I will like to divorce my wife, I have not spoken to her for 1 and a half months. If I do not speak to her for 6 months to a year, would we be considered divorced? or do I have to say the words in front of her?
You have what we can call
I found your situation to be like those ones here (ARABIC)
Allah knows better
Yes, you have to say the words in order to divorce your wife. Having intentions alone does not cause divorce. Neither separation from your wife cause the divorce. Words are important. You have to say the word 'divorce' if you're issuing the divorce. One should not send mix signals when issue divorce decree for example "I have left you". to be safe I think they do not cause the divorce. I will explain it below.
It is important to say the word, "I divorce you" to your wife in order to divorce her. The words are utterly important. For example if you jokingly say to your wife, "I divorce you", this make one divorce already. While there might be minority (a very small minority) that would say such divorce does not quality for divorce. But IMO this is a divorce.
Remember one can divorce his wife three time. They can remarry her two times (in specified time) but if they issue 3 divorces, the woman has to marry someone else, consummate the marriage and then is allowed to remarry her first husband. This was done because divorce should not be considered as joke or something that light that you can issue it every now and then.
Sunni Version of Divorce
In sunni Islam, divorce does not require witnesses. You can issue divorce decree alone with your wife. It is a valid divorce.
Shia Version of Divorce
In Shia Islam, divorce can be issues alone without any witness but it must be completed with two witnesses. They reference 65:2 that mention 'establish two just witnesses for testimony'. This verse was also related about Prophet Muhammad (PBUH) when he divorce his wife, Hafsa (daughter of 'ummar). As the narration says, Prophet (PBUH) issues one divorce and the only witness was Hafsa (RA). When this verse was revealed,the prophet took her back as two witnesses were not established in the Hafsa divorce.
Note that divorce is among the least likable action in Islam that is allowed but not banned. The prophet piece be upon him spoke high of women and "If you are displaces with your wife, if you look close, you will find a good quality". Also use this decision very carefully and in my opinion in the presence of witness and on paper as that is more appropriate by now a days standards.