Reacting center atoms can not be SMARTS. Actually, they can be SMARTS expressions, but a warning is issued and the toolkit does not attempt to set atomic properties during the reaction at that node.
[N,n;+:1][H:2]>>[N,n:1].[H+1:2]
[N+1,P+2:1][H:2]>>[N,P+1:1].[H+1:2]
The following general syntax is allowed for atomic expressions within reacting centers:
[<SMILES PART>;<SMARTS PART>:<MAP>]
[+1;n,N:1][H:2]>>[+0;n,N:1].[H+1:2]
The low-precedence "AND" is used to separate SMILES from SMARTS parts of the atomic expression. This allows both SMARTS expressiveness (including recursive SMARTS) and SMILES specificity.