organic radical, M is {HEAD ~ a metal} or metalloid selected from antimony, arsenic, phosphorus and {TAIL ~ boron}, and d is an integer equal to from 4 6 L inclusive 
organic radical , M is { HEAD ~ a metal } or metalloid selected from antimony , arsenic , phosphorus and { TAIL ~ boron } , and d is an integer equal to from 4 6 L inclusive
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH