In the complex acetylbromidodicarbonylbis(triethylphosphine) iron(II), the number of Fe-C bond(s) is ___________.

Among the complex ions, [Co(NH₂-CH₂-CH₂-NH₂)₂Cl₂]⁺, [CrCl₂(C₂O₄)₂]^3$$-$$, [Fe(H₂O)₄)OH)₂]⁺, [Fe(NH₃)₂(CN)₄]^$$-$$, [Co(NH₂-CH₂-CH₂-NH₂)₂(NH₃)Cl]²⁺ and [Co(NH₃)₄(H₂O)Cl]²⁺, the number of complex ions that shows cis-trans isomerism is ______________.

Three moles of B₂H₆ are completely reacted with methanol. The number of moles of boron containing product formed is ____________.

In the following reactions, the product S is