Table 1. Selected bond lengths (Å) and angles (°) for 5–9.

	5	6	7	8	9
C–Calkene/yne	1.552(2)	1.58(1)	1.491(7)	1.545(3)	1.370(6)
Mg–Calkene/yne (primary)	2.137(2)	2.084(7)	2.153(3)	2.156(2)	2.104(5)
	2.142(2)	2.16(1)	—	—	2.106(5)
Mg–Calkene/yne (secondary)	3.329(2)	2.324(1)	2.401(3)	2.552(2)	—
Mg···Carene (ipso)	—	—	2.518(3)	2.572(2)	2.666(5)
Mg···Carene (ortho)	2.566(2)	—	2.721(4)	2.537(2)	2.727(5)
Mg–C–C a	76.47(9)	77.3(5)	62.1(2)	57.4(1)	103.3(3)
	101.2(1)	110.4(5)	80.2(2)	85.5(1)	112.5(3)

^aInvolving primary Mg–C interaction. Narrowest angle listed first.