State Robbery statute is a valid predicate crime of violence, as even the passive examples raised here implied the threatened use of force. Where the underlying offense is a crime of violence, the attempt is also a crime of violence.
http://www.ca2.uscourts.gov/decisions/isysquery/13eb0ff5-18df-4bbb-afe2-1d11a429c5aa/1/doc/17-952_opn.pdf#xml=http://www.ca2.uscourts.gov/decisions/isysquery/13eb0ff5-18df-4bbb-afe2-1d11a429c5aa/1/hilite/
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.