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Et, Ph), has been developed, in which the tungsten dinitrogen fragment acts as a novel metallonitrogen ligand to the catalytically active titanium center. Alkylation of 1d (Cp′ ) C 5 Me 5 , L ) 1/2 Et 2 PCH 2 CH 2 PEt 2 ) with MeLi gave di-and trimethyl derivatives 2d and 3d, which were structurally characterized.Polymerization of olefins catalyzed by soluble, welldefined transition metal complexes has been one of the most attractive subjects in organometallic chemistry. 2 In particular, monocyclopentadienyl titanium catalysts containing amide, phosphinimide, and aryloxy ligands have extensively been studied, and some of them are now employed commercially. 3,4 On the other hand, some examples of olefin polymerization by using heterobimetallic complexes have been reported where bis(cyclopentadienyl)M (M ) Zr, Hf) moieties are connected to other transition metals such as Mo, 5a,b Fe, 5c,d,f Co, 5f Rh, 5e-h and Ni 5a via cyclopentadienyl or phosphido ligands. However, significant enhancement in catalytic activity has rarely been observed. 5c,d,g During our long-standing study on chemical nitrogen fixation by transition metal complexes, 6 we have recently synthesized the titanium-tungsten heterobimetallic bridging dinitrogen complexes 1a and 1b ( Figure 1) having a half-sandwich titanium fragment from the reaction of tungsten dinitrogen complexes [W(N 2 ) 2 (L) 4 ] (L ) PMe 2 Ph, 1/2 dppe; dppe ) Ph 2 PCH 2 CH 2 PPh 2 ) with CpTiCl 3 . 7 We have now found that the heterobimetallic complexes of this class are excellent catalyst precursors for copolymerization of ethylene and 1-hexene. Preliminary results are described here.Copolymerization of ethylene and 1-hexene was studied using the titanium-tungsten heterobimetallic dinitrogen complexes 1a-1g as catalyst precursors, in which several new complexes, 1c-1g, were synthesized from similar reactions. The constrained geometry catalyst [(t-BuNSiMe 2 C 5 Me 4 )TiCl 2 ] (CGC) 2 was chosen as a reference in the copolymerization because it also contains both cyclopentadienyl and nitrogen-based ligands on titanium. Table 1 summarizes the polymerization results in which Al(i-Bu) 3 and [Ph 3 C][B(C 6 F 5 ) 4 ] were used as cocatalysts. The heterobimetallic dinitrogen complex 1a showed a very high catalytic activity of 376 kg mmol (cat) -1 h -1 . The copolymers produced have relatively high molecular weights (M w ) 77 × 10 4 ) and unimodal molecular weight distribution (M w /M n ) 2.2), indicating that the copolymers were produced by a single active species. It should be noted that the catalytic activity of 1a was more than 3 times as high as that of CGC under the same conditions, although the 1-hexene content was one-third of that observed in CGC.Complexes 1c-1e with depe (Et 2 PCH 2 CH 2 PEt 2 ) ligands also exhibited high catalytic activity. Complex (1) Preparation and Properties of Molybdenum and Tungsten Dinitrogen Complexes. Part 72. Part 71: Arita, C.; Seino, H.; Mizobe, Y.; Hidai, M. Nabika, M.; Imai, A.; Miyashita, A.; Watanabe, T.; Johohji, H.; Oda, Y.; Hanaoka, H. ...

The catalyst systems composed of hydrotris-(pyrazolyl)borate (Tp) manganese and coactivators showed good activity for ethylene polymerization and ethylene-R-olefin lymerizations goes up to 1.6 × 10 7 g mol(cat) -1 h -1 , giving ethylene-1-butene copolymer with a narrow molecular weight distribution (M w /M n ) 1.8) and a high melting point (120°C). This system is also active toward propylene and gives isotactic polypropylene with a triad mm fraction of 0.905.Since the discovery of group 4 metallocene single-site catalysts, 1 many efforts have been made for the survey of new transition metal complex catalysts. 2 In particular, Ni-or Pd-based non-metallocene catalysts were the most spectacular breakthroughs in this field. 3 Afterward, many transition metal complex catalysts based on vanadium, 4 chromium, 5 iron and cobalt, 6 and lanthanides 7 have been reported. However, less attention has been paid to group 7 metal catalysts. 8 Mn-based catalysts would be expected to have unique features different from both early and late transition metal catalysts. H. T. Ban and co-workers have reported Mn-(acac) 3 -, Cp 2 Mn-, and Mn(salen)Cl-catalyzed ethylene polymerization when methylaluminoxane (MAO) was used as an activator. 8 In their report, they obtained linear polyethylene having a relatively narrow molecular weight distribution (M w /M n ) 2.8). Among these catalysts, Cp 2 Mn/MAO showed the highest activity of 6.3 kg mol(cat) -1 h -1 , but this level is insufficient for practical use. In this report, we demonstrated three * Corresponding authors.