Co(R-η-C₃H₄)(η-C₅H₅)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt₃ to the iodo-complex (R  H) gives [Co(η-C₃H₅)(η-C₅H₅)(PEt₃)]⁺. The reactions of [Co(R-η-C₃H₄)(η-C₅H₅))I] (R  H or 2-Me) with AgBF₄ give solutions containing the coordinatively unsaturated species [Co(R-η-C₃H₄)(η-C₅H₅)⁺. The presence of traces of water leads to the formation of [Co(R-ηC₃H₄)-(η-C₅H₅)(H₂O)]⁺. The addition of monodentate ligands L  PEt₃ PPh₃, AsPh₃, SbPh₃, CNCH₃ and bidentate ligands LL  Ph₂PCH₂CH₂PPh₂(dppe) and o-C₆H₄(AsMe₂)₂(diars), gives, respectively mononuclear [Co(2-Me-ηC₃H₄)-(η-C₅H₅)L]⁺ and binuclear ligand-bridged [(2-Me-ηC₃H₄)(η-C₅H₅)CoLLCo(2-Me-ηC₃H₄)(η-C₅H₅))]²⁺ complexes. Crystals of [Co(2-Me-ηC₃H₄)(η-C₅H₅)-(H₂O)]⁺[BF₄]^- are monoclinic, space group P2₁/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H₂O molecule in a staggered conformation with respect to the 2-Me group.     

Synthese d'une phosphine contenant du titane(II), (η5-C5H5)[η7-C7H6P(C6H5)2]Ti,ET DEcomplexes heterobimetalliques

Reaction of chlorodiphenylphosphine with (η⁵-C₅H₅)(η⁷-C₇H₆Li)Ti gave (η⁵-C₅H₅)[η⁷-C₇H₆P(C₆H₅)₂]Ti in good yields. This novel phosphinetitanium (II) derivative displaced one carbonyl of metal carbonyl complexes [Ni(CO)₄, Fe(CO)₅ and Mo(CO)₆] to afford heterobimetallic complexes containing low valent titanium, and behaved as a poor electron-donating phosphine.     

1,2-Diphosphaferrocene als Liganden in Übergangsmetallkomplexen. Röntgenstrukturanalyse von [(η5-1,3-tBu2C5H3){η5-1,2-[Co2(CO)6]-3,4-(Me3SiO)2-5-(Me3Si)P2C3}]

1,2-Diphosphaferrocenes as Ligands in Transition Metal Complexes. X-Ray Structure Analysis of [(η⁵-1,3-tBu₂C₅H₃){η⁵-1,2-[Co₂(CO)₆]-3,4-(Me₃SiO)₂-5-(Me₃Si)P₂C₃}] Reaction of metallo-1,2-diphosphapropene (η⁵-tBuC₅H₄)(CO)₂Fe? P(SiMe₃)? P?C(SiMe₃)₂ with (Z-cyclooctene)Cr(CO)₅ afforded the pentacarbonylchromium adduct of a 1,2-diphosphaferrocene [(η⁵-tBuC₅C₅H₄){η⁵-1-[Cr(CO)₅]-3,4-(Me₃SiO)₂-5-(Me₃Si)P₂C₃}Fe] ( 1 c ). Diphosphaferrocene [(η⁵-tBuC₅H₄){η⁵-3,4-(Me₃SiO)₂-5-(Me₃Si)P₂C₃}Fe] ( 2 c ) was formed when (η⁵-tBuC₅H₄)(CO)₂FeBr was treated with (Me₃Si)₂P? P?C(SiMe₃)₂ in toluene at 60°C. Photolysis of molybdenum- and tungsten hexacarbonyl in the presence of [(η⁵-1,3-tBu₂C₅H₃){η⁵-3,4-(Me₃SiO)₂-5-(Me₃Si)P₂C₃}Fe] ( 2 b ) gave the pentacarbonylmetal adducts 8 (M = Mo) and 9 (M = W), respectively. A corresponding manganese derivative resulted from the photochemical reaction of 2 b and (MeC₅H₄)Mn(CO)₃. Treatment of 2 b with Co₂(CO)₈ yielded trinuclear [(η⁵-1,3-tBu₂C₅H₃){η⁵-1,2-[Co₂(CO)₆]-3,4-(Me₃SiO)₂-5-(Me₃Si)P₂C₃}Fe] ( 11 ). Constitution and configuration of compounds 1 c, 2 c, 8 – 11 were determined by elemental analyses and spectra (IR, ¹H-, ¹³C-, ³¹P-NMR, MS). In addition the molecular structure of 11 was established by single crystal X-ray analysis.