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Reaction of 4,5-bis(2,4,6-triisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene (H2XN2) with [Zr(NMe2)4], followed by crystallization from O(SiMe3)2, yielded [(XN2)Zr(NMe2)2]·{O(SiMe3)2}0.5 (1·{O(SiMe3)2}0.5). The zirconium dimethyl complex [(XN2)ZrMe2] (2) was subsequently accessed (a) by treatment of 1·(O(SiMe3)2)0.5 with excess AlMe3 or (b) via reaction of 1·(O(SiMe3)2)0.5 with excess Me3SiCl, affording [(XN2)ZrCl2] (3) followed by reaction of 3 with 2 equiv of MeLi. Reaction of [(XN2)ZrMe2] (2) with one equiv of B(C6F5)3 or [CPh3][B(C6F5)4] yielded cationic [(XN2)ZrMe][MeB(C6F5)3] (4) and [(XN2)ZrMe(arene)][B(C6F5)4] {arene = η6-benzene (5a), η6-toluene (5b), or bromobenzene (5c)}, respectively. Both 4 and 5b are active for ethylene polymerization under 1 atm of ethylene at 24 and 80 °C in toluene with activities ranging from 23.5-883 kg mol-1 atm-1 h-1, yielding polymers with weight-average molecular weights (M w) of 70,800-88,100 g mol-1 and polydispersities (M w/M n) of 3.94-4.67. [ABSTRACT FROM AUTHOR]

The solid-state structures and the physical, solution magnetic, solid-state magnetic, and spectroscopic (NMR and UV/vis) properties of a range of oxygen- and nitrogen-free dialkylmanganese(II) complexes are reported, and the solution reactivity of these complexes toward H2 and ZnEt2 is described. The compounds investigated are [{Mn(μ-CH2SiMe3)2}∞] (1), [{Mn(CH2CMe3)(μ-CH2CMe3)2}2{Mn(μ-CH2CMe3)2Mn}] (2), [Mn(CH2SiMe3)2(dmpe)] (3; dmpe = 1,2-bis(dimethylphosphino)ethane), [{Mn(CH2CMe3)2(μ-dmpe)}2] (4), [{Mn(CH2SiMe3)(μ-CH2SiMe3)}2(μ-dmpe)] (5), [{Mn(CH2CMe3)(μ-CH2CMe3)}2(μ-dmpe)] (6), [{Mn(CH2SiMe3)(μ-CH2SiMe3)}2(μ-dmpm)] (7; dmpm = bis(dimethylphosphino)methane), and [{Mn(CH2CMe3)(μ-CH2CMe3)}2(μ-dmpm)] (8). Syntheses for 1-4 have previously been reported, but the solid-state structures and most properties of 2-4 had not been described. Compounds 5 and 6, with a 1:2 dmpe/Mn ratio, were prepared by reaction of 3 and 4 with base-free 1 and 2, respectively. Compounds 7 and 8 were accessed by reaction of 1 and 2 with 0.5 equiv or more of dmpm per manganese atom. An X-ray structure of 2 revealed a tetrametallic structure with two terminal and six bridging alkyl groups. In the solid state, bisphosphine-coordinated 3-8 adopted three distinct structural types: (a) monometallic [LMnR2], (b) dimetallic [R2Mn(μ-L)2MnR2], and (c) dimetallic [{RMn(μ-R)}2(μ-L)] (L = dmpe, dmpm). Compound 3 exhibited particularly desirable properties for an ALD or CVD precursor, melting at 62-63 °C, subliming at 60 °C (5 mTorr), and showing negligible decomposition after 24 h at 120 °C. Comparison of variable-temperature solution and solid-state magnetic data provided insight into the solution structures of 2-8. Solution reactions of 1-8 with H2 yielded manganese metal, demonstrating the thermodynamic feasibility of the key reaction steps required for manganese(II) dialkyl complexes to serve, in combination with H2, as precursors for metal ALD or pulsed CVD. In contrast, the solution reactions of 1-8 with ZnEt2 yielded a zinc-manganese alloy with an approximate 1:1 Zn/Mn ratio. [ABSTRACT FROM AUTHOR]

Paramagnetic metal hydride (PMH) complexes play important roles in catalytic applications and bioinorganic chemistry. 3d PMH chemistry has largely focused on Ti, Mn, Fe, and Co. Various Mn II PMHs have been proposed as intermediates in catalysis, but isolated Mn II PMHs are limited to dimeric high-spin Mn II structures with bridging hydrides. In this paper, a series of the first low-spin monomeric Mn II PMH complexes are generated by chemical oxidation of their Mn I analogues. This series is of the type trans -[MnH(L)(dmpe) 2 ] +/0 where the trans ligand L is PMe 3 , C 2 H 4 , or CO [dmpe is 1,2-bis(dimethylphosphino)ethane], and the thermal stability of the Mn II hydride complexes was found to be strongly dependent on the identity of the trans ligand. When L is PMe 3 , the complex is the first example of an isolated monomeric Mn II hydride complex. In contrast, when L is C 2 H 4 or CO, the complexes are only stable at low temperatures; upon warming to room temperature, the former decomposed to afford [Mn(dmpe) 3 ] + , accompanied by ethane and ethylene, whereas the latter eliminated H 2 , generating [Mn(MeCN)(CO)(dmpe) 2 ] + or a mixture of products including [Mn(κ 1 -PF 6 )(CO)(dmpe) 2 ], depending on the reaction conditions. All PMHs were characterized by low-temperature electron paramagnetic resonance (EPR) spectroscopy, and stable [MnH(PMe 3 )(dmpe) 2 ] + was further characterized by UV-vis and IR spectroscopy, Superconducting Quantum Interference Device magnetometry, and single-crystal X-ray diffraction. Noteworthy spectral properties are the significant EPR superhyperfine coupling to the hydride (∼85 MHz) and an increase (+33 cm -1 ) in the Mn-H IR stretch upon oxidation. Density functional theory calculations were also employed to gain insights into the acidity and bond strengths of the complexes. Mn II -H bond dissociation free energies are estimated to decrease in the series of complexes from 60 (L = PMe 3 ) to 47 kcal/mol (L = CO).