How can I prepare Sn(NO3)2?
Tin nitrate can be prepared by mixing tin and nitric acid at various proportions.


$$\ce{5Sn + 12HNO3 -&gt; 5Sn(NO3)2 + N2 + 6H2O}$$



  Tin react with nitric acid to produce nitrate tin(II), nitrogen and
  water. Nitric acid - diluted solution. This reaction takes place
  slowly. Impurities: nitrogen(II) oxide (chemiday 1)



$$\ce{4Sn + 10HNO3 -&gt; 4Sn(NO3)2 + NH4NO3 + 3H2O}$$



  Tin react with nitric acid to produce nitrate tin(II), ammonium
  nitrate and water. Nitric acid - very dilute solution. This reaction
  takes place slowly.(chemiday 2)



$$\ce{3Sn + 8HNO3 -&gt; 3Sn(NO3)2 + 2NO + 4H2O}$$



  Tin react with nitric acid to produce nitrate tin (II), oxide nitrogen
  (II) and water. Nitric acid - diluted solution.(chemiday 3)


A brief information on tin nitrate can be found here*


  Stannous Nitrate is obtained in white leaflets having the
  composition $\ce{Sn(NO3)2.20H2O}$ by cooling to -20° C. a solution of
  stannous oxide in nitric acid of density 1.2. It is also formed by the
  action of highly diluted nitric acid on the metal, some of the acid
  thus suffering maximum reduction to ammonia: 
  
  $$\ce{4Sn + 10HNO3 -&gt; 4Sn(NO3)2 + NH4NO3 + 3H2O}$$
  
  According to C. H. H. Walker, tin dissolves in nitric acid forming
  stannous and stannic nitrates, the relative proportion of these two
  salts produced depending on the temperature and the strength of the
  acid; moreover, the yellowish white precipitate which separates when
  the somewhat concentrated acid is employed is said to be a hydrated,
  ill-defined, stannic nitrate.


*http://tin.atomistry.com/stannous_nitrate.html