wherein {HEAD ~ the tertiary ligand} comprises a formula of {TAIL ~ X2 X3} X4 X5 X6 wherein 
wherein { HEAD ~ the tertiary ligand } comprises a formula of { TAIL ~ X2 X3 } X4 X5 X6 wherein
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH