Coordination polymers and supramolecular structures in Ag(I)triflate–dppf systems (dppf=1,1′-bis(diphenylphosphino)ferrocene)

From Coordination to Noncoordination: Syntheses and Substitution Lability Studies of Titanium Triflato Complexes

A new concept for obtaining cationic complexes with triflate counteranions from coordinating triflato ligands was developed. Various routes are leading to titanium(IV) and titanium(III) triflato complexes efficiently. The reactions of pentafulvene titanium complexes with either triflic acid or silver triflate give the corresponding titanium(IV) triflato complexes in excellent yields. Hydrolysis of the titanium(IV) bistriflato complexes leads to cationic aqua complexes via displacement of the triflato ligand, which consequently acts as a noncoordinating anion. A functionalized titanium(IV) monotriflato complex was synthesized by insertion of a nitrile into the Ti-C bond and the triflato ligand was displaced by an NHC. While the titanium(IV) complexes are mostly inert toward substrates, the donor-free titanium(III) triflato complex is a strong Lewis acid and forms various adducts with monodentate Lewis bases. The titanium(III) complex was oxidized by reaction with TEMPO, resulting in a diamagnetic titanium(IV) complex. The reaction with bidentate ligands results in cationic titanium(III) complexes due to displacement of the triflato ligand by the bidentate ligands. Treatment with acetone leads to an aldol reaction of two acetone molecules and the formation of a cationic diacetone alcohol complex.

Syntheses, Characterization, and Redox Activity of Ferrocene-Containing Titanium Complexes

The chemistry of bis(π-η5:σ-η1-pentafulvene)titanium complexes is characterized by a broad range of E-H activation and Ti-C functionalization reactions, whereas ferrocene derivatives are easily accessible and redox-active compounds. The reaction of ferrocenealdehyde and -ketones with bis(π-η5:σ-η1-pentafulvene)titanium complexes result in the formation of bimetallic complexes via insertion of the C=O double bond of the aldehyde/ketone into the Ti-Cexo bond of the pentafulvene moiety. The reaction of bis(π-η5:σ-η1-pentafulvene)titanium complexes with ferrocenyl alcohols leads to alcoholate complexes via deprotonation of the OH group by the pentafulvene ligand. Because of the one remaining pentafulvene unit, further functionalization of the complexes is possible. In this work, we proceeded with 1,1'-bifunctionalized ferrocene derivatives for intramolecular follow-up reactions. 1,1'-Ferrocenedimethanol reacts with bis(π-η5:σ-η1-pentafulvene)titanium complexes in a double O-H deprotonation reaction to yield the dialcoholate complex. 1,1'-bis(phenylphosphine)ferrocene reacts differently as the double P-H deprotonation reaction results in the formation of a P-P linked phosphine. Therefore, we studied the reactivity of 1,1'-bis(phenylphosphine)ferrocene toward Rosenthal's reagent. As Rosenthal's reagent is regarded as a masked titanocene(II) species, it undergoes redox reactions toward H-acidic substrates, forming a paramagnetic Ti(III) complex.

Silver(i) complexes with 1'-(diphenylphosphino)-1-cyanoferrocene: the art of improvisation in coordination

1'-(Diphenylphosphino)-1-cyanoferrocene () reacts with silver(i) halides at a 1 : 1 metal-to-ligand ratio to afford the heterocubane complexes [Ag(μ3-X)(-κP)]4, where X = Cl (), Br (), and I (). In addition, the reaction with AgCl with 2 equiv. of leads to chloride-bridged dimer [(μ-Cl)2{Ag(-κP)2}2] () and, presumably, also to [(μ(P,N)-){AgCl(-κP)}]2 (). While similar reactions with AgCN furnished only the insoluble coordination polymer [(-κP)2Ag(NC)Ag(CN)]n (), those with AgSCN afforded the heterocubane [Ag(-κP)(μ-SCN-S,S,N)]4 () and the thiocyanato-bridged disilver(i) complex [Ag(-κP)2(μ-SCN-S,N)]2 (), thereby resembling reactions in the AgCl- system. Attempted reactions with AgF led to ill-defined products, among which [Ag(-κP)2(μ-HF2)]2 () and [(μ-SiF6){Ag(-κP)2}2] () could be identified. The latter compound was prepared also from Ag2[SiF6] and . Reactions between and AgClO4 or Ag[BF4] afforded disilver complexes [(μ(P,N)-)Ag(ClO4-κO)]2 () and [(μ(P,N)-)Ag(BF4-κF)]2 () featuring pseudolinear Ag(i) centers that are weakly coordinated by the counter anions. A similar reaction with Ag[SbF6] followed by crystallization from ethyl acetate produced an analogous complex, albeit with coordinated solvent, [(μ(P,N)-)Ag(AcOEt-κO)]2[SbF6]2 (). Ultimately, a compound devoid of any additional ligands at the Ag(i) centers, [(μ(P,N)-)Ag]2[B(C6H3(CF3)2-3,5)4]2 (), was obtained from the reaction of with silver(i) tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. The reaction of Ag[BF4] with two equivalents of produced unique coordination polymer [Ag(-κP)(μ(P,N)-)]n[BF4]n (), the structure of which contained one of the phosphinoferrocene ligands coordinated as a P,N-chelate and the other forming a bridge to an adjacent Ag(i) center. All of these compounds were structurally characterized by single-crystal X-ray crystallography, revealing that the lengths of the bonds between silver and its anionic ligand(s) typically exceed the sum of the respective covalent radii, which is in line with the results of theoretical calculations at the density-functional theory (DFT) level, suggesting that standard covalent dative bonds are formed between silver and phosphorus (soft acid/soft base interactions) while the interactions between silver and the ligand's nitrile group (if coordinated) or the supporting anion are of predominantly electrostatic nature.

Iminophosphanes: Synthesis, Rhodium Complexes, and Ruthenium(II)-Catalyzed Hydration of Nitriles

Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both κ¹ and κ² complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 °C, 3 h) and water (100 °C, 24 h) and under solvent free conditions (180 °C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand.

One-dimensional silver(i) coordination polymers containing cyclodiphosphazane, cis-{(o-MeOC6H4O)P(µ-NtBu)}2

The 1:1 reaction between the cyclodiphosphazane cis-{(o-MeOC(6)H(4)O)P(mu-N(t)Bu)}(2) (1) and AgOTf afforded one-dimensional Ag(I) coordination polymer [Ag{mu-OTf-kappaO,kappaO}{mu-(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP,kappaP}(2)](infinity) (2) containing bridging cyclodiphosphazane and trifluoromethanesulfonate (OTf) ligands. The 2:1 reaction of and AgOTf leads to the formation of simple mononuclear complex [Ag{OTf-kappaO,kappaO}({(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP}(2))(2)] (3) in quantitative yield. Reaction of 1 with AgCN produces a strain-free zig-zag coordination polymer [({(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP,kappaP}(2))(2)Ag(NCAgCN)](infinity) (4) irrespective of reaction stoichiometry and conditions. In complexes 3 and 4 cyclodiphosphazanes coordinate to Ag(I) centers in a monodentate fashion. Single crystal structures were established for the Ag(I) polymers 2 and 4.

Self-Assembly, Structures, and Solution Dynamics of Emissive Silver Metallacycles and Helices

Reactions of 9,10-bis(diphenylphosphino)anthracene (PAnP) and AgX (X = OTf-, ClO4-, PF6-, and BF4-) led to luminescent Ag-PAnP complexes with rich structural diversity. Helical polymers [Ag(mu-PAnP)(CH3CN)X]n (X = OTf-, ClO4-, and PF6-) and discrete binuclear [Ag2(mu-PAnP)2(CH3CN)4](PF6)2, trinuclear [Ag3(mu-PAnP)3 supersetBF4](BF4)2, and tetranuclear [Ag4(mu-PAnP)4 superset(ClO4)2](ClO4)2 metallacycles were isolated from different solvents. The tri- and tetranuclear metallacycles exhibited novel puckered-ring and saddlelike structures. Variable-temperature (VT) 31P{1H}-NMR spectroscopy of the complexes was solvent dependent. The dynamics in CD3CN involve two species, but the exchange processes in CD2Cl2 are more complicated. A ring-opening polymerization was proposed for the exchange mechanism in CD3CN.