Bis(silylaminodiarylphosphoranylsilylmethyl-C,N)-tin(II) and -lead(II) complexes and their precursors; structures of H(LL′), H(LL″), Sn(LL″)2 and Pb(LL″)2; [LL′] = [CH(SiMe3)P(Ph)2NSiMe3],

We report a series (a)-(d) of tandem reactions involving the conversion of: (a) 2CH₂(SiMe₃)P(Ph)₂NSiMe₃ [2H(LL′)] (III) into successively [Li(LL′)]₂ (1a) and [Pb(LL′)₂] (3a); (b) 1a in turn into {[Li(LL″)]₂} (2) and [Pb(LL″)₂] (4); (c) 1a successively into Sn(LL′)Cl (5) and [Sn(LL″)₂] (6); (d) (1b) into (3b). Experimental details for the preparation and characterisation (including elemental analysis and multinuclear NMR spectra in C₆D₆ and EI mass spectra) of 1a, 2, 3a, 3b, 4, 6, III (a new synthesis) and IV are provided. The X-ray structures of crystalline 4, 6, III and IV are presented; those of 1a, 2 and 3a were previously published.     

Organometallic compounds of Group 13 elements containing the ligand C(SiMe3)2(SiMe2C5H4N-2)

The lithium derivative (1) reacted with AlCl₃ or Me₂AlCl to give, respectively, the monomeric compounds (2a) and (2b). The product from reaction with commercially available GaBr₃ was the analytically pure monomeric heterocycle (3), indicating that the starting halide had been partially hydrolysed before use. The reaction between 1 and commercially available InCl₃ gave a homogenous white solid (4) with X = Cl (59%) or OH (41%). The X-ray crystal structures of 2a, 3, and 4 have been determined.     

An alkylzinc bromide and a lithium alkyldibromozincate containing tris(organosilyl)methyl groups

The lithium reagent (3) reacts with a molar equivalent of anhydrous zinc bromide to give the dimeric compound (2a), in which zinc is four-coordinate. The product from a similar reaction with Li{C(SiMe₃)₂(SiMe₂NPhMe)} is the lithium zincate [Li(THF)₂(μ-Br)₂Zn{C(SiMe₃)₂(SiMe₂NPhMe)}] (4), in which the zinc is only three-coordinate. The crystal structures of 2a and 4 have been determined.     

Exchange of boryl ligand substituents in Os[B(OEt)2]Cl(CO)(PPh3)2

Reaction between Os[B(OEt)₂]Cl(CO)(PPh₃)₂ and 1,2-ethanediol in the presence of Me₃SiCl (1 equivalent) leads to the tethered boryl complex, Cl(CO)(PPh₃)₂ (1), in which one ethoxy substituent on the boryl ligand is exchanged with one hydroxy group of the 1,2-ethanediol leaving the other OH group available to coordinate to osmium, so giving a six coordinate complex. This formulation is confirmed by crystal structure determination. The same reactants, but with 2 equivalents of Me₃SiCl, lead to the yellow, coordinatively unsaturated complex, OsCl(CO)(PPh₃)₂ (2). Complex (2) adds CO to give OsCl(CO)₂ (PPh₃)₂ (3). Crystal structure determinations of 2 and 3 reveal a very marked difference in the Os-B distances found in the five coordinate complex 2 (2.043(4) Å) and the six coordinate complex 3 (2.179(7) Å). In a reaction similar to that used for forming 2 but with 1,3-propanediol replacing 1,2-ethanediol, the product is OsCl(CO)(PPh₃)₂ (4). The crystal structure for 4 is also reported.     

Reactivity of diacetylplatinum(II) complexes: Oxidative addition of halogens and hydrogen halides

Diacetylplatinum(II) complexes [Pt(COMe)₂()] ( = bpy, 3a; 4,4′-t-Bu₂-bpy, 3b), obtained by the reaction of [Pt(COMe)₂X(H)()] with NaOH in CH₂Cl₂/H₂O, were found to undergo oxidative addition reactions with halogens (Br₂, I₂) yielding the platinum(IV) complexes (trans, OC-6-13)/(cis, OC-6-32) [Pt(COMe)₂X₂()] ( = bpy, X = Br, 4a/4b; I, 4c/4d;  = 4,4′-t-Bu₂-bpy, X = Br, 4e/4f; I, 4g/4h). The diastereoselectivity of the reactions proved to be strongly dependent on the solvent. The oxidative addition of (SCN)₂ resulted in the formation of (OC-6-13)-[Pt(COMe)₂(SCN)₂()] ( = bpy, 4i; 4,4′-t-Bu₂-bpy, 4j). In a reaction the reverse of their formation, the diacetylplatinum(II) complexes 3 underwent oxidative addition with anhydrous HX (X = Cl, Br, I), prepared in situ from Me₃SiX/H₂O, yielding diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)₂X(H)()] ( = bpy, X = Cl, 5a; Br, 5b; I, 5c;  = 4,4′-t-Bu₂-bpy, X = Cl, 5d; Br, 5e; I, 5f). Furthermore, diacetyldihaloplatinum complexes 4 were found to undergo reductive elimination reactions in boiling methanol yielding acetylplatinum(II) complexes [Pt(COMe)X()] ( = bpy, X = Br, 6b; I, 6c;  = 4,4′-t-Bu₂-bpy, X = Br, 6e; I, 6f). All complexes were characterized by microanalysis, IR and ¹H and ¹³C NMR spectroscopy. Additionally, the bis(thiocyanato) complex 4j was characterized by single-crystal X-ray diffraction analysis.     

Saturated and unsaturated nickelalactones with N-heterocyclic carbene ligands: Synthesis and structures

Monomeric and dimeric nickelalactones with N-heterocyclic carbene ligands [(py)(im^mes)Ni(CH₂CH₂COO)] (1), [(im^mes)Ni(CH₂CH₂COO)]₂ (2), [(im^t-but)Ni(C(Et)C(Et)-COO)]₂ (3), [(im^mes)Ni(C(Et)C(Et)-COO)]₂ (4), and [(im^mes)Ni(CH₂C(CH₃)C(CH₃)-CH₂-COO)] (5) (im^mes: 1,3-dimesityimidazol-2-ylidene; im^t-but: 1,3-di-t-butylimidazol-2-ylidene) were synthesized and investigated by ¹H, ¹³C NMR and IR spectroscopic measurements. The solid-state structures of 1-3 and 5 were also elucidated by X-ray diffraction analyses of single crystals. In the compounds the Ni(II) ion has square-planar geometry. The metal centers in the dimers 2 and 3 are bridged by two endocyclic oxygen donor atoms of the carboxylate groups resulting in Ni₂O₂-four-membered rings. Reaction of with 2,3-dimethylbutadiene and CO₂ resulted in an oxidative coupling of the two dienes followed by insertion of CO₂ to form the dimeric complex 6. The X-ray structure of 6 shows two substituted heptenoic acid dianions which connect the two Ni(II) centers. Each nickel atom is surrounded by a η³-allyl group, a monodentate carboxylate group and an im^mes ligand.     

Transfer of heterocyclic carbene ligands from chromium to gold, palladium and platinum

The reaction of pentacarbonyl(pyrazolin-3-ylidene)chromium complexes, (2a-c) (R = Ph (a), C₆H₄NMe₂-4 (b); (C₅H₄)FeCp (c)), with [AuCl(SMe₂)], H[AuCl₄], [PdCl₂(NCPh)₂] and [PtCl₂(NCPh)₂] gives, by transfer of the heterocyclic carbene ligand, new chloro pyrazolin-3-ylidene complexes of gold(I) and gold(III), dichloro bis(pyrazolin-3-ylidene) palladium and dichloro bis(pyrazolin-3-ylidene) platinum in high yield. The chloride ligand in (Fc = (C₅H₄)FeCp) is readily displaced by trifluoroacetate. The analogous substitution of iodide for the chloride ligands in (M = Pd, Pt) give the corresponding diiodo complexes although in a much slower reaction. In contrast, the reaction of silver trifluoroacetate with affords a binuclear Pd-Ag complex containing two pyrazolin-3-ylidene and three trifluoroacetate ligands two of whom occupy bridging positions between Pd and Ag. The reactions of the pyrazolidin-3-ylidene complex (R = C₆H₄NMe₂-4) with [AuCl(SMe₂)] and [PdCl₂(NCPh)₂] yield chloro pyrazolidin-3-ylidene gold and dichloro bis(pyrazolidin-3-ylidene) palladium complexes. The related dichloro bis(tetrahydropyrimidin-4-ylidene) palladium complex is formed in the reaction of with the palladium complex [PdCl₂(NCPh)₂]. The solid-state structures of several of these heterocyclic carbene complexes including the structure of the binuclear Pd-Ag complex are established by X-ray structure analyses.     

Rhodium(I) carbonyl complexes of mono selenium functionalized bis(diphenylphosphino)methane and bis(diphenylphosphino)amine chelating ligands and their catalytic carbonylation activity

The chelate complexes of the types (1) and (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the ν(P-Se) bands and downfield shift of the ³¹P-{¹H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation through selenium donor. 1 and 2 show terminal ν(CO) bands at 1977 and 1981 cm⁻¹, respectively, suggesting high electron density at the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans- to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH₃I to produce acyl complexes (3) and (4), respectively. The kinetics of the OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of methanol was higher than that of the well known species [Rh(CO)₂I₂]⁻ and 2 shows higher catalytic activity compared to 1.     

Synthesis and first characterization of N-alkyldiaminoresorcinols

We report the synthesis and first characterization of N-alkyldiaminoresorcinols (or 4,6-bis-dialkylaminobenzene-1,3-diols C₆H₂(NHR)₂(OH)₂) (10a, R = CH₂-2-Py; 10b, R = CH₂-3-Py; 10c, R = CH₂-4-Py) which result from one-pot stepwise reactions: (i) air-oxidation of diaminoresorcinol 3, (ii) transamination reaction leading to the corresponding functional 6π+6π quinonemonoimine zwitterions C₆H₂(NHR)₂(O)₂ (9a, R = CH₂-2-Py; 9b, R = CH₂-3-Py; 9c, R = CH₂-4-Py), (iii) reduction and re-aromatization in the presence of the corresponding primary amine bearing a pyridine moiety.     

Synthesis of heterocyclic carbene ligands via 1,2,3-diheterocyclization of allenylidene complexes with dinucleophiles

Heterocyclic carbene complexes are accessible from π-donor-substituted allenylidene complexes, [(CO)₅CrCCC(NMe₂)Ph] (1) and [(CO)₅CrCCC(O-endo-Bornyl)OEt] (4), and various dinucleophiles by 1,2,3-diheterocyclization. The reaction of 1 with 1,2-dimethylhydrazine gives the 1,2-dimethylpyrazolylidene complex (2) in high yield in addition to small amounts of the α,β-unsaturated carbene complex [(CO)₅CrC(NMe₂)-C(H)C(NMe₂)Ph] (3). The analogous reaction of 4 with 1,2-dimethylhydrazine affords the 1,2-dimethylpyrazolylidene complex (5) and, via displacement of the C_γ-bound ethoxy substituent, the hydrazinoallenylidene complex [(CO)₅CrCCC(O-endo-Bornyl){NMe-N(H)Me}] (6). Treatment of 6 with catalytic amounts of acids induces cyclization to 5. On addition of 1,1-dimethylhydrazine to 1 the zwitterionic pyrazolium-5-ylidene complex (7) is formed. The reaction of 1 with 1,2-diaminocyclohexane affords a octahydro-benzo[1,4]diazepinylidene complex (10) and, via intermolecular substitution, a binuclear bisallenylidene complex (11). Thiazepinylidene complexes (12-14), containing 7-membered N/S-heterocyclic carbene ligands, are formed highly selectively in the reaction of 1 with 2-aminoethanethiol or related cysteine derivatives by a substitution/cyclization sequence. The analogous reaction of 1 with homocysteine methylester yields a thiazocanylidene complex (15). All new heterocyclic carbene ligands are strong donors exhibiting σ-donor/π-acceptor ratios similar to those of the known imidazolylidene complexes. On photolysis of 2 and 12 in the presence of triphenylphosphine, the corresponding cis-carbene tetracarbonyl triphenylphosphine complexes (16 and 17) are formed. The solid state structure of complexes 2, 7, 14, 15, and 16 is established by X-ray structural analysis.     

Platina-β-diketones as catalysts for hydrosilylation and their reactivity towards hydrosilanes

The platina-β-diketones [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1), [PPh₄][Pt{(COMe)₂H}Cl₂] (2) and [Pt{(COMe)₂H}-(acac)] (3) were found to catalyze the hydrosilylation of alkynes (hex-1-yne, hex-2-yne, hex-3-yne) and alkenes (hex-1-ene, styrene, trimethylvinylsilane) with methyldiphenylsilane (n_silane:n_substrate:n_Pt = 3000:3000:1, T = 27 °C, in C₆D₆). The comparison with the well-established catalysts from Speier (4) and Karstedt (5) exhibited up to twice as high activities for catalyst 1 and comparable regioselectivities. To get insight into the mechanism of the hydrosilylation, Si-H oxidative addition reactions towards the dinuclear platina-β-diketone 1 have been explored. Reactions of 1 with 2-picolyl substituted hydrosilanes of the type NSiMe₂H and NSiMeHN resulted in decomposition with the formation of platinum black, only. On the other hand, the analogous reaction with the 8-quinolyl substituted silane of the type NSiMeHN was found to proceed under loss of H₂ with the formation of a diacetyl(silyl)platinum(IV) complex [Pt(COMe)₂Cl(NSiMeN-κ²N,N′,κSi)] (23). DFT calculations gave insight into the reason for this different reactivity and into the course of reaction. For comparison, the reaction of 1 with bis(2-picolyl)amine was performed resulting under proton shift in the sense of an oxidative addition reaction in the formation of the diacetyl(hydrido)platinum(IV) complex [Pt(COMe)₂Cl(NNHN-κ³N,N′,N′′)] (25). The complexes 23 and 25 were fully characterized spectroscopically (¹H, ¹³C, ¹⁹⁵Pt, ²⁹Si NMR, IR) and by single-crystal X-ray structure determinations.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

Exploring reactivity of a bis-sulfonium zirconocene-ate dimer: Synthesis of various zwitterionic phosphonium anionic zirconocene complexes

Formal [3+2] cycloaddition reactions between the bis-sulfonium zirconocene-ate dimer 1a and methylpropiolate, benzaldehyde and carbon disulfide afforded stable zwitterionic phosphonium zirconocene-ate complexes 2-4, respectively, with two orthocondensed five-membered heterocycles. X-ray crystal structure of 4 has been determined. Elemental chalcogens (S, Se, Te) gave rise also to a new variety of five-coordinate zirconium(IV) complexes (5-7) by a formal [3+1] cycloaddition reaction. In these bicyclic zirconates, sulfur is included in a five-membered ring while the second chalcogen is in a four-membered one.     

Preparation and molecular structure of a pyrazolyl-ruthenium complex, Ru{C3H2NN(SO2tol)}(dppe)Cp*

The reaction between RuCl(dppe)Cp* and Me₃SiCCC(SiMe₃)NNHTs has given the pyrazole derivative (1), which was characterised by a single-crystal X-ray structure determination. Complex 1 is probably formed by attack of the NTs group on the π-complexed desilylated alkyne, with concomitant loss of a proton.     

1,1-Insertion of substituted alkynes into the Ir-O bond of η-carboxylato iridium complexes

Alkyl-carbonyl-iridium [Ir(CH₃)(CO)(η²-O₂CR′)(PPh₃)₂]⁺ (1, R′ = CH₃, Ph, p-C₆H₄CH₃) react with alkynes (RCCH; R = Ph, p-C₆H₄CH₃) in the presence of NEt₃ to give acyl-alkynyl-iridium Ir(C(O)CH₃)(-CCR)(η²-O₂CR′)(PPh₃)₂ (4) which further react with RCCH to give alkyl-carbonyl-cis-bis(alkynyl) iridium Ir(CH₃)(CO)(CCR)₂(PPh₃)₂ (5). cis-Bis(alkenyl)iridium complexes, Ir(-CHCH₂)₂(η²-O₂CCH₃)(PPh₃)₂ (6) and (η²-O₂CCH₃)(PPh₃)₂ (7) react with substituted alkynes RCCH (R = Ph, p-C₆H₄CH₃, cyclohex-1-enyl) to give cis-bis(alkynyl) Ir(CCR)₂(η²-O₂CCH₃)(PPh₃)₂ (9) that further react with RCCH to undergo the alkyne insertion reaction into the Ir-O bond to produce iridacycles containing vinyl acetate ligands, (-CCR)₂(PPh₃)₂ (8).     

Ruthenium (II) complexes of the chelating phosphine borane H2ClB · dppm

Reaction of H₂ClB · PPh₂CH₂PPh₂ (H₂ClB · dppm) with results in displacement of all three acetonitrile ligands and the formation of (1), which has been characterised crystallographically. Reaction with carbon monoxide results in a change from η² to η¹ of the borane ligand to afford (2). Compound 1 undergoes H/D exchange under a D₂ atmosphere to afford , while 2 does not.     

Synthesis of some substituted 5,6,11,12-tetrahydro-dibenzo[a,e]cyclooctene derivatives through the intermediacy of tricarbonyl(η-arene)chromium complexes

5,6,11,12-Tetrahydrodibenzo[a,e]cyclooctene derivatives with α- and β-substituents are readily accessible from [Cr(CO)₃(5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene)] 2 via a two-step sequence, which involves addition of a nucleophile and oxidation of the intermediate anionic cyclohexadienyl complex. Nucleophiles used included LiCMe₂CN (A), LiCH₂CN (B), and (C). The results show that the primary carbanion LiCH₂CN and the S-stabilized carbanion give mixtures of α- and β-substituted products and in both cases α-isomers were major, whereas the opposite regioselectivity was obtained with the tertiary carbanion LiCMe₂CN.     

Intermolecular versus intramolecular C-H activation reaction in the thermolysis of [Ru(Me)Cp*(PMe2Ph)2] (Cp* = η-C5Me5): formation and crystallographic characterisation of [Ru(Ph)Cp*(PMe2Ph)2]

Thermolysis of the ruthenium complex [Ru(Me)Cp*(PMe₂Ph)₂] (1) (Cp* = η⁵-C₅Me₅) in benzene gives methane and [Ru(Ph)Cp*(PMe₂Ph)₂] (2), which is converted slowly to (3) through the loss of benzene. 2 was structurally characterised by single-crystal X-ray diffraction experiments. DFT calculations were performed in order to understand the behaviour of the ruthenium complex 1 towards inter- or intra-molecular C-H bond activation reactions.     

ipso-and para-Functionalization of meta-terphenyl ligands with substituted methyl groups: Unusual head-to-tail coupling of terphenyl moieties

The synthesis and characterization of several ipso-functionalized derivatives of the bulky terphenyl group are described. These include the primary alcohol Ar′CH₂OH (1), the bromo derivative Ar′CH₂Br (2), and the terphenyl formate Ar′CH₂OC(O)H (3). The alcohol 1 was obtained by treatment of LiAr′ with formaldehyde, and 1 was readily converted to the bromo derivative 2 using HBr. The reaction of 1 with formic acid afforded 3 in good yield. Attempts to form the Grignard derivative of 1, i.e., Ar′CH₂MgBr, resulted in a head-to-tail reaction of the terphenyl benzyl units to yield an unusual coupled product 4. An approach to the avoidance of this coupling involved the synthesis of the terphenyl derivatives and , bearing methyl groups in the para positions of the central aryl ring, which could be prepared in good yield, and converted to their respective lithium salts 7 and 8 without complication . The compounds were characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy (1) and X-ray crystallography (2, 4, 5 and 6).     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.