Angular use string as outlet name

I need to use string varible as outletname rr

this is my code:

  public redirect(): any {
    let rr = 'productModal';
    let rr2 = 'm/addProduct';
    return this.router.navigate(    
      ['link/link', {outlets: {rr: rr2}}]
    );
  }
  

 public redirect(): any {
    let rr = 'productModal';
    let rr2 = 'm/addProduct';
    return this.router.navigate(    
      ['link/link', {outlets: {[rr]: rr2}}]
    );
  }