ZBW CTLR EXPERIENCED OPERROR AT FL350 DURING VECTORS FOR IN-TRAIL SPACING REQUIREMENT.

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I HAD ASSIGNED A 285 DEG HDG TO ACR X AT FL350 TO COMPLY WITH THE 30 MI IN-TRAIL RESTR TO DULLES (IAD). I ACCEPTED A HDOF ON ACR Y AT FL370 PROCEEDING DIRECT ALBANY (ALB); LNDG MANCHESTER (MHT). I CLRED ACR X DIRECT SPARTA (SAX) WHEN THE REQUIRED IN-TRAIL SPACING WAS ACHIEVED. OTHER IAD TFC WAS BEING VECTORED TO COMPLY WITH THE IN-TRAIL RESTR. THE SUPVR INFORMED US THAT ACR Z WAS EXEMPT FROM THE IN-TRAIL RESTR; BUT WE WERE REQUESTED TO GIVE AS MANY MI IN-TRAIL AS POSSIBLE. THE D-SIDE WAS VERY BUSY SEEING WHERE THIS ACFT WOULD FIT IN WITH OTHER IAD TFC. THE SECTOR WAS VERY BUSY AND I HAD OTHER ACFT ON VECTORS. THE D-SIDE WAS HAVING DIFFICULTY CONTACTING ZNY TO COORDINATE PARALLEL HDGS ON 2 OTHER ACFT. THEY WANTED 1 ACFT ASSIGNED A DIFFERENT ALT AND I COMPLIED WITH THAT. I THEN CLRED ACR Y TO DSND TO FL330 TO COMPLY WITH THE RESTR ON ACFT LNDG MHT. I RECOGNIZED THAT ACR Y'S DSCNT WAS GOING TO BE CLOSE TO ACR X. I ASSIGNED ACR X A L TURN; INSTRUCTED ACR Y TO STOP DSNDING; AND ALSO ASSIGNED ACR Y A L TURN. A CONTRIBUTING FACTOR WAS THE 30 MI IN-TRAIL RESTR. THIS TFC MUST BE TAKEN OFF THEIR RTE AND VECTORED WHICH CAN CAUSE CONFLICT WITH OTHER ACFT. THIS INCREASES GREATLY THE WORKLOAD.