Synthesis of hydride and alkyl compounds containing the Cp*Os({eta}{sup 3}-allyl) fragment. Crystal structures of Cp*Os({eta}{sup 3}-C{sub 8}H{sub 13})Br{sub 2} and [Cp*Os({eta}{sup 3}-C{sub 4}H{sub 7})Me(H{sub 2}O)][BF{sub 4}]