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Main factors have been analyzed necessary for creation of an effi cient catalytic system for alkynes hydrophosphorylation based on nickel complexes, and a valid model system was suggested for the comparison with palladium complexes. It has been discovered for the fi rst time that the insertion of an alkyne into the metalhydrogen bond occurs with a considerably lower activation barrier than into the metal-phosphorus bond, whereas the variation in the reaction energy corresponds in both cases to an exothermic reaction. Under the optimized conditions the transformation catalyzed by nickel complexes does not require acid addition and may proceed even in the absence of a phosphine ligand.The hydroheterofunctionalization (the addition of molecules containing a bond hydrogen-heteroatom) of unsaturated organic compounds is among the leading methods of contemporary fi ne organic synthesis and underlies quite a number of industrial processes [1-3]. The creation of effi cient catalytic systems proceeding from available complexes of transition metals is the common strategy in this fi eld. Nowadays a dynamic development is observed, and in many cases a signifi cant progress is achieved for catalytic reactions involving quite a number of heteroatoms and elements (B, Si, O, N, S, Se etc.) [1][2][3][4][5][6][7].Notwithstanding the advances in this field, the situation in the investigations of addition to alkynes of molecules containing the phosphorus(V)-hydrogen bond is not clear. The products of the addition along Markownikoff rule were shown to be available in the presence of palladium and nickel catalyst as was reported by Tanaka [8-12], Han [13, 14], Montchamp [15-17], Toffano [18] and in our publications [19][20][21].The accumulated array of the experimental data does not form a general unambiguous pattern, and in some cases the results from various studies are contradictory.The following key problems can be revealed requiring keen attention and deep comprehension: (1)What is the effi cience of catalysts based on palladium and nickel complexes in the addition of the P(V)-H bond to alkynes;(2)What is the reason of the signifi cant difference in the activity of catalyst precursors containing bivalent and zero-valent metal compounds, M(II) and M(0); (3)Why the regioselectivity of addition reactions changes if all of them occur by the alkyne insertion into the metal-phosphorus bond; (4) Ambiguous results exist on the ligand and acid effect. In this report we make the fi rst attempt to understand the reason of some among these contradictions and to suggest the optimum strategy of the studies for their solution.The investigation of catalytic activity of nickel and palladium complexes was carried out on a selected model hydrophosphorylation reaction of 1-heptyne (Scheme 1). It should be stated that similar model systems involving a terminal alkyne without substituents (1-hexyne, 1-hep-

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Stable negative ions containing up to sixteen silicon atoms have been measured by mass spectromettry in RF power-modulated silane plasmas for amorphous silicon deposition. These hydrogenated silicon cluster ions reach much higher masses than the positive ions, which have no more than six silicon atoms. This supports the view that negative ions are the precursors to particulate formation in silane plasmas. The time-dependent fluxes d positive and negative ions from the plasma are shown with a 5 p s time resolution. Possible cluster reaction sequences are discussed and the effect of visible light on the negative ion signal i s commented upon.

Abstract:The nickel catalyst prepared in situ from nickel bis(acetylacetonate) [NiA C H T U N G T R E N N U N G (acac) 2 ] precursor and bis(diphenylphosphino)ethane (DPPE) ligand has shown excellent performance in the hydrophosphorylation of alkynes. Markovnikov-type regioselective addition to terminal alkynes and stereoselective addition to internal alkynes were carried out with high selectivity without an acidic co-catalyst (in contrast to the palladium/acid catalytic system). Various Hphosphonates and alkynes reacted smoothly in the developed catalytic system with up to 99% yield. The mechanisms of catalyst activation and C À P bond formation were revealed by experimental (NMR, ESI-MS, X-ray) and theoretical (density functional calculations) studies. Two different pathways of the alkyne insertion in the coordination sphere of the metal are reported for the first time.