Volatility and high thermal stability in mid-to-late first-row transition-metal complexes containing 1,2,5-triazapentadienyl ligands.

Treatment of first-row transition-metal MCl(2) (M = Ni, Co, Fe, Mn, Cr) with 2 equiv of the potassium 1,2,5-triazapentadienyl salts K(tBuNNCHCHNR) (R = tBu, NMe(2)) afforded M(tBuNNCHCHNR)(2) in 18-73% isolated yields after sublimation. The X-ray crystal structures of these compounds show monomeric, tetrahedral molecular geometries, and magnetic moment measurements are consistent with high-spin electronic configurations. Complexes with R = tBu sublime between 155 and 175 °C at 0.05 Torr and have decomposition temperatures that range from 280 to 310 °C, whereas complexes with R = NMe(2) sublime at 105 °C at 0.05 Torr but decompose between 181 and 225 °C. This work offers new nitrogen-rich ligands that are related to widely used ß-diketiminate and 1,3,5-triazapentadienyl ligands and demonstrates new complexes with properties suitable for use in atomic-layer deposition.

Interactions between catalysts and amphiphilic structures and their implications for a protocell model.

One of the essential elements of any cell, including primitive ancestors, is a structural component that protects and confines the metabolism and genes while allowing access to essential nutrients. For the targeted protocell model, bilayers of decanoic acid, a single-chain fatty acid amphiphile, are used as the container. These bilayers interact with a ruthenium-nucleobase complex, the metabolic complex, to convert amphiphile precursors into more amphiphiles. These interactions are dependent on non-covalent bonding. The initial rate of conversion of an oily precursor molecule into fatty acid was examined as a function of these interactions. It is shown that the precursor molecule associates strongly with decanoic acid structures. This results in a high dependence of conversion rates on the interaction of the catalyst with the self-assembled structures. The observed rate logically increases when a tight interaction between catalyst complex and container exists. A strong association between the metabolic complex and the container was achieved by bonding a sufficiently long hydrocarbon tail to the complex. Surprisingly, the rate enhancement was nearly as strong when the ruthenium and nucleobase elements of the complex were each given their own hydrocarbon tail and existed as separate molecules, as when the two elements were covalently bonded to each other and the resulting molecule was given a hydrocarbon tail. These results provide insights into the possibilities and constraints of such a reaction system in relation to building the ultimate protocell.

Four-coordinate Mo(II) as (silox)2Mo(PMe3)2 and its W(IV) congener (silox)2HW(eta2-CH2PMe2)(PMe3) (silox = tBu3SiO).

The reduction of [( (t) Bu 3SiO) 2MoCl] 2 ( 2 2) provided the cyclometalated derivative, (silox) 2HMoMo(kappa-O,C-OSi (t) Bu 2CMe 2CH 2)(silox) ( 3), and alkylation of 2 2 with MeMgBr afforded [( (t) Bu 3SiO) 2MoCH 3] 2 ( 4 2). The hydrogenation of 4 2 was ineffective, but the reduction of 2 2 under H 2 generated [( (t) Bu 3SiO) 2MoH] 2 ( 5 2), and the addition of 2-butyne to 3 gave [(silox) 2Mo] 2(mu:eta (2)eta (2)-C 2Me 2) ( 6), thereby implicating the existence of [(silox) 2Mo] 2 ( 1 2). The addition of (silox)H to Mo(NMe 2) 4 led to (silox) 2Mo(NMe 2) 2 ( 7), but further elaboration of the core proved ineffective. The silanolysis of MoCl 5 afforded (silox) 2MoCl 4 ( 8) and (silox) 3MoCl 3 ( 9) as a mixture from which pure 8 could be isolated, and the addition of THF or PMe 3 resulted in derivatives of 9 as (silox) 2Cl 3MoL (L = THF, 10; PMe 3, 11). Reductions of 11 and (silox) 2WCl 4 ( 15) in the presence of excess PMe 3 provided (silox) 2Cl 2MPMe 3 (M = Mo, 12; W, 16) or (silox) 2HW(eta (2)-CH 2PMe 2)PMe 3 ( 14). While "(silox) 2W(PMe 3) 2" was unstable with respect to W(IV) as 14, a reduction of 12 led to the stable Mo(II) diphosphine, (silox) 2Mo(PMe 3) 2 ( 17). X-ray crystal structures of 10 (pseudo- O h ), 12 (square pyramidal), and 14 and 17 (distorted T d ) are reported. Calculations address the diamagnetism of 12 and 16, and the distortion of 17 and its stability to cyclometalation in contrast to 14.

Low coordinate, monomeric molybdenum and tungsten(III) complexes: structure, reactivity and calculational studies of (silox)3Mo and (silox)3ML (M = Mo, W; L = PMe3, CO; silox = (t)Bu3SiO).

Treatment of (silox)3MCl (M = Mo, 1-Cl; W, 2-Cl; silox = (t)Bu3SiO) with PMe3 and Na/Hg led to formation of monomeric, d(3) phosphine adducts, (silox)3MPMe3 (M = Mo, 1-PMe3; W, 2-PMe3) via (silox)3ClMPMe3 (M = Mo, 1-ClPMe3; W, 2-ClPMe3). Structural studies show 1-PMe3 and 2-PMe3 to be highly distorted; calculations on full chemical models corroborate experimentally determined S = 1/2 ground states and their structural features. The compounds contain a bent M-P bond that is characteristic of significant sigma/pi-mixing. PMe3 may be thermally removed from 1-PMe3 in vacuo to produce (4)A2' (silox) 3Mo (1), which was derivatized with CO, NO, and 1/4 P4 to form (silox)3Mo (1-CO), (silox)3MoNO (1-NO), and (silox)3MoP (1-P), respectively. Calculations revealed (silox)3W (2') to have an S = 1/2 ground state, which may render it too reactive to be isolated. Treatment of 2-PMe3 with CO, NO, and 1/4 P4 formed (silox)3WCO (2-CO), (silox)3WNO (2-NO), and (silox)3WP (2-P), respectively. 2-CO and 2-NO are more conveniently prepared from Na/Hg reductions of 2-Cl in the presence of CO and NO, respectively. Calculations reveal subtle effects of nd(z2)/(n+1)s mixing in differentiating the chemistry of Mo and W and in rationalizing the generation of mononuclear species.

Molybdenum and tungsten structural differences are dependent on ndz(2)/(n + 1)s mixing: comparisons of (silox)3MX/R (M = Mo, W; silox = (t)Bu3SiO).

Treatment of trans-(Et 2O) 2MoCl 4 with 2 or 3 equiv of Na(silox) (i.e., NaOSi (t) Bu 3) afforded (silox) 3MoCl 2 ( 1-Mo) or (silox) 3MoCl ( 2-Mo). Purification of 2-Mo was accomplished via addition of PMe 3 to precipitate (silox) 3ClMoPMe 3 ( 2-MoPMe 3), followed by thermolysis to remove phosphine. Use of MoCl 3(THF) 3 with various amounts of Na(silox) produced (silox) 2ClMoMoCl(silox) 2 ( 3-Mo). Alkylation of 2-Mo with MeMgBr or EtMgBr afforded (silox) 3MoR (R = Me, 2-MoMe; Et, 2-MoEt). 2-MoEt was also synthesized from C 2H 4 and (silox) 3MoH, which was prepared from 2-Mo and NaBEt 3H. Thermolysis of WCl 6 with HOSi ( t )Bu 3 afforded (silox) 2WCl 4 ( 4-W), and sequential treatment of 4-W with Na/Hg and Na(silox) provided (silox) 3WCl 2 ( 1-W, tbp, X-ray), which was alternatively prepared from trans-(Et 2S) 2WCl 4 and 3 equiv of Tl(silox). Na/Hg reduction of 1-W generated (silox) 3WCl ( 2-W). Alkylation of 2-W with MeMgBr produced (silox) 3WMe ( 2-WMe), which dehydrogenated to (silox) 3WCH ( 6-W) with Delta H (double dagger) = 14.9(9) kcal/mol and Delta S (double dagger) = -26(2) eu. Magnetism and structural studies revealed that 2-Mo and 2-MoEt have triplet ground states (GS) and distorted trigonal monopyramid (tmp) and tmp structures, respectively. In contrast, 2-W and 2-WMe possess squashed-T d (distorted square planar) structures, and the former has a singlet GS. Quantum mechanics/molecular mechanics studies of the S = 0 and S = 1 states for full models of 2-Mo, 2-MoEt, 2-W, and 2-WMe corroborate the experimental findings and are consistent with the greater nd z (2) /( n + 1)s mixing in the third-row transition-metal species being the dominant feature in determining the structural disparity between molybdenum and tungsten.

The butterfly dimer [(tBu3SiO)Cr]2(mu-OSitBu3)2 and its oxidative cleavage to (tBu3SiO)2Cr(=N-N=CPh2)2 and (tBu3SiO)2Cr=N(2,6-Ph2-C6H3).

Treatment of CrCl2(THF)2 with NaOSitBu3 afforded the butterfly dimer [(tBu3SiO)Cr]2(mu-OSitBu3)2 (1(2)), whose d(CrCr) of 2.658(31) A and magnetism were indicative of strong antiferromagnetic coupling. A Boltzmann distribution of low-energy 1A1, 3B1, 5A1, 7B1, and 9A1 states obtained from calculations on [(HO)2Cr]2(muOH)2 (1'(2)) were used to provide a reasonable fit of the mu(eff) vs T data. Cleavage of 1(2) with various L (L = 4-picoline, p-tolunitrile, tBuCN, tBuNC, Ph2CO, and PMe3) generated (tBu3SiO)2CrL2 (1-L2). The dimer was oxidatively severed by Ph2CN2 to give (tBu3SiO)2Cr(N2CPh2)2 (2) and by RN3 at 23 degrees C to afford (silox)2Cr=NR (3-R) for bulky R (adamantyl (Ad), 2,6-iPr2-C6H3, 2,4,6-Me3-C6H2 = Mes, 2,6-Ph2-C6H3) and (tBu3SiO)2Cr(=NR)2 (4-R) for smaller substituents (R = 1-Naph, 2-Anth). X-ray structural studies were conducted on 1(2), square planar 1-(OCPh2)2, pseudo-Td 2 and pseudo-trigonal 3-(2,6-Ph2-C6H3), whose S = 1 ground state was discussed on the basis of calculations of (H3SiO)2Cr=NPh (3' '-Ph).