Heat map + Numbers

First we write down the First Matrix, in which every number will be represented by a color N.B. The table contains also the Axis Legend.

  c1 = {
       {"\!\(\*SubscriptBox[\(E\), \(sol\)]\)", "Ir", "Ru", "Sn", "Ti"}, 
       {"\!\(\*SubscriptBox[\(IrO\), \(2\)]\)", 0.00, -0.14, 0.80, 0.37}, 
       {"\!\(\*SubscriptBox[\(RuO\), \(2\)]\)", -0.10, 0.00, 1.03, 0.69}, 
       {"\!\(\*SubscriptBox[\(SnO\), \(2\)]\)", 0.54, 0.43, 0.00, 0.17}, 
       {"\!\(\*SubscriptBox[\(TiO\), \(2\)]\)", -0.71, 0.63, 0.62, 0.00}
       }

Second, we write down a Second Matrix, in which the numbers will be written over the colored tables

  c2 = {
       {"0.00", -0.14, "0.80", 0.37}, 
       {"-0.10", "0.00", 1.03, 0.69}, 
       {0.54, 0.43, "0.00", 0.17}, 
       {-0.71, 0.63, 0.62, "0.00"}
       }

Then we isolate the numerical part of the first matrix

  n1 = c12 ;; All, 2 ;; All 

We

l1 = c12 ;; All, 1 (*Width of a line*)

p1 = c11, 2 ;; All (*Height of a column*)

ImageCompose[

ArrayPlot[n1, ColorFunction -> "Rainbow", 
 ColorFunctionScaling -> True, Frame -> True, 
 FrameStyle -> Opacity[0], AspectRatio -> 0.737, 
 FrameTicks -> {{Transpose[{Range[Length[l1]], l1}], None}, {None, 
    Transpose[{Range[Length[p1]], p1}]}},
 FrameTicksStyle -> 
  Directive[Opacity[1], Bold, FontSize -> 60, FontFamily -> "Times"],
  Mesh -> All, MeshStyle -> White, ImageSize -> 1000],
GraphicsGrid[c2, BaseStyle -> {"Times", 45, Bold, White}, 
 AspectRatio -> 0.75, ImageSize -> 780] , {580, 310}]