Nigel T. Lucas

Organometallic complexes for nonlinear optics. Part 27. Syntheses and optical properties of some iron, ruthenium and osmium alkynyl complexes

The syntheses of the alkynyl complexes M(4-CCC6H4NO2)(dppe)(η-C5H5) [M=Fe (1), Ru (2), Os (3)], Os(4-CCC6H4NO2)(PPh3)2(η-C5H5) (4) and Ru(4-CCC6H4NO2)(CO)2(η-C5H5) (5) are reported. Structural studies reveal a decrease in RuC(1) distance on proceeding from 5 to 2, consistent with greater back-donation of electron density to the alkynyl ligand from the more electron-rich metal center in 2. Electrochemical data show that the MII/III couple for the dicarbonyl complex 5 is at a significantly more positive potential than that of the related diphosphine complex 2, consistent with ligand variation modifying the electron richness and hence donor strength of the metal center. Time-dependent density functional calculations on model complexes M(4-CCC6H4NO2)(PH3)2(η-C5H5) (M=Fe, Ru, Os) have been employed to assign the intense low-energy optical transition in these complexes as MLCT in character, the higher energy band being phenyl–phenyl* in nature. Molecular quadratic optical nonlinearities have been measured using the hyper-Rayleigh scattering procedure at 1064 nm. β values vary as Fe≤Ru≤Os for metal variation and CO<phosphines for co-ligand variation, the latter consistent with the variation in donor strength of the metal center inferred from electrochemical and crystallographic data. The observed trend in β on metal variation follows the trend in backbonding energies calculated by DFT.

Organometallic complexes for nonlinear optics Part 19. Syntheses and molecular quadratic hyperpolarizabilities of indoanilino-alkynyl-ruthenium complexes

Abstract The terminal alkyne 4-HCCC 6 H 4 N CCHC t BuC(O)C t BuC H ( 1 ) and ruthenium complex derivatives trans -[Ru(CC-4-C 6 H 4 N CCH=C t BuC(O)C t BuC H}Cl(dppm) 2 ] ( 2 ) and [Ru{CC-4-C 6 H 4 N CCHC t BuC(O)C t BuC H}(PPh 3 ) 2 (η-C 5 H 5 )] ( 3 ) have been synthesized. An X-ray structural study of 3 reveals the expected equivalent CC bond lengths of the phenyl and alternating CC and CC bond lengths of the quinonal ring in the indoanilino–alkynyl ligand; there is a dihedral angle of 47.59° between the phenyl and quinonal rings, probably a result of ortho -hydrogen repulsion. Metal-centred oxidation potentials of 2 and 3 are similar to those of ‘extended chain’ 4-nitroaryl–alkynyl complex analogues. Irreversible quinonal ring-centred reductions occur at significantly more negative potentials than the quasi-reversible reductions in their nitro-containing analogues. Quadratic optical nonlinearities by hyper-Rayleigh scattering at 1064 nm for 2 (417×10 −30 esu) and 3 (658×10 −30 esu) are both large, but resonance enhanced. Two-level-corrected nonlinearities for these complexes (124×10 −30 , 159×10 −30 esu, respectively) are also large, despite the presence of electron-donating tert -butyl groups reducing the efficiency of the (formally) electron-accepting quinonal ring in these donor-bridge-acceptor complexes.

Organometallic complexes for nonlinear optics. Part 29. Quadratic and cubic hyperpolarizabilities of stilbenylethynyl/gold and -ruthenium complexes

Abstract The compounds ( E )-4-XCCC 6 H 4 CHCHPh [X=SiMe 3 ( 1 ), H ( 2 )], 1,3,5-{( E )-4-XC 6 H 4 CHCH} 3 C 6 H 3 [X=I ( 3 ), CCSiMe 3 ( 4 ), CCH ( 5 )], [Au{( E )-4-CCC 6 H 4 CHCHPh}(L)] [L=PPh 3 ( 6 ), PMe 3 ( 7 )], [Au(4-CCC 6 H 4 CCPh)(L)] [L=PPh 3 ( 8 ), PMe 3 ( 9 )], 1,3,5-[(Ph 3 P)Au{( E )-4-CCC 6 H 4 CHCH}] 3 C 6 H 3 ( 10 ), trans -[Ru{( E )-4-CCHC 6 H 4 CHCHPh}Cl(dppm) 2 ]PF 6 ( 11 ), trans -[Ru{( E )-4-CCC 6 H 4 CHCHPh}Cl(L 2 ) 2 ] [L 2 =dppm ( 12 ), dppe ( 13 )], [1,3,5-( trans -[(dppm) 2 ClRu{( E )-4-CCHC 6 H 4 CHCH}]) 3 C 6 H 3 ](PF 6 ) 3 ( 14 ), 1,3,5-( trans -[(L 2 ) 2 ClRu{( E )-4-CCC 6 H 4 CHCH}]) 3 C 6 H 3 [L 2 =dppm ( 15 ), dppe ( 16 )] and 1,3,5-( trans -[(dppe) 2 (PhCC)Ru{( E )-4-CCC 6 H 4 CHCH}]) 3 C 6 H 3 ( 17 ) have been prepared (and the identity of 6 confirmed by a single-crystal X-ray diffraction study), and their electrochemical (Ru complexes) and nonlinear optical (NLO) properties assessed. The ruthenium complexes display reversible ( 12 , 13 , 15 – 17 ) or nonreversible ( 11 , 14 ) processes attributable to Ru-centered oxidation, at potentials similar to those of previously-investigated monoruthenium alkynyl or vinylidene complexes. No evidence for intermetallic electronic communication in 14 – 17 is observed. Quadratic nonlinearities at 1064 and 800 nm for the octopolar stilbenyl–ruthenium complexes 14 , 15 are large for compounds without strongly accepting substituents. Cubic molecular hyperpolarizabilities at 800 nm for the organic compounds and gold complexes are low. Cubic nonlinearities ∣ γ ∣ 800 and two-photon absorption (TPA) cross-sections σ 2 for the ruthenium complexes increase on proceeding from linear analogues 12 , 13 to octopolar complexes 15 , 16 ; the latter and 17 possess some of the largest ∣ γ ∣ 800 and σ 2 values for organometallics thus far. Cubic nonlinearities Im( χ (3) )/ N for 13 , 16 , and 17 from the first application of electroabsorption (EA) spectroscopy to organometallics are also large, scaling with the number of metal atoms.

Organometallic complexes for nonlinear optics Part 20. Syntheses and molecular quadratic hyperpolarizabilities of alkynyl complexes derived from (E)-4,4-HCCC6H4N=NC6H4NO2

Abstract The syntheses of the alkyne ( E )-4,4′-HCCC 6 H 4 NNC 6 H 4 NO 2 ( 1 ) and alkynyl complexes L n M{( E )-4,4′-CCC 6 H 4 NNC 6 H 4 NO 2 } [L n M= trans -[RuCl(dppm) 2 ] ( 2 ), Ru(PPh 3 ) 2 (η-C 5 H 5 ) ( 3 ), Au(PPh 3 ) ( 4 )] are reported. A structural study of 2 reveals E stereochemistry about the azo-linkage. Electrochemical data for the ruthenium complexes reveal that the azo-linkage in complexes 2 and 3 perturbs the metal-centred oxidation potential compared to all other alkynyl complexes of similar composition. Quadratic optical nonlinearities by hyper-Rayleigh scattering (HRS) at 1064 nm are very large for 2 and 3 , but resonance-enhanced. Comparison of HRS data for 4 with those of Au{( E )-4,4′-CCC 6 H 4 XCHC 6 H 4 NO 2 }( PP h 3 ) (X=CH, N) reveals that complex 4 has a significantly larger quadratic nonlinearity than its ene- or imino-linked analogues.

Organometallic complexes for nonlinear optics ☆: Part 23. Quadratic and cubic hyperpolarizabilities of acetylide and vinylidene complexes derived from protected and free formylphenylacetylenes

The acetylenes 4-HCCC 6 H 4 R [R=CH{OC(O)Me} 2 ( 1 ), ( 2 )], ruthenium complexes [Ru(4-CCC 6 H 4 R)(PPh 3 ) 2 (η-C 5 H 5 )] [R=CH{OC(O)Me} 2 ( 3 ), CHO ( 4 )], [Ru( n -CCHC 6 H 4 R)Cl(dppm) 2 ]PF 6 [ n =4, R= ( 7 ); R=CHO, n =3 ( 11 ), 2 ( 15 )], and [Ru( n -CCC 6 H 4 R)Cl(dppm) 2 ] [ n =4, R= ( 8 ); n =3, R=CHO ( 12 )], and gold complexes [Au( n -CCC 6 H 4 R)(L)] [ n =4, R=CHO, L=PPh 3 ( 5 ), PMe 3 ( 6 ); n =4, R= , L=PPh 3 ( 9 ), PMe 3 ( 10 ); n =3, R=CHO, L=PPh 3 ( 13 ), PMe 3 ( 14 )] have been prepared, and 9 characterized by a single crystal X-ray diffraction study. Electrochemical data for the ruthenium complexes reveal reversible or quasi-reversible (alkynyl complexes) or irreversible (vinylidene complexes) processes assigned to the Ru II/III couple; the effect on E 1/2 values of the various structural modifications across 3 , 4 , 7 , 8 , 11 , 12 and 15 are discussed. The molecular quadratic and cubic optical nonlinearities of 1 – 15 have been determined by the hyper-Rayleigh scattering technique at 1064 nm and the Z -scan technique at 800 nm, respectively; β values increase on increasing the acceptor strength, proceeding from 3-acceptor-substituted to 4-acceptor-substituted arylalkynyl ligand, and an increasing phosphine donor strength, whereas γ values increase on increasing the number of phosphine aryl groups (i.e. increasing delocalization) proceeding from PMe 3 to PPh 3 -containing complex.

Mixed-metal cluster chemistry V syntheses and X-ray crystal structure of Cp2Mo2Ir2(μ3-CO)(μ-CO)5(CO)4

Abstract The mixed-metal cluster Cp 2 Mo 2 Ir 2 (CO) 10 has been synthesized by two procedures, namely reacting CpMo(CO) 3 H with IrCl(CO) 2 ( p -toluidine) under a CO atmosphere in the presence of zinc (23%), and by combining [CpMo(CO) 3 ] − with IrCl(CO) 2 ( p -toluidine) (78%). A structural study reveals that, in contrast to the analogous Cp 2 W 2 Ir 2 (CO) 10 , it is a rare example of a tetrahedral cluster with all edges bridged by CO, and that it possesses an unusual ‘semi-face-capping’ carbonyl ligand. Carbonyl bridging and hence steric crowding increase on proceeding from tungsten to molybdenum, rendering the title complex amongst the most crowded of metal clusters.

Mixed-metal cluster chemistry VII: some phosphine and alkyne chemistry of Cp2Mo2Ir2(CO)10; X-ray crystal structures of Cp2Mo2Ir2(μ-CO)3(CO)6(PMe3) and Cp2Mo2Ir2(μ4-η2-HC2Ph)(μ-CO)4(CO)4

Abstract Reactions of Cp 2 Mo 2 Ir 2 (CO) 10 ( 1 ) with stoichiometric amounts of phosphines afforded the substitution products Cp 2 Mo 2 Ir 2 (CO) 10− x L x , (L = PPh 3 , x = 1 ( 5 ), 2 ( 6 ); L=PMe 3 , 1 ( 7 ), 2 ( 8 )), in fair to excellent yields (36–78%), shown by low temperature 31 P NMR to consist of mixtures of interconverting isomers. An X-ray structural study of Cp 2 Mo 2 Ir 2 (μ-CO) 3 (CO) 6 (PMe 3 ( 7a ), one isomer of 7 , revealed that the PMe 3 ligand occupies the electronically-preferred axial site (with respect to the plane of the bridging carbonyls). Geometries of all other isomers of 5–8 have been postulated from a combination of NMR data and results from the analogous Cp 2 Mo 2 Ir 2 (CO) 10 system. Reactions of 1 with a range of alkynes afforded Cp 2 Mo 2 Ir 2 (μ 4 -η 2 -RC 2 R′)(CO) 8 (R = R′ = Ph ( 9 ), H ( 14 ); R = H, R′ - Ph ( 10 ), 4-C 6 H 4 NO 2 ( 11 ), 4,4′-C 6 H 4 C≡CC 6 H 4 NO 2 ( 12 ), CH 2 Br ( 13 )) in fair to good yields (34–80%). An X-ray structural study of 10 revealed that the alkynes have formally inserted into the Mo−Mo bond of 1 , to afford clusters with a pseudooctahedral core geometry. Qualitative analysis of reaction rates for the syntheses of 9–14 revealed the trends acetylene > terminal alkyne > internal alkyne and 4-nitrophenylacetylene > phenylacetylene, assigned to a combination of electronic and steric effects.

Organometallic Complexes for Non-Linear Optics. XXVI. Quadratic Hyperpolarizabilities of Some 4-Methoxytetrafluorophenylalkynyl Gold and Ruthenium Complexes

The complexes [Au(4-CA≡CC6F4OMe)(L)] [L = PMe3 (1), PPh3 (2)],trans-[Ru(4-C=CHC6F4OMe)Cl(dppm)2]PF6(3) and trans-[Ru(4-CA≡CC6F4OMe)Cl(dppm)2](4) have been prepared and the identity of (2) was confirmed by a structural study. Electrochemical data for (3) and (4) suggest that the 4-C6F4OMe group lies midway between Ph and 4-C6H4NO2in electron-withdrawing strength. Quadratic non-linearities at 1064 nm, determined by the hyper-Rayleigh scattering technique, increase for co-ligand variation, in the order PPh3 < PMe3, in proceeding from (2) to (1), whereas data for the vinylidene/alkynyl complexes (3) and (4) are experimentally indistinguishable. The quadratic non-linear optical data for (1) and (2) are comparable to those of their 4-nitrophenylalkynyl analogues, however, (1) and (2) are more optically transparent.

Mixed-metal cluster chemistry VI: Phosphine substitution at CpMoIr3(μ-CO)3(CO)8; X-ray crystal structure of CpMoIr3(μ-CO)3(CO)7(PPh3)

Abstract Reactions of CpMoIr3(μ-CO)3(CO)8 (1) with stoichiometric amounts of phosphines afford the substitution products CpMoIr3(μ-CO)3(CO)8−x (L)x (L = PPh3, x = 1 (2), 2 (3); L = PMe3, x = 1 (4), 2 (5), 3 (6)) in fair to good yields (23–54%); the yields of both 3 and 6 are increased on reacting 1 with excess phosphine. Products 2–5 are fluxional in solution, with the interconverting isomers resolvable at low temperatures. A structural study of one isomer of 2 reveals that the three edges of an MoIr2 face of the tetrahedral core are spanned by bridging carbonyls, and that the iridium-bound triphenyiphosphine ligates radially and the molybdenum-bound cyclopentadienyl coordinates axially with respect to this Molr2 face. Information from this crystal structure, 31P NMR data (both solution and solid-state), and results with analogous tungsten—triiridium and tetrairidium clusters have been employed to suggest coordination geometries for the isomeric derivatives.

“Very mixed”-metal carbonyl clusters

Publisher Summary The multi-metallic coordination of organic molecules at clusters facilitates substrate transformations not readily achievable at mononuclear complexes. The aggregation of metal atoms within a metal cluster core can afford molecules with a large number of accessible oxidation states which may have the potential to function as electron reservoirs. A significant number of mixed-metal clusters contain metals from the same group or adjacent groups, but far fewer mixed-metal clusters incorporating disparate metals have been reported. The presence of differing metals introduces the possibility of metallo-selectivity into ligand substitution. This selectivity should be enhanced upon accentuating the disparity between the metals. The introduction of differing metals into a cluster core also reduces the effective symmetry over that of related homo-metallic clusters, rendering coordination sites for incoming ligands inequivalent and affording the prospect of site- as well as metallo-selectivity.