A series of metal amidoboranes LiNH(2)BH(3) (LAB), NaNH(2)BH(3) (SAB), LiNH(Me)BH(3) (LMAB), NaNH(Me)BH(3) (SMAB), KNH(Me)BH(3) (PMAB), and KNH((t)Bu)BH(3) (PBAB) were synthesized by solution phase methods, and the thermal release of H(2) in the solid state was studied. The mechanism of hydrogen release from metal amidoboranes, a metal ion assisted hydride transfer, is very different than the mechanism of hydrogen release from the parent compound ammonia borane (AB). On the basis of the observed trends in reaction rates of H > Me > (t)Bu, K > Na > Li, and the kinetic isotope effect, the mechanism of hydrogen release from MAB compounds was found to proceed through a bimolecular mechanism involving the intermediacy of a MH (M = Li, Na, or K). The non-volatile products formed from MABs are significantly different than the products formed after hydrogen release from AB. The boron containing products resulting from the release of 1 equiv of hydrogen from the metal amidoboranes were characterized by MAS (11)B NMR spectroscopy and found to contain both BH(3) and sp(2) hybridized BH groups, consistent with the general structure MN(R)=BHN(R)MBH(3).

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The hydroarylation of olefins is a valuable C À C bond forming reaction used to produce alkyl arenes.[1] Olefin hydroarylation can be catalyzed by Lewis acids, but such reactions proceed through a Friedel-Crafts type mechanism involving an intermediary carbocation. Thus, these reactions give predominantly Markovnikov products, and ortho, meta, and para selectivity is determined by the substituents on the aromatic ring. In contrast, the use of transition-metal catalysts can afford different regioselectivities acting via a mechanism of arene CÀH bond activation and olefin insertion.[1] While in the past transition-metal-catalyzed olefin hydroarylation reactions were primarily limited to activated arenes wherein a chelating functionality on the arene was available to assist and direct the C À H bond activation step, [1] recently Ir III and Ru II catalysts have demonstrated hydroarylation with unactivated arenes and olefins. [2,3] Mechanistic and computational studies on these Ir III and Ru II catalysts suggest that the hydroarylation does not proceed through a Friedel-Crafts type activation but through olefin insertion followed by oxidative hydrogen migration. In addition, selectivity for antiMarkovnikov over Markovnikov products (ca. 60:40) was observed. However, significantly higher selectivities and turnover numbers (TONs) are needed to make these processes economical, so a broadly tunable system that can be modified both sterically and electronically is likely needed.One promising metal for olefin hydroarylation is platinum. There is considerable precedent for both arene C À H bond activation and olefin insertion at Pt II ; [4,5] however, attempts at olefin hydroarylation with Pt II have been disappointing.[6] Selectivities consistent with an electrophilic Friedel-Crafts type pathway were observed using a mixed Ag-Pt catalyst system. [7] With a related Pt II catalyst, the hydroarylation of norbornene was reported, but other olefins were found to be unreactive.[8] Finally, tridentate chelation of a tris(pyrazolyl)borate ligand stabilized a potential Pt IV intermediate preventing catalytic turnover.[5] Herein, we describe the rational development of an effective Pt II system for intermolecular hydroarylation with unactivated arenes and olefins and present mechanistic evidence consistent with a pathway involving aryl-olefin insertion and C À H bond oxidative addition at Pt II . While Markovnikov products are favored, anti-Markovnikov products are observed, and the mechanistic insight gained is promising for rational design of more selective and productive Pt II catalysts for these reactions.We recently reported that thermolysis of the five-coordinate Pt IV complexes [(LX)PtMe 3 ] {LX = dtbpp [3,5-di-tertbutyl-2-(2-pyridyl)pyrrolide] (1 a) or dppp [3,5-diphenyl-2-(2-pyridyl)pyrrolide] (1 b)} at 85-100 8C in C 6 D 6 in the presence of C 2 H 4 (9-60 equivalents) led to the release of ethane and methane and formation of Pt II complexes 2 a or 2 b, which contain a cyclometalated substituted pyrrolide group and C 2 H 4 ...