Angular 2 How to "watch" for tab changes

You could use the (selectedTabChange) event. Check Material2#tabs.

Template:

<mat-tab-group color="primary" (selectedTabChange)="onLinkClick($event)">
  ...
</mat-tab-group>

Component:

import { MatTabChangeEvent } from '@angular/material';

// ...

onLinkClick(event: MatTabChangeEvent) {
  console.log({ event });

  this.router.navigate(['contacts']); 
}