Hi Christina Zuniga,
I think this topic is touching on the point of cold emailing people.
If the person has opted out of marketing emails I would still think its appropriate (and legal - In B2B sales) for the new sales rep to contact them on a one to one basis. I would make sure the focus of the email is specific to the opportunity and doesn't contain any marketing fluff.
My company has been looking at this in great detail lately due to the opt-in laws in many different countries around Europe. If someone has never opted-in or unsubscribed from your email list they are technically saying they are not interested in receiving marketing material from you. That is completely different from a member of staff sending them an email 1:1 regarding a potential deal or opportunity. I would stick to the point of the email though and not attach reports and white papers etc... Many outbound teams do prospecting and send unsolicited emails to potential customers. As long as they are sending a personal email from their own inbox or from the CRM like Salesforce its rarely considered spam in any legal sense. The email you are describing isn't technically a cold email as your company has a relationship with the lead but its also definitely not marketing.
As an extra step to your Marketing unsubscribe in Marketo I would also have a Do Not Contact Checkbox in your CRM and make sure your sales team know how and when to use it. Sometimes a potential client might reply to a sales rep saying they are not interested and please do not contact me again. This needs to be recorded in the CRM so that a few months later a new rep doesn't inherit a list of leads and call or email them again.
Here are some articles that might help:
I hope that is answering your question.